Max Frame rate & a new camera

[Calamity_Jane]

Hi:

I just acquired a ZWO ASI 2600MM camera, with a view to replacing a ZWO ASI294MM.

I've been doing some astrometric shots for a while, where I expose for 0.5s per frame, stack 800 frames and keep the best 10%. This is using lucky imaging for deep sky work, tracking star movements.

SharpCap and my Windows 10 PC could keep up with the 294, and write frames as fast as I could collect them. This doesn't seem to be the case with the larger files of the 2600. I'm pretty sure that the rate-determining step is the speed of my hard disk drive, about which I can't easily do much.

So I tried a max frame rate of 2 per second, and it lost fewer frames, but still lost some. I could obviously set the max frame rate to 1 per second, but the time to expose 800 frames then starts to add up. I'd really prefer to set it to 1.5 fps if I could. I don't think I can set vales not in the menu for maximum frame rate. Is that correct?

(I don't seriously want to see the live stack - it's just a convenient way to weed out really bad frames, especially on nights when there are lots of passing clouds.)

Thank you,
Jane

[admin]

Hi Jane,

once you get everything sorted you will really notice the improvement in image quality (and ease of use) in switching from the 294 to the 2600...

For the saving, the first thing to think about is the format in which you are saving the files - FITS is the slowest format to save in in terms of CPU operations needed to prepare the file, and also usually creates the largest files, meaning that the disk will have to write data at a higher rate than other formats. If you are using FITS, it may be worth trying other formats (PNG as a first try) to see if that helps at all. You could also consider SER video format and then use a tool like PIPP later to split the video into frames. Obviously if you are already using PNG or SER, this isn't much help. Do beware when saving to PNG that those files *do* allow 16 bit data, but some processing/viewing applications will drop the data down to 8 bit when you open the file. Astro imaging applicaitons are usually OK, but those aimed at more general photo viewing can often do this.

Another thing you can try is to bring up Windows task manager while capturing, make sure you are in the detailed view and open the 'Performance' section. This will show the usage of various system resources. If you are losing images then I would expect that something is at 100% - either CPU or the disk you are saving to. If it is the disk then clearing extra space on the disk and either defragmenting (hard disk) or optimizing (SSD) before capturing may help a bit.

cheers,

Robin

[Calamity_Jane]

Thank you. There are some interesting ideas there to think about. The weather won't be clear here in S. E. Wales tomorrow night, so that may be a chance to defrag the disk on the observatory PC.

Probably the thing to try tonight is to use a ser file to feed to Autostakkert, which is how I normally stack images of stars. I have tried other apps, but find Autostakkert hard to beat.

I have been watching on the task manager. The disk is the rate-determining device now. It was RAM until I quadrupled the amount of RAM in the PC a couple of years ago.

Regards, Jane.

[admin]

Hi,

good to have it pinned down to the disk speed. If you are using an old-fashioned spinning hard disk then that's your problem right there, and updating to an SSD for captures will make a big difference. For SSDs, NVMe is better than SATA but both can slow down when near to full, or when you have written a lot of data recently (you may find that maybe 50Gb will write quickly, then it slows down).

cheers,

Robin