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How do y'all take flats with the ASI294mm / QHY294M ?

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#1 StellarHesk

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Posted 14 May 2022 - 10:31 AM

The 294 is one of the two cameras (533mm) I'm split between in considering getting in the near future (next few months maybe...), and I've seen all of the drama with the finicky nature of the IMX492 sensor. I'm not worried about the amp glow, because that shouldn't be a problem if darks are matched. I'm curious to know which methods y'all use to get consistent flats with this camera (flat panel? Exposure times? Sky flats?) - The last thing I want is to end up banging my head over overcorrection.

 

 

Appreciated!


Edited by StellarHesk, 14 May 2022 - 11:27 AM.


#2 michael68

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Posted 14 May 2022 - 11:00 AM

I use N.I.N.A's Flats wizard. So easy-peezy! Slew to the zenith, White T-shirt and an Ipad with a pure white wallpaper. I run through 40 flats of LRGB-HOS in less than 10 minutes and my flats always come out great.


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#3 hornjs

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Posted 14 May 2022 - 11:00 AM

What is the other camera you are considering?  I struggle with flat correction on my 294mm.  My 294 mcp does great.  Seems like I do fine in narrowband but can’t correct the sensor pattern in LRGB. 
IAm using an elumiglow light panel, 3 sec flats.  Tried several adu.  Finally started taking L AT ZERO GAIN, RGB at 50 gain and the sensor pattern is not as bad, easier to correct in processing. But as you know those low gains come with other problems.  
just got the 2600 last week.  Getting that set up now as my main camera.  Will keep the 294mm around for narrowband only.


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#4 dswtan

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Posted 14 May 2022 - 11:16 AM

NINA, Amazon sketching panel (large A3 size), t shirt, Dark Flats not Bias. No issues.

 

From what I’ve read here, it’s the 294MC (OSC) that people have more commonly have trouble with, not the 294MM. (Post above excepted.)

 

I’m just getting a second 294MM to replace the 1600MM on my long focal length rig. Full confidence.


Edited by dswtan, 14 May 2022 - 12:03 PM.

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#5 StellarHesk

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Posted 14 May 2022 - 11:19 AM

What is the other camera you are considering?  I struggle with flat correction on my 294mm.  My 294 mcp does great.  Seems like I do fine in narrowband but can’t correct the sensor pattern in LRGB. 
IAm using an elumiglow light panel, 3 sec flats.  Tried several adu.  Finally started taking L AT ZERO GAIN, RGB at 50 gain and the sensor pattern is not as bad, easier to correct in processing. But as you know those low gains come with other problems.  
just got the 2600 last week.  Getting that set up now as my main camera.  Will keep the 294mm around for narrowband only.

My second option would've been the ASI533MM Pro (I'll edit that into the original post). It's a more forgiving camera, but the wider field of view of the 294 is desirable for me if possible.


Edited by StellarHesk, 14 May 2022 - 11:27 AM.

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#6 StellarHesk

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Posted 14 May 2022 - 11:26 AM

I use N.I.N.A's Flats wizard. So easy-peezy! Slew to the zenith, White T-shirt and an Ipad with a pure white wallpaper. I run through 40 flats of LRGB-HOS in less than 10 minutes and my flats always come out great.

Cool! Do you happen to take bias frames too? Or dark flats?



#7 michael68

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Posted 14 May 2022 - 11:38 AM

 

From what I’ve read here, it’s the 294MC (OSC) that people have more commonly have trouble with, not the 294MM. (Post above excepted.)

 

I have actually never had an issue getting flats with my 294mc. NINA has worked great with both the 294mc and 1600mm

 

 

Cool! Do you happen to take bias frames too? Or dark flats?

I don't take bias because these are cmos and from what I've read, the noise has no consistency. Some folks say to use longer than say 1/4000 of a sec but I've just forgone those and just take flats and darks. I don't usually bother with dark flats either. I've taken dark flats and subtracted them from my calibration frames but never really see a side by side comparison difference. 


Edited by michael68, 14 May 2022 - 11:39 AM.

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#8 jrmagill

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Posted 14 May 2022 - 12:38 PM

I'm curious to know which methods y'all use to get consistent flats with this camera (flat panel? Exposure times? Sky flats?) 

 I have the ASI294MM Pro camera and take flats using a light panel with 3 sheets of white printer paper taped on top to reduce the transmitted light and act as a diffuser.  I shoot LRGB and SHO;  have never had a problem with calibration corrections.   I take dark flats and don't use bias frames.   Exposure times for flats are 0.1 seconds for L,  0.3 seconds for RGB, and 3 seconds for SHO.   Brightness of the light panel is adjusted for the different filters to get an optimum ADU (about 30,000).   


Edited by jrmagill, 14 May 2022 - 12:43 PM.

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#9 Drothgeb

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Posted 14 May 2022 - 01:44 PM

I use a 294MC. I use a 1” thick piece of white acrylic with an iPad on top for flats. And I do dark flats instead of of bias. Both are 3 sec exposures.


Edited by Drothgeb, 14 May 2022 - 01:45 PM.

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#10 fuadramsey

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Posted 16 May 2022 - 03:24 PM

Both the 294mm and 294mc suffer from the dark noise not being scalable. So with both cameras (even though they have different sensors), you do not want to use bias frames. Instead use dark flats that are 2.5 seconds or longer.

 

I have two cheap dimmable Amazon light panels. One is for narrowband filters, and the other is for LRGB. On the LRGB panel, I put automotive tint on it to bring the brightness down to do the required long flats. I could not get it dim enough to do long exposures without the tint.


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#11 StellarHesk

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Posted 16 May 2022 - 08:39 PM

What is the other camera you are considering?  I struggle with flat correction on my 294mm.  My 294 mcp does great.  Seems like I do fine in narrowband but can’t correct the sensor pattern in LRGB. 
IAm using an elumiglow light panel, 3 sec flats.  Tried several adu.  Finally started taking L AT ZERO GAIN, RGB at 50 gain and the sensor pattern is not as bad, easier to correct in processing. But as you know those low gains come with other problems.  
just got the 2600 last week.  Getting that set up now as my main camera.  Will keep the 294mm around for narrowband only.

Forgot to ask, but do you skip bias frames and use dark flats instead? I heard that using bias frames can be problematic with this sensor.



#12 KTAZ

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Posted 16 May 2022 - 09:02 PM

294MC Pro is best with dark flats no bias. Keep flats and dark flats below 2 seconds. Sky flats all day long.


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