M 101 (NGC 5457, Arp 26) Galaxy in Ursa Major
Located at: RA 14 hours 03 minutes 13 seconds, Dec +54 degrees 20 minutes 55 seconds
Size: 28.9' x 26.9' Magnitude: 8.3 blue Class: SAB(rs)cd HII
North is up
West to the right
8" f5 Newtonian reflector
ST-8XME, self-guided, binned 1x1, temp -25c, camera control MaxIm DL 4.56
Lumicon Red filter, 710 minutes (71 x 10 minute subs), 04/11/12/14/15/2009; seeing 2.6-4.6 FWHM per CCDStack
CCDStack 220.127.116.11, Photoshop 7.0
Rolling Roof Observatory, Thousand Oaks, CA 91360 (+34d 13m 29s -118h 52m 20s)
This image replaces a 360 minute red
filtered image from 05/13/14/2007. I tried doubling the exposure
with the new Lumicon red filter, but difference was only marginally more
successful. This image is smoother, and processed more realistically,
than my previous image. However, the doubling of the exposure time only
increased the difficulty of dealing with the gradients. Need a real
narrow band filter to significantly increase the contrast/details (i.e., 'pop'
the HII regions).
My charting software (Megastar v5.0.13) lists three NGC "knot in Galaxy" designations for brighter areas along M 101's arms, along with NGC 5477 (1.8'x1.3', 14.0v mag, Cl:SA(s)m), the small dim galaxy to the northeast (upper left), and NGC 5471 (0.7'x0.6', -- mag, Cl:-- [NGC / IC Projects identifies this as an HII region]) the small, bright, non-stellar lump midway between M 101's nucleus and NGC 5477. However, the NGC / IC Project lists six other knots with NGC numbers ... There is a lot going on in and around M 101 ...
See the 14.5" version.
From the NGC / IC Project:Contemporary Visual Observation(s) for NGC 5457
NGC 5457 = M101 = U08981 = MCG +09-23-028 = CGCG 272-021 = Arp 26 = VV 344 = VV 456 = Pinwheel Galaxy = PGC 50063 14 03 12.4 +54 20 55 V = 7.9; Size 28.8x26.9; SB = 14.9 13.1": fairly bright, very large, round, about 20' diameter, bright core. Fairly low surface brightness but beautifully resolved into several distinct arms and sections of arms with a pinwheel design. Obvious mottling along the spiral arms which appear clumpy with at least four HII regions resolved including N5447, N5458, N5461, N5462. At least six stars are superimposed. - by Steve GottliebHistorical Research Notes / Correction for NGC 5457
NGC 5457 = Messier 101, and is also Messier 102. The identification with M102 has been controversial, however, and rests on a letter that Mechain (who discovered M101) wrote to Bernoulli, then the editor of the Berliner Jahrbuch, claiming that the object is nothing more than a reobservation of M101. This letter was republished in 1947 by Helen Sawyer Hogg, and is usually taken as proof of the identity. Here is the relevant paragraph extracted from Mechain's letter, first in the original German as published in the Jahrbuch, then in Hogg's English translation: "Seite 267 der Connoissance des tems f. 1784 zeigt Herr Messier unter No. 102 einen Nebelfleck an, den ich zwischen [omicron] Bootes und [iota] Drachen entdeckt habe; dies is aber ein Fehler. Diest Nebel fleck ist mit dem vorhergehenden No. 101 ein und derselbe. Herr Messier hat durch einen Fehler in den Himmelscharten veranlasst, denselben nach dem ihm mitgeheilten Verseichnisse meiner Nebelsterne verwechselt." "On page 267 of the Connaissance des temps for 1784 M. Messier lists under No. 102 a nebula which I have discovered between [omicron] Bootes and [iota] Draconis; this is, however, an error. This nebula is one and the same as the preceding No. 101. M. Messier confused the same as the result of an error in the sky chart, in the list of my nebulous stars communicated to him." (I am grateful to Ashraf Shaker -- at the time he sent it in the mid-1980's -- a student at the Helwan Institute in Egypt, for sending a copy of Hogg's paper "Catalogues of Nebulous Objects in the Eighteenth Century" published in the "Journal" of the Royal Astronomical Society of Canada, Vol. 41, pp. 265-273, 1947; and reprinted in the "Communications" from the David Dunlop Observatory, Vol. 1, No. 14. The paper is now -- June 2006 -- available at ADS; the URL is "http://adsabs.harvard.edu/cgi-bin/bib_query?1947JRASC..41..265S".) However, some observers are still trying to make the case that M102 is actually NGC 5866 (which see). The evidence points almost unequivocally to NGC 5457, but there is some marginal evidence for NGC 5866. Occam's Razor, however, points to a simple mistake on Messier's part. Steve O'Meara's "Eye on the Sky" column in the March 2005 issue of "Sky and Telescope" has the full story. There Steve gives his own translation of Mechain's letter, and points out that Messier probably mistakenly plotted M102 east of theta Bootis instead of west, leading to the erroneous description published in the 1781 list. If so, this is far from the only case of an observer confusing directions from a comparison star. - Dr. Harold G. Corwin, Jr.
** I list observations for only the three knots (and one galaxy?) my software identified ... for the others, see NGC / IC Project ...Contemporary Visual Observation(s) for NGC 5447**
NGC 5447 14 02 27.9 +54 16 34 18" (6/21/03): at 215x this fairly prominent HII region appeared as an elongated patch oriented NNW-SSE, perhaps 25"x8", located just south of a mag 13.5 star. At 323x this patch clearly resolved into two sections -- within 30" of the star is a very compact knot, ~6"-10" diameter. There may be a small gap to the south with a larger extension to the SSE (this is N5450). Located on the opposite side of M101 as N5462. 17.5" (6/7/97): brightest HII region on the preceding side of M101 located 7.8' SW of center. Appears as a very elongated glow NW-SE situated just south of a mag 13.5 star. A very small knot is partially resolved at the N edge within a common halo with the extension to the SE. Harold Corwin identifies these two components as N5447 and N5450. 13": this is a knot in an outer arm of M101 on the western side. Easily visible, compact, round. Located symmetrically opposite from N5462 on the opposite side of the core. - by Steve GottliebHistorical Research Notes / Correction for NGC 5447/5461/5462/5471
NGC 5447, 5449, 5450, 5451, 5453, 5455, 5458, 5461, 5462, and NGC 5471 are HII regions and/or star clouds in M 101/M 102. Most were discovered by LdR, though WH found three of the brightest, and d'Arrest noticed the outlier, N5471. Unfortunately, only the identifications of WH's and d'A's objects are unambiguous. The positions of the others turn out to have been determined by JH for GC. He used the sketch of M101 that appeared in LdR's 1861 paper to estimate offsets from stars with known positions. This must have been a hurried chore, since his resulting positions for the knots are not very good. Without additional observations, Dreyer simply adopted JH's GC positions. There has thus been some confusion over the identifications of the objects found by LdR. Only in two cases, N5461 and N5462 (both found by WH), did LdR provide offsets from a nearby star. D'A's object, N5471, not only has a good position, but is isolated enough from the main body of the galaxy that its identification is also certain. To identify the other objects, I have gone back to the published 1861 sketch where they are clearly shown. I have easily identified the knots which JH saw in the same sketch. With those identifications in hand, I remeasured the positions, and have also been able to sort out most of the identifications used in earlier papers on M101. The correct identifications and new positions are in the main Table. - Dr. Harold G. Corwin, Jr.Contemporary Visual Observation(s) for NGC 5461**
NGC 5461 14 03 40.9 +54 19 02 18" (6/28/03): at 435x (5.2mm Pentax) a fairly bright quasi-stellar knot is attached at the NE end with a relatively faint extension (even surface brightness) extending to the SW. 18" (6/21/03): at 215x, this prominent HII region has a high surface brightness and stands out well. Increasing the power to 435x, there is a stellar or quasi- stellar core offset at the NE end with a faint extension to the SW. Backing down to 323x and using a UHC filter, the glow decreases in size, but the star- like core seems to increase slightly in contrast. 17.5" (6/7/97): fairly faint knot in the trailing arm of M101 4.5' SE of center. Appears slightly elongated, ~25"x15", fairly high surface brightness. Contains a very small brighter center or a star is superimposed. 13": this is a knot in M101 located in the spiral arm which trails to the E. Appears as a very diffuse, fairly small knot. - by Steve GottliebContemporary Visual Observation(s) for NGC 5462**
NGC 5462 14 03 52.9 +54 21 53 18" (6/28/03): this HII region is probably the largest continuous piece. It appears very elongated 3:1 or 7:2 SW-NE, roughly 60"x18". 18" (6/21/03): fairly bright and relatively large, elongated 3:1, ~50"x17" SW- NE. This HII region has an irregular surface brightness with a bright, nearly stellar knot at the NE end. 17.5" (6/7/97): moderately bright elongated knot in M101, extended 3:1 SW-NE, ~50"x20". One of the largest and brightest HII regions in M101. 13": knot in M101 located in the same arm as N5461 but further to the E. This is an easily visible, compact, round knot on the opposite side of the core as N5447. - by Steve GottliebContemporary Visual Observation(s) for NGC 5471**
NGC 5471 = MCG +09-23-030 14 04 29.1 +54 23 49 Size 0.9x0.7 18" (6/28/03): highest surface brightness of any of the HII regions in M101. Appears very similar to a small, elliptical galaxy -- even contains a small, brighter core. Situated beyond the main glow of the galaxy, 11.5' NE of the core of M101. 18" (6/21/03): at 323x appears similar to a compact, round galaxy. Furthest NE of all the HII regions and well separated from the main glow of M101. Interestingly, this was one of the few HII regions that did show a positive contrast response to a UHC filter at 161x and 215x. 17.5" (6/7/97): this is one of brightest HII regions in M101, on the extreme NE end of the galaxy 11.5' from center. Appears as a moderately bright knot, ~20" diameter. This HII region stands out well due to its isolation and fairly high surface brightness with crisp halo. Incorrectly identified as a galaxy in MCG. - by Steve GottliebContemporary Visual Observation(s) for NGC 5477
NGC 5477 = UGC 09018 = MCG +09-23-034 = CGCG 272-025 = VV 561 = PGC 50262 14 05 32.3 +54 27 33 V = 14.0; Size 1.7x1.3; SB = 14.7; PA = 95d 17.5": extremely faint. Nearby is a mag 14.5 star 1.2' SW of center and a mag 15 star is superimposed south of the core. A brighter mag 12 star is 3.5' E of center. Member of the M101 group. - by Steve Gottlieb