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Old 31-03-2018, 08:33 AM
LewisM
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Sony sensor issue

The following tri-channel image splits are from a Sony sensor OSC CCD that I obtained 2nd hand. As you can see, there is a significant issue with the centre of the sensor, notably blocking the red (with some blocking of blue and green).

I have been messaging directly with the manufacturer, and the current suggestion is the sensor was directly exposed to extreme light (like solar imaging WITHOUT any filtering) or there is contamination on the cover slip (seems to me that occurring dead centre is a statistical near improbability). The manufacturer wishes to take it back to inspect, and has noted that sensor replacement is likely.

Any opinions on what may be the issue here? The manufacturer has confirmed that the effects being seen are NOT that of moon light pollution (these were taken at 94% moon) but a sensor issue of some sort.

NOTE: these are unprocessed, non-calibrated files - no flats, darks or bias, so it is NOT calibration file over-correction.
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Last edited by LewisM; 31-03-2018 at 08:44 AM.
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Old 31-03-2018, 10:35 AM
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billdan (Bill)
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That looks like what happens to my QHY12 when the glass window starts to dew up on the front. A small dew heater eliminates it.
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Old 31-03-2018, 12:33 PM
LewisM
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Manufacturer says not the case as it is present in daylight images too, so I either send it to them for inspection, or return to the seller. At this stage, i will continue talking to the manufacturer.
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Old 31-03-2018, 01:52 PM
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Slawomir (Suavi)
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In 1996 in one of SOHO's cameras the shutter remained jammed open for a few hours and this left only a slight burn on the CCD, caused mainly by XUV light that is anyway strongly absorbed by atmosphere and requires vacuum for transmission. But SOHOs sensors are mono and yours is an OSC, therefore it seems plausible, that the colour filter array on top of the CCD (that was made from gelatine/pigment/dye etc) got damaged from the heat from exposure to solar radiation. Most damage would most likely occur at the centre where there is the most intensity of light falling on the sensor and it would take longer to dissipate heat from that part of the CCD.

Another good reason to use mono cameras for astroimaging
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Old 31-03-2018, 01:55 PM
LewisM
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Manufacturer says it is light damaged.

Suavi, I simply don't have the time (or patience) to use mono any more.

Imaging is a hobby for me, for my enjoyment, not for the publishing of pretty pictures, so OSC works just fine for my needs. I have had mono (3 in fact), but come back to OSC (and now incorporate H-a and OIII)
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Old 31-03-2018, 02:33 PM
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I understand Lewis. I am sometimes tempted myself to try OSC - have had very little time to use my rig. Please keep us posted with developments with the sensor. Would it be possible to ask the previous owner whether he/she was doing solar imaging without any filters?
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Old 31-03-2018, 04:03 PM
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Shiraz (Ray)
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Maybe have a read of this Lewis - I understand that you did not use flats, but the effects from internal reflections described by Alan Holmes look similar to what you are getting.

http://diffractionlimited.com/flat-f...ur-telescopes/

Last edited by Shiraz; 31-03-2018 at 09:28 PM.
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Old 31-03-2018, 05:34 PM
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That is a great article, thank you Ray.
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Old 31-03-2018, 05:35 PM
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Lewis, if you’re in it for enjoyment, get yourself one of the cameras based on the IMX294 chip, abut the same size but way better SNR...
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Old 31-03-2018, 06:36 PM
LewisM
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Thanks Ray - very interesting, and I had read it before.

I don't get this issue with my SBIG STF-8300 - in fact, the field is very evenly illuminated (despite the weird "WTF" sub a few weeks back ). Months ago, I had painted all my black anodised internal Tak adaptors, and redid them all recently with Black 2.0 ultra-flat black paint. No internal reflections to speak of, and I have shone 240 lumens down there, as well as a 500 lumens torch. Didn't see anything to worry about at all and NO light leaks in the system I could perceive, with the STF-8300 anyway. Maybe with this cam?.

The CCD is a Starlight Xpress M26C. Terry Platt has been VERY forthcoming and helpful and he is of the belief it is a damaged matrix on the sensor. During image download and in pure greyscale, the issue is not at all noticeable - nice, even field (hence why I kept going with 5 hrs data!). It was not until I debayered did I shout the profanities (I did try stacking mono, and unfortunately it does show the "donut" after stacking them all). This leads both Terry and myself to the conclusion the red on the bayer matrix is damaged, and red seems the most susceptible to strong UV.

I await Terry waking up again and seeing my bunch of FITS and more testing and see what he says. It is NOT worth my while having the CCD replaced as it will cost more than what I paid for the cam. I will supply more day shots, uncooled shots, cooled shots and a plethora of night shots. Then make a decision - but it's sadly not looking good, which is a shame as the images are otherwise incredible - next to no noise, lovely contrast, big field.
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Old 11-04-2018, 06:59 PM
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Gone back to Starlight Xpress for assessment and repair, so here is fingers crossed for a speedy and not-costly recovery.
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