There is a lattice striped

@mo-mo That's hard to say with only a screenshot. Do you see this as well if you don't use the bias and darks?

@wvreeven Thank you immediately

I calibrated without using BIAS and Dark (using Flat and Darkflat). Critical warning came out during the process, but continued to process. The lattice is not visible, but column is clearly displayed.

@mo-mo Can you check the master dark and master bias to verify that the colunms are visible in those as well? Were the master dark and master bias created in APP?

@wvreeven Hello

Yes, there are columns in both master dark and master bias. These were created in the APP.

@mo-mo I suppose that such strong cold columns may be difficult to get rid of, even with proper darks and bias. Do you apply dithering during imaging and, if yes, how much? If not then I would suggest to do so using 20 or even 30 pixels in the imaging train and to make sure that dithering is done after each exposure.

@wvreeven 

I would like to return to my first question, but does the lattice -like shadow can't be solved?

Sorry, I don't understand what to do.

@wvreeven Hello

Columns were solved because those became less noticeable. Instead, a lattice -like pattern is a problem, but is there a solution?

Thank you for your usual kind advice.

Hi momo, so this is a tricky issue I see. Just to summarize to make it clear for me as well:

- You use flat frames that are calibrated with the bias, yes?

- You get the columns/grid in the end result after calibration, yes?

If so, what happens when you process without using any calibration data?

@vincent-mod Hello

First, let me answer your question.

- You use flat frames that are calibrated with the bias, yes? YES

- You get the columns/grid in the end result after calibration, yes?

YES but not colorized

-If so, what happens when you process without using any calibration data?

The grid will disappear, but the columns will appear clearly.

I used Flat and Darkflat without BIAS and Dark. Let me know if you want to know the result if you don't use all the calibration data. I will check.

The O3 image of the lattice has an exposure time of 900 seconds. I have an O3 with an exposure time of 300 seconds, but no grid. The difference between the two is the camera and telescope as well as the exposure time. Where is the cause of the lattice?

columns? camera? calibration data?
Both the grid image and the previous image were obtained using a telescope subscription service.If you think the calibration data is the cause, I would like to consult with the service provider.

Thank you.

Hi momo,

So I also talked to Mabula and he mentions it is likely an issue many old CCD camera's have. Darks for these are very important and should have a complete match with the lights (temperature, exposure, gain and offset), can you find out if that is indeed the case? I know that many telescope providers seem to struggle a bit with calibration data. You also have to dither (big steps) and the hot/cold column kappa can be reduced from 8 to 6 or even 4.

So if you can verify the above and try out even stronger kappa values, that would be interesting to know. If you still see issues, you may have to dither even more. Old CCD sensors are quite notorious for this.

@vincent-mod 

Thank you for answer.

For the first time, I learned for the first time that an old CCD camera is more likely to cause problems. I'm glad I understand that. If possible, can you check the calibration data?

I would be happy if you could do so.

Thank you for your kindness.

Sure, you can upload it to your own folder with name "mo-mo-calibrationData"

@vincent-mod 

I uploaded the file. Please check the condition. Thank you.

Thanks! Let me get to it, please allow for 2 days.

Hello

Is there any updated information about the uploaded file?

Thank you

Not yet, apologies, I have time tomorrow to have a detailed look.

Ok, I got this OIII result with just the darks:

I already got a warning in the end that 100 pixels were clipping (I'm doing this with our internal beta5 which has a higher cutoff for showing this issue). This is not very bad, but it does point to either the OIII exposure not being long enough still or a slight issue with the dark. When the dark is substracted, these 100 pixels turn black, which means the dark's signal is a bit too high. I'm not seeing the lattice though.

When I started to look at the flats and bias, I noticed their resolution was half (2048x2048 instead of 4096x4096), so APP is not using those at all. Could you try again with flats/bias of the correct resolution?

@vincent-mod 

Thank you for answer.

The camera is 2x2 Binned.
Do you cause a problem if the resolution of BIAS and Flat is different from Light?
I didn't care about the difference in resolution so far, but is the different resolution a problem in principle?

Can APP adjust the resolution difference?

No, APP needs the same resolution for all frames.

@vincent-mod 

hello
I understand.
I will ask the provider to get it.

Thank you

Hello

Telescope Subscription Service provided 4096*4096 resolution flat,bias. I have included the results of my calibration using them.
There are dark areas at the top and bottom of the image. According to the service provider, the dark areas are shadows of the OAG. And they say the following as the reason why the shadow is not corrected by the calibration.

looking at the Jpeg you have sent you are getting an under correction of your flats. The two dark patches you are seeing is the shadow of the OAG, you can see two the field being rotated 180 degrees during the aligning of the frames.. Although P8 is a fork mount it can swap the orientation of the frame due to which ever side of the meridian it decides to image from night to night .
This can be remedied by adding a pedestal value when creating your Master flat, It is also very important to remove the Bias from your darks and flats when creating your Masters.

It says "adding a pedestal value when creating your Master flat", can APP do this?