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.
Hello
I got a Newton 800mm/f4 with OAG, comacorrector with screwed on filter optolong L-Pro, camera Zwo 294 Mcpro
2 days ago a took several pictures , gain 120, -10°, 180 sec
I also got darks, flats and darkflats
There was some moonlight !
I got very strange effects after stacking in APP
I took stacks with calibration files, without flats, without darks, with few lights with lights when the moon was almost under.....it gave always almost the same effects, see examples hereunder.
only the stack without calibrationfiles seems to be better
(all exposures are streched at 30%)
What could be the cause ?????
The strange thing is that i took already a lot of pictures in the past without this effect !
Could you please help, thx
GR
Dirk
Is it somthing in APP or could it be the reason of reflection of the moonlight ???
Dirk (@dirkvl)
I don't claim to understand this, but I have seen almost exactly the same results under certain circumstances. I have a theory, but not enough evidence to be sure about it.
My theory is that when you are using a fast focal ratio, with a colour camera, and the light pollution is perhaps stronger than normal, that too long an exposure time will produce an image that won't calibrate correctly.
In my case I was using an F2 lens with a 2600mc in a suburban back yard with a little bit of moon. I was shooting 60s exposures (which is about the same as 240secs at F4 - so in the same ballpark as you) and I got similar results. I thought I had stuffed up my flats, but redoing them didn't help.
I could be completely wrong about this, but if this theory is correct then you need much shorter exposures when shooting with your fast F4 system under those conditions.
I hope this helps (and doesn't mislead).
JC
Hy John, thanks for your reply
Its worth to try
goin to test it perhaps this evening , almost full moon and they expect here some clearences
Gr Dirk
Hy,
could it be caused by the filter i screwed on the top of my corrector, it has a mettalic edge.... (see attachement)
And it looks like those effects only appear when there is some moonlight....
Dirk
I doubt that the filter is to blame - but who knows. At least that gives you something you can test. I did have a similar idea about reflections off the lens shield I was using on the F2 lens, but I dismissed that idea. Maybe I dismissed it too quickly.
JC
Hi Dirk,
I have an Apertura 6" F4 newtonian with a ZWO 183MC pro and have never had any issues shooting at 180 seconds or with moon light. Now, I haven't used the newest versions of APP but I doubt that is the issue. A couple of thoughts. I believe a filter will change focal distances so I personally would not want anything in front of the coma corrector that might effect it's operation. I would place it in a filter drawer or filter wheel between the corrector and the camera. I think I have also read that if the focusing tube extends into the telescope tube, that can have some effects on the photo. I don't know if yours is that way when taking photos or just to show the filter on it. Also don't know if it would cause the effects you're seeing. If it is that way when taking photos, I wonder if taking flats with the shiny filter extending into the tube could cause some odd reflections. Good luck.
Tom
Tom (@tfergu01)
I think these are good suggestions, but surely if the filter is the issue it would affect all flats taken with the filter in place. Dirk (@dirkvl) has said that he has not had this problem before. Just the same, I agree with your suggestion that the filter would be better placed behind the corrector (if Dirk's backfocus allows it).
Dirk's bortle class may be very different than yours. Another possibility is that he (and I) might have had some very light high cloud that magnified the lunar light pollution. I know - I'm clutching at straws here 😉 , but I would really like to understand this problem better.
JC
Hi John,
Oops, I thought when he wrote "I got" , he had acquired a new telescope. In that case, yes, seems odd to have an issue now. Hopefully Mabula can figure this one out.
Tom
Just did a new test last night with no filter .....same result see attachement
Getting a little desperate....
Dirk (@dirkvl)
I am left with only two suggestions, and I'm not that confident about either.
Firstly, did you try my suggestion of much shorter exposure times ? Something like 30 secs, just to see if the problem goes away.
Secondly, I noticed that the inside of your newt's tube looks like a pale grey. I guess if the lunar separation (from your target) is low then there might be a lot of moonlight bouncing around inside your tube. I understand that a lot of newt owners recommend lining the inside of their tubes with some sort of black matt flocking material, although I thought this was mainly to improve contrast. Might be worth considering.
My question for other readers of this forum. Surely Dirk and I can't be the only people who have experienced this issue ? Is there anyone who has solved this problem, or at least been able to understand the cause with reasonable certainty ?
JC
