Hi all!
I have a small problem and I can’t figure out the cause. Appreciate any help or suggestions.
During three consecutive nights in April, I shot M13, The Great Globular Cluster in Hercules, using my EdgeHD 8” f/7 and ASI294MC. I used a Baader UV/IR-cut filter, 60 seconds exposures at Unity Gain and -20 degrees. I used my usual Superbias, matching MasterDark and MasterFlat from the first night (using my LED-panel). I did not Dither.
I used Blink to sort out less good subs and subs with sat trails, and the Subframe Selector Process to weigh the better ones after FWHM, SNR and Eccentricity. I then used the best sub for registration and integration. It happened to be a sub from the second night.
April 21 I got 168x60sec exposures, April 22 - 240x60sec and April 23 - 219x60sec.
Using the best sub, mentioned above, as reference during stacking subs from any ONE of the nights, results in a photo with a reasonably smooth background and good looking stars. However, any combination of TWO or THREE nights results in a photo with lines in the background in a 45-degree angle. Still the stars look good.
The settings I use are mostly PixInsight Default, and they are also the settings I always use, most times with good result from a novice’s point of view.
In the jpg below one can see the difference between my integrations.
https://www.dropbox.com/s/zeq2gq1gw1u4pkp/M13_PI.JPG?dl=0Here are links to XISF-versions. They are just integrated and cropped, no further development.
One night integrated:
https://www.dropbox.com/s/lyw5m0cnxpq53vh/Integration_M13_April22_crop.xisf?dl=0Three nights integrated:
https://www.dropbox.com/s/taeo6hrrl5qdbnl/Integration_M13_April21_22_23_crop.xisf?dl=0Is there an obvious reason to these lines? Is it a no-dither-multi-session-issue? I have stacked multi-sessions before without this phenomenon…
Below is a link to the same corner of my photo of M51 from the week before. Shot with the same equipment except for the filter. My development process was the same, however I used dithering, longer subs, LPS-filter and a few hours longer integration time. It consists of 233x180sec and 89x120sec.
https://www.dropbox.com/s/ktshwrjwqy1qz3q/Integration_M51_April11_12_13_14_crop.xisf?dl=0Regards,
Anders