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Old 02-01-2012, 03:18 AM
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pmrid (Peter)
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Starlight Xpress H18 CCD - strange problem

I wonder if anyone can help me understand what is happening here.
I have a new Starlight Xpress SXVR_H18 - just received direct from SX as a replacement for the one I received in November that seemed to be defective. Credit to Terry Platt and Michael also for replacing the camera but I see that aspects of the same problem persist in the replacement as well.
I attach 2 images. One is a luminance image of NGC3324 and surrounds. The other is a 10 minute dark taken directly after. The bright stars from the first image are clearly visible in the dark. Also visible in the dark is a terrible light intrusion in the lower left side - probably amp glow of some kind.
The retained image problem is the same one that I encountered in the first camera as well. The amp glow is new though.
I wonder if anyone else with an H18 has any similar problems. And also, whether anyone has any idea what the cause may be.
I am using Maxim 5.15 to capture.

Peter
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Old 02-01-2012, 02:57 PM
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Visionoz (Bill)
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I think gregbradley once mentioned in another thread about RBI - where ghosted image of previous shots are retained by the chip

HTH
Cheers
Bill
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Old 02-01-2012, 03:02 PM
Karls48 (Karl)
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It must be a season for cameras problems.
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Old 02-01-2012, 03:12 PM
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Tandum (Robin)
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There's a thread on CN about this Peter.

That light flash looks more like a light leak than amp glow. Is the shutter closing ok?
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Old 02-01-2012, 04:39 PM
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I've never seen signs of RBI on my H18, Peter. I have a dark library that I built at home and never take darks in the field so maybe my camera has the problem too but I haven't noticed it?

I've been meaning to give this a try since you mentioned the problem, but I haven't had an opportunity yet. If it is clear tonight I will give it a go.

As Robin said, that bright artifact looks more like a light leak. The shutter is not 100% lightproof. Did you cover the end of the scope as well when you took the dark?

Cheers,
Rick.
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Old 02-01-2012, 05:54 PM
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Quote:
Originally Posted by Tandum View Post
There's a thread on CN about this Peter.

That light flash looks more like a light leak than amp glow. Is the shutter closing ok?
Good question about the shutter. Short answer - NO!!
It's a mechanical shutter in which there are 2 leaves that overlap. Have a look at these photos - it shows that the bottom leaf is actually distorted and is jamming against the upper leaf causing it to remain partly open at the pivot end. So it is useless as a shutter, really. And over time, will deposit metal shavings on the sensor and probably lock up entirely. So for the second tome, this camera has to go back. So far, SX are batting 0 for 2. Not a good look.
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Old 02-01-2012, 06:02 PM
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pmrid (Peter)
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Did you cover the end of the scope as well when you took the dark?

Cheers,
Rick.
I found the source of the leak. There is a rubber ring that is sandwiched between the camera faceplate and body and antagonistic screws to adjust tilt as well. The ring is not a nice regularn O-ring but a short length of rubber tube with a plastic clamp holding it into a rough circular shape and when the camera is mounted to the SX filter wheel, there is a visible light gap under that ring. I have now reduced that gap from the manufacturer's starting setting of 95 thou down to 45 thou so the ring is more fully compressed and that may have solved that leak, but the remaining problems of the non-closing shutter and the RBI make this camera a total and very expensive dud. I am hoping that SX wil do the right thing. That have done so far inasmuch as they have actualy replaced camera 1 with camera 2, but from the serial numbers, the replacement is older that the first one and, if anything, has more problems that the first as well.

Peter
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Old 03-01-2012, 02:09 AM
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Peter,

I just took a 300 sec dark immediately after a 180 sec light frame of a bright object (plenty of saturated stars) and can't see any sign of a residual image on my H18. I'll have a closer look at it in the morning...

BTW, got my AO working tonight. It seems to guide very, very well!

Cheers,
Rick.
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Old 03-01-2012, 05:04 AM
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Peter,

I just took a 300 sec dark immediately after a 180 sec light frame of a bright object (plenty of saturated stars) and can't see any sign of a residual image on my H18. I'll have a closer look at it in the morning...

BTW, got my AO working tonight. It seems to guide very, very well!

Cheers,
Rick.
cheers Rick. I had a bit of a play after the moon set. The recommendation from SX to deal with the shutter that won't close has been 'unusual' to say the least. It was to try to jog it closed by running a heap of 1 second lights and if that doesn't do it, then give it a whack with a soft mallet. It is a landmark day when you get advice from a manufacturer to give their expensive product a whack with a hammer. One for the books. I tried both suggestions but neither worked. The shutter still leaves a window open at one end.
To test the residual thingm try doing a Bahtinov mask on something bright - like Canopus and then immediately after, nudge the camera a bit off that target, remove the Baht mask and do another light so you will see both a spikey mask image and a plain non-mask - if it's there that is.
Peter
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