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Blooming on QSI 660i (Sony ICX694)?


Gib007

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Hi all, I'm just wondering if I'm getting some blooming on my QSI 660i (Sony ICX694). There shouldn't be any, since it is an anti-blooming sensor, but perhaps there's a fault in it or something. I've e-mailed the raw FITS file to QSI to check but just wondering what some of you here think. 

The following is a full-size Luminance image. It is a single 5 minute 1x1 exposure that has been calibrated quickly with 5 flats and 20 bias:

QSI660i_Luminance_300s_1x1_zps33dcff91.j

Circled on the top-left corner are what look like bloom trails. Mind you, see how much brighter stars do not have any blooming. This is an enlargement of the same:

QSI660i_Luminance_300s_1x1_Enlarged_zps7

There is a little bit of coma in my image but I just need to play with the Borg focal reducer to get it just right. I highly doubt this coma is related but I cannot discount it as the blooming only seems to appear very near the edges of images but clearly not in all the stars.

As a further example, here is the centre-right side of an Oxygen-III narrowband exposure of the same (single 5 minute 1x1 exposure quickly calibrated with 5 flats and 20 bias):

QSI660i_OxygenIII_300s_1x1_Enlarged_zps6

Keep in mind this is narrowband! Also, much, much brighter stars show no such effect. Operating CCD sensor temperature for these exposures was -10°C. Thanks for any opinions you may have. 

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It isn't blooming, that occurs (or CAN occur with some sensors) when the pixel well-depth is exceeded and there is no anti-bloom gate to stop electrons bleeding over into the next one. None of that applies here. I suspect what you have there is some internal reflection.

ChrisH

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It isn't blooming, that occurs (or CAN occur with some sensors) when the pixel well-depth is exceeded and there is no anti-bloom gate to stop electrons bleeding over into the next one. None of that applies here. I suspect what you have there is some internal reflection.

ChrisH

Indeed, and I guess blooming would be insanely bright and quite significant, particular on the bright star. 

Coincidentally, now that you mention internal reflections, I was using a Hutech IDAS LPS filter right in front of the focal reducer. A friend of mine was doing the same and uses the same telescope and same camera, but didn't get any of this. That's odd. 

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Indeed, and I guess blooming would be insanely bright and quite significant, particular on the bright star. 

Coincidentally, now that you mention internal reflections, I was using a Hutech IDAS LPS filter right in front of the focal reducer. A friend of mine was doing the same and uses the same telescope and same camera, but didn't get any of this. That's odd. 

Ah. I had to stop using mine with the 10" SCT entirely because of reflections but so far not too much of a problem with the refractor - except with the 0.8x reducer. It is very prone to picking up internal (forward) reflections and throwing them back at the sensor. Maybe you can spot something inside that is not well blackened?

ChrisH

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