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ASI462 noise is very bad

CCD Imaging
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#1 keen227

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Posted 13 May 2022 - 11:21 AM

Hello all. I have a new ASI462. Bought for planet season coming up, but tried some deep sky with it. The noise level is horrible. Anywhere from 1sec to 30 sec exposure, all different gain settings, I can just barely make out the stars within the noise. Flipped to the moon with 1-10milli-sec exposure and it seemed fine. With the lens cap on, using the ASI software, any exposure, any gain, the histogram shows vertical line at 6300 (full scale is 65535).

Does this sound correct? Is there a calibration step I'm missing? 

Thanks

Ken



#2 Alien Observatory

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Posted 13 May 2022 - 12:26 PM

Due to the 462 extreme sensitivity at infrared (850 nm) I would recommend to using a UV/IF filter and no lower gain than unity (about 90).  I had one of these cams a couple of years ago and only kept it for a few weeks as I did not like the performance.   Pat Utah smile.gif

 

 

https://astronomy-im...t/asi462mccolor


Edited by Alien Observatory, 13 May 2022 - 12:27 PM.


#3 alphatripleplus

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Posted 13 May 2022 - 01:39 PM

Have you compared it with another camera? 



#4 Straight on til morning

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Posted 14 May 2022 - 06:23 PM

I have used an asi462 for about a year and it works fine for all types of imaging. I have used it mainly for DSO.

The vertical line at 6300 with the cap on will be the camera bias. Take bias frames at the same and temperature to remove those in stacking. Taking dark frames also helps. In my experience the asi462 still works fine without bias or dark frames as long as you adjust the histogram as the noise is very consistent over the sensor. Calibration frames are important but not essential with this camera.

Under bortle 5 with an f5 scope, sub exposures times of 5-10s should work well with gain=90 (recommended gain). Only the brightest stars will saturate and the signal to noise should be good.

The high IR sensitivity of the asi462 is its party trick. If you use an Apo refractor or a reflector that has little chromatic aberration then try without the UV/IR filter on broadband targets such as faint galaxies. The extra IR boosts the signal a lot. For emission nebula and clusters it would be better to use UV/IR or UHC filters.

What scope setup do you have, and what is your light pollution level?

#5 keen227

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Posted 15 May 2022 - 11:37 AM

Scope is 500mm FL, 102mm diam refractor, bortle 5. Also tried with UHC light pollution filter.  I was thinking the noise may cancel out when stacking, but it isn't constant. It's like an old TV with no signal where you get all snow. With 10 sec exp it was impossible to make out M81. I couldn't tell if I was on target to take a bunch of subs. 

I didn't keep any video...I need to set up again and capture something. I know this isn't meant for deep sky, but I see many example of it working.

Thanks for the help 



#6 Alien Observatory

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Posted 15 May 2022 - 12:16 PM

Hate to ask the question... USB Cable Issue?  Have you tried connecting the cam to your computer with a short USB 3 cable to see if that is an issue?  Pat Utah :)



#7 Straight on til morning

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Posted 16 May 2022 - 05:06 AM

That is weird. My old setup was almost identical and it worked fine for DSO. Many faint DSO will be barely visible as a faint smudge in single subs so that part is not unusual.

Use gain 90. Lower gain is much, much noisier. Sun exposure ~5-10s should work fine.

Use ASILive - it is the simplest app to use.

How does it go on brighter targets such as Orion or bright clusters?

Just checking for major errors here. Have you enabled the auto histogram stretch? Without it you will basically see nothing. It is a rookie error that I made in the early days. Another rookie error is to view the single frames when stacking rather than the stacked images.

It would be really helpful if you posted a screen shot of your stacking program and a single frame image.

#8 happylimpet

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Posted 16 May 2022 - 05:38 AM

Its a very sensitive camera. You're doing something wrong!



#9 alphatripleplus

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Posted 16 May 2022 - 06:22 AM

If you can post a screenshot from SharpCap on a bright DSO with settings visible, it might be helpful for the purposes of diagnosis. 


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#10 AhBok

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Posted 16 May 2022 - 09:44 AM

Are you looking at a single short sub or a live stack of short subs? I would expect a single short sub to be quite noisy, especially for higher gains. I recommend starting with unity gain and 8-15 second subs while live stacking in SharpCap. Use the histogram on the live stacking page. After you get decent results, learn to use the smart histogram along with flats and darks for best images. However, a stack of 5-10 minutes using unity gain should clean up much of your noise, even without calibration frames.

#11 keen227

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Posted 19 May 2022 - 08:55 PM

Haven't had much good weather, but looks like it can work well. Until now, I have only used a Canon DSLR. Take a 30 sec exp on high ISO and it's easy to make out almost any target. I thought the ASI462 would be the same at high gain. I'm not clear why, but that is not the case. Another mistake was using the ASI free software. I got Sharpcap, figured out how to take darks and flats and do live stacking and that seems to work. Need a clear night to give it a full test, but I'm pretty sure this will work as I expected

 

thanks all


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