Notes on the Flat Galaxies Program
When I first contemplated doing the Astro League’s Flat Galaxy program, I assumed that a number of the photos already on this website – from the Southern Arp Peculiar Galaxies or the Local Galaxy Group – would qualify as flat galaxies for of this program. Not so!
We view many galaxies “edge on,” as if we were looking roughly into the galaxy’s plane from its side. Flat galaxies, however, are a special class of edge on galaxies. The flat galaxy designation is given to a galaxy that is at least 40 arc-seconds in diameter with a major axis to minor axis ratio greater or equal to 7. Flat galaxies are not just generally elliptical, but really flat or needle-like. There are thousands of flat galaxies, and they are cataloged in the Revised Flat Galaxy Catalog.
I have pursued this program with the remote photographic option, using remote photo services from Sierrastars and Slooh. These services employ a number of telescopes, and I have used several of them for this project. Below each photo I note the scope with an abbreviation that follows this convention:
SSON – Warrumbungle in New South Wales, Austrailia = W
SSON – Gemini in Sonoita, Arizona, USA = G
SLOOH – Santiago, Chile = SC 1 or SC 2
SLOOH – Canary Islands = C 1 (a Plane Wave Instruments 20″ f/6.8 scope), C 2 (a Plane Wave Instruments 17″ f/6.8 scope), or C 3 (a Celestron 11″ RASA f/2.2 scope)
Most all of the photos taken for this program were Luminance exposures, usually of 50 seconds duration. The few RGB images used were 20 second exposures for the R, G, and B channels.
I also include a link to SIMBAD (the Set of Identifications, Measurements, and Bibliography for Astronomical Data) operated by the Centre de Données astronomiques de Strasbourg (CDS) that provides additional information about the object in question.
This program requires the observer to calculate the position angle of each target (a measurement that is also used in describing double stars). In the case of flat galaxies, imagine a compass rose (with North at the top and East to the left) with a photo of a flat galaxy precisely centered and superimposed onto the compass rose. The angle the flat galaxy strikes (in degrees), from the North-South axis to the eastern side of the compass, is the position angle. I used an online resource, the NASA / IPAC Extragalactic Database to find the angles. (The Position Angles are located on the “Diameters” tab on the NASA / IPAC website.)