In October 2010, I ordered an Astro Systeme Austria (ASA) N12 Corrected Newtonian from Oceanside Photo & Telescope (OPT). This 12" telescope has a fast focal ratio of f/3.6 and a large flat field that is optimized for astrophotography.
The decision to purchase this instrument was based on the experience I had with the Takahashi Epsilon 180 Hyperbolic Astrograph and the desire for a fast telescope with a longer focal length. The Tak E180 has an aperture of 180 mm (7.1"), a focal length of 500 mm, and an f/ratio of 2.8. In comparison, the ASA N12 has an aperture of 305 mm (12.0"), a focal length of 1080 mm, and an f/ratio of 3.6. So the ASA has just over twice the focal length and nearly as fast as the Tak E180.
I was also influenced by the excellent images that my ASV neighbor David Churchill was obtaining with an ASA N16 astrograph. My choice of the smaller ASA N12 was driven by the need to simultaneously mount the ASA, the Tak E180 and the Astro-Physics 130mm EDF Refractor all on the Astro-Physics 1200GTO German Equatorial Mount. This mount is rated to carry approximately 140 lb. (63.6kg) of equipment making the above configuration possible using the MultiScope32 dovetail bar from Robin Casady Astro Accessories.
Although the delivery time of the ASA N12 was advertised as "3-4 months", a problem with ASA's optics production resulted in a 9-month wait with delivery occurring in late June 2011. This unfortunate timing meant that the ASA N12 arrived just as Arizona's summer monsoon season began. This gave me time to master the use of Jim Fly's CATSEYE Collimation Tools. The accurate collimation of the optics in fast Newtonians like the N12 is critical in optimal performance and the CATSEYE Tools were perfect for this task.
With the optics collimated and the ASA N12 mounted on the AP 1200GTO, it was now a waiting game for the weather to break. I only enjoyed one night with an hour or two of clear sky to focus the ASA and shoot a few test frames. Things were looking very promising but I now had to return to the East Coast for several months beginning mid-August. I guess I'll just have to be patient a few more months until I return in the autumn!
|Astro Systeme Austria (ASA) N12 Corrected Newtonian Astrograph|
|Primary Mirror:||305mm (12.01")|
|Secondary Mirror:||120mm (4.72")|
|Focal Length:||1080mm (42.52") - with 3" Wynne Corrector|
|Focal Ratio:||f/3.54 - with 3" Wynne Corrector|
|T Ratio:||f/3.9 - with 3" Wynne Correcter|
|Resolution:||0.46 arc seconds|
|Tube Assembly:||high-grade carbon fibre, black velvet interior|
|Tube Dimensions:||Length - 990mm (39.0"); Diameter - 360mm (14.2")|
|Weight:||18 kg (39.7 lbs.)|
|Image Circle:||50 mm (1.97")|
|Field of View (35mm):||1.3 x 1.9 degrees @ f3.6|
|Field of View (DX):||0.8 x 1.2 degrees @ f3.6|
The ASA website has more information about the N-Series Astrographs.