10" Dob + DSLR field of view

[Rahul Zota]

Hi all,

I am thinking to buy the adapter to fix my DSLR camera on a focuser of my 10" Dobsonian telescope. The question is what field of view (FOV) would I get? My purpose is wide-field photography. The camera I am using is Canon EOS 550D and the focal length of my telescope is 1200mm.

[Ags]

The field of view is inversely proportional to the focal length. 50mm to 400mm might be regarded as wide field, but 1200mm would give a very small field.

To calculate the actual field, multiply the width of the camera sensor by 57.3 and divide by the focal length. Working roughly in my head, i would say that would give you a field of approx one degree with a regular DSLR.

[Merlin66]

You can use Ron's CCDCalc software to illustrate the various FOV with different scopes and cameras....

The New CCD Astronomy Home Page

HTH

[JohnC]

And another link

Field of View Calculator | Sky at Night Magazine

[Rahul Zota]

Thanks to all for satisfying replies. The online calculator is very useful

[JimStan]

You would be much better suited for wide-field photography by just employing the regular lens that came with your camera, and allowing the camera to "ride" on a "piggyback adapter" mounted to your normal OTA. A telephoto up to around 200mm will allow you to narrow in on a constellation, and some very nice photos of the Milky Way etc. have been taken with lenses with as short a FL as 18 mm !

If you don't have a motorized mount to put your camera on, you might want to investigate a device called "the barn-door tracker". These can be constructed with normal materials such as threaded rod, piano hinges, some pieces of wood, etc. The only specialized items you will need include a "ball socket" for holding the camera and lens. You can find many ideas on the web.

Good luck!

Jim S.

[Rahul Zota]

Thanks Jim,

I was planning for bar dor tracking but it requires some mathematical skills and high accuracy. I know one guy in India who has build such tracking mount and I am going to take some help from him. Also my future plans are to buy a Sky-Watcher 102mm short-tube refractor with HEQ5 or EQ6 mounts. I think this will be helpful for DSLR comet hunting!