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Abell 1656 (Coma Galaxy Cluster)

Abell 1656 (Coma Galaxy Cluster)

Drawing data

Abell 1656 (Coma Galaxy Cluster): NGC 4889, NGC 4874, ... (about 70 galaxies) Com GX
Date(s) of observation:
2015.03.19/20. Ágasvár
2015.03.20/21. Ágasvár
Place(s) of observation:
Telescope(s) used:
16" f/4.4 Newtonian (MCSE Dobson)
Enlargement(s) used:
176x (10mm Delos)
Author / Observer:
Peter Kiss


Abell 1656 a.k.a. the Coma Galaxy Cluster is a dense and rich cluster of galaxies with thousands of members in the constellation of Coma Berenices. The Coma Supercluster containing Abell 1656 lies 300 million light years away. It is the closest point of the CfA2 Great Wall. Both the visible (more degrees) and the physical size (> 20 million light years) of Abell 1656 are impressive. Its mass and density are enormous. As a comparison the size of our Local Group is about 10 million light years and it hosts only about three galaxies of considerable size (Andromeda Galaxy, our own Milky Way and M 33). There are two giant elliptical galaxies at the center of the Coma Cluster: NGC 4874 and NGC 4889. The latter is brighter with 11.5m and it harbours one of the largest black holes known with a mass of about 21 billion Suns. The majority of Abell 1656's cluster members are ellipticals and lenticulars. The spirals are more on the outskirts of the cluster and they look extremely good based on the Hubble images.

Coma Galaxy Cluster. Inverted drawing made using a 16" Newtonian telescope.
Coma Galaxy Cluster. Inverted drawing made using a 16" Newtonian telescope. Peter Kiss

The Coma Cluster was discovered by William Herschel in 1785. It has been pretty well studied because it is close to the north galactic pole thus far from the absorbing dust clouds of the Milky Way. Also, though it is very far it is still relatively close compared to other clusters of similar size. To name only one among the numerous scientifical results, it was the Coma Cluster where a considerable amount of dark matter was detected for the first time (by Fritz Zwicky back in the 1930's).

Galaxies in the Coma Cluster.
Galaxies in the Coma Cluster. The colors stand for galaxy types. The two central giant ellipticals are marked with deep orange. Ellipticals and those galaxies that I didn't have any information about their types are marked with orange color. Green stands for lenticulars (S0 and SB0) and blue means spirals.

The eyepiece impression of Abell 1656 is worth a few words as well. Most of the 60-70 galaxies that are in the drawing are not that very faint (brighter than 15.0m) therefore they are really spectacularly crowding the field of view. But there isn't any real detail visible in any of the galaxies. No wonder since the visible size of the members is generally very small, about 20"-40" (arcseconds). It is interesting that there is a background galaxy in the drawing as well. NGC 4858 is about 70 million light years behind the Coma Cluster.

This is a panorama drawing that is it covers more than a field of view of the telescope. I drew 28 stars into my sketchbook from the map (Guide) before drawing by the telescope at night.

Some selected galaxies in the telescope and in the Hubble images

Fields of the HST (Hubble Space Telescope) images below (in red), and the field of the 16
Fields of the HST (Hubble Space Telescope) images below (in red), and the field of view of the 16" Newtonian telescope I used to draw the cluster (in blue) superimposed on my drawing.

You can see the Hubble (HST, Hubble Space Telescope) images of a few selected galaxies in the Coma Cluster below. By taking a look into the telescope the fine details of these very deep images can of course not be seen. But I think these images demonstrate the beauty and the spectacularity of the Coma Cluster pretty well.

Hubble image of NGC 4889.
Hubble image of NGC 4889. Credit: NASA & ESA. Source:
Hubble image of NGC 4874.
Hubble image of NGC 4874. Credit: ESA/Hubble & NASA. Source:
Hubble image of NGC 4921.
Hubble image of NGC 4921. Credit: NASA, ESA and K. Cook (Lawrence Livermore National Laboratory, USA). Source:
Hubble image of NGC 4911.
Hubble image of NGC 4911. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA). Source:
Hubble image of IC 4041 (left) and IC 4042 and IC 4042 galaxies (right).
Hubble image of IC 4041 (left) and IC 4042 and IC 4042 galaxies (right). Credit: ESA/Hubble & NASA; D. Carter (LJMU) Acknowledgement: Nick Rose. Source:
Hubble image of NGC 4881.
Hubble image of NGC 4881. Credit: Hubble Space Telescope WFPC Team, NASA/ESA, STScI. Source:
Hubble image of NGC 4858 (down).
Hubble image of NGC 4858 (down). Credit: NASA/ESA Hubble Space Telescope, Hubble Legacy Archive. Source:

The galaxies I saw in the telescope are summarized in the table below. Brightnesses come from the Guide planetarium program. It is possible that the brightnesses were taken from different catalogs and they might even correspond to different wavelengths (B, V, etc.). Therefore the brightnesses are not to be taken as absolutely precise.

There is a short description of a few selected galaxies below the table where I write about the eyepiece impression.

Galaxies in the drawing
namebrightness [m]
NGC 484813.7SBc
NGC 485014.4S0
NGC 4851 (PGC 44439)14.2S0components
NGC 4851 (PGC 83717)15.0S0components
NGC 485815.2SBb
NGC 486013.5E
NGC 486413.6E
NGC 486513.6E
NGC 486714.5E
NGC 486913.8E
NGC 487114.2S0
NGC 487214.4E-S0
NGC 487314.1S0
NGC 487411.9E
NGC 487514.7S0
NGC 487614.4E
NGC 488113.5E
NGC 488314.4SB0
NGC 488613.9E
NGC 488911.5E
NGC 489513.2S0
NGC 4895 A14.6Estellar
NGC 489813.6E
NGC 490614.1E
NGC 490713.6SBb
NGC 490813.2E
NGC 491112.8SBb-c
NGC 491914.0S0
NGC 492112.5SBa-b
NGC 492313.7E-S0
NGC 492713.8E-S0
IC 83914.8S0
IC 394314.7S0-a
IC 394614.2S0
IC 394914.1S0
IC 395514.4SB0
IC 395714.6E
IC 395914.2E
IC 396014.7SB0stellar
IC 396314.7S0
IC 397314.4SB0
IC 397614.7Estellar
IC 399814.6SB0
IC 401215.0Estellar
IC 402114.9Estellar
IC 402614.6SB0stellar
IC 404114.4Estellar
IC 404214.3SB0
IC 4042 A15.0S0
IC 404513.9E
IC 405113.6E
UGC 807115.3S?
PGC 4436415.7(?)
PGC 4436715.8(?)
PGC 4446715.2(?)
PGC 4453715.3(?)
PGC 4456015.7(?)
PGC 4463616.0(?)
PGC 4465616.1(?)
PGC 4466215.9(?)
PGC 4471616.0(?)
PGC 4478415.4(?)
PGC 4484915.7(?)
PGC 4486416.4(?)stellar
PGC 4492915.9(?)
LEDA 8368815.4(?)
LEDA 8370216.5(?)stellar
LEDA 8375516.2(?)
GMP 4837(?)(?)seen???
GMP 4838(?)(?)seen???

I describe the eyepiece impression of a few selected gaaxies below. The most common detail I saw was only that the majority of the galaxies have a stellar core. And a couple of galaxies are elongated.

NGC 4889

This is the central galaxy of the Coma Cluster. It is elongated and it has the brightest core. It is very suddenly getting brighter towards the core.

NGC 4874

It is just a little fainter than NGC 4889. This galaxy seems to be much more the center of the cluster in the telescope because of its many satellite galaxies. Its core is fainter than that of NGC 4889 but it is getting much more gradually brighter towards the core. This probably adds to the feeling that NGC 4874 is the center as well.

I drew one of the satellite galaxies (PGC 44636) to the wrong position. By comparing the drawing and the photo you can see the error.

NGC 4921

This is one of the large spirals of the Coma Cluster. I saw a bright, small, almost stellar core. The disk of the galaxy is perfectly round and uniformly bright. The edge is diffuse. I didn't see any more details but this is a very spectacular galaxy in the photos.

NGC 4921 is moving at a high speed through the intergalactical medium filling the Coma Cluster. This compresses / tears away the gas (neutral hydrogen) of NGC 4921. The signs of this interaction can be seen in the Hubble image as well (deformed dust lanes).

NGC 4911

This is another beautiful spiral next to NGC 4921. I didn't see the core here but the inner brighter region of the galaxy seemed to be elongated. This was surrounded by a faint round halo. This is in good agreement with the photo: the bar, the brighter spiral arms and the tilt of the galaxy cause the elongated inner region. I didn't see the companion galaxy NGC 4911 A.

NGC 4858

This distorted barred spiral galaxy (as seen in the Hubble image) is a background galaxy. It does not belong to the cluster. I didn't see any details.

Stellar looking galaxies

After processing my drawing I identified several pointlike objects as galaxies. Before / during drawing at night by the telescope I didn't take a look at the map or any photo. So I didn't know where the galaxies were. I was afraid that I would draw stars as galaxies because of the sky or the telescope not being perfect. But the objects I drew as diffuse spots (galaxies) are in fact galaxies. And there were several galaxies which I didn't see as extended patches. I drew them as stars.

Galaxies below 16m

There are some pretty faint (around / below 16.0m) galaxies in the drawing. These were indentified without knowing their positions beforehand as well. I certainly saw them. It is possible that the brightness given in the catalogs is off by as much as a magnitude. Or it's not the V band magnitude. I am not sure that these galaxies are so faint. Also, my experience is that the limiting magnitude of a 16" Newtonian is around / below 16.5m in good conditions.

GMP 4837, GMP 4838

I saw the not too faint 15.2m star as a double. But it is not a double star according to the photos. On the other hand there are these two tiny galaxies just in the right place. It is very questionable if I had seen them at all. Probably I saw the star as a double erroneously and the tiny galaxies are too faint for the 16" telescope. I didn't find and brightness data for these galaxies.

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