Arp Peculiar Galaxy (Northern) Observing Program

Peculiar Galaxy (Northern) Observing Program Coordinator:

Marie Lott
2836 Rangewood Ter NE
Atlanta GA 30345-1581
(404) 941-5688



“When looked at closely enough, every galaxy is peculiar” – Halton Arp

This Astronomical League Observing Program is based on the 338 objects found in the Arp Catalog of Peculiar Galaxies. One hundred of the 338 Arp galaxies must be observed or imaged to qualify for the Program’s certificate and pin (if a pin was not already given for the completion of the Southern Arp Observing Program). Please remember, though, before you start this program, that it was developed for advanced amateurs, and may not be suitable for beginners. For observers and astrophotographers, a majority of the 338 galaxies fall in the 12th to 18th magnitude range. However, there are over 100 Arp objects below magnitude 13.5.

We feel that this Observing Program will challenge even the most serious of amateur astronomers. We sincerely hope that you find it rewarding and we look forward to seeing your images and observations.

Background Information

Halton C. Arp:

Halton C. Arp was one of the key actors in the contemporary debate on the origin and evolution of galaxies in the universe. His landmark compilation of peculiar galaxies, the Atlas of Peculiar Galaxies, led him to challenge the fundamental assumption of modern cosmology, that redshift is a uniform indicator of distance. 

List of Objects:

The list is provided in Arp Catalog number order. Because of the size of the catalog (338 objects), only a limited amount of information can be provided. In addition to the Arp number, you are given additional catalog names that the object is known under, and the Right Ascension and Declination of each object (Epoch 2000). For more information, we recommend a good catalog such as the “Deep Sky Field Guide to the Uranometria 2000.0” published by Willmann-Bell, Inc., or a computer catalog (I used The Arizona Database V. 8.0). Finally, for those of you that like to do constellation hopping or would like to plan your program around what is visible in the sky at certain times of the year, we have provided the Arp Peculiar Galaxy Catalog by constellation. I wish all of you the best of luck in this Observing Program.

Requirements and Rules

This certification is available to members of the Astronomical League, either through their local astronomical society or as members at large.  If you are not a member and would like to become one, check with your local astronomical society, search for a local society on the Astronomical League Website, or join as a Member-at-Large .

To qualify for the Northern Arp Peculiar Galaxy Program Certificate, image or observe 100 of the 338 objects in the Arp Peculiar Galaxy Catalog. You may select any 100 objects that you want to image or observe. Since many of the Arp objects are multiple galaxies, only the brightest member of the group needs to be imaged or observed, but it would be preferred if you could image or observe the entire group.  When making observations or taking images of multiple galaxies, the required tally of 100 should be made by the Arp number, not by the number of galaxies.  For locating the Arp galaxies, it is recommended that you use a good star atlas such as the “Uranometria 2000.0”, Volumes I & II published by Willmann-Bell, Inc., Sky & Telescope’s Millennium Star Atlas, or a good computer atlas.

Since this is an advanced observing program for light buckets, it is recommended that you use a telescope with an aperture of 12.5 inches or larger, and observe from a dark sky site. To record your observations, you may use log sheets similar to those found in the back of the Astronomical League’s manual Observe: A Guide to the Messier Objects. You can order this observing manual through Astronomical League Sales. If you use your own log sheets, they should include the object name, date and time, power, seeing and transparency, type of instrument, your latitude and longitude, and observing notes.

Submitting for Certification

  • The log sheets with visual observations or digital images (which should be submitted on a CD-ROM or via URL if images are posted online) should be sent to the Northern Arp Observing Program Coordinator.
  • Include your name, mailing address, phone number, email address, and club affiliation.
  • You may also have them reviewed and approved by an officer of your local astronomy club who should then send an email to the Northern Arp Observing Program Coordinator.
  • If you have already received a pin and certificate for the Southern Arp, you will receive just a certificate for the Northern Arp, as only one pin is awarded.
Each certificate will be numbered and lettered according to how it was acquired, either through CCD imaging, observation, or astrophotography.
Upon verification of your submission and of your active membership in the Astronomical League, your recognition (certificate, pin, etc.) will be sent to you or to the awards coordinator for your society, as you specified.  Your name will also appear in an upcoming issue of the Reflector magazine and in the Astronomical League’s online database.  Congratulations.  Good luck with your next observing challenge.

Arp Peculiar Galaxy Observing Program Coordinator:

Marie Lott
2836 Rangewood Ter NE
Atlanta, GA 30345-1581
(404) 941-5688



I and the Astronomical League wish to gratefully acknowledge Dennis Webb of the Johnson Space Center Astronomical Society for his suggestion to create this program, and for the wonderful work that he has put into investigating the list of objects as reflected in this Observing Program.

– John Wagoner


Northern Arp Observing Program Object Lists:

Other Northern Arp Observing Program Links:


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