PeterSEllis
24-07-2018, 03:13 PM
Hi Guys,
Back again, for those who might be interested, this is a shot of M8 was through my Esprit 150mm using a WILLIAM OPTICS Flattener 4 - 0.8X Reducer.
When you enlarge the shot up, there is slight elongation of the stars in the very corners of the shot, but the rest are fine. It is absolutely crucial to get that back focus distance correct, if it is not correct, the stars are god dam awful. It took a little bit of trial and error to nail the correct back focus distance.
A measurement and calculation using Astrometry, indicates a reduction on my system by x0.821. If there is any interest, I will put up a shot through a Riccardi triplet Apo Reducer x0.75, when it finally arrives.
3.5 Hours exposure (ASI071 pro) with the Moon shining like a beacon from hell, and the wind ranging from 10KmH to 13KmH, with the gusts being about double that. "Not ideal conditions", we live with what we get.
Cheers
Peter
Back again, for those who might be interested, this is a shot of M8 was through my Esprit 150mm using a WILLIAM OPTICS Flattener 4 - 0.8X Reducer.
When you enlarge the shot up, there is slight elongation of the stars in the very corners of the shot, but the rest are fine. It is absolutely crucial to get that back focus distance correct, if it is not correct, the stars are god dam awful. It took a little bit of trial and error to nail the correct back focus distance.
A measurement and calculation using Astrometry, indicates a reduction on my system by x0.821. If there is any interest, I will put up a shot through a Riccardi triplet Apo Reducer x0.75, when it finally arrives.
3.5 Hours exposure (ASI071 pro) with the Moon shining like a beacon from hell, and the wind ranging from 10KmH to 13KmH, with the gusts being about double that. "Not ideal conditions", we live with what we get.
Cheers
Peter