Object name: ABELL 2634

Designation(s): NGC7720, NGC7726, IC5341, IC5342, ABELL 2634,

The Abell galaxy cluster 2634, in the north central part of the Great Square of Pegasus, is listed at NED as consisting of 125 galaxies over a 3 degree radius from a point slightly southwest of NGC 7720 as labeled in the annotated image. I don\'t quite understand the count of only 125 galaxies as there are nearly that many known to be in the cluster in my very small field of view. While some appear members of a cluster some 1.5 billion light-years distant most are at about the 0.4 billion light-year distance to the Abell 2634 cluster. It is listed as morphology class BM 2. This would indicate it has more than one major cD or bright cluster galaxy like the Coma Cluster. While NGC 7720A is a bright elliptical it doesn\'t seem large enough to qualify. Though several other large ellipticals are in the image they too aren\'t listed as cD or as major bright elliptical though IC 5341 comes close. Maybe it is just the large number of quite large ellipticals that gives it this morphology rating.

NGC 7720 is a huge elliptical. It was discovered by William Herschel on September 10, 1784. It\'s not either H400 program. I measure it as just under 300,000 light-years in diameter though that halo may also include the halo of NGC 7720A, in which case that may be too large. Still, I think it pretty close to the correct size. Papers indicate it has hundreds of globular clusters though I didn\'t pick those up. Like most clusters, it is composed almost entirely of elliptical and S0 galaxies. The only classic spiral in the image may be NGC 7726 at 330 million light-years. That may put it too close to be a true member of the cluster or it may just have a high velocity compared to the average cluster member. Several other galaxies at about that redshift are also in the image though most are 370 million or greater distance. The identification of NGC 7726 is somewhat of a question mark. Entry 7726 is an obvious error and this is the most likely object seen but mislocated. Still it can\'t be proven to be what was originally seen. See the entry for it at the NGC Project for details. The NGC project site is down for rebuilding which may or may not happen. NGC 7726 is the best guess as to what Lewis Swift was seeing on August 8, 1886.

The strange galaxy in the image is LEDA 085553 at the top edge. It is a very irregular galaxy also a bit close to be a cluster member at 350 million light-years. It consists of many blue star clouds all in a single halo of stars. It is one of only two blue galaxies in the entire image. Even NGC 7726 is mostly red and thus containing mostly old stars. The other blue galaxy is LEDA 085609 southeast of NGC 7720. It is listed as S/I. It appears in my image to be a blue spiral with a large plume to the east. It may be a disrupted spiral. The only other galaxy with any significant blue is the slightly blue LEDA 085559 also listed as S/I.

Another galaxy worth looking at is CGCG 476-080 on the western edge of the image. While listed as S0 it appears to be a ring galaxy though this isn\'t mentioned at NED.

In annotating this image I listed all with redshift data at NED along with classification if given. Those listed only as G or by their classification rather than catalog name had no catalog name other than one that consisted solely of its sky coordinates. If no classification was available I just used G for galaxy. This is likely the densest annotated image I\'ve done. They are usually fun but it gets boring when this dense. Took a good 2 hours. Hope it was worth it.

The two IC galaxies were found by Herbert Howe on November 27, 1899. Most sources just say 1899 but Steve Gottlieb as this date. I don\'t know his source.

This was taken on about the best night I had in August 2013. At least I made no notes about it being poor in some way like I did nearly every night this summer and fall. Still, most of the Luminance data came from a September night. Due to sky conditions, I started taking only color data on the commonly poor nights and only luminance on the nights worth doing it. I now have many objects with no luminance waiting for better conditions next year. After those piled up, I gave up and went back to using whatever the night gave me and cussing a lot.

14\" LX200R @ f/10, L=4x10\' RGB=2x10\', STL-11000XM, Paramount ME