Hi Paddy,
It is impressive to be able to visually detect a single star-like source at such an enormous distance. Some papers give the distance of this cluster of galaxies as 190 million light years.
You are a very careful observer, often picking up interesting features,
even within challenging objects. That is why I find it valuable to inform you about the range of phenomena which are potentially visible in galaxies, even without the use of CCDs etc.
N5292 is an interesting and luminous outlier of the cluster; in this Galex ultraviolet image, there is a very large ring structure in its central regions that might accord with what you have observed:
[ Could look like a large diffuse annulus or ring, visually]
This must be one of the least known members of the population of (relatively) bright galaxies!
Blue 13th magnitude might not seem too bright for a galaxy, but considering the large distance of this galaxy, NGC 5292 is a most impressively luminous spiral.(at least comparable to M100 and M99 and M61, which are the first ranked spirals in the Virgo Cluster)
Actually, NGC 5292 might be as bright as B= 12.5 (large discrepancy between various catalog magnitudes)
cheers,
Robert
Some thoughts Regarding the distance of Abell 3574
The distance of this cluster of galaxies is usually given as 58 Megaparsecs (= 189 million light years), but mostly this distance has been derived using not-very-accurate methods of distance determination;
such as the Tully-Fisher relation and Velocity Distances.
This distance estimate could very easily be wrong by as much as 15 -20 percent (if not a little more).
In fact, the galaxies of Abell 3574 (= the IC 4329 group of galaxies) seem of remarkably large angular sizes compared to the angular sizes of the galaxies of the Centaurus Cluster of Galaxies (N4696, N4709, etc., etc., etc.) despite the fact that the Centaurus Cluster (= Abell 3526) is
supposed to be significantly closer than Abell 3574.
At face value, it seems to me that Centaurus Cluster could be further away than is usually thought and/or Abell 3574 could be closer than usually thought.
The degree of resolution of the galaxies in Abell 3574 would be remarkable if it is nearly 200 million light years away. These galaxies seem to be too large and too easy to observe to be this far away!
(as a comparison, the Virgo Cluster is 50 million light years away)
The recession velocity of this cluster is often given as about 4870 km/s in the CMB reference frame, a velocity which also yields a very large distance, for plausible values of the Hubble Constant. However, I note that Richter in 1984, A&AS,
58, 131 gives only 4253 km/s as a mean velocity of this cluster (corrected to the centroid of the Local Group).
So there can be a lot of error in estimating the true cosmological velocity of a cluster of galaxies. (not forgetting that there is a
1500 km/s peculiar velocity in the line-of-sight of one of the subclusters of the Centaurus Cluster!)
In general, the IC 4329 group is remarkably poorly known and studied compared to similar clusters in the Northern sky!!
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