G1

[Talitha]

I wasn't aware of this object until Mick posted his report, and it was clear tonight so i got a chance to see it. Finding it was really quite easy, it took less than 5 minutes using the MSA (Millennium Star Atlas). The volume was perched on a music stand at my elbow and upside-down of course, to match my eyepiece view.

Using M32 as a springboard, i used the atlas, a 32mm Plossl, and a home made fov guide to work my way towards the area where G1 is located. The fov guide is just a piece of clear plastic with a circle marked on it which matches the 32mm's fov. Primitive, but it works well.

The MSA had G1 marked on the page, but it lacked the details i needed to see exactly what i should be seeing in the eyepiece. But judging from the starhop, i knew i was right on top of the globular cluster... now it was only a matter of kicking up the power and picking it out.

The field was narrowed down eyepiece by eyepiece. I remembered Mick's sketch had a lovely arc of stars, and then a small triangle of stars, and then the globular cluster grouping. But when i cranked up the magnification on the triangle next to the arc, things began to go wonky. The lower left 'star' of the triangle was actually a double, and the upper left 'star' was a very tiny triangle. Avertedly, i could see a tight double star with a blurry spot nestled next to them. Could this be the formation containing G1?

I made a sketch while using the 7mm Axiom and then put the 5mm Celestron Ultima Plossl in to dig a bit deeper. Sure enough, there was definitely a non-stellar object tucked in with the two tiny stars... a globular cluster from another galaxy, how cool is that? The sketch is pretty raw, i didn't feel like turning on the main pc when i got home just to use the scanner, so i took a picture of it instead, and put it on my laptop. Labels identify the single star in the triangle, and also G1. I have to admit, i wasn't expecting anything this tiny but it was a lot of fun.

[acey]

I too viewed this object last night, following Mick's posting. Like you I found the field easy enough to locate (initially using the chart that Mick linked to, then TriAtlas to check). Between the two stars marked on the chart I could see the little triangle shown on your sketch, with one corner being a pair of stars and another being visibly non-stellar at medium power. I was using my 12" f4.9 flextube, Sky Quality 21.0 (limiting mag 6.1), with some high thin cloud reducing transparency by about 0.1 mag.

I started with a Baader 8-24mm zoom, and by cranking up the power to the maximum x187.5 was able to confirm the object. I then went to my highest power eyepiece, a 4mm Nirvana (x375) and with averted vision could clearly see three stellar points in an L-shape against a background haze: the cluster plus the 2 stars at its edge. However I couldn't definitely say which of the 3 was the centre of the haze, which appeared to envelope all three points; I could never entirely shake off my suspicion that part of the non-stellar appearance was simply due to the extremely close proximity of three equally bright points, though the haze was distinctly visible. It is indeed a tiny object, and I felt I wanted to push the magnification even higher to get a better view.

TriAtlas also marks two galaxies very nearby. The first, UGC 330, lies close to one of the marker stars used to find the glob (SAO 53990). I had little difficulty finding it, and could hold it steady in averted vision with a 6mm TMB planetary eyepiece (x250) as long as I kept the bright star out of the field. I found it small, round and featureless. Images show it as an elongated galaxy with a round bright central region: it was this central region I must have been looking at, of presumably high surface brightness (the galaxy as a whole is mag 15.0). I would guess that it was only the vicinity of the bright star that prevented this object from being spotted by the NGC observers. The other nearby galaxy is UGC 344. I tried for this one too and could see faint twinklings at the marked spot which I took to be stars: I couldn't detect the galaxy.

There is a detailed finder chart for G1, plus images etc, here: Deep-Sky Corner / And / G1, Mayall I: Andromeda's Globular . The chart also plots the galaxy I saw, naming it as PGC 2026.

[Doc]

For starters I'm really glad I got you two observing this Glob. You both have more darker skies then I do, mines only mag 4 so it took me ages to star hop.

Where we dither is I cannot remember the point of the triangle being a double star, maybe my seeing was to bad to see. Also you seem to have G1 in a slightly different place then me Carol, but then I was drawing under a blackout blanket, trying to hold a torch between my teeth and nudging the dob, it doesn't really help.

It is indeed a very small object but I'm pleased we gave it a go. And well done acey in seeing those galaxies, I did know they were there but had no chance of seeing them.

[Talitha]

Mick, i'm really glad you posted a report on G1... i'd never seen a globular cluster outside of the Milky Way before, but now i have.

I did a few measurements in SkyTools3 this morning. The double stars (mag 13.2 and mag 13.3) at the corner of the triangle have a separation of 1'2". The two stars flanking G1 weren't displayed in the program (neither is G1) but i wanted to find out their designations and separation. Problem is, they never displayed onscreen even after a stellar saturation increase. They weren't displayed after generating dimmer stars from the supplementary catalogs, either.

No idea what's up with that.

Even though i couldn't get a separation on them, i can tell you one thing for sure.. they're definitely closer than the 13.2/13.3 double star. Even though the G1 group wouldn't display on my program, i wanted to see how far it was from the other two corners of the triangle... a guesstimate of 2' was made using my sketch and the measurement tool in the program.

So far, the only image i'd seen of G1 was from the Hubble, but a google image search this morning turned up a few of the triangle which show the size and proportion of things very nicely.

image 1 image 2

[yeti monster]

Well guys, you are really giving me a renewed bout of aperture fever here with your 16"ers!

Good work on finding this Glob and on showing the results.

[Talitha]

renewed bout of aperture fever

Resistance is futile...

TBH, i'm kicking myself for waiting a decade to get a serious aperture increase.

Go ahead and treat yourself, you won't regret it.

[yeti monster]

The list of 'wants' already exceeds my pocket money. As soon as ebay allows the listing of Grandmothers, I'll be there..........

[acey]

Well guys, you are really giving me a renewed bout of aperture fever here with your 16"ers!

Good work on finding this Glob and on showing the results.

I found it with a 12", it's generally considered an object for as little as 10" but has even been seen with 6". We all have aperture fever but the key to G1 isn't huge aperture; it's a good star map, a dark enough sky, and very high magnification.

G1 has a quoted magnitude of 13.7; the stellar core is probably more like 13.5 or brighter. A 6" scope will give you a magnitude gain of about 7 over your naked eye so in order to see the core of the glob you would need a sky of limiting magnitude around 6.5. With an 8" it should be enough to have 6.1, with 10" 5.7, and with 12" a limiting mag of 5.2 should be enough to see the core. I had limiting mag 6.1 and with my 12" could plainly see G1 as an extended object. If I could have gone higher than x375 I would have seen it better (but I ran out of eyepieces). With a 16" it should be possible to glimpse the tiny L-shape of the core and two foreground stars given a sky of limiting magnitude of 4.6. To see the faint haze surrounding the core would, I think, require greater darkness. So you don't need a light-bucket as long as you can get to a dark enough sky, though what makes things harder for small scopes is the requirement of high magnification: a 12" can handle x400 a lot better than a 6".

As with nearby UGC 330, it's interesting that the NGC/IC compilers overlooked G1 (simply because it's so tiny). It was only discovered in 1953 by Mayall and Eggen. It's a fascinating object and I'm grateful to Mick for having spread the word on this one, which is certainly worth trying with modest aperture. The link I gave earlier has a very detailed finder chart showing the little triangle (also clearly seen on Carol's sketch) that is the key to finding the object. It also has descriptions of the views obtained with 6" and 12" aperture, noting that with 6" (and a dark sky) only the core was seen. The CCD image at the site shows a further challenge: two very faint stars just NE of the cluster, apparently detectable with 12", though I didn't notice them.

G1 is apparently the only M31 globular that can be seen as non-stellar in amateur scopes, though many more are of sufficient magnitude to be seen as stellar objects. Only other one I've seen (or looked for) is G76, but plenty more are described at the following link, from observations with 18". Quite a few of them should be reachable with 12".

http://astronomy-mall.com/Adventures.In.Deep.Space/gcm31.htm

[Talitha]

Need to correct myself on something...

The separation between the double stars (mag 13.2 and mag 13.3) at the corner of the triangle isn't 1'2"... it's 18".

The 1'2" distance is between the double and the GSC star.

[EntropyStar]

Heys,

I've made G1 a target for myself when the skies decide to clear round here, and in the interim period I've been collating a few resources to enable finding this ellusive object.

Stunning high-res image/map of M31 with globular clusters highlighted (G1 is just outside the FOV in this image) : http://www.robgendle...saicglobs2.html

Central globular clusters image/map (I suspect the majority are beyond most amateur scopes): http://www.robgendle...obs2center.html

Article detailing how to find G1 with finder images (bottom of the page): http://astronomerica...acewalk-m31.php

Star hopping guide + course and fine finder maps: http://www.nightskyi...obular_cluster/

Best of luck to everyone with this one!!!