×

INDI Library v2.0.6 is Released (02 Feb 2024)

Bi-monthly release with minor bug fixes and improvements

Advice on Flats with Canon DSLR

  • Posts: 79
  • Thank you received: 13
I am trying to work out the best way to take flats with my Canon 450D Astro Modified. I have tried just using AV mode to get the exposure and then using it in EKOS but flats seem slightly over exposed at 1/125, ie .008 secs.
So I wanted to try the calibration routing in the EKOS camera module based on a more accurate ADU.
EKOS calibration only works with FTS files not the Canon raw CR2. So I get EKOS to capture in that. The ADU target I use is 7500 based on a search of forums . So I put that into the calibration setting and start with .008 secs and it ends up at .029 secs .
Can I just transfer that value when taking CR2 Flats? Or as I will be using DSS for stacking am I better off using FTS flats (can I mix CR2, lights, Darks with FTS flats?)

My Flat illumination is an LCD panel on my shed observatory wall, plus I also stretch a white cloth over the lens to increase diffusion.

Or am I doing it all wrong?

Any advice much appreciated.
5 years 2 months ago #34083

Please Log in or Create an account to join the conversation.

  • Posts: 1957
  • Thank you received: 420
When taking flats with a DSLR you need to make sure that the exposure time is longer than about 1 second. The reason is the mirror flipping up and down and when the exposure times are too short then you'll get flats that are affected by the mirror flip. This will introduce a slight shadow on one side of the flats rendering them useless. In order to be able to increase the exposure time you can make use of a white t-shirt.

For more info, see

photographingspace.com/how-to-create-dsl...or-astrophotography/

I always make flats that way and they work great. I just take an image and inspect the histogram. This needs to be more or less at the center. Many people claim it needs to be at 40% (i.e. slightly to the left of center) or 60% (i.e. slightly at the right of center) but in my experience anywhere between 20% and 80% will work fine. Too far left and they will be too dark with some pixels not having any data. Too far right and some pixels will be saturated.


HTH, Wouter
The following user(s) said Thank You: Max Dobres
5 years 2 months ago #34085

Please Log in or Create an account to join the conversation.

Time to create page: 0.156 seconds