There seems to be a dearth of information about early AP refractors. Thomas Back’s essay provides a one sentence summary of some of these scopes that may be incomplete, and occasionally inaccurate. I know that the staff at AP will eventually put together a history of these scopes, but they are quite busy with their current equipment.
John Volk, who lives near me is a friend who has a collection of beautiful vintage AP scopes. I have looked through a 5” f/12 (wonderful images of the Moon and planets), 6” f/9 Starfire (only deep sky so far) and a 5” f/6. The 5” f/6 scope is only described in Back’s essay as “the least well corrected scope AP has ever produced.” While that may be technically true, we need to remember that TMB was a planetary fanatic and judged everything on that basis. The scope is advertised as a “Wide Field Refractor”, and true to its name it provides beautiful deep sky images. John, Daniel Mounsey and I used eyepieces including a Leitz 30mm, Nagler 17mm, and Nagler 9mm, and even from Los Angeles, we had beautiful views of the M31, the Double Cluster and Stock 2. There was some false color on Aldebaran and especially Vega, but not bad for such a fast pre-ED refractor. The Double Double had a beautiful split that looked appropriate for its aperture. 5th and 6th magnitude stars aren’t sensitive to the chromatic aberration and spherochromatism that was present on the star test. Using a green filter, the star test cleaned up quite nicely.
I have abstracted, edited, and summarized a small portion of the information from a Company 7 newsletter about AP scopes from 1987 in a table below. There are some interesting tidbits of information. First, there were indeed photo versions and visual versions of some scopes, and the visual versions have violet color whereas the photo versions have a crimson halo. This runs counter to the argument espoused on by some that the planetary performance of a refractor (other than a classic achromat) is always related to the amount of purple present. Second, there were some very cool prototypes, including a 7” f/15, 8” f/13.3 Apo (don’t know what AS means), and a pre-1987 10” f/14 with trispace corrector that was supplanted with a newer design, most likely with Starfire glasses. Finally, the optics in the 2” 2x Barlows were “hand corrected to insure no aberrations are introduced into the system.” Try finding a hand-made barlow today!
I am attaching some photos of the scope. While it is far from the CNC fit and finish of modern AP scopes and lacks a two speed focuser, it is quite charming and usable as is. Some people have criticized early AP scopes for having cork spacers that sometimes require replacement, but the four scopes I have seen that are reaching 30 years of age are still going strong without evidence of misalignment.
If one of these comes up, instead of parroting Thomas Back, we should refer to it as a classic wide field refractor that was advertised as such and performs admirably for its intended purpose.
1987 Astro-Physics Scopes in C7 Newsletter (* = Prototype)
Low Power Wide-Field Refractor
Sec. Spectrum (Red-Blue) < +/- 0.008% C-F
4” f/6 FL 610mm Wt 7# Discontinued; Visual/photo versions
5” f/6 FL 762mm Wt 12# Discontinued; Visual/photo versions
High Resolution Portable Refractor
Sec. Spectrum (Red-Blue) < +/- 0.008% C-F
4” f/10 FL 1016mm Wt 8# Discontinued
5” f/8 FL 1016mm Wt 13# Visual/photo versions
6” f/8 FL 1219mm Wt 19# Visual/photo versions
Super Planetary Portable Refractor
Sec. Spectrum (Deep Red-Blue) < +/- 0.004% C-F
5” f/12 FL 1524mm Wt 14# Discontinued
6” f/12 FL 1829mm Wt 21#
6” f/12F* FL 1219mm Folded
6” f/15* FL 2286mm
Starfire Photo-Visual Refractor
Sec. Spectrum (Deep Red-Violet) < +/- 0.025% C-G
4” f/8 FL 813mm Wt 8#
5” f/8 FL 1016mm Wt 14#
5.6” f/7 FL 996mm Wt 19# Discontinued
6” f/9 FL 1372mm Wt 21#
7” f/9 FL 1600mm Wt 34#
7” f/15* FL 2667mm
Sec. Spectrum (Deep Red-Blue) < +/- 0.008% C-F except as noted
6.8” f/15* FL 2590mm
6” f/9 NASA FL 1372mm Wt 20#
8” f/13.3 AS* FL 2682mm Wt 58#
10” f/14 Apo FL 3556mm Wt 185# Sec Spec <0.003% C-F
10” f/14 Tri FL 3556mm Wt 175# Tri-Spaced, Discontinued
Visual/Photo refractors are available in Photo (crimson halo) or Visual (slight violet) corrected
Edited by Derek Wong, 01 October 2016 - 11:47 AM.