astroshot wrote: ↑Tue Dec 26, 2023 7:32 pm
How big a video file size did you have as a result?
I watched the YouTube video. The file size used was around 1.8 GB. In FireCapture, the FPS was 15. The number of frames was 2448 (dimensions 2432 x 152 pixels). This means the time for the scan was 163 seconds. Since the Y/X ratio was close to 1.0, this suggests the mount was not scanned but the Sun was simply allowed to drift across the slit.
I've noticed a lot of very high end mounts are actually not particularly good at the kind of slewing required for this technique. That might be the reason Pedro has decided to use "drift scan".
It seems the cheaper Skywatcher mounts are actually some of the best for scanning. They can scan at an arbitrary rate (e.g. 15x sidereal rate) and generally keep a quite constant velocity.
The ZWO AM5/AM3 mounts are quite good at scanning (they have a very constant velocity), but the drivers don't seem to support arbitrary slewing rate.
While drift scan obviously produces an image with very little geometric distortion, the disadvantage is the long scan time means there is more opportunity for noise (air turbulence, floor vibration, etc). I generally try to push the data into a higher frequency range, assuming that the noise sources tend to have 1/f characteristics. If you minimise the ROI width, you can find the maximum FPS that the camera/computer combination can handle. Generally, somewhere around 300 fps is achievable; i.e. 20x the 15 fps used here. This means you can scan at around 20x sidereal rate.
solar_imaging_session_20231226-02 by Pedro Re', on Flickr
solex_20231226 (9) by Pedro Re', on Flickr
solar_imaging_session_20231226-05a by Pedro Re', on Flickr
solex_FS60C_20231226_mosaica by Pedro Re', on Flickr
solex_20231226-02 by Pedro Re', on Flickr
solex_20231226-05 by Pedro Re', on Flickr
solex_20231226-06 by Pedro Re', on Flickr
