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View Full Version here: : Back focus with my DSLR and SCT with reducer


evltoy
11-06-2021, 01:43 PM
Hello All,

I hope everyone is keeping well :)

As some may know, I have been battling with getting the right back focus distance with the introduction of a x.63 Celestron Corrector/reducer on my 8" SCT. Last night I was able to sneak in 2hrs of testing while the skies were somewhat clear.

Here is what I did.
1) Using my Alt/AZM mount align etc..
2) Using a Bahtinov mask, get the right focus on a bright start
3) Slew to NGC104 and took the best 30sec exposure
4) Change distance down by 5mm
5) repeat steps 2-4

The only thing I didnt do is frame up the target like for like. Should I have done this?

Anyways I have attached the single shot images for review. If you have the time please have a look and tell me which image feels right or getting close to perfect.

The setup is a Celectron 8" SCT with Celestron .63 Corrector/reducer, 2" rings to a Nikon D600 (using DX mode).

Cheers
Wayne

AdamJL
14-06-2021, 01:54 PM
Hi Wayne

I would say the two sharpest are these:

http://www.iceinspace.com.au/forum/attachment_browse.php?a=276409
http://www.iceinspace.com.au/forum/attachment_browse.php?a=276410

hard to choose between those two.

evltoy
15-06-2021, 03:41 PM
Hey Adam,

Thanks for taking out the time to look & comment. I appreciate you helping me out.

I too picked one you did
https://www.iceinspace.com.au/forum/attachment_browse.php?a=276410

But I went the other way on my second
https://www.iceinspace.com.au/forum/attachment_browse.php?a=276411

My main focus was trying to find the most roundest stars on the outer sections of the image.

Cheers
Wayne