chris2021 wrote on 2022-08-07, 22:47:
davidrg wrote on 2022-08-02, 00:16:
I dabble a bit in astrophotography though I've been a bit too busy with other things this year. Here is a picture of Saturn I took a few years back (details):
This is mildly amazing to me. Could you describe the equipment needed.to produce a picture like that.
I used a "cheap" SkyWatcher Skymax-127 maksutov-cassegrain telescope which has a 127mm aperture, and a 1.5m focal length (the light travels the length of the tube three times) to produce a narrower more zoomed-in field of view. I also used a cheap 2x barlow lens which kind of has the effect of doubling the focal length to 3m but doesn't increase the resolution at all (need a bigger aperture for that) - it just makes the image bigger on the camera chip.
The camera was a ZWO ASI224MC USB3 camera which is capable of quite a high frame rate if you turn the resolution way down. So the image was made by recording a 320x240 video at some fairly high frame rate (probably 60-100fps), then using some software to align all the frames with each other and combine them together to produce an image with a low signal to noise ratio.
The telescope mount was a SkyWatcher AZ-EQ6 in its equatorial configuration. Normally I'd be using this mount with an 80mm refractor and an old DSLR for deep-space stuff but its much more stable (telescope doesn't shake whenever I adjust it or move nearby) than the little portable mount (a battery powered Mini AZ-GTi) I originally got with the SkyMax-127. The cheap mount is usable for this, it just takes more effort. Both mounts I have support full computer control but for this image I was probably controlling it manually with the keypad as the computer can't really do automatic star alignment with that telescope and camera combination (field of view too small for it to see enough stars to figure out where its looking).
This telescope works quite well for the planets and the moon but due to its focal length to aperture ratio its not too good for deep-space stuff (which is why I got the 80mm refractor). Back in 2020 I also used this same equipment (without the barlow lens) to also make a mosiac of the moon which I thought turned out pretty well though next time I need to turn the gain down on the camera a bit more so the bright areas are less washed out.
This was done under full computer control - I pointed it at the moon and from there a piece of software handed positioning the telescope for each tile and taking a 1304x967 62fps video for later processing. I think up there was around 200GB of data produced all up that got processed down to the one image. You can see the full image here of which the above picture is one tile.