Observations of Some Faint Galaxies

[MarkM]

I really enjoy hunting down and observing faint galaxies. Like people, no two galaxies are alike. Sure, a lot of times the sight is not visually spectacular, but I get a kick out of looking in on these unique objects which are so far away.

During Spring, I had no problem seeing mag 12ish galaxies from my home site. But now, humidity-induced light pollution severely limits my late night sessions to the brighter (albeit limited), Messier objects (like M102 and M77). Early morning sessions are a bit better in that I can catch mag 10-11 objects if their surface brightness (sb) is not too dim.

So, at an increasing frequency, it’s off to the dark site with the scope, equipped with charts and good intentions for observing these faint fuzzies.

Described below are some faint galaxies that I have observed this month from my favorite dark site along with a few lessons I have learned while honing my DSO hunting skills. Most observation were made with a 13mm Nagler Type 6 EP which gives 92x in my scope. An Orion Q70 (giving 38x) was used when a star hop was needed to get to the final location.

Objects from Deep Sky Atlas
I tend to get a bit frustrated if I don’t include more easily found items on my observing menu. For these, I like to mine the maps found here ([Registered users can see links. ]) within constellations I know will be in sight at the time of interest. The galaxies listed on this site are limited to mag 11 and brighter, meaning I can just punch in the NGC number into the COL of my GOTO scope, slew the scope, and (usually) observe the item directly in the eyepiece without additional hunting.

I have seen the following galaxies using this list:

NGC 6946 (m8.8, sb13.8, CYG): a large diffuse galaxy that appeared oblong and possibly contained a dust lane
NGC 584 (m10.5, sb12.9, CET): small round galaxy with a bright core
NGC 524 (m10.3, sb12.3, PSC): a pleasingly compact, oblong galaxy with a bright core which forms an isosceles triangle with nearby mag 9-10 stars; looked nice at 184x also
NGC 520 (m11.4, sb13.6, PSC): this is a faint, elongated galaxy that exhibits a “weak core” (i.e., lack of stellar concentration).

Objects from Cartes du Ciel
I like to use this freeware program to sweep an area of the sky for DSOs whose magnitude is limited by parameters I preset. I typically only go after mag 13.2 or brighter objects. Prior experience has shown that a chart is necessary for final pinpointing of these items. They are visible (either direct or with averted vision), but only if I know just where to look. Most often I will wear an eyepatch over my open, non-observing eye and just stare long and hard into the EP at the desired spot until the target becomes evident to my dark-adapted eye. All of these galaxies showed greater extent with averted vision; some could only be seen with averted vision (typically mag 12.8 and fainter).

The following galaxies were observed using this method:

NGC 452 (m12.6, sb13.2, PSC): I could just barely see this one as a tiny smudge with averted vision
NGC 420 (m12.1, sb13.5, PSC): this very small galaxy was readily evident with averted vision
NGC 410 (m11.5, sb12.7, PSC): I likde this sizeable, elongated galaxy due to its shape despite being faint and weakly concentrated

Arp 331 Cluster
NGC 384 (m13.1, sb13.1, PSC): only a tiny hint of a large diffuse patch of light using averted vision; this galaxy likely represents the mag limit of my scope during these humid months for non-stellar objects.
NGC 380 (m12.5, sb123.1, PSC): actually saw this one with direct vision as an oblong body with a bright core.

Abell 262 Cluster
NGC 708 (m12.7, sb14.9, AND): very close to the “Baby Dipper” mentioned below, this object was best seen with averted vision and seemed elongated
NGC 753 (m12.3, sb13.9, TRI): this is a dim, but large and round galaxy with a bright core. Previous observations at the dark site were inconclusive which highlights the role atmospherics play in seeing these faint objects.
NGC 679 (m12.3, sb13.8, AND): this object is quite small, has a bright core, and seemed slightly elongated
NGC 669 (m12.3, sb12.8, TRI): this galaxy is small, is slightly elongated and has a weakly concentrated core.

**Abell 262 is a very enjoyable cluster because within a 6 degree FOV of all of these galaxies there is a small asterism that looks a lot like the Little Dipper (the “Baby Dipper”). This little cluster proved very handy for star hopping to the exact spot for each member. Attached is a screenshot from Cartes du Ciel that shows this asterism at the 12 o’clock position between the 2 outermost Telrad finder circles centered on NGC 753. A wider view shows this asterism as one vertex of a pentagon with bright stars Epsilon TRI, Beta TRI, 58 AND and open cluster NGC 752.**

“Missing Objects” from the Internet AA Catalog
This is a new project I have undertaken in which I look for items not previously described on this AA website ([Registered users can see links. ]). I then run a quick check using Starry Night to check for suitability for current viewing and acceptable magnitude (typically less than mag 13.5). Success here also requires use of a tailored chart; the COL alone just gets me in the neighborhood.

NGC 237 (m13, sb13.3, CET): the only item seen to date from this list, this galaxy was very difficult to glimpse (averted vision) as it was extremely faint and small (I think it is round).

Lessons learned
a) There is no harmonization between programs with respect to galaxy magnitude. For some objects, I have seen three different values (varying by more than one magnitude) depending on if I use Cartes du Ciel, Starry Night or the XT8i’s COL.
I have no idea which value is correct; I use those listed by Cartes du Ciel for consistency.

b) I have lost several hours of valuable observing time by using charts that are no longer tailored to my observing time and date. Last night, I got hopelessly lost finding landmarks while searching for “missing” NGC galaxy 1056; this brings me to point c).

c) If no progress is made to locate an item of interest after say 10 minutes, it may be best to cut losses and move on. I have wasted too much time through stubborn determination to find my object when the session could have been more fruitful if I had given up until another time.

d) Increasingly, I am fond of finding a target rich area that puts 3 or more observable galaxies onto one map. If I can find a landmark on that map, I have a good chance to observe more than just one DSO; if not, I can move on to the next map along the lines of point c) above.

Thanks for reading and Happy Hunting.

[dmbryan]

Thanks for the read. That is good advice.