Some digiscoping experiments with a dslr (1 Viewer)

[vkalia]

I want to thank all the participants on this thread for a one of the most informative discussions I have read in a long time. Paul, my hats off to you for your extensive experiments in this area.

I have been playing with digiscoping with my Vortex Skyline ED scope (decent for viewing, but not the best by any means) as I want to try to find a practical way to get an effective focal length of 2500mm + (in 35mm terms).

I was resigned to settling for a digicam (resigned mainly due to lack of RAW) but this thread has opened up a lot of possibilities for me.

Now I'm thinking of a scope with the following potential configs:
- 30x WA eyepiece to which I can attach either a 3x digicam for combining birding with photography
- 20-30x WA eyepiece, DSLR with 28-50mm lens and TCs/spacers.

The threaded Baader eyepieces - which work with Zeiss Diascopes and may work with the Pentax 80mm - seem really attractive.

I did have a question for Paul and others - have you tried using a longer focal length than 50mm - perhaps a 100mm lens? With a narrower field of view, that might pair better with a higher power eyepiece, providing for obscene amounts of magnification (enough to tell if those flies at 35m were male or female, perhaps? )

Vandit

 

[Paul Corfield]

From my own experiments, for high magnification I found it best to go with good quality high power eyepieces coupled to low power camera lenses to keep the brightness up at the camera. A high power lens on the camera will mean light levels really suffer. I tried a 135mm lens once but shutter speed really suffered. You could possible get away with 80mm on a sunny day. On the hand I've used my 28mm lens through a 13mm eyepiece (45X on my scope) and that works fairly well.

On my astro style scope I can get out to around 3300mm with a 1.5X and 2X converter stacked together. I took another fly photo (see below) from 35m with this method on my old Samsung dslr just before it got broke. I shall try this with the Canon 450D when I get the scope adapter I'm waiting for, hopefully next week.

Only thing with this sort of magnification is you need good clear air, no heat shimmer in the air, a good tripod and shutter release.

Paul.

 

[JGobeil]

Vandit,

Don't forget that the Vortex Skyline does not have interchangeable eyepieces. I sold mine because of that.

I then got a Pentax PF80ED with a good WX20 eyepiece and was quite dissattisfied with the results - although results were acceptable, I was never able to get really sharp pics like some you have seen in this thread. I tried both DSLR (Canon 20D) and P&S (Nikon P5100). Maybe I got a bad one...

I have purchased a 600mm APO ED astro scope that I will try in prime focus digiscoping, like Paul. I should get it next week. Results to follow.

Good luck with digiscoping, I wish you success and pleasure.

 

[bluedubius]

This has been a very informative thread and I would like to thank Paul and all who have contributed. Last week I came across a deal on a Celestron 80ED refractor new for $384 shipping included. I have been digiscoping with a Meade ETX-90 maksutov-cassegrain asto scope for a few years, but always wanted to try an ED refractor. Here is one photo taken of a Bluejay this morning with the Celestron 80ED with a Fuji S2 Pro camera with an extension tube only. The cardinal photo was taken with the ETX-90 thru the rear photo port and photo adapter at the same distance (around 40 feet) with the same camera. I was quite happy with both attempts and look forward to more opportunities. Want to try a 1.5 teleconverter next.

Rick

 

[vkalia]

Paul, thanks for that information re. lens and EP power. Now that you mention it, I think you had made this point earlier in this thread as well but I guess it hadnt registered.

Jules - you are right re. the Vortex. It is a very nice scope for the money (I got a great deal on mine) but no interchangeable EPs & physical size are issues - I am indeed looking for another scope (trying to decide between the PF80 and the Fieldscope 82ED - am open to Zeiss/Swaro/Kowa if I think they'll provide better images).

I wonder if astro telescopes are better suited to higher-mag photography than regular scopes - I have come across several references on BF about this being the case. The photos posted by Rick just above are very, very nice as well... and also with an astro scope. Hmmmm.

I guess I need to do a little bit of research into them. Portability and weather sealing are issues for me, which is why I have stayed away from them so far but if the results are good...

Still, I am surprised when you say your results with the PF80 have not been as good. I've seen some really nice images here with that scope. Of course, I have NOT seen all the rejects so it is hard to say how useful this scope is as a photography device.

I was planning to get an 800/5.6 to supplement my 500 and add greater reach, but I can get a Kowa, an astro scope, all the goodies and still save over 50% of the cost of the 800... so this is definitely an option I'm investigating in detail. The big issue is that I am unable to actually demo any of these products. So I'm relying on the excellent discussions here on BF to help me narrow my selections.

Vandit

 

[JGobeil]

IMO, prime focus digiscoping should produce better photos than conventional P&S digiscoping. After a lot of reading and a long reflection, this is why I ordered a refractor scope. Some will hate me for that statement but here are the reasons, as I see it.

1- There is just too much glass in regular digiscoping. There is the erecting prism in the scope, then the eyepiece and finally the camera lens, often of doubtful quality. Each of these introduces a loss of light, distortion and reflections. Prime focus digiscoping uses none of these: there is just a 2 element lens connected to the DSLR. Simple and effective !

2- P&S cameras use very small sensors. The Nikon P5100 cramps 12 million pixels in a tiny 1/1.72" sensor. This brings more noise and less precision.

3- Spotting scopes use an inferior optical design compared to an extremely effective apochromatic doublet refractor scope. See this article from the respected Cornell Lab of Ornithology. On page 3, they compare the Kowa 883 Prominar, which is considered the best spotting scope available, to a Televue 85 Evergreen refractor. "...when reviewers put the Kowa next to the TeleVue, their jaws dropped in amazement."
http://www.livingbird.org/NetCommunity/Page.aspx?pid=272&srcid=265

4- Focusing is much easier with prime focus digiscoping. The astro scope uses a more precise dual speed Crayford focuser. Also, one must rely on the LCD screen when using a P&S camera while the DSLR has a much preferred viewfinder which is brighter, protected from the outside light/sun and diopter corrected if one needs it.

5- They are less expensive.


Of course, the refractor astro scope has its drawbacks.

A- It is not waterproof. Astronomy does not need that.

B- It is not as portable and probably more fragile, mainly because of the design. There are many knobs and screws on the focuser.

C- Some don't have a conventional and simple photography mount. They come with rings made for astro tripods.

C- They are not designed to be used as a spotting scope. One must add an erecting prism to use it with an eyepiece to avoid having a reversed image, both horizontally and vertically. As far as I know, there are no good quality straight erecting prisms so a 45 degree prism must be used.

D- They are heavier.

E- Most come in colours that are far from camouflage... white, gold, silver, sapphire blue !


Low priced ED APO refractor scopes have just begun to be available. I think we will see more and more of these used for digiscoping.

 

[vkalia]

Post deleted - duplicate

 

[vkalia]

Hi Jules -

You are correct that prime focus will probably yield better results - the more precise nature of the alignment alone probably helps. However, prime focus doesnt get you focal lengths that are significantly greater than DSLR lenses - I already have a 500/4, which, paired with a 2x TC and a 1DMk2, gives me 1300mm of focal length, yields publication/stock quality images and 95%+ keeper ratio (as far as technical aspects, such as focus & exposure, go). Example:
http://www.photosafariindia.com/galleries/khichan/img001.jpg

But your point about refractors is a good one. I've just been looking at the Televue unit and frankly, it sounds really appealing. It comes with a 45 degree erector which provides images in the proper orientation, to boot.

Also, as a FYI, as per Televue's website, they have a straight erector and it is their recommended option for people wanting a proper orientation (they say it provided better IQ than the 45 degree unit)

Waterproofing shouldnt be a real issue for digiscopers - waterproof bags/cases can be had and who does a lot of long-distance/high-mag photography while in the pouring rain anyway?

Which refractor are you getting?

Vandit

 

[JGobeil]

Vandit,

Yes, the long guns have a lot of reach. A Canon 600mm, a 2X teleconverter and a 40D yields 38X. However, it costs 10K$... As a bonus, the lens has IS, auto focus and F/4.0.

I would have liked a Televue TV85 or A Williams Megrez 90mm but unfortunately my budget is not that large... I got a Astro-Tech AT80ED. It is an 80mm APO ED refractor that has a focal length of 560mm at f/7. I got it new for a really good price on eBay.
http://www.astronomics.com/main/product.asp/catalog_name/Astronomics/category_name/K56U1T2Q7KWF8GDVGLKVBN1PL3/product_id/AT80ED

I also ordered a true 2" Canon EOS photo adapter instead of a T2 adapter, which should allow more light.
http://www.cncsupplyinc.com/
(See Canon 2" DSLR adapter)

 

[vkalia]

Hi Jules -

The refractor is a 560/7. If you dont mind my asking, why did you choose a refractor over a 500mm zoom lens, such as a Sigma 170-500, which is f6.3 at the long end and about the same price, more or less? If you plan to use prime focus, this would probably be a better solution for image-making... and you can always stack TCs onto it. Art Morris has reported very good results with 2x and 1.4x TCs stacked onto a 600 prime. Admittedly, the zoom is not going to be as good with TCs, but I wonder how the results will compare with a telescope + TCs + prime focus.

I guess the advantage of the scope is that you can also bird with it...

Vandit

 

[JGobeil]

Also, as a FYI, as per Televue's website, they have a straight erector and it is their recommended option for people wanting a proper orientation (they say it provided better IQ than the 45 degree unit)

Vandit

I haven't found this erector on Televue's site but I think that the Televue diagonals, 45 and 60 degrees, are mirror diagonals which correct vertically only - not horizontally. I wonder if the 0 degree is similar ?

 

[Paul Corfield]

I haven't found this erector on Televue's site but I think that the Televue diagonals, 45 and 60 degrees, are mirror diagonals which correct vertically only - not horizontally. I wonder if the 0 degree is similar ?

Televue make a straight porro style erector for astro scopes. Pretty sure the 45° is a prism also. Porro probably better than the 45°.

http://www.televue.co.uk/prism.htm

Paul.

 

[Paul Corfield]

Hi Jules -

The refractor is a 560/7. If you dont mind my asking, why did you choose a refractor over a 500mm zoom lens, such as a Sigma 170-500, which is f6.3 at the long end and about the same price, more or less? If you plan to use prime focus, this would probably be a better solution for image-making... and you can always stack TCs onto it. Art Morris has reported very good results with 2x and 1.4x TCs stacked onto a 600 prime. Admittedly, the zoom is not going to be as good with TCs, but I wonder how the results will compare with a telescope + TCs + prime focus.

I guess the advantage of the scope is that you can also bird with it...

Vandit

As an example I took a photo today on the Skywatcher 600mm with my 1.5X and 2X converters stacked together (3360mm equivalent on the 450D). The 1.5X is a Vivitar and the 2X is a 7 element Komura Telemore 95 II 7KMC. They aren't the quality of say a Kenko Pro 300 but produce acceptable results. My goal is to get a couple of Kenko's but that's for the future.

Paul.

 

[JGobeil]

Hi Jules -

The refractor is a 560/7. If you dont mind my asking, why did you choose a refractor over a 500mm zoom lens, such as a Sigma 170-500, which is f6.3 at the long end and about the same price, more or less? If you plan to use prime focus, this would probably be a better solution for image-making... and you can always stack TCs onto it. Art Morris has reported very good results with 2x and 1.4x TCs stacked onto a 600 prime. Admittedly, the zoom is not going to be as good with TCs, but I wonder how the results will compare with a telescope + TCs + prime focus.

I guess the advantage of the scope is that you can also bird with it...

Vandit

Darn good question... I hesitated a long time with this one. In fact, I went with the scope for 3 reasons:

1-Price: I paid 380$ for the scope...

2- I had seen some of Paul's pictures taken with stacked converters in this thread and I don't think a Sigma zoom can do that. IMO, a single 1.4X converter is already stretching a zoom lens to its limits. I own a Canon 100-400 IS lens and it does fine with a 1.4X, very soft with a 2X and extremely bad with the 2 stacked. Today, Paul does it again with his photograph. By the way, Art Morris is stacking teleconverters on a 8000$ 600mm Canon lens - not in the same game...

3- I want to explore regular digiscoping with an eyepiece and a DSLR with lens attached. Extreme magnifications can be attained.
EX: 20D+50mm and scope with 14mm eyepiece = 64X - Add a 1.4X teleconverter and you reach 90X. One can also experiment with a 2X teleconverter and reach even bigger magnifications.

Of course, at those magnifications, every little detail counts: one needs a clear sky with lots of light, total absence of haze or smog, no wind, extremely stable tripod and head, remote shutter, mirror lockup, etc. But that should be fun.

My plan is to experiment with this scope and then maybe get a bigger top quality scope like the 110mm William Optics Megrez doublet: 655mm f/5.9 or one in the 7-800mm range.

 

[vkalia]

As an example I took a photo today on the Skywatcher 600mm with my 1.5X and 2X converters stacked together (3360mm equivalent on the 450D).

Very nice shot - far better than I'd have expected from such a setup, to be honest.

At some point, Paul, would you be interested in conducting an experiment? I'll mail you a test chart -or we can use a commonly-accepted test chart. I'll take some shots with my 500/4 + stacked TCs, and you take them with the 600mm refractor + TCs. I'm only going to have access to my 500 when I'm back after my current trip at the end of July, however.

I'd be interested in seeing how the results play out...

Regards,
Vandit

 

[vkalia]

2- I had seen some of Paul's pictures taken with stacked converters in this thread and I don't think a Sigma zoom can do that. IMO, a single 1.4X converter is already stretching a zoom lens to its limits. I own a Canon 100-400 IS lens and it does fine with a 1.4X, very soft with a 2X and extremely bad with the 2 stacked. Today, Paul does it again with his photograph. By the way, Art Morris is stacking teleconverters on a 8000$ 600mm Canon lens - not in the same game...

In principle, I agree with you. I have both the 100-400 and the 500 (which is optically very similar to the 600) and my findings agree with yours *wide open*.

What I havent done is tried shooting the zoom tele stopped down a couple of stops. I suspect this will improve sharpness significantly - especially on a good, sturdy tripod.

Actually, based on the eye-opening images Paul is posting, I do think that the refractor+TC setup will be sharper still... but the greater responsiveness of a DSLR + lens is something to be traded off. The big question for me is, what is the quality difference and is it enough to justify the loss of operating speed?

I'd dearly love to perform the experiment posted above - perhaps a group of us can get together and try it with various setups. For ease of comparison purposes, it would be best to use a standardized subject at a fixed distance.

I'd be happy to analyze, host and post the results.

3- I want to explore regular digiscoping with an eyepiece and a DSLR with lens attached. Extreme magnifications can be attained.
EX: 20D+50mm and scope with 14mm eyepiece = 64X - Add a 1.4X teleconverter and you reach 90X. One can also experiment with a 2X teleconverter and reach even bigger magnifications.

Yeah, this is also the big appeal of refractors for me and why I am considering one.

I am trying to decide on a refractor myself. The Televue 85 sounds really nice but lord it is heavy and large. I might be more tempted by the smaller Televue 76.

My plan is to experiment with this scope and then maybe get a bigger top quality scope like the 110mm William Optics Megrez doublet: 655mm f/5.9 or one in the 7-800mm range.

Do you have any suggestions on good sites to read up on various astro scopes?

Btw, here is a link to the Televue site about their erectors - see point #2:
http://www.televue.com/BirdScope/Tables/Telescopes4DaBirds.htm

Regards,
Vandit

 

[JGobeil]

I would be interested in taking part in the test. I have a Canon 1.4X and a Tamron 2x Pro. We would be able to compare 2 different setups of refractors. It would be interesting to compare without the teleconverters also.

 

[JGobeil]

Vandit,

This is what I thought, the Televue diagonals are horizontally reversed, except the 45 degree one. This makes spotting quite difficult unfortunately.

A good place for the scopes is Anacortes, they offer more than 200 different refractors. You get all the specs, a description, some reviews and of course price:
http://www.buytelescopes.com/product_list.asp?t=1

I suggest you look for the OTA models since they are stripped scopes without the tripod and often without the 90 degree diagonal, which are not needed for our use.

IMO it is also important to choose a model with a dual speed precision focuser. Also, the focuser should be able to rotate on the scope to allow for adjustment of the camera on the horizon level.

Of course, it should be an apochromatic refractor using ED glass. Unfortunatley, it seems that the term apochromatic is used rather loosely by the entry level scopes. See this article:
http://www.cloudynights.com/item.php?item_id=1498

There are many brands of entry level scopes that qualify and they all come from only a few manufacturers under different names. Interesting brands at the next level are Televue, Stellarvue and Williams Optics.

I have tried stopping down my 100-400 with stacked teleconverters and results were still unacceptable.

 

[vkalia]

Jules,

The straight viewer is also optically corrected (no L/R inversion) - and is also supposed to be optically better per Televue.

And thanks for that info on scopes. I've been checking out the Televue models - the 76mm scope looks quite nice: it isnt substantially bigger than the Vortex 80mm scope I currently have and as per BVD, offers 99% of the performance of the bigger scope.

I prefer angled scopes so was thinking of a 45 degree finder anyway (although I could live with the straight erector, which is optically better). Of course, the question is - how much of the optical performance of these scopes is lost by using that 45 degree finder.

Let me come up with a testing methodology for high-mag photography and I'll post it here for discussion. Give me a day or so.

Regards,
Vandit

 

[JGobeil]

Jules,

I prefer angled scopes so was thinking of a 45 degree finder anyway (although I could live with the straight erector, which is optically better). Of course, the question is - how much of the optical performance of these scopes is lost by using that 45 degree finder.

Vandit

You can get a very nice 45 degree diagonal 2"/1.25" from Williams Optics. From my readings, you shouldn't see any degradation in quality using a good diagonal. Light will be reduced by about 5%, negligeable for birding, and magnification increased by 8%.