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It was only nautical dark in the nights here in Norway when i took these, but gave narrowband a try with my QHY5L-II-M anyway, and the results are not bad at all for such a camera i think. It's noisy, but i guess with this little data and a planetary/guide-cam i guess that's to be expected. With more time i think it will give decent results. Taken with the QHY5L-II-M cooled to around -5c and and Olympus OM 50mm F/1.8 lens at F/2.8 OIII 8.5nm: 10x 600s with gain at 20. Ha 7nm: 15x 600s with gain at 12 (i think). No darks, flats or bias.
I lost astro dark a couple of weeks back. I thought, therefore, that I would try capturing narrowband during nautical darkness on the basis that I may as well do something with all the gear. I ended up with 6 hours of Ha and 6 Hours of OIII captured at my home observatory using my Esprit 120 and QSI 690 atop a Mesu 200 mount. Filters are Astrodon and exposures were 30 minutes each. Processing in PixInsight and Adobe Photoshop. I cropped the image slightly to eliminate a couple of brighter stars at the edge of the frame. I'd be interested to hear what people think.
Finally got done stacking the few hundred frames, aligning them, and processing them for the high dynamic range. Then came a nightmare - registar was unable to align my channels... Well, after 2-3 hours i finally got them all aligned, just to find out the OIII really did more bad then good, so i dripped it and went for a bicolor instead to get more details. It don't look too good in high/full res, especially as I've used 3x drizzle, but for this little data, manual alignment, and my poor tracking - I'm quite happy. The image was captures with the Polemaster on the Explorer 200 guided by the QHY5L-II. And the bicolor consists of NIR and Ha data instead of the usual Ha and OIII. NIR data is from 742nm and 23x 60sec, 59x 5sec, and 172x 1sec. Ha data consists of 18x 30sec and 100x 1sec. Total exposure is a low 41 min 45 sec, with a total of 372 frames. Edit: I just realised i posted this in the wrong section, if a mod could move it to deep sky i'd be thankful.
The Crescent Nebula NGC 6888 The Crescent Nebula rides on the Swan’s neck in Cygnus in a dense swathe of Milky Way stars - an ideal target for my first bi-colour image with my new Astrodon 3nm Ha and OIII filters and Esprit 150 telescope. The nebula was discovered by William Herschel on 15th September, 1792 and he described it as ‘A double star of the 8th magnitude with a faint south preceding milky ray joining to it.8’ long by 1.5’ broad’. This double star is not the prominent star with an apparent companion close to the heart of the nebula, rather, it is ADS13515 at the 2 o’clock position on the nebula’s bright periphery. The bright star off-centre of the nebula is particularly significant as this is the star that is powering the emissions from the surrounding gas cloud. This magnitude +7.5 star, HD192163, is of the Wolf-Rayet type and is also designated WR-136. Charles Wolf and Georges Rayet first described wolf-Rayet stars in 1867 following detection of their broad emission lines. The Wolf-Rayet stage applies to stars with an original mass in excess of 30 times our own Sun’s mass. This stage comes late in the star's evolution when a rapidly expanding shell of hot gas is powered outwards by the stellar wind only to collide with the much slower-moving gas clouds that were ejected thousands of years previously when the star entered its Red Giant phase. These forceful collisions produce a shock wave that generates an enormous amount of energy including wavelengths within the light spectrum, allowing us to observe them. This complex process displays as an arc of bright nebulosity that we identify as the Crescent Nebula. Long exposure images fill in this arc producing a crab-shell shaped nebulous region rich in Hydrogen Alpha and doubly ionised Oxygen emissions. WR-136 is fated to go supernova at some time in the future – watch this space! Image Stats Mount: Mesu 200 Telescope: Sky-Watcher Esprit 150 ED Pro CCD Camera: QSI 683 WSG-8 Sampling: 1.04”/pixel Guiding: OAG/LodeStar Filters: Astrodon 3nm Ha and 3nm OIII Exposure: 30 x 1800 sec Ha, 15 x 1800 sec OIII Date: 11/06/17 + 19/06/17 – much of which was under Lunar illumination Calibration: Bias, Darks & Flats Object Stats RA: 20° 12’ 04.6” Dec: 38° 30’ 46.0” Magnitude: +10.0 Distance: 4700 light years The Crescent Nebula – NGC 6888 Comparison of Ha and OIII data We imagers (well me anyway!) tend to think that Ha is the all-powerful emission line in nebulous objects but it is interesting to compare the Ha and OIII data for this structure as there is an enormous amount of OIII emission present in The Crescent Nebula.
While i was indeed satisfied with my HaRGB picture of M27, i couldn't resist giving a bicolor a go as i only needed some OIII data. Taken with the QHY5L-II-M and the Explorer 200. Camera cooled, i can't remember exact temp, but i believe around -10c. 7nm Ha: 47x 60 sec, gain = 1000 in firecapture 8.5nm OIII: 60x 60 sec, gain = 1000 in firecapture