UPDATE FROM MABULA
I have had a very rough 2 months unfortunately health wise. I was struck 3x in a row with bacterial infections. The second infection occurred  after a routine hospital checkup and I became very sick. I had to rest and take a lot of antibiotics. Once I was recovering and restarting work 1 month ago, I again became sick. The infection was not yet gone, so even more antibiotics and rest was needed. Needless to say, it took a lot of my energy and I needed a lot of rest.
Finally, the infection is really gone and my energy is coming back step-by-step now and I have started work again. I am terribly sorry to have kept you waiting for support. I will address all outstanding questions and e-mails step-by step and will be on the forum daily from today.
APP 2.0.0-beta47 will come soon as well, a lot of work was already completed before I became very ill, so the release is also nearly ready for you. Beta47 will be much faster actually. Many workflows will be more than 2x faster, mosaics can even be 10x faster than before because registration really received a major boost... all compared to beta46. Â Before I release it, I will make sure that everything is working properly and then I will release it.
Hi,
I am seeing artifacts like you can see on the stars in this picture in my stacked image (scaled 2x, droplet size is 1.0). I was hoping someone more experienced than myself could see right away what this is and what might cause it. I used local normalization rejection on this image (but I have to admit that I don't know what exactly this does and whether it could cause something like this), my re-run without it is still in progress.
Thanks for your help,
Felix
Felix
I'm assuming since you mentioned droplet size that this is a drizzled integration. If that is so then I'll start with a few questions.
- Is this a bayer drizzle with a colour camera, or a normal (non-bayer) drizzle ?
- How many exposures and how many dithers were performed.
- Is the data undersampled (what arcsec/pixel ratio)
If I had to make a completely uninformed guess based just on the image and your post, I would guess that you may have done a bayer drizzle with too large a scale, too small a droplet size and not enough dithers. But that's just a guess.
The local normalization rejection is unlikely to be the culprit here.
I would also suggest that you do a non-drizzled test integration. If the problem goes away then you will know it is a drizzle issue. If it doesn't then we will need to look elsewhere.
JC
Thank you for the quick reply, JC.
The problem is gone after I reset all of the menues. One thing I did notice is that the normalization maps all had the stars visible, which I believe is not right.
The frames come from a mirrorless camera, taken with a 200mm lens (so quite undersampled if I understand correctly). I have 100 frames, dithered either every 3 or 7 frames (sorry, I changed the settings during the night and can't remember when exactly).
Unfortunately, I no longer have the settings of the menues before I reset them, so I cannot diagnose what I had done wrong (for posterity), but the immediate issue appears be solved at least.
Felix
I'm glad the problem is gone. I still strongly suspect it was caused by innapropriate drizzle settings.
Do you still want to drizzle the dataset ? With a 200mm lens your sampling will be somewhere around 6 arcsecs/pixel - so there may be some value in drizzle, as long as the parameters are appropriate. Drizzle is typically used either to fix 'blocky' stars or to upscale the image - perhaps to allow a crop that features a small section of the original image.
For a Bayer drizzle with a colour camera, I would suggest starting with a scale of 1.0 and a droplet size of 2.0 (I think the opposite of what you used), and ideally at least 30-40 dithers - more would be better. This should round the stars nicely. As the scale is increased, or the droplet size is decreased, the noise in the resulting image will increase - until eventually there will be drizzle artefacts that distort the image. These negatives can be reduced to some extent by increasing the number of dithers - even 80 to 100 dithers is not excessive.
If you want to test different drizzle settings quickly @mabula-admin has suggested that you change the composition mode in 6) Integrate from 'full' to 'crop' and select a small part of your image. This will integrate much more quickly.
JC
Hi Felix @edx,Â
Thanks John for assisting here 😉
I am glad that the issue is solved by resetting the menus. To me the problem looks like to aggresive outlier rejection in 6) Integrate. Could it be Felix that you were manually rejecting outliers and had the high kappa very low?
Mabula
