Finally a bit of clear sky and I'm seeing something I've not seen before. The first image looked OK....the next 3 really strange black circles moving to different positions with each exposure. Is this moisture?
looks like the makings of a nice 1532 there. the black marks look strange, it is almost it is like it is a small bug moving around fairly close to the sensor
Thanks Aidan. You are the 2nd person to suggest that! How a bug would get into this sealed system is a mystery. I think tomorrow I will need to break it down. The filters are too dirty anyway so it's a good excuse.
Probably just some crud.Perhaps your shutter is shedding a small amount of material?
Your filters are pretty dirty by the way. Some filter wheels have cutouts in their filter wheel. I have read where this can cause the dust donuts to move around from the wind of the filter wheel moving. This would then not be able to be flat fielded out which assumes the donuts don't move. I find my FLI filter wheels are very good for this. Clean the filters well, install them and then 3 months later they are still clean. Its why I got a 7 position filter wheel even though it was expensive as it stops the constant opening and closing to fit Narrowband then take them off again.
I use a Hurricane blower and a photographic micro fibre cloth to clean them and inspect them with a bright torch illuminating them at an angle to get a reflection to show up spots. I am for a fully clean image without the need for dust donuts to be removed with flats. It takes a lot of pressure off of the calibration process.
Whilst flats may remove dust donuts on some systems unless your darks and biases are perfect and your flats taken really precisely they won't. Also you've got to wonder if the crud is large enough to make a black spot that large does the signal ever get fully restored if it never fully arrived in the first place?
You are certainly correct that my filters are filthy! However, it cannot be the shutter or the FW moving because there is no shutter on the Trius. And the FW was on the green filter for 50 images in a row. No focusing and no slewing either. So I still think it's a bug, now hopefully quite dead. I put the ONAG, FW and cameras in a bag with some insect killer. Time will tell!
Peter
PS Thanks for the cleaning tips. I've tried before and find the process really frustrating. I know I've got to do these soon. I probably will if the bug or whatever has survived.
I have to do something like that myself soon. I get these tiny little spiders that float in the air and land on the scope. They are tiny and weave a couple of strands of web overnight.
