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Old Oct 4, 2002, 10:00 AM   #11
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I've been using the CP 4500 since late August with my Leica APO Televid and a 32WW eyepiece. The CP is no weight, the carbon fibre tripod is ok and the Leica is great exercise since the physio recommended the new back exercises. It's the weight factor that is the only thing that has made me consider a future swap to Swarovski, as I'm very happy with the Leica scope quality in conjunction with the CP.

I use the EagleEye adapter with this set-up and I've found, similar to Lin's comment, that I can remove the rubber eyering from the 32WW and reduce (but not eliminate) the vignetting. The 32WW strikes me as being a good birding - digiscoping compromise eyepiece for the Leica (I'll duck at this point !) but I must admit that I've reservations about the CP zoom. I'm now tending to photograph and then crop any vignetting, but due to the exit pupil size of the eyepiece I find that without careful re-adjustment of the adapter things can get rapidly out of line.

But whatever the set-up, not even the best gear can counter excessive vibration. One of the best pieces of advice I've had from this site is "don't extend the central pillar of your tripod". I've found that it makes all the difference between an acceptably crisp shot and............

By the way, do people tend to have one permanently set up eyepiece for digiscoping and another for birding ? I'd value some advice.
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Old Oct 5, 2002, 1:58 AM   #12
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Default Scope Eyepiece

I have an almost identical set up to you Graham, except I use the 885 and have got some good results. The question of eyepieces is interesting because I am a birder first and a digiscoper 2nd. I have both the 32WW and the 20-60 zoom and for general birding I prefer the 32WW, so I tend to take photos with that. However, for photography I think the zoom gives greater flexibility so I end up carrying both around. What's a few extra gms!

I agree with your comments on stability - it's been very windy all summer here and vibration has been a real problem.
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Old Oct 5, 2002, 3:12 AM   #13
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Default Digiscoping eyepiece

I have the 30xwwa and 20-60x zoom, fortunately I prefer the zoom for general birding as well as digiscoping..... at 20x it lets in a lot of light for fast shutter-speeds. 30x (or just over) is the ideal mag to be using with a 77mm+ scope, resolving the optimum amount of detail that is available to the scope. There is absolutely no difference in optical quality between the Swaro' 30x wwa and the 20-60x zoom @ 30x.... this may not be the case with all manufacturers.
My own opinion is that digiscoping is secondary to birding, so you should be using the e.p. that you prefer to use with the naked eye... but it all depends on your priorities.
I sometimes use as much as 50x on some shots....not resolving more detail than 30x but enabling the bird to fill the frame to get more accurate exposure for the subject.
On the cp4500 I rarely go above 3x (f4.2ish).
Stability can also be improved by lowering the tripod to it's minimum working height (just above the ground if you have adjustable leg angles + splittable centre column). Another popular method is the stonebag or any heavy object attached to the centre column.
Andy B,
London
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Old Oct 18, 2002, 2:35 AM   #14
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I'm new to this group and relatively new to digiscoping. I've been at it about two months now. My experience has been entirely with variations on Maksutov type scopes (except for a few shots through binoculars). There are two things I'd like to address that Lin made in his (her? - sorry - can't tell for sure from the name) initial post.

While it is true that the mirror portion of a scope such as a C5 or ETX-90 cannot introduce chromatic aberrations, it is not true that the scope is immune to chromatic aberrations. This is because these scopes are Catadioptric - meaning they use both a lens and mirrors. The lens is a key element in Mak-Cassegrains and Schmidt-Cassegrains in that they correct for the spherical distortion introduced by the main spherical lens. These lenses or corrector plates do not do bend the light severly like an objective lens would. However, as glass lenses they can introduce chromatic aberrations. Furthermore, these scopes use standard eyepieces. These eyepieces typically use spherical surfaced lens elements. Yet another place chromatic aberration can occur.

I guarantee you that my inexpensive 14x40 LOMO Captain has serious chromatic aberration. My LOMO Asltele 95 exhibits very little such distortion, and I think what little it does exhibit is probably from the eyepiece. So while I suspect it is easier to get low or near non-existent chromatic aberration from a spotting scope that uses a mirror, it is wrong to assume that the use of a mirror means the scope will be free of such distortions.

My second point is that I find the long focal length of my 95mm LOMO to be more of a hinderance than a help. Most digiscoping occurs at effective magnifications of 20-30X. Beyond 30X, most scopes cannot add appreciable detail. Large mirror scopes like the C5 can, but even they can't out to 35mm equivalent focal lengths of 6000mm. For the C5, 40X or about a 3000mm equivalent is where the scope can no longer add detail - and this assumes top notch optics that are diffraction limited. The 1200mm focal length of my scope is a hinderance because it significantly limits the usable eyepieces for digiscoping to between 50mm and perhaps 25mm. You will find most people with mirror scopes like these use a 40mm objective (30X). I'm using a 50mm surplus binocular eyepiece.

So, I like mirror scopes and think they are a great value. They generally will create superb images and the better ones are very low in chromatic aberration or are essentially apochromatic. But I think Lin has overstated their advantages in these two areas a little bit.
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Old Oct 28, 2002, 11:42 AM   #15
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Jay is correct that a low quality eyepiece can and will introduce chromatic aberration, even when used with a high quality mirror, however my assumption is that for digiscoping with a quality spotting scope, the user will use an eyepiece of equivalent quality.

With such combinations, I've not seen chromatic aberration beyond that introduced by my camera's lenses at all with a C5 or ETX-90. I use either William Optics DCL-28 or ScopeTronix eyepieces with all my spotting scopes and Nikon cameras. With inexpensive terrestrial type spotting scopes, I've seen significant chromatic aberration added to that produced by the camera itself - so in theory, I agree with Jay, but in practice I disagree. If you purchase a quality astro-spotting scope and use a quality APO type eyepiece, you will not experience any additional chromatic aberration beyond that contributed by the camera's internal lens system.

Focal length considerations depend greatly on your camera and eyepiece choices. Personally, I like the 1250mm focal length of the Meade ETX-90 for birding. Coupled with the DCL-28 William Optics(24mm eyepiece) eyepiece, at 3x zoom on a CP990 one gets 5989mm which is about the limits of usable focal length in good lighting conditions. With the CP995 or CP4500, an eyepiece like the wide angle ScopeTronix 18mm will render a range of approximately 2639mm to 10,763mm. Obviously, one will never use the full 4x zoom with this small an eyepiece, but since there is nearly full zoom range with no vignetting, the usable focal length range is excellent. With the 3x cameras this same eyepiece/scope combination yields about 2639mm to 7986mm. With the William Optics 24mm eyepiece, the range is respectively 1979mm to 5989 or 1979mm to 8073mm.

Since I use the same eyepieces with my Swarovski (focal length 462mm) I get excellent value from just two eyepieces. By using eyepieces which allow nearly full zoom range without vignetting, I can avoid using my zoom eyepiece with the Swarovski and still cover nearly the same usable range of focal lengths.

Jay is correct that additional detail is not added beyond around 30x, but using longer focal lengths allows framing the subject without cropping and enlarging, which has it's own benefit when printing in that it minimizes The amount of interpolation required.

The important thing is to find a combination which works best for you. What works well for one may not be suitable for another. When all other factors are equal, shorter focal length tubes have greater light gathering potential, and this may be even more important for certain shooting conditions.

There are numerous possibilities, but do choose a scope which has excellent light gathering capability and sufficient quality in construction to allow field use for birding. The mirror types definitely represent a bargain when compared to similar optical quality in a terrestrial spotting scope. Obviously they are not as rugged and waterproof, but for use in good weather they are quite capable and inexpensive.

Best regards,

Lin (it's a "He" rather than a "She") :-)
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