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The open cluster M37 contains almost 2000 stars and is spread across 20 light years. Most of the stars are young blue/white but it also contains red giant orange suns which provide considerable colour contrast. I first imaged M37 a couple of years ago but I decided to add to the data since I was never entirely happy about the quality of the some of the sub-frames. I also decided to try out some of my newly learnt stellar processing techniques to improve the data which I describe below for anyone that might be interested. Since I often image in non-ideal conditions, I sometimes find that the red stacked channel has a larger FWHM values than the blue or green channels, if I combine this data to obtain an RGB image. the result is a red fringe around the stars. For blue stars, this is particularly apparent and creates magenta halos. This time, I decided to shrink the red channel via a ring mask using PI's erosion filter. The ring mask protects the star core, minimizing damage and core dimming. The main issue is generating a good ring mask which captures the majority of the red fringing. After watching one of the Adam Block's Pixinsight's tutorials ( https://adamblockstudios.com/) on how to de-emphase stars, I decided to apply a technique he recommends. Basically, you first create a star mask which includes all the stars and all the halos. This mask should be white across the star and halo and slightly feathered around the edges. Having done this, you then subtract from this the Red channel lum information to create the ring mask. The reason this creates an accurate ring mask is that the lum data contains accurate information on how the light profile various from the stars center. So, for example, at the stars core, the star mask will be close to 1 (in PI everything is normalised to 1), whilst the lum information will also be close to 1, so if you subtract one from the other you end up with something that is close to 0 (eg black) at the core. Thus, at the core you will be protecting the star's core almost 100%. Outside of the star mask (eg outside of the halos) you will have 0, whilst in the lum channel you might have 0.2 (say representing a non-stellar structure), if you subtract 0.2 from 0 you get 0, since you cannot have negative values in PI, so outside the star mask the ring mask will be 0 eg black. Within the halo, the ring mask will mimic the stars halo hence generating an accurate ring mask. The LRGB image below was taken with my Esprit 150 and represents just over 15 hours integration time. Alan LIGHTS: L:23, R:26, G:23, B:21 x 600s, BIAS:100, DARKS:30, FLATS:40 all at -20C.

The view from my centre of town garden is both physically & light-pollution restricted. Anything below 25 degrees is out of the question, anything West below 60 degrees behind bright buildings and a huge South-Easterly sycamore tree combines with a neighbour’s security & outdoor fairy-light obsession to make a fairly narrow observing window to say the least. The local park about 5 mins away potentially offers a darker & wider alternative which I confirmed this week on a late night dog comfort-break excursion. All of a sudden, from a spot around the 22 on the rugby pitch, a break in the cloud presented a full vista of Orion, Taurus, both Canis, Auriga, Gemini, Perseus & Cassiopeia- I was star-struck to the point where my furry companion thought I’d lost it. Messier clusters in Auriga I’d struggled to get in the eyepiece from the garden were immediately visible as naked-eye diamond-dust, the Pleiades sparkled and M42 glowed. It was ten minutes of magic. Inspired by my mid-week bonus I hatched a plan to head to the park the next time a clear-sky coincided with a non-school night. Tonight promised a couple of clear hours around midnight but dodgy weather earlier in the evening combined with the feeling that lugging the Mak and tripod to the park might be tough to justify as a lockdown exercise break, confined me to a late night stroll armed only with my trusty 10x50s. Having overcome the nagging sensation I might be mistaken for some kind of lurking pervert, I set off for the park. In the end I got about 15 minutes before fog bubbled up from the river. But even this fleeting glimpse allowed me to confirm I can now easily find the Messier clusters in Auriga and put my bins straight onto the double cluster in Perseus, things I’d never seen before lockdown. As the fog closed in I took a sweep of the alpha Perseii cluster and Pleiades, my current binocular greatest hits, and headed home happy.

Since I needed more practice at my star field processing, particularly with respect to star colour, I thought I'd have a go at M37. My default exposure duration is 600s subs which I find works well from my site and allows me to capture faint background objects. Unfortunately, for M37 I noticed that this length of exposure, whilst it does not create saturated stars, it does take my camera into the non-linear response region for some of the bright stars. A consequence is that star colours can become compromised. So, I thought this would be a good opportunity to try out the Pixinsight Repaired HSV separation script, which can be used to correct this non-linear effect. I also decided to shoot a small amount of Lum since I like the glowing effect it produces. Since I was interested in capturing quite faint objects in addition to containing the bright stars, I performed both a high and low strength DDP stretch of the Lum which I subsequently blended and then mixed with the RGB data. The result is below and represents just over 5 hours integration time. Alan LIGHTS: L:5, R:10, G:9, B:8 x 600s. DARKS:30, FLATS:40, BIAS:100 all at -20C.

I grabbed the frames for this image on the night of the 5th Nov as a quick target after having got a lot more data on the Bubble. ST2000XM, with a WO FLT110 at f5.7 - R:G:B = 35:35:35 (5min subs) at 1x1. Processed in Pixinsight - it's tricky to hold the colour in the stars for these images - but really like the colour of the deep red carbon star V358 Aur (colour index ~1.57, V mag 12.something) in the lower portion of the image. Thanks for looking!

This is my first image of 2017. 2 hours each of R, G and B captured on the nights of 1 and 2 January 2017:

All Just had an hour with the 12x50 bins following AN magazines November binocular sky feature. Basicly a hunt for M's 36, 37 and 38. Found them fairly quickly Starting from Alnath to HIP25291. Just on the edge of the fov was M36 a sharpish fuzzie. Once located both M37 and M38 could both be located on the edge of fov above and below M36, both appearing as less distinct faint fuzzies. For all 3 M's i had to use averted vision Pleased as punch with that hour and 3 more M's chalked off and my first chance to scan Auriga. I also passed many rich star fields that i havent identified due to the initial hunt for M's

Hi folks, Another reprocess of old data (from last December) to see if my skills have improved. Here's one which includes the Flaming Star nebula, rather deeper than my previous effort: Flaming Star - includes M36, M37, M38, IC 405, IC 410 and IC 417 The full sized 4096 pixel square version is available here (6 MB download) - beware, horrors may await the avid pixel peeper! The challenges for this one were to separate out the faint Ha from some residual sensor noise and to decide how many stars were enough - there were a lot more in the RGB subs. At the image scale offered by the 165mm focal length lens the reflection nebulosity was difficult to extract. I decided where it was by doing a blink comparison of the 1000 second blue stack with the full RGB image (the version with all the stars plus some nebulosity) and then it was a matter of isolating it from the bright stars that were illuminating it. It was added to the Photoshop stack of Ha (no stars) plus RGB (just stars) and the final challenge was deciding how strongly to show it - the reflection nebulosity should certainly be weaker but then it risks geting lost in the artificially strong Ha signal. Something that I didn't find in the original processing of the data last year is the "sugar cage" just creeping in at the bottom of the image at about six-thirty. Has anyone got a shot of the full object? Bob. Shooting Information: 8 x 1000 seconds exposures of Ha 5 x 200 seconds through each of Red, Green and Blue 3 x 1000 seconds through the Blue filter for reflection nebulosity Camera: FLI ML16803 cooled to -25°C. Lens: 165mm focal length f/2.8 Pentax medium format Pointing at: 5h 25m, +34° 30'