Abell 4 and Hickson 16

Hello,

My first two sketches with 18". Inversed and slightly modified in GIMP.
I'm disappointed with them, but since I remember at school I was always the worst when it came to drawing/sketching anything...
The Abell 4 was supprizingly easy at 286x (Pentax XW7), visible without an OIII filter with averted vision and with OIII directly. Is the listed visual magnitude of this object (16.7 mag) really correct? The nearby galaxy PGC 2201006 (16.12 mag) was much harder to see.

http://s12.postimage.org/fw5a5t9rx/Abell_4.jpg

http://s15.postimage.org/c0qs1cl8r/H16.jpg

Out with the 18". I bet that was most enjoyable.

I am having some trouble determining the object PGC 2201006 but Abell 4 and the nearby 3 stars are distinct in the drawing.
One thing of note is directly adjacent to Abell 4 is a thin galaxy, CGCG 539-91 at mag 15.6 and I have noticed that my notes do not mention it at all. I shall have to revisit this pair.

Ehh... my mistake. I saw the galaxy marked with a circle on the picture below - the PGC 2816330.
The one marked with a rectangle (PGC 10427) I failed to see.

http://s8.postimage.org/tpzk72jpx/Abell4.jpg

Uggh, this is a confusing situation. CGCG 539-91, does not refer the faint edge-on close northwest of Abell 4 (as indicated by Megastar), but rather Abell 4, itself! I know that sounds contradictory as the CGCG is a galaxy catalogue, but they mislabeled some objects that are not galaxies, and Abell 4 is one of them. Unfortunately, that means PGC 10427 is also not the edge-on, but again refers to the planetary. Obviously, there IS a galaxy there, but i's too faint to have been picked up by the CGCG, which only goes to mag 15.7 blue photographic mag.

You will find the little edge-on in NED as 2MFGC 2191 (see http://tinyurl.com/98qomok) and it is catalogued in HyperLeda as PGC 2201333 (see http://tinyurl.com/9lbpc5z). HyperLeda give a B magnitude of 17.12 +/- 0.50, so this a pretty dim object. Hope that clears up the confusion!

Thanks Steve. I now don't feel so bad for not having noticed it right next to Abell 4. If it were mag 15.4 it is odd that I would not have seen it. Of course that leads to the question of who has seen it and in what type of scope.

I have looked at this a lot and I sure do not remember the edge on by Abell 4 to be that dim?

Have you seen it in you're 18" Steve?

Certainly the LEDA mag may be off, but I haven't seen it in my 18". On the other hand, I'm usually looking at Abell 4 with an OIII or NPB filter!

17,1bmag seems to be realistic to me.

I never saw anything from the edge-on in my 16" for sure and I tried it several times. Ordinarily I reaches the 17bmag once in a while with the 16" under very good conditions. So in combination with its surface brightness and thin morphology a hard target for 16"-18". But I knew a good fried who catches the edge-on with his 20".

I for one have this on my target re-visit list as this closeby near-edge-on has peaked my curiosity. Maybe in these next few months as Perseus gets closer to meridian.

Mark I would like to here how you do with the edge on, I have seen it in my old 25" but that is the smallest scope I have tried it with.

Give it a go and let us know! :D

2MFGC 02191 has a J magnitude of 13.517 within an ellipse whose semi-major axis is 14.9” [The 2MASS Extended sources (IPAC/UMass, 2003-2006) VII/233/xsc ] and 13.48 in a ”fiducial elliptical Kron radius” of 18.0” [2MASS-selected Flat Galaxy Catalog (2MFGC) (Mitronova+, 2004) J/other/BSAO/57.5/catalog ]. According to Brian Skiff an approximate J to V conversion is plus two magnitudes, so either source gives about magnitude 15½ for the galaxy.
I’ve observed Abell 4, but made no note of the galaxy – not even a failure to see it. It’s entirely possible that I didn’t know it was there, and I’d be unlikely to notice it at that magnitude unless I was looking for it.
Sue

What was the aperture of that abell 4 observation Sue?

I will be looking for sure in my 18 the next two months for sure with assorted unfiltered views.

Mark,

I've logged Abell 4 on two occasions, with a 10-inch. Here are the observations.

12-20-06, 8:20 pm EST, 254/1494mm Newtonian, Seeing: poor, Transparency: poor
166x with UHC filter: Faintly visible with averted vision. Intermittent.
213x with UHC filter: Can hold it more steadily.
[I made a little sketch that shows a small round disk and two nearby stars. The annularity is not shown.]
1-17-07, 8:40 pm EST, 254/1494mm Newtonian, 166x and 213x with UHC and OIII filters, Transparency: fair
Visible with averted vision in all cases. Round. About 1/3' across. Featureless. UHC works better than OIII.

Sue