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2 more groups - IC 2476 and Hickson 67 (last until June)

DSO Observing Report Sketching Visual
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#1 bphaneuf

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Posted 04 May 2024 - 12:23 PM

Here are the last two from the first and last day in May.  We're hitting the road for the month, but taking the binoculars!

 

IC 2476 galaxy group in Leo:

 

This group had also eluded me for some time but yielded to the conditions and greater familiarity with the star field by this time.  The whole group is faint, with IC 2476 by far the brightest at vmag 14.4 and the others in the upper 15s and 16s.  Not surprising as the group members range from 361-401 million ly out.  It consists of 5 members – IC 2476, 2478, 2479, PGC 1886684 and PGC 1886169.  The last galaxy in that list was not seen.  I could not find out if there’s any interaction among them, but did learn that 2476 is a “dying” radio source, whose activity in the core has mostly ceased but the lobes that were pushed out when it was active have not yet dissipated.  As a result, it’s been a valuable study as a stage in galactic evolution. 

 

 

Observing:  The well-populated star field was both a hindrance and a help, but a line of bright stars to the east stands out and moving from there to the west a neat triangle of stars that are not quite as bright comes into view.  All the stars are of near-equal magnitude, with the northern angle formed by a pair of stars.  The angle of the triangle pointing away from the line of stars has an extra star a bit further west that’s noticeably brighter.  Nice confirmation as there are triangles aplenty in the field.  2476 sits nearly in the center of the triangle, offset just a tad to the north side.  The other members of this group form a triangle of their own to the north-northeast.  The galaxy not seen is tucked up very close to 2476 and refused to puff into view.

 

IC 2476 is slightly oval along an E-W axis and brightens towards the center.  The lack of a stellar nucleus is perhaps an indication that this galaxy’s more active days are over. 

 

The round smudge of 2478 was seen next, nicely marked by the star pair that forms that corner of the triangle.  Quite persistent in AV, it also displayed a discernible but subtle core brightening.  At times it could be held in direct vision. 

 

2479 was the same size and shape, but lacked the core brightening and was less obvious.  Can’t be sure but I think I had it direct a couple times. 

 

PGC 1886684 was by far the hardest to capture.  At vmag 16.7 it’s a full magnitude fainter than the previous two.  It sits between 2476 and 2478 as a purely AV smudge, an ill-defined patch marginally brighter than the background.

 

Sketching: white pastel pencils and white pastel powder on Bachmore 92 lb. black multimedia paper.  A #5 pointed brush created all the galactic halos, with a 12/0 mini angular creating the cores for IC 2476 and 2478.

 

 

 IC 2476 group in Vir.jpg           IC 2476 group in Vir labelled.jpg

 

 

 

Hickson 67 – compact galaxy group in Virgo:

 

The four members of this group range between 345-363 million ly distance.  The dominant member is NGC 5306 at mag. 13.1, with the others ranging from 15.1-15.8.  5306 must have an interesting history given its double nucleus, but the only information I could locate was from this CN post (in memoriam) from June of 2012.  The group also carries the Vorontsov-Velyaminov catalog number 135 due to the two galaxies with which 5306 is interacting.

 

 

Observing:  Using the 21mm @ 145x as a finder shows a large amorphous area bounded by 9 bright HD catalogue stars.  An unfocused gaze reveals a hazy patch toward the northeast.  Mag 9 HD 120386 lies just to the south of it.  Zooming in with the 8mm @ 381x reveals that patch to be NGC 5306 (A) and its two close companions MCG-1-35-15 © and PGC 49036 (D).  MGC-1-35-13  (B) – an edge-on spiral was not seen at either magnification.  It took the 2x Power Mate to finally bring that one out.  The sketch uses the 8mm + 2x Power Mate FOV and the observing notes are from that magnification of 762x.

 

NGC 5306 (component A) is easily held in direct vision.  The halo is clear as is the bright but non-stellar nucleus.  I suspect that the double nucleus is not able to be observed in most amateur telescopes until maybe the 48” range or above and very high magnification indeed.  Maybe Mel with his 30”.   Mel, you listening?

 

Components C and D that flank 5306 are mostly AV objects, but persistent clear round spots that show a hint of brightening toward their centers.  They are visually detached from 5306, but I’m sure I was only seeing the cores. 

 

Component B was a bit frustrating as it’s ranked brighter than C and D, but it was tough to nail down.  Went back and forth between 235x, 381x and 762x a number of times trying to smoke it out.  It finally puffed into view as a 4:1 AV slash with no detail.  That was using 762x.  Photos show a prominent dust lane so perhaps that was masking the core glow. 

 

An interesting compact group particularly for the different morphologies involved. 

 

 

Sketching: white pastel pencils and white pastel powder on Bachmore 92 lb. black multimedia paper.  A #5 pointed brush drew NGC 5306 and components C & D.  The edge-on component B and NGC 5306’s nucleus were done with a 12/0 mini angular.

 

 

Hickson 67 - NGC 5306.jpg           Hickson 67 - NGC 5306 labelled.jpg

 

 

Thanks for looking!  See ya in June!

-b


  • KidOrion, Mel Bartels, Jef De Wit and 8 others like this

#2 Herodotus

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Posted 23 May 2024 - 07:47 PM

Just saw these, nice sketches and very interesting targets for sure.
  • bphaneuf likes this


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