Focusing a camera mounted on a telescope

[trevor_quested]

I have a Kowa TSN-823 telescope and have started using an adaptor for

my Nikon F100 to take bird photos. I received my first roll of film

back and the shots look slightly out of focus. When I am looking

through the camera instead of being clear the view seems a bit

grainy. Can someone tell if they experience the same please?

 

Also I feel the need of a remote control as it is awkward to focus,

work the tripod handle and press the button at the same time. I

checked a few sites for the accessories and there are a number of

remotes to choose from. Any suggestions?

 

I put a question on Photo.net re the unsuitability for me of my 400

5.6 Sigma lens. Privately some people contacted me and said in fact

400mm wasn't quite long enough for bird photography. Now I have the

telescope adaptor I can see what they were getting at. Mind you, the

whole set up is so slow, so far it has been ducks on water, that sort

of thing.

 

 

Trevor Quested

quested@triode.net.au

Sydney, Australia

[bobatkins]

The "grainy" view is a consequence of a slow lens and therefore a dim viewfinder image. It's normal.

 

Are you sure the shots are slightly out of focus. You could be seeing bluring due to lens/camera vibrations, or due to shooting through a lot of air, or due to the limitations of the optics.

 

An 850mm f10.4 lens is going to be difficult to use (as you are finding!). The only way to tell what's at fault is to shoot some test

slides with slight focus bracketing. I presume the F100 doesn't have any form of mirror lock up. If it did, I'd advise you to use it whenever possible.

[vince_farnsworth1]

Unless you are using a *very* stable tripod and cable release, your chances of sharp shots are slim. I am testing some 200 mm lenses at the moment and even those are extremely sensitive to stability. You mention pressing a button. If this is the shutter release, you're already on shaky ground. Use the tripod without full leg extension, collapsed center column and a cable release. For remote focusers, many astronomers use the JMI products. Good luck.

[phil]

The TSN-823 is a fluorite-element spotting scope, so I doubt that the

problem is with the scope in particular.

 

Most *birders* use a lighter tripod than a photographer would for

an 800mm lens. I know I do if I'm just using my scope. Also, since

most scopes aren't all that heavy, there's seems to be less inertial-damping going on with the scope than with my 600mm/4.

(Same tripod, same ball-head, etc) which may add to the problem.

 

My two best guesses would be: need a bigger tripod; need to use

faster film to reduce effects of vibration. Mirror lockup might

help you, but I just bet that the darn thing is waving around in the

breeze.

 

Phil

 

PS. Never overlook the potential of the 400mm Sigma with a decent

1.4x converter. The 560mm/f8 is not all that bad for larger birds

in bright conditions. For passerines it's a stretch, but you can't

scope passerines either.