Mark9473
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Reged: 07/21/05
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Loc: 51°N 4°E
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Here's something nice that I've been looking at the past few evenings with my 15x60.
I suspect one road in the stars that many of us have travelled along - and if not, you should - is from alpha to beta CAS, then at beta take a 90° right turn to get to the formidable open cluster NGC 7789.
Next time, after you've looked at NGC 7789, start over but at beta CAS take a 45° left turn. You then hit a pretty rich star field with a sprinkling of stars of 5th to 7th magnitude, and nested among them the open cluster NGC 7790 (and a few smaller/fainter ones as well).
What I found so interesting here, is that from the region of NGC 7790, starts a "path" of 9th and 10th magnitude stars that curves away and upward like a big inverted S, somewhat slanted, and miraculously brings you to the doorstep of M52 which I otherwise find notoriously hard to locate.
I suspect that the visibility of this pathway depends among other things on the limiting magnitude your sky and instrument allow, so I'd be interested in your impressions.
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63; Docter 15x60
WO Megrez II 80 FD + Baader 90° T2 Amici
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GlennLeDrew
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Reged: 06/18/08
Posts: 1304
Loc: Ottawa, Ontario, Canada
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....which I otherwise find notoriously hard to locate.
That's one reason why I like huge fields of view; panning from one target to another is made so much easier. For example, even at 21X, my 4.7 degree field keeps me from wandering too far off the track when panning even more than 15 degrees when the general direction is known.
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Home-made Mk II RA bino, using interchangeable objectives and eyepieces
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RichD
professor emeritus
Reged: 11/08/07
Posts: 567
Loc: Derbyshire, UK
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Interesting, i've never found M52 difficult to locate, I just draw an imaginary line extending from alpha to beta then extend it out the same length again beyond beta. I'll look for the path you describe next time. I've never really lingered on 7790 for long so i'll check it out more thoroughly.
This is one of my all time favourite areas to sweep with binos!
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Clear skies
Rich
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BobinKy
Carpal Tunnel
Reged: 04/27/07
Posts: 1683
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Mark...
Thanks for the report and the tip on the inverted S path to M52.
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Bob
38°N
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EdZ
Professor EdZ
Reged: 02/15/02
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Loc: Cumberland, R I , USA42N71.4W
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7790 is quite a difficult object. Consider that it is about 5 times fainter than 7789 and about 10 times less sparse in population and appears only 20% the diameter of 7789, and in comparison you are looking for a speck rather than a faint diffuse spot like 7789. I seldom see this cluster with binoculars.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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Mark9473
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Reged: 07/21/05
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Loc: 51°N 4°E
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SAC lists it at mag 8.5 and 17' diameter; in comparison NGC 7789 is listed at mag 6.7 and 16' diameter.
To me it certainly doesn't look like a speck; the SAC listed diameter seems realistic. It appears more irregular though.
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63; Docter 15x60
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EdZ
Professor EdZ
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Loc: Cumberland, R I , USA42N71.4W
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Quote:
SAC lists it at mag 8.5 and 17' diameter; in comparison NGC 7789 is listed at mag 6.7 and 16' diameter.
To me it certainly doesn't look like a speck; the SAC listed diameter seems realistic. It appears more irregular though.
Lughinbuhl and Skiff state the extent is 8 arcmin. They observed only 12 stars in a 4'x2' area with a 150mm scope under mag 6.5 skies. Archinal and Hynes tells us the size is only 5 arcmin, with a brighest star mag 10.
If all the star light were concentrated in a 1 sq arcmin area, it would reach its surface brightness, which is mag 12.
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ronharper
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Reged: 02/14/06
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When I first became interested in ngc 7790, it took me a while to figure out what I was supposed to be seeing. There is a large loose asterism of relatively bright stars in that area, but that is not it. It is a little bitty dim smudge, I finally came to believe, quite difficult as EdZ says. This discussion is an interesting confirmation of what I thought, but was not sure of. Marks picture is not supposed to be to scale I know, but shows 7790 so large that it is misleading.
Otherwise on a good night, my 16x70, even at 60mm, reveals actual stars in ngc7789 (this still amazes me), and also in M52, in addition to the obvious bright one on the west side that even a 7x50 will show.
Ron
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Mark9473
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Reged: 07/21/05
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Loc: 51°N 4°E
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Ron, that's not a sketch and it's not a depiction of what it looks like visually. The scale is that of Cartes du Ciel's catalog parameters. I see an irregular smudge; it's elongated - could this be due to its close neighbours Berk 58 and NGC7788? If the sky clears in the next New Moon period, I'll attempt a sketch.
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63; Docter 15x60
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EdZ
Professor EdZ
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Quote:
Ron, that's not a sketch and it's not a depiction of what it looks like visually. The scale is that of Cartes du Ciel's catalog parameters. I see an irregular smudge; it's elongated - could this be due to its close neighbours Berk 58 and NGC7788? If the sky clears in the next New Moon period, I'll attempt a sketch.
Well, I don't think so.
Be58
Achinal and Hynes list it as 5 arcmin with a Br* of mag 15. K&S observed it with a 12" scope. I've never seen it in my 6" refractor.
NGC7788
is said to have a 9th magnitude star. The cluster is about 5 arcmin i dia, of a dozen mag9 to mag 12 stars. A&H list it as 4 arcmin. That minght be seen under mag 6.5 skies. I've never seen it.
NGC7790
is said to have 10 stars of mag 11 and mag12. 30 stars that make up the dense part of the cluster are compacted in a small 4' x 2' area. Under mag 5.5 skies, I recorded it as very small at 100x in my 6" refractor.
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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EdZ
Professor EdZ
Reged: 02/15/02
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Loc: Cumberland, R I , USA42N71.4W
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I had a brief opportunity to observe early this morning, and the sky was very good, so I took out the WO22x70 apo to refresh myself in the area around NGC 7790.
There is a string of 5 bright stars with the two brighest east and the two dimmest but also the closet to the west. 7790 is just ne of the center star. It was seen fairly easy as a small smudge. To estimate it size, I compared it to the two close stars towards the west. It was about 1/4 the size of the distance between that pair. I measured that pair when I came in and they are 10 arcmin apart. So, I measure 7790 as 2 to 3 arcmin in diameter at 22x.
I referenced Uranometria to try and find the other two close by clusters, Be58 and 7788. Neither could be seen.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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ronharper
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Reged: 02/14/06
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Thanks for the good directions and description Ed, I'll look when I get a chance.
Ron
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Mark9473
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Reged: 07/21/05
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Loc: 51°N 4°E
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The sky finally cleared so I took a shot at sketching the area around NGC 7788 and 7790 with my 15x60 (tripod mounted).
I had difficulty seeing the 7th star of Ursa Minor, so I'd put the NELM at 5.0. I didn't do an accurate LM determination in the binoculars, but noticed I could see a bit fainter stars than the 10.0 limiting magnitude of the chart I used. Edit: the attached sketch is based on a CdC chart going a bit deeper, to mag 10.5
I really don't have any sketching skills, so what I did was print out a star chart from Cartes du Ciel, without any DSO shown, then used a pen to indicate where I saw a bit of a glow as if from unresolved stars. For the sketch shown here I loaded a JPEG out of Cartes du Ciel into MS Paint and attempted to reproduce what I saw.
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63; Docter 15x60
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Edited by Mark9473 (09/10/09 05:17 PM)
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Mark9473
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Reged: 07/21/05
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Loc: 51°N 4°E
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Here is the same area with the DSO shwn and labelled; their position and size result from the SAC 8.0 catalog I use in Cartes du Ciel.
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63; Docter 15x60
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Mark9473
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Loc: 51°N 4°E
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BTW the field shown is 2°.5 across (I'm asuming CdC means this diagonally, but I'm not sure).
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Mark
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EdZ
Professor EdZ
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Loc: Cumberland, R I , USA42N71.4W
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well based on the info I provided from several sources earlier in this thread, I'd say SAC has got some of the sizes incorrect. FWIW, I'd trust L&S and A&H as the definitive resorces rather than SAC, who probably gets their data from NSOG, which although it can be good, has lots of incorrect data.
Some of those clusters you plotted are mag15 clusters, perhaps visible in 12" 14" scopes at 200x.
Your sketch for 7790 is more realistic than the plotted size.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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Mark9473
Post Laureate
Reged: 07/21/05
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Loc: 51°N 4°E
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I'm certainly not claiming SAC is the ultimate resource, EdZ. Neither am I claiming that when I see a glow, that means I'm actually seeing a true cluster.
On the other hand, SAC says, from left to right:
King 12 : mag 10.0
NGC 7788 : mag 9.4
NGC 7790 : mag 8.5 (this was certainly the brightest blob I saw)
Berk 58 : mag 9.7
So I don't think you can blame me for believing I saw some of these clusters.
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63; Docter 15x60
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Mark9473
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Reged: 07/21/05
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Loc: 51°N 4°E
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Quote:
Your sketch for 7790 is more realistic than the plotted size.
I would have drawn it even smaller actually, but Paint didn't have a smaller brush...
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63; Docter 15x60
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Mark9473
Post Laureate
Reged: 07/21/05
Posts: 3220
Loc: 51°N 4°E
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I have another catalog for CdC called "open clusters", which gives the attached result. The full reference of this catalog is:
New catalog of optically visible open clusters and candidates
Dias W.S., Alessi B.S., Moitinho A., Lepine J.R.D. <Astron. Astrophys. 389, 871 (2002)>
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63; Docter 15x60
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Mark9473
Post Laureate
Reged: 07/21/05
Posts: 3220
Loc: 51°N 4°E
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At this point I'm sufficiently confident to claim that I did see NGC 7790 in my 15x60, despite what you said earlier, EdZ.
Edit: of course in my original description I had the identification wrong.
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63; Docter 15x60
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Edited by Mark9473 (09/10/09 05:55 PM)
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