NGC 7822 and FUNKY FLATS

[ultranova]

Hi Every one,

Managed to get out for 4 hours on Saturday,

which gave me the opportunity to try out the ZWO EAF.

which was a first for me, the last 40 years I have been focusing manually and was 

very hesitant at letting something else do it.

worry unjustified as it worked a charm.

It was also a first using the optolong L-extreme filter for a longer session with the ZWO294mc pro

Anyway here's my take on it and the Flats that I can not use when staking,

As it makes processing  of the image near on impossible.

Would be interesting to here from any one else with a similar problem using 

that camera filter combination.

 

here is the master flat, never had a problem like this before with flats 

thanks for looking, 

clear sky's

Paul

[vlaiv]

Question is - why is your master flat debayered?

Calibration files should be left as they are and applied before any possible debayering.

Also - check histogram of linear master flat and ADU values. Do you have any clipping?

Filter that you are using aggressively cuts off light and there is a chance green channel is void from data. If you have offset set incorrectly that will cause clipping to the left on histogram.

If you have any sort of automatic flat generation - software might be confused by lack of proper peaks and can over expose red - which would lead to clipping on the right of histogram.

[Luke Newbould]

Hi,

I had a very similar issue calibrating l-enhance data from a 294mc Pro, I found flats were only usable when the light source was significantly dimmed and the flat exposures were around 2+ seconds each.

https://www.cloudynights.com/topic/661685-word-of-warning-asi294mc-pro-and-opt-triad-and-nb/

 

A related thread here, if you scroll around half way down the page you'll see cuivenior's posts with images highlighting the almost exact same issue, it seems its a pattern only visible in the deep reds, and the origin is the sensor itself.

 

Hope that helps, don't be discouraged as I found that once I knew what was going on I could work well with the camera!

[ultranova]

Hi Valaiv,

I only debayed and and auto streched the image  in pix insight to show the strange colors coming through the filter,

not my normal routine for sure.

I don't have clipping, i thought that might be the case,  

and there does appear to be green data coming through, actually to much,

Here is a auto streched image of the master light frames debayered .

 

 

I don't have problem with flats normally,  but you could be onto something about the  flat generation,

I normally do my flat around the 19000, to 24000 range , I needed around 26000 for this image according to the figures

i was using,  which at the time of processing did seen very high.

I think i will have another look, as you say something could be causing the flat range to be way off,

The strange one for me is the colour shift over the flat..

 

 

 

 

 

 

 

 

 

 

 

[ultranova]

18 minutes ago, Luke Newbould said:

Hi,

I had a very similar issue calibrating l-enhance data from a 294mc Pro, I found flats were only usable when the light source was significantly dimmed and the flat exposures were around 2+ seconds each.

https://www.cloudynights.com/topic/661685-word-of-warning-asi294mc-pro-and-opt-triad-and-nb/

 

A related thread here, if you scroll around half way down the page you'll see cuivenior's posts with images highlighting the almost exact same issue, it seems its a pattern only visible in the deep reds, and the origin is the sensor itself.

 

Hope that helps, don't be discouraged as I found that once I knew what was going on I could work well with the camera!

Thanks for that, as i say it has only been with that filter, 

I didnt have any issues with optolong  l -enhance,, which is similar, in its design,, but obviously 

this filter is a lot tighter on it spectral bandwidth and pre dominantly only supposed to let in two channels 

unlike the L-enhance.

Thanks for the links and help, i will re visit my flats  and see what occurs.

Paul