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adrian tyler
30-Jul-2009, 23:03
to complete a project i would like to make some pictures from the top of the sierra nevada looking down into granada. however none of my long lenses are going to work as they don't have sufficient magnification. i have been looking at the "Leica APO-TELEVID 82 angled telescope with VARIO 20 - 50x WW ASPH ocular"

http://www.company7.com/leica/telescopes/apotelevid82.html

if there is anyone who knows the focal length equivelant in 35mm format of this optic i'd be grateful...

thanks

adrian

Struan Gray
30-Jul-2009, 23:56
Those are sexy scopes.

The total magnification of a telescope is the focal length of the main optic divided by the focal length of the eyepiece. In this case, 440 mm divided by 8.8-17.6, which roughly works out as 25-50 x (hence the name of the eyepiece :-).

Roughly speaking, for a given format, its normal lens gives 1x magnification at infinity. Multiply other magnifications by the normal focal length to get an effective focal length. So, for 35 mm film, assuming a 'normal lens' is 50 mm, the equivalent focal length of the Leica scope is 1250-2500 mm. Use appropriate factors if your camera is a non full-frame digital.

Hearsay has it that the dedicated camera adapters for these scope (http://www.company7.com/leica/televcam.html) give better results that photographing through an eyepiece made for viewing, but then you are limited to a single focal length, 800 mm. It all depends on how pernickerty you want to be: astro photographers are generally unhappy with the results from even these exalted terrestrial scopes.

adrian tyler
31-Jul-2009, 01:54
thanks struan i appreciate it !

they do look good don't they, pretty un-versatile but it may be my best solution if i can swing the budget, also after looking through the "brought to light: photography of the invisible" SFMOMA catalogue there are a possiblity of other applications which could provide hours of fun!

it'd be interesting to see the difference between photographs made through the eyepiece viewer and the dedicated adaptor.

i suppose astro photograhers need more magnification?

Struan Gray
31-Jul-2009, 02:49
The biggest problem is that telescopes are usually optimised for on-axis performance, and even the relatively small area of a digicam sensor gets you far enough off-axis that the aberrations turn ugly. When looking through a telescope with your eyes, their adaptation covers errors which can make a photograph look horrible, and you tend to be more indulgent to centred compositions and things like colour fringes at the edge of the field.

You will need a beefier support than the usual sorts of tripods used by birdwatchers. In fact, support and air quality between you and the town will be your biggest headaches.

You might also want to look into local options for renting the big sports glass by Canon and Nikon. The APO wunderskops from Zeiss and Leica have quite good reputations as telephoto replacements when compared to other spotting scopes, but I've never seen anyone suggest they compete with the dedicated long lenses, even once you have to crop and interpolate the images taken with the telephoto lens.

PS: if you want to do things 'right', here's some telescope porn:

http://www.takahashi-europe.com/en/products.refractors.php

Archphoto
31-Jul-2009, 04:05
There is a crude way of finding out the lengh you want: take a picture of the area you want with your longest lens and enlarge the full frame of it to say 40x50, deterimine the size of the area you realy want and start calculating.

Original hight of the print at ...mm /new hight of the area choosen = your factor k
...mm x k = new/needed focal lengh

For 35mm a mirror lens with extender (focal lengh converter) could do the trick, for 4x5 you would need a Sinar P2 with multiple bellows and inbetween standards and a bit more....

You allso need quiet air as has been said, a sturdy tripod and expect a loss of contrast if you are phtographing an object miles away.

Peter

jp
31-Jul-2009, 05:35
There is a crude way of finding out the lengh you want: take a picture of the area you want with your longest lens and enlarge the full frame of it to say 40x50, deterimine the size of the area you realy want and start calculating.

Original hight of the print at ...mm /new hight of the area choosen = your factor k
...mm x k = new/needed focal lengh

For 35mm a mirror lens with extender (focal lengh converter) could do the trick, for 4x5 you would need a Sinar P2 with multiple bellows and inbetween standards and a bit more....

You allso need quiet air as has been said, a sturdy tripod and expect a loss of contrast if you are phtographing an object miles away.

Peter

I've used a cheap russian mirror lens + teleconverter (2000mm) on a 35mm dslr for these sort of shots. In addition to these reqiurements, you'll also want a darkcloth, as they aren't that bright for focusing. The distance compression is uncanny.

You can get almost as good results shooting with a high quality tele lens (300 2.8) and digital zooming/cropping in post processing if you've got a decent camera sensor.

GPS
31-Jul-2009, 05:56
Adrian, are you speaking 35mm photography or LF photography?

Peter K
31-Jul-2009, 07:13
Adrian, are you speaking 35mm photography or LF photography?
That's no difference if one uses the telescope mounted in the way the exit pupil of the telescope meets the entrance pupil of the camera's standard lens, focussed at infinity.

In this case the telescope is an afocal device and the subject is, in Adrian's case magnified 20 - 50x compared with the standard lens.

This is also the case with other afocal devices like microscopes, dove turn-over prisms, fisheye converters etc.

Peter

Drew Wiley
31-Jul-2009, 09:15
A real expert at adapting cameras to telescopes is a fellow here in the SF Bay area
named Francis Sakamoto. Originally he adapted Nikon and Pentax 6x7 cameras for
Celestron telescopes, but now he uses a 8x10 Toyo view camera with a long bellows,
puts Apo-Nikkor graphics lenses on the front, and a 6x7 camera at the film position.
Has a website.

Glenn Thoreson
31-Jul-2009, 10:39
Be advised that atmospheric haze is greatly enhanced using ultra long lenses. Something to consider.

GPS
31-Jul-2009, 10:45
That's no difference if one uses the telescope mounted in the way the exit pupil of the telescope meets the entrance pupil of the camera's standard lens, focussed at infinity.

In this case the telescope is an afocal device and the subject is, in Adrian's case magnified 20 - 50x compared with the standard lens.

This is also the case with other afocal devices like microscopes, dove turn-over prisms, fisheye converters etc.

Peter

Sure, I know it. I want to know if he intends to attach a LF camera to the scope or just a 35mm camera. Makes a great mechanical difference.

Donald Miller
31-Jul-2009, 12:36
Sure, I know it. I want to know if he intends to attach a LF camera to the scope or just a 35mm camera. Makes a great mechanical difference.

Excuse me but I have some questions. I own a Celestron 6" Schmidt Cassegrain telescope. How in the world would someone mount a LF camera to that and expect that they are going to cover a sheet of film? I specifically asked about that at one time and the tech people told me that telescopes would not cover anything more than a 35 mm film. So considering that what would it benefit to project that image on a sheet of film as opposed to a 35 mm negative or a sensor?

If you are going to project the telescopes image circle onto the entrance pupil of a camera taking lens, how in the world would one hold that contraption in registration? Now I could see where one could mount a 35 mm DSLR to the scope and do stitching to arrive at some pretty incredible images. My scope (using the rule of 60) would have an optimal magnification of 360. The focal length is either 1250 mm or 1500 (I can't remember which offhand).

The reason I ask is that I probably have everything to bring this together other than the mechanism to mate the telescope to the camera.

GPS
31-Jul-2009, 12:47
It would not cover. I never said so...

Dan Fromm
31-Jul-2009, 14:24
As long as the thread is drifting a little, why not a Televue refractor instead of a Leica?

GPS
31-Jul-2009, 14:37
...

The reason I ask is that I probably have everything to bring this together other than the mechanism to mate the telescope to the camera.

That was the reason of my original question too. The mechanical problems would be huge. Beside the fact that 35mm camera problems belong to the lounge...:)

Darren Kruger
31-Jul-2009, 14:42
If you are going to project the telescopes image circle onto the entrance pupil of a camera taking lens, how in the world would one hold that contraption in registration?

The reason I ask is that I probably have everything to bring this together other than the mechanism to mate the telescope to the camera.

Not sure on your telescope or camera, but I have hooked up a spotting scope to my old Pentax K1000 using a T-mount adapter. in effect it makes the scope into the taking lens. I've been thinking of getting a Pentax dSLR with shake reduction in the camera and play around with my scope again.

-Darren

Peter K
31-Jul-2009, 15:35
If you are going to project the telescopes image circle onto the entrance pupil of a camera taking lens, how in the world would one hold that contraption in registration?
How do you think Karl Schwarzschild 1897 has found with this telescope (http://upload.wikimedia.org/wikipedia/commons/6/67/Refraktor_Wien_Kerschbaum_1.jpg) Bunsen-Rocoe's law i x t = s isn't true with long exposures? A LF-camera was mounted behind the telescope's eyepiece.

Peter

GPS
31-Jul-2009, 16:32
How do you think Karl Schwarzschild 1897 has found with this telescope (http://upload.wikimedia.org/wikipedia/commons/6/67/Refraktor_Wien_Kerschbaum_1.jpg) Bunsen-Rocoe's law i x t = s isn't true with long exposures? A LF-camera was mounted behind the telescope's eyepiece.

Peter

Come on Peter, that's not a serious answer. Donald is right, you cannot just put a LF lens in front of an eyepiece of his Celestron telescope and go for LF afocal photography. The problem he would face is called vignetting...:) I think you know why...:)

Donald Miller
31-Jul-2009, 17:39
Not sure on your telescope or camera, but I have hooked up a spotting scope to my old Pentax K1000 using a T-mount adapter. in effect it makes the scope into the taking lens. I've been thinking of getting a Pentax dSLR with shake reduction in the camera and play around with my scope again.

-Darren

There is no problem mounting a dslr to a telescope provided one can find the adapter. I found this site and they seem to have a fairly good number of cameras covered. It looks like for $40 I can hook my 5D to my Celestron. I may need to give this a go for something new to try.

I found this link to be interesting because of the effects of camera temperature as it relates to image noise.

http://ghonis2.ho8.com/rebelmod450d16c.html

Best regards,
Donald Miller

Peter K
1-Aug-2009, 02:38
The problem he would face is called vignetting...:) I think you know why...:)
Why vignetting? The exit pupil of a telescope like the celestron f/10, focal-lenght 2000mm and entrance pupil 200mm, is in the area of 5 to 7mm. And the entrance pupil of a LF-lens f/8 150mm for an 4x5" camera is 18,75mm. So the rays from the telescope leave the telescope's eyepiece parallel and if the LF-camera without telescope is focussed at infinity the image produced by the telescope with eyepiece fills the whole 4x5".

Of course if the mechanical problems to mount the camera are solved.

Peter

GPS
1-Aug-2009, 06:38
Why vignetting? The exit pupil of a telescope like the celestron f/10, focal-lenght 2000mm and entrance pupil 200mm, is in the area of 5 to 7mm. And the entrance pupil of a LF-lens f/8 150mm for an 4x5" camera is 18,75mm. So the rays from the telescope leave the telescope's eyepiece parallel and if the LF-camera without telescope is focussed at infinity the image produced by the telescope with eyepiece fills the whole 4x5".

Of course if the mechanical problems to mount the camera are solved.

Peter

Unfortunately Peter, the things are much more complicated in the afocal photography than you see it. I mistakingly took you for someone who knew it...
In the afocal photography, the vignetting depends on many factors, such as the eyepiece eye relief, the position of the diaphragm of the taking lens in relation to the exit pupil of the eyepiece, the film format, the focal length of the camera lens etc.
If you want to study it more I suggest you see the easy but good book of "Astrophotography for amateurs" by Michael A. Covington. Cheers!

Peter K
1-Aug-2009, 11:59
GPS, thanks for your correction. I've started with the assumption an, often used, eyepiece with 17mm eye relief. Together with a "normal" camera lens - no Tele or WA - in use. With such a lens one has some degree of freedom. And no vignetting if the camera lens aperture is wide open.

Peter

Joseph O'Neil
2-Aug-2009, 07:44
Attaching a DSLR to any telescope (1.25" or 2 inch focuser) is extremely easy. All you need is a T-ring, (about $20), then either 1.25" or 2" adaptor (another $15 to $40) and in some cases, and extention tube ($30 to $60). When possible, 2" adpators are best for full coverage.

For wider coverage , Takahashi Petvals can cover 120 film (seen it in person first hand) and I suspect you can try them on 4x5 sheet film with spome decent luck. You might not have full coverage, you you could get a nice image.

Most of the time, I do not see actual 4x5 or other large format cameras attached tot he back of a telescope, rather, you see 4x5 backs attached to telescopes - all sizes of telescope.

In fact, two weeks ago I was touring the 72 inch David Dunlop observatory north of Toronto, and it used ot use 4x5" glass plates. Kodak stopped producing thier specialty films for astronomical use - oh, around the mid 1990s, if memory serves more correct. The plates and films had special spectral response,a nd had names like 103a, etc.

The camera at the DDO north of Toronto used liquid air (nitrogen I think - but I stand ot be corrected) for extreme cooling during exposures, but the other way to do it was bake the glass plates, and in some cases, gas hypering. I still have my gas hyerping setup, while tech pan was always used gas hypered, it works on all films.

so it isn't all that hard, your major issue, IMO, is lack of image coverage. If you are happy with a small image circle on the centre of a sheet of film, it can be done. One last thought, to hold the film steady for long term or time exposures, Linhof holders were always prized.

joe

adrian tyler
2-Aug-2009, 11:20
thanks for all the interesting replies, it woud seem a shame to spend a lot of money on a tesescope and no be able to do astronomical work with it so it looks like i have to do a bit of reading...

"GPS" well both 35mm & LF are of interest but LF was certainly not in mind when i made the post, so yes, smack bottom and banished to the lounge.

Dan: thanks for the tip to the Televue refractors. Struan: thanks for the oriental "porn" make me sweat looking at the price list...

adrian

Tim Povlick
4-Aug-2009, 21:10
A good APO telescope makes a nice camera lens, although a very small FOV. If shooting with camera attached to scope directly looking at the objective then one needs a field flattener (FF) to cover 35mm to 6x7 size. Attached are two images taken with two different APOs. The smaller sign (right) was taken with a 480mm f/l scope at f/6, but no FF. The field curvature in the full size image is very apparent (this is a tiny crop). The sign post is about 3 inches tall and about 120 feet distant.

First (left) image is with a 152mm APO (1200mm f/l) with FF. Both scopes and the FF were designed by the late Thomas Back, optical genius. Yours truly did the mechanical design (with great help from "my" machinist Ross) of the FF.
The sign is about 200 feet distant and taken with a 6x7 PentaxII. The FF made full FOV in perfect focus. The biggest problem to really sharp images is the daytime turbulence. Had I taken this image about 2 hours earlier it would be sharper.

Tim

adrian tyler
4-Aug-2009, 23:12
A good APO telescope makes a nice camera lens, although a very small FOV. If shooting with camera attached to scope directly looking at the objective then one needs a field flattener (FF) to cover 35mm to 6x7 size. Attached are two images taken with two different APOs. The smaller sign (right) was taken with a 480mm f/l scope at f/6, but no FF. The field curvature in the full size image is very apparent (this is a tiny crop). The sign post is about 3 inches tall and about 120 feet distant.

First (left) image is with a 152mm APO (1200mm f/l) with FF. Both scopes and the FF were designed by the late Thomas Back, optical genius. Yours truly did the mechanical design (with great help from "my" machinist Ross) of the FF.
The sign is about 200 feet distant and taken with a 6x7 PentaxII. The FF made full FOV in perfect focus. The biggest problem to really sharp images is the daytime turbulence. Had I taken this image about 2 hours earlier it would be sharper.

Tim


hi tim, they both look very sharp which is encoraging, what is a "field flattener?"

thanks

Tim Povlick
5-Aug-2009, 06:48
hi tim, they both look very sharp which is encoraging, what is a "field flattener?"

thanks

Hi Adrian,

A field flattener is a multi-element (2 to 4) optic placed close to the focus plane (placement is typically critical +/- 1mm). It flattens the curved focus plane of a typical refractor telescope. The diameter must be large enough to not vignette; for the 6x7 this required a 93mm lens followed by an 88mm lens. When focusing the FF must move with the camera, hence the focuser has to deal with the weight of the camera and FF.

If you check the bottom of this page:

http://www.ccdware.com/products/ccdinspector/examples.cfm

you can see the effect of without / with the FF. The images are mapping the Petzval surface (plane of focus). I believe some of the old Schmidt cameras (telescopes) had film holders that bent the film to match the curvature of the focus plane.

Best Regards,
Tim