Cosmic Challenge: Dissecting M101
Posted 01 July 2018 - 05:30 AM
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- Lewis Cason, okiestarman56 and cookjaiii like this
Posted 03 July 2018 - 09:38 PM
But with time and patience, M101 is visible, with difficulty, through 50-mm binoculars even given a suburban sky with a naked-eye limiting magnitude of perhaps 4.5.
Hi, Phil! What Bortle number would you estimate those kinds of skies at? I live in the city under hard Bortle 9 skies, but reach limiting magnitudes of ~5.0-5.5.
I set up my 15x70 binoculars + parallelogram mount last night to search for M101, but got no convincing hints. I was able to barely, with effort, see M51, and in a brief moment of clarity saw a mag 11.5 star pop a time or two. The transparency was not the best, but good for summer (I live in Houston so there's tons of gulf moisture). The skyglow was bright enough that I was able to see plainly into the deepest shadows under the trees 50' away, and the sky was the color of a planetary nebula overhead and in the direction of Ursa Major, simultaneously blue and green. Towards the horizon or my many light domes it turned tan. I will keep trying for M101 under hopefully better conditions.
- Augustus likes this
Posted 04 July 2018 - 09:32 PM
I’m sure under pristine unpolluted skies that M101 is visible with instruments under 100mm. I was checking my observer’s log from last year around this time and viewed the sketch with my 8” at about 70x. It was a barely discernible irregular grey patch only marginally lighter than the background. More magnification did not produce meaningful detail and certainly nothing like the structure Phil sketched with his 18”. I live in a Bortle 5 zone and took an SQM reading of the area which yielded a reading of 20.35. I typically have good-excellent transparency.
- Tyson M and TieDyeAstronomer like this
Posted 05 July 2018 - 07:48 PM
Hey Chesterguy1! Thanks for sharing your report!
I’m sure under pristine unpolluted skies that M101 is visible with instruments under 100mm.
Definitely! I've been able to see it quite "easily" (for a deep sky object) in my 15x70 binoculars from a Bortle 3-4 site, and one where the big light dome is to the North too, so not the best for M101. But having such a low surface brightness, it sure does get wiped out fast. I bet it would be a bigger struggle from my club's Bortle 4.5 dark site.
Posted 06 July 2018 - 07:58 AM
For me, it's always a better target this time of year: high in the sky, more north/northwest and away from the small light dome of my city, which for me is NE. It's still a tough target and even with my 15" it reveals little structural detail from my admittedly suburban zone. It is, of course, much easier to find with the 15" (although I would never classify it as easy from my locale). What I can see readily--but is more elusive in the 8" are the nearby NGC galaxies, 5473 and 5474. I cannot see 5477. Thus, the galaxies Phil sees within the structure of M101 are simply not possible unless I go to a much darker site.
- PhilH likes this
Posted 07 July 2018 - 02:27 PM
I can sweep up M101 fairly easily with my Celestron 8x42s from a really good dark site.
Posted 07 July 2018 - 02:32 PM
M101 and its HII regions can be quite spectacular through a large aperture from a pristine site.
Here's an image that I captured years ago using the BRT.
M101 (The Pinwheel Galaxy)
14" f/11 Celestron C14 SCT working at f/5.3
FLI MicroLine CCD camera
Bradford Robotic Telescope
Tenerife, the Canary Islands
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Posted 28 July 2018 - 03:02 PM
of 8,000 feet on the North Rim of the Grand canyon during new
moon in June. I observed it through a 20" f/4.5 reflector owned by
Steve Dodder of the Saguaro Astronomy Club, who host a week
long star party at the North Rim each year as an outreach event
in conjunction with the North Rim Lodge and the Park Service.
Through the 20-inch using a 14mm 82 degree eyepiece (150X)
M-101 looked exactly like Dave Mitsky's astrophoto, above.
ALL of the H-II and star-forming knots in the spiral arms
were clearly visible. With averted vision, even the faintest
knots shown in Dave's photo were visible. This was the finest
view of M-101 I have ever had, and will remain one of my
greatest moments at the eyepiece of a telescope. The skies
at 8,000 feet were incredibly dark, with so many stars that the\
constellations were hard to pick out! M-101 was AWESOME!!
- Dave Mitsky and PhilH like this
Posted 30 July 2018 - 10:01 PM
I never knew these NGC regions existed inside M101. I just discovered the pinwheel spiral arm structure for the first time this year with my 8" dob from a dark site. I know now to bump up the magnification for closer scrutiny!
Also I found this galaxy easy to sweep up with the 10 x 50 binos from my dark site.
Thanks for the article
- PhilH likes this