Object of the Week, July 16, 2023 – NGC 6453

[Howard B]

(forgive the early post, I'm leaving for the Oregon Star Party in a few minutes!)

NGC 6453_HST.JPG

NGC 6453 is one of those objects that’s easy to locate, isn’t terribly difficult to see, but is wonderfully fascinating once you know a little about it.

NGC 6453 is a globular cluster that’s seen through M7’s western border, so it has no relation to the spectacular open cluster – it just happens to be in the same lie of sight. 6453 is approximately 33,000 light-years away, which places it on the opposite side of the galactic center from the Sun. And it’s about 2,700 light-years below the galactic plane, putting it outside the Milky Way’s disk, like many other globular clusters.

And yet, in spite of all the 33,000 light years of intervening gas and dust near the heart of the Milky Way, it still manages a visual magnitude of 9.2, making it accessible to anyone with an 8-inch or larger scope. Even if you have little interest in M7, this improbably observable globular cluster is a must-see.

M7 finder sketch.jpg

Depending on the source, the apparent diameter of NGC 6453 is anywhere from 21.5? to 7.6? across. Given my observations, I favor the smaller diameter.

With my 8-inch f/3.3 scope, NGC 6453 was a small, fuzzy glow without any resolution into individual stars. I could resolve only a few stars with the 30-inch, and there’s a good chance they’re just foreground stars.

But at best, I can observe this part of the sky when 6453 is only about 9 degrees above the southern horizon. Perhaps I’d have a better chance to resolve the cluster if it were higher in the sky for another go. Let us know what you’ve seen!

NGC 6453 sketch_30 inch.jpg

(PS - Don’t forget to enjoy M7 while you’re here…)

[lamperti]

With a 20" at 73, 195 & 318x: "This shows as a faint glow under 73x. Under 195x, it is a bit brighter but little resolution. 318x = some stars around the edges (these are foreground stars). The rest is a round tight glow. When classifying, don't let the foreground stars confuse you; it really is a IV!"
Three years later with a 22" at 48x, I was able to see this GC along with two open clusters: M 7 and Cr 355 (Trumpler 30) in the same field.

[wvreeven]

I managed to pick this one up with my old home built 6" newtonian from Southern France. I noted that is was an equally lit faint haze that suddenly fades into the background. I'll need to try this one from Chile with my 20" dob when it's near zenith.

[Don Pensack]

This one culminates for me at 21° above the horizon, but even at that altitude it is hard to resolve completely into stars in a 32cm scope.
I can see why--the horizontal branch is mag.17.7, and the cluster is 3.8' at the mag.25 isophote, so it needs a fairly high magnification, and seeing that low is rarely great.
total integrated magnitudes are all over the place, depending on source. I see m.9.19 to m.10.8 depending on source.

[oliva]

Hi,

One of my favorite sky vistas! Marvelous, the beautiful pair of M7 and this tiny GC.

14 inch Newton under dark sky in Spain:

Very small, round GC without a noticeable increase in brightness towards the center. Already visible at 56x spotting M 7 as a very small, compact cloud in the outside area. At 114x the GV is partially resolved and looks granulated. At 430x two faint stars become visible to the southwest and southeast and the cluster appears indeed resolved, although the background is still grainy.

Namibia using a 25 inch Newton:

Small irregularly shaped globular cluster lying on the border of M7. Could be fully resolved. Difficult to see though as the seeing isn't the best. 280x.

Oliver

[Raul Leon]

Hi, here's my observation from 8/12/2023: ngc 6453 globular cluster in Scorpius ; mag:10.07 ; size:7.6' ; fairly bright but small, unresolved except for a couple of outliers or foreground stars. I used a 6mm Ethos at 300x with my 14.5 StarStructure f/4.3ngc 6453.jpg