Flat frames?

denababy

Hi, I’ve been struggling getting good flats, I’m sure this is one area that is having a poor effect on my images. I have purchased a light box with variable settings and tried them all. I have tried combinations of white paper, tried a white vest with one thickness then folded over to two three and four but nothing I have tried has worked. My scope is an Explore Scientific and my camera is a 294 mc pro. I play around un The flats I have are anything but flat. The dew shield is slightly drawn out. I try to get the average to around 30.000.
Any one managed to get good flats and how?

Digopak22

denababy I try to keep my flats longer than 3 sec with that camera. >5 usually

ckoos

I use Autorun and select the Flats setting. This defaults the exposure to Auto. I don't have any problems creating flats this way.

WalterT

As Digopak mentioned, the 294 camera models require long exposure flats. I make all of mine 5sec long. Just stick sheets of white printer paper Infront of your lens until you achieve the desired result, it may take 8-10 sheets give it take. Also I find that 50% of the fullwell is excessive I get better results around 17K-22K.

matt s

Hi Walter
I’m reasonably new to using the 294MC Pro, on my CPC925 (F6.3).
I have seen comments along the ‘several seconds for flats’ before. Could you explain why this is the case? I ask as mine are typically around 0.7secs which provides a histogram at ₄₀% and a ‘nice’ image.
Grateful for any tips.
Clear skies
Matt

WalterT

@matt s#55378
"The issue with the IMX294 sensor is that amp glow becomes prominent at exposures below 1 second. A one second exposure has about the same amp glow as a 20 second exposure. Amp glow drops sharply at 1 second and then shows normal growth above the one second mark. For exposures of zero to one second, amp glow ramps up rapidly." - by jdupton, 02 April 2021 CloudyNights

ps. I also should mention that you should combine the longer exposure flats with darks and flat darks, no biases.

matt s

WalterT
Hi Walter
Thanks for the tips. Two more Qs, if I may?

Does amp glow reveal itself on the flat; and
Do you know if DSS can combine flats with dark flats etc?
Thanks again
M

astronebulee

Hi
I use an a4 light panel in a DIY box holder with a few sheets of paper on the screen of the light panel and set manual exposures to 2 secs and have had no issues with my 294MC pro. The histogram hump on my asiair pro is generally just before halfway with I find perfect.
Cheers
Lee

WalterT

@matt s#55393 #1 I'm no expert but I'm going to say "Yes." That is the purpose of the flat darks, in order to subtract the amp glow in the flats that would not be present on a typical short exposure flat from camera sensors that are not affected by this problem.
#2 Yes. I use DSS to stack my images.

matt s

WalterT
Hi Walter
Thanks for the explanation-much appreciated. Looks like I’ll be tweaking my approach to taking calibration frames!
Clear skies
Matt