DSS vs ASTAP

[bomberbaz]

Hello all.

Just a very brief overview of a comparison I did for no other reason than I had a few minutes to kill.

There is only a small amount of data (about 30 mins) on M81 at the heart with M82 and NGC 3077 off to upper sides. 

The images are messy but these are purely stacks including usual calibration files, I have done nothing else to them so I just thought I would stick them both up.

DSS is well known and simple to use, ASTAP is a little more involved but none the less not too difficult once you learn how it thinks!

Top one, DSS, bottom ASTAP. I would welcome opinions and will post again when I have added further data to see if there is anything else.

[tooth_dr]

The background looks odd, like the flat calibration isn’t correct.  I’m not sure what camera you used, some OSC are harder to calibrate.  When I calibrate my own OSC data it either has a completely flat background or just a simple gradient running across it if imaged during the moon.  If you can sort this issue it’ll make processing 100x easier.

[alacant]

14 hours ago, bomberbaz said:

opinions

Hi

Guessing: There may be cloud on one or more of the frames? Light entering the telescope? Condensation? Non-corresponding flat frames? Difficult to say without more detail, but easily fixed. If you corrected each frame before registering and stacking, even better.

I used Siril, but I think ASTAP may have something similar.

Cheers and HTH

Edited April 26, 2023 by alacant

[bomberbaz]

6 hours ago, tooth_dr said:

The background looks odd, like the flat calibration isn’t correct.  I’m not sure what camera you used, some OSC are harder to calibrate.  When I calibrate my own OSC data it either has a completely flat background or just a simple gradient running across it if imaged during the moon.  If you can sort this issue it’ll make processing 100x easier.

 

2 hours ago, alacant said:

Hi

Guessing: There may be cloud on one or more of the frames? Light entering the telescope? Condensation? Non-corresponding flat frames? Difficult to say without more detail, but easily fixed. If you corrected each frame before registering and stacking, even better.

I used Siril, but I think ASTAP may have something similar.

Cheers and HTH

 

Just looked at the L2 filter, there is a smudge print on it, might be the problem or it could be the lights although they are new ones. Think I shall start again, clean my filters with some isoprol, blow out the focal train for dust and do a new fresh batch.

 

EDIT> The flat fit below explains it, very bad indeed.

Flat_160.0ms_Bin1_183MC_gain115_20230425-174344_0011.fit

Edited April 26, 2023 by bomberbaz

[tooth_dr]

On 26/04/2023 at 13:11, bomberbaz said:

EDIT> The flat fit below explains it, very bad indeed.

Flat_160.0ms_Bin1_183MC_gain115_20230425-174344_0011.fit 38.5 MB · 4 downloads

 You cant be sure if a flat is bad by looking at it, it can look awful but as long as it corrects the data properly then its good!  Unfortunately the fresh batch of flats wont be any use for the lights above but it's always better to have clean surfaces as much as possibe.

[bomberbaz]

6 minutes ago, tooth_dr said:

 You cant be sure if a flat is bad by looking at it, it can look awful but as long as it corrects the data properly then its good!  Unfortunately the fresh batch of flats wont be any use for the lights above but it's always better to have clean surfaces as much as possibe.

I have got to the bottom of this in another thread.  It was a comedy of errors on my behalf but thankfully with the help of other peoples input and hindsight of the mistakes it has now been sorted out.

The main error above is a variable level output from a tablet being used as a whitescreen, that is what has led to the uneven image results. A sheet of white paper and a slow rotation of the tablet  device evened out the flats and the latest results were significantly improved.