Astronomy

Any simple experiment with an H-alpha telescope?

Any simple experiment with an H-alpha telescope?


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Is there any simple experiment that can be done with an H-alpha telescope, for example to estimate the Sun's mass, size, distance, temperature or intensity?

I give lessons about renewable energy and it would be nice to somehow integrate a telescope (PST Coronado + double stack) to the chapter about photovoltaics and solar thermal energy.

  • Right now, the only "experiment" I could come up with was to show that there's often nothing to see because of the solar minimum. But we also wouldn't see any feature if the telescope was not focused or not well calibrated.

  • With some luck, it should be possible to follow the movement of a sunspot over a few days and estimate how fast the sun is rotating, possibly at different latitudes.

  • I suppose that in order to calculate many sun characteristics, it is mandatory to know the average distance between Earth and the Sun. It seems to be relatively hard to estimate 1 AU.

Is it possible to use the telescope for any experiment and estimate an order of magnitude for any of the Sun characteristics, assuming that the distance to the Sun is approximately 150 000 000km?


If you have the right filters and equipment you can make doppler measurements of the $H_alpha$ line from the sun. Since an H-alpha telescope directly detects this you can use this to measure the doppler shift. Using this you can measure the rotation rate of the sun. This has been done before with a different telescope and the paper is here.

It should also be noted that if you don't find an adequate experiment just seeing the sun thru your telescope makes a profound impact on the viewer. One writer wrote that " I watched with a mix of awe and fear. Ever since that time, I've seen the Sun not so much as a sunny companion but as a star to be reckoned with." Reference is here. That link and this one discuss viewing the doppler effect using an H-alpha telescope.


DayStar Filters SR-127-QT H-Alpha Solar Telescope

The DayStar Filters H-Alpha SR-127 QT is a new 2020 model of its flagship dedicated Hydrogen Alpha solar telescope.

The carbon fiber telescope offers a newly developed lightweight, short tube with retractable dew shield. The new, compact design is only 29 inches long and weighs just 13lbs including mounting rings and dovetail.

A high quality 127mm doublet achromat, the telescope is optimized for Hydrogen Alpha in design, figuring and coating. The focal length is 2667m and with focal reducer EFL is 1355mm. It is available in Chromosphere, Prominence or specific bandpass in PE grade.

The SE Grade DayStar Filters SR-127-QT Solar Telescope Prominence Model is priced at $5,995US and the SE Grade Chromosphere Model is retail priced at $7,995US. Pricing of the PE Grade SR 127-QT Solar Telescope 0.2 – 0.8Å is available upon request.

Specifications of the new telescope include:

– Digital readout and precision tuning control accurate to 0.01Å in center wavelength.

– Uses 12VDC power so it can also run off batteries.

– Quantum Control software capable.

– Robust, 2-inch steeltrack and rack and pinion focuser for added strength.

– Fully integrated DayStar filtration with classic DayStar Quantum control.

– Includes mounting rings with Vixen dovetail.

– Includes zero power solar finder ‘alignment keys’.

– Ships in Pelican Storm Case.

– Telescope Length: 31.1″ with dew shield retracted

– Telescope weight: 13.6 lbs. in rings.

– Operating Temperature: 20-100° F

– Power supply: DC 12V, maximum

– AC Adapter included: 120-240VAC

– Power consumption: 1.5 watts

– Wavelength Shift range: +/-1Å

– 100% safe and fully blocked directly through the OTA

– 100% safe and fully blocked directly through white light solar finder scope

– Reaches focus using the following: 1.25″ eyepiece, 2″ eyepiece, ToUCam, Lumenera, SBIG, SLR, DSLR*, afocal, CCTV Video,

– Recommended: Tele Vue 55mm Plössl eyepiece for full disk or Tele Vue 32mm or 40mm Plössl eyepieces for higher power views with the SR-127 Solar Telescope.

You can learn more about the DayStar Filters SR-127-QT at DayStars’ website.

And to make it easier for you to get the most extensive news, articles and reviews that are only available in the magazine pages of Astronomy Technology Today, we are offering a 1 year subscription for only $6! Or, for an even better deal, we are offering 2 years for only $9. Click here to get these deals which only will be available for a very limited time. You can also check out a free sample issue here.


Any simple experiment with an H-alpha telescope? - Astronomy

Телескоп/объектив съёмки: Explore Scientific ES MN-152 Comet Hunter

Камеры для съемки: ZWO ASI 183 MM Pro (Cooled)

Монтировки: SkyWatcher EQ6-R Pro EQMOD

Гиды телескоп/объектив: SVBONY 60mm Guidescope 240mm f/4

Камеры гида: Altair GPCAM3 178M

Программы: N.I.N.A. · EQAscom EQMOD · Pixinsight · PHD2

Фильтры: SVBony H-Alpha 2" 7nm

Кадры: 83x300" (6h 55')

Накопление: 6h 55'

Сред. возраст Луны: 16.72 дней

Средн. фаза Луны: 95.73%

Разрешение: 5496x3672

Местоположения: Triebes, Zeulenroda-Triebes, Thüringen, Германия

Источник данных: Путешественник

Описание

The last nights we had clear skies after a long period of clouds. Although I had to work every early morning, I decided to use the telescope. I had to solve some last technical issues with my setup and managed to keep the scope working automatically the whole night(s). After some hints of nice users in the forum, I decided to play a bit with my exposure times. One night, I took a lot of images with an exposure time of 180 seconds. After stacking the images in DSS, I was not able to get a usable result. So I decided to go with an exposure time of 300 seconds instead. I also switched from gain 111 (unity gain on the ZWO 183MM) to 178. The results with the Ha filter were much better now. Because there was a full moon out, the contrast in a lot of the images was really poor. So again I decided to go for additional images in Ha during the third night. Yesterday, I purchased a license of PixInsight and did some experiments today.

I managed to stack 83 images of 300s each, that were captured on the 30th and 31st of march 2021. Because I was not able to shoot flats, I had to use the DBE-Tool to even out the exposure. So far, this first attempt was in my opinion really successful. Although it is just a monochrome image, I am quite happy with it. As soon as the sky is clear again, i will capture the heart of the heart nebula in SII and if the moon is not out, I also go for OIII to get a colored version.


Online Telescopes

Have you ever wondered what it would be like to look through a telescope, but don’t have one? Are you curious if there is such a thing as an online telescope? The answer is yes. If you have a computer, you can use it to virtually look through the eyepiece of a telescope… and even aim it at the objects of your choice!

One of the most exciting concepts to come about in a long time is the SLOOH Space Camera. Here’s an opportunity to look through a variety of online telescopes located around the world and take a look at space from the comfort of your home. It’s not difficult and you don’t need complicated instructions to use it. SLOOH’s patented instant-imaging technology and user-friendly interface let’s astronomers of all ages and skill levels remotely control a real telescope!All you need is a Mac or PC computer and Internet browser to explore the deepest reaches of space. To use the Slooh online telescope you must become a member of the Club, which includes mission cards, activity books, and online gift certificates. Once enrolled, you can articipate in group missions or control the online telescopes yourself. Says PC Magazine: “Would-be astronomers can gaze at live images of the night sky, but in the comfort of their homes. Kids – even big ones will marvel when they see the Andromeda Galaxy and other distant objects slowly materialize on their computer screens.”

If you’re a bit more advanced and would like to try your hand at astrophotograpy with an online telescope, then check out iTelescope.Net. iTelescope.Net also has a variety of telescopes positioned in observatories around the world, and you can view live images as they are being created by remote astrophographers. Because taking images of the sky can involve very costly equipment and years of practice, how cool would it be just to tap into an on-line telescope and begin imaging? Now it’s as easy as taking lessons and renting the equipment – and you don’t even need clear skies or a special place to go. It’s as close as your PC!

Another type of opportunity to enjoy an online telescope in a different format is the WorldWide Telescope. While this online telescope doesn’t offer “live” views, the WorldWide Telescope (WWT) will allow your computer to act as a virtual telescope by displaying images from the foremost ground and space-based telescopes. You can even take a tour of all the most incredible places in space narrated by a real astronomer! This online telescope can provide views in multiple wavelength. Imagine seeing an x-ray view of a supernova and fading into visible light! Now you can take a look with H-alpha to view star-forming regions and examine high energy radiation coming from nearby stars in the Milky Way. Are you skies clouded out? No more. With the WorldWide Telescope you can view the Moon and planets anytime, from any location on Earth and any time in the past or future!

Would you like to use an online telescope to look at our nearest star? Then take a look at Eyes On The Skies. This simple and easy to use website offers “live” views of our Sun with an online telescope. This is the home of the internet-accessible robotic solar telescope, built by Tri-Valley Stargazers member Mike Rushford. Of course, you can only control the online solar telescope if the skies are sunny in Livermore California, USA!


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All this telescope.

The weather forecast says cold, cloudy and rainy for the coming weeks, so I thought it would be a good time to dig out and dust off my oldest refractor to take inventory of the items.

And as this is the merry month of Christmas, some unboxing is surely in order. Nothing extraordinary, but besides the nice hardware, the items do hold a lot of fond memories, -- and no better time that December to share that.

#2 apfever

That looks like a dubbed Unitron add that had the suave college guy carrying the scope in box, and a cig.

#3 Kasmos

#4 AllanDystrup

Yeah well, I tried to somewhat match the atmosphere of that iconic add, though now a couple of scratches in the varnish, a few wrinkles on the forehead, some fading of the colors. but hey! in general, "still crazy after all these years. "

Edited by AllanDystrup, 04 December 2020 - 03:43 AM.

#5 Kasmos

It can be fun to try and recreate a photo.

In the same vein here's your next assignment

#6 AllanDystrup

Would love to, -- but sadly I don't have a Questar.

And I just sold my Zeiss Meniscas, -- though that would have been one heck of a challenge to balance on one hand!

Edited by AllanDystrup, 04 December 2020 - 04:12 AM.

#7 AllanDystrup

Aaaand: SimSalaBim!
.
Superiority

Edited by AllanDystrup, 04 December 2020 - 04:31 AM.

#8 starman876

Beautiful Unitron set up. Nice box for the Unihex. Looks custom made. I have seen a lot of Unitron mount boxes with that foam in them. One way of keeping the parts from shifting around. It looks like you have both the 128 mount and the Alt Az mount.

#9 Corcaroli78

It can be fun to try and recreate a photo.

In the same vein here's your next assignment

Questar Goddess.jpg

Wow. This is a very creative ad,

I must say that when i saw Allan opening post he looked quite strange, like those scandinavian psycho drama novels, but now all is clear :-)

#10 Terra Nova

I’m glad to see that you kept one Unitron Allan! And like me, you kept the iconic model 114 and lots of goodies for it.

#11 badback

#12 RichA

Smoker. Won't be buying his old Unitron.

#13 The_Vagabond

"All this telescope are yours, except Europa. Attempt no landings there. "

#14 AllanDystrup

Johann , -- yes, I made the custom box for the Unihex and the solar equipment. And yes, I have both the 114 and 128 mount heads for the 2.4" Unitron/Polarex OTA.

Terra, -- yes, I can't let go completely of my past, too many memories and emotions connected with "being at the controls of a Unitron". I hope I can make one of my grandchildren interested in using it, -- small girls now, but they'll be tweens in the wink of an eye.

Carlos, -- indeed, some Scandinavian film noir has crept into my take on the original Unitron add (it' s a pencil btw, in my hand, not a cig :-)

So, here's a couple of highlights:

The objective shows at least 1/8 wave in DPAC (green light). Much better that the "diffraction limited" resolution Nihon Seiko guaranteed. It's housed in an adjustable cell with three "ears" for easy collimation.

I have two 23.5mm diameter, 150mm focal length chromed brass viewfinders. One can use std. 0.965 eyepieces and comes with a 6x EP equivalent to a 25mm FL. It also accepts 8x equivalent to 18mm FL eyepieces. The other has smaller eyepieces and slightly smaller FOV, but features a nice double-cross which I prefer to use.

I've substituted the NS 3-armed metal octograbber with a Zeiss Telementor-like leather strap stabilizer (still have the original, of course). It is easier to collapse/expand the tripod this way, when carrying it in and out for observation. -- And the tripod of course is the adjustable height, sliding leg version, much better in use than the single height bending leg construction.

Some other Christmas sweets, which I'll present to you on a virtual tray, shortly.

Edited by AllanDystrup, 05 December 2020 - 04:52 AM.

#15 Astrojensen

Funny thread and a very, very nice setup, Allan.

#16 starman876

.

Johann, -- yes, I made the custom box for the Unihex and the solar equipment. And yes, I have both the 114 and 128 mount heads for the 2.4" Unitron/Polarex OTA.

Terra, -- yes, I can't let go completely of my past, too many memories and emotions connected with "being at the controls of a Unitron". I hope I can make one of my grandchildren interested in using it, -- small girls now, but they'll be tweens in the wink of an eye.

Carlos, -- indeed, some Scandinavian film noir has crept into my take on the original Unitron add (it' s a pencil btw, in my hand, not a cig :-)

You other guys, --

Never.jpg

So, here's a couple of highlights:

UNI 01.jpg

The objective shows at least 1/8 wave in DPAC (green light). Much better that the "diffraction limited" resolution Nihon Seiko guaranteed. It's housed in an adjustable cell with three "ears" for easy collimation.

I have two 23.5mm diameter, 150mm focal length chromed brass viewfinders. One can use std. 0.965 eyepieces and comes with a 6x EP equivalent to a 25mm FL. It also accepts 8x equivalent to 18mm FL eyepieces. The other has smaller eyepieces and slightly smaller FOV, but features a nice double-cross which I prefer to use.

I've substituted the NS 3-armed metal octograbber with a Zeiss Telementor-like leather strap stabilizer (still have the original, of course). It is easier to collapse/expand the tripod this way, when carrying it in and out for observation. -- And the tripod of course is the adjustable height, sliding leg version, much better in use than the single height bending leg construction.

Some other Christmas sweets, which I'll present to you on a virtual tray, shortly.

-- Allan

and you have the very rare electric drive for the 128. Not many of those sold. Bet yours is 220 volt 50 hertz. awesome DPAC picture.

Edited by starman876, 05 December 2020 - 05:40 PM.

#17 AllanDystrup

Thomas, -- yes,a nice setup indeed, and many toys to play with. That flexibility was one of the factors that set apart the Nihon Seiko scopes from all the competitors, back then.

Johann, -- yes, the synchronous R.A. drive for the 128 is a rare item, and the one I've got is the only one I've ever seen. Some pros and cons (which I can return to later).


The optical quality of the Unitron/Polarex objectives is, as you know, varying. My objective here is above average (

95% Strehl), and very good for a Fraunhofer achromat, even by todays standard. Of course it is only measured in green, so the achromat color dispersion does degrade the view contrast somewhat.

Back then in the 60'ies, even 1/4 wave error P-V (80% Strehl Ratio) was considered excellent, and it was the goal for all Dawes diffraction limited optics, like NS. For example, these views were considered superior back then by Unitron (Mars, Jupiter, Saturn):


Of course, the usage by amateurs in the 60'ies was almost exclusively visual, so the demand for high Strehl was not close to what we came to strive for later with digital imaging. For example the bar for Zeiss telescopes was raised to 90% Strehl for the Maksutov and 95% for the APQs. And asking a very demanding guy like Markus Ludes (of APM), he'd insist that only by 95% Strehl you reach a level of good optics, by 96% very good and from 97-99 excellent. And he's talking visual here, so.

Anyway, with a small aperture high quality optic like my NS 114/128, you very often get a performance close to the theoretical limit, especially in my temperate coastal climate, where larger aperture instruments -- besides issues of collimation and obstruction -- always seem to struggle with seeing and thermal equilibrium:



Returning to the Christmas goodies, here's some info on the backend of my small Unitron scope:

The focuser is the nice double-knob pinion type (good for a GEM mount) with a solid attachment for adjusting the tension on the rack. It has a screw for locking the rack position and a clamp for locking the draw tube. No shifting or wobbling, as can be seen with other small RP focusers.

Here I show an assortment of visual backends: the standard 0.965 EP holder (1), a "convertible" 0.965/1.25" EP holder (2), a 1.25" EP holder (3: not common, bought from UNITRON some years back), plus a custom-made NS/T2 thread adapter (by Xavier some years ago). All these thread into the NS drawtube.

For the Unihex, there's the std. short drawtube (5) but also a Unihex/T2 adapter (6, also by Xavier), onto which I can screw for instance a T2 1.25" nosepiece (a) or a T2 quick change ring (6b). And there's an assorted set of standard 0.965 NS eyepieces (9) plus the larger 40mm Mono and the 24mm Erfle.

My most used visual backend the last years has been the T2 custom adapter, either with the "click on" Unihex or with a Baader diagonal and modern 1.25" eyepieces. Works like a charm!

Oh, did I mention that back-focus has never been an issue with these Unitron scopes ?

Edited by AllanDystrup, 06 December 2020 - 05:52 AM.

#18 strdst

(it' s a pencil btw, in my hand, not a cig

So in Denmark, you smoke pencils, eh?

After gazing upon the Questar goddess I was considering lighting up, but then BadBack had to spoil the moment. Bad, badback!

#19 AllanDystrup

strdst, -- yeah, my wifie quit smoking some decades ago now, and I never adopted that habit, so a pencil was what I decided to light up for that photo op. In Denmark in general the youth seem to be inhaling anything these days, -- (e-)cigs, bongs, joints, N2O cartridges, whatever. But I think sparking a doobie for the dubbed add would risk breaking the illusion.

Viewing the sun comes with a warning from Unitron: “One instructive experiment is to light your pipe by holding it at the focal point of a telescope directed at the sun”. Not smoking a pipe at the age of 12, I never got to execute this experiment…

For solar observation, Unitron provided several solutions:

  1. A matching set of metal plates (Solar projection screens): a black shade plus a white screen for the projected image, both sliding onto a chromed brass rod, which can be mounted on the OTA by brackets. This was the generally recommended method, and it works fine. The set I have for the 114/128C is especially nice, because the brackets for mounting the whole projection apparatus are fixed onto a small block, which in turn can be easily mounted/removed from the OTA using just one large thumbscrew.
  2. An OD5 eyepiece sun filter (sun glass) that can be screwed onto the top of any Unitron 0,965” eyepiece. Unitron advised using the sunglass for visual observation only up to up to 4” aperture. For photography and for visual observation with the 4” and larger, Unitron advised stopping down the aperture by mounting a solar diaphragm over the dew shield. Though all kind of eyepiece filters are of course banned in modern solar astronomy, I must admit to having used this method in my youth on my 3” Unitron with quite pleasing results. After a year or so, I became more aware of the risk though, and therefore upgraded to a 1000-Oaks front glass solar filter, which besides being safe offered much better views of the Suns photosphere.
  3. A OD2 solar wedge (Herschel sun diagonal), which was introduced around 1958 For visual, it requires an OD3 neutral filter, but then it offers splendid views fully on par with the modern LUNT wedge. In recent years, this has been my preferred method of solar observation in white light with the small Unitron scope.
  4. Finally, of course you can use a modern glass or mylar OD5 filter in front of the objective, which gives almost (but not quite) as good a view as the Herschel wedge.

Edited by AllanDystrup, 07 December 2020 - 02:53 PM.

#20 Corcaroli78

will you release an unboxing of your Telemator / Teleminor case in the future? i would be happy to see the whole collection to be inspired. :-)

All the best Allan, Greetings from Vejle,

Edited by Corcaroli78, 07 December 2020 - 06:19 AM.

#21 AllanDystrup

Carlos, — indeed, it could be a fun activity to unwrap my classic Zeiss Telemator & Teleminor setup with accessories.

I have considered doing that for Xmas next year, and then perhaps the Zeiss APQ with all tidbits in december 2022.

You’ll have to be patient, it seems

Edited by AllanDystrup, 07 December 2020 - 06:53 AM.

#22 AllanDystrup

The Mount
"Nōlī turbāre circulōs meōs!

#23 AllanDystrup

As shown above, the UNITRON mounts have setting circles for DEC and RA, but where the larger 3” and 4” scopes have verniers that can be read to a precision of 5’ DEC and 1min RA, the small 1.2” models 114/128 have simple index lines that can only differentiate down to 30’ DEC and 10min RA. It seems that it would have been not much trouble to provide verniers also for the small models, but for some reason Nihon Seiko chose not to.

Both circles can be rotated and must be initialized (fixed) so that DEC=90° when pointing at the celestial pole (

Polaris on the N hemisphere), and RA=0 h (aka 24 h ) when the declination axis is in horizontal position (i.e. the OTA is pointing at the meridian). Setting DEC to 90° minus the local latitude when in initial position, will result in the DEC being 90° in home position (assuming the mount is correctly levelled). UNITRON got this wrong in their manuals btw.

Thus initialized, the OTA can be directed at any celestial object when you know the Local Star Time (LST) plus the Declination (DEC) and Right Ascension (RA) of the object. The latitude of the object is directly set on the DEC circle. One method for setting the longitude (advocated by UNITRON in their manuals), is using the relation: Local Hour Angle (LHA) = LST – RA. Today LST, RA and even LHA is calculated and directly show in planetarium apps like “Stellarium” on your smartphone, so all the fuzz with nitty-gritty table interpolations and manual calculations of the past are gone today.

Edited by AllanDystrup, 11 December 2020 - 11:51 AM.

#24 AllanDystrup

As previously indicated, NS offered several 90° angled prism diagonals for their series of Unitron/Polarex refractors: a star diagonal, the rotary eyepiece diagonal ( UNIHEX ) and a sun diagonal (Herschel Wedge), -- all inverting East<->West of the FOV. An erecting porro prism diagonal for straight through RACI terrestrial viewing was also part of the standard accessories delivered with an NS refractor. For RACI astronomical viewing (of primarily the Moon), I’ve always preferred a good roof prism, and I have an acceptable 0.965” classic one, which looks like it was produced by NS or one of its subcontractors (but I don’t know that for sure). The roof diagonal is not as big and clunky as the porro version, and it also offers a bit brighter image.

For higher magnification views, NS offered 2-element achromatic 2x amplifiers (Barlows): a short one for inserting directly into a star or erecting diagonal, plus a longer one for insertion into the backend draw tube before the diagonals. Both these 2x amplifiers work OK with the 0.965” diagonals of the day. NS also made a 2x Barlow specifically for the UNIHEX , but that one did not did not work well, so I’ve preferred using the eyepiece rotator with modern Barlows instead. And of course a modern 1.25” diagonal with better glass and coating will squeeze out all the juice the Fraunhofer objective has to offer, yielding the widest, brightest and sharpest fields of view with this little telescope.

Speaking about modern accessories, NS also sold a UNICLAMP bracket for attaching extra equipment, which in those days would often be a film camera. With up to 10min exposures on a medium-fast film you could easily get down to 10 m stellar magnitude, which was not bad at all. These days I have used the UNICLAMP for my small digital pocket camera (wide field images of the Moon) and also as a tracking platform for my night vision monocular, getting views and short recordings (with my smartphone camera+adapter) of ionized gas clouds in the Milky Way (using a narrow-band Hα filter).


David Lunt (1942-2005)

By: Richard Tresch Fienberg January 18, 2005 0

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David Lunt stands at the entrance to his office in Tucson, Arizona, in October 2001. As the creative force behind Coronado solar filters, Lunt revolutionized amateur astronomy by designing and manufacturing affordable hydrogen-alpha filters and telescopes.

S & T photo by Rick Fienberg.

At the first "Hands on the Sun" workshop, held in October 2001 in Tucson, Arizona, Coronado's David Lunt watches as astrophotographer Jack Newton checks out the view of the Sun in a Tele Vue-102 refractor fitted with a Coronado hydrogen-alpha filter.


Any simple experiment with an H-alpha telescope? - Astronomy

David Arditti tests out a new hydrogen-alpha filter for refractors marketed as ‘quick, cheap, easy and fun’.

American company Daystar has a respected name in the solar telescope field. For many years they have been producing, amongst other products, high-grade hydrogen-alpha filters that fit to the eye end of a telescope. In contrast to the type of filter that goes at the objective end, or is fixed inside, this design necessitates adding a Barlow lens first to make the light from the objective sufficiently parallel for the filtration to work. The best of these eye-end hydrogen-alpha filters also use a heating element to raise the filter to a precisely-regulated temperature at which it is optimally ‘on band’ to reveal the chromospheric surface details.

A new twist to an old idea

The new Daystar Quark ‘eyepiece’ is actually not an eyepiece at all, but a new manifestation of this eye-end filter idea: a cylindrical unit the size of a large two-inch eyepiece that fits in the draw-tube or diagonal of your existing refractor, and takes a 1.25-inch eyepiece or a camera nosepiece. It comes with a power supply for the heater and has a knob that adjusts the temperature to alter the tuning of the pass frequency. Importantly, it is set at a price point well below other Daystar filters, and below all but the smallest (40mm aperture and under) dedicated hydrogen-alpha telescopes. It has a smart anodised black and red aluminium housing, with both two-inch and 1.25-inch barrels, and a brass compression fitting for the eyepiece.

The specially optimised Barlow, which gives an amplification of 4.2 times and contains its own blocking filter, is built-in and cannot be substituted for another one as it has special coatings and Daystar have given it a unique thread. The Quark is said to be compatible with f/4 to f/9 refractors. For telescopes of less than 120mm aperture, Daystar suggest using an ultraviolet and infrared cut-off filter (not supplied) screwed on in front of the diagonal, which reflects these invisible wavelengths back up the telescope to prevent the focal area from getting too hot. This cannot work with an oil-spaced objective or a Petzval telescope and above 120mm aperture, Daystar recommend an energy rejection filter be used over the objective instead. For brief observing sessions with a telescope under 80mm aperture on a non-tracking mount, Daystar say that having no other filter may be satisfactory, but I did not risk this.

A filament imaged through the Quark using a DMK 41AU02.AS camera and a 66mm f/5.9 refractor, on 29 June 2014. Image: David Arditti.

This review first appeared in our August 2014 issue.

The Quark comes in two editions at the same price, a ‘chromosphere’ version and a ‘prominence’ version. The former is quoted with a bandpass of 0.5 to 0.3 Ångstroms (0.05 to 0.03 nanometres) depending on your telescope’s f-ratio, while the latter has a bandpass of 0.8 to 0.6 Ångstroms. However, as the prominences are nicely visible in the chromosphere version (which I tested), I am not clear why anyone would want to pay the same for the wider bandpass version that is only capable of showing prominences.

Consider your focal lengths

Comparing the image using the Quark on the 66mm refractor with the view through my Lunt LS60T double-stacked hydrogen-alpha telescope I found that the Quark view was far more uniform, with detail visible simultaneously across the Sun’s disc and around the chromospheric ring, whereas the view through the Lunt had higher contrast in its ‘sweet spot’, but required the Sun to be moved around the field to see the details in all areas. The contrasts in the disc features (filaments and active areas) through the Quark were fairly subtle and required a bit of time to trace, though all the same features were there. Top-quality front-end filter systems that I have observed through give higher contrast and the same uniformity, but it must be noted the Quark is a fraction of the price of these. The Quark on the end of the 100mm f/9 proved a good system for observing detail in prominences, although the minimum magnification was too high to really get a good impression of the surface.

Use your diagonal correctly

Use of a diagonal needs a bit of consideration. A two-inch diagonal can only go between the telescope and the Quark. A 1.25-inch diagonal could go either side, but the arrangement would be more stable if you placed the diagonal after the Quark. This might necessitate putting a draw-tube extension on a telescope with ample back-focus, as the Barlow in the Quark is telecentric, meaning it requires to be at a certain distance from the objective. On a telescope with limited back-focus, a 1.25-inch diagonal placed after the Quark might be the only diagonal viewing option.

Another issue to think about is the power supply. The supplied mains unit and lead is not going to be very convenient unless you have an observatory. Fortunately the retailer also supplied me with a five-volt rechargeable USB battery. If you are going to be doing public observing, you need to weigh up how convenient it is to have a device that requires power, with a lead that can be easily pulled out. I found the Quark takes about 15 minutes to get to temperature again, in the cloudy climate of the UK, this is a potential disadvantage as your window of clear skies might be gone by the time it is on-band.

The Quark in straight-through imaging configuration on a 100mm refractor. Image: David Arditti.

The Quark on a two-inch diagonal. Image: Daystar.

To use a camera with a Quark requires it to have a 1.25-inch nosepiece. Daystar have not supplied the unit with a T-thread, which would have been better I suggest they think about the imaging application more carefully. I took some images with the 66mm and 100mm telescopes with a DMK camera and a Lumenera camera and, although conditions were not optimal, I think I showed that the device has serious imaging potential.

The Quark is an effective and well-priced product for opening up the vistas of detailed solar hydrogen-alpha observing and imaging to refractor owners, subject to the reservations on focal length I make above. For visual use I think it is really best suited to the shortest instruments it would be good if Daystar could produce a version with less powerful amplification for longer refractors. I suspect it will prove most attractive to those taking a small telescope and mount on holiday to a dark site, who would like to add a high-grade solar capability without carrying too much extra luggage. For this purpose the Quark would be excellent.


The 5 Most Ingenious Experiments in Astronomy and Physics

Paul Sutter is an astrophysicist at The Ohio State University and the chief scientist at COSI Science Center. Sutter is also host of Ask a Spaceman, RealSpace and COSI Science Now.

Our modern understanding of the universe is built upon hundreds of experiments spanning centuries, all designed and implemented by thousands of creative, hardworking scientists. Naturally, a select few of these experiments stand out as especially groundbreaking, because they transform our view of the way things work. A different exercise is to select the most clever experiments — those that uncovered some simple fact of the universe through ingenuity rather than brute force.

Without further ado, here are my top five selections for the most ingenious experiment in physics and astronomy — in no particular order.

First exoplanet
In 1992, it had been more than 60 years since the discovery of Pluto, and astronomers were itching to find a new planet — not in our solar system, but around another star. They knew that by carefully observing the light from a distant star, they could see the telltale changes in the wavelengths of light, called redshifting and blueshifting, as any planets wobbled the star back and forth over the course of their orbits. [How Do You Spot an Alien Planet from Earth? (Infographic)]

Too bad we didn't have sensitive enough observations of starlight to read the traces of orbiting planets at that time. The exception was pulsars, which form from the remains of some stars after they go supernova. Those objects' almost-unnaturally precise signal, which is caused by beams of radiation jetting away from a rapidly rotating neutron star, could be used to detect the gravitational influence of orbiting exoplanets. The gravitational tug changes the timing of the pulsar blasts in a way that scientists can measure.

But how could a pulsar host a planetary system? The violence of a star's final days would surely destabilize any orbits, leaving the local vicinity barren. Apparently, nature doesn't care for reasonable questions like that, because the first exoplanets identified were orbiting pulsar PSR B1257+12.

Here's the clever bit: using an oddly precise system generated by nature itself to tease out a difficult detection.

Size of the Earth
It doesn't take much thought to realize that the Earth is round: Ships at sea disappear from view bottom-first, the Earth's shadow during a lunar eclipse is circular, stars that are visible in the Southern Hemisphere can't be seen from the Northern Hemisphere, and so on. Many ancient peoples (at least those who had the luxury of thinking about the problem), including the Greeks, generally seemed to accept that fact.

But just how big was that giant orb?

Leave it to Eratosthenes, a smart Greek living in Alexandria around 250 B.C., to cleverly measure the circumference of the Earth without even having to leave his city. He knew that a city in southern Egypt, Syene (near modern-day Aswan), experienced no shadows during the summer solstice but Alexandria did.

Well, if Eratosthenes knew the distance to Syene, if the Earth were perfectly spherical, if the sun really were absolutely directly overhead Syene during the solstice, and if Alexandria and Syene lay perfectly along a North-South line, then he could use the length of shadows in Alexandria during the solstice to measure the angle between the two cities, and convert that into the planet's circumference using this newfangled technique called geometry.

It turns out, all those conditions are close enough to correct to allow Eratosthenes to measure a circumference of about 45,000 kilometers (28,000 miles) — only 10 percent off from its correct value.

Einstein's thought experiments
Not all experiments happen in a laboratory sometimes you can just think of an imaginary scenario, let mathematics guide you to a conclusion, and — presto — learn about the universe. Einstein was, naturally, a master at this.

As recalled by Einstein, his first "gedankenexperiment" (German for "thought experiment") occurred during his precocious teenage years: What if he could race a bicycle alongside a beam of light — at the speed of light? What would he see? [Video: The genius of Einstein's thought experiments]

Because light is made of waves of electricity and magnetism, Einstein figured he would see those waves frozen alongside him as he pedaled furiously. But we don't see frozen waves of electricity and magnetism. Anywhere. Ever. So maybe, instead, it's impossible to travel as fast as a beam of light. Anywhere. Ever. Start with that thought, and do a bunch of math, and before you know it, you've developed the theory of special relativity.

Einstein pulled a similar trick later in life, as well. What if you were in a windowless elevator and someone cut the cord, sending you into free fall? Are you plummeting to your death, or simply kicking about in the weightlessness of free space?

Einstein's answer: It's impossible to tell the difference. Inertial mass (the response of a body to any force acting on it) is the same as gravitational mass (the strength of an object’s reaction to gravity). Take that simple concept and a significant amount of mass, and out pops the theory of general relativity. Neat. [Einstein's Theory of Relativity Explained (Infographic)]

Millikan's oil drop
This experiment, performed by physicists Robert Millikan and Harvey Fletcher in 1909, isn't clever because of its ingenious design or attempts to outwit nature at its own game, but rather because of its simple construction and unflinching honesty of measurement. I also picked it because it doesn't get a lot of airtime despite being historic.

Back in that time, scientists knew that electric charge existed, but they didn't know much at all about it. Were there fundamental bits of charge? Or could something have any amount of charge, as mass can? What's the charge on an electron, anyway?

So Millikan and company built a device that dripped drops of electrically charged oil through a chamber. Very quickly, the falling drops would reach terminal velocity, which is the maximum speed at which they can fall through the air due to the pull of gravity. If you know the density of air, the density of oil and the strength of gravity, measuring the terminal velocity tells you the mass of the drops.

By applying an electric field, Millikan could halt the drop of the drips (or the drip of the drops, if you prefer) and make them hover in place. With the electric force perfectly balanced by the gravitational force, the charge on each drop could be measured.

After repeating such measurements many times, Millikan was able to make two conclusions: The charge on a single electron is minus 1.6 x 10^19 coulombs, and that charge is fundamental — all charges must be built out of units that size. Want to have a charge of minus 1.9 x 10^19 or 8.7 x 10^19 coulombs? Too bad. You're not allowed.

Foucault's pendulum
Like the curvature of the Earth in ancient times, in the mid-1800s, the rotation of the Earth was generally accepted by people who had the luxury of thinking about such things, but not really talked about or understood in the way we might talk about, say, the antics of the latest reality TV star.

Physicist Léon Foucault wanted to change that, and he did so in suitably grand fashion. If you leave a pendulum to its own devices (that is, swinging) the Earth literally rotates underneath it while the pendulum maintains its original plane. From our perspective attached to the rotating Earth, it looks as though the ground were fixed and the pendulum were rotating its orientation over the course of the day.

In 1851, Foucault set up such a pendulum in the Panthéon of downtown Paris, thus demonstrating the Earth's movement by slowly changing its orientation clockwise — at around 11.3 degrees per hour. It was a huge spectacle, and the media loved it. The demo went viral (well, as viral as it could in the 1800’s), and soon enough, Foucault's pendulum was a mainstay of science exhibits around the world.

It was exciting! People were talking about the rotation of the Earth! And that's the clever bit here: making science accessible and something worth talking about.


A quick thought experiment

lately I‘ve been thinking about the human ability of detecting colors in space.

Now imagine you are on earth taking a peek through your telescope and there it is – the Orion Nebula. This powerful piece of gas and dust shoots out new stars and yet it appears in black and white to the human eye. Next thing you know, you are already attaching the camera to your telescope and you start taking a series of long exposure shots. The outcome is a magnificent play of colors and shapes.

Now picture yourself flying towards it in an imaginary spacecraft. Forget about the laws of physics and answer this: had you been able to shorten the distance between yourself and the nebula or even get there as close as you could, would you be able to see it in its full color and glory exactly as you see it in your long exposures? Could the perception of the human eye be as good as the image sensor? Is it really only a matter of distance? Or does it have something to do with our unfortunate inability of perceiving what really goes on up there and eventually it doesn't look as magnificent to the human eye as one would wish for?

What do you think? Care to venture a guess?

#2 ShaulaB

The human eye evolved to adapt for survival with light conditions encountered on Earth. I doubt if just getting a few light years closer to objects would increase the chance of us seeing a diffuse object like M8 as red.

Another interesting question--if you are flying at 1% of light speed toward Andromeda, would M31 look bluer?

#3 cookjaiii

The rod cells in our retinas are more sensitive than our cone cells, so faint light is perceived as B&W. We need more light to trigger a signal from our cone cells. The way to do that with an earth-bound telescope is to use more light gathering aperture. I have read accounts on CN from people with 20" Newts and larger, who claim to see color in the Orion nebula. Another way to gather more light on the back of our retinas would be to get closer (as in your thought experiment). The inverse square law applies so the closer we get to the light source, the more intense the light we see.

It should be a simple matter to calculate how much closer you would have to be in order to see the same amount of color you can see in a 20" earth-bound telescope. Or maybe not so simple since you would have to take Earth's atmosphere into account.

Edited by cookjaiii, 09 August 2019 - 03:19 PM.

#4 David-LR

The rod cells in our retinas are more sensitive than our cone cells, so faint light is perceived as B&W. We need more light to trigger a signal from our cone cells.

It why in low light at night, we see only B&W. I would think in space it would be the same until you were really close to the nebula.

Edited by David-LR, 09 August 2019 - 03:24 PM.

#5 Alan French

The Orion nebula is bright enough to allow some color perception and a large aperture is not required.

Under dark skies, the green of the Orion nebula is not hard to see in a 10-inch Newt. Also look for a touch of red in the eastern arm.

With experience and excellent sky conditions, the green can be seen in considerably smaller apertures.

#6 TOMDEY

Except for getting through a bit of intervening atmosphere, dust and gas. the étendue, and therefore the luminance of the glowing gas is invariant with range. So, it would look pretty much the same. just bigger. The stars would, of course, look brighter, but the gas would just look more expansive, but not more luminous or colorful. And that is what you get, when you use "Rich Field Binoculars.". where the magnification is only

3.5x per inch of aperture. or less. That's as good as it can get. Tom

#7 ngc7319_20

Flying to the Orion nebula would not help much. When you got there you would be surrounded by a tenuous gas and a dim glow. The brightness from just outside the nebula would be about the same as in a large scope from earth with a nominal 7mm exit pupil. What would change is the solid angle in the sky subtended by the nebula.

The eye is not very sensitive to dim red light, so you would still not perceive the H-alpha light. It would mostly look green ([OIII] emission) as it does from a large scope on earth.

#8 TOMDEY

PS: I see the greenish OK, but not red or pink. Have become convinced that the reds are wishful thinking, kind of a placebo coloration. That is. if you firmly believe you should see the red. it actually appears to be red! The tricky part is, you can't tell people about Santa, the Easter Bunny, or M42's subtle reds. or. well, we know.

Ummm. Uhhh. (Nuts!) Yes, YES! The Great Orion Nebula shows green and red! It takes practice, experience, dark skies and a spanking clean telescope. But it is there! Here's my picture, to prove it. >>> Tom

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#9 Waddensky

#10 ChristinaKa

Oh wow, these are many different perspectives! Thank you all, guys, for your interesting insights.

Let’s review: some of you are skeptical that shortening the distance would make any difference in the perception, but some of you agree that seeing colors in space with the naked eye is not impossible. Maybe not exactly as in a long exposure and maybe not all colors that are usually captured by the image sensors of our cameras, but still not completely black and white.

Can we all agree on this? Or am I forgetting an important aspect of this discussion?

#11 TOMDEY

What people are able to see varies a fair amount. What people claim they can see varies a lot!

#12 Jon Isaacs

Oh wow, these are many different perspectives! Thank you all, guys, for your interesting insights.

Let’s review: some of you are skeptical that shortening the distance would make any difference in the perception, but some of you agree that seeing colors in space with the naked eye is not impossible. Maybe not exactly as in a long exposure and maybe not all colors that are usually captured by the image sensors of our cameras, but still not completely black and white.

Can we all agree on this? Or am I forgetting an important aspect of this discussion?

What I see is a consensus that traveling closer would not make much difference since the surface brightness is independent of the distance to the object.

In also see a general agreement that there is green visible in the Orion nebula at larger exit pupils. Larger apertures help because they make the Orion nebula larger at larger exit pupils. I see the green regions on the right night in my 12.5 inch under dark skies. I see more in my larger scopes.

I agree with Tom Dey, I see faint rust colors at times but I believe they're artifacts of the visual process, the brain interpreting clues incorrectly.

#13 TOMDEY

I guess very few people will remember this any more. but, if you had a traditional Photographic Darkroom. remember that little red light that you would use, when processing B&W Prints? And how it wouldn't really look red, but just sorta neutral? Only staring straight at it would look dull red. Then, you turn on the white light, and the red light looks saturated Beet Red!

So, I can en-vision where the bright green in M42 might help trigger better perception of the red next to it. by some threshold color-contrast? Thing is, are those red filaments really any redder than what we see as green in the bright parts? That is to say --- why does my color picture up there just look white and red? --- why doesn't the green that we see display to the color film? What I'm speculating is that they are actually the same color (same point on the normalized IES/CIE XYZ-space color palate). If that's true, then

turning up the brightness

leans green perception, and turning it down leans red perception. even though the spectra are identical mix of oxygen and hydrogen. Hmmm. Tom

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#14 Tony Flanders

Let’s review: some of you are skeptical that shortening the distance would make any difference in the perception

Getting nearer to the Orion Nebula would make only a very minor difference, and almost all of that difference would occur during the first 10 miles of your 6-quadrillion-mile trip, namely the part that gets you through Earth's atmosphere.

Some of you agree that seeing colors in space with the naked eye is not impossible.

"In space" is irrelevant. You can see these colors through a telescope from Earth's surface -- and in some cases, with your unaided eyes.

The Orion Nebula does indeed appear greenish and possibly red to many if not most people. But there are many celestial objects that appear colored to almost everyone. Betelgeuse is a prime example of a naked-eye colored star, and there are many stars that appear much deeper red than Betelgeuse through a telescope.

Among non-stellar objects, many small planetary nebulae appear quite strongly bluish or greenish.

#15 Phil Cowell

Hey guys,

lately I‘ve been thinking about the human ability of detecting colors in space.

Now imagine you are on earth taking a peek through your telescope and there it is – the Orion Nebula. This powerful piece of gas and dust shoots out new stars and yet it appears in black and white to the human eye. Next thing you know, you are already attaching the camera to your telescope and you start taking a series of long exposure shots. The outcome is a magnificent play of colors and shapes.

Now picture yourself flying towards it in an imaginary spacecraft. Forget about the laws of physics and answer this: had you been able to shorten the distance between yourself and the nebula or even get there as close as you could, would you be able to see it in its full color and glory exactly as you see it in your long exposures? Could the perception of the human eye be as good as the image sensor? Is it really only a matter of distance? Or does it have something to do with our unfortunate inability of perceiving what really goes on up there and eventually it doesn't look as magnificent to the human eye as one would wish for?

What do you think? Care to venture a guess?

EAA brings out the colors as your looking at the object. It’s something to see.

#16 Araguaia

Have become convinced that the reds are wishful thinking, kind of a placebo coloration.

Absolutely not! Certainly not on M42, where the red is as bright and vivid as it gets.

I have been testing this rigorously. I have been observing objects that glow faintly green, as well as plain greyish-white, trying to see if I could "see" illusionary red in the fainter parts due to the contrast effect. On some I can, on some I cannot. As you say, it takes effort and wishful thinking. But it is easy enough to learn to recognize the contrast illusion by its constantly shifting nature and by its uniformly pale orange hue.*

I just had my first look of the season at M42 a couple of nights ago. The ruby red jumped out at the first glance at 51x. Not at all like a contrast illusion! And at high power you can find its brighter knots and borders with the green, and they don't float around indistinctly like in the contrast illusion.

* the Carina Nebula does glow in rich orange, but not at all the same hue as the illusory one, and you can clearly see tendrils of bright nebulosity and a sharp filigree of dark dust overlaying it. I have never heard of someone who has seen the Carina Nebula and questioned its color.