Yesterday evening I had a few hours of partly cloudy skies between the rain storms and wanted to get what will probably be my last look at the Orion Nebula until next fall (looks like rain for the next week to 10 days followed by another cycle on the gibbous and full moon). So, I decided to do a high resolution shot of the core of the nebula, including the Trapezium.
This was going to be a so-called lucky imaging session using exposures that ranged from 1s down to 100mm using a Tele Vue NP127is with an uncooled QHY5III-178C camera. Since I wanted to take frames as quickly as possible I decided not to use Sequence Generator Pro (too slow) and thus imaged using SharpCap. I ended up taking over 60GB of images, 1000 at 1s, 4000 at 250ms, and another 800 at 100ms (ran out of disk space on the last sequence). I didn't use any guiding and I didn't even check my polar alignment (although it was probably pretty close, since I set the tripod and mount -- a Mach1GTO -- down on fixed marks on a concrete slab).
Later (shortly after on the same night) I also captured 256 dark fields at each exposure setting (but no flats, which I may add at a later time).
To qualify for lucky imaging I ran PixInsight's SubframeSelector script looking for the best 20% of the 1s subs and I ended up with a master integration that had a median FWHM of 1.86 arc seconds with a median eccentricity just over 0.3. I'm still working on the 250ms sequence, and that may/should produce an even sharper result. In the end (as shown below) I ended up with 3m 22s of total integration time (202 x 1s) at a gain setting of 30 and an offset of 128.
The original capture scale was at 0.75 arc seconds per pixel (660mm e.f.l. with 2.4um pixels) and I did a drizzle integration followed by a reduction to 0.94 arc seconds per pixel to produce a final image that recorded the Trapezium stars A, B, C, D, E, and F (the latter partially merged with star C). This reduction also just barely recorded the protoplanetary disks (propylids) G, H, and I. You need to look pretty closely to see the propylids at this image scale, but in the next post I've reproduced the drizzled master that has an image scale of 0.5 arc seconds per pixel and in that image the propylids are clearly visible.
Image processing was done with PixInsight and Photoshop CC2017.
Edited by james7ca, 17 March 2018 - 08:46 AM.