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Latest Website Update [1 Sep 2015] >> New Galaxy of the Month for September >> M27 is our Picture of the Month >> New Double Stars for September >> M92 and a few galactic extras >> Don't forget the Object of the Season: NGC 1 and 2

September 2015 - Picture of the Month

M27 - The Dumbbell Nebula

I took my first images of M27, the Dumbbell Nebula in Vulpecula three years ago with a DSLR camera and this year thought to return to it to see what my QSI camera would reveal. I have read that in 1991, it was discovered that there exists a very faint outer halo around the main nebula that extends out to at least twice the 8 x 6 arc minute extent of the 'normal' nebula but is around 1000 times fainter. I wondered, therefore, if I had any chance of revealing this outer halo.

I gathered nine hours of H-alpha, Oxygen III and Sulphur II narrow band data and 3.5 hours of LRGB data during the three weeks 22 July to 10 August and have generated the two attached images.

An image of M27 using the HST palette - Image Courtesy of David Davies

The first image is a narrow band HST palette rendering with an LRGB image of the stars blended with it. In this image S II data are assigned to red, H-alpha to green and O III to blue.

An LRGB image of M27 - Image Courtesy of David Davies

The second image is also narrow band but with with H-alpha and S II data are added together and assigned to red (their normal colour), O III is assigned to blue and a synthetic green has been generated as a combination of O III (80%) and H-alpha (20%). This image has also been blended with the LRGB image and has the more normal looking colours.

I have read that the outer halo is cooler than the hotter central nebula and we can see the chaotic boundary between the two as the hotter core pushes outwards. We can see the cool outer halo of gas from the original supergiant star penetrated by columns of glowing hydrogen-alpha originating from the central star in the regions from the top to the left side: 1 o' clock round to 9 o'clock.I'm wondering if what we are seeing is evidence of the central star precessing and periodically having outbursts of radiation. At the 4 o'clock location there is a powerful jet which seems to extend as an extremely faint extension beyond the outer halo itself.

Image details

23' 35" X 16' 51" at 0.97 arc sec / pixel Exposure times: three hours, each of narrow band data in 20 minute frames; two hours of luminance and 30 minutes each of RGB in five minute frames

Equipment

254 mm Newtonian at F/4 plus TV Paracorr giving F/4.5 QSI 583 plus Astrodon LRGB and 3 nm narrow band filters

David Davies (21 August 2015).

All images are courtesy of David Davies, Cambridge, UK. Please click on the images for the high resolution versions. For more images from David please visit his Flickr Photostream.

September 2015 - Double Star of the Month

Nestling in the region about 4 degrees north following the upper left-hand corner of the Square of Pegasus, AC 1 (HIP1669) (00 20 54.10 +32 58 40.9) seems to have been a little neglected by the double star community. It doesn't even have a note in the WDS catalogue but things may change now that Henry Zirm has published an orbit for it.

It was discovered by Alvan Clark using a 7.125-inch object glass of his own make in October 1856, and published in MNRAS a year later with additional notes by W. R. Dawes. At the time of discovery it was 0".4 apart and Dawes was of the opinion that it escaped the attention of F. G. W. Struve at Pulkovo because it was too close at that time.

This view has been borne out - the stars are now easily measurable with a 20-cm refractor. The magnitudes are 7.3 and 8.3. Hartung notes that the stars are 'deep-yellow' and also points out the presence of a orange-red star some 4'.5 SW (HR 59 - spectral type K5III). Zirm's orbit with a projected period of 525 years is clearly provisional as the stars are close to maximum separation and only 12 degrees has been described in the apparent orbit. The author found 289°s; and 1".9 in autumn 2014.

Psi 1, 2, and 3 Aquarii are three bright stars of visual magnitude 4.2, 4.4 and 5.0 respectively. They can be found about 3 degrees east of the centre of the line joining alpha Peg to Fomalhaut, in a region rather low down from the UK but filled with interesting visual doubles.

Some 4 degrees directly below psi 3 is 94 Aquarii (23 19 06.51 -13 27 30.4) a fine, wide pair which is worth seeking out. Its mag 5.3 and 7.0 stars appeared yellow and orange to Hartung who was able to observe them close to the zenith whilst the Reverend Webb noted a reddish glare in A whilst B appeared greenish.

The proper motion of the pair amounts to more than 0".3 per year so the fact that the change recorded in separation over 200 years amounts to only 2 arc seconds tells us that this is a physical pair, and it is located 69 light years away. In 1976 McAlister and colleagues discovered that B was a close pair (MCA 74) and it has subsequently turned out to be a binary of short period. It rotates every 6.3 years and the separation is never more than 0".2.

Bob Argyle - Double Star Section Director

September 2015 - Galaxy of the Month

NGC 48 Group in Andromeda

This interactive image of the NGC 48 group was provided by the Sloan Sky Survey using Aladin Sky Atlas. We've also provided a finder chart for the group too.

Browsing through the Clusters section of the Webb Society Deep-Sky Observer's Handbook (WSDSOH) Vol 5 I came across the description of the cluster of galaxies around NGC 48. Apart from their appearance in the WSDSOH the group does not appear to be in any of the other standard references and appears to have been neglected.

The galaxies appear to be a true physical group catalogued as WBL 005. The group consists of the three NGC galaxies NGC 48, 49 and 51 which were first discovered by Lewis Swift in 1885 using a 16” refractor and three IC galaxies IC 1534, 1535 and 1536, all discovered by Barnard in 1888 using a 12” refractor.

The clusters appears to be two parallel triplets with the NGC group and the IC group. Steve Gottlieb does have notes for all the galaxies in the group with a 17.5” telescope but describes them as fairly faint. NGC 51 would appear to be the brightest of the group. This may not be surprising as they have photographic magnitudes of around 14 for the NGC group and around 15 for the IC group.

The group lies on the border of the constellations of Andromeda and Cassiopeia and would appear to consist of two spirals and 4 lenticular S0 galaxies which is slightly interesting unless they are part of a much larger coarse grouping. There is a problem with the distance of NGC 48 as the redshift measurements are wildly discordant. However as it appears to be part of the group with the other 5 it must be at the 63 Mpc distance rather than 43 Mpc which some of the redshifts indicate. The galaxies may be an isolated group that is part of the western end of the Perseus supercluster.

They do however appear to be almost as ignored by the professional community as the amateur as apart from basic data there is really not a lot of information about them. NGC 51 may be a mild form of AGN known as a LINER. There are almost certainly gravitational interactions going on within the group which may be distorting the galaxies and causing some starburst behaviour. IC 1535 was home to SN 2000cz discovered by Mark Armstrong in the UK. IC 1536 is also classified as a Markarian starburst galaxy which is rather odd given is morphology of E/S0.

The will make both an interesting visual as well as imaging challenge as I could find no images apart from the DSS on the net.

Owen Brazell - Galaxy Section Director

Object of the Season (Summer 2015)

Galaxy Pair NGC 1 and 2 in Pegasus

Galaxy Pair NGC 1 and 2 in Pegasus will be announced in DSO 168, and the results will be published in DSO 170.

The optical galaxy pair NGC 1 and NGC 2 in Pegasus: NGC 1 is the northern object - Image Courtesy of Sloan Digital Sky Survey (SDSS) This image was supplied by the Sloan Digital Sky Survey (SDSS). NGC 1 is the northern object.

NGC 1

Position (2000)
0 07 15.9 +27 42 32 (Peg)
Visual magnitude
12.9 mag
PA
120°
Size
1.7' x 1.2'
Distance
206 Mly
Other Designations
GC 1, UGC 57, MCG 4-1-25, CGCG 477-54, KCPG 2A, PGC 564

NGC 2

Position (2000)
0 07 17.1 +27 40 43 (Peg)
Visual magnitude
14.2 mag
PA
112°
Size
1.0' x 0.6
Distance
347 Mly
Other Designations
GC 6246, UGC 59, MCG 4-1-26, CGCG 477-55, KCPG 2B, PGC 567

Wolfgang Steinicke - Nebulae and Clusters Section Director

Deep-Sky Observer (DSO) No 153 - Free Sample

DSO153 Cover

This free journal is DSO 153 from 2010. You can download it as a PDF file onto your computer by right clicking the link below and choosing either 'Save Target As' or 'Save Link As'...

Download DSO 153 (2MB PDF file)

Clear Skies Observing Guides (CSOG)

Courtesy of Victor van Wulfen.

Clear Skies Observing Guides Banner

Webb Deep-Sky Society member Victor van Wulfen produces the CSOG. He's recently relaunched the website with version 2.1, so now would be a good time to take a look.

The Brightest Planetary Nebulae Observing Atlas - 2nd Edition

Massimo Zecchin has just completed the 2nd Edition of an atlas of planetary nebulae observed with small apertures and from suburban locations, entitled: "The Brightest Planetary Nebulae Observing Atlas".

Massimo has kindly made the atlas is freely available in two versions, Black (for display) and White (printer friendly with the images in negative).

The 2nd Edition contains:

  • Six additional objects.
  • Data of visual magnitude, central star magnitude and object size from the Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (SEC catalogue) and in a few cases from the Saguaro Astronomy Club database (SAC catalogue).
  • Calculated surficial brightness for any object (in magnitude per square arcsec).
  • Six additionaltables showing the objects sorted by magnitude, surficial brightness, size, central star mag, constellation and declination.
  • A general position map.

Either version of the atlas can be downloaded as a PDF file onto your computer by right clicking the respective image above and choosing either Save Target As or Save Link As...

Please note that the Black version is 14MB and the White version 10MB