Astro Photography

[andy_witkowski]

-Not particular to Canon but I'm using a 40D so here it goes.

 

Im borrowing my friends Meade EXT-70 telescope and have purchase (ordered)

a "Variable Eyepiece Projection Camera Adapter" from

http://www.cncsupplyinc.com/

 

It says it can work both with or without eyepeice.

 

From your experience, is prime focusing preferred over eyepiece projection?

And, what can I expect out of this setup as far as planetary photography is

concerned?

Thanks

-Andy

[matthew_greenwood]

Hi,

 

I have used my 400D (XTi) on my ETX-105 before a few times and find prime focusing gives good results, however even using a 400D i found the weight of the camera was a big strain on the (plastic) gears and needed counter balancing. I think a 40D on an ETX-70 would be even worse (heavier camera, lighter scope) and with it being your friends telescope please be careful!

 

The EXT 70 only has a 350mm focal length so i think decent planetary photography would be out of reach using prime focus (i haven't used one though so would be happy to be corrected). Maybe you'd be better off trying out wide field photography instead (Andromeda galaxy, Orion nebula?).

 

The best eyepiece projection results i have had have been using a compact camera to the eyepiece, although i find this difficult to get any decent results.

 

Although the ETX range are a good telescope, i think they are too lightweight to mount anything heavier than a webcam with out causing problems. Good luck though, its tough getting good astro pics but very rewarding if you do!

[albert_barmettler1]

Hi Andy,

 

The question "is prime focusing preferred over eyepiece projection" ist actually the wrong one.

 

Prime focussing means, you attach the camera directly to the telescope (usually using a T2 adapter), without any other gear in between them (hence the term "prime focus"). Doing so, you are using the scope's focal length (lets say 700mm like a consumer newton telescope, approx. 100.- or 150 Euro's).

 

Using eyepiece projection, there is an eypiece between telescope and the camera. It's purpose is to >>extend<< the focal length of the whole system. Using EPP you'll get equivalent focal length of several meters, depending on the focal length of the telescope, the eyepiece and the distance between camera and eypiece.

 

You wil have to choose... as usual...

 

Prime focus means:

- Higher image quality (because of no eyepiece)

- brighter image (and therefore shorter shutter speed)

 

EPP means: Depending on the eyepiece..

- darker image (due to the focal ratio)

- worse image quality especially at the outer edges

- often only a small area in the center of the image

gets really sharp, because the usual eyepiece is not optimized

for yielding a flat field (they are optimized for the human eye)

 

BUT: EPP allows to pfotograph details (on the moon) at high magnification.

 

So generally speaking: Prime focussing is usually used for "deep sky" images, EPP usually for details of the moon and the planets of our solar system.

 

Im sure the magnification of the system is too low to photograph planets [in a reasnonable size].

 

I recommend to have a look at the astrophotography pages in the internet, usually they describe the settings and used gear. Use this as a starting point!

 

Have fun!

Albert

[andy_witkowski]

Thanks for the information. I hope to try this setup out within the next few weeks and will let you know the results.