Has anyone seen this effect

[JSeaman]

I haven't seen this before, every picture I take is showing a band (see attached between the two lines) where I have half of the image as I would normally expect and half dark

Has anybody seen it? There is no obvious defect on the glass or sensor that I can see

James

[ollypenrice]

We need to know camera, filters, filterwheel etc.

That's an odd one. Is the frontier between light and dark in exactly the same place in each sub?

Often problems of electronic origin tend to follow the X and Y axes of the pixel array. That isn't the case here so I suppose it could be optical. If so it's a reasonably well focused artefact suggesting something close to the chip. Does your camera have a shutter? Could it be sticking?

Olly

[MarsG76]

No.. interesting... looks too "focused" to be close to the sensor but too sharp for a gradient...

I'm also curious what could cause this effect.

[JSeaman]

No filters, QHY8L, no shutter

The 'frontier' stays the same

To add to the confusion, after 40 minutes of bad subs, I moved to M42 and it has gone?! I was on Rosette before so haven't moved far

[MarsG76]

Only thing that comes to mind is perhaps some light reflecting withing the optical system? 

Were there any bright light sources in the direction of the Rosette, for example a neighbors bright light, even if on only for a moment?

[gonzostar]

Dont know what scope you are using, However i got similar streaking with the C8. Mainly imaging low targets and light  from neighbours conservatory getting through dew shield? 

[JSeaman]

No I thought the same thing, I got the effect 4 times on 10 minute subs. I decided the only logical thing to do was move back of M42 to Rosette and ... it returned.

I've attached the 10 minute M42 directly followed by the 10 minute Rosette (with plane and weird effect)

Now trying Leo Triplet...

[JSeaman]

Scope is an Evostar ED80, I have done this target recently and seen no strange effect so fundamentally something has changed and it is a repeatable failure. In terms of the position in the sky, Rosette and M42 are pretty much the same so I'd expect it to be a common phenomenon (e.g. neighbours' lights) but it isn't. I'll see what Leo throws up ..

[MarsG76]

9 minutes ago, JSeaman said:

No I thought the same thing, I got the effect 4 times on 10 minute subs. I decided the only logical thing to do was move back of M42 to Rosette and ... it returned.

I've attached the 10 minute M42 directly followed by the 10 minute Rosette (with plane and weird effect)

Now trying Leo Triplet...

Clouds or haze perhaps? Low pressure front colliding with high pressure???

[gonzostar]

I am left scratching my head to. Will be interested to see how the Leo Triplet turn out. Sound like you have nice clear skies up north. I have unwanted early clouds at moment blocking the Leo Triplets! 

 

[Stub Mandrel]

Moonlight gradient is my bet, I also see it a lot with LP here.

Our friends with glorious skies won't see it.

I find that on my initial stretch of such stacks you can vary the position and definition of the line quite easily in DSS, I don't know why stretching in DSS gives such a striking cutoff, but it can.

Raising the background enough that it is all 'grey' seems to be the best strategy, then in PS lift the black point and apply gradient exterminator.

 

Edit - Rosette is half the distance from the moon that M42 is and by the look of it the direction to the moon is at 90 degrees to the band.

 

Also moon is showing a halo tonight, could it be a 22 degree halo?

[JSeaman]

Clouds wouldn't be in the same place on 4x10 minute shots, haze would vary too

Leo Triplet came out fine (well, one of the three at least!)

Clear skies end in about 20-30 mins which will give me just enough time to have taken 1 picture

My first thought was the moon but that would hit M42 as they are in the same place (near enough)

It seems my scope has fallen out with Rosette!

[carastro]

I have an idea.  This is a QHY camera.  I had something similar happen to my QHY5 guide camera, and I discovered what it was.  Orientation and gravity can play a part if this is the same cause.  

QHY seem to put foam inside the cameras and I found the foam had slipped on my QHY5 obscuring part of my guide screen.  I wondered what on Earth was going on at the time.  The picture you posted up of the Rosette with the yellow diagonal band looks very much like my guide screen looked.

When you tip the camera in a different direction, the foam slips back into place.  Might be worth taking a look.

I posted up a question on the QHY forum and Mr QHY said it was OK to remove it if need be.  I haven't done so yet as my foam is now staying in place.

Carole 

[JSeaman]

Thanks Carol, was this foam covering the sensor? 

The orientation of the scope was fairly similar for a couple of targets but I won't rule it out.

I managed 40 minutes before the clouds rolled in eventually!

[carastro]

Yes when I looked inside the QHY5 after that occasion, the foam was sticking out and covering part of the sensor.  I pushed it back and it seems to have been OK since.   Obviously as a guide camera I was only doing 1sec exposures and could not understand why I couldn't see the bottom left corner of the screen it was fuzzy.   In much longer exposure and with tracking, I guess you would see some stars between the porousness of the foam.  

It's worth a look, but if that is the case on your camera, you might have to tip it in different orientations to see whether any foam falls out intermittently as it seems to happen only on some targets.  

Carole 

 

[JSeaman]

Thanks, I think I can rule that one out though. I looked down the scope and could see very clearly the sensor was fully visible with no obstructions. I'm at a bit of a loss, I guess I'll simply try Rosette on the next clear night and see if it was transient

[carastro]

Quote

 I looked down the scope and could see very clearly the sensor was fully visible with no obstructions.

You mean at the time it happened?

OK, well just a thought.  Let us know if you find out the cause.

Carole 

[carastro]

I am sure you will have sussed out these, but floppy dew shield?  Observatory roof in the way? I get that occasionally if the POD roof is in the way.

Carole 

[JSeaman]

Yes the first thing I did was have a look down the OTA for marks and it gives a nice magnified view of the sensor which was unobstructed (I thought it might be icing or something but no)

Dew shields are all tight and there is no roof to get in the way so sadly I'm at a loss too!

I just noticed Neil's edit and I guess the moon could possibly have been having an effect. I'll update following the next clear night - probably November!

[SteveA]

Are you using an OAG?

If so...and its quite common (at least for me!) is the OAG prism is impinging on the optical path to such a degree that it's  preventing full illumination of the sensor. This would necessitate moving the prism further out of the optical path.

Steve

[SteveA]

I should have asked also.....does it appear in any flats you take?

[JSeaman]

Sorry no OAG and I didn't take flats last night but I've never had it before

[ollypenrice]

You could try rotating the camera between subs just to eliminate anything environmental. Does the gradient track the camera or track the sky?

Olly

[JSeaman]

I'm not sure on that, if it breaks again I will check

Thanks again for all the feedback

[carastro]

You saw all that snow on its way, that was what it was!!!