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Latest Website Update [1 Feb 2015] >> February Galaxy of the Month >> February Double Star of the Month >> DSO 166 >> Observations of STF 644

The Deep Sky Observer (DSO) issue 166 is out now.

February 2015 - Double Star of the Month

In mid-February, Gemini passes the meridian at 10pm and offers an excellent opportunity to view some of the fine double and binary stars in this constellation. One of the less-well known systems is 20 Gem (06 32 18.52 +17 47 03.4) which is eaily found about 3 degrees north preceding the bright star gamma Gem. Wil Tirion's Cambridge Star Atlas shows another double star about a degree south of 20. This is STT143 (6.2, 10.4, 103°, 7".6 with a fainter third component at 345° and 47"). Also known as STF924, 20 Gem offers a beautiful pair of stars which Webb noted as topaz yellow and cerulean blue, but as these are the exact hues noted by Smyth in the Bedford catalogue it may be assumed that Webb was merely repeating the Bedford colours. More recently Sissy Haas finds both stars to be gloss-white.

There is little relative motion between the stars and the current situation is that the PA is 211° and the separation 20".2. Hipparcos found the determination of the parallax of star A difficult and finds a distance of 262 light years with an error of 30%. This is no doubt due to the motion induced by the duplicity of A confirmed by both occultation observations and also directly as a spectroscopic binary.

Looking about 1° slightly north preceding the V = 4.4 star q Puppis, one will alight on the wide pairs DUN 67 (08 13 58.31 -36 19 20.2) and DUN 68 about 1.5 arc mins south and west of it. DUN 67 consists of stars of magnitude 5.0 and 6.0 which are currently separated by 66 arc seconds and PA 174°. The separation is slowly decreasing. Hartung chooses not to include them is his book 'Astronomical Objects for Southern Telescopes' but Gould with 175-mm finds both stars to be pale yellow and notes the existence of several fainter pairs in the area. The components of DUN 68 are both mag 7.3 but form a wider pair than its neighbour. The PA is 25° and the separation is 125" and increasing.

The whole region is fine with the large scattered star cluster NGC 2546 about 1.5° further south adding further reason to take in the area with a pair of binoculars as well. Both pairs are at the same distance from us within the stated errors of the Hipparcos parallaxes.

Bob Argyle - Double Star Section Director

January 2015 - Picture of the Month

Sh2-155 The Cave Nebula in Cepheus

Our images this month are courtesy of David Davies from Cambridge in the UK. They provide an interesting comparison of the difference aperture can make when imaging nebulae. Please click on either image for the high resolution version. For more images from David please visit his Flickr Photostream.

I've been collecting data for an image of the Cave Nebula over four nights during December (5, 7, 13 15) and it has been a chapter of carelessness and frustration. I ended up binning hours of data after discovering it was slightly out of focus or was captured with the wrong filters. In the end I did some work on what I could rescue and the attached image is the result.

I set off trying to image the Cave in narrow-band but soon discovered that although the main cup-shaped nebula is rated as reasonably bright (integrated magnitude 7) it covers around 15 arc minutes of sky and is quite faint. The surrounding nebulosity comprising emission, reflection and dark nebulae is much fainter. Hydrogen-alpha emission can be acquired fairly readily but oxygen III and sulphur II emissions are very faint indeed. I decided to cut my losses and abandoned my acquisition of oxygen and sulphur, changed the filter wheel to RGB and acquired around an hour of each.

I was interested to see the Cave in its context and chose to image it with my ED120 refractor plus a reducer/flattener to give a field of view of 81 x 61 arc minutes. The attached image is a crop to approximately 60 x 60 arc minutes.

The Cave Nebula (Sh2-155) with an Equinox ED120 - Image Courtesy of David Davies

The image is Hydrogen-alpha, RGB; four hours of hydrogen-alpha in 20 minute subs; 132 minutes of RGB in 8-minute subs; all binned 1 x 1. Processing was in Pixinsight with a final touch-up in Photoshop.

  • Telescope is Skywatcher Equinox ED120 with a Skywatcher X0.85 reducer/flattener.
  • Camera is a QSI 583 wsg with Astrodon LRGB and 3 nm narrow band filters and Lodestar guide camera.
  • Mount is a Skywatcher NEQ6 controlled via EQMOD.
  • Image capture was with Nebulosity and Scopefocus for automatic focusing.

I was curious to see what my 10-inch Newtonian would make of it so here is the Cave again but this time captured with a 10-inch Newtonian. The faster optics and longer exposures have yielded a deeper image.

The Cave Nebula (Sh2-155) with a 10 inch newtonian - Image Courtesy of David Davies

A hydrogen-alpha RGB image captured on the nights of 19 and 24 December 2014 from Cambridge, UK. Two hours each of RGB in 10-minute subs plus one hour of hydrogen-alpha in 20-minute subs.

  • Telescope is a 10-inch Newtonian plus Televue Paracorr at F/4.5.
  • Camera is a QSI 583 wsg with a Lodestar camera as off-axis guider.
  • Mount is a Skywatcher NEQ6.
  • Image processing with PixInsight and Photoshop.

February 2015 - Galaxy of the Month

NGC 2275 Group in Gemini

NGC2275 Group - Image Courtesy the Sloan Sky Survey

This image the NGC 2275 group was provided by the Sloan Sky Survey, and this finder chart should help you locate these galaxies.

Finding galaxies in the winter constellation is always a challenge as most are quite faint and in general overlooked. With Gemini riding high on the meridian on February nights the challenge was to find a galaxy that was not really just for imagers. The NGC 2274/5 pair seemed to be a good challenge. There are not many observations of this galaxy pair and it is not included in either the NSOG or L&S. Both galaxies were discovered by William Herschel (who else ☺) in 1786.

NGC 2274 is the brighter of the two being an elliptical galaxy. At 12th magnitude this may be a challenge to find. Its companion NGC 2275 is actually much fainter and is an unclassified spiral. It appears to be undergoing some form of interaction as one of its spirals arms is much more obvious than the other. I am sure it would have made Arp’s famous catalogue if it was a brighter pair.

The pair is actually part of a small group of galaxies which has been variously catalogued as LGG 139 or WBL 121. The group consists of the four galaxies, NGC 2274, 2275, 2290 and UGC 3537. NGC 2290 is actually quite a distance from the others at 47’ of arc away. It appears with another group of galaxies which are in fact unrelated. NGC 2290 was also discovered by William Herschel but in 1793. The separation is due to the fact that the group is relatively close to us at about 4.6 Mpc so the group is spread out on the sky.

NGC 2274 and 2275 have been reported with apertures as small as 15cm from very dark sites but I suspect that probably 30cm will be needed from most normal sites, certainly to see NGC 2275. The other galaxy in the group UGC 3537 appears to be a face on spiral and is quite faint and is going to be a challenge to see unless you have a large telescope or use video or CCD imaging.

NGC2290 - Image Courtesy the Sloan Sky Survey

This image of NGC 2290 was provided by the Sloan Sky Survey.

The group of galaxies around NGC 2290 will also make a nice target but will be a challenge for large telescope owners as these galaxies are much fainter.

Owen Brazell - Galaxy Section Director

Object of the Season (Winter 2014/15)

NGC 4449 in Canes Venatici

Irregular galaxy NGC 4449 in Canes Venatici will be announced in DSO 166, and the results will be published in DSO 168.

NGC4449 - Image Courtesy of Hubble Space Telescope (HST) Please click on the image for a high resolution version taken by the Hubble Space Telescope (HST).

Position (2000)
12 28 11.0 +44 05 33 (CVn)
Visual magnitude
9.4 mag
Type
IBm
Size
5.5' x 3.6'
Distance
12.5 Mio. ly
Other Designations
I 213, h 1281, GC 3002, UGC 7592, CGCG 216-5, MCG 7-26-9, PGC 40973

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)

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