Telescope:

 8" f5 Newtonian reflector

Camera:

  ST-8XME, self-guided, binned 1x1, temp -20c, camera control MaxIm DL 4.56

Image:

Lumicon Red filter, 650 minutes (65 x 10 minute subs), 01/16/17/18/2009; seeing 2.5-3.7 FWHM per CCDStack

Processing:

CCDStack 1.4.1, Photoshop 7.0

Location:

 Rolling Roof Observatory, Thousand Oaks, CA 91360 (+34d 13m 29s -118h 52m 20s)

Notes:

This image replaces an unfiltered 91.5 minute Track & Accumulate image from 12/24/2005.

From the NGC / IC Project:

Contemporary Visual Observation(s) for NGC 598

NGC 0598 = M33 = U01117 = MCG +05-04-069 = CGCG 502-110 = Triangulum galaxy = 
PGC 05818
01 33 50.9 +30 39 37
V = 5.7;  Size 70.8x41.7;  SB = 14.2;  PA = 23d

17.5": bright, very large, elongated 3:2 SSW-NNE, weakly concentrated irregular 
halo, rises suddenly to a small bright core.  Two prominent spiral arms form an 
"S-pattern" with an irregular surface brightness.  At least a dozen HII regions 
or clusters are resolved (see the numerous IC listings).  Overall, the entire 
galaxy is very mottled and the outer extent is difficult to define.  Naked-eye 
threshold 25% of time in very dark skies.

- by Steve Gottlieb

There are 4 separate NGC objects plotted across the face of M 33 ... here is the observation for the most prominent ...

NGC 0604 = A84
01 34 31.9 +30 47 13

13.1": bright HII region located 12' NE of the core of M33.  Situated at the end 
of the large spiral arm of M33 which extends N and then E of the core.  Bright, 
fairly small, ~30" diameter, round.

8": fairly bright, round, knot in M33.

- by Steve Gottlieb

Historical Research Notes / Correction for NGC 598

The IC Objects associated with NGC 598 (M 33)
Listed below, is the paper chase associated with IC 135, IC 136, IC 137, IC
139, and IC 140. The  associated positions for each of these objects is due in
large part to the original work of French  astronomer Guillaume Bigourdan
(1851-1932).

He verified the positions of 6380 nebulae between 1884 and  1911 with Paris
Observatory's 12inch refractor (F/17.2) and discovered about 500 new objects
while doing  so ("Observations de nébuleuses et d'amas stellaires",
Gauthier-Villars, 1912). J. L. E. Dreyer credits  77 objects in the NGC to
Bigourdan. His original purpose (which now may seem fruitless) was to obtain
the  base for future nebulae proper motion surveys.

Bigourdan made meticulous micrometric measurements of many of the positions
of NGC (and IC) objects referenced  against a nearby, easily identifiable 
field star.  For all of the IC Objects of interest, but one, Dr. Harold Corwin
has the following note:

"IC 135, IC 136, IC 139, and IC 140.  These are all HII regions or star
clouds in M33.  There is a (typographical?) error in Bigourdan's estimated 
offset from M33's nucleus of his comparison star for these four.  He claims 
that the 10th magnitude comparison star is 8' south, and 31 seconds of time 
preceding the nucleus.  There is no star that bright in that position.  However,
there is a star of the right brightness 31 seconds of time following the nucleus.
When Bigourdan's measured offsets for his four novae are referred to this
star, the four objects can be pretty easily identified (but see IC 139!)."

For IC 139, Dr. Corwin notes:

"IC 139.  The identity is not quite certain.  I measured the position of a
star cloud that I thought was IC 139, but this turned out to be half an arcminute
north of Bigourdan's micrometric position.  Checking the field, however, I
found that his position is very clearly on a foreground star embedded in a
confused area of fainter stars.  His description is telling, too, as he
refers to a nebula about 30 arcsec across with a brighter central point that he
measured.  It seems likely that the combination of the star and the
background light of M33 led him to think he had found a nebula."

Dr. Corwin started with Bigourdan's micrometric positions, and then, using
the POSS plates, determined  the positions for each of the IC objects in
question based upon Bigourdan's chosen reference star.  In  Dr. Corwin's own 
words:

"My own measurements with an engineering scale, astrometrically reduced,
generally on the POSS prints,  sometimes from the IIIa-J SSS  films. Standard
deviation about 5 arcsec."

Dr. Corwin's positions are available on this web site, and are in
B1950 Equinox.  Shown below  are Dr. Corwin's B1950 positions along with my
precession of those positions to J2000 Equinox.

              Dr. Corwin's B1950                  Dr. Corwin's B1950
              measured positions                  Precessed to J2000
         -----------------------------       -----------------------------
IC 135   01h 31m 26.3s    +30° 21' 49"       01h 34m 15.5s    +30° 37' 10"
IC 136   01h 31m 26.7s    +30° 18' 19"       01h 34m 15.9s    +30° 33' 40"
IC 137   01h 30m 49.8s    +30° 15' 59"       01h 33m 38.9s    +30° 31' 21"
IC 139   01h 31m 10.2s    +30° 19' 10"       01h 33m 59.3s    +30° 34' 32"
IC 140   01h 31m 09.0s    +30° 17' 39"       01h 33m 58.1s    +30° 33' 01"

Bigourdan's original positions (micrometrically measured offsets from his
reference star) were converted  to B1950 positions by Dr. Corwin, who states that:

"G. Bigourdan, visual micrometric measurements (1884 - 1907) reduced by me
w.r.t. SAO, AGK3, GSC, or AC  positions, taking proper motion into account when
possible.  Standard deviation varies, usually about 2  arcsec, but is larger for 
objects with poorly-defined or faint nuclei."

          Bigourdan's original positions
          reduced to B1950 by Dr. Corwin
          ------------------------------
IC 135    01h 31m 26.5s    +30° 21' 53"
IC 136    01h 31m 26.6s    +30° 18' 18"
IC 137    01h 30m 49.8s    +30° 16' 01"
IC 139    01h 31m 10.3s    +30° 18' 43"
IC 140    01h 31m 09.0s    +30° 17' 45"

 - Robert E. Erdmann, Jr.