Nexstar 6se prime focus question

[deckardbr]

Dear all,

Had a chance to experiment with my setup for the first time a couple of days ago.

Nexstar 6SE -- sct to t ring -- t ring -- Canon EOS Xti rebel

When I centered with my 40mm EP the FOV I get is about 1.3 degrees.

When I take a picture of the same with the canon camera, it looks to me that the FOV got smaller! On the short side, the moon barely fits in, on the long side it fits 1.5 moons. The 1.3 degree FOV usually equals 2.5 moons roughly.

Is this normal for this setup?

What options do I have to expand FOV?

One that I know of is to buy a reducer.

Any advice would be appreciated.

Thanks

Andrea

[michael.h.f.wilkinson]

Assuming a field stop diameter of 34mm for the 40mm EP (based on the size of the FOV), the smaller FOV is simply due to the size of the chip (22.2 x 14.8mm), or 0.848 x 0.565 degrees. A focal reducer can help. That vignettes on 35mm film, but I guess that on APS-C format it should be OK.

[Cornelius Varley]

With a 1500mm fl telescope the moon will just fit onto the sensor of a DSLR. The moon will be approx 13.71mm in diameter (1500/109).

[chrissealuk]

Dear all,

Had a chance to experiment with my setup for the first time a couple of days ago.

Nexstar 6SE -- sct to t ring -- t ring -- Canon EOS Xti rebel

When I centered with my 40mm EP the FOV I get is about 1.3 degrees.

When I take a picture of the same with the canon camera, it looks to me that the FOV got smaller! On the short side, the moon barely fits in, on the long side it fits 1.5 moons. The 1.3 degree FOV usually equals 2.5 moons roughly.

Is this normal for this setup?

What options do I have to expand FOV?

One that I know of is to buy a reducer.

Any advice would be appreciated.

Thanks

Andrea

Hi Andrea, I hope you don't mind me asking but I notice you have a 2 inch diagonal for your 6SE. I have a 6SE & it comes with a 1.25 inch, what benefit does the 2 inch setup give you? I also have a T adapter along with a Canon EOS 550D but I find there is not enough room to insert an eyepiece into the T adapter & then attach it to the camera. Does the two inch setup allow room for the eyepiece?

Thanks, Chris.

[deckardbr]

Hi Chris,

The benefit is limited to be honest. When used in combination with my 2" 40mm WO EP it reaches a maximum FOV of 1.3 degrees. Some great guy on Cloudynight did an experiment and it turns out this this is maximum field of you with the Nexstar 6SE in its basic setup.

I recently bought a Celestron focal reducer, and found that it does a much better job increasing FOV with the added benefit of reducing exposure times when taking pictures. In hindsight, that would have been the better purchase... and my advice to you, unless you already have it.

To insert the EP you need a different type of adapter. This guy is an example:

http://www.scsastro.co.uk/catalogue/orion-universal-camera-adapters.htm

But to be honest... why would you? In the end, I bought a planetary webcam which I use for planets/moon pictures. And use the Canon in prime focus with focal reducer for DSO.

I found it a better option, rather than trying "zooming" in with an EP and then using my canon to take planetary/moon pictures. The webcam is much easier to use... at least to me.

Hope this helps.

Andrea

[chrissealuk]

Thanks Andrea

I think you have talked me into the webcam route for planets. I had already looked at them but wan't sure which way to go. What camera did you decide on?

I think I will buy the Celestron Reducer - Corrector item #94175 too, is this what you use?

Thanks again for your help.

Chris.

[deckardbr]

Hi Chris,

Check out this thread - I asked the same question and people provided a few options. I personally bought:

http://www.modernastronomy.co.uk/camerasPlanetary.html

The last one at the end of the page (£99). There are cheaper and more expensive options... but so far I've been pleased with this one.

And yes, that's the right focal reducer!

Cheers

Andrea

[chrissealuk]

Thanks Andrea, Chris.