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Sharing with you my quickie exposure... The Trifid nebula, aka M20 or NGC 6514, a popular and bright nebula about 4300 light years away in the constellation Sagittarius.
I had no plans for another object after imaging the "War and Peace" nebula and I didn't want to waste a clear night, so I pointed the scope at M20 and started exposing.
This image was taken through my Celestron 8" SCT on the CGEM at f6.3 using a cooled and astro-modded DSLR.
RGB subs: 6x60s, 5x120s, 5x180s, 5x240s, 4x300s
HII subs: 10x600s
OIII subs: 9x600s
Total Time: 04hr 21min.
Most of this image is natural color because I only used 10% of the HII and OIII stack to emphesize the detail in the red and blue hues.
Hello All again,
Sharing with you the other image I've taken of the Rho Ophiuchus/Scorpio region, two nights later.
This was taken with a Canon 40D DSLR and a 50mm Sigma lens.
Total integration time was 2 hours with 30, 60 and 120 second ISO800 subs.
I was bitten by the Messier bug back in the beginning of 2013. By the start of that summer I had seen over 70 Messiers with the help of my Helios NatureSport 10x50 binoculars, Sky-Watcher Explorer 130P and my two favourite dark sky sites: a “local” one in the north of the Cheshire plain and a location further afield in North Wales.
The objects that had eluded me were mainly the fainter galaxies in Ursa Major and Virgo and the southerly Messiers, i.e. those lying below -30 degrees in declination: M55, M54, M70 and M69 in Sagittarius and M6, M7 and M62 in Scorpius.
My 2013 summer holiday to Switzerland coincided with a new moon and some marvellously clear skies. To my great surprise and satisfaction I was able to bag all the southerly Messiers. The open star clusters M6 and M7 twinkled almost as bright as city lights in the 10x50 bins. Globular cluster M55 was large and diffuse and M54 was also a straightforward sighting in the bins. For the small and faint globular clusters of M69 and M70 I had to resort to my newly acquired SkyMaster 10x70 bins, and even then it was a struggle to see them. The 10x50 bins, however, were sufficient to pick out globular cluster M62 further west in Scorpius. The fact that these objects were 8 degrees higher in the sky than when seen from home was a key factor in my success.
Subsequent summer holidays in Portugal and Spain benefitted from being another 5 degrees further south, so once again with clear dark skies, the most southerly Messiers were easily seen. In fact, conditions were sufficiently favourable at our holiday home 80 miles south west of Barcelona, that M7 was a naked eye object. That sky was a wonder to behold!
As a side note, when locating M6 and M7 on these holidays I followed the instructions of my Messier guidebook which recommended navigating from the tail of Scorpius. More recently, after studying my star atlas, it was clear that navigating from the spout of the teapot asterism in Sagittarius was a better bet, especially from more northerly latitudes where only the top half of Scorpius is visible.
About a year ago I started to wonder if it might be possible to see M6 from my North Wales site, latitude of 53 degrees, as the sky there stays remarkably dark right down to the horizon. At that latitude M6 should lie almost 5 degrees above a low horizon. Alas, such things are a rarity in North Wales!
After several failed attempts last year and this, I celebrated success a couple of months back on 17th June. M6 was clearly visible as a faint fuzz in my 10x50 bins. By now I had graduated from the 130P to a Sky-Watcher Skyliner 250PX Dob. Looking through the Dob with a 17.3mm eyepiece, the cluster occupied a significant part of the 1 degree FOV. There was a suggestion of a "V" shape at its centre and a bright orange star (BM) glowed in the upper right of the eyepiece. I estimated M6 to be about 2 degrees above the hilly horizon so I knew straight away that M7 wouldn't be visible, as it lies 2.5 degrees further south than M6. Not yet beaten, I turned the Dob a few degrees west into Scorpius and with a "seat of the pants" navigation (due to a lack of any prominent star patterns) just managed to locate a faint M62 in Scorpius.
A reconnaissance of the local area uncovered another suitable viewing spot a couple of miles away where I estimated the horizon was 2 degrees lower which, in theory, gave the opportunity to see M7.
My first visit to this new site on 17th July was a disappointment as a band of thin, low lying cloud mostly obscured the area of interest.
My next visit on 24th July was a different story. I arrived at 11:15 when M6 and M7 should have been at their highest, and set up poste-haste. The sky wasn't fully dark yet and the only star in the teapot asterism of Sagittarius I could see with the naked eye was Nunki, the top of the handle. Thanks to my success in June, I was able to navigate quickly using my 10x50 bins to M6, which again showed as a definite fuzz. I then swept around the teapot looking keenly for Kaus Australis, the base of the spout which was roughly the same declination as M7. To my surprise and excitement I found it, so I knew M7 was at least above the horizon. I then navigated from the top of the spout, still using my 10x50 bins, to where I reckoned I would find M7 and sure enough, a very faint fuzz appeared. I then dashed over to my Dob using the same eyepiece as previously, navigated through the finderscope, and there in the eyepiece was M7, occupying most of the FOV! I could discern a definite "V" shape with 4 stars in each arm on a west-east axis. Looking through the binoculars, I estimated M7 to be about 1.5 degrees above the horizon, which fitted with my previous calculations.
I then mounted my Canon 500D on a tripod and fitted a 50mm f/1.7 lens. I took several photos of the teapot asterism (at ISO3200, 6 seconds exposure), hoping against hope to capture both M6 and M7 in the shots. When I got home I was very pleasantly surprised to find that I had been successful.
By 12:45 the sky had darkened in the south such that the teapot asterism was now clearly visible to the naked eye.
I then returned to my Dob, hoping to see the globular clusters of M69 (near the base of the spout), nearby M70 and M54 (near the base of the handle). I had success with each object: M69 and M70 were both faint fuzz balls, M54 was rather brighter but smaller. I then turned my attention further east with M55 in mind. I rehearsed star hopping with my bins a couple of times so that navigation with the Dob was straightforward. Looking through the eyepiece there was the mighty, but faint, globular cluster of M55.
In the combined sessions of 17th June and 24th July I saw all the southerly Messiers for the first time from this country - and from a latitude close to that of home. These viewings gave me the satisfaction of having seen all Messiers from a latitude of 53 degrees or higher.
So that is my story of the southerly Messiers.
I wonder what tales of frustration and success other observers can share about their experiences seeking out these low-lying objects, especially from UK latitudes?
Re-processed - Trifid Nebula in Sagittarius ( Messier 20, NGC 6514 ) - new PhotometricColorCalibration toolBy MikeODay
Re-processed 12th August 2017 using the new PhotometricColorCalibration tool from Pixinsight.
This function seeks to adjust the colour balance of the image by plate solving the image and comparing the colour of the stars in the image with the colour values for these stars as stored in various databases.
( please click / tap on image to see larger / sharper )
Trifid Nebula ( M20, NGC 6514 )
I manged to capture another 60 odd 240sec images in late July to add to the data I captured at the end of June ( Trifid Nebula WIP )
Trifid Nebula in Sagittarius ( Messier 20, NGC 6514 )
( please click / tap on image to see larger and sharper )'
and a crop of the main part of the nebula ...
I am quite pleased with how the colour balance turned out - especially the colours of the stars ( my goal has been to get the colours of the stars as close as I can to how they would look with "daylight" whitebalance and no light pollution / sky glow).
"High Dynamic Range" ( HDR ) image of the Trifid Nebula - built from exposures ranging from 1/8 to 240 seconds in duration.
Size: 52.2 x 35.5 arcmins.
Centre: 18h 2 min 30.8 sec, -22deg 57' 37.7''.
Orientation: up is -88.2 East of North ( ie. E^ N> ).
Orion Optics CT12 Newtonian ( mirror 300mm, fl 1200mm, f4 ).
Corrector: ASA 2" Coma Corrector Quattro 1.175x.
Effective Focal Length / Aperture : 1410mm f4.7.
Skywatcher AZ Eq6 GT.
TSOAG9 Off-Axis-Guider, Starlight Xpress Lodestar X2, PHD2 .
Nikon D5300 (unmodified) (sensor 23.5 x 15.6mm, 6016x4016 3.9um pixels).
Blue Mountains, Australia
Moderate light pollution ( pale green zone on darksitefinder.com map ).
12 sets of sub-images with exposure duration for each set doubling ( 1/8s to 240s ) all at ISO800.
Calibration: master bias, master flat and no darks.
Integration in 12 sets.
105 x 240sec main image.
5 each for exposures 1/8 to 120sec - to caputure highlights.
HDR combination using Pixinsight's PixelMath function.