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deepskytraveler
October 29th, 2019, 04:30 AM
Object of the Week October 27, 2019 - The Pinwheel Treasures
Constellation: Triangulum

H II Regions
A66
RA: 01h 33.8m DEC: +30° 45’
A71
RA: 01h 34.1m DEC: +30° 48’
IC 135, A100
RA: 01h 34.3m DEC: +30° 37’
IC 136, A101
RA: 01h 34.3m DEC: +30° 34’
IC 137, A12
RA: 01h 33.6m DEC: +30° 31’
IC 139, A4
RA: 01h 34.0m DEC: +30° 34’
IC 140, A5
RA: 01h 34.0m DEC: +30° 33’
IC 142, A67
RA: 01h 33.9m DEC: +30° 45’
IC 143, A75
RA: 01h 34.1m DEC: +30° 47’
NGC 588, A27
RA: 01h 32.8m DEC: +30° 39’
NGC 592, A59
RA: 01h 33.0m DEC: +30° 35’
NGC 595, A62
RA: 01h 33.8m DEC: +30° 42’
NGC 604, A84
RA: 01h 34.5m DEC: +30° 47’

Globular Cluster
C39
RA: 01h 34.8m DEC: +30° 22’

Triple Star
NGC 603
RA: 01h 34.8m DEC: +30° 22’



My first telescope many, many years ago was a 6” dobsonian. I fondly recall first light on that scope, shared with David Levy, the well-known comet hunter and astronomy author, at the Hidden Hollow Star Party. That night and the next was absolutely pure magic for me, as I was guided from one deep sky jewel after another in the Autumn sky. I distinctly recall my first three galaxy observations. First was the magnificent Andromeda galaxy (M31). The Andromeda galaxy was clearly visible to my naked eye in the semi-rural skies outside of Mansfield, Ohio. In my scope it was…wow! It seemed to go on forever and I could easily discern brightening toward the core and…double wow…that fuzzy patch to one side I was told was another galaxy called NGC 205. Next up was the Pinwheel Galaxy (M33) in the constellation Triangulum. Unlike the Andromeda Galaxy it was not visible to my naked eye nor in my Telrad (zero-power) finder. So David star-hopped for me to M33. At first, I didn’t see anything in the eyepiece. I looked again and again. Finally with some averted vision and perhaps some creative imagination, I thought I saw some haze. What a contrast between M31 and M33 for a novice observer!

I later learned my experience was far from unusual. Inexperienced observers cite M33 as one of the hardest objects in the Messier catalog. Why is this? Its large size, low surface brightness, and lack of a bright central disk make it a challenging object for small telescopes. The problem is the observer, expecting to see something much smaller and brighter, fails to spot its dim glow which covers an area larger than that of the full Moon. Sky conditions are a critical factor; the least bit of haze can render it invisible. However when viewed near the zenith under clear, dark skies with a large aperture telescope (20” or greater) your first view of M33 may shock you!

This week’s OOTW is not about the Pinwheel Galaxy (M33) - it is about some remarkable deep sky treasures inside the galaxy that are visible under dark, transparent skies with a large aperture telescope at high power.

A pioneering guide to these objects in M33 appeared in Observing Handbook and Catalogue of Deep-Sky Objects by Christian B. Luginbuhl and Brian A. Skiff (Cambridge University Press, 1990). They started the tradition of naming knots within M33 based on a paper published in the November 1980 Astrophysical Journal Supplement Series (http://articles.adsabs.harvard.edu/full/1980ApJS...44..319H) by Roberta M. Humphreys (University of Minnesota) and Allan R. Sandage (Carnegie Observatories). The names consist of the letter A followed by a number.

More than two-dozen individual clusters, stellar associations, and H II regions are visible as distinct objects in amateur-sized scopes, but many do not reveal themselves without effort. And since moderate to high powers are necessary to detect many of the objects, the observing conditions must allow for the higher magnifications required.

The largest and easiest H II region to spot is NGC 604 (A84) which lies near the tip of the galaxy’s main northern arm. A novice observer may mistake it for an unrelated object resembling an elliptical galaxy. OOTW contributor Howard Banich documented NGC 604 in his OOTW for December 6, 2013. Click here (http://www.deepskyforum.com/showthread.php?453-Object-of-the-Week-October-6-2013-NGC-604) to read it.

The following is a list of visible objects within M33 compiled by Sky and Telescope contributing editor, Ted Forte. He observed these from the dark skies outside Sierra Vista, AZ with an 18” telescope at 197x and 262x.


A66 Large, bright patch in the northern arm
A71 Bright spot adjacent to IC 143
C39 Tiny, faint, very challenging; M33’s largest and brightest globular cluster

Conspicuous in their relative isolation, two nebulous stellar associations like to the east of the southern arm. IC 135 and IC 136 glow with the combined light of their component stars and surrounding gas. Both are a little elongated and nearly resolvable.

IC 135 (A100) Bright, elongated, isolated knot
IC 136 (A101) Larger, elongated, mottled knot


IC 137 (A12) Large, formless glow in the southern spiral arm
IC 139 (A4) Together with IC 140, bright knot in the combined glow
IC 140 (A5) Together with IC 139, bright knot in the combined glow
IC 142 (A67) Stellar knot in the northern arm
IC 143 (A75) Elongated know in the northern arm
NGC 588 (A27) Round, less obvious than other NGC knots. On the outskirts of the southern arm. Larger than NGC 592 but fainter. Appears round.
NGC 592 (A59) Smallish, but easy to spot. Smaller and more star-like, it is easier to spot, lying in a blank area west of the core and inside the curve of the southern spiral arm.
NGC 595 (A62) Large and bright oval masked by nearby core. Brightest and largest H II region after NGC 604. May be overlooked because it lies just 4’ northwest of the galaxy’s core.
NGC 603 Triple star that Lord Rosse noted as a nebulous object, lies 28’ southeast of M33’s core

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So much for my nearly invisible galaxy. I can’t wait for my next dark sky outing to give these objects a try with my 15” scope.

Now it is your turn.
Give it a go and let us know!

Steve Gottlieb
October 29th, 2019, 06:17 AM
For another resource, I have a page (https://www.astronomy-mall.com/Adventures.In.Deep.Space/M33.HII-Star.Clouds.html) on Adventures in Deep Space dedicated to HII regions and stellar associations in M33 with a labeled photographic chart and visual descriptions with my 18", as well as a dowloadable spreadsheet. A number of additional objects are included.

Clear Skies
October 29th, 2019, 09:43 AM
Observations of the NGC and IC objects in M33.

22 September 2014, southern France, SQM 21.25, 12" SCT @ 179x/27'

NGC588
Slightly elongated north to south, even in brightness, no change when using AV. Fainter and just a bit smaller than NGC692 that is 1/4 FoV to the east.

NGC592
Is to the west of the galaxy, on the western edge of the outer glow. A slightly north to south elongated patch with a stellar point on the southeastern edge that resembles a mag. 14.5 star.
1/4 FoV to the west is NGC588, 1/4 FoV to the NE is NGC595.

IC131
Very faint, a very small patch, almost stellar.
To the NW is a mag. 15 star, one and half times that distance towards the NW is mag. 13 star with a mag. 12 star to its north. To the SSW is NGC595, almost 1/2 FoV to the north is IC133.

IC133
Quite large (relatively), almost twice the size of NGC588 and NGC592. A north-south elongate glow, even in brightness when not using AV, using AV a bright point is on the southern edge, resembles a mag. 15 star (can only be held with use of AV).
To the north is a mag. 14 star with two mag. 13.5 to its north, aligned SE to NW. To the NNE of the two mag. 13.5 stars is IC 132. Almost 1/2 FoV to the south is IC131.

IC132
A small, faint, round patch, a faint glow.
To the SSW are two mag. 13.5 star aligned SE to NW. To the south is IC133.

NGC595
A faint, round glow, a small patch that is directly NW of the nucleus of the galaxy. Just a bit smaller than NGC592 that is 1/4 FoV to the SW.
To the NE is a mag. 14.5 star. to the NNE is IC131. On the NW side of the nucleus of the galaxy are two mag. 14 star aligned NW to SW.

IC137
A quite large, NE-SW elongated glow to the SSW of the nucleus of the galaxy.
To the ENE is IC140.

IC140
A north-south elongated part of the galaxy, half the size of IC137 to the WSW.
To the NNE is IC139.

IC139
Larger and less clear than IC140 to the SSW, IC139 is more round, not very detached from the galaxy.
From the nucleus of the galaxy a curving section is visible towards the south, curving towards the SE. That section widens (IC139) with the elongated star cloud IC140 to its SSW.
To the ESE is IC136.

IC136
A round glow, quite faint and not very detached. To the SE is a mag. 11.5 star. Fainter than most of the HII regions in the galaxy.
To the north is IC135.

IC135
Only visible when using AV and on the limit of visibility, elongated north to south, very faint, faint than IC136 to the south.
1/3 FoV to the NNE is NGC604.

IC142
A small and pretty faint, NE-SW elongated glow. In the SE corner of a slightly flattened triangle pointing towards the SE with the base on the NW side aligned NE (mag. 13 star) to SW (mag. 12 star). Directly SE of the mag. 12 star is a mag. 14 star.
To the ENE is IC143.

IC143
A very faint, slightly east to west elongated glow, only clear when using AV. Directly ESE is a mag. 13.5-14 star.
To the WSW is IC142, just a bit farther to the east is NGC604.

NGC604
The brightest HII region in the galaxy, on the edge of the halo of the galaxy. Slightly elongated WNW to ESE with a stellar point directly WSW of the center. To the SE is a mag. 11 star, to the SSW is a mag 13.5 star.

Screenshots below from CSOG (the upcoming V2.3 edition), click here (https://www.dropbox.com/s/gud6q5lp2lvqs0d/Tri%20-%20M33%20%5B12-14%5D.pdf?dl=1) to download in PDF.

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lamperti
October 29th, 2019, 04:30 PM
With a 20" f5, 272xfrom 2004 & 2006:
U-49: Globular cluster: Averted vision, scale #1. Was able to hold this tiny globular briefly.
C-39: Found the globular using my own Megastar sheet first and confirmed with photo which was easy once oriented correctly.
IC-143: It is seen as a small glow.
IC-142: Seen as a thin narrow strip.
IC-131: Appears small but it is adjacent to a triangle of three stars.
IC-132: Faint and small
IC-133: Faint and small
IC-137: t is not split from IC-139 and IC-140. It looks homogeneous and part of the arm of M-33 rather than a distinct member.
IC-135: Fairly bright
IC-136: It is more stellar with a star adjacent to it.

Bertrand Laville
October 30th, 2019, 02:33 PM
Hi All,

Two years ago, I could manage a very deep study of this galaxy, during several following nights, with my 25" Obsession, and under good sky (NELM +/-7.0v at zenith, SQML 21.56).
The result was that I could point at 17 GC's, 34 Hii regions, and 83 associations!
Here is a very long report: http://www.deepsky-drawings.com/m-033/dsdlang/fr
And the drawings here under.

Clear skies
Bertrand
http://www.deepsky-drawings.com

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Uwe Glahn
October 30th, 2019, 08:51 PM
M 33 is for real a huge object which showing lots of detail up from very small apertures. Impossible to find and add all individual observations but I try to show some highlights.

Starting with 4-inch I was shocked several years ago when I was looking at the galaxy. It showed many HII regions and the inner plus outer arms.
sketch: 4", 63x, NELM 6m5+
3687

With the 16-inch (450x, NELM 6m5+) I tried some globular clusters after Mochejska et.al. [1998AcA....48..455M]:
- 40 = U49 (15,89) - brightest GC; difficult, popping in and out of view with averted vision, safe observation
- 21 (16,04) - difficult but safe observation
- 27 (16,05) - difficult but safe observation
- 43 (16,52) - very hard to detect but again safe observation
- 47 - not visible
Parallel I tried the brighter Cepheid VHK83. I noted: very difficult but popping in and out of view several times at the exact position, safe observation

Later I tried to resolve the brightest HII regions with the 27-inch.

sketch NGC 588: 27", 837x, Seeing II-III, NELM 7m0+
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sketch NGC 592: 27", 837x-977x, Seeing II, NELM 7m0+
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sketch NGC 595: 27", 837x-977x, Seeing II, NELM 7m0+
3690

sketch NGC 604: 27", 837x, Seeing I, NELM 7m0+
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Dragan
October 30th, 2019, 09:26 PM
Great post Mark!

And the wealth of information being provided in members' responses is wonderful! Keep them coming!

skyraider
November 1st, 2019, 11:32 PM
WOW!! This thread is amazing! I'm pumped to pick this galaxy apart. This is a compliment to this website. Truly a wealth of observing knowledge coalesced into one convenient spot. Nicely done...

kisspeter
November 4th, 2019, 11:47 AM
I can contribute a drawing from 2015-16. This is a panorama: a good dozen star positions drawn from a map (Guide), then 1 night 4" and 6 nights 16" observations (71x-220x).
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C39 was difficult but surely visible (16", 220x).
I have 2 ready detail drawings:
NGC 604 (16", 220x-294x):
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IC 139-140 (16", 220x-294x):
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I also have a ready sketch of NGC 592 from 2018 but it's not yet processed into a final drawing. It's also a nice star forming region with many details in the 16" scope.

Howard B
November 10th, 2019, 05:03 AM
Here's a drawing from several years ago of what I've seen of M33 through my 28-inch:

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And a sketch of NGC 604:

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I have a bunch of sketches of the other NGC and IC objects that are a part of M33, as well as a bunch of star associations - but given the profuse amount of sketches above this is probably enough!