xiongz
31-12-2024, 10:01 AM
There was finally a week long good weather over Christmas period after months of cloudy nights. I took the oppotunity on a camping trip and tested a home-build 12 inch F4 newtonian based on Skywatcher Quattro 300F4. It was a first trip with the scope since I started working on it about a year ago. With some 4-5 kg saved turning the scope into a truss structure using pool fence aluminium bars, it first broke my CEM60 mount as the weight reached upper limit of it. After replacing RA worm, ring gear, and finally the two bearings on RA worm ends, the mount was restored. This setup would be perhaps the lightest combination for a 12 scope. Plus a truss structure would help reducing wind effects on guiding, making it suitable for camping trips.
As it was a first such trip, the primary mirror mount worked loose slightly, giving me oblong stars at in the first few nights. I tightened the scope all over again and problems persisted. Since stars were round at certain angles I thought it could be primary mirror mounts. For people with Quattro 12 this might need some special words. Primary mirrors on Skywatcher newtonians cannot be tightened fully without deforming mirrors. I first noticed this on a carbon version of Quattro 10. I had to add metal clips to make it road safe. I already added longer clippers for the mounts on Quattro 12 but it came with only 3 mounting bases/clips instead of 6 on Quattro 10. I think these mirrors were a bit too thin for F4 as well, which also cause rapid focal changes with temperatures. These focal changes far exceed temperature effects on scope structure with aluminium bars.
Anyway, here are images for NGC 1365 and NGC 1532, ASI2600MM, cooled to -15, gain 100, 5min subs. First two nights were actually best seeing with RMS guiding errors around (and mostly under) 0.3 arcsec for both RA and DEC, but unfortunately about 40% of my 132 subs for L were lost due to excessively oblong stars. More should be trashed if I were to have tighter stars. Final image was with 81 subs for L, 15, 14, and 20 for R, G, and B, respectively, totalling just under 11 hours. NGC1532 was with 59 subs for L, 12, 7, and 16 for R, G, and B, respectively, totalling just under 8 hours. I was going for one hour each for RGB but wind blown away a few for G. NGC1532 was downsized by 30% to bring files size allowed here. These certainly wouldn't be as good as observatory setups, but they were nevertheless much better than what I got with Quattro 10 and ASI1600 before. I may add more data later or maybe next year.
Happy New Year,
John
As it was a first such trip, the primary mirror mount worked loose slightly, giving me oblong stars at in the first few nights. I tightened the scope all over again and problems persisted. Since stars were round at certain angles I thought it could be primary mirror mounts. For people with Quattro 12 this might need some special words. Primary mirrors on Skywatcher newtonians cannot be tightened fully without deforming mirrors. I first noticed this on a carbon version of Quattro 10. I had to add metal clips to make it road safe. I already added longer clippers for the mounts on Quattro 12 but it came with only 3 mounting bases/clips instead of 6 on Quattro 10. I think these mirrors were a bit too thin for F4 as well, which also cause rapid focal changes with temperatures. These focal changes far exceed temperature effects on scope structure with aluminium bars.
Anyway, here are images for NGC 1365 and NGC 1532, ASI2600MM, cooled to -15, gain 100, 5min subs. First two nights were actually best seeing with RMS guiding errors around (and mostly under) 0.3 arcsec for both RA and DEC, but unfortunately about 40% of my 132 subs for L were lost due to excessively oblong stars. More should be trashed if I were to have tighter stars. Final image was with 81 subs for L, 15, 14, and 20 for R, G, and B, respectively, totalling just under 11 hours. NGC1532 was with 59 subs for L, 12, 7, and 16 for R, G, and B, respectively, totalling just under 8 hours. I was going for one hour each for RGB but wind blown away a few for G. NGC1532 was downsized by 30% to bring files size allowed here. These certainly wouldn't be as good as observatory setups, but they were nevertheless much better than what I got with Quattro 10 and ASI1600 before. I may add more data later or maybe next year.
Happy New Year,
John