Hemisphere:  Northern  ·  Constellation: Canes Venatici (CVn)
Getting plate-solving status, please wait...
Arp 36 (with Arp 183), 


            Gary Imm
Arp 36 (with Arp 183), 


            Gary Imm

Arp 36 (with Arp 183)

Getting plate-solving status, please wait...
Arp 36 (with Arp 183), 


            Gary Imm
Arp 36 (with Arp 183), 


            Gary Imm

Arp 36 (with Arp 183)

Imaging telescopes or lenses: Celestron EdgeHD 11

Imaging cameras: ZWO ASI 294 MM Pro

Mounts: Astro-Physics Mach1GTO

Guiding cameras: ZWO ASI 174 MM Mini

Software: Main Sequence Software Sequence Generator Pro  ·  Pixinsight  ·  Stark Labs PHD2 2.6.3

Filters: Astrodon Green 31mm Gen2 I-Series  ·  Astrodon Blue 31mm Gen2 I-Series  ·  Astrodon Lum 31mm Gen2 I-Series  ·  Astrodon Red 31mm Gen2 I-Series

Accessory: Celestron OAG  ·  ZWO EFW 2″X7  ·  MoonLite Focuser for EdgeHD 11

Dates:Feb. 21, 2021Feb. 22, 2021

Astrodon Blue 31mm Gen2 I-Series: 30x120" (1h) (gain: 120.00) -20C bin 2x2
Astrodon Green 31mm Gen2 I-Series: 30x120" (1h) (gain: 120.00) -20C bin 2x2
Astrodon Lum 31mm Gen2 I-Series: 60x120" (2h) (gain: 120.00) -20C bin 2x2
Astrodon Red 31mm Gen2 I-Series: 30x120" (1h) (gain: 120.00) -20C bin 2x2

Integration: 5h

Avg. Moon age: 9.39 days

Avg. Moon phase: 70.63%

Astrometry.net job: 4266237

RA center: 13h 34' 34"

DEC center: +31° 25' 0"

Pixel scale: 0.343 arcsec/pixel

Orientation: -2.788 degrees

Field radius: 0.226 degrees

Resolution: 3959x2614

Locations: Backyard (Mag 20.8 - Bortle 4.5), Onalaska, Texas, United States

Data source: Backyard


This image captures a pair of Arp objects located in the constellation of Canes Venatici at a declination of +31 degrees. Both of these are Astrobin Debut Objects.

Each Arp object is located about 225 million light years away. They are likely to be interacting with each other. Arp 36 (magnitude 15.0) is located at upper right and Arp 183 (magnitude 14.4) is at lower left. Each galaxy is similar is size, spanning 1.4 arc-minutes in our apparent view and having a diameter of 90,000 light years.

Arp 36 was classified by Dr. Arp into the category of Spiral Galaxies – Integral Sign. This is an interesting category, in that it does NOT include the classic edge-on integral sign galaxy, UGC 3697. Instead, the 6 Arp "integral sign" galaxies (Arp 31-36) are less dramatic but amazingly consistent. All are face-on grand spiral galaxies with 2 strong arms. In all 6 cases, ,these arms appear as a symmetric, stretched-out “S” shape where the arms have unwound a bit. Within the arms are many star clusters, making the arms look lumpy. The galaxy cores are poorly defined.

Since all of the galaxies in this category have similar characteristics, it would make sense that they are the result of the same dynamic processes. But those processes are a mystery at this time. To me, the shapes seem reminiscent of objects like Arp 244 (Antennae Galaxies) which are obviously the result of 2 spiral galaxies merging. Such a merger would also initiate star formation, leading to the lumpy look, as well as messing up both cores. So it seems logical that the galaxies of this Arp category are merging galaxies which are towards the end of their merger, such that they appear to look more like one galaxy at this time.

One strange aspect of this object is that a star cluster below and left of the core, about 1/3 of the way along the lower arm, appears to have a green tint. I can’t explain that.

Arp 183 is also interesting. For more information on that object, please see my dedicated post on it here.

Although the Arp objects take center stage here, I like the numerous background galaxies just as much. There are a number of interesting galaxy cluster patterns here. The “<” pattern of distant galaxies in the middle of the image is my favorite. I also like the galaxy groupings above and right of center. These galaxies look to be about 2 billion light years away.