Odd artefact help please

[RayD]

Was doing some testing on M51 last night, and when a 300s sub downloaded I was met by the below anomaly.  It was worse with 600s.

I've checked, double checked and triple checked everything in the imaging train, and it is squeaky clean with no obstructions or alike.

I thought it looked a little like light intrusion, so taped over the flashing red LED on the SestoSenso (I have submitted a feature request for this to be switchable in software) but the next image was the same.

Do any of you have any ideas, and do you reckon I should look at possible light sources, or any ideas you may have as I'm a little stumped.

This is the image straight off the camera and just converted for uploading, so no stretching etc. carried out.

[souls33k3r]

Here's an idea mate, cover the scope end and take a say 300s dark frame. See if you're still noticing this light leak. This was you'll know whether it's something creeping in from the scope end of through other bits of your imagining train.

I did help a friend out not too long ago where he had some strange light leak. What it was in the end was a wrong camera adapter fitted to his camera and that was causing the light leak. We changed it to something else and *poof* there was no light leaking in.

[RayD]

8 minutes ago, souls33k3r said:

Here's an idea mate, cover the scope end and take a say 300s dark frame. See if you're still noticing this light leak. This was you'll know whether it's something creeping in from the scope end of through other bits of your imagining train.

I did help a friend out not too long ago where he had some strange light leak. What it was in the end was a wrong camera adapter fitted to his camera and that was causing the light leak. We changed it to something else and *poof* there was no light leaking in.

Cheers mate, you think the same, it looks like light leak?  I'll have to have a good look over as I cannot for the life of me think where it would get in (apart from the open bit at the front of the telescope of course).

[RayD]

Thing is it is the Tak and Atik 16200 and I'm using all the Tak adaptors etc.  I had a thought this afternoon which was there is an infrared motion sensor quite near where I'm imaging.  I wonder if it might be picking something up from that?

[alan4908]

19 minutes ago, RayD said:

Was doing some testing on M51 last night, and when a 300s sub downloaded I was met by the below anomaly.  It was worse with 600s.

I've checked, double checked and triple checked everything in the imaging train, and it is squeaky clean with no obstructions or alike.

I thought it looked a little like light intrusion, so taped over the flashing red LED on the SestoSenso (I have submitted a feature request for this to be switchable in software) but the next image was the same.

Do any of you have any ideas, and do you reckon I should look at possible light sources, or any ideas you may have as I'm a little stumped.

This is the image straight off the camera and just converted for uploading, so no stretching etc. carried out.

Occasionally, I've had a similar issue - in my case it's always been due to a bright star that is just out of the field of view and causing internal reflections.

Alan

[souls33k3r]

4 minutes ago, RayD said:

Cheers mate, you think the same, it looks like light leak?  I'll have to have a good look over as I cannot for the life of me think where it would get in (apart from the open bit at the front of the telescope of course).

The last thing you want is tinkering with a Tak beauty mate. I'm fairly certain it's light leak because the way the streaks come inwards towards the center. Like i said, cover the front with the scope cap in a dark room and then take a 300s dark frame. You'll quickly find out if there still is light leaking or not. If it is, then at least it's not coming in from the front end but somewhere in the middle of your imaging train.

Next step, take the camera off the scope and cover the front of the camera and take another 300s image, see if you are still seeing this. If so then it's the camera, if not then it's the adapter or the focuser not properly screwed in.

[RayD]

4 minutes ago, alan4908 said:

Occasionally, I've had a similar issue - in my case it's always been due to a bright star that is just out of the field of view and causing internal reflections.

Alan

I didn't give that a thought, Alan.  Alkaid, a mag +1.85 star is in about the location of the issue........I wonder...........

[RayD]

2 minutes ago, souls33k3r said:

The last thing you want is tinkering with a Tak beauty mate. I'm fairly certain it's light leak because the way the streaks come inwards towards the center. Like i said, cover the front with the scope cap in a dark room and then take a 300s dark frame. You'll quickly find out if there still is light leaking or not. If it is, then at least it's not coming in from the front end but somewhere in the middle of your imaging train.

Next step, take the camera off the scope and cover the front of the camera and take another 300s image, see if you are still seeing this. If so then it's the camera, if not then it's the adapter or the focuser not properly screwed in.

I did take a dark this afternoon with the cap on mate, but the scope is outside (I'm in Spain) so it's pretty light.  I'll have a go when it's dark later and see how I get on.  I can try another target also to see whether Alan's theory could be right.

Definitely not spacers etc.  Had the whole thing on the kitchen island today and it is as good and proper as it could be. The only other place possible would be the OAG, but that's also pretty snug and facing directly downwards, so I would expect the light to be at the bottom rather than on a corner as it appears to be.

Clear clear clear skies and imaging time still = 0 

[souls33k3r]

1 minute ago, RayD said:

I did take a dark this afternoon with the cap on mate, but the scope is outside (I'm in Spain) so it's pretty light.  I'll have a go when it's dark later and see how I get on.  I can try another target also to see whether Alan's theory could be right.

Definitely not spacers etc.  Had the whole thing on the kitchen island today and it is as good and proper as it could be. The only other place possible would be the OAG, but that's also pretty snug and facing directly downwards, so I would expect the light to be at the bottom rather than on a corner as it appears to be.

Clear clear clear skies and imaging time still = 0 

yeah now i'm super curious to know what is causing it and what fixes it. Hope you work it out soon mate.

[swag72]

I would have thought of one thing..... a bright star outside of the frame..... but now you mention an IR sensor I would consider that too...... but unless the IR sensor is a new addition, I guess you'd have seen it before if this was the case.  

Perfect test for the bright star theory..... slew somewhere else and take a sub. Easy way to answer that ?

[RayD]

2 minutes ago, swag72 said:

I would have thought of one thing..... a bright star outside of the frame..... but now you mention an IR sensor I would consider that too...... but unless the IR sensor is a new addition, I guess you'd have seen it before if this was the case.  

Perfect test for the bright star theory..... slew somewhere else and take a sub. Easy way to answer that ?

Thanks Sara.  I'll give another target a go tonight. 

No sensor isn't new so, as you rightly say, I would probably have run in to the issue before. However, I've never imaged here with this OTA and camera, so I'll keep it in mind.

[DeepSkyBagger]

Eta UMa (mag 1.9) is 1.8 degrees off the top left corner of your image. Maybe there's something in your rig that could be reflecting the light of that star?

[Stub Mandrel]

Nothing lined up, until I realised your image is mirror reversed top to bottom.

That puts Alkaid pretty close to the centre of the light pattern.

[RayD]

8 minutes ago, Stub Mandrel said:

Nothing lined up, until I realised your image is mirror reversed top to bottom.

That puts Alkaid pretty close to the centre of the light pattern.

Yes that threw me for a bit too, Neil.  I was flicking back and forth from my image to Sky Safari scratching my head, but it does seem to be the most likely candidate.  I certainly hope it is that and not light leakage or similar.

[RayD]

19 minutes ago, DeepSkyBagger said:

Eta UMa (mag 1.9) is 1.8 degrees off the top left corner of your image. Maybe there's something in your rig that could be reflecting the light of that star?

I think tonight I'll select another target anyway as this was actually only for testing, but a suggestion has been made to me to try moving just a small amount as this can sometimes resolve this too.

Amazing that I never even gave this a thought as I've not had it before.  

[PhotoGav]

I think this looks very much like light leak, but from a nearby bright star that is just out of frame. Try moving the compostion of this frame and see if the light patterns change. I had a very similar problem when imaging M109. It turned out to be the nearby bright star, Phad. Here's the thread:

The solution was to alter the framing so that the rays vanished.

[RayD]

Great stuff, thanks Gav.  That looks very similar indeed, so fingers are now firmly crossed that I don't need to panic.

[ollypenrice]

I would drive the scope to put Alkaid in centre field and take a 5 min sub, then mosaic that with the image you have (assuming the FOVs allow overlap.) I have often found that bright stars create artefacts when they are out of shot but not when they are in the field. A number of our mosaics have involved patching off-shot flares with on-shot panels which are flare-free.

Olly

[PhotoGav]

9 minutes ago, ollypenrice said:

I would drive the scope to put Alkaid in centre field and take a 5 min sub, then mosaic that with the image you have (assuming the FOVs allow overlap.) I have often found that bright stars create artefacts when they are out of shot but not when they are in the field. A number of our mosaics have involved patching off-shot flares with on-shot panels which are flare-free.

Oooh, now that's crafty - great tip Olly!

[ollypenrice]

2 minutes ago, PhotoGav said:

Oooh, now that's crafty - great tip Olly!

Born not of craft but of exasperation!!!

Olly

[RayD]

1 hour ago, ollypenrice said:

I would drive the scope to put Alkaid in centre field and take a 5 min sub, then mosaic that with the image you have (assuming the FOVs allow overlap.) I have often found that bright stars create artefacts when they are out of shot but not when they are in the field. A number of our mosaics have involved patching off-shot flares with on-shot panels which are flare-free.

Olly

Thanks Olly, top tip.

[RayD]

Thanks all, you were spot on.  Different target tonight and perfect 

[sharkmelley]

On ‎03‎/‎05‎/‎2018 at 17:52, alan4908 said:

Occasionally, I've had a similar issue - in my case it's always been due to a bright star that is just out of the field of view and causing internal reflections.

Alan

Yes, such artefacts are usually caused by a bright star out of frame.  In your specific case I'm betting on Alkaid, which is very bright and is in that direction.

Mark

[RayD]

18 hours ago, sharkmelley said:

Yes, such artefacts are usually caused by a bright star out of frame.  In your specific case I'm betting on Alkaid, which is very bright and is in that direction.

Mark

Thanks Mark.  Yes I think it was probably Alkaid as moving to another target removed the issue.  I've not imaged again on M51 yet, but will give Olly's suggestion a whirl when I do to see if it resolves it.