Qhy268m with 135mm Samyang lens

[assouptro]

Hi all

A quick one, has anyone used this combo? 
I have the lens attached to the camera and the distance is good, aberration detector looks good in all corners now 

I am going camping this weekend to a dark site and it looks like there is going to be a clear sky for the first half of Friday night, I don’t want to waste my subs by over or under saturating them, can anyone help me decide a sub length at f2.8? For narrow and broadband? 
I had an hour clear last night and was trying mode 1 gain 56 offset 25 narrowband, on the heart and soul. 1min subs, I could see the nebula, 2min subs parts of the heart were white, looked oversaturated. 
I don’t know if Nina is stretching the image, I’m still a complete novice with this software 

Has anyone used this combo and do they have any tips? 
 

Many thanks 

Bryan

[assouptro]

I of course realise i just need to open a file in pix to see if it’s blown out, I am just reaching out as I’m at work and haven’t got the capability to do that atm, I’m going to be pushed for time before I go away and I’m just hoping for a shortcut to the answer 🙄It’s one of those “back of the mind” niggles that’s eating away 

Cheers 

Bryan

Edited October 27, 2022 by assouptro

[Phillyo]

I don't have that exact set up, but I use the Risingcam IMX571 which I think is the same or similar sensor with the Samyang. I shoot at f3.5 using stop down rings and for narrowband (5nm Antlia ALP-T filter) I shoot 3min exposures as directed by NINA exposure calculator having done a sensor analysis in Sharpcap Pro. I don't mess with the gain or offset and leave them at default.

NINA will be debayering and performing a stretch on your image, so it's a useful guide but don't look into it too much. As you say, you need to stack them and check them fully in PI before really getting an idea.

For broadband I can shoot as short as 5 seconds in my area, but obviously that would fill my hard drive way too quick so I normally shoot 30, 60 or 120s exposures depending on the brightness of the target I'm aiming for.

I live in a Bortle 4/5 area for reference.

[assouptro]

39 minutes ago, Phillyo said:

I don't have that exact set up, but I use the Risingcam IMX571 which I think is the same or similar sensor with the Samyang. I shoot at f3.5 using stop down rings and for narrowband (5nm Antlia ALP-T filter) I shoot 3min exposures as directed by NINA exposure calculator having done a sensor analysis in Sharpcap Pro. I don't mess with the gain or offset and leave them at default.

NINA will be debayering and performing a stretch on your image, so it's a useful guide but don't look into it too much. As you say, you need to stack them and check them fully in PI before really getting an idea.

For broadband I can shoot as short as 5 seconds in my area, but obviously that would fill my hard drive way too quick so I normally shoot 30, 60 or 120s exposures depending on the brightness of the target I'm aiming for.

I live in a Bortle 4/5 area for reference.

Thank you for replying to my enquiry 

I can see I am going to have to do a sharpcap sensor analysis and get the valuable information required, I don’t think it’s wise to look for shortcuts with this camera! 

I miss the simplicity of the Atik ccd cameras, the only thing I had to decide on was to bin or not to bin depending on arcseconds per pixel! 
 

I’m not familiar with the risingcam capabilities, I’m aware of the camera as I nearly bought one myself, I have one question….

When you say you leave the gain and offset at default, what is the default on that camera? 
 

Thanks again 

Bryan

 

[Phillyo]

1 hour ago, assouptro said:

Thank you for replying to my enquiry 

I can see I am going to have to do a sharpcap sensor analysis and get the valuable information required, I don’t think it’s wise to look for shortcuts with this camera! 

I miss the simplicity of the Atik ccd cameras, the only thing I had to decide on was to bin or not to bin depending on arcseconds per pixel! 
 

I’m not familiar with the risingcam capabilities, I’m aware of the camera as I nearly bought one myself, I have one question….

When you say you leave the gain and offset at default, what is the default on that camera? 
 

Thanks again 

Bryan

 

Ha, yeah I hear ya! I sometimes miss my old QSI583 CCD camera...but I don't miss the 20min exposure times required!!

So, Risingcam have two different drivers for the camera. They have a native driver and an ASCOM driver. The native driver has an offset of 768 and a gain of 100. The ASCOM driver is different, but the actual results of the values remain the same (I can't remember exactly what the ASCOM default values are as I only really use the native drivers in NINA). I *THINK* it's something like gain 0 offset of 50, but don't quote me on that. However like I say, just because the gain of one of them is 100 and the other is 0 doesn't mean there's any actual difference in gain, it's just how the drivers display it. Same with offset.

With my 533MC Pro, I also just left the gain and offset at default and just adjusted the exposure length to the target/conditions/filter etc.

Hope that makes sense!

Phil