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 Post subject: Telescope for telefoto ?
PostPosted: Wed Jan 07, 2009 11:59 am 
Hi,
Was kind of thinking of trying to catch two flies in one strike....

I'd like to try astrophoto with some kind of beginners equipment.
And i'd like a very very long tele-lens.

I was kind of hoping that it would be possible to buy a telescope (plus equimpent for DSLR photo) that i also could use as a long tele?

Can i do that?


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 Post subject:
PostPosted: Wed Jan 07, 2009 12:57 pm 
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Hi Khol,

It's certainly possible but the biggest drawback is that as telescopes aren't designed to focus at closer objects you'll lose that ability. Also, of course, there's no aperture control available.

If your main use is astro then something like a Meade ETX might fit the bill. You can add a T-Adapter appropriate for your camera. I assume, but please check, that it cold be removed from the mounting and be portable enough to be useful for terrestrial work.

You might also want to search the Net for the term "mirror lens". The issue there would be the potential cost of mounting it for astro use. You might also want to look and see whether any spotting scopes could be pressed into service.

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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 Post subject:
PostPosted: Wed Jan 07, 2009 1:00 pm 
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You certainly can within some limits. For more on the scope I got first see here. I should add more examples of terrestrial photos there...

The question is how long and how fast do you want to go? That will determine the size of the scope. The one I got is a 4 inch Maksutov-Cassegrain design, which gives a small size for the focal length, but do not tend to be very bright. Mine is 1325mm f/13. In the similar type at bigger sizes tend to be Schmidt-Cassegrain types.

You can go bigger and/or cheaper with Newtonian designs, but they are physically very BIG.

In all the above cases, you can get either dedicated adapters for the scope, or a generic eyepiece adapter. Generally both will need a T-ring to suit the camera.

The camera would be operating in manual mode only. You can't vary the aperture so if you ever need less light you will need to add ND filters.

Focus will be manual too. And you will need a very stable platform at longer focal lengths as even small vibrations will cause big movements in the image.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
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 Post subject:
PostPosted: Wed Jan 07, 2009 1:37 pm 
Thanks guys,
Got even more to think about now :)
Never thought about the closest focus-distance, and i'm not sure if (or how) it can be calculated. Dont think i've seen such value in specs either as it probably normally isnt that interesting when buying a telescope.

What i had in mind would something like this scope:
http://www.rymdbutiken.com/index.cfm?fu ... uct_ID=590

And a thing like this:
http://www.rymdbutiken.com/index.cfm?fu ... uct_ID=306

(sorry for the swedish in those links)

And mount the ring at the end of the scope and use it as described.

I have absolutelly no clue if its possible and/or if its a good combination.

I'll also have a look into the gear and stuff you posted. Looks really interesting this astro-photo, and it would be a huge plus if it could be use at relativelly close range as telephoto (wildlife etc).


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 Post subject:
PostPosted: Wed Jan 07, 2009 1:41 pm 
looking up on this...

I have a 20x-60x telescope and one thing to note is the greater you magnify the more the atmosphere gets in the way.

30-40x is a comfortable range for the moon for example, you can get in closer but there is more rippling and hence harder to focus...you'd have to take quicker shutter times

sorry if I am stating the obvious


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 Post subject:
PostPosted: Wed Jan 07, 2009 6:10 pm 
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Khol,

You'll probably need an eyepiece adapter too. The ring goes between the eyepiece adapter and the camera. The eyepiece adapter goes where the eyepiece does on the scope.

Manufacturer's page for that scope is here, but in this case I can't see any details on the minimum focus distance even downloading the manual.

Can't comment on the scope itself without any experience of it or even that type. But the focal length of 1000mm will allow the moon to fill most of the height of an image. At f/11 it could be better, could be worse (mine's f/13!).

I can't think in terms of magnification when used with a camera. It more applies to viewing by eye. Certainly at 1000mm you will be able to see shimmering on the moon's surface, no way of getting around that other than waiting for a clear day (night) or just hoping you get lucky with a lot of shots.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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 Post subject:
PostPosted: Wed Jan 07, 2009 6:58 pm 
Thanks for good feedback in this thread.
I learn alot from you guys.

Hopefully i'll get me a good set of space-gear and get back with some killer-pix :)

We have a wonderful night in sweden tonight with no clouds and a nice atmosphere with a beautiful crisp moon. Really want to snap a few but unfortanently i left my gear at service today. Hopefully i'll get them back soon and in crisp condition.

popo wrote:
or just hoping you get lucky with a lot of shots.


Ohh... well... that is my default mindset anyhow ;)
Hopefully the service i mentioned above will make me a better photographer :)


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