[Ben_Edict]

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But IMHO, lens coats are by far more superior than telescope ones?
Although they wouldn’t have as much light gathering power, but in terms of CA, shouldn’t they outperform single lens spotting scope in daylight?
Is that 500mm a cheaper generic brand? (That’s similar to the setup I had in mind)
As for the good quality of the 70-210mm, that is exactly what I wanted but not a permanent fix setup. Whereas an adaptor that can be mount to ANY lens for a quick conversion to a telescope.
If one adaptor is the price of a cheap spotting scope, having it would double the use of your lens collection than just photos, right?

I would say, that in general a telescope is made to much higher specs than a photographic lens, as the primary image of the scope will be magnified massively by the eyepiece. So any decent (I am not necessarily talking about discount store crap...) telescope will easily outperform even a good photographic lens. Coating is just a tiny part of the game. Telescopes usually have very few lenses (and some mirros designs, as the widely used Newtonian) have no lenses at all - thus multi-coating is by far not as important as it is in photographic lenses. On the other hand good scopes have quality coatings, sometimes even multi-coatings, which are either optimized for visual use or for photographic use (the Pentax scopes always had SMC!)

Ben

[Ex Finn.]

Is that 500mm a cheaper generic brand?

Yes, it is a $80.00 piece of junk that I bought, to remind myself, why I needed to spend money for a Vixen 100mm APO refractor.
The statement "similar results can be achieved even with inexpensive gear", is way too general, maybe.
I think that you are better off, by using your gear for what it was intended for.
There could be a reason why lens to 1.25" eyepiece adapters are difficult to locate.
For what it is worth, I had fun piecing together those 2 science projects without spending a penny. Were the results good enough to think about making something permanent, no!.

Cheers, Mike.

[Sean Nelson]

Had anyone seen any adaptor that could convert a K mount lens (not a m42) to a 1.25" eyepiece holder?

If you're still looking for this, then have a look at this thread:

Something not often seen


...which discusses this item on eBay:

Pentax Monocular Converter K - New In Box - Very Rare!

[Douglas_of_Sweden]

I'm a bit surpriced this thread could go on until toay before someone pointed out that the Pentax monocular converter K was the obvious existing solution.



I see them quite regularly on ebay so I don't think they are very rare. I baught mine new from Pentax in the 90's, but don't know if they still make it. Don't pay as much as they ask in that ebay link, I've seen them go for considerably less. Also there are third party copies.

[Ben_Edict]

I'm a bit surpriced this thread could go on until toay before someone pointed out that the Pentax monocular converter K was the obvious existing solution.
I see them quite regularly on ebay so I don't think they are very rare. I baught mine new from Pentax in the 90's, but don't know if they still make it. Don't pay as much as they ask in that ebay link, I've seen them go for considerably less.

No, this is unfortunately not the obvious solution, as it has a fixed eyepiece and cannot be used to adapt ANY 1.25-inch eyepiece to a lens. That is exactly the problem.

Ben

[wildman]

I would saya telescope is made to much higher specs than a photographic lens, as the primary image of the scope will be magnified massively by the eyepiece. So any decent telescope will easily outperform even a good photographic lens.

One shot taken with a $4500 500mm 14 element prime telephoto and the other with a $100 500mm achro doublet asto scope.

[Ben_Edict]

One shot taken with a $4500 500mm 14 element prime telephoto and the other with a $100 500mm achro doublet asto scope.

Very nice examples for comparisson. I can only say, that the cheap scope does a very good job, compared to a lens, 45x as expensive! I would expect some colour on the metal tray, but even that seems to be absent. Thanks for posting.

Ben

[wildman]

Very nice examples for comparisson. I can only say, that the cheap scope does a very good job, compared to a lens, 45x as expensive! I would expect some colour on the metal tray, but even that seems to be absent. Thanks for posting.

Ben

Yes it's very hard to explain in a conventional photography forum the difference in optics between telephotos and scopes.

My APO triplet with FPL-53 glass has resolution to burn compared to even the highest quality conventional prime telephotos. For pure raw optical performance nothing can surpass a high quality triplet at prime focus photographically.

[Ben_Edict]

Yes it's very hard to explain in a conventional photography forum the difference in optics between telephotos and scopes.

My APO triplet with FPL-53 glass has resolution to burn compared to even the highest quality conventional prime telephotos. For pure raw optical performance nothing can surpass a high quality triplet at prime focus photographically.

The only drawback being, that there is no aperture. I even like the Crayford focusers, which are fairly standard on most scopes, more than the helicoids on photo lenses. Crayfords are just faster and quite as good.

Ben

[wildman]

The only drawback being, that there is no aperture. I even like the Crayford focusers, which are fairly standard on most scopes, more than the helicoids on photo lenses. Cray fords are just faster and quite as good.

Ben

Ben,
Aperture:
As a practical matter it does not make as much difference as you might think. When photographing birds you are often shooting under a dark forest canopy or deeply shaded brush. The result is that even if you are shooting with your $10000 f/5.6 800mm Canon where will aperture be set? - wide open or very close to it. Under these conditions, which are common in wildlife photography, your $10000 glass becomes a fixed aperture glass anyway. As a wide open fixed aperture glass a high quality scope has a distinct advantage. After all it is optimized for it's maximum clear aperture unlike a photo lens.

Crayfords:
Crayford's are even faster than you might think under real world conditions. Typically I shot very small fast moving nervous birds. This requires I shoot at a distance of under 40 feet. So the bird may be at 35 feet one moment and 20 feet the next. What I do is set the drag on the crayford very light. Thus a light tug on the camera body and the crayford acts as a very fast draw tube and brings the scope into close focus very quickly while I still can fine focus with the knobs if needed.

Under certain conditions I go even further and add a variable eyepiece projection adapter. This gives me an additional 40mm of focus, if needed, and brings me as close as 10 feet. I can use the additional 40mm of focus or not so it does not interfere with focus at infinity. 10 feet at 15x gives you near macro performance. Try using a conventional telephoto from macro to infinity and still maintain a fast focus throughout the entire range.

My apologies to the OP for getting off topic. I have a cold right now with too much time on my hands.

1 variable eyepiece projection adapter
2. Shot taken using above at about 12 feet

[Ben_Edict]

Ben,
Aperture:
As a practical matter it does not make as much difference as you might think. When photographing birds you are often shooting under a dark forest canopy or deeply shaded brush. The result is that even if you are shooting with your $10000 f/5.6 800mm Canon where will aperture be set? - wide open or very close to it. Under these conditions, which are common in wildlife photography, your $10000 glass becomes a fixed aperture glass anyway. As a wide open fixed aperture glass a high quality scope has a distinct advantage. After all it is optimized for it's maximum clear aperture unlike a photo lens.

Crayfords:
Crayford's are even faster than you might think under real world conditions. Typically I shot very small fast moving nervous birds. This requires I shoot at a distance of under 40 feet. So the bird may be at 35 feet one moment and 20 feet the next. What I do is set the drag on the crayford very light. Thus a light tug on the camera body and the crayford acts as a very fast draw tube and brings the scope into close focus very quickly while I still can fine focus with the knobs if needed.

Under certain conditions I go even further and add a variable eyepiece projection adapter. This gives me an additional 40mm of focus, if needed, and brings me as close as 10 feet. I can use the additional 40mm of focus or not so it does not interfere with focus at infinity. 10 feet at 15x gives you near macro performance. Try using a conventional telephoto from macro to infinity and still maintain a fast focus throughout the entire range.

My apologies to the OP for getting off topic. I have a cold right now with too much time on my hands.

The butterfly is superb. -- I personally find, I get too much flex, if I add any more extension to the crayfords I use, except for some 2-inch sliding tubes, which I got by small manufacturer. These are completely stiff....
There is indeed one lens (system), which combines many of the techniques you describe, the good old Novoflex rapid focusing lenses. You focus by simply pressing a grip and the focusing tube slides forwards/backwards. And they sport integrated variable extension tubes (old modell have a bellows unit to accomplish all that). On top the 3-element optics are very sharp. I have the 400/5.6 and the 600/8, but haven't used these lenses for a long time now - perhaps I should. In many situations, focusing is much faster than any AF systems, especially when shooting wildlife with twigs etc. in the line of sight, which irritates the AF (of all cameras, that's not another Pentax problem...)

Ben