QSI 6120 Flats adu level

[mikeyj1]

Hi all, 

I have been trying to get flats using the 6120 and LRGB filters, but struggling to find an exposure, it's either ridiculously short for 20,000 adu (approaching bias frame speed!), or far too long (8-10sec) for 33,000, which is the 'default' in SGP.  i seem to only be able to get a max of around 31,000 adu even with a multi second exposure, into a relatively bright source. I have a stretched t shirt as my diffuser

What should i be aiming for, and does the binning level make a difference on the max level?

thanks

Mike

[RayD]

46 minutes ago, mikeyj1 said:

Hi all, 

I have been trying to get flats using the 6120 and LRGB filters, but struggling to find an exposure, it's either ridiculously short for 20,000 adu (approaching bias frame speed!), or far too long (8-10sec) for 33,000, which is the 'default' in SGP.  i seem to only be able to get a max of around 31,000 adu even with a multi second exposure, into a relatively bright source. I have a stretched t shirt as my diffuser

What should i be aiming for, and does the binning level make a difference on the max level?

thanks

Mike

When I take my flats with my Sony sensored cameras I pretty much have the flat panel light off for the RGB filters.  They are very sensitive and I only increase the lighting levels to high when taking Ha flats (3nm).  Try them agianst just a white board or wall with only background lighting.

I aim for a time of around 2 seconds, and adjust the lighting level to achieve this.

Increasing the binning will reduce the time needed for the same ADU level, but only use that if your lights are binned also.

Not sure what the exact ADU level would be on your particualr camera as I believe the QSI6120 has slecetable gain, so on low gain it is around 50,000 ADU, so you would aim for around 20,000 - 25,000 ADU.

Edited May 1, 2020 by RayD

[mikeyj1]

thanks Ray,

I'm still wondering if the ADU max level  will change if I Bin 2x2 compared to 1x1?  

in any case i will aim for around 20k and 2 secs or less for the LRGB.

I will experiment some more tonight hopefully, looks like it may be clearing...!

cheers

Mike

 

[Star101]

My method is to take flats at different exposure settings until I see the Vignetting and dust motes stand out. Once I get them as prominent as possible. I note the exposure settings and the ADU reading and use that.

 

 

[MarkAR]

I've been using Ekos which can calibrate flats on the fly, seems to work well.

I also found out that if you have binned your lights then you have to match the binning of the flats, darks and bias.

Edited May 4, 2020 by MarkAR

[RayD]

21 hours ago, mikeyj1 said:

thanks Ray,

I'm still wondering if the ADU max level  will change if I Bin 2x2 compared to 1x1?  

in any case i will aim for around 20k and 2 secs or less for the LRGB.

I will experiment some more tonight hopefully, looks like it may be clearing...!

cheers

Mike

 

No the ADU max level shouldn't change as the full well depth doesn't change. What it will mean is as you are now aggregating 4 pixels (at 2x2) the amount of time needed to reach the same ADU will reduce.

If you bin your lights you will also need to bin your flats to match. 

Edited May 5, 2020 by RayD