Gain in Moravian C3 - Forums

Topic starter

Apr 13, 2024

Hi everyone,

What gain you typically use with Moravian C3-61000 PRO ?

When using ZWO ASI6200mm , gain 100 turns on HCG high gain mode. So what is the equivalent gain on Moravian C3 to turn on HCG high gain mode?

Bill McLaughlin

Apr 13, 2024

Moravian specs gain differently numerically. This is from the C3 product page...

Dark Matters Astrophotography

Apr 13, 2024

Gain 0 for broadband and 2750 for NB.

Daniel Carter

IOTD Staff

Apr 13, 2024

Gain 0 for broadband and 2750 for NB.

I use the same Gain values for broadband and NB with my Moravian C3-26000 (ASP-C instead of full frame) and that has worked out well for me. I based those gain values off of the same information that Bill posted from Moravian's product page.

Well Written

Wolfgang Promper

Apr 13, 2024

2750 for everything

Jon Rista

Apr 13, 2024

Gain 0 for broadband and 2750 for NB.

This is what I would do as well, unless you explicitly want very short LRGB exposures. If you want more reasonable LRGB exposures and frame counts, then I'd use gain 0 for that. You will get about half a stop more dynamic range, as well as a significantly larger well capacity, so you'll be able to expose for a good deal longer (probably a lot longer than necessary to swamp the read noise, which is a real bonus... That probably wouldn't quite be the case at 2750 for broadband.)

Dark Matters Astrophotography

Apr 13, 2024

Jon Rista:
Gain 0 for broadband and 2750 for NB.

This is what I would do as well, unless you explicitly want very short LRGB exposures. If you want more reasonable LRGB exposures and frame counts, then I'd use gain 0 for that. You will get about half a stop more dynamic range, as well as a significantly larger well capacity, so you'll be able to expose for a good deal longer (probably a lot longer than necessary to swamp the read noise, which is a real bonus... That probably wouldn't quite be the case at 2750 for broadband.)

In my case, with the C5A-100M (same gain values) the subs are 300mb each. You don't want to live through stacking hundreds and hundreds of them. 🤯

Bob Lockwood

Apr 13, 2024

I'm glad all this came up as I just got a C3-61000 Pro and have a C3-26000 Pro on the way. Why would you not just leave it at 0 for both BB and NB
if exposure time is not an issue. I'll experiment, but plan to just stay at 0 gain.

Dark Matters Astrophotography

Apr 13, 2024

Bob Lockwood:
I'm glad all this came up as I just got a C3-61000 Pro and have a C3-26000 Pro on the way. Why would you not just leave it at 0 for both BB and NB
if exposure time is not an issue. I'll experiment, but plan to just stay at 0 gain.

The read noise is significantly lower at 2750 and there's no real drawback with NB.

Rafael Sampaio

Topic starter

Apr 13, 2024 · Edited: Apr 13, 2024

Using 0 gain means not only longer subs, but a much longer total exposure time needed, comparing when using 2750 (HCG) gain. Right?

Or wrong?

Dark Matters Astrophotography

Apr 13, 2024

Rafael Sampaio:
Using 0 gain means not only longer subs, but a much longer total exposure time needed, comparing when using 2750 (HCG) gain. Right?

Or wrong?

No. You're still going to swamp the noise fairly quickly, you'll just have less saturated stars, which is why I use Gain 0. I want to prevent images with great extended objects but white washed out looking stars.

Bob Lockwood

Apr 13, 2024 · Edited: Apr 13, 2024

To me, leaving it at 0 for broadband keeps the well depth as high as it can go, exposure time for me is not an issue, I typically do 10-15 minutes all the time.
For NB I guess going with 2750 will help with read noise and having the well depth drop to about 17k won't matter much with over saturation.

Roger Gifkins

Apr 14, 2024

2750 for everything with my C3 26000C

Ani Shastry

Apr 14, 2024

Bob Lockwood:
I'm glad all this came up as I just got a C3-61000 Pro and have a C3-26000 Pro on the way. Why would you not just leave it at 0 for both BB and NB
if exposure time is not an issue. I'll experiment, but plan to just stay at 0 gain.

The read noise is significantly lower at 2750 and there's no real drawback with NB.

Hi @Bill Long, given the ginormous 300MB sizes of the subs with the C5A-100M, I would be curious to hear if you have tried binning 2x2 (and in particular whatever Moravian calls “hardware” binning which course isn’t like CCD HW binning in terms of read noise) and running at gain 2750 for broadband?

I assume that the full-well capacity would be 4x higher, and so less likely to saturate stars even in broadband with gain 2750?

Willem Jan Drijfhout

Apr 14, 2024

So far have only been using my C3-61000 Pro for a few weeks, all BD at gain 0. For NB I would default to 2750. The best settings will probably be different for different situations. It’s a balance between noise (or signal to noise) at the low end and saturation on the high end. I’ve found that my system (f/7.2) even at gain 0 does not easily saturate, so might even try 2750. For NB I would not see much benefit of gain 0 on my system. But if you have a very fast system, this may be very different and a gain 0 for both NB and BD might work best?

Dark Matters Astrophotography

Apr 14, 2024

Ani Shastry:
Bob Lockwood:
I'm glad all this came up as I just got a C3-61000 Pro and have a C3-26000 Pro on the way. Why would you not just leave it at 0 for both BB and NB
if exposure time is not an issue. I'll experiment, but plan to just stay at 0 gain.

The read noise is significantly lower at 2750 and there's no real drawback with NB.

Hi @Bill Long, given the ginormous 300MB sizes of the subs with the C5A-100M, I would be curious to hear if you have tried binning 2x2 (and in particular whatever Moravian calls “hardware” binning which course isn’t like CCD HW binning in terms of read noise) and running at gain 2750 for broadband?

I assume that the full-well capacity would be 4x higher, and so less likely to saturate stars even in broadband with gain 2750?

I haven't seen a way in their driver to use this mode. I'll have to double check and see if I can find it. If I can it's certainly worth a test.

Bill

Wolfgang Promper

Apr 14, 2024

Ani Shastry:
Bob Lockwood:
I'm glad all this came up as I just got a C3-61000 Pro and have a C3-26000 Pro on the way. Why would you not just leave it at 0 for both BB and NB
if exposure time is not an issue. I'll experiment, but plan to just stay at 0 gain.

The read noise is significantly lower at 2750 and there's no real drawback with NB.

Hi @Bill Long, given the ginormous 300MB sizes of the subs with the C5A-100M, I would be curious to hear if you have tried binning 2x2 (and in particular whatever Moravian calls “hardware” binning which course isn’t like CCD HW binning in terms of read noise) and running at gain 2750 for broadband?

I assume that the full-well capacity would be 4x higher, and so less likely to saturate stars even in broadband with gain 2750?

I haven't seen a way in their driver to use this mode. I'll have to double check and see if I can find it. If I can it's certainly worth a test.

Bill

I think you need to set that in the .ini file

John Hayes

Frequent contributor

Apr 14, 2024

Ani Shastry:
I assume that the full-well capacity would be 4x higher, and so less likely to saturate stars even in broadband with gain 2750?

No, it doesn't quite work that way and that's the problem with binning in hardware with a CMOS camera. They only transfer 16 bit values for each pixel so they typically-left shift the sum by 2 bytes to the left to produce an integer average of the value. That strategy does give you more effective well depth at the expense of loosing 2 bytes of data resolution when you bin. The only way to avoid that is to download the data binned 1x1 and then do a local 2x2 software bin in floating point. The IntegerResample in PI will do this. Of course this doesn't address the bandwidth problem. Even if you downloaded a longer word for each pixel--say 32 bits, you end up with just as much data being transferred. QHY claims to have an 18 bit download option but I believe that you have to write your own code to use that option. It's not something that any current astro-software will deal with (at least that I know of.)

John

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Rafael Sampaio

Topic starter

Apr 15, 2024

John Hayes:
Ani Shastry:
I assume that the full-well capacity would be 4x higher, and so less likely to saturate stars even in broadband with gain 2750?

No, it doesn't quite work that way and that's the problem with binning in hardware with a CMOS camera. They only transfer 16 bit values for each pixel so they typically-left shift the sum by 2 bytes to the left to produce an integer average of the value. That strategy does give you more effective well depth at the expense of loosing 2 bytes of data resolution when you bin. The only way to avoid that is to download the data binned 1x1 and then do a local 2x2 software bin in floating point. The IntegerResample in PI will do this. Of course this doesn't address the bandwidth problem. Even if you downloaded a longer word for each pixel--say 32 bits, you end up with just as much data being transferred. QHY claims to have an 18 bit download option but I believe that you have to write your own code to use that option. It's not something that any current astro-software will deal with (at least that I know of.)

John

Hi John! Thanks! And do you usually use gain for broadband?