PDA

View Full Version : Observing report, 2015 March 23rd, Texas Hill country



akarsh
March 25th, 2015, 07:02 AM
Hello DSF

(Sorry if this becomes a double post. I think I made a mistake trying to post this the last time.)

The transparency was not very good, there was substantial moonlight until 11:35 PM, the humidity was expected to hit 100% at around 2 AM, and clouds were expected by 4 AM, but I still went observing because I really wanted to drive out of Austin and do something, having wasted an entire spring break.

I was just looking at some Messiers with 10x50 binoculars before moonset, so as to at least do a Messier marathon and have fun with some bright NGC objects if not anything serious. I casually set up my telescope, and was just about ready to observe as the moon set, knowing that I might have to even take it down in 2 hours and drive back. I thought I was under some pretty crappy skies even after moon set, since the transparency wasn't looking good anyway -- but the darkness of the site is such that there is nothing much other than star light for the water to scatter. So I was pleasantly surprised when I noticed a very conspicuous Gegenschein in Virgo, with even hints of the zodiacal band! A few more tests (the appearance of spiral arms of M 101) convinced me that the skies were good enough for serious work. This was completely unexpected, so I was naturally very pleased to be able to go after things that I did not expect to be able to.

Two interesting things came out of the observing run, namely Holmberg VII and Holmberg VIII. While Holmberg VIII was expected, VII was not but it still yielded.

(Observations made with an 18" f/4.5 Obsession classic dob on an equatorial platform.)

Holmberg VII

To find Holmberg VII, I found M 49 by naïve pointing, then galaxy-hopped down to NGC 4532 and the bright star nearby. I moved into the appropriate field and without knowing the exact position, looked around for faint patches, and I happened to notice one. I uncontrollably uttered an explitive at this point, because I had definitely not expected to see it without knowing the precise position. Then confirmed the exact position with a POSS image. The galaxy was by no means bright, but it was easier than many of the Palomar objects. The observation was confirmed repeatedly. The galaxy appeared to take up about 2 arcminutes in diameter. The asterism seen to the side of the galaxy in the POSS image was harder to see than the galaxy, but occasionally some of the stars were visible. The best views were with 10mm Delos and 14mm Pentax (thank you, Jimi!).

Holmberg VIII

To find Holmberg VIII, I moved in from NGC 5033 towards the object, and as I was moving the telescope, a patch caught my eye. Indeed, it was Holmberg VIII, more easier than Holmberg VII. Unlike with Holmberg VII, VIII could be held steadily with averted vision. Exact position confirmed against POSS images. I tried to see if I could observe the irregular '?' shape seen on the POSS blue image, but all I could say was that the north end was thicker than the south end. Best views with 10mm Delos and 14mm Pentax.

Other objects that I observed were Hickson groups 53, 54 (I used Reiner's atlas; thank you Reiner!) and Arp galaxies 84, 266 and 270.

I was going to try Pyxis GC, but the aperture was obstructed by trees -- I hadn't planned for it as I wasn't expecting to be able to do any serious observing at all. I could not reconfirm Palomar 3 from last time. Again, while I could sense something and verify some particular details, I would like to have a more concrete observation at some point. I also culled off NGC 3132 from OOTW here, but once again, had to observe with half the aperture covered by trees, so nothing substantial.

Clear Skies!

Regards
Akarsh

Ivan Maly
March 25th, 2015, 03:11 PM
That's some cool observing, Akarsh. (And should I add that ANY is way better than none ;) Here is Arp 266, a sketch and notes, from last year. 12", up to 375x, SQM 21.67.

http://2.bp.blogspot.com/-4gD5pTAP8bs/U1wkAz3fbjI/AAAAAAAABDE/idUOxiPaiT8/s1600/2014-04-23+NGC+4861.jpg

NGC 4861, 40 kly, SBsm, 40 Mly. Arp 266. The compact HII region on the S end has been cataloged as UGC 8098. It was already described by Herschel as a star. VV 797, KPG 362. The identity of IC 3961 and derivative UGC and PGC designations with the NGC galaxy or the southern bright knot is inconsistent.

Uwe Glahn
March 25th, 2015, 09:15 PM
Hi Akarsh,

I did all Holmberg's several years ago and write my notes down in a small project side (http://www.deepsky-visuell.de/Projekte/Holmberg.htm). You can use google translator because of the German language. Nice objects and small but fine catalog.

akarsh
March 26th, 2015, 08:45 AM
Ivan, thanks for pointing out that the "star" is actually a HII region. I didn't realize that either until now. Also, very nice and detailed sketch. I have a lot to learn :)

Uwe, very incidentally, I looked at your page right after posting this report, and noticed that you have a series on Holmberg galaxies. I can understand some German, except that I need to familiarize myself with the vocabulary that you use for observing (terms like geringe Flächenhelligkeit were totally new to me for example). Your notes are indeed extremely detailed, as is quite expected of a seasoned and very accomplished visual observer like you. Like I said to Ivan, I have a lot to learn from you too. It is amazing that you managed to distill out Holmberg IX in a 16". This gives me a little more foolish confidence to attempt the same in my 18" -- the last I tried (TSP 2012), I could not see it, and had to take recourse to a 25", but some things have changed since then. Thank you for your wonderful website (which I need to explore more). Your Arp page is very interesting too.

Regards
Akarsh

akarsh
March 26th, 2015, 08:51 AM
Uwe, what does AP here mean? "bei mittlerer AP ist eine etwa 3,5' große"

Regards
Akarsh

Uwe Glahn
March 29th, 2015, 05:23 PM
Hi Akarsh,

thanks for the warm words. Unfortunately the ARP side is not actual any more because Martin S. is not active any more.
HLM IX is definitely within reach with 16", perhaps also with aperture around 12". I call it "horse-head-effect" (B33) because you need to kn ow what to look at exactly. Up from the first light of HLM IX other visual observations will be much easier.
AP means exit pupil.