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asi294mc pro uneven cooling in warmer weather (at first)? target max fan speed?

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#1 markm75c

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Posted 02 June 2020 - 09:56 PM

I have the asi294mc pro on the edge 11 with oag and 174mm mini guide camera.

 

On some warmer nights (72F and up), i've left it at my usual -10C cooling target, but im noticing a hot spot early on in the imaging session, maybe the first 20 minutes (i should be equalizing longer, forget how long though, anyway, its a nexdome).

 

Is this pretty typical to see this type of pattern near the center (nina with extreme stretch going on, raw image, frame)?  Also, wondering what typical max speed fan target I should shoot for to avoid added noise, i want to say it was 65%?  After about 15 mins its at 67% for -10C (all my darks/flats are at -10C as of now).

 

Thanks in advance for any info, though i think its just a cool down period thing

 

Capturehotspot.JPG


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#2 RazvanUnderStars

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Posted 10 June 2020 - 10:06 AM

It's not the fan speed that should be the target but the temperature rather. The required cooling it will vary throughout the year.

 

Robin Glover, SharpCap's author, has a very useful presentation at https://youtu.be/3RH93UvP358 in which he also covers how temperature affects noise (jump directly to that section: https://youtu.be/3RH93UvP358?t=1108). The chart he showed also covers the ASI294. -10C is a good target, which I use as well, the thermal noise then will then be negligible. 



#3 Ptarmigan

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Posted 14 June 2020 - 07:14 PM

I had a similar problem when I set it at -20. When I set it at -5, it is not there. Is there a way to cool down the camera slowly? It goes rather fast, which I think causes the dew.



#4 RazvanUnderStars

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Posted 17 June 2020 - 12:36 PM

I don't know. In Sharpcap the cooling power setting is read only for ZWO cameras (at least according to the manual last updated in 2018). It can also be done by switching cooling on and off repeatedly, but I'm not sure it's recommended, thinking of the thermal stress.



#5 m3guy

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Posted 17 June 2020 - 04:04 PM

I get this too.  Here's what I've observed.   

 

  1. If I push the cooler power over about 75% this problem is more likely to happen.   So in winter I can shoot -15 no problem, but find I need to shoot -10 in the summer.   
  2. Even at 10 degrees, this problem shows up for me sometimes when it first gets up to temp, then the "fog" fades away after 15-30 minutes.   
  3. One of the things I've done to manage this is to take a rough flat ahead of the imaging session and make sure the fog is not present by stretching in StarTools.   If it is, I either wait or try dialing back my cooling.

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