Astroart Forum

What are the FIT headers AVISUMIN and AVISUMAX ?

When I finish preprocessing .fit files I get one set of values of AVISUMIN and AVISUMAX
When I save the file (Save 16/32bit) The values of AVISUMIN and AVISUMAX change

I have attached screenshots of preprocessing results and after saving the file.
Why are they changing and does this affect the image contrast ?
I want to adjust the image contrast.

Thanks

Erik

What are the FIT headers AVISUMIN and AVISUMAX ?

Hello, they are the visualization thresholds inside Astroart. They are used only when you reopen the image.

When I finish preprocessing .fit files I get one set of values of AVISUMIN and AVISUMAX

They were the visualization of a single raw image.

When I save the file (Save 16/32bit) The values of AVISUMIN and AVISUMAX change

They are saved, with the values currently used. (In the Status Bar of the image, the data: V = ...)

I want to adjust the image contrast.

If you want to adjust the visulization of the image (so, without changing the image ADU data) just rotate the mouse wheel, or move the cursors, or use the Histogram window.

If instead you want to modify the data, use the filter Histogram Stretch, or DDP, or Scale, etc.
Fabio.

Fabio,

Thanks for your explanations.
I am doing optometry so will "If you want to adjust the visulization of the image (so, without changing the image ADU data) just rotate the mouse wheel, or move the cursors, or use the Histogram window" .

Erik