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NGC 185 & 147

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#1 Usquebae

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Posted 16 July 2013 - 09:32 AM

I had my first quality visit with Cassiopeia last night. I'm hooked on the OC! :jump: But I was only able to find one of the two "bright" galaxies near Andromeda. In my 8" at 75x, NGC 185 appeared as a largish, round, very faint blob of slight gray against black. Like a small version of M101. I'm %90 sure 185 was what I was looking at, but I couldn't for the life of me see 147.

It seems on the map that Omicron Cass, 185, and 147 make a nearly straight line, with 185 roughly equidistant from each of the others. I must have gone over 147 many times. Was using my 16/100 EP, so FoV shouldn't have been a problem. Any clues from the gurus? I expect most of you can see 147 through your 10x50 with both eyes closed, but I'm new and all this stuff is pretty hard to see for me, even in a light bucket. Will going up or down in magnification help?

Thanks.

#2 KidOrion

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Posted 16 July 2013 - 09:52 AM

147 is considerably more difficult than 185, with a lower surface brightness. Observing from an orange zone, I find 147 to be marginally visible in a 12.5", even when 185 is obvious.

Do try to find NGC 278 while in the area. It's on the opposite side of Omicron Cass from 185 and 147.

#3 Tony Flanders

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Posted 16 July 2013 - 12:51 PM

I had my first quality visit with Cassiopeia last night. I'm hooked on the OC! :jump: But I was only able to find one of the two "bright" galaxies near Andromeda. In my 8" at 75x, NGC 185 appeared as a largish, round, very faint blob of slight gray against black ... but I couldn't for the life of me see 147.


You're doing great! Seeing NGC 185 is no mean feat for a relative newbie with an 8-inch scope -- and probably operating under significant light pollution, like 95% of all people in the U.S.

As others have said, NGC 147 has much lower surface brightness, making it much tougher to spot. As usual, the trick is to go to exactly the right spot in the sky -- as determined by matching up the star field -- and then start applying averted vision, controlled breathing, and different magnifications.

#4 Jim Nelson

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Posted 16 July 2013 - 07:47 PM

Yeah, NGC 147 was a real nemesis for me. It's very close to 185 so it's almost certainly in your field of view at some point. That's what I found so frustrating.

I would try to print out a detailed star field if you can (I use SkyTools, which I love, but there are other cheaper options) so you really know when in you're in the right place, then practice your averted vision.

Also, get to the darkest skies you can! With dark enough skies, it ceases to be what I would call a difficult object (it's fairly bright in terms of total integrated brightness), but a little light pollution really mucks things up.

#5 Nick Anderson

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Posted 16 July 2013 - 08:19 PM

NGC 185 and NGC 147 are by no means easy targets for a beginner, so it's rather impressive that you already caught one of these. Back when I worked through the Caldwell objects with my 8-inch Dob primarily from a local ~5.7 magnitude site, after several attempts I couldn't snag NGC 147 due to its low surface brightness. A few months later I got it from a lower 6th magnitude site without too much of a struggle. Averted vision is the key here. They're both just discrete smudges, and they appear to me a bit larger than M110. It sure would be interesting to go back to that first site and give those galaxies another attempt there...

-Nick Anderson

#6 Achernar

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Posted 17 July 2013 - 10:23 AM

NGC-185 is farily bright and I have observed it a number of times with m 6-inch from a reasonably dark site. NGC-147 is a lot tougher, it is larger and fainter with a very weak brightening towards the center. It took a 10-inch for me to find it for the first time from a yellow zone site. Even from a blue zone site through my 15-inch it is still faint, although fairly easy to see. Light pollution is what makes this one a difficult object, you should have no problem seeing it from a dark site. It will appear along with NGC-185 together in the field of view of a low-power, wide angle eyepiece through your 8-inch. Forget about it if the moon's bright, or the skies hazy and or badly light polluted.

Taras

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#7 Usquebae

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Posted 17 July 2013 - 06:58 PM

Thanks all for your help. It's good to know I'm not missing something super-obvious. Not having learned to account for surface brightness, I tend to expect anything under mag 10 should be easy to see.

I live in a forested green zone with no neighbors in sight, so I'm optimistic I may find 147 yet. Sky was not perfect this time around, and I haven't yet built a blind to obstruct the glow from my own house. Better collimation couldn't hurt, either.

I am excited to seek out 278. I've mainly stuck to M & C objects so far, and whatever else is marked on IAU charts. The few times I've plotted my own path to objects using just RA and Dec coordinates were really fun.

#8 blb

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Posted 18 July 2013 - 01:44 PM

The magnitude for an extended object is like putting all the light from that object into a point source like a star. If you know your field-of-view size you can view a defocused star that has the same magnitude as the object you are viewing with the star defocused until it is the same size as the object you are viewing. It's a neet trick that was once used to determine the mag. of comets. So if you would like to know if you can see an 11th mag. object that is six arc minutes in diameter, just defocus an 11th mag. star until it is six arc minutes in diameter. This is not exactly the same but it will give you a good idea.

#9 Usquebae

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Posted 19 July 2013 - 09:32 AM

Buddy - thanks! That's great to know, but... it leads me to two more questions:

1. How do I judge an arc minute through my eyepiece? I do understand FoV somewhat, and have saved lists of the AFoV and TFoV of all my eyepieces for each of my scopes.

2. How do I interpret the "size" numbers on DSO lists? Some have a single number of minutes; others have two (like 4'x3').

I also don't understand 4' versus 4" - I would assume former is minutes, the latter is seconds. But then why is there an object listed as 240"x210"? Wouldn't that be 4'x3.5'?

I just don't get it... :confused:

#10 blb

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Posted 19 July 2013 - 12:41 PM

First you need to know the size of your field-of-view (fov) for each eyepiece/telescope combination. Let's say that your fov, for example, is 30' (30 arc minutes) in diameter and the object your looking at is twice as long as it is wide and it's length is approximately one third of the field of view; well one third of 30' would make the object about 10' long and since it is half as wide as it is long, it would be about 5' wide, that is an object that you would say is 10'x5' in size. What I often do with small objects is place one end of the object in the center of the fov and estimate how far it extends to the edge of my fov, so in the above example if it extends one third the way from the center to the edge of my fov, that would make the object about 5' long. With a little practice it is real easy to estimate the size of an object pretty close, just knowing the fov diameter.

There are 360 degrees in a circle, each degree is divided into 60 minutes (') and each minute is futher divided into 60 seconds ("). It is easier to work with minutes and decimal parts of a minute. For example 6 seconds is 0.1 minute and 18 seconds is 0.3 minutes, or 21 seconds is 0.35 minutes. With practice you can do this almost without thinking.

Read 4'x3' as the size of the object is 4 minutes long by 3 minutes wide. An object that has a listed size of 14' is an object that is about 14' in diameter.

Hope this helps.

#11 KidOrion

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Posted 19 July 2013 - 04:12 PM

I also don't understand 4' versus 4" - I would assume former is minutes, the latter is seconds. But then why is there an object listed as 240"x210"? Wouldn't that be 4'x3.5'?

I just don't get it... :confused:


I'm not an expert, but I suspect it was a planetary nebula, which usually are measured in arcseconds because the vast majority are under one arcminute in diameter. (?)

#12 Starman1

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Posted 19 July 2013 - 05:19 PM

From my notes with an 8" SCT:
NGC147:
med.size,v.faint,diffuse,no details, looks like brightening of night sky.

NGC185:
med.size,lrg.core,oval,diffuse edges,mottling and extension w/averted vision

These notes were taken in dark skies (mag.6.8 or so)

It might help to compare with NGC6822 in Sagittarius:
lrg,oval,v.faint,diffuse,even brightness,like brightening of background sky

or IC10:
nice!,v.low surface briteness, hints of arms? and core,intermittent details in outer parts of galaxy.

Lots of local group galaxies are faint. We get spoiled by M32/M110/M31/M33

#13 Astrodj

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Posted 19 July 2013 - 10:44 PM

Also, keep in mind that the published size of many DSO's is often somewhat larger than what you will see visually in modest scopes. For example, the fainter extent of many galaxies will show photographically or with video assisted images, but will not be visible at the eyepiece.

Good luck to you, sounds like you have good, dark skies!

#14 Usquebae

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Posted 20 July 2013 - 12:05 AM

Buddy - thanks again! I think I understand now. My table says I get 0.5 degrees TFoV with the 9mm Expanse in my C90. That equals 30 arc minutes diameter, so a galaxy that stretches 1/3 across the view is 10' long. If I've got that wrong somehow, please correct me.

KidOrion - Indeed it was a planetary nebula (NGC 246), and I now see that all the PLNNBs on the Herschel 400 spreadsheet I've got list size in seconds, even if they are bigger than 60"x60".

Don - Thanks for the notes, I will put them to use. I don't remember whose H400 sheet I printed, but his small scope is 12.5", so virtually all the notes describe things as bright and obvious. After barely spotting 2 globs (6544 & 6553) by accident below M8, I looked through the SGR objects on this spreadsheet to find out what they were. His descriptions made me laugh. I could scarcely detect a ghostly dark grayness against black, and this guy's resolving stars. :ohmy:

As for those bright galaxies you mentioned, I stayed up late and saw M31 for the first time just 2 weeks ago (I've got TALL east-west tree horizons). I've yet to see the other three. Looking forward to being spoiled by them! Especially if M31 is "overrated," like some posters are claiming. Call me green, but M31 is the cheese to my eyes!

:thanx:

#15 John_G

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Posted 20 July 2013 - 08:59 AM

For these faint, face on galaxies an observing vest can make a difference. After tracking along for several minutes using the hood, more details start to become visible.






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