Bulletin Board

Latest Website Update [1 Aug 2015] >> M92 and a few galactic extras >> Don't forget the Object of the Season: NGC 1 and 2 >> New Galaxy of the Month for August >> New Double Stars for August >> Revised Double Star Section >> Revised Observations and Galaxies Sections

Observations, Galaxies and Double Stars by Name and Constellation

I've updated the Deep-Sky Observations and Galaxy of the Month sections of the website to provide lists by object name and constellation in addition to the articles themselves. I hope it'll make it much easier to find things. The Double Stars have now had the same treatment!

August 2015 - Picture of the Month

M92 revisited with some galactic extras

M92 and friends - Image Courtesy of David Davies

Images 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.

I first observed M92 visually several years ago and was struck by the beauty of this globular cluster that is often spoken of as the poor relation of the Great Cluster, M13 in Hercules. I understand that M92 is believed to contain stars that are nearly as old as the universe itself, since these stars contain just 0.5% of the metal elements that our sun contains. It is an intriguing object.

Therefore M92 has always been my list for imaging. Two years ago I succeeded in capturing a relatively low resolution image in black white with my ED80; clouds prevented capturing any colour data.

Friday 17 July produced a rare clear night with stable seeing and reasonable transparency. In planning the image capture I could see that there are many galaxies in the background of this area of sky and so offset the field of view of the image to also capture what I could of the background galaxies.

I elected to use my Equinox F/7.5 ED120 refractor rather than my faster Newtonian to get a wider field of view and as clean an image possible, without diffraction spikes. A test exposure time of five minutes showed that I would get sufficient signal but not saturate the brighter stars. To reduce the risk of not having a complete set of colour data, I captured a set of RGB images first and then captured the luminance data I could before the onset of dawn stopped work. Data capture started around midnight and I had to stop at 02:20 as the sky was brightening. I managed to capture two and half hours of data.

I've attached two images. The first is the complete LRGB image. The second image (NGC 6332) is a crop from the lower right part of the frame. This has been enlarged by a factor of two and is shown as a negative image. I have annotated it with the names of some of the galaxies that I've been able to identify from the NGC and LEDA catalogues.

Galaxies around NGC6332 - Image Courtesy of David Davies

The brightest galaxies are magnitude 13 to 14; the smaller galaxies still showing a distinct shape are around magnitude 16 to 17 and the faint, tiny smudges are around magnitude 18 to 19.

The faintest galaxy I've been able to identify is magnitude 19.2. I've also identified the double star HIP 84333 but my studies show that the apparent double visible in the image is an optical double; the true binary is only 0.4" from the primary and was discovered by the Hipparcos satellite.

The image scale of the galaxies image is 0.62 arc sec/pixel - half that of the main image image scale 1.24 arc sec per pixel.

The Equipment

  • Telescope: Skywatcher Equinox ED120.
  • Mount: Skywatcher EQ6.
  • Camera: QSI 583 with SX Lodestar as off-axis guider Automatic focussing with Scopefocus.

Image Processing notes

The colour subs were plagued by satellite trails so I used median stacking in Deep Sky Stacker to eliminate them (mostly). Pixinsight w used to align, calibrate and integrate the colour frames. Photoshop was used to assemble and finish the LRGB image with a little saturation boost applied to the stars and a little high pass sharpening applied to the galaxies.

David Davies (21 July 2015).

So there are some challenges to those with large telescopes and other imagers. Can you provide us with some observations of these objects?

I realise that Hercules is slipping to the West, but the nights are getting darker... and there's are always your archives to scour.

James Whinfrey - Website Administrator

August 2015 - Galaxy of the Month

NGC 7265 in Lacerta

This interactive image of the NGC 7265 group was provided by the Sloan Sky Survey using Aladin Sky Atlas. You can view a large overview image of the group too.

It is not often that we think of galaxies in the small constellation of Lacerta because it lies in the Milky Way region between Cygnus and Cassiopeia. There is however a section of the constellation that lies outside the Milky Way’s boundaries and approaches the border of Pegasus and it is here that we find the galaxies.

Our targets this month are a challenging group of galaxies associated with NGC 7265. The group is known as USGC U813. The group comprises of 8 galaxies including NGC 7264, UGC 12013 and UGC 12007, and this finder map should help you sort them out.

NGC 7265 itself is an E/S0 galaxy with an active core. NED currently leans towards giving NGC 7265 a classification of S0 (lenticular). This type of galaxy is normally only found in galaxy clusters so it must be possible that the NGC 7265 group is or has been associated with a much larger group. The distance to the group is probably of the order of 73 Mpc. The whole group appears to be associated with the Perseus super cluster of galaxies. None of the standard references cover NGC 7265 which is slightly surprising but may give some idea of the faintness of the group. I think this is probably one for telescopes in the 40cm+ class, certainly from the UK. I am not sure the UGC galaxies will be seen from the light polluted and crud filled skies we normally expect from the UK. NGC 7265 itself was discovered by Edouard Stephan in 1876 using a 31” sliver on glass reflector whilst NGC 7264 was found by Marth using Lassell’s 48” speculum metal reflector from Malta in 1863. NGC 7263 does not appear to be part of the same group of galaxies. Steve Gottleib in his NGC notes has observed all of the NGC galaxies in this region but they are described as faint and he was observing from high clear California skies. NGC 7264 looks like a smaller version of the classic edge on NGC 4565 in Coma from the images.

It will be interesting so see how much of this can be seen visually. It would also be interesting to see what amateur imagers can make of this group as there are no images either. I suspect that when hunting this group use a medium to high power eyepiece.

The group of galaxies around NGC 7274 is also associated with the NGC 7265 group but interestingly also seems to be included in the poor galaxy group catalogue as WBL 681 which does not seem to include NGC 7265 as it only includes the three NGC galaxies near 7274. These three galaxies were also discovered by Stephan in 1876.

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

August 2015 - Double Star of the Month

Lambda Cygni (20 47 24.563 +36 29 26.7) is easily found. Just move 3 degrees due north from epsilon Cygni, the left-hand star in the cross. One of Otto Struve's discoveries from Pulkova the seeing needs to be good to get a measure of the companion. The stars are magnitudes 4.7 and 6.3 but have always been separated by less than 1" although the angular distance between the stars is now roughly double that at discovery. Since 1990 the writer has observed the pair in 12 seasons and in that time the position angle has decreased by about 10 degrees. The current orbit has a period of 391 years but this is complicated by the fact that Hal McAlister and colleagues found the primary to be an interferometric binary with a period of 11 years and maximum separation of 0".05. There is some evidence that one of the three stars is also a single-lined spectroscopic binary. Lambda Cyg has a spectral type of B5Ve and is a rapid rotator surrounded by a circumstellar disk. Sir James South adds a faint companion, mag 9.7, at 106° and 83".

The sprawling constellation of Capricornus sits near the meridian on a northern summer night but locating stars in it apart from the third magnitude alpha and beta needs the help of a star atlas. However, starting with the brightest star of all, beta, by moving 3 degrees south and slightly east a trio of stars is encountered, all enclosed by a 1 degree field. Each of these is a visual double star and the subject of this column is omicron Cap = SHJ 324 (20 29 53.91 -18 34 59.4) the most southerly of the three. Smyth calls it omicron2 and notes that both components are to be found in Piazzi's catalogue. The WDS gives magnitudes of 5.9 and 6.7 and the separation is currently 21".9, down from 25" when found by William Herschel with a small decrease in the position angle, currently 238°. The Hipparcos catalogue gives the distance as 216 light years but with a formal error of 27% this is an indicator that there could possibly be another star nestling in the system.

Smyth calls both stars bluish, and whilst Sissy Haas regards them as almost equal, the report by Hartung notes that they are an 'unequal white pair'.

Bob Argyle - Double Star 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