Optolyth 100 for digiscoping? (1 Viewer)

Hi Forum!

This is my first post here.

So far, I have been digiscoping with an old Kowa TS-1 and a home-made achromatic eye-piece. It works fine but the chromatic abberrations from the scope's objective and prisms are very disturbing so I am considering to upgrade the scope.

I have been searching the web and this forum for info on digiscoping with an Optolyth 100 TBS APO but have not really found any opinions on that for this purpose.

Does anyone here have any experience? I am in particular interested in knowing about vignetting with different eyepieces since I am using an Olymus C5050 digital camera that has a larger diameter lens than the conventional CoolPix 9XX cameras.

Also, another question: How do you post a review of equipment? I have a brand new Nikon 10x42 SE CF that I could review for others to read.

With best regards, Jens.

Hello Jens - welcome to BF.

To add a review, go to the review section and click on "upload products" - I look forward to reading your review of the Nikon.

I have no experience of the Optolyth scope but it is a high quality optic - the best advice is to put your camera up to the eyepiece and see what happens! You are bound to get some vignetting and will need to use your camera's zoom to reduce this to a minimum, but the 100mm objective will ensure a good bright image that should allow a decent exposure speed / aperture combination.

jebir said:

Hi Forum!

This is my first post here.

So far, I have been digiscoping with an old Kowa TS-1 and a home-made achromatic eye-piece. It works fine but the chromatic abberrations from the scope's objective and prisms are very disturbing so I am considering to upgrade the scope.

I have been searching the web and this forum for info on digiscoping with an Optolyth 100 TBS APO but have not really found any opinions on that for this purpose.

Does anyone here have any experience? I am in particular interested in knowing about vignetting with different eyepieces since I am using an Olymus C5050 digital camera that has a larger diameter lens than the conventional CoolPix 9XX cameras.

Also, another question: How do you post a review of equipment? I have a brand new Nikon 10x42 SE CF that I could review for others to read.

With best regards, Jens.

Click to expand...

There are 2 parts to creating a review. First you must create a product description assuming one does not already exist. This contains the specs and a few pictures. Then you create a review for the product.

Click on the "Reviews" manu item at the top of the page. Then scroll down and click on the "Large binoculars" category. You will see a list of products, but with no entry for the Nikon 10x42 SE. So you will have to create an entry. Click on "Upload products". Then enter information for the product (but NOT the review- just the specs). When you have done click on the Upload button at the bottom of the page.

Now you can enter a review for that product. From the list of products, select the product you have added, and then when it appears, click on "Add reply". Enter your review.

jebir said:

I have been searching the web and this forum for info on digiscoping with an Optolyth 100 TBS APO but have not really found any opinions on that for this purpose.

Does anyone here have any experience? I am in particular interested in knowing about vignetting with different eyepieces since I am using an Olymus C5050 digital camera that has a larger diameter lens than the conventional CoolPix 9XX cameras.
.

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concerning Vignetting while Digiscoping
try this interesting page from Jay Turberville:
http://www.jayandwanda.com/digiscope/vignette/vignetting.html
One of his findings is that long eye relief may be more important than the diameter of the eyepiece.

general optolyth tests:
http://www.kikkertspesialisten.no/pdf/testtele.pdf
http://www.betterviewdesired.com/Optolyth_TGB_100.html

gorank said:

concerning Vignetting while Digiscoping
try this interesting page from Jay Turberville:
http://www.jayandwanda.com/digiscope/vignette/vignetting.html
One of his findings is that long eye relief may be more important than the diameter of the eyepiece.

general optolyth tests:
http://www.kikkertspesialisten.no/pdf/testtele.pdf
http://www.betterviewdesired.com/Optolyth_TGB_100.html

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Thanks Gorank,

Very interesting links - all of them!

Cheers, Jens.

gorank said:

http://www.jayandwanda.com/digiscope/vignette/vignetting.html
One of his findings is that long eye relief may be more important than the diameter of the eyepiece.

Click to expand...

The eye relief requirements for "standard" Coolpix cameras is fairly well known, but there is little info on the C5050. But the C5060 apparently has requirements very similar to the typical Coolpixes. I just don't know about the C5050's requirements though. Getting good information about camera eye relief requirements is not easy without testing for yourself. But I have found two additional clues since I wrote that article that may be helpful in sorting out candidate cameras.

1) The "nodal point" that is used by folks taking panoramic photos is actually the lens' entrance pupil. If you have good info on this "nodal point", you can compare it to the "nodal point" for the standard Coolpix line and make some decent estimates about what the camera's eye relief requirements are.

2) I've seen the entrance pupil defined as, "the image of the aperture stop formed by that part of the system preceding it in the optical train." In other words, if you look into the front of your camera you can actually see the entrance pupil. If you do this with a CP5000 and zoom the lens, you will see some mild back and forth movement, but it amounts to a few millimeters. And the iris seems fairly close to the front elements of the lens. But if you do this witht he CP5400 - known for its need for a great deal of eye relief - you will see that the iris is seemingly sucked into the deep recesses of the camera lens as the lens is zoomed. Of course, you can't make a measurement of this distance, but this kind of analysis should help you eliminate obviously poor camera candidates. If your C5050 displays such behaviour, then you will probably have a tough time or have a very limited range that will digiscope well.

In the end, the best options are a cooperative camera store that will allow you do do some basic testing in the store or the direct experience of others with the same gear.

Jay Turberville said:

The eye relief requirements for "standard" Coolpix cameras is fairly well known, but there is little info on the C5050. <snip>
1) The "nodal point" that is used by folks taking panoramic photos is actually the lens' entrance pupil. If you have good info on this "nodal point", you can compare it to the "nodal point" for the standard Coolpix line and make some decent estimates about what the camera's eye relief requirements are.

2) I've seen the entrance pupil defined as, "the image of the aperture stop formed by that part of the system preceding it in the optical train." In other words, if you look into the front of your camera you can actually see the entrance pupil. If you do this with a CP5000 and zoom the lens, you will see some mild back and forth movement, but it amounts to a few millimeters. And the iris seems fairly close to the front elements of the lens. But if you do this witht he CP5400 - known for its need for a great deal of eye relief - you will see that the iris is seemingly sucked into the deep recesses of the camera lens as the lens is zoomed. Of course, you can't make a measurement of this distance, but this kind of analysis should help you eliminate obviously poor camera candidates. If your C5050 displays such behaviour, then you will probably have a tough time or have a very limited range that will digiscope well.

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Jay,

thanks a lot for these important pieces of information.

Let me report my findings for others to note:
1) the C5050 behaves like the CP5400 with respect to the diafragm movement.
2) From panorama photo considerations, I know the distances for the nodal points at the extremes of the zoom range measured from the tripod mount. Converted to distances from the objective lens surface which is useful for digiscoping the distances are:
at 7 mm FL (35 mm equiv): 25.1 mm
at 21 mm FL (105 mm equiv): 53.8 mm
3) The original 60 mm Kowa TS-1 25x eyepiece has only 10 mm eye relief which explains why I couldn't use it for digiscoping with the C5050 without getting severe vignetting.
4) My homemade eyepiece, which has an eye relief of 50 mm but only half the magnification, works fine for full field images through the TS-1

Since I am considering the Optolyt 100 scope, I will now try to figure out if I can use it with the C5050 or if I can use the homemade eyepiece. I'll report back my findings.

Cheers, Jens.

It is worth noting that while it is ideal to have the camera's entrance pupil coincide with the eyepiece's exit pupil, it is not strictly necessary. Deviations result in limitation of the scope's FOV. But considering that a 105mm equivalent zoom setting on a camera only has about a 24 degree FOV and that most scope eyepiece have at least 40 degrees to offer(and often over 60 degrees), some limitation can often be tolerated since the longer zoom setting can't "see" the full FOV anyway. This is probably at least partly the reason that some cameras are useful over a relatively large camera zoom range.

Unfortunately, I don't know of any good way to quantify how much FOV is lost as you move away from ideal pupil location.

jebir said:

3) The original 60 mm Kowa TS-1 25x eyepiece has only 10 mm eye relief which explains why I couldn't use it for digiscoping with the C5050 without getting severe vignetting.
4) My homemade eyepiece, which has an eye relief of 50 mm but only half the magnification, works fine for full field images through the TS-1

Since I am considering the Optolyt 100 scope, I will now try to figure out if I can use it with the C5050 or if I can use the homemade eyepiece. I'll report back my findings.

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Hi Jens,
I have copied the following info about Optolyth eyepieces from a Dutch scope test page (not the one that was discussed on the forum recently), which itself I could not find any longer.

Fixed
30x: 12 mm
45x: 11 mm

20-60x zoom
20x: 12.5 mm
30x: 10.5
40x: 11
50x: 12.5
60x: 15

Looks like the Optolyth eyepieces are not quite as "digiscoping-friendly" - in terms of eye-relief - as the ones from Swarovski, Zeiss or Leica, but slightly better than Kowa (which too has been used for digiscoping with great success, see eg. IanF's gallery). You may be able to bring the camera 1-3 mm closer using a steady bracket-type adapter instead of the tube systems. I am afraid that in digiscoping you may still lose some field-of-view because of vignetting, but in normal viewing the big Optolyth APO is really impressive.
Good luck,

Ilkka

Eye reliefs of Optolyth:

iporali said:

Fixed
30x: 12 mm
45x: 11 mm

20-60x zoom
20x: 12.5 mm
30x: 10.5
40x: 11
50x: 12.5
60x: 15

Looks like the Optolyth eyepieces are not quite as "digiscoping-friendly"

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Thanks for these numbers Ilkka, I have been searching the web for them without success. -You are right, not so digiscoping friendly but I will test the scope tomorrow and we will see then.

You may be able to bring the camera 1-3 mm closer using a steady bracket-type adapter instead of the tube systems.

Click to expand...

Actually, the tube system can be trimmed to place the camera wherever you want (within the limits of the tube lengthst).

...but in normal viewing the big Optolyth APO is really impressive.
Good luck,

Ilkka

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Thanks Ilkka!

Now that I have become spoilt with a very nice pair of binos, I am REALLY looking forward to have a look through that scope in dawn or dusk!

Cheers, Jens.

jebir said:

Actually, the tube system can be trimmed to place the camera wherever you want (within the limits of the tube lengthst).

Click to expand...

Oh yes - I was fixated with the CP4500's filter threads and internal zooming. :t:

Ilkka

Hi all,

I tried the Optolyth 100 APO and as expected, I recieved severe vignetting with my Olympus C5050, with the fixed 45x as well as the 30-60x zoom (old design) eyepieces, for all combinations of scope/camera zooms.

This makes sense when I put all pieces of information together:
1) The eye relief of the scope should coincide with the entrance pupil of the camera
2) The eye relief of the Optolyth is about 11-12 mm at useful magnifications
3) The entrance pupil of the C5050 is at ~25 mm at wide-angle and at ~54 mm at full zoom.
4) The apparent FOV must be larger than the camera's FOV

So, at full zoom, the vignetting is due to the eye-relief/entrance pupil mismatch and as I zoom out with the camera, the mismatch decreases but at some point, the FOV of the camera exceeds the AFOV of the scope.

These two pieces of equipment simply do not mate well!

However, the view through the scope was so fantastic so I could not resist buying it anyway. After all, digidcoping has a smaller priority than watching the birds.

Now the very good news: When I came home, I tested the homemade eye-piece that I have made for my old Kowa TS-1. It gives a SUPERB match between the camera and the scope! I can even zoom out a bit and it doesn't seem like it reduces the amount of light into the camera by any large amount either. The latter, I think is a combination of relatively low magnification of the eye-piece and very large scope objective diameter.

So, I am now modifying the homebuilt eyepiece to fit the Optolyth scope. I'll share the first bird-pics with you when it is ready.

When I get more time, I will make a comparison of the various combinations for these two scopes and the five different eyepieces for everyone in this forum to see.

Thanks for all your help! Without your input, I wouldn't have understood how these things should be in order to be useful for digiscoping.

Cheers, Jens.

Brilliant news, Jens. When you find a scope that suits, you are in birding heaven, that's for sure. Let's hope plenty of your feathered friends find their way into its field of view, eh?

jebir said:

Now the very good news: When I came home, I tested the homemade eye-piece that I have made for my old Kowa TS-1. It gives a SUPERB match between the camera and the scope! I can even zoom out a bit and it doesn't seem like it reduces the amount of light into the camera by any large amount either. The latter, I think is a combination of relatively low magnification of the eye-piece and very large scope objective diameter.
Cheers, Jens.

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Sounds great. I'm very curious about the design of your homemade eyepiece.

The exit pupil of the Olpolyth with your homemade eyepiece is probably larger than the diameter of your camera's iris. This would be why you don't see much change in brightness as you zoom out with the camera. What little you do see is probably from the camera f-number itself changing. At 12.5x and a 100mm objective, the exit pupil is 8mm. That's pretty big.

jebir said:

I tried the Optolyth 100 APO and as expected, I recieved severe vignetting with my Olympus C5050, with the fixed 45x as well as the 30-60x zoom (old design) eyepieces, for all combinations of scope/camera zooms.
<snip>
So, I am now modifying the homebuilt eyepiece to fit the Optolyth scope. I'll share the first bird-pics with you when it is ready.

Click to expand...

Hi again.

I am now finished rebuilding the adapter tube for my long eye-relief eyepiece that allows for digiscoping with my C5050. I promised some of the first pictures. Here are a few. The Yellow wagtails are from this Thursday. They are cropped to about 50-75% of the initial area. The hare is from this morning and is hardly cropped at all. I am very pleased with the combination of equipment that I have gathered now.

Cheers, Jens.

Whew - that hare is superb. Well done.

Jens,

I have recently been trying to use a c5050 with my Swarovski ATS 65HD scope with the 20-60 eyepiece, and I, too, have been getting severe vignetting. Your post with the info on the entrance pupil explains why. Many thanks for that! But now I am curious about your references to your homebuilt eyepiece. I wouldn't know the first thing about building an eyepiece and am probably not capable of such a feat even with excellent instruction, but I would still be interested to know how you do that. Any guidance you can offer will be greatly appreciated. Thanks.

George

Hi George,

I made the eyepiece from an old Sigma Zoom-Maseter 35-70mm SLR zoom lens. That lens is built up around an 'achromatic triplet' which is an optical device that has extremely good colour correcting and imaging properties and at the same time acts as a relatively strong magnifier. What differentiates this from ordinary eye-pieces is the long eye-relief.

I (and many others) have bought second hand Sigma Zoom-Master 35-70
mm lenses and dis-assembled them to get out the triplet. It can then
be mounted in front of the C5050 lens to produce macros like this one:
http://myolympus.org/document.php?id=405 and it can be used as an eye-piece for digiscoping (see my gallery for numerous examples with Optolyth APO 100 and Kowa TS-1.)

In order to use it for digiscoping, I mounted the triplet on an adapter tube that I had a good friend help me do in aluminium. However, I also used PVC drain pipe tubes that I could modify at home when experimenting with the length etc in the beginning.

Once attached to the scope, you can just hold the camera to the eye-piece and get a decent image if it is bright enough. However, I also made a simple attachment by combining one Olympus CLA-1 and one Raynox 5241 extensiontube (see this thread for some images: http://www.birdforum.net/showthread.php?t=14774&highlight=eyepiece ).

I hope that helps a little!

Cheers, Jens.

jonege said:

Jens,

I have recently been trying to use a c5050 with my Swarovski ATS 65HD scope with the 20-60 eyepiece, and I, too, have been getting severe vignetting. Your post with the info on the entrance pupil explains why. Many thanks for that! But now I am curious about your references to your homebuilt eyepiece. I wouldn't know the first thing about building an eyepiece and am probably not capable of such a feat even with excellent instruction, but I would still be interested to know how you do that. Any guidance you can offer will be greatly appreciated. Thanks.

George

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