Any idea what this is?

[StargeezerTim]

Hi, this is the DSS output (in jpg) of 15 X 5min subs of M29 taken last night. I used a UHC filter.

Any idea what the line is? It is on all the individual subs in the same position.

I also took images of M57 & and Crescent Nebula with no problems.

I had this once before and assumed it was a diffraction spike originating from Vega that was nearby, but no star of origin visible here.

Another thing...any idea of how to get rid of it! Thanks.

[Tinker1947]

just read your post properly....no idea....was going for a Satellite but  that would only affect one sub....

[StargeezerTim]

A satellite, just find the sub with it in and delete the sub..... 

its in all the subs!

[Uranium235]

If its in every sub, in the same spot, you cant get rid of it by stacking. You will need to go in close with Ps and use the clone brush (very carefully!) to heal the image.

Its possibly an odd diffraction spike, the bright star does not have to be on your chip to make its presence felt (especially if its Vega!).

[swag72]

Have you used calibration frames at all? I wonder if bias frames would sort it. I say that as I have a bad column on the camera I am using at the moment and bias frames will get rid of these sorts of defects.

[StargeezerTim]

If its in every sub, in the same spot, you cant get rid of it by stacking. You will need to go in close with Ps and use the clone brush (very carefully!) to heal the image.

Its possibly an odd diffraction spike, the bright star does not have to be on your chip to make its presence felt (especially if its Vega!).

Thanks...would you do the cloning before or after the stretching and processing? There should be some nebulosity right where the line is...

[StargeezerTim]

Have you used calibration frames at all? I wonder if bias frames would sort it. I say that as I have a bad column on the camera I am using at the moment and bias frames will get rid of these sorts of defects.

Yep....Darks, Bias and flats....   

[Uranium235]

Thanks...would you do the cloning before or after the stretching and processing? There should be some nebulosity right where the line is...

I'd do it after, just as your're doing the the final few tweaks. It takes a steady hand, and lot of zooming. Have your history window open too (in case you need to take a few steps back).

[Mrbloke]

Contrail? It's going to take some work to get rid of it, is it worth it?

[swag72]

Does it show on your bias or darks? Or just the light frames?

[StargeezerTim]

I'd do it after, just as your're doing the the final few tweaks. It takes a steady hand, and lot of zooming. Have your history window open too (in case you need to take a few steps back).

Thank you...   

[StargeezerTim]

Does it show on your bias or darks? Or just the light frames?

Just the lights...and only on this target...one of three I captured last night...

[swag72]

Strange..... At least you know its not a camera issue. Looks like the clone / heal tool is going to be your friend.

[ollypenrice]

There are some easy ways to fix this kind of thing quickly. For example;

Create a copy layer, make the top invisible and work on the bottom. Not bothering to protect the stars just use the biggest clone stamp the starfield will allow you to find and stamp over the line (and any nearby stars.) Now make the top layer active and visible and use the eraser tool to take off the line. If you can make a star selection or have Noels Actions Select Brighter Stars then this would make it even easier to remove only the line. (You'd select the stars, expand and feather the selection slightly and then select inverse.)

This method would be easier than clone stamping the top layer accurately.

But why is it there? Good question! It's slightly curved and not orthogonal so I doubt it's electronic. Something odd's going on with the bright star on the left, too. You weren't shooting through a clothes line or with a spider's web in the path?

Olly

[MattJenko]

The bright stars all have elongated horizontal lines so I suspect an overhead cable or something along those lines, boom boom. I have had something similar when imaging through an overhead phone line. The brightest one could be a diff spike along the cable from a bright nearby object.

[Stub Mandrel]

The line is curved more than I woudl expect so close to the centre of the image.

[Moonshane]

I was going to suggest washing line or similar.

[StargeezerTim]

It's a mystery but my best is that it is Vega interfering with my image (without my permission). I wasn't shooting though any lines or physical obstructions, and the line is in the same place throughout over an hour of tracking the target. Also the other targets last night (crescent Nebula and Ring Nebula) were all fairly adjacent and were captured without probs... Strange........

[StargeezerTim]

It's a mystery but my best is that it is Vega interfering with my image (without my permission). I wasn't shooting though any lines or physical obstructions, and the line is in the same place throughout over an hour of tracking the target. Also the other targets last night (crescent Nebula and Ring Nebula) were all fairly adjacent and were captured without probs... Strange........

Sorry....Just checked and I think I was a little unkind to Vega...Its actually closer to Deneb... but not actually adjacent to any really bright stars, as far as I can see. I do live next to Stanstead Airport.....   

[StargeezerTim]

Contrail? It's going to take some work to get rid of it, is it worth it?

Probably not... I've just stretched the image and found no evidence of nebulosity...  Up the iso and start again, I think!

[toxic]

i was going to blame reflection on the skywatcher cc but it looks like you didnt use one so it could it be light leaking in from the back of the dslr' i have had that happen in the past and it can do some strange things to the subs.

[Alien 13]

I have been caught out with a clothes line before its even more confusing when there is a slight breeze and its on most but not on every sub.

Alan

[Paul M]

Interestingly the artifact is parallel to the faint diffraction spikes on the brighter stars of M29. And if Sadr (gamma Cygni) had an extended diffraction spike that could be it.

Why it would be isolated and so far off Sadr is another question

[Stub Mandrel]

I'm sure it's curved. Wouldn't a diffraction spike be straight? My money's ona something shining into the viewfinder at an awkward angle.

[Paul M]

I'm sure it's curved. Wouldn't a diffraction spike be straight? My money's ona something shining into the viewfinder at an awkward angle.

You'd think so. But on that image scale could the focal plane be non-linear?

It's just that playing with Stellarium and comparing the orientation of M29 and it's diffraction spikes in the image, I found that the artifact points almost exactly at Sadr!