The previous one's sky was much too black.
9 x 90 secs @ ISO 400.
Does anyone know why Rigel and Betelgeuse most noticeably have shadows of my 5 leaf shutter on their outer sides; sharply rendered
on the individual subs, and still there, but blurred, on the final image.
Needs magnifying to see easily. It just occurred to me that it could be that the shutter was illuminated by stray light and reflected off the back of the lens, could that be right?
raymo
Hi Raymo,
Seems like you have your mount problem resolved OK. Had similar problems the other night much to my aggravation. Lost the night's imaging - and it was a beautiful night too.
Yes, stray light can cause problems like these. Do you use a dew-shield? They also act as a good light shield.
Robert
So this was taken through a normal camera lense? I would question whether a lense has the full mulitcoating regime that is used in telescope optics but I could be wrong. Be aware that the stock sensor cover glass is also highly reflective as shown below.
Watch this utube video of a comparison of the stock cover glass reflectivity with an Astonomik MC Clear cover glass.
First, Robert, the mount problems last night were the last straw; it has now officially gone bananas, did one iteration o.k. and after the second one it said I was 23 degs off in Az and 9 degs in Alt. Gave up and did a rough drift align which got me 110 sec subs with this lens.
I have a huge dew shield for the Newt, but not yet for this little lens, must fabricate something for it.
Thanks for the info Glen, I'll have a look at it.
Thanks Dunk, with better P.A.I'll go for longer subs.
raymo
Last edited by raymo; 31-12-2015 at 08:31 PM.
Reason: more text
Hi Raymo
I think the Rigel and Betelgeuse issue is a sort of coma.
It's not that noticeable on your IIS compressed image, but I often get artefacts that appear worse the further away from the centre it gets.
Stopping down the lens will make it better, but then you'll have to increase the exposure time to compensate.
Cheers
Bob
Hi Bobby, on the hi res version they are almost perfect pentagons,
mimicking exactly the 5 leaf aperture diaphragm. I still think that they are reflections from stray light. I'm going to try the same shots again,
but with a shield to block out what I tend to think is the offending street light. Thanks for looking.
raymo
Barnard's Loop is trying to break free!
