White master flat in ccdsoft

[Joshua Bunn (Joshua)]

Hi - again,

Last night i could open a master flat in ccdsoft and it looked as it should. However, this morning, i open it up in ccdsoft and its all completely white. I can open it in ccdstack 2 and its all good, but it displays as all white in ccdsoft and the pixel values are waaay high. Anyone know how i can get around this?

thanks
Josh

[Dennis]

Hi Josh

Is CCDSoft auto-stretching the Flat? Try playing with the Histogram Stretch function.

Cheers

Dennis

[Joshua Bunn (Joshua)]

Thanks Dennis, thats what it was. But what should i set the histogram to to undo the the auto contrast?

Josh

[Dennis]

In the CCDSoft Menu Bar select “Camera” then “Setup” from the drop down menu.

This should open the “Camera Control” Panel.

Select the “Setup” Tab and tick the “Auto contrast” box and I think that this should stretch your image from min to max.

Note that this does not actually change any image data in the image file; it just defines how that data is to be represented on your computer screen.

Cheers

Dennis

[Joshua Bunn (Joshua)]

Thanks Dennis,

It doesnt seem to work for me, i followed your advice. I note that it only does it on the master dark, i can open a single dark frame and it will display "normaly". I shot the darks using ccdsoft and combined them in ccdstack. But it did all work yesterday. Im obviously doing something wrong.

thanks
Josh

[Dennis]

It could be that CCDStack is saving the processed FITs file as a 32 bit file, whereas the native Dark files from your CCD camera are 16 bits?

Cheers

Dennis

[Joshua Bunn (Joshua)]

Well, the master bdark was 32 bit and the original 16 bit, what should they be?

Edit: saving the master dark in 16 bit fixed it, but in ccdstack there are several 16 bit options, should it be saved as 32 bit anyway?

Edit again: I saved the master in ccdstack as 16 bit signed and it looked too black in ccdsoft. As 16 bit unsigned in ccdstack and it looked as it should in terms of contrast in ccdsoft. As 32 bit float and it displayed as all white, and lastly as 32 bit integer in ccdstack and it was the same as 16 bit unsigned in ccdsoft. Which one is best? I also better start reading the ccdstack manual .

I will also read this thread.

thanks