Configuration for minimum power usage

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Rob2160
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Joined: Tue May 31, 2022 11:48 am

Configuration for minimum power usage

#1

Post by Rob2160 »

Hi Robin,

Long time use of Sharpcap and thanks for the many updates and new features.

I am planning an extended trip to remote areas and this will require operating a laptop from small portable power banks. In my recent testing when operating Sharpcap the power requirement of the laptop increases from 3-4 watts idle to around 25-30 watts (When capturing at the rate of 1 frame per second)

I am looking for the most efficient configuration and any advice is appreciated.

Should I use new or old interface?
Enable or disable graphics card acceleration?
32 or 64 bit version?

Thanks.

Rob.
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Re: Configuration for minimum power usage

#2

Post by admin »

Hi Rob,

I'm not sure that I can give you good answers, or at least you are likely to get better answers by trying out the options with a wattmeter attached to your laptop, since the results may well depend on details of your laptop that will be different on any system I test on.

In general, I would now recommend the 64 bit version, since it is less likely to suffer from out of memory issues if you do complex processing - no idea how processors differ in terms of power usage for 32/64 bit though.

I will spend a little time checking on any unecessary power usage in SharpCap (what camera brand are you using?) to see if it is something I can improve in a future update.

cheers,

Robin
Rob2160
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Re: Configuration for minimum power usage

#3

Post by Rob2160 »

Thanks for the quick reply.

I will be using a ZWO 485MC on this trip. I have three Comsol laptop power banks (Airline carry on size for Lithium Batteries which is the limitation)

Each can keep the laptop at 100% charge for about 3 hours so it is enough for one night. The power banks have a watt meter built in and this is when I noticed the increase when starting Sharpcap and capturing. (Never an issue at home as it is plugged into the mains)

Lowering screen brightness and turning off screen after 1 minutes helps also but it made me curious about other ways to tweak efficiency.

Regards.

Rob.
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Re: Configuration for minimum power usage

#4

Post by admin »

Hi,

I did find a power drain with PlayerOne brand cameras that was a mistake on my part (left the CPU running waiting for the next frame to arrive), but ZWO were fine in that respect. I fixed the PlayerOne issue, so that will be in the next update anyway.

You may want to test different save formats - I suspect that FITS may draw the most power as it is a relatively inefficient format. You might find PNG is the most efficient. If the difference is significant then you need to decide if you can live without the metadata in FITS files.

cheers,

Robin
Rob2160
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Joined: Tue May 31, 2022 11:48 am

Re: Configuration for minimum power usage

#5

Post by Rob2160 »

Thanks Robin,

I tried different capture formats and didn't notice much difference. What seems to make the most difference is how much of the image is bright.

For example. Taking one frame per second of a full Moon filling most of the frame uses more power than an equivalent size image of the stars.

Using the test cameras on Deep Sky - 1 frame per second uses 14-15 watts
On High Speed (Jupiter) - 1 frame per second uses 28-30 watts.

This usage continues even when the laptop screen turns off (Set to 1 minute)

I did some bench testing with the cover over the telescope so the camera was taking all dark images. When I tried the same configuration and settings on a full moon the draw was significantly higher so the battery did not last as long as the bench testing had predicted. (less than half the time)

I would understand if the screen was on and displaying a bright Moon but the drain increase with screen off is the essentially the same.
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Re: Configuration for minimum power usage

#6

Post by admin »

Well, that is definitely weird!

Do you see a difference in reported CPU/GPU usage in task manager between dark and light images? I just tried a similar test and can possibly see some change in CPU usage between a dark image and a light one in RAW16 mode (but nothing in RAW8). I will have a look at the code when I get a chance to see if there is any good reason behind that.

One thing I did notice is that if you minimize the SharpCap window then the GPU usage drops to zero (since it is not drawing the image updates) - this may save some battery.

cheers,

Robin
Rob2160
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Re: Configuration for minimum power usage

#7

Post by Rob2160 »

Thanks I did notice that minimising the window reduces the current drain. I will buy a better wattmeter this week and do more detailed testing.

I have it working to the point where I can make the trip work nicely, now it is just curiosity.
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Re: Configuration for minimum power usage

#8

Post by admin »

Hi,

I must admit that this thread has got me interested in the power/CPU efficiency of the software too :)

I think the difference between a dark image and a light image is down to calculation of the histogram to show in the mini histogram area on the right - at least it seems to spend more time calculating that histogram when you have a bright image, but only different in 16 bit modes. I suspect this is down to CPU cache hits/misses - making the histogram when you are in 16 bit mode (more histogram bins) and have a bright image involves updating more different memory locations that the small number you end up updating for a dark image. That's my guess, anyway :)

cheers,

Robin
Rob2160
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Re: Configuration for minimum power usage

#9

Post by Rob2160 »

Hi Robin, I did a trial at Broome airport the other night and was able to track the Moon most of the night using the portable batteries to keep the Laptop charged.

I wanted to share that the feature tracking was superb all night. The Moon was held rock solid as per this screenshot.

At one point the Moon was just a few degrees from Zenith.

A fun night.

Cheers,

Rob.
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Re: Configuration for minimum power usage

#10

Post by admin »

Looks like you had a great evening of observing/imaging, and good to hear that the feature tracking worked so well. The option to use the center of mass is great as it is very robust and will work well on full disk sun/moon/planets :)

cheers,

Robin
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