Troubles with flats - Forums

Topic starter

Apr 17, 2020

Hello,
I am wondering how you guys go round taking flats that works for you.
Since I have switched to Newtonian telescope (TS-8 ONTC f/5), flats aren't calibrating out the dust, and has a minimal effect on flattening out the image.
I aim with SGP to reach 30K or 35k ADU with my Moravian G2-8300, using ledpanel covered with white cloth and placed on the telescope front. Telescope in zenith position. Histogram then reaches a little over half, which worked before with a refractor. Is it essential to reach on third of the Histogram? Could that be the issue?
Any ideas?
I really don't want to through away 40 hours of material

QUOTE QUOTE SELECTED EDIT

Ralph Wilhelm

Apr 17, 2020

Try to make flats with 10-20k. Maybe what you see is non-linearity of the camera.

Pam Whitfield

Apr 23, 2020

I go for 23k which seems to work fairly well. I seem to remember that being recommended as a good target for my QHY9 by the folk at QHYCCD. Having a mechanical shutter complicates things when trying for long-enough exposures with broad-band filters. The professional literature say 5s but I try to make sure I'm over 2s even when I'm in a hurry. That's hard to do but I got a Pegasus Flatmaster that controls precisely and is quite dim as these things go (too dim for narrow-band but I have another panel for those)

Helpful

Guillermo (Guy) Yanez

Jun 17, 2020

In my case, I use a white t-shirt and a white full screen Ipad on top of my refractor pointing straight up as if you were imaging at the zenith (doing otherwise, I would drop the ipad!). Try something similar with your newtonian. I use the sky flats assistant addin for MaximDL (http://winfij.com/maximdl/skyflats.html) at 25k ADU, a minimum of 20 flat frames for each filter and works perfectly well. The integration process is done with DSS. Use whatever software you prefer, it should work.

Helpful