An image of the Orion Nebula, M42 and M43, shot for demo purposes, taken through my standard (not Edge HD model) Celestron C9.25 inch SCT for 2300mm focal length at f/10. This was all unguided just for fun on a night I was shooting the 8-day-old Moon nearby above Orion. So this was taken in a bright moonlit sky and with light haze in the sky. This shows what is possible by stacking lots of very short though still well-exposed exposures even under less than ideal sky conditions, and with simple techniques. I used higher than normal ISOs for this to keep exposures very short to avoid trailing from the lack of guiding. However, it helps that this is the brightest nebula in the sky! The exposure blending retains the bright core and Trepezium stars while bringing what I could of the fainter tendrils that were visible in the moonlight and haze. TECHNICAL This is a stack of 32 x 6-second (!) exposures at ISO 6400, 24 x 6 seconds at ISO 3200, and 12 x 6-seconds at ISO 1600 for the core, all with the Sony a7III, and blended with luminosity masks. All alignments and stacking with Photoshop. So this did take a fair amount of skilled processing to make this look good. LENR dark frames were applied in camera to each image. This was with the Astro-Physics Mach One mount.
The Pleiades in Taurus, and the California Nebula, NGC 1499, in Perseus. The small blue reflection nebula at centre right is IC 348. This is a stack of 5 x 6 minute exposures with the 135mm Canon L-Series lens at f/2.8 and Canon 5D MkII at ISO 800. From home on a clear winter's night. Original exposures were technically overexposed but processed up well with huge increases in contrast introduced at every stage, from RAW to layered Photoshop, to final flattened TIFF. Several masks employed to equallize (flatten) the brightness gradients across the image from radial lens vignetting, linear edge camera lens box shadowing, and linear sky gradients. But having originals that were overexposed provided lots of signal, despite having only 5 exposures median combined, allowing the very faint nebulas to be brought out without significant noise. Having a cold (-5°C) camera helped too.
The Pleiades star cluster, or Seven Sisters, aka Messier 45, in Taurus. The brightest part of the reflection nebula around the Pleiades at bottom is the Merope Nebula, IC 349. In this image. I’ve shot long exposures at low ISO speeds to record faint structure at low noise, to allow me to bring out the faint dusty nebulosity all around the region in processing. This is a stack of 10 x 12 minute exposures with the filter-modified Canon 5D MkII at ISO 400 through the TMB 92mm apo refractor at f/4.5 with the Borg. 0.85x field flattener/reducer. Taken from New Mexico, Nov 17, 2014.
