7 replies to this topic

[Asbytec]

It's been a long monsoon season. Following the sketching forum is hard on a guy with cloudy nights. But, the dry season is pushing it's way south and get to jump into the mix, again. This time with a tough one, but turned out to be interesting. It's NGC 7742, a Seyfert galaxy in Pegasus. Looks like a fried egg, it's nickname, in pictures. Not visually. Couldn't even smell the bacon. 

 

So, okay, at about 75x, I could tell it was in the FOV, but just barely. Something fuzzy was there. Indistinct, just faint. Jumping up to 108x with a 18mm Ortho, well it was still there. But I was catching flashes of some kind of weak elongation. Other times kind of face on. Just could not decide what I was looking at. It was pretty faint at close to 12th magnitude and about 21.5 Mag/Arcsec^2. I guess my limiting (stellar) magnitude was approaching 14 as a 13.5 Mag star near the galaxy was seen pretty easily. 

 

So, cranked it up a notch to 162x with a 12mm Ortho. Okay, so things began to happen. Deep breathing with a dark shirt over my head, staring into the darkness and relaxing, then easing onto the exit pupil, okay was getting some real good glimpses. I began to see the thing was really very much round. Distinctly round. I guess in the end, that was the striking thing...how round it really was. No star like nucleus was visible. Just a round patch in the sky.

 

On the elongation thing. I knew I had an edge on galaxy in my observing list, but was not sure if this was it or not. But, I did get the "feeling" it had some elongation to it. Roughly NW to SE. Stubby and broad elongation, not like an edge on. So, I noted it and kind of decided that's what I saw. Some possible elongation, but definitely a very round core with no noticeable nucleus. 

 

I would not think much of the elongation part and may have written it off as spurious. Checking afterward, images simply do not show any elongation whatsoever. None. But, I did get the feeling more than once. And I ran across the only sketch I could find of NGC 7752 done through a 12" scope. Guess what? He showed it elongated, too. So, maybe there is some visual effect, after all. So, I think I saw the apparent elongation he saw and decided to trust myself and throw it out there. 

 

http://www.fjastrono...laxies/ngc7742/

 

Anyway, first observation and sketch in almost a year. Thanks! 

 

Edited by Asbytec, 28 October 2016 - 12:02 PM.

[niteskystargazer]

Norme,

 

Nice sketch of  NGC 7742   .

 

CS,KLU,

 

 ,

 

Tom

[frank5817]

Norme,

That is a nice way to kick off your observing season.
NGC 7742 looks very good in your sketch.
I hope the dry season is getting started in earnest.

Frank

[tommy10]

Very nice sketch, nice to see you sketching again, thanks for sharing,

[azure1961p]

Boy, you jumped right in on a galaxy Messier never knew. 

 

I did some googling on this object andvtge ellipse can be explained fairly easily. The ring structure surrounding the "yolk" is NOT evenly lit. Indeed opposing sides are both dimmer which could then visually give a slightly flattened look to the "egg white". Had the light been truly uniform in the ring, you would've seen a circle no doubt.

 

I knew of this galaxy but not of it from observing. If I'm not mistaken, Omeara covers this one in one of his books.  

 

It's interesting that being a Seyfert, no stellar or substellar nucleus was evident, good testimony that the classification doesn't necessarily guarantee this detail visually.  Ill guess that the yolk is killing the contrast of it that might normally be available to your aperture?

 

Well, an impressive observation to ring in the season, and none too easy it would seem!

 

Well done.

 

Pete

[Asbytec]

Thank you all. Looking forward to joining you this year.

Pete, where did you find the info on the uneven brightness. It was late, really had little time to research it.

One observation I wrote off as spurious, when I was trying to figure out what the heck I was looking at, was a twin sharp cut off in brightness on both E and W sides. Almost like two dust lanes. I wasnt real sure thats what I saw, maybe just another glimpse of the elongation I cannot explain from images.

Like to read more on its uneven brightness. That's curious.

You're right about the star like nucleus. It shows well in images, but my notes specifically state no nucleus seen. I almost went back to confirm it, but after losing dark adaption the clouds rolled in after midnight. So, no chance to confirm what my notes already stated.

The circular core was a striking feature in itself. The hint of elingation adds to the beauty. This was a fairly difficult object to observe.

What does Omeara say? Through his 4"?

Edited by Asbytec, 28 October 2016 - 10:25 PM.

[Asbytec]

The mystery deepens. Does this guy show dark arcs near NGC 7742's core? In his sketch, the lone star to the left should be approximately north west putting the dark arcs he shows about NE and SW. Which seems to match the apparent elongation NW to SE. Amazingly, he appears to have noted some dust lane like features. Those features are possibly the same ones I wrote off as spurious in my comment above. Need a moment to gather my thoughts...

 

http://www.geocities...23/ngc-7742.png

 

This is a sketch done by Taras?

 

Anyway, here's a couple of images to help put things into perspective. 

http://cseligman.com...ngc7742wide.jpg

http://skyservice.ph...812&opt=&query=

 

We can see the inner ring is deep within the galaxy. I doubt seriously if I could see any of the dark inner ring, and the brighter ring is what gives it a distinct circular core. The faint outer halo extends almost to the nearby 13.5 magnitude field star, but I drew that star well outside what I could see. So, I was not seeing much of the halo. So, any mention of dark arcs seemed spurious in my case because it was so very fleeting, especially if we think they are inside the bright halo. I just think they are too small to be resolved and very low contrast. But, maybe outside the ring?

 

My guess is, the bright inner ring gives it the distinct circular appearance of the core, and some of the halo was visible. Curious that one observer sketched some apparent elongation and another sketched some dark arcs that appear to be in the halo itself and not near the nucleus. I did get an elongated view more than once, and only once (likely spurious) impression of a sharp cut off where the second sketch placed two dark arcs. I have to wonder though if there was something to be seen. In a 6", I dunno...that's a tall order. 

 

Edit: More mystery. A double ring? 

http://www.astrophot...ES/NGC 7742.htm

Edited by Asbytec, 29 October 2016 - 05:15 AM.

[azure1961p]

Norme,

 

I believe that sketch is by Wes Stone, a very prolific observer with a good eye.

 

Pete