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. Before I release it, I will make sure that everything is working properly and then I will release it.
Scattered red, blue and green point clouds in a stacked and stretched image. I am thinking it could due to dithering, where some interpolation must be performed.
Jørgen (@mailjorgenhald-dk)
At first glance it looks like these could be hot pixels on the camera sensor, combined with dithers that may be too small and too few.
Did you use a good masterdark (exposure time and temperature matched). Is it reasonably 'fresh' (or like mine - a bit too old 😉 ). A new BPM ?
How many exposures. How many dithers. What size dithers.
There are other possibilities, but this is where we should start.
JC
John Connor
Thank you very much for your response.
Looking once more at the above image, I noticed that all these small point clouds (in R, G or B) all have the points distributed in the exact same way. To me that indicates dithering being the cause as stated also by you. So the bad/hot pixels get repeated in the pattern of mount movement during dithering. If the system could identify the movements and if the Bad Pixel Map were known, perhaps the point clouds could be removed? I was hoping that such functionality had already been impllemented.
The light frames used for the above image were taken on October 4th 2024, while the Dark frames were taken on October 17th 2023. I guess that is a bit too long time difference? I have no stored information about the performed dithering, but 35 images were recorded and used.
The focal length of the telescope was 342 mm, explaining why the point clouds are compact.
I can upload a newer session with new Dark frames. Would that help?
Jørgen
Jørgen (@mailjorgenhald-dk)
That's definately the place to start. Take a new set of darks (exposure time and temperature matched), make a new masterdark and try a new integration. Don't reuse the old BPM - let APP make a new one. I always take at least 30 darks - some people recommend more and some recommend less.
To my shame, my masterdarks are older than yours - but different sensors degrade at different rates so this is definately worth a try. If hot pixels are the issue this should sort it out perfectly, although ideally your 'new' darks should have been taken at about the same date as your exposures.
If this integration is from 35 exposures then it looks like you must have dithered every exposure. Nothing wrong with that - its a good thing - but it makes me a bit more confident that it is an out of date masterdark that is the issue. I do wonder if you may have changed the rejection settings. You should ensure that APP is using the default settings to start.
I would note that I have seen some people recommend that a BPM should be created and saved from a room temperature masterdark - to give the best chance of catching all the borderline hot pixels. I have never found that necessary and don't really recommend it - I just thought I would mention it for your consideration.
JC
On 15/3 I took a new set of Darks, and to have the Darks and the Lights close to each other in time, I used a set of exposures of M101 taken 19/2 2026. All the point clouds have gone! I am surprised that Darks must be taken so close in time to the Lights.
Thank you so much for your valuable input to my problem.
Clear skies
Jørgen (@mailjorgenhald-dk)
You are very welcome. Hopefully your sensor will have 'settled' a bit and you won't need to keep refreshing your masterdark too frequently. But you will know when you need to do it.
JC
