M101 dissected (almost…)
May 26th 2017; 1:30 AM, Dijkgatsbos/Wieringerwerf, The Netherlands
Darkness has by now reached its maximum. But it’s too bad the SQM halts at 21.1; a nice score where I’m living and within an hour drive from home, but a week ago it was still 21.4… It can be blamed on the “grey nights”, a phenomenon that everyone who lives above 48 degrees will be facing for the next two months…. Good thing is that tonight the transparancy is very, very good and the seeing is not too bad either. After a small hesitation, I decide to seize this last opportunity to sketch M101.
After receiving my 16″ scope I am now finally able to make out some of the spiral arm structure of this monstrous galaxy, filling up the field of view and surrounding a somewhat better visible core.
The Pinwheel Galaxy
I’m used to seeing only a faint, round veil of light in my 10″ with this galaxy but not this time though… Armed with a detailed drawing and the book “Cosmic Challenge” (by Phil Harrington) I smile when the object enters the field… the galaxy waves back at me with more arms than I ever thought possible, although the whole appearance is still VERY flimsy. If you don’t know exactly what to look for, then there is a chance that you will see right through it. Otherwise you will only see the dim pearl in the heart of the beast.
For the sketch I settle with a 14mm eyepiece, giving a magnification of 129x and an exit pupil of 3.2, which is a bit too high, but at least I’m able to capture the whole galaxy in a pleasing proportion.
Counting HII regions
There are numerous of HII regions hiding in the slender arms of this galaxy and ten in total should be within the reach of my telescope, but only under perfect circumstances. So I switch eyepieces to a 7mm, which darkens the background enough and turns out to generate sufficient magnification to identify them (or at least most of them) after consulting my detailed drawing. And here’s where (I think) I saw them:
In order of appearance:
- NGC 5471 – Very bright, small and round. Resembles a galaxy
- NGC 5461 – Very bright core area with a small halo around it
- NGC 5462 – Large and stretched out in the direction of the spiral arm. Visible as a smooth and even brightening
- NGC 5447 – Just comes loose from NGC 5450 and the brightest of the two. Both are fairly easily visible
- NGC 5455 – Small tuft of cotton and fairly bright. Visible in a triangle with 2 stars on the outer rim of the galaxy
- NGC 5458 – Weak. Can be seen as a faint brightening in the arm with averted vision
- NGC 5453 – Utterly weak brightening in the arm with averted vision
NGC 5451 – This one takes a lot of effort. It’s near a very faint double star which is very distractive. Nonetheless the area seems to blink at me from time to time with averted vision. This one has to remain an uncertain observation…
- NGC 5449 – This one is a no-go, no matter what I try