[RCC] Help me to improve: My first shoot of M 31 - Forums

Topic starter

Jul 17, 2018 · Edited: Jul 18, 2018

Hi,This is my first shoot of M 31. I think I can do it better, but I’m not sure what to do in order to improve. That’s why I’m here

Here are the details:Subs: 30 (80 seconds)Bias: 30Darks: 30Flats: 30I have a Celestron 8 inch Schmidt Cassegrain, and I don’t use an AutoGuider. My camera is a DSLR Canon 6D

The vignette is so weird. What is happening here? Did I get the Flats right? Do I have to improve my processing skills? Any help will be appreciated.

Thank you

p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 12.0px Helvetica}
p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 12.0px Helvetica; min-height: 14.0px}
p.p3 {margin: 0.0px 0.0px 0.0px 0.0px; line-height: 11.0px; font: 12.0px Helvetica; min-height: 14.0px}

Wim van Berlo

Aug 5, 2018

If your camera has a full frame sensor, the illuminated area that the scope provides may just be too small. In that case, flats can't correct the vignetting, because there is no signal in the corners of the lights and flats. Flats that are unstretched should only show mild vignetting. If the light drop off is large towards the corners, that's a sign that the light cone doesn't cover the sensor. The only way to get flat images is to 1. crop them; 2. use a camera with a smaller sensor; 3. use a telescope with a larger illuminated area (ligth cone).

Helpful Concise

Michael Timm

Aug 5, 2018

Yes, i think wimvb is right. The sensor of the 6D is too big for the C8, especially if you use a reducer like you did. I would suggest to search for smaller targets and dont use the reducer at first for testing. Wimvb suggested all possible solutions i think.

Bradley Hargrave

Aug 6, 2018

I have an APS-C dslr with a celestron c8 sct.
At first, I used the universal t-adapter from celestron (#93625)
This caused serious vignetting similar to what you're experiencing. This adapter cut the light on the edges of the frame due to its diameter being small. Probably less vignetting for me considering i have a cropped sensor.
After further researching, I moved to the Celestron SCT t-adapter(#93633-A)
The vignetting wasn't as noticable and flats were correcting the image much better.

As other have said, I don't think a C8 will ever cover a full frame dslr sensor. If you have the universal adapter, moving to the dedicated sct adapter will help with its larger diameter.

Helpful Respectful Concise Supportive

Deep Sky West (Lloyd)

Aug 6, 2018

What does your image look like before and after DBE? Can you show your DBE model?

Well Written Respectful Engaging

Beck Novaes

Topic starter

Aug 6, 2018

Hi everybody. I just figured out how to fix it. I was not using Debayer process. I've just used and that weird effect on the corners gone away.I really appreciate all feedback here, specially about the sensor size, because I was learning a lot.Thank you all!

Related discussions

Hello from Martinique

Hi, I'm a very new astrophotographer , I just took my first shoot last month and my passion for astronomy is only since less than one year. I'm here to gets constructive critics to improve my photos and my skills. I learned a lot but i know i...

First astrophotographer seeking improvement, similar experience level and goals.

Sep 26, 2017

RCC - First DSO attempt

Hi this is my first go at DSO. My equipment is less than ideal I know but from what I may eventually get something acceptable. I had a hard time focusing. The only thing I knew to do was to view the object through the camera's view finder and it ...

First DSO attempt with equipment constraints, relevant processing and technique discussion.

Dec 15, 2016

[RCC] Looking for feedback on my first SHO narrowband image

I am looking for constructive criticism from the Astrobin community on my image of the N. America and Pelican Nebulae. You can see all the equipment and acquisition details by clicking through to the image below. For processing I used both PixInsight...

Seeking constructive criticism on deep sky object image processing and technique.

Jul 3, 2017