Jump to content

Narrowband

Abell clusters and Copeland’s Septet with a 12”


acey

Recommended Posts

Equipment: Skywatcher Flextube 300P, TeleVue Plossls. Rural site, limiting magnitude 6.

Having set myself a project to observe the brightest Abell clusters with my newly acquired scope, I began on 20th March with one of the richest and best known: Abell 1656 (the Coma Cluster). This was my first proper experience of cluster-watching with a 12” and it was reminiscent of looking at the Virgo Cluster with an 8-inch. With so many galaxies to try and identify, the best way is to draw a diagram showing every fuzzy you can see at the eyepiece, then use a chart to name them (e.g. Uranometria appendix A8). Luginbuhl and Skiff provide notes on about 30 cluster members (pp87-89 of Observing Handbook) and I was able to see nearly all of them. A particularly nice spot was the region around NGC4874, where I identified three close companions (-71,-72,-73), though I didn’t spot IC3998, unless perhaps I mistook it for a star.

After spending over an hour and a half on the cluster, I took a break with some nice bright objects – M64 showed it’s “black eye” very well and M13 was resolved all the way to the core (I wondered if my 12” would show redness in any stars but I couldn’t see any). I then moved on to Abells 2197 and 2199 in Hercules (Uranometria A3). Abell 2199 is centred on NGC 6166 which I found fairly bright; its four faint companions were also visible though I was unable to split 6166A and D, which appeared single with averted vision. Nearby 6158 was also seen. All the other cluster members are beyond NGC and I didn’t expect to see them so I turned my attention to neighbouring Abell 2197, centred on moderately bright NGC6160, which had a speckled appearance. To the west I found a single faint fuzzy at the location of 6141/-/-45/-47 ( nearby 6138 was not seen). Heading back east, 6173 was rather large and moderately bright, 6175 was faint but seen with direct vision, 6174 was possibly glimpsed but impossible to confirm. Dawn brought a close to what had been a very enjoyable first crack at the Abells.

On the 28th I was back again in still, cold air (the thermometer hit -6 celsius) and ready for a crack at Abell 1367 in Leo (Uranometria A11). I’d briefly seen the brightest members during my scope’s first light a few weeks previously but the weather hadn’t been kind. This time round I had all the time I wanted, and I made the most of it. Over the course of about two hours I tracked down all the entries in Luginbuhl and Skiff (pp 144-146), about 20 galaxies, plus others not listed such as NGC3859,-64,--67,-68. The busiest area is around NGC 3842, where I identified 10 galaxies in a single medium power field, including my first UGC (6697) and a couple of CGCGs (97-86 and 97-90). I’d been wrong in thinking the NGC was as far as I could go: now I had some idea how far I could expect to reach with the 12”, and it was very encouraging. Increasing aperture won’t suddenly make M51 look like it does in photographs, but it increases the number of reachable objects by a big factor. While touring the cluster I picked up a number of other UGCs, CGCGs and MCGs (+04-28-43/44, plainly seen but not split, and +3-30-83, much elongated, seen with direct vision).

I made a detour to nearby Copeland’s Septet, expecting the seven NGC objects to be a picnic – but I was wrong. I was able to identify only 3 members (NGC 3750, -53, -54), all faint. The faintest, 3750, is listed as magnitude 15.2, the remaining members are fainter. So this would appear to be my limit for the 12” – actually it’s fainter than I expected to reach, because with my old 8-inch I don’t think I ever made it to mag 14, and a 12” should manage only about 0.9 mag fainter than an 8”. I think that having nice new clean optics must have something to do with it. Better make the most of them!

What I’ve learned from all this is that catalogue listings can be deceptive – the only way to find out if something is visible is to look for it. Actually I knew that already. What I really learned is that this new scope is fun!

I ended my night with a few Messiers: M82 was the most enjoyable, plainly showing its dust bar and distorted form. Dawn came all too soon.

Link to comment
Share on other sites

Great report Acey.

That must have been a fantastic night. Have yet to take mine to a dark site so don't really know how dark it is to get down to mag 6.

You are right in saying these big dobs do see so much more.

Thanks for the report.

Link to comment
Share on other sites

  • 1 month later...

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.