Moving artefact (hair on DSLR's mirror?) - Any easy fix?

[Xiga]

Hey guys

Last night was clear so I set the rig up to capture some subs of the Shark Nebula. I checked the first few subs and they looked good, so I went to get some ZZZ's.

I awoke to a sky full of clouds (was supposed to still be clear!) but thankfully it only cost me the last 3 subs. So I quickly took the flats and then quickly calibrated the subs in APP while I packed away.

When I viewed the subs, the first half looked ok, but then an artefact suddenly appeared and was in all of the 2nd half of subs. What's more, the artefact moves between all of the subsequent subs. When I look at the flats, the artefact is in all of them too, and is also moving between every one. Argh!!

What I suspect may have happened (but would like a 2nd opinion) is that half-way through the session, the shutter dislodged a small hair (I'm guessing it's a hair due to the curve?) and it landed on the mirror. And then with each further shot, the shutter kept moving it. Does this sound likely, or does anyone have any other ideas?

The Master Flat has a long trail running down the middle, basically drawing the path the hair takes throughout each of the 30 flats. Although it's quite faint, which i'm guessing is the reason why the calibrated first half of subs looked ok (with a quick stretch), I suspect on full PP the trail would eventually show up. But the artefacts in the individual 2nd half of subs is really quite dark.

I've attached 3 pictures I took with my phone before I packed up, as well as the Master Flat.

I'm loathe to bin the 2nd half of subs, as I capture little enough data as it is these days. Is my only option to just stack them and try and clean it up as best I can manually in PP? (I mostly use PS).

Note to future self - always use the air blower on the camera before attaching to the scope! ?

[Xiga]

Thinking about this some more, my optical train is usually pretty clean and I don’t normally suffer from dust bunnies (apart from the few darker spots visible above, which I’m guessing are on the D5300 mirror as they are always in the same place). I’ve been able to re-use flats before, so I can probably just calibrate the subs with the flats from my previous session. That should at least mean that the 1st half of subs should be useable.

As for trying to make the affected subs useable, the only other thing I can think of is to do 2 stacks, one with just the first half of subs, and another with all of them. Then layer them in PS and use a bit of jiggery-pokery to repair the streak. I guess I need to do a stack first before I know how bad the problem is going to be.

[wxsatuser]

It will not be on the mirror as that's out the way when shooting.

[George Gearless]

I'd be very much interested to learn if there is any easy fix for this. I've got a big blob of a dustbunny at the very bottom of the field. Luckily it's in the bottom 1/10. So it's easy to crop out without losing to much of the total picture. But it annoys the hell out of me.

[Knight of Clear Skies]

If it moves between subs a sigma-clip may help remove it. If that fails the spot-heal brush in Photoshop works pretty well.

[Alien 13]

I have had a hair trapped at one end in the mirror box which caused lots of weird effects with the free end dangling close to the sensor that changed with every shot, I also had a tiny insect that got in and was visible through the viewfinder.

Had to spend ages with the bug as I was not sure if he had brought his mates with him, even removed the focusing screen in the end and subsequently damaged it (easily marked bit of plastic) but got a replacement split prism type (like the old film cameras) and was easy to fit.

Now all my camera bags have a nice stick of cedar wood in them 

Alan

[JOC]

It's a good job it wasn't a Rabbit!