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HII region in M33 ?

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#1 nytecam

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Posted 12 November 2013 - 10:26 AM

Although a comparable distance to M31 - the elusive face-on M33 presents some interesting HII regions for the amateur to attempt. The brightest [mag 14?] and most interesting is NGC 604. It's located 14'-arc Nf the galactic core and was discovered by William Herschel in 1784 using his speculum mirror which was no match in light grasp for modern scopes.

NGC 604 has some impressive statistics unequaled in our Local Group of Galaxies eg x40 the size of the Orion Nebula and X6000 brighter ! Some lesser HII regions are also marked on my image below taken last month using this reference. I'd be interested in your obs of NGC 604 etc :rainbow:

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#2 Astrojensen

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Posted 12 November 2013 - 10:49 AM

NGC 604 is nowhere near as faint as mag 14, more like mag 10! I see it almost every time I look at M33 with my 63mm Zeiss, unless the conditions are horrible. I've seen it well in my 50mm Zeiss, too.

In my 12", it's very bright. It has, after all, the same (or higher!) surface brightness as the Orion Nebula! I've also seen several other spots in the spiral arms with the 12", but didn't have a map with me at the scope, so they remain unidentified so far. I consider it highly likely that I've seen at least NGC 595, NGC 592 and IC 142, but I am not 100% sure.


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#3 aatt

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Posted 12 November 2013 - 10:55 AM

I think I have seen NGC 604, 595,592 and IC 139 or 140 (probably thought of the IC's as one object) as I too was going from memory only.

#4 nytecam

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Posted 12 November 2013 - 11:01 AM

Thanks AATT for your obs :bow:

NGC 604 is nowhere near as faint as mag 14, more like mag 10! Thomas, Denmark

Thanks Thomas - I used a Wikisky reference to its mag but added the "?" as I thought the figure was dubious :p

#5 galaxyman

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Posted 12 November 2013 - 11:37 AM

I talk about observing it in this month's Galaxy Log video using a 4" refractor. http://www.youtube.c...h?v=qmf_ITlQFd0

In larger scopes from my 8" refractor to the 22" dob, M-33 becomes one of the great objects in the northern sky. Many star clouds and HII regions are seen throughout the galaxy.


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#6 kt4hx

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Posted 12 November 2013 - 11:39 AM

Thanks for the annotated image - that really helps. The only listed magnitudes I could find for NGC 604 were 12th. I'm glad Thomas mentioned the surface brightness comparison with M42. I read on one site that if NGC 604 were at the same distance from us as M42, it would cover an area about the size of your hand with your arm extended, and have an apparent magnitude similar to Venus. It also said that NGC 604 was second only in size to the Tarantula Nebula in the LMC, when it comes to emission nebulae in the Local Group.

#7 IVM

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Posted 12 November 2013 - 05:06 PM

I observed NGC 604 around this time of the year in 2010 with my 12" solid-tube Newtonian (Orion XT Classic) and in 2011 with my 12" SCT (LX200GPS). My notes describe it as "bright, threatening my dark adaptation" and "round, approximately the same size as the other three NGC regions". One of these is NGC 588 that is just beyond the right edge of your frame. I viewed NGC 604 again just last month but that night I concentrated on the other side of the galaxy and did not record anything about NGC 604.

EDIT: P.S. It is interesting how faint the individual HII region BCLMP 710 on the WSW edge of the IC 136 complex is in your photo. It really stands out in some other photos (e.g. on Wikisky) and visually.

#8 hbanich

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Posted 12 November 2013 - 07:10 PM

The best finder chart I’ve found for M33 is on Steve Gottlieb’s page at http://tinyurl.com/m4mrmy2 . He includes visual descriptions of all the marked objects too, and this was an indispensable resource for finding my way around because so many low contrast features can be seen here in a big scope. It was my main reference while making my M33 drawing.

I’ve attached my full drawing, and note that the central portion of it accompanies Ted Forte’s excellent observing article in the December issue of Sky & Telescope. There’s about 8 hours of observation time into that drawing, spread out over four long years – unfortunately M33 gets high enough to observe just as the rainy season begins here in Oregon. Even so, I sure didn’t plan on it taking this long!

Anyway, I include the full drawing here and you can see NGC 604 near the top left, and I’ve included a close up as well. I’ve used up to 1200x on 604 when the seeing was steady enough, and see its main structure as two overlapping triangles studded with faint star-like points. I think these are some of the huge star clusters within 604 rather than individual stars, but I really don’t know. I’ve been trying to see the loop shown so well in the HST image but so far have come up empty. Jimi Lowrey has seen it with his 48” in Texas though, and someday I hope to be able to see it as well.

The size of 604 is so vast that it’s actually wider along its longest dimension (~1500 light years) than the distance between the Earth and the Orion Nebula (~1344 light years). Imagine, if M42 could magically trade places with 604, it would be a minor and probably overlooked HII region. And we’d be inside 604! Location, location, location.

NGC’s 595, 592 and 588 are all worth close inspection when the seeing is steady, but they don’t offer anywhere near the detail that 604 has. Another interesting observation is NGC 603, which although is a close a triple star really does appear embedded in nebulosity the few times I’ve seen it.

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#9 hbanich

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Posted 12 November 2013 - 07:11 PM

...and NGC 604 close up -

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#10 Sasa

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Posted 13 November 2013 - 03:36 AM

Howard, amazing drawing of M33! What kind of telescope you were using?

I was able to see NGC604 from my small town backyard. In 63mm and 80mm it was almost stellar without too much of detail. It became more alive in 130mm refractor, here I could noticed some elongation and mottling.

#11 hbanich

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Posted 13 November 2013 - 12:17 PM

Hi Sasa,

Thank you! I used my 28 inch f4 Newtonian to make the M33 and NGC 604 sketches, using magnifications from 100x to 1200x.

#12 Feidb

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Posted 13 November 2013 - 09:28 PM

I've logged 11 of the 14 or so IC/NGC objects within the galaxy. The three I missed, I probably saw but didn't have them marked on my map so wasn't looking for them. Next time... Haven't tried for any of the C globulars, if there are any, which if it's like M-31, there are probably quite a few. My star maps don't list them anyway.

#13 hbanich

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Posted 14 November 2013 - 04:42 PM

I found a list of M33 globular in a paper located here: http://cds.cern.ch/r...les/9806222.pdf
Scroll almost to the end of the paper and on page 25 you'll find a list. Unfortunately it doesn't include detailed chart showing where they are in M33 but it does include the coordinates and magnitudes.

This is a helpful page too: http://fdsa-blog.blo...triangulum.html

#14 nytecam

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Posted 17 November 2013 - 04:45 AM

Despite nearby full moon - here's a close-up of the massive HII region NGC 604 in zoomed crop top right from last Thursday :rainbow:

#15 IVM

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Posted 17 November 2013 - 10:44 AM

Interesting how the graininess in this photo traces the outer arm quite nicely.






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