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Ngc5189
I thought it might be worthwhile to share a test result imaging NGC5189. Some of latest images in the forum showed so much fine details compared to years ago and completely changed my impression that deep sky images would best be limited to an image pixel scale of about 0.8 arcsec/px, and CMOS cameras with small pixels would require faster apertures. After successfully converting a Skywatcher Quattro 12/F4 to truss structure, saving some 4-5 kg weight using aluminium bars (swimming pool fence bar), I did the same with a Skywatcher astrograph 300F5 that I bought years ago for viewing. I also bought an ASI2600mm and an ASIAIR mini for automated imaging. I tried imaging NGC5189 using GSO RC10, 300F4, and 300F5 in the past few weeks, with my CEM60 mount broken down and fixed myself in-between. 300F4 obviously was brightest but showed less resolutions (it could also be due to unfavourable seeing plus mount tuning issues). RC 10 with a TCD 0.67x reducer at a focal length of about 1340mm showed more details, and 300F5 at a focal length of 1500mm came out the best. Seeing in the past few weeks was average at best. Seeing was in fact a far more deciding factor than image gear performance and/or combinations. In calm Sydney weather with good seeing conditions longer focal lengths can definitely resolve more details on a camera such as ASI2600MM with a pixel size of 3.8 micron. Here is a HOO image of NGC5189 with 46 and 44 subs in 10 min for Ha and Oiii, 3nm Antila filters, cooled to -15 degrees. It isn't as fine as David's incredibly detailed version with a 14 in SCT, but it is nevertheless acceptable to me for a 12 in Newtonian. It could be improved with better seeing and a steadier mount. Of these 46 and 44 subs for Ha and Oiii only 1-2 hours for each filter were with good quiding resolution around 0.5 RMS total.
Clear skies,
John
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