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Old 16-10-2020, 11:11 AM
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Peter Ward
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More sparkles

I'm still trying to get me head around these CMOS thingies. The sensitivity and resolution of the QHY600m is quite remarkable. But the noise floor still remains slightly problematic.

This image is a Sigma rejection sum of 10 sub five minute sub exposures, but as no attempt was made to register the field over three nights, the data was dithered and drizzled all by itself (I had to crop the image due nil overlap in places)

My KAF16803 CCD would have delivered a much smoother background, but no way would it resolved the extent of 47Tuc's halo as well..9 micron pixels look blocky at this FL.

I've uploaded the image at 4k resolution....looks very nice on a 4k monitor
Sorry, no colour, late evening clouds have foiled the colour data three nights in a row...

The link is here
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Old 16-10-2020, 01:19 PM
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What gain and offset are you using?

Which readout mode?

Greg.
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Old 16-10-2020, 02:38 PM
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Quote:
Originally Posted by gregbradley View Post
What gain and offset are you using?

Which readout mode?

Greg.
High Gain mode, Gain 30 offset 20. Attached is a full res crop. No noise reduction applied. Pleasingly there is no fixed pattern noise...just a little
"film grain" which may well dissolve with 20-30 subs.
Attached Thumbnails
Click for full-size image (47tuccrop.jpg)
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Old 16-10-2020, 04:30 PM
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multiweb (Marc)
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Huge fov. Cool.
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Old 16-10-2020, 05:33 PM
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I think you are going to have to experiment with the different modes and gain/offset. One thread I read suggested to do a 0 second bias and adjust the offset until you get 1000adu.

The extended full well mode might be best for something like 47 Tuc with its super bright core.

For what it is worth that fine noise grain seems very much like what I see on my Sony A7riii which has a similar architecture sensor (BSI 42.4mp).

Greg.
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Old 16-10-2020, 05:38 PM
Placidus (Mike and Trish)
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Many, many sparkles Peter. The wide field is wonderful. The two outlying globulars look so meek and mild compared with the Big One.
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Old 16-10-2020, 06:20 PM
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Holy Guacamole, Peter. This is a mind-bogglinlgy spectacular image of 47 Tuc. The crisp fine, detail and contrast are standouts and any perception of noise is completely subordinate to the stunning beauty of this vista. The best image of 47 Tuc I have seen anywhere. Simply wonderful! Can I ask which scope you used for this? The Tak?

By the way, your fantastic Nebula award winning image of NGC 3576 has set admiring tongues wagging down here in Tassie. Of course, you should be called peter AWARD, lol. It's a joy to behold such incredible deep sky imagery.

Cheers,
Richard
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Old 16-10-2020, 07:01 PM
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Quote:
Originally Posted by multiweb View Post
Huge fov. Cool.
Ta Marc...the plan is to go wider...just waiting on an adapter from Precise Parts
Quote:
Originally Posted by gregbradley View Post
I think you are going to have to experiment with the different modes and gain/offset. One thread I read suggested to do a 0 second bias and adjust the offset until you get 1000adu.

The extended full well mode might be best for something like 47 Tuc with its super bright core.

For what it is worth that fine noise grain seems very much like what I see on my Sony A7riii which has a similar architecture sensor (BSI 42.4mp).

Greg.
I wasn't that impressed with the sensitivity in the deep well mode...in any event the core is easily fixed by a couple of shorter subs. I still find it weird users can vary the gain/offset. But agree experimentation is worth while.

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Originally Posted by Placidus View Post
Many, many sparkles Peter. The wide field is wonderful. The two outlying globulars look so meek and mild compared with the Big One.
Ta M&T. The FSQ106 works well with this sensor...which samples the scene beautifully. That said, I'll eventually move the camera up the aperture totem pole once I better understand the value in its various readout modes.

Quote:
Originally Posted by Decimus View Post
Holy Guacamole, Peter. This is a mind-bogglinlgy spectacular image of 47 Tuc. The crisp fine, detail and contrast are standouts and any perception of noise is completely subordinate to the stunning beauty of this vista. The best image of 47 Tuc I have seen anywhere. Simply wonderful! Can I ask which scope you used for this? The Tak?

By the way, your fantastic Nebula award winning image of NGC 3576 has set admiring tongues wagging down here in Tassie. Of course, you should be called peter AWARD, lol. It's a joy to behold such incredible deep sky imagery.

Cheers,
Richard
Thanks Richard. As you may have guessed (but I did mention this on the web page) I used a Takahashi FSQ106 EDXIII As for those glittering prizes...I've shamelessly listed a few of them here along with some other shenanigans.
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Old 17-10-2020, 11:02 AM
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Added in some thin colour data same URL
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Old 19-10-2020, 07:34 PM
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Quote:
Originally Posted by Peter Ward View Post
Ta Marc...the plan is to go wider...just waiting on an adapter from Precise Parts


I wasn't that impressed with the sensitivity in the deep well mode...in any event the core is easily fixed by a couple of shorter subs. I still find it weird users can vary the gain/offset. But agree experimentation is worth while.



Ta M&T. The FSQ106 works well with this sensor...which samples the scene beautifully. That said, I'll eventually move the camera up the aperture totem pole once I better understand the value in its various readout modes.

Thanks Richard. As you may have guessed (but I did mention this on the web page) I used a Takahashi FSQ106 EDXIII As for those glittering prizes...I've shamelessly listed a few of them here along with some other shenanigans.
I had a good look at those images and awards. Amazing stuff, Peter. I vividly recall too, your image of M42 (also published in the calendar) -the Hi-res version on your ATS site was mind-blowing and certainly the best image of the Orion Nebula I have ever seen anywhere. Fantastic work.
The outlook from your observatory (not to mention the equipment within) is magnificent. Thanks for sharing.

Cheers,
Richard
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Old 20-10-2020, 04:49 PM
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excellent shot Peter, interesting regarding the background noise levels though, i thought they were suppose to be super clean above gain 30 - perhaps that was just readout noise and no amp glow... although it might be worth punching out shorter subs as you're dealing with a cmos sensor now..?

cheers

Russell
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Old 20-10-2020, 07:27 PM
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Originally Posted by rustigsmed View Post
excellent shot Peter, interesting regarding the background noise levels though, i thought they were suppose to be super clean above gain 30 - perhaps that was just readout noise and no amp glow... although it might be worth punching out shorter subs as you're dealing with a cmos sensor now..?

cheers

Russell
I'm still working this out as I go, but I suspect read noise and pixel to pixel uniformity are two different things. sCMOS looks to have a novel notion of how to best define read noise, e.g. median or RMS...but with many sensors this can still be a remarkably low number and makes you wonder, despite the disparate numbers, why CCD's still look so smooth.

Here's my take: CMOS have a transistor for every pixel. So each pixel has its own "weight scale".
Which in effect deliver an albeit very repeatable signal (i.e. low read noise) but the overall sensor has a "film grain" pattern to it. (as all the" scales" read a little differently)

Yet a CCD is read-up effectively by one transistor for the entire array.
Just one "scale" that each pixel has to jump on to be weighed. It takes longer, but there is no variation in individual "scale" readings to contend with.
The total signal might drift high or low after a readout and shows as a higher total read noise rather than an embedded "grain" in the sensor.

I'd be more than happy to hear a decidedly more erudite take on the above, from those better versed in electronic engineering than myself

Last edited by Peter Ward; 21-10-2020 at 09:53 AM.
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Old 22-10-2020, 09:35 AM
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Atmos (Colin)
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It's quite a nice wide field there Peter.
CMOS do definitely have a different noise profile, I've never really given it much thought as to what causes this but you've got a solid theory there.
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