QHY268C Camera Settings - Forums

Topic starter

Jun 7, 2022

Hi folks,

This question goes out to those of you using a QHY268C with the WO Cat 51.

With such a small aperture, what camera settings did you end up settling into, and what helped you determine those settings?

I think I might be consistently under exposing my subs. My goal is to maintain dynamic range, but the histogram is shifted so far into the black that I struggle to surface any detail or nebulosity without also surfacing a lot of noise. I've been relying on the Smart Histogram in SharpCap to help me establish exposure settings, but it seems like I'm consistently coming up short on data.

- Which read mode do you use?
- What are your offset, gain, and exposure time values?
- How did you determine these values?
- Which stacking algorithm do you use?

Any feedback/suggestions are appreciated.

Thanks in advance,

Nikko

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Mr. Ashley McGlone

Jun 8, 2022

I'm interested to see where this thread goes. Almost everything I've read across multiple forums and threads on the QHY268C recommends:
Mode 1 High Gain
Gain 56
Offset 30
USB Limit 10 - optional, a Facebook user said this reduced banding

I have a RedCat 51 and an AT115EDT. See here for my first session with the QHY268C on the bigger scope. As I recently got this camera up and running, I'm interested to see what others have found best for settings.

AstroNikko

Topic starter

Jun 8, 2022

Mr. Ashley McGlone:
I'm interested to see where this thread goes. Almost everything I've read across multiple forums and threads on the QHY268C recommends:
Mode 1 High Gain
Gain 56
Offset 30
USB Limit 10 - optional, a Facebook user said this reduced banding

I have a RedCat 51 and an AT115EDT. See here for my first session with the QHY268C on the bigger scope. As I recently got this camera up and running, I'm interested to see what others have found best for settings.

Thank you! I started out with the same settings for the most part, except I've been using an offset of 12 instead of 30. Which was determined as optimal through sensor analysis in SharpCap. But I don't fully understand how it came up with that value, and from what I've read, that number can be raised or lowered with respect to gain, and can be somewhat arbitrarily set. As far as I understand, it just needs to be set high enough to avoid clipping the black point.

Think I'll push the offset up to 30, and use gain 56 with readout Mode 1 High Gain, as you suggest.

How do you determine your exposure time? With those settings, the Smart Histogram in SharpCap will typically suggest an exposure length of about 25 seconds under my Bortle 4 skies.

Thanks again!

Nikko

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AstroNikko

Topic starter

Jun 8, 2022

Decided to stick with 3 minute exposures tonight using Read Mode 1 High Gain.

The Smart Histogram in SharpCap suggested 7 second exposures at 56 gain for high dynamic range, or 37 second exposures at 0 gain for Unity gain. The moon is pretty bright tonight. So I'm sure the moon glow is driving down those exposure times.

Also went with offset 30 instead of 12 as suggested by the Smart Histogram.

Niko Geisriegler

Jun 9, 2022

Hello AstroNikko!

I have a 268M- is a little more sensitive but will also hold out for some settings.
I also have a Bortle 4-3 sky at home and it is actually so, the brighter your sky is the shorter your single exposure time. The Bortle 4 are only valid for new moon.
The suggested time from the smart histogram can be used as the minimum exposure time. If I now use the optimal exposure time calculator with NINA, a somewhat higher exposure time is given there.
I have settled in high gain mode at the values Gain 0 with offset 90 and Gain 60 offset 120 - this works quite well.
For the offset you only need to make sure that the min value of the histogram is clearly off the left edge (for me approx. 1550). once you have found your value, you can continue to play with the actual length of a light.
Anyway, your rosette nebula doesn't look so bad.
The redcat is also a diva when it comes to focusing. you have to be very sensitive - with the rosette nebula it seems to me as if you were not completely in focus and you can still reduce the green cast a bit.
In our German-speaking area Daniel Nimmervoll has extensively tested the color version of the camera and you can possibly copy his settings in his videos.

Hope that has helped you now and continue to have fun with your equipment.
CS Niko

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AstroNikko

Topic starter

Jun 11, 2022

Niko Geisriegler:
Hello AstroNikko!

I have a 268M- is a little more sensitive but will also hold out for some settings.
I also have a Bortle 4-3 sky at home and it is actually so, the brighter your sky is the shorter your single exposure time. The Bortle 4 are only valid for new moon.
The suggested time from the smart histogram can be used as the minimum exposure time. If I now use the optimal exposure time calculator with NINA, a somewhat higher exposure time is given there.
I have settled in high gain mode at the values Gain 0 with offset 90 and Gain 60 offset 120 - this works quite well.
For the offset you only need to make sure that the min value of the histogram is clearly off the left edge (for me approx. 1550). once you have found your value, you can continue to play with the actual length of a light.
Anyway, your rosette nebula doesn't look so bad.
The redcat is also a diva when it comes to focusing. you have to be very sensitive - with the rosette nebula it seems to me as if you were not completely in focus and you can still reduce the green cast a bit.
In our German-speaking area Daniel Nimmervoll has extensively tested the color version of the camera and you can possibly copy his settings in his videos.

Hope that has helped you now and continue to have fun with your equipment.
CS Niko

Hi Niko!

Nice to meet another Niko/Nikko

Thanks for the feedback. It reaffirms some of my current understanding. I was surprised to see you using offset values that are that high, though. It's given me the confidence to experiment more, and push those values further with higher gain values.

The Cat 51 is a diva for sure. It's always a challenge dialing in the focus with the helical focuser, and keep it there. Focus slips easily, even with the tension ring. I was surprised when you mentioned the Rosette being out of focus. I didn't remember it being out of focus. But now that you mention it, I do remember it was the second target of the night, and I only checked focus at the start of the night. I need to be more diligent about checking focus throughout the night.

Around that same time, I was also struggling to resolve field tilt. I think I attributed most of the focus issue to field tilt. I ended up sending the scope out for servicing, but I haven't evaluated tilt yet since I got it back. Still something I need to do.

Thanks again for all the feedback. I appreciate it.

Clear skies,

Nikko

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