Good Day CN,
I just thought that I would share this information in case a new user of Pixinsight encounters the same issue that I did.
When I first started using PI about 9 months ago, after running the WBPP script to pre-process my data, the brighter stars were "square" or "pointed" looking.
It definitely looked like an anomaly to me. Possibly something wrong in my optical train. I was hesitant to post to the PI forum because of my "newness" to the software, so I used DSS to stack. In the DSS stacks, the same "square" stars that produced by PI, were nice and round. I did some researching on Google and saw that this issue could be remediated (somewhat)
by changing some settings in PI for pre-processing or just used DSS for pre-processing.
So, for the last 9 months, I have used the modified settings in Pixinsight’s WBPP.
Just recently, I started using a new scope (Sharpstar 61 EDPHII) with the same camera (ASI 533 MC-P) and reset the PI WBPP script settings back to default. When I generated the first masterlight with the new scope, I zoomed in and saw the same "square" stars again!
So, I ran a test so that I had the images to post to the PI forum.
I prepared a PI masterlight with the WBPP defaults (with "square" stars), another PI masterlight with the modified settings that I had been using (only slightly "square" stars) and an Autosave.fit with DSS to compare the three.
I applied a screen stretch to all three with no additional processing.
The WBPP masterlight with default settings had the "square" stars, but had obviously better quality (resolution) than the WBPP settings that I had been using trying to minimize the "square" star effect. The DSS autosave.fit had the nice round stars, but the resolution was the lowest of the three in the test.
I posted to the PI forum and here is the link in case you are interested.
Here is the comparison image that I submitted to the PI forum (I don't think that it can be viewed unless you are logged into the forum). This is a 2x zoom in on a part of the M31 dust lanes with only an unlinked screen stretch with no processing.
The PI WBPP with defaults is the image on the left (Square stars with the best resolution). The PI WBPP with the settings that I have been using to get "rounder" stars is in the middle. The DSS stack is on the right.
I found very little searching for this on Google or in the PI forum, but just in case you might have noticed a similar issue and were not sure why, here you go.
Ignorance on my part and I wish that I had posted the issue to the PI forum earlier, but definitely an unexpected happy ending!