Need some help, if possible.

[Stuart1971]

3 minutes ago, teoria_del_big_bang said:

To be honest I too am not that sure but when I first got the camera I did some searching and read several articles about this camera (don;t ask me which - I would have to search again which I might well do bit not tonight) and people were suggesting to use mode 1 and a gain of 56 to take advantage of that big drop in read noise, or some suggested 30 in mode 0 for the same reason.

But when I saw you were using gain 0 I have started to look again now there are more of these cameras out there and looks like a few are now saying Gain 0 mode 1, and they all say offset is not really important but seem to use between 10 and 40.
And  if @vlaiv says use 0 gain that good enough for me so may try this next time, just need to take some more darks for the library if I do but that not an issue plenty of cloudy wet noghts to get those done 🙂 

Steve

Yes looking at that graph, I was using mode 0 and gain 0, which is the highest possible read noise….7.5e..😮no wonder they were bad…

So mode 1 and gain 0 would be 3.5e but Mode 0 and gain 30 would only be 2.5e, and then as you say mode 1 and a gain of 60 it drops again to 1.5e….interesting….

so you used Mode 1 and not mode 0…?

[vlaiv]

5 minutes ago, Stuart1971 said:

This image was taken on mode 0 and gain 0….

My old CCD was the SXVR M25c

You say that you were using 5 minute subs with your old camera?

That camera has twice as large pixel size (x4 by surface) and read noise of ~12e.

If you used mode 0 and gain 0 you had read noise of about 7.5e

According to your old camera, with these settings on new camera you should have used about 6 minute subs. 3 minute subs with gain 0 mode #1 and 1 minute subs with gain 75 mode #1

 

[vlaiv]

Ok, here is image with background removed (no more green cast):

@Stuart1971

Have you tried working on 32bit float point image from APP? You loose quite a bit by going with 16bit.

[Stuart1971]

4 minutes ago, vlaiv said:

Ok, here is image with background removed (no more green cast):

@Stuart1971

Have you tried working on 32bit float point image from APP? You loose quite a bit by going with 16bit.

Looks great, some good detail in there…and no not used 32 bit, will try next time….and will put the linear data 32 bit in Dropbox for you to look at…👍🏼Thanks for all your help….much appreciated…

[teoria_del_big_bang]

8 minutes ago, Stuart1971 said:

Yes looking at that graph, I was using mode 0 and gain 0, which is the highest possible read noise….7.5e..😮no wonder they were bad…

So mode 1 and gain 0 would be 3.5e but Mode 0 and gain 30 would only be 2.5e, and then as you say mode 1 and a gain of 60 it drops again to 1.5e….interesting….

so you used Mode 1 and not mode 0…?

That was my thoughts but I think overall the readout noise is very low for this advanced camera and so probably not too big an issue using gain 0 but I would tend to think mode 1 is the way to go and if your guiding is good then 5 to 10 minute subs, but that also depends on target, whether broadband or narrowband and seeing conditions as well.
So I am still going to give mode 1 gain 0 a go, see if any difference, if I get darks for both prepared I can do a fairly quick comparison next time the snow clouds sod off 🙂 

Steve

[vlaiv]

12 minutes ago, teoria_del_big_bang said:

To be honest I too am not that sure either, I too seem to think I understand it all and then later down the line an not sure why I did think I understood it at all (but that could be my age 🙂 )  but when I first got the camera I did some searching and read several articles about this camera (don;t ask me which - I would have to search again which I might well do bit not tonight) and people were suggesting to use mode 1 and a gain of 56 to take advantage of that big drop in read noise, or some suggested 30 in mode 0 for the same reason.

Again, that is really the question of how much read noise won't cause you any problems.

Here, look at this for example.

3.5e of read noise versus 1.5e of read noise sounds a lot, right?

But imagine that you have LP flux per pixel of say 10e per minute and you image 1 minute subs with 1.5e read noise while you image 5 minutes with 3.5e read noise. You image for one hour total. What will be total noise in each case.

In one minute there will be 10e total LP background and LP noise will be square root of that - so ~3.16227766. These two noises combined will be sqrt ( 1.5*1.5 + 3.1622... * 3.1622...) = sqrt(2.25 + 10) = 3.5e

So first combination gives you 3.5e per sub - and you have 60 subs stacked - so we end up having 3.5 * sqrt(60) = 27.11e of total noise

Let's do the other. Background will be 50e (10e x 5 minutes), so LP noise will be sqrt(50) and we have read noise of 3.5e so total per sub will be sqrt ( 50 + 3.5*3.5) = sqrt(62.25) = ~7.889867e per sub.

We have 12 subs so total will be sqrt(12) * 7.889867 = 27.33e of total noise

Although 3.5e of read noise looks like much more than 1.5e - in reality, if LP is strong enough and if sub duration is chosen accordingly - difference is minimal 27.11e vs 27.33e

 

[vlaiv]

1 minute ago, teoria_del_big_bang said:

That was my thoughts but I think overall the readout noise is very low for this advanced camera and so probably not too big an issue using gain 0 but I would tend to think mode 1 is the way to go and if your guiding is good then 5 to 10 minute subs, but that also depends on target, whether broadband or narrowband and seeing conditions as well.
So I am still going to give mode 1 gain 0 a go, see if any difference, if I get darks for both prepared I can do a fairly quick comparison next time the snow clouds sod off 🙂 

Steve

Just be careful. Narrowband is completely different thing. With NB you seriously cut down any LP that you have and it can't swamp read noise easily.

NB does benefit from lower read noise and longer subs. Here you combine the two - choose gain setting with 1.5e and still do 10 minute subs for best results (CCD cameras with high read noise often used 20-30 minute NB subs because of this).

[Stuart1971]

1 minute ago, vlaiv said:

Just be careful. Narrowband is completely different thing. With NB you seriously cut down any LP that you have and it can't swamp read noise easily.

NB does benefit from lower read noise and longer subs. Here you combine the two - choose gain setting with 1.5e and still do 10 minute subs for best results (CCD cameras with high read noise often used 20-30 minute NB subs because of this).

So would I be better not using my Idas LP filter and letting the LP in to swamp the read noise…?

[vlaiv]

1 minute ago, Stuart1971 said:

So would I be better not using my Idas LP filter and letting the LP in to swamp the read noise…?

It is always better to reduced it. It might mean slightly longer subs if you cut some of it down - but total SNR will always improve if you don't cut signal but you cut down LP.

[Stuart1971]

1 minute ago, vlaiv said:

It is always better to reduced it. It might mean slightly longer subs if you cut some of it down - but total SNR will always improve if you don't cut signal but you cut down LP.

So looking at the graphs I think next time out I am going to try either Mode 0 at gain 30, @ 2.5e … or mode 1 at gain 0 @ 3.5e….🤔🤔

[Stuart1971]

12 minutes ago, teoria_del_big_bang said:

That was my thoughts but I think overall the readout noise is very low for this advanced camera and so probably not too big an issue using gain 0 but I would tend to think mode 1 is the way to go and if your guiding is good then 5 to 10 minute subs, but that also depends on target, whether broadband or narrowband and seeing conditions as well.
So I am still going to give mode 1 gain 0 a go, see if any difference, if I get darks for both prepared I can do a fairly quick comparison next time the snow clouds sod off 🙂 

Steve

What about mode 0 and a gain of 30…??

[teoria_del_big_bang]

39 minutes ago, Stuart1971 said:

What about mode 0 and a gain of 30…??

I think you have to try it and see, to be honest using mode 1 and 56 gain has worked well for me so far on the few clear nights I have had since buying the camera but would like to try gain zero and see for myself what the differences are.
Most of my imaging is with narrowband, although my LP is not too bad, I find LRGB difficult with any any significant moon presence, and sods law the few clear nights here usually do coincide with moon presence., so after vlaivs comment about NB I still may stick with gain 56 for my NB stuff.

Steve

[Stuart1971]

Hmmmm, now I’m confused, which is the correct graph 🤔🤔 is 7.5e or 5.5e the highest read out noise….?? Also the highest read out noise for mode #1 is different too….

 

Edited January 12, 2022 by Stuart1971

[vlaiv]

1 hour ago, Stuart1971 said:

Hmmmm, now I’m confused, which is the correct graph 🤔🤔 is 7.5e or 5.5e the highest read out noise….?? Also the highest read out noise for mode #1 is different too….

That depends - where you found those graphs.

I'd be inclined to trust one published on QHY website. Other one might be early / beta version or something like that.

Alternative is of course to measure camera yourself, but that is somewhat involved.

[Stuart1971]

1 minute ago, vlaiv said:

That depends - where you found those graphs.

I'd be inclined to trust one published on QHY website. Other one might be early / beta version or something like that.

Alternative is of course to measure camera yourself, but that is somewhat involved.

Yes, very involved, easy for you, almost impossible for me….😂😂

just one question based on out chat from a few days ago….

I am hoping to be out tonight and doing 5 min subs, in your opinion based on what we spoke about would I be better using mode 0 and gain 30 or mode 1 and gain 0, as I am edging towards the later….🤔

[vlaiv]

2 minutes ago, Stuart1971 said:

Yes, very involved, easy for you, almost impossible for me….😂😂

just one question based on out chat from a few days ago….

I am hoping to be out tonight and doing 5 min subs, in your opinion based on what we spoke about would I be better using mode 0 and gain 30 or mode 1 and gain 0, as I am edging towards the later….🤔

Yes, go with #1 / gain 0

[Stuart1971]

On 12/01/2022 at 12:59, vlaiv said:

Yes, go with #1 / gain 0

So managed 40 x 5 min subs in high gain mode and gain 0, and this is what I managed, still very noisy, so not sure where to go next, also,it was almost full moon while shooting this…would dithering help…?? Or a different gain setting….? Or just more data..

I still can’t shake the feeling that my old CCD would have done better and cleaner image with the same amount of subs, and yet everyone raves about these IMX571 sensors….🤔🤔

 

[vlaiv]

52 minutes ago, Stuart1971 said:

So managed 40 x 5 min subs in high gain mode and gain 0, and this is what I managed, still very noisy, so not sure where to go next, also,it was almost full moon while shooting this…would dithering help…?? Or a different gain setting….? Or just more data..

I still can’t shake the feeling that my old CCD would have done better and cleaner image with the same amount of subs, and yet everyone raves about these IMX571 sensors…

Well, it does not look bad to me

What were your stacking settings?

[Stuart1971]

1 hour ago, vlaiv said:

Well, it does not look bad to me

What were your stacking settings?

All defaults in APP…?

[tooth_dr]

Hi Stuart. I looked at your Pacman and did feel it was quite noisy for the time but then I see the moon was up so that’s  going to have significantly impacted on the SNR.  Although I’m using the mono version, I’ve settled on mode 1 gain 56

[david_taurus83]

The Iris is faint, very faint, I've tried it a few times from Bortle 6 and never got a good result with either ASI1600MM or my 6D with big pixels. It's definitely a star party type target with dark skies so I don't think your camera is at fault here. Again with the Pacman, was this with just a broadband filter? Most folk use a duo band filter when imaging with the moon and OSC.

[Stuart1971]

2 hours ago, tooth_dr said:

Hi Stuart. I looked at your Pacman and did feel it was quite noisy for the time but then I see the moon was up so that’s  going to have significantly impacted on the SNR.  Although I’m using the mono version, I’ve settled on mode 1 gain 56

Thanks, yes I was not sure what impact the moon would have, but thanks for the comments much appreciated, I might try the those gain settings too with the same 5 min subs..

What sort of length exposure would you use with your settings…?

[Stuart1971]

34 minutes ago, david_taurus83 said:

The Iris is faint, very faint, I've tried it a few times from Bortle 6 and never got a good result with either ASI1600MM or my 6D with big pixels. It's definitely a star party type target with dark skies so I don't think your camera is at fault here. Again with the Pacman, was this with just a broadband filter? Most folk use a duo band filter when imaging with the moon and OSC.

Thanks, again much appreciated, I guess it was not a good first target really, but hey you live and learn….

[Stuart1971]

One question I would like to know the answer too, Dark Flats or Bias frames, or both, I have only been calibrating with Darks, flats and dark flats with this camera, should I be using bias instead of dark flats or as well as…? Also what exposure to use with bias, I know it’s supposed to be the fasted the camera will do….but that is what…??

[The Lazy Astronomer]

37 minutes ago, Stuart1971 said:

One question I would like to know the answer too, Dark Flats or Bias frames, or both, I have only been calibrating with Darks, flats and dark flats with this camera, should I be using bias instead of dark flats or as well as…? Also what exposure to use with bias, I know it’s supposed to be the fasted the camera will do….but that is what…??

Seperate bias frames should not be necessary as the bias signal is contained within the flat darks. 

For information though: the ZWO version has a minimum exposure time of 32 micro seconds, I assume the QHY one is the same. With my ZWO cameras, if I set the exposure time to 0 in the capture software, the camera will use the shortest possible exposures. Again, I assume this would work the same with QHY.