calibration (dark,Flat & Bias

Image processing, astrometry, photometry, etc.
Astrognosis
Posts: 14
Joined: 07 Oct 2019, 22:08

calibration (dark,Flat & Bias

Post by Astrognosis » 24 May 2023, 13:25

I'm new to Astroart8. My familiarity with similar software is MaxIm Ver 6.14 and the sky X with which I've found calibration of images fairly simple.

1. Can I create master darks, flats etc that I could load and use for calibration instead of load say the 20 + images taken for each (akin to MaxIM)

2. I have created images using Astroart8 and calibration images with The Sky X and finally used MaxIm to create master frames to calibrate the astroart images again using MaxIm, but reports that no calibration images found?? Yes a bit of a convoluted route, but what I'm used to (MaxIm DL) for calibration seems easier. I would expect this should have worked, any solutions?

Many thanks,

Eric

Dunmunro
Posts: 230
Joined: 10 Jan 2019, 01:11

Re: calibration (dark,Flat & Bias

Post by Dunmunro » 24 May 2023, 22:00

Astrognosis wrote:
24 May 2023, 13:25
I'm new to Astroart8. My familiarity with similar software is MaxIm Ver 6.14 and the sky X with which I've found calibration of images fairly simple.

1. Can I create master darks, flats etc that I could load and use for calibration instead of load say the 20 + images taken for each (akin to MaxIM)

2. I have created images using Astroart8 and calibration images with The Sky X and finally used MaxIm to create master frames to calibrate the astroart images again using MaxIm, but reports that no calibration images found?? Yes a bit of a convoluted route, but what I'm used to (MaxIm DL) for calibration seems easier. I would expect this should have worked, any solutions?

Many thanks,

Eric
AA8 creates master darks and flats during Preprocessing:

Tools->Preprocessing->Files

and you have the option to save and reuse them:

Tools->Preprocessing->Options->options

Astrognosis
Posts: 14
Joined: 07 Oct 2019, 22:08

Re: calibration (dark,Flat & Bias

Post by Astrognosis » 25 May 2023, 02:23

Dunmunro
thanks for pointing me in the right direction.

Emm not as straight forward as I had hoped.

Eric

fabdev
Posts: 477
Joined: 03 Dec 2018, 21:43

Re: calibration (dark,Flat & Bias

Post by fabdev » 25 May 2023, 14:44

Hi,

1) Yes and it's recommended. However using Master dark frames and flat fields is just a speed optimization, which will save 4-5 seconds for every process. Before doing that, verify that the results you are getting are already correct. Then, a Master file can be created "manually" placing dark frames into the Images box, or "automatically" during a real calibration, with the option "Show master dark frame and flat field". In both cases, save it manually after the process.

2) Maybe I'm wrong, but I remember that some software can be set to recognize dark frames and flat fields automatically, using some FITS keywords or naming convention. If you acquired them with another software this could be the cause.

Fabio.

Astrognosis
Posts: 14
Joined: 07 Oct 2019, 22:08

Re: calibration (dark,Flat & Bias

Post by Astrognosis » 25 May 2023, 21:40

Fabio,

Re point 1 i am finding in difficult to follow the instructions given in the manual and tutorial. I can load up the images, flats, darks etc into the pre-processing, but it's what to do next and how to proceed?

your comments re point 2 seem to ring a bell with me so I shall look into this further. Though it would be good to get everything under one roof.

The sub-frame fix you did for me works thanks.

I very much like the focusing procedure, once one finds an approximate focus manually the auto focus works a dream and getting to a good focus in less than a minute tops all other software I have tried. When I get the frame calibrations working for this will me this would then make AA8 my telescope control and image taking my software of choice.

Any step by step approach would be very much appreciated.

Eric

fabdev
Posts: 477
Joined: 03 Dec 2018, 21:43

Re: calibration (dark,Flat & Bias

Post by fabdev » 25 May 2023, 22:34

I suggest to test incrementally:

1) Add your images to the "Images" box, verify that no options are active and press OK. You should get a result image with trailed stars and noise.

2) Enable auto-alignment in the "Options", press OK, the stars should now be round, but noise will be still visible.

3) Add the dark frames to the "Dark frames" box, press OK, noise should be gone.

4) If it works, 70% of the procedure is complete.

Astrognosis
Posts: 14
Joined: 07 Oct 2019, 22:08

Re: calibration (dark,Flat & Bias

Post by Astrognosis » 25 May 2023, 23:43

Fabio,

I have successfully followed these instructions and have the single image with noise much reduced, but the flat faults showing. What would be the next steps?

Cheers, Eric

fabdev
Posts: 477
Joined: 03 Dec 2018, 21:43

Re: calibration (dark,Flat & Bias

Post by fabdev » 26 May 2023, 17:50

5) Add the Flat fields into the "Flat fields" box and the Biases into the "F. Dark frame" box (the "dark frames of the flat fields". On modern cameras you may use biases for them).
Correcting the Flat fields with their "dark frames" is mandatory for a proper division.

Astrognosis
Posts: 14
Joined: 07 Oct 2019, 22:08

Re: calibration (dark,Flat & Bias

Post by Astrognosis » 26 May 2023, 19:59

Fabio,

I have now additionally done the flat field (inc the dark flats) correction and have a single corrected displayed. So i guess I now save this image. Which again I guess would be the 11 stacked corrected image. ?

Suppose I wanted to calibrate the the II images individually. I suppose this could be done 1 image at a time, bit of a long process there must be a shorter way?
Also how would I create a master frame of each Dark,dark Flat, Flat and Bias to use.

Eric

fabdev
Posts: 477
Joined: 03 Dec 2018, 21:43

Re: calibration (dark,Flat & Bias

Post by fabdev » 26 May 2023, 23:23

So i guess I now save this image. Which again I guess would be the 11 stacked corrected image. ?
Hi Eric, try stacking 2, 5, or 11 images, the improvement on the stacked result (which will be called "preprocessing01.fit", "preprocessing02.fit", etc.) should be evident, use the full frame blink to verify. To delete the images from the box, right click then "Delete all" from the context menu).
Suppose I wanted to calibrate the the II images individually.
do you mean a sequence of another object ? Again right click in the "Images" box, click "Delete all", then put in the "Images" box the sequence of the other object, it will be very quick, since the darks/flats/biases will be kept from the previous preprocessing.

Actually you could also close Astroart, reopen it, Preprocessing, click "Recent files" in the lower-right corner, and all your darks/flats/biases will be ready for another object.

Another solution is to create a "draft" of this preprocessing, place your darks/flats/biases in the proper boxes (no images into the Images box) and save it with the Save button. Then reopen it when needed. Don't use Masters for now.

Astrognosis
Posts: 14
Joined: 07 Oct 2019, 22:08

Re: calibration (dark,Flat & Bias

Post by Astrognosis » 27 May 2023, 17:05

Good day Fabio,

I shall read through your comments and try them out. I have also had a friend give me some advice on creating darks etc and applying them and also how to create a master.

No I meant to calibrate single images. I'm not an imager so don't usually do pretty pictures. I need individual images calibrated 1 at a time for series photometry. I think I've been shown how to do this. So I have a bit to try out and will get back to you.

Thanks for prompt and thorough instruction.

Eric

fabdev
Posts: 477
Joined: 03 Dec 2018, 21:43

Re: calibration (dark,Flat & Bias

Post by fabdev » 28 May 2023, 21:27

Hi, to calibrate a sequence for photometry, for another software, which cannot correct darks and flats during photometry itself:

1. Enable the option "Save each image".
2. (Optional) Select "None" as stacking method for images, so that no result image will be created.
3. Auto-alignment: usually this is not used, unless the other software cannot recognize objects and stars on misaligned images.

For Astroart instead, see in the guide: Commands / Tools menu / Batch photometry

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