Flats issues

[bottletopburly]

7 hours ago, PadrePeace said:

I too have been wondering about the exposure I'm using for my Flats on an ATIK 460EX mono. Until recently I had been letting the Flats Generator in APT do the leg work with a dim EL panel with a frosted 4mm clear diffuser sheet as the light source. That typically gave me 0.01467s for a Lum 1x1 Flat looking to hit 20,000 ADU which is the Atik recommend full well number. 

I've been told that may be far too short and that some recommend >1sec exposures for Flats. To achieve that I had to put six sheets of good quality A4 white paper under the EL panel. It was so dim I could hardly see the light myself. Whilst that worked for a 1sec Lum Flat my OIII time shot up to 87s which I know is because its NB and 3nm at that but that becomes a 45min exercise to catch 30 Flats.  

Using a technique suggested on the APP sight I had the histogram results posted below:

The first is for a single 1x1 Lum Flat at 0.01467s exp
 
The second for a single 1x1 Lum Flat at 0.205s exp

I went with 0.2s compromise ove the full 1sec as that brings the OIII down to just 12 sec exposure.  Considering the negligible variation and that both are nicely positioned at the 1/3 point with no clipping why should I need to doubt my existing settings (0.01467)? 

Finally, what would you guys recommend for this specific CCD camera as a target Flats exp setting and why?

kind regards

Chris Peace

PS: Just a thought not requiring an answer unless anyone feels so inclined but if I need to get my light source so dim, why are bespoke Astro EPs and light boxes, sold expressly for making Flats, so bright in the first place?

Give Nina flats wizard a shot you don’t need to set it all up , just as a comparison as to what it  exposure it works your flats at ,some flats panels are dimmable though El panels are too bright out the box and need tweaking  Nina tells you if light source is too bright .

[PadrePeace]

6 hours ago, bottletopburly said:

Give Nina flats wizard a shot you don’t need to set it all up , just as a comparison as to what it  exposure it works your flats at ,some flats panels are dimmable though El panels are too bright out the box and need tweaking  Nina tells you if light source is too bright .

I intend to do that today as there seem to be a few variances between programmes. I have found that my shots captured in APT are 1 pixel larger in both axis than subs out of NINA. This was highlighted when I tried to Build mosaic panels shot in the two different programmes and the Bias would not work. 
Thanks for the tip.