Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Do I need a coma corrector for the C8?

Astrophotography Equipment Filters Imaging SCT
  • Please log in to reply
6 replies to this topic

#1 Aman Dude

Aman Dude

    Vostok 1

  • -----
  • topic starter
  • Posts: 153
  • Joined: 13 Sep 2021
  • Loc: U.S.A.

Posted 25 May 2024 - 06:02 PM

I am using a ZWO ASI533MC for imaging with the C8, but the back focus is too far off due to my OAG needing spacers for proper focus. Should I use my Celestron 0.63x corrector? Or does it not impact it that much for this camera sensor size?

 

Thanks,

Asher



#2 acrh2

acrh2

    Mercury-Atlas

  • *****
  • Posts: 2,826
  • Joined: 16 Mar 2021

Posted 25 May 2024 - 07:01 PM

I am using a ZWO ASI533MC for imaging with the C8, but the back focus is too far off due to my OAG needing spacers for proper focus. Should I use my Celestron 0.63x corrector? Or does it not impact it that much for this camera sensor size?

 

Thanks,

Asher

 

That depends on what an acceptable star shape is to you. 

Here are images from C8 with and without various coma correctors. The diagonal in the images is 26.8 mm, ASI533 has a diagonal of 16 mm.

 

It took me 10 seconds to Google it.

 

https://stargazerslo...corrector-test/

 

The reducer will also make images 2.5 times brighter, improving the SNR by 60%.


Edited by acrh2, 25 May 2024 - 07:06 PM.


#3 pedxing

pedxing

    Gemini

  • *****
  • Posts: 3,123
  • Joined: 03 Nov 2009
  • Loc: SE Alaska

Posted 25 May 2024 - 08:23 PM

The celestron reducer is not a corrector. The Starizona reducer is a corrector and works pretty well.

I would say try your celestron reducer and see how it goes, the smaller sensor of the 533 might give you a "good enough" field.

You never know until you try...

#4 DirtyRod

DirtyRod

    Surveyor 1

  • *****
  • Posts: 1,993
  • Joined: 23 Mar 2021
  • Loc: Arizona

Posted 25 May 2024 - 08:28 PM

What’s preventing you from getting to the proper backfocus? I use a 533, as well as other cameras, with an Edge-8 and an OAG and have no issues getting to 133mm without the reducer and 105mm with it. I know plenty of folks using the standard C8 and an OAG and can get to the right backfocus.



#5 acrh2

acrh2

    Mercury-Atlas

  • *****
  • Posts: 2,826
  • Joined: 16 Mar 2021

Posted 25 May 2024 - 09:49 PM

The celestron reducer is not a corrector. 

 

What gave you that idea?



#6 RedLionNJ

RedLionNJ

    Cosmos

  • *****
  • Moderators
  • Posts: 8,681
  • Joined: 29 Dec 2009
  • Loc: Red Lion, NJ, USA

Posted 25 May 2024 - 10:11 PM

What gave you that idea?

Agreed!  Celestron describe it as a "Unique focal reducer and field corrector lens accessory"



#7 pedxing

pedxing

    Gemini

  • *****
  • Posts: 3,123
  • Joined: 03 Nov 2009
  • Loc: SE Alaska

Posted 26 May 2024 - 03:17 PM

Agreed! Celestron describe it as a "Unique focal reducer and field corrector lens accessory"

Marketing hype from the folks who sell the c8/avx combo as an imaging system.

Do you have an example sub from a C8 with that reducer that is well-corrected?


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics




Also tagged with one or more of these keywords: Astrophotography, Equipment, Filters, Imaging, SCT



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics