Object of the Week August 18, 2013 - NGC 247 & Burbidge's Chain

Object of the Week August 18, 2013
NGC 247 & Burbidge's Chain
Cetus


Position - NGC 247
RA 00 47 08.6
DEC -20 45 38

Mag = 9.7(B); Size 20.0'x5.0'; SB = 14.4 (All magnitudes taken from SkyTools)

Type: Dwarf Spiral Galaxy
NGC 247 is a member of the Sculptor Group, along with NGC 55, NGC 300, NGC 253, and NGC 7793, along with 10 or 12 others. This is the closest galaxy group to our Local Group at about 11 or 12 million LY's away.

In my 25" it is easy enough to see, but its 9.7 magnitude is misleading because it is large, and therefore has a low surface brightness. There is a 9.5 magnitude foreground star at the brighter, skinnier southern end, and the slightly wider northern end is dimmer, and it is not easy to detect the actual edge of the galaxy, it just gradually fades away. I only just read that this guy is sometimes called The Needle's Eye galaxy because of a large dark area centered near the northern end, and sure enough, in deep photos there indeed seems to be a dark patch, making the whole thing reminiscent of a rather plump needle. I don't know if this feature is visible or not, I never knew to look for it and it certainly didn't jump out at me... let us know if you've seen it!

I observed NGC 247 in the first place because it is the jumping-off point for locating the tiny string of faint galaxies otherwise known as Burbidge's Chain, located a scant 16 arcminutes north-northeast of the center of NGC 247. The (4) components of Burbidge's Chain are:

a = MCG-4-3-10, mag 14.6(B)

b = MCG-4-3-13, mag 14.8(B)

c = MCG-4-3-11, mag 16.0(B)

d = MCG-4-3-12, mag 17.5(B)

Attachment 831Attachment 832



I've observed this little string of tiny galaxies several times over the years, most recently at CalStar a few of years ago, and in 25" there is no trouble seeing 3 of the 4 galaxies, with the "d" component being a certified stinker. I was observing with Greg LaFlamme, an experienced observer with much younger eyes, and Greg said it was just an occasional flicker in the eyepiece for a small percentage of the time. After trying for many minutes, I thought that perhaps I saw it, too... but someone once told me I was gullible, and I believed him... so maybe I did, maybe I didn't. The night was good but not great. I think I'll try it at CalStar again, in October.

“Give it a go and let us know!”

Coincidentally I was planning to reobserve this group (or "group") in detail just last night. But the forecast changed. Now we will have to wait till the Moon is out of the morning sky. So far I believe I've only seen the main NGC galaxy with my 4" f/5.5 Televue. And since I am not O'Meara, I did not record any details in it ;) It is actually remarkable that in his Caldwell book he sketched a couple of the galaxy's brightest compact HII regions - as if they were superimposed stars.

Hi Paul and Ivan,

I've observed NGC 247 and Burbidge's Chain just once but it was during a fabulous night at Steens Mountain in September 2008. Here are my notes and sketch:

"Great Field! NGC 247 is huge, bright and detailed and worth a sketch on its own, but with Burbidge's Chain in the same fov this is irresistible. The faintest galaxy in the chain is mag 16.7 and has a SB of 14.2 so it took extreme AV to barely detect. An added bonus is ESO 540-19, a nice mag 14.1 galaxy on the other side of 247. Sweet! 253x and 408x, 21.95 SQM."

This was a very dark and transparent night at 7400 feet so this is likely as good a view I'll ever have of this group, and even then galaxy C was tough to see with a 28 inch scope. Hopefully I'll be able to have another good look at it in the next few months.

Attachment 833 Attachment 834

Howard, I took the liberty to indicate on your sketch what I think is the brightest HII region in this galaxy.

Attachment 835


EDIT: Alright, maybe after all it's a star next to it...

Paul,

I could also only detect the three brightest members with my old 16". I did not try it with my 27" but 17,5bmag seems to be possible.

16", 100x-257x, NELM 7m+, Seeing III
Attachment 837

Quote:

---

Originally Posted by Uwe Glahn

Paul,

I could also only detect the three brightest members with my old 16". I did not try it with my 27" but 17,5bmag seems to be possible.

16", 100x-257x, NELM 7m+, Seeing III
Attachment 837

---

Uwe, I agree that mag 17.5 is possible with my 25", but apparently not on the nights I have viewed Burbidge's Chain. I will keep trying, and expect to succeed one of these days.

Have seen 3 but not the d member in a 33" dob that in general is not often in a very clean or aligned state. As a shared view I was not armed with the eyepieces I would have tended to try to use for best exit pupil and my observing techniques were not as well developed as these days. My 18 would not get the 'd' ever but I suspect with care and an ideal night it just may be available in a 24" in great shape. Being that this great challenge objects is coming around nowadays it is a timely post Paul. Thanks for remembering.

Quick post - Shneor and I saw D at Shot Rock with my 6mm ZAO-II in his 22".

Hi

Very interesting objects!! I will try with 16 "!! NGC 247 and this group is at my next observationplan! Thanks for this presentation!!

Clear Skys
Hajü
www.astromerk.de

This was a great challenge for my 18"! I had attempted this group twice since Paul introduced the group to me, both from Xyliatos, a prime location on the mountains of Cyprus, but only "A" was visible with certainty, as from that location this sky area is brighter than the rest of the sky.

On Friday evening though, I found myself at Lysos, a far more desolate area on the western part of the island, situated at the edge of extensive mountain forests at 2,000ft. With a rock steady SQM 21.55 sky, I was able to identify three of the four members of the chain. "A" was a piece of cake, a round patch with a steady light profile. Component B was much harder but once I spotted it I could hold it with direct vision as a featureless little blob. Component "C" was weird in that I spotted it easily before "B", but then I had more trouble holding "C" steady, it was more of an averted vision object. Component "D" was just not visible to me however hard I tried. But still, getting three out of the four members was very rewarding. In my accompanying sketch, both "B" and "C" seem approximately similar, but there was no way I could prepare a sketch showing the faintness of "C" - it would be lost in the processing...

This galaxy is tough! As I mentioned I'd seen it without difficulty in a 4", but details are another matter entirely. In September a few days after the absolutely spectacular conditions that enabled my deep view of IC 1613 posted here earlier I was driving again to our club site (not my usual remote one) full of hope. The transparency turned out to be only ordinary however. I measured 21.20 mag/sq arcsec near the culminating Beta Cet; it was 21.30 overhead. 45 minutes on NGC 247 with the 16" showed that a) the galaxy is most intriguing and b) better conditions are needed to go after real details in it. The brevity of my journal record conveys the disappointment:

NGC 247 at 45x elongated 7-8x1 NS. S end punctuated by a star. Core appears closer to this end, and the N end extends asymmetrically farther, at least to the W of another comparable star. At 225x (Ethos 8) only the core is clearly visible. 02:45.