QHY8 OSC Camera Problem

[TrevorW]

Light leakage or something else :question:

attached image is a stack of 11, 10 minute frames with auto levels only applied no other processing taken on a warm night 23/11

I ran a series of darks (lens cap on) (indoors with the air-con on) today from 90 seconds to 10 minutes and still the same issue, each frame showed a bright band at top

Last time I used the camera was in mid October without an issue

The camera is on the way back to Theo for a check :thanx:

[wasyoungonce]

Although probably not the problem...but..plastic lens caps do pass some wavelengths of IR energy....which is seen on the sensor as light!

[TrevorW]

The camera was facing down on a flat surface sitting in a dark cloth

[wasyoungonce]

Didn't think you would be caught buy that oldie and the problem doesn't look like leaking IR energy..:thumbsup:

So, I'll go back to sleep now.

[TrevorW]

Well Theo checked the camera and it appears to be a light leakage, caused by the camera LED light leaking onto the CCD, via a gap which has formed when the foam which surrounds the CCD has somehow shrunk over time

better safe than sorry

[wasyoungonce]

That has got to be a first!:eyepop:

Amazing, nice to see Theo on the ball!:thumbsup:

[TrevorW]

Well I got my camera back but I'm not to sure

Theo said he did some 3 minute darks and they were fine

but with my gain and offset setting 3 and 109

I'm still getting a bright band appearing at the top of each frame

any clues anyone :question::screwy::thanx:

[peter_4059]

Do you get it if you turn the gain down to 0 or 1?

[TrevorW]

Having tried 0 or 1 Peter, the gain offset setting were the ones I've always used

Thanks

[peter_4059]

"On a CCD Labs Q8-HR I have, even at gains of 0 and 1 (on its 0-63 scale), the camera would hit 65535 on bright objects (like the ceiling above my desk). There's no point in running this camera at gains higher than 0 or 1.

Why is there no point? The camera only holds 25k e-. If a gain of 0 or 1 gets me to 0.38 e-/ADU (so that those 25k e- become 65535), running at 0.1 e-/ADU will only serve to limit my dynamic range. Each single electron already comes out to more than 2 ADU."


http://www.stark-labs.com/blog/files/GainAndOffset.php

"Since this time, QHY has gone on to
create a wide range of cameras and CCD
Labs acts as a VAR (Value Added Reseller)
for the cameras (a number of other dealers
act as resellers or VARs as well, including
Starizona in the USA). One camera, the
QHY8, is sold through CCD Labs as the
Q453-HR (formerly the Q8-HR) and a
second, the QHY2-Pro (not to be confused
with the entirely different QHY2), is sold
through CCD Labs as the Q285-M. CCD
Labs provides the cameras with additional
capture and processing software, an install
disk with a manual, assembles the cameras,
does a full quality control check before
shipping to customers, and seals the CCD
chamber following an argon purge to keep
it nice and dry."

http://www.stark-labs.com/craig/articles/assets/CCDLabs_ATT.pdf

[Shiraz]

dont know if it is any use, but I saw a similar effect when the wiring to my Peltier failed - however, in my case it was only transient, occuring on one frame as the chip heated up.
Might be worth a look at the cooler and its connections/power supply to make sure that it is drawing reasonable current - could be a high resistance somewhere in the circuit or maybe the Peltier itself has partially failed. If it's not light leakage, it must be heat. all the best Ray

[TrevorW]

Thanks Ray

a process of eliminating all variables

it has been suggested by Theo that it could be a power supply problem

before I install the drivers again

I'll

a) test in a completely dark environment (no ambivient light whatsoever)
b) allow the camera to cool and then disconnect the power to the peltier (the camera has been back to Theo so I assume he has checked that the peltier is cooling)
c) don't know about changing the gain as this has never previously been an issue

[TrevorW]

Well I tried it in a draw with my gain and offset settings and all the darks (up to 10 minutes where fine) to dark actually I thought something may be wrong (run for 1hr roughly)

so I took it out and did a one second focus to see if it was working (bright image as expected)

shut everything down and switched it off for 10 minutes

then I thought I'd try it out of the drawer face down on a table in my study with a light on, with some Alfoil wrapped around the nosepiece
darks are still dark

I really don't know what's going on here

I'll have to wait for another clear cool night to get it outside for another test

[Shiraz]

Aaaugh - an intermittent. At least that rules out stray light - it's a power problem.
I would have a good look at the cables and maybe replace the main power lead - those wires look fairly fragile. My problem was poor soldering inside the camera, but I wouldn't open that up unless there was no other option. Probably worth checking with Theo again, now that the symptoms have changed - he knows everything there is to know about these cameras. All the best, Ray