EAA Observing Session: 2, January04/01/2025
Astronomy
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Well I guess that’s not bad. The first clear night – 2 days into 2025.

Having really enjoyed observing Hickson 92 back in November of last year, I have decided to add the Hickson Compact Group list to my observing programme.

Session Data

  • Date:  02/01/2025
  • Time:  22:13 – 02:20 UT
  • Seeing: I. Excellent
  • Transparency: IV. Poor with heavy haze
  • Temp: 2 C,
  • Air Pressure: 1026mb
  • Humidity: 79%
  • Dew Point: -2 C
  • Wind Speed: 4mph
  • Average SQM: 20.23 magn/arcsec^2

Scope: Altair 250mm RC f/8  Camera: ZWO ASI 183MM. Darks but no Flats

All images are displayed North to the Top and East to the Left.

M81, NGC3031

Located 10 degrees NW of Alpha UMa in Mrsa Major.

‘ve never imaged this such a long focal length. At 2000mm this galaxy is huge.

From the bright and elongated core, you can make out the first of the dark dust lanes to the SW about 2.5 arcmins out , curls all the way clockwise and exits the frame to the North. On this arm there is a concentration of star forming regions to the South

The second arm starts seems to start at the Southeast and again runs clockwise all the way north and curling round to the South where it peters out at the edge of the frame to the South. On this arm there is a concentration of star forming regions along the NE and NW sides of the arm

The third arm exits to the East and follows outside the second arm as it curls to the North then back to the South, where it looks like it joins back into the second arm.

I could have exposed for longer to see more, but this is EAA and not astrophotography.

Total Integration Time: 720 sec

HCG35

Located just over 4 degrees NEE of 31 Lyn in Lynx.

The Hickson 35 group is made up of 6 galaxies, I’ve listed these in North to South order. PGC24599, PGC24600, PGC24596, PGC24601, PGC24597 and PGC24598. All of these are clearly visible, although PGC24598 almost looks stellar.

However this image contains many more galaxies as annotated in the image above. I’ve set an 18 mag filter as I don’t see any other objects DSO’s fainter than this.

Total Integration Time: 525 sec

HCG31

Located about 1.5 degrees NW of Beta Eri in Eridanus.

This is a really tight grouping of 4 galaxies. The Hickson paper suggests the group spans only 0.9 arcmin, but if you look at the graphic marking the distribution, this spans nearer 2 arcmins.

The four galaxies from East to West are PGC16574, PGC16573, PGC 16571 and PGC16570. When you see the Hickson graphic, you can make our all four in the image. However without that graphic PGC16574 and PGC16573 could be confused as only being one galaxy doing something really weird.

PGC16571 just looks stellar, just like Gaia EDR3 3212843864799228672 46 arcsec to the Southeast of it.

PGC16570 looks to be edge on, but has a slight S twist to it.

PGC16574 Looks like it loops in a circle and joins up with PGC16573.

2.6 arcmin to the SE of HCG31 is PGC16592.

Total Integration Time: 540 sec

HCG37

Located 6 degrees NEE of Iota Cnc in Cancer.

HCG37 consists of 5 galaxies. From North to South, these are PGC26006, PGC26005, PGC26012, PGC26004 and PGC 26013

PGC26012 is an edge on Sb spiral and has that flat S shape. I can clearly see the core and the brighter bulge

PGC26013 looks to be face on with a diameter of 1.8arcmins. It’s also classified as NGC2783

The faintest of the five is PGC26006 at 16.3 mag

I can also make out two faint galaxies PGC1883496 and PGC1883653 about 3.5 arcmin to the SSE . These are 16.8 and 17.8 mag respectively.

Total Integration Time: 450 sec

HCG44

Located 2 degrees NNW of Gamma 2 Leo in Leo.

The group contains 4 galaxies…..and what belters they are. Starting in the NE corner and going to the SW, they are PGC30099, PGC30068, PGC30083 and PGC30059

PGC3009 is an elliptical at 11 mag.

Image Credit https://en.wikipedia.org/wiki/Galaxy_morphological_classification

PGC30068 is a contorted Spiral. It is classed as an SBc type ( barred) but from what I’ve read, this is more likely non barred spiral that has undergone massive tidal disturbances, where outer arms have be perturbed to form this distorted shape.

PGC30083 is hard to describe. I can see the bright nucleus illuminating the inner core. Being partially edge on, I can see the a dark dust lane that has a second branching of toward the East. The sides of the dust lane look like they are above and bow the plane of the disk making the galaxy look like a hamburger with a thick bun top and bottom with a very thin burger inside.

PGC30059 to the South is almost face on. It looks like a barred type ( Simbad confirms it as a SBa) with very tightly wound arms.

9.9 arcmin to the SW of PGC30083 is another galaxy PGC 86788 at 6.8mag and just going out the frame to the South east is PGC2806871 at 16.3 mag

At the centre of the frame is PGC1657032 at 19.9 mag, this being the faintest object in the frame that I can make out.

Total Integration Time: 450 sec

HCG46

Located 2 degrees NNE of Gamma 2 Leo in Leo.

This groups contains 4 galaxies. Starting from the NE going towards the SW they are PGC30354, PGC30349, PGC30350 and PGC30347. The Hickson position for this group is a way off by 3.4 arcmin to the SW of the location of the two central galaxies.

Total Integration Time: 435 sec

HCG41

Located just over 4 degrees NW of Lamda UMa

This groups contains 4 galaxies. Starting from East to West they are , PGC28784, PGC 28770, PGC28764 and PGC28753. All of these are almost edge on with PGC28764 being the brightest at 14.6 mag. The faintest is barely visible at 18.1 mag.

Just outside the official group is PGC28751, which if you were observing this visually, might mistake for being one of the group. I guess it’s always wise to check these things so you can correctly identify your observed constituents.

While there are lots of other galaxies in the frame, the only others that are obvious are PGC226229 17.5 mag 9.0 arcmin to the West and PGC2462170 17.7 mag 7.7 arcmin to the Southeast.

Total Integration Time: 525 sec