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Old 02-12-2018, 11:24 AM
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Sensor motes

I took a single 10 min sub of M42 last night with my FSQ-106 and SX M26C OSC cam. It was only ever intended to check the cleanliness of the imaging train (M42 dissappears behind trees for me for most of the night).

Judging by the crispness of most of the motes seen in the image (which flats are correcting), would the likely position of these motes be on the chamber window or actually on the sensor itself? I checked the UV/IR filter (spaced 60mm away from the sensor - I use a 67mm UV/IR right in the CAA, rather than at the camera)

I recently pulled the cam apart to clean a grease streak on the window, so it's either that I think, or on the sensor itself (a loupe and a torch aren't revealing anything obvious, nor is using a UV torch)

No need to comment on the noisy nature of this SINGLE 10min sub...it's not even processed apart from an auto-stretch in PI (no flats, darks or biases nor anything else) I also notice I didn't fully get the streak, as evidenced by the small spikes on some stars
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Old 02-12-2018, 11:27 AM
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Sharp enough to be on sensor but if it's sealed unlikely. Just wipe window with a wet Q tip.
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Old 02-12-2018, 11:29 AM
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Here is M78 with flats applied (also a single 10min sub only), so it does remove them.
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Old 02-12-2018, 11:29 AM
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Quote:
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Sharp enough to be on sensor.
I think so too...disassemble time again
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Old 02-12-2018, 11:31 AM
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I think so too...disassemble time again
Try the chamber window first then do some flats to check. Also dust on filters.
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Old 02-12-2018, 11:33 AM
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Quote:
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Here is M78 with flats applied (also a single 10min sub only), so it does remove them.
Yeah but if you don't dither you'll be missing stars on widefields, possibly obliterating entire civilisations.
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Old 02-12-2018, 11:37 AM
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Yeah but if you don't dither you'll be missing stars on widefields, possibly obliterating entire civilisations.
Marc, it's ONE shot...dither what?

For my main image, yes, I dither every single sub. Only managed 1 hr before the high level clouds came back...and early morning storms here...
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Old 02-12-2018, 11:40 AM
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Here is NGC 2014 (and a few dozen others) as a 1 hr compile, using full calibration too. Needs a LOT more data...

I can JUST see the bubble in the original non-reduced...SO much noise (and SO many LP gradients I had to remove).
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Old 02-12-2018, 11:42 AM
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Marc, it's ONE shot...dither what?

For my main image, yes, I dither every single sub. Only managed 1 hr before the high level clouds came back...and early morning storms here...
Then they're all dead...
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Old 02-12-2018, 12:00 PM
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Sharp motes like that would indicate dust on the cover of the sensor - as suggested by Marc.
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Old 02-12-2018, 12:00 PM
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Then they're all dead...
Hey, I am only adhering to Starfleet's Prime Directive
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Old 02-12-2018, 12:06 PM
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This is a single flat, stretched to show the faint motes (much further away from sensor given the shape, grey-scale etc) and the sharper motes (i.e lint and hair )

Yup, time to clean again...
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Old 02-12-2018, 03:32 PM
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Some nice dusty stuff there, Lewis

I agree that the small ones are clearly very close to the sensor. Here's a formula that you can use to work out the distance: http://www.wilmslowastro.com/software/formulae.htm#Dust

Cheers,
Rick.
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Old 02-12-2018, 04:23 PM
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Rick,

Thanks!

The darker, well focused motes are generally between 0.76 and 1.8mm from sensor, indicating the sensor cover itself, and the usual round out of focus motes would seemingly indicate the chamber cover, at 5 ~ 6.5mm distance.

So, clean time
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