Flat frames and months of try or miss (99% miss)

[Altayer]

Hi,


Flats are giving me headache. it did work with me once with early morning sky flats. after that  I bought  spika-a flat fielder and paid 200$. not good outcome from the product.




the one on the right is flat processed and the one with big gradient is non-flat processed.


if I do DBE with the flat processed image, it will bite a big chunk out of the back ground but will leave a really nice image of the object.


I've been trying for months with no success.



the image is L only.

[NGC7789]

Perhaps you need to test your flats for flatness. Take two sets of flats one with your panel rotated 90 degrees with respect to the first set. Use one set to calibrate the other. The result should be an evenly illuminated field (within some acceptable tolerance). If it's not then your flats are not flat.

[Altayer]

good idea,

will try it soon.


otherwise I might have to look at the Alnitak Flat panel

[jerryyyyy]

I recently had to redo my flats and got good results with the new version of SkyFlat Assistant.  If you use Maxim, you may want to look into this.

[Altayer]

I have used the Flat Wizard Calibration in Main Sequence Generator and set it to caculate the ideal exposure for a target of 30,000 ADU. and captured those flats based on that exposure.


I don't have time to wait 'till dawn to capture flats. Will Alnitak Flip-Flat do any better?


ny ideas?

[mschuster]

Alnitak works, but I would not buy one yet. The problem could be data collection or calibration/processing issues. Compare your panel flats to your sky flats that you said worked. How do these two types of flats differ? Also might try doing a PixelMath sanity check: (light - dark) / (flat - bias). You probably need to set the PixelMath auto scaling option, as this formula is not normalized properly. Use raw frames, not masters here, the result will be noisy but should be in the ballpark and appear reasonably "flattened". Looking at things like this might help diagnose the problem. Also double check that all of your frames are 16-bit raw with no calibration by the capture software.
Mike