Object of the Week August 12, 2012 - Barnards Galaxy with Ha Regions

Object of the Week August 12, 2012 – NGC 6822 with Ha Regions

Barred Irregular Galaxy

Sagittarius
RA 19 44 56.5 DEC -14 48 11

Size: 15.6' x 13.5' Mag: 9.3 (B) (MegaStar – RC3)

Deep Photo on Adventures In Space: http://astronomy-mall.com/Adventures...ce/barnard.htm

Nicely placed this new moon we find Barnard's Galaxy, NGC6822. This faint barred irregular galaxy in Sagittarius is a low surface brightness galaxy of a fair size that is viewable with both small an large scopes. Ngc6822 holds significance in astronomy for one reason due to Edwin Hubble's detection of 11 Cepheid variable stars in this galaxy which are used to accurately determine distance.

A fun project was to track down several of the Ha regions in this object in my 18" f/3.7 StarMaster. Here are two observations of mine on Ngc6822 in the 18" where the first one was from last year with the intent of tracking down 4 of the Ha regions and the other observation I only knew of the two brighter Ha regions. As recently as last night I have detected the glow of this galaxy in a 5" refractor from a 20.7 Sqm site. Deep photographs show even more Ha regions as more challanges.


8-27-2012 22:05 PST from a site well south-east of the bay area, CA. South is 'down' in my view.
NELM better than 6.6 with SQM 21.55 where I rated seeing as excellent and transparency very good (8/10)

NGC 6822 IC 4895 MCG -2-50-6 19 44 56.5 -14 48 11
Using 9mmNag, 216x with ParaCorr total sizes of 7/10fov [16'] x 4/10 fov [9'] Unfiltered shows the two northern H2 regions. The H2 region to lower left [W] of the other is brightest of the two unfiltered and both appear to bracket the glow one on either side of the north end of the glow in EW orientation to each other. 5mmNag 389x shows EW elongation of the brighter H2 region west of the other one. Looking for the very dim H2 regions we move co-linear west of the two H2 regions by their spacing to a field star. Now move 1/2 of this length to see the H2 regions. These are very dark targets that only present themselves in strained averted over 50% of the time that are closely spaced.

Another measurement without the Ha regions was interesting perhaps as well:
10-10-10 from same site but in lesser skies with seeing 8/10 but transparency 6/10

NGC 6822 IC 4895 MCG -2-50-6 19 44 56.5 -14 48 11
Using 9mmNag, 216x with ParaCorr Extends 3/4 x 1/2 fov [17x11'] up and to right [NS] Stands out well on East edge in 16mm. Appears as NS elongated shape. NPB filter we see the two knots appearing 6/10 of a field down and to left [N] from the bright field star at S end of the galaxy glow. The second knot is 1/5fov [4.5'] East of the 1st. both are similar brightness and maybe 1/80 fov [0.3'] in size. In unfiltered view all the glow appears as just that, a glow with no distinctly brighter glow. OIII filter was swapped in and I felt it offered a bit better contrast on the knots.

What do you see?

"GIVE IT A GO AND LET US KNOW"

GOOD LUCK AND GREAT VIEWING!

Quite a challenge for my 4" refractor and for my eyes that refused to really cooperate due to overall lack of sleep these past few days. As usual the TV Ethos 13mm got the job done but I am still kicking myself in the re@r for not viewing the finder chart beforehand (not for finding the FOV, but for actually knowing beforehand what to look for, due to low surface brightness). Will surely revisit :)

I would like to thank the forum for posting plenty of challenges that can be taken on by amateurs like me with smaller instruments. Although I cannot see what you kind folks can with the kind of mirrors being toted around, it is still a pleasure to be able to track this and that faint fuzzy!

How I confirmed with 5" on last Sat night (in Orion ST120) was I noted where the glow was (averted and scope movement) then made note of just south of the galaxy is a distinct EW 4:1 elongated rectangle of mag 9-10 stars that is 15' below the center of Ngc6822 and is about 14' east to west and 4' N-S. One star is on the long side that is more south midway so it is very distinct but averted view for 5" scope. I think you could see the glow at a darker site in a 4" and maybe even at the sort of site I was at but just barely (mag 20.6 or so). It was absolutely there and another guy I was there with (also with visual experience) confirmed the glow.

Marko, I am a newb (I don't consider my forays with a Go-To SCT as qualifying for amateur astronomy) and my adventures into astronomy officially commenced May this year when I got a 4" refractor and a manual alt/az mount.

My eyes require a lot of training as evidenced by my struggle last night. It was a good night last night @ 21.30 at our location (oh, yes!) and I was able to see NGC6822 in the end. Took a lot of shaking of the OTA and strictly averted vision for me and RolandosCY confirmed the FOV which was exactly as you mention. He was able to see NGC6822 clearly in my scope but for me (again, a newb) it was an on/off situation and barely detectable. Hopefully I will be able to pull in slightly more detail next time, conditions permitting.

And thank you for the tips above :) This hobby is one of constant learning and and hopefully assistance and advise will keep on coming. No other way to learn... :D

Oh yes, NGC 6822 is one of those objects that really require experience to see and enjoy, even under good skies. On Monday night I could readily see it with direct vision in Nicos' Stellarvue, yet for a while it was really hard for Nicos to detect it. This is a common problem with persons not accustomed to seeing large, very low surface brightness objects. In the 18" of course it was readily visible, at times hinting into granulation. I have experienced this effect once more in an extremely transparent night at a darker site with my old 12", but it was not as distinct as it was last Monday (I guess the extra six inches do help!). HGopefully we'll be given another chance later this week to re-observe it...

Nice OOTW Marc, thanks for showing us you detail observing and the labeled chart.

Minimum aperture for me was 4" Newton under good, but not perfect skies (NELM around 6.5mag). The galaxy was easily visible as 8' long, 1:2 elongated glow with direct vision. To my surprise I could catch the HII region IC 1308 as a stellar spot. I could not detect Hubble V, maybe to close to the 13mag star SW.

With 16" I could detect 3 HII regions, see sketch below. I could not separate Hubble I and III.

I quick look with 24" showed the insolent bright HII regions. I have to revisit the galaxy and especially try the structure of Hubble I and III with my 27".

sketch with 16" (home)
Attachment 282

In excellent conditions (7200' in the Sierras) Barnard's Galaxy was quite evident in my 80mm Stellarvue finder at 25x as a faint, elongated glow and it was just at the edge of visibility in my 15x50 IS binoculars but even then Hubble I/III was barely seen in my 18".

Another challenging project, by the way, is tracking down Hubble VII, a 16th magnitude globular cluster near the center of the galaxy.

Last days I tried again Hubble I and III. Conditions were nearly perfect, 27" telescope and good to very good seeing. The two Hubbles were visible with direct vision and could separate easily. But my hope to detect the ring-shape of Hubble III was negative. In fact, Hubble III was a round glow with involved stars.

After some discussion with SteveG I am beginning to question if I had seen only the glow from involved stars for Hubble I and III. I should downgrade those two to questionable observations until farther study on my own confirms those. They took a significant amount of effort and time in any case. My error would have been in not making a distinction between seeing 'any' glow at all in those positions VS detection of Ha glow around stars. This again was in an 18" f/4.2 (f/3.7 with paracorr) using 5mm eyepiece