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 momo
(@mo-mo)
Red Giant Customer
Joined: 1 year ago
Posts: 121
Topic starter  

Hello

O3 images were calibrated with Bias, Dark, Darkflat, Flat. There is a lattice striped, but is it a calibration failure? Since cold column kappa and hot column kappa are both 8.0 because CCD cameras have Column. The same goes for 7.0.

I will attach an image, but can you see a lattice striped?

APP Version 1.083.4

CCD camera FLI PL-16803 Mono CCD - 2x2 Binned

Thank you in advance.

squid p12 Both column8 St
This topic was modified 2 months ago 2 times by momo

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(@wvreeven)
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Joined: 4 years ago
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@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?


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 momo
(@mo-mo)
Red Giant Customer
Joined: 1 year ago
Posts: 121
Topic starter  

@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.

squid O3 p12 NoDarkNobias 3 St
criticalwarning
This post was modified 2 months ago by momo

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(@wvreeven)
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@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?


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 momo
(@mo-mo)
Red Giant Customer
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Posts: 121
Topic starter  

@wvreeven Hello

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


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(@wvreeven)
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@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.


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 momo
(@mo-mo)
Red Giant Customer
Joined: 1 year ago
Posts: 121
Topic starter  

@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.


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 momo
(@mo-mo)
Red Giant Customer
Joined: 1 year ago
Posts: 121
Topic starter  

@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.


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(@vincent-mod)
Universe Admin
Joined: 5 years ago
Posts: 5130
 

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?


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 momo
(@mo-mo)
Red Giant Customer
Joined: 1 year ago
Posts: 121
Topic starter  

@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.


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(@vincent-mod)
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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.


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 momo
(@mo-mo)
Red Giant Customer
Joined: 1 year ago
Posts: 121
Topic starter  

@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.

 


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(@vincent-mod)
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Sure, you can upload it to your own folder with name "mo-mo-calibrationData"


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 momo
(@mo-mo)
Red Giant Customer
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Posts: 121
Topic starter  

@vincent-mod 

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


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(@vincent-mod)
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Joined: 5 years ago
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Thanks! Let me get to it, please allow for 2 days.


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 momo
(@mo-mo)
Red Giant Customer
Joined: 1 year ago
Posts: 121
Topic starter  

Hello

Is there any updated information about the uploaded file?

Thank you


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(@vincent-mod)
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Not yet, apologies, I have time tomorrow to have a detailed look.


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(@vincent-mod)
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Ok, I got this OIII result with just the darks:

image

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?

 


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 momo
(@mo-mo)
Red Giant Customer
Joined: 1 year ago
Posts: 121
Topic starter  

@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?


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(@vincent-mod)
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No, APP needs the same resolution for all frames.


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