Hemisphere:  Northern  ·  Constellation: Pisces (Psc)  ·  Contains:  IC 1685  ·  IC 1687  ·  IC 1688  ·  IC 1689  ·  IC 1690  ·  IC1685  ·  IC1687  ·  IC1689  ·  IC1690  ·  NGC 494  ·  NGC 504  ·  NGC 507  ·  NGC 508  ·  NGC494  ·  NGC504  ·  NGC507  ·  NGC508  ·  PGC169774  ·  PGC5100
Getting plate-solving status, please wait...
Arp 229, 


            Gary Imm
Arp 229, 


            Gary Imm

Arp 229

Getting plate-solving status, please wait...
Arp 229, 


            Gary Imm
Arp 229, 


            Gary Imm

Arp 229

Imaging telescopes or lenses: Celestron EdgeHD 11

Imaging cameras: ZWO ASI 1600MM Cooled 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:Oct. 14, 2020Oct. 15, 2020

Astrodon Blue 31mm Gen2 I-Series: 30x120" (1h) (gain: 139.00) -20C bin 1x1
Astrodon Green 31mm Gen2 I-Series: 30x120" (1h) (gain: 139.00) -20C
Astrodon Lum 31mm Gen2 I-Series: 60x120" (2h) (gain: 139.00) -20C bin 1x1
Astrodon Red 31mm Gen2 I-Series: 30x120" (1h) (gain: 139.00) -20C bin 1x1

Integration: 5h

Avg. Moon age: 27.41 days

Avg. Moon phase: 5.33%

Astrometry.net job: 4110488

RA center: 1h 23' 30"

DEC center: +33° 9' 35"

Pixel scale: 0.281 arcsec/pixel

Orientation: -4.549 degrees

Field radius: 0.199 degrees

Resolution: 3912x3273

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

Data source: Backyard


This object consists of a pair of elliptical galaxies at the top left of the image. The large elliptical is the magnitude 12 NGC 507 and the smaller one above is the magnitude 14 NGC 508. They are located 210 million light years away in the constellation of Pisces at a declination of +33 degrees. I did not center them in the image because of the bright 9th magnitude star HD 8347, just off the top right of the image, which created quite a distraction. Its glow is still seen at top right.

NGC 507 spans 5 arc-minutes in our apparent view, which corresponds to a huge actual diameter of 280,000 light years. Dr. Arp categorized this object in the category of Galaxies with Concentric Rings. Looking closely, you can see the “ring” which Arp identified. These tend to be called shells now and not rings. I was careful to try not to overprocess this object and create artifacts that would affect the shell.

Roughly 10 percent of ellipticals have these shells, which were first discovered fairly recently in 1980. I don't fully understand the "shell" mechanism - my thought would be that the stars should have a constant light/density gradient away from the galaxy core, but they don't. The shells remind me a bit of mid-region galaxy rings, so perhaps it is a similar mechanism - gravitational interaction with another galaxy causes waves of material to compress and spread outward, initiating star formation.

This object is part of a galaxy group, naturally known as the NGC 507 group. All of the galaxies in this image are members of this group. It is an interesting assortment of galaxies! The highlights include the polar ring galaxy IC 1689 at bottom left, the warped edge-on spiral galaxy NGC 504 just above image center, the odd IC 1685 to the right of center, and the beautiful grand spiral ring galaxy NGC 494 near the right edge.