9 replies to this topic

[AlienRatDog]

Hi everyone, I’ll be having an ASI071MC Pro coming my way soon. I have some questions:

-is there an optimal cooling temp (I.e, where there is diminished returns on performance)? I want to stick with the “warmest temp” I can get away with so I can use one temp and make a darks library for the exposures I typically use. (-5 deg C?)

-with a cooled camera, I can essentially take darks indoors since the sensor temperature is held at one temp (so I can build up my dark library at home to save actual imaging time as my time is very limited), is this a reasonable assumption?

- what kind of DC power cable are you guys using? I want to grab one of those lithium power tanks off Amazon (45 amp hour). My imaging sessions will never be more than two hours. I currently have a 17 amp-hr lead acid battery pack...not sure if that will curly it as I will connect my laptop to it also.

Thanks!!

[Midnight Dan]

If you go to their web page for that camera and scroll down to the graphs, the dark current bottoms out at -5C.  So you're probably good there.

 

For power, it will depend on the ambient temperature.  The cooler can use up to 3 amps when running at 100%.  On a warm night it will be close to that, bu on a cool night it might be using only 20 or 30%.  

 

So if you're using 3 amps for 2 hours, you'll need 6 amp hours.  But ... the important thing is that it is 6 amp hours at 12 volts.  Contrary to popular belief, amp hours is NOT the power capacity of a battery.  Watt-hours is.  When using amp-hours, you can only compare batteries if they are rated at the same voltage.  Lithium batteries are often rate at their native cell voltage of about 3 volts, not 12.  If that 45 amp hour battery is rated at 3 volts, it will have only have 1/4 the amp hours, or about 11 amp hours, at 12 volts.

 

Just a warning that you have to carefully look at the specs and make sure the amp hours is rated at 12 volts.  If not, you have to calculate the 12v amp hours.

 

** edit **

 

I just went to Amazon and found a 45,000maH battery bank:

 

http://tinyurl.com/yxcxwzy6

 

If you look at the description, it says it is 167Wh (watt-hours).  Divide that by 12 to get amp hours at 12volts, and you'll see that it has 14 amp hours at 12 volts.

 

-Dan

Edited by Midnight Dan, 11 September 2019 - 09:13 AM.

[petert913]

Great info, Midnight Dan !  Thanks from the rest of us

[AhBok]

After much experimentation in my Bortle 4/5 skies, I find anything below 0C makes no detectable difference in my images. I am convinced the 071MC Pro requires less cooling, less dithering and less exposure time than most people think. The camera has very low read noise, fixed pattern noise and no “amp glow (sic)”. In fact, if you have anything more than Bortle 2 skies, LP will swamp other noise contributors, including thermal noise, by a good bit. Under extremely dark skies, more exposure time and deeper cooling might be warranted to get optimal performance available.

But this is just my experience/opinion. Others vary.

Edited by AhBok, 11 September 2019 - 02:01 PM.

[Midnight Dan]

After much experimentation in my Bortle 4/5 skies, I find anything below 0C makes no detectable difference in my images. I am convinced the 071MC Pro requires less cooling, less dithering and less exposure time than most people think. The camera has very low read noise, fixed pattern noise and no “amp glow (sic)”. In fact, if you have anything more than Bortle 2 skies, LP will swamp other noise contributors, including thermal noise, by a good bit. Under extremely dark skies, more exposure time and deeper cooling might be warranted to get optimal performance available.

But this is just my experience/opinion. Others vary.

 

According to the graph on their web site, there should be a small improvement between 0 and -5C. But may not be noticeable.  I agree completely on the exposure length.  My exposures are usually in the 30 second to 2 minute range with my 071 pro.

 

-Dan

[telfish]

0C works fine for me. Cool slowly in stages and try and keep below 25% power draw to avoid frosting/condensation.

[Diellur]

I'm using a QHY168C, which is more or less the same camera. For cooling I bring it down to -10 deg C and it works well. Re the darks, yes you can take them at a later point. However a word of caution; make sure your setup is still in a dark room - I didn't realise this was necessary and my first set of darks were distinctly light! 

[AlienRatDog]

I'm using a QHY168C, which is more or less the same camera. For cooling I bring it down to -10 deg C and it works well. Re the darks, yes you can take them at a later point. However a word of caution; make sure your setup is still in a dark room - I didn't realise this was necessary and my first set of darks were distinctly light!

.

Thanks for the heads up!

[AlienRatDog]

If you go to their web page for that camera and scroll down to the graphs, the dark current bottoms out at -5C. So you're probably good there.

For power, it will depend on the ambient temperature. The cooler can use up to 3 amps when running at 100%. On a warm night it will be close to that, bu on a cool night it might be using only 20 or 30%.

So if you're using 3 amps for 2 hours, you'll need 6 amp hours. But ... the important thing is that it is 6 amp hours at 12 volts. Contrary to popular belief, amp hours is NOT the power capacity of a battery. Watt-hours is. When using amp-hours, you can only compare batteries if they are rated at the same voltage. Lithium batteries are often rate at their native cell voltage of about 3 volts, not 12. If that 45 amp hour battery is rated at 3 volts, it will have only have 1/4 the amp hours, or about 11 amp hours, at 12 volts.

Just a warning that you have to carefully look at the specs and make sure the amp hours is rated at 12 volts. If not, you have to calculate the 12v amp hours.

** edit **

I just went to Amazon and found a 45,000maH battery bank:

http://tinyurl.com/yxcxwzy6

If you look at the description, it says it is 167Wh (watt-hours). Divide that by 12 to get amp hours at 12volts, and you'll see that it has 14 amp hours at 12 volts.

-Dan

Thanks!!! I am going to go with a 220W-Hr one to be on the safe side.

[AhBok]

According to the graph on their web site, there should be a small improvement between 0 and -5C. But may not be noticeable.  I agree completely on the exposure length.  My exposures are usually in the 30 second to 2 minute range with my 071 pro.

 

-Dan

Hi Dan,

 

I believe if your skies are truly dark, say Bortle 1-2, the difference in 0 and -5c would make a difference. My skies are Bortle 4/5 and I am pretty sure the LP swamps any improvement that one might see by going to -5c temp. IOW, I agree with the graph, but you would have to have, I believe, truly dark skies to achieve a practical  performance improvement. BTW--Robin Glover, Mr. SharpCap, has an excellent presentation that addresses this. It is well worth the time to review this video:

 

 https://www.youtube....3UvP358&t=1416s