Was happily collecting images the other night... and then found a big fat donut when I was processing in Photoshop.
Now... it wasn't happening just a few night before... not a spec... but I am assuming it is a collimation problem?? Odd that it just sprang up out of no where... don't remember bumping or jolting the scope... and only carried it from the house to the backyard.
So... from all you far more knowledgeable people than me... am I right? Collimation needs fixing up?
It's just flare from Alnitak, the bright star. Some scopes handle it better than others. Sometimes placing it in a different part of the field can help, sometimes not. Everyone loves Alnitak! Not.
I believe it is an internal reflection of your imaging train Geoff caused by the bright star Alnitak in the field of view. The center of the "doughnut" is the secondary mirror. You will probably find that it will happen on any really bright star without changes to your imaging train to reduce the reflection. One of the largest internal reflections I have ever seen though. I got a reflection as well when I imaged this area of sky: https://www.facebook.com/CapturingTh...type=3&theater
Were you imaging an area devoid of bright stars the night previous you mentioned?
Wasn't devoid of stars... was doing Orion, Carina... testing out my new focal reducer, which I thought was the problem at first. Took it out of the optic train, and still got a similar effect, which is why I was thinking collimation.
The flame and the horse are the faintest objects I have tried to image so far... so it seems that fainter nebula near a brighter star is problematic.
Any tips on reducing the effect? Other than the one given... moving the image in the scope a bit. Can it be dealt with, even a little, at the Photoshop stage?
