NOTES
The Arp Catalog(s) of Peculiar Galaxies
Halton Arp (1927 – 2013) was an American astronomer best known for his Atlas of Peculiar Galaxies, which was published in 1966. Though he made many contributions to astronomy, he was particularly interested in how galaxies change over time. His Atlas cataloged some 338 “peculiar” galaxies that were oddly shaped or colliding galaxies that looked unusual for one reason or another. You can learn more about Arp here and here. Arp’s original catalog is the subject of the Astronomical League’s Arp Peculiar Galaxy (Northern) Observing Program.
In 1987 Arp and collaborators Barry Madore and William Roberto published a “southern hemisphere version” of his Atlas, entitled A Catalogue of Southern Peculiar Galaxies and Associations. Items in the Catalogue are classified with reference to Arp and Madore’s surnames, such as AM 1322-424, which is also cataloged as NGC 5128. The Arp and Madore southern collection of galaxies is the subject of the Astronomical League’s Arp Peculiar Galaxy (Southern) Observing Program.
Arp organized his first catalog (the Northern Arps) into four major sections : Spiral Galaxies, Elliptical and Elliptical-like Galaxies, Amorphous Galaxies, and Double and Multiple Galaxies. Across these sections, he developed thirty nine sub-categories that broke down the sections further. The sections and sub-sections are reflected in my photo log.
A friend gave me two great resources and one challenge at the outset of the program. First, she steered me to a really informative article on the Northern Arps on Wikipedia. You can find it here. Second, she recommended a printed book called The Arp Atlas of Peculiar Galaxies, A Chronicle and Observer’s Guide, by Jeff Kanipe and Dennis Webb (Willmann-Bell, 2006-2019), which is a terrific resource on the Northern Arps. Her challenge was this: Photograph at least one Arp object from each of the thirty-nine sub-sections. Working with the categories in this manner has greatly helped me understand how Arp was thinking as he put together his catalog. Alas, photos from one of the categories eluded me (Category 5 – One-armed spiral galaxies, featuring Arps 22, 23, and 24). Each of the photos is captioned using the following protocol: Scope Used / Exposure and Filter Data / Date of Exposure / Time of Exposure (all UTC).
Scopes and Cameras
I have pursued this program with the remote photographic option using remote photo services from SSON and Slooh.
SSON has two observatories. They are located at the University of Iowa Observatory in Sonoita, Arizona (Latitude: 31° 39′ 56.08″ North / Longitude: 110° 36′ 06.42″ West) and the the Warrumbungle Observatory in New South Wales, Australia (Latitude: 31° 39′ 56.08″ North / Longitude: 110° 36′ 06.42″ West). I routinely ordered a single 60 or 90 second Luminance exposure from the SSON scopes.
Gemini
Scope: 20-inch F/6.8 PlaneWave CDK20 at f/6.8
Camera: Apogee CG42
Warrumbungle
Scope: 20-inch PlaneWave CDK at f/6.8
Camera: SBIG STL6303E
Slooh operates a number of telescopes around the world and I have used several of them for this project. The Slooh locations are in Santiago, Chile (Latitude: S33° 16′ 8.4″ S33.269 / Longitude: W070° 32′ 2.4″ W070.534) and the Canary Islands (Latitude: N28° 17′ 58.92″ N28.29970 / Longitude: W016° 30′ 29.736″ W016.50826). Each location has several scopes installed.
Chile 1
Scope: Celestron 14″ EdgeHD 1400 Schmidt-Cassegrain Catadioptric (SCT) at f/11
Camera: Diffraction Limited SBIG, Model STL-11000
Chile 2
Scope: PlaneWave Instruments 17″ CDK17 (Corrected Dall-Kirkham) at f/6.8
Camera: Finger Lakes Instrument Proline PL16803 Monochrome CCD Camera
Canary 1
Scope: PlaneWave Instruments20″ CDK20 (Corrected Dall-Kirkham) at f/6.8
Camera: Finger Lake Instruments PL09000
Canary 2
Scope: PlaneWave Instruments 17″ CDK17 (Corrected Dall-Kirkham) at f/6.8
Camera: Finger Lake Instruments PL16803
Canary 3
Scope: Celestron 11″ Rowe-Ackermann Schmidt Astrograph (RASA) at f/2.2
Camera: Celestron Nightscape 8300 One Shot Color (OSC)
Canary 4
Scope: Celestron 14″ EdgeHD 1400 Schmidt-Cassegrain Catadioptric (SCT) at f/11
Camera: Diffraction Limited SBIG STT-8300M
Slooh telescopes and cameras operate on fixed filter / exposure formulas based on the type of target in question. Sometimes they take luminance-only shots and at other times they take separate L,R,G, and B photos. I used a variety of integration techniques for the photos in this program. In general, if the photo has any color in it, it is RGB or LRGB. If it is monochrome, it is a luminance shot. In some cases I found it best to turn a color photo into a mono photo in order to bring out the contrast between dark space and the objects in the field of view. In all cases, Slooh returns Luminance shots with 50 second exposures and R, G, and B shots with 20 second exposures.
Photo Quality
While I am quite happy with the photos I have used in this program, it is perhaps worth noting that they are not Astrobin quality “pretty pictures.” The scopes and cameras used to produced the photos are of very high quality. But the chief limiting factors have to do with length of exposure (these are very short exposures as astro photos go), the ability to manipulate filters (there is some choice in SSON cameras, but none in Slooh Cameras), and image calibration (SSON and Slooh control all of that). When I first began remote astrophotography I wanted to see what could be done in 60 or 90 seconds. As it turns out, one can get quite a bit of detail in brief exposures.
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