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Latest Website Update [16 March 2015] >> New observations of NGC 1501 and M35 >> A new Galaxy of the Month >> A new Object of the Season for Spring 2015 >> March Double Star of the Month

The Object of the Season now has its own section. It's on the main menu above.

March 2015 - Galaxy of the Month

NGC 2713 in Hydra

This interactive image of the NGC 2713 group was provided by the Sloan Sky Survey using Aladin Sky Atlas. This finder chart should help you locate these galaxies.

First discovered by Albert Marth in 1864 using William Lassell’s 48" Speculum metal telescope from Malta the pair of galaxies NGC 2713 and NGC 2716 will provide an interesting challenge for deep sky observers from mid northern climes. The pair was also independently rediscovered by d’Arrest in 1866.

Residing in the head of Hydra NGC 2713 appears to form a physical pair with the nearby galaxy NGC 2716. The pair reside approximately 53 Mpc from the earth. NGC 2713 itself is a barred spiral that is highly inclined to our line of sight. NGC 2716 is a bit more difficult to classify but appears to be either an elliptical or a lenticular galaxy, recent classifications tend to the SB0 classification. NGC 2713 is classified as a radio galaxy, possibly from interactions with its companion. It may also host a weak AGN. It was also host to a type 1 supernova in 1968.

The nearby galaxy IC 2426 may also be associated with this pair as its radial velocity is very similar, and in fact the trio is classified as a compact group number 83 in the catalogue compact groups from the UGZ. IC 2426 at 15th mag is going to be a lot more difficult to see but should fit in the same field as the others with a medium power eyepiece (say 220x)

At about 12th magnitude NGC 2713 is not going to be easy to see but it should be visible in a 22cm telescope. NGC 2716 will be a bit more tricky but should be visible in a similar sized telescope. The pair should be visible in the same field with a medium power eyepiece.

AGC 732 - Image Courtesy the Sloan Sky Survey

This interactive image of AGC 732 was provided by the Sloan Sky Survey.

Owners of very large telescopes might like to see if they can see any of the components of the galaxy cluster AGC 732 just to the north of NGC 2716. The brightest galaxies here would be around 17th magnitude so I suspect they are going to be on the edge for all but the largest amateur telescopes.

Owen Brazell - Galaxy Section Director

Object of the Season (Spring 2015)

NGC 6572 in Ophiuchus

Planetary Nebula NGC 6572 in Ophiuchus will be announced in DSO 167, and the results will be published in DSO 169.

NGC6572 - Image Courtesy of Hubble Space Telescope (HST) This image was supplied by the Hubble Space Telescope (HST).

Position (2000)
18 12 06.4 +06 51 15 (Oph)
Visual magnitude
8.1 mag
Central Star
13.6 mag
Size
0.6' x 0.4'
Distance
2500 ly
Other Designations
Σ 6, h 2000, GC 4390, PK 34+11-1, VV 159, ARO 7

Wolfgang Steinicke - Nebulae and Clusters Section Director

March 2015 - Double Star of the Month

With Cancer now moving inexorably towards the western horizon, its stars are becoming more comfortably accessible to the classical refractor user and one of its finest doubles is 57 Cnc (08 54 14.70 +30 34 45.0).

According to Webb, it is a pair of crocus-yellow stars which are not quite equal in brightness (magnitudes 6.1 and 6.4). There has been little motion of any kind save a small increase in both position angle and separation with the result that the separation is now well over 1".

It is an ideal test for a 7.5-cm refractor. Webb was able to divide it at x144 on his 3.7-inch Tulley OG, and the writer found 1".55 with the Cambridge 8-inch in 2006.

The pair is almost certainly binary in nature as the proper motion of the system would have separated them a long time ago. A faint component can be found at 55" and PA 202° which appears fixed. The WDS gives its magnitude as 9.2.

57 Cnc is about 2.5 degrees north following the spectacular wide pair iota Cnc.

Gamma Sextantis, also called 8 Sextantis (09 53 30.47 -08 06 17.7) was discovered on 1852 Apr 7 by Alvan Clark with a 12-cm aperture. As it happens he observed the star at a suitable part of its orbit but this discovery is a good indication of the quality of Clark's telescopes.

He said, reporting his finds in Monthly Notices for 1857, Notwthstanding the moderate meridional altitude of of 8 Sextantis at Dorpat (about 24°), it may reasonably be doubted whether its duplicity would have been left to be discovered with a 4 3/4-inch object-glass, however perfect, if no change had occurred in its appearance since Struve's scrutiny of that part of the heavens.

The separation of this close pair is never wider than 0".6. It reached maximum separation in its 77.8 year cycle in 2002 and is now closing again. By Spring 2015 it will be at 44°, 0".54 and the low declination means that it will be a significant test for 20-cm and its more likely that a good, steady air will be essential to resolve it, especially as there is a considerable difference in brightness between the components - A is 5.4 and B is 6.4. Hipparcos places the system at 278 light years distance and the primary is an A1 dwarf.

To find gamma Sextantis, locate alpha Hya and move 5 degrees east.

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