Abell 70 + PGC187663: What does it take to see both?

[Clear Skies]

Hi all,

5 September I attempted to observe the galaxy PGC187663 in Aquila, in the background of the planetary nebula Abell 70, behind its northern edge. I was expecting to perhaps be able to pick up the faint glow of the galaxy in my 12" and did not expect to see anything of the nebula. The opposite was true. The nebula was visible quite clearly, confirmed with both a UHC and an OIII filter. The galaxy however, eluded me. Scope used was my 12" SCT with a 17mm Nagler.

What does it take to observe both objects? Anyone succesful using a 12", or smaller? Skies permitting I will attempt again next new Moon from a darker location.

Cheers,


Victor

[Marko]

With 12" you have not stated it but I'll assume you looked for the galaxy with an unfiltered view just as you would to see if you could see the central star, same reasons.

Here is an 18" description with use of NPB filter first for nebula observation and then slightly higher mag unfiltered gave best galaxy view. It was an amazing 21.7sqm and 6.9NELM night at 8000 feet (Mt Lassen in CA, USA) so that was likely to make the view close to ideal sky conditions. It was only later in writing up my notes at home that I came to realize the stronger glow on one side was the galaxy. In my notes I put observations or clarifications from DSS that was used later in brackets. I have two observations and both in 18" both mention the 'bar of nebulosity on N rim' but the one below has the most detail on the galaxy. The other observation states that unfiltered view did not show me the central star (for what that is worth).

Abell_70: NPB filter shows a donut of 1/20fov diameter [0.63'] where averted indicates the central open or dimmer portion of about 1/3 the diameter or about 20" dia open area. It is still glowing but just darker with averted in the central area. 7mmNag unfiltered available averted 100% of the time. There is brightness along north side in a bright line 20 degrees from EW that does not show up with the NPB FILTER [This is a galaxy].

So from this the nebula as well as galaxy were available unfiltered in 18" f/3.7 scope with ParaCorr which gave me 278x power. I also noted the line of glow was not seen with the NPB and that indicates the filter kills the galaxy (seems likely since the galaxy is so dim to start with).

[Clear Skies]

Thanks Marko.
I did indeed look for the galaxy unfiltered. No matter what the object, that is what I always do to start with. The surprise in this observation was that I did not expect to see even a hint of the nebula with the my scope under 21.1sqm skies. Later this month I will have 21.5sqm skies at a higher location so I better give it another try..!

[Marko]

I'll thank you right back in that your reminder of Abell 70 is timely. It is a curious sight to be sure and worth reobservation if only as an 'old friend' in the night sky.

I have found it curious and lucky at the same time that because we see only a 2D view we get assorted wonderful apparent associations and yet the objects can be nowhere near each other. There are numerous cases of this inability for our human eyes to know how far these things are to make it easy to just enjoy the hap-hazard 2D placement forming a nice view in the eyepiece from Earth. Speaking of such 'old friends' I was up real late last new moon to catch M38/Ngc1907 also Gem M35/Ngc2158 'apparent cluster pairs'. I ended my session on my first peek of the season of old Orion nebula high enough to be out of the 'low level muck' . I saw it last month but still in the 'muck'.

[Don Pensack]

This wasn't particularly hard at 304X in a 12.5" last new moon. I observed under the following conditions:
Seeing: 10/10 Superb.
Transparency: superb--extinction as low as I've ever seen.
Darkness--Good, at mag.21.43/sq.arc.sec.
The planetary, while more visible with an O-III filter, was still quite obvious without. I didn't see any elongation of the galaxy, but spotted it as a bright spot on one edge of the planetary, and it was obvious.
I suspect you had two problems keeping you from seeing it: too low a power, and possibly too much extinction.

[Steve Gottlieb]

I thought I'd mention that Abell 70 + PGC 187663 was an earlier OOTW, so there are more posts of this object here (http://www.deepskyforum.com/showthread.php?202-Object-of-the-Week-September-9-2012-Abell-70-%28PK-38-25-1)

Kent Wallace viewed Abell 70 with his C-8 and even mentioned seeing the planetary unfiltered with averted vision at 200x, but didn't mention seeing the galaxy (or a brighter spot). Keep in mind that the galaxy will probably appear as a fairly subtle brightening along the northern edge, and with 12" will probably not appear as an edge-on.

[Clear Skies]

Thank you all for your replies. Will definitely try again very soon: observing under dark skies in southern France ten days from now. Good to know it can be glimpsed in a 12"..!