This auction is for a 1988 Celestron (Vixen of Japan) .965-inch 45-degree prism diagonal (Erect Image Diagonal). It will come with its original setscrew, original (V) bottom and top dust caps, and the now hard to find original box-with-label.

Though the complete model name for this unit is "45 Degrees Erect Image Diagonal .96"", I will simply refer to it as a 45 degree diagonal.

Like its .965-inch to 1.25-inch hybrid prism relative, which was marketed at the same time, the .965-inch 45 degree prism diagonal arrived in (2) generations; the earliest models coming from Vixen of Japan and later on the Synta Technology Corp of Taiwan models, which were offered in the catalogs and sometimes as inclusive equipment up until late 2000. Materials makeup and prism size and coatings were completely unchanged and performance and even weight are unchanged. This one here is a 1st generation example.  

The only differences between the (2) generations of the 45 degree diagonal are:  1) The set screw is fancier on the Taiwanese model and instead of being a nickel plated steel set screw, which can rust and pit, is a milled brass-with-anodized aluminum grip, which cannot rust. 2) The "JAPAN" etching on the chrome barrel is absent and no etching appears. Its source is remarked on the box and on the underside diagonal access cover. 

It should be noted, which few will ever notice, there are (2) variants of the Japanese-made 45 degree diagonals of this size. The earlier units have "JAPAN" etched on the chrome barrel. In their last years before being sourced from Taiwan, "JAPAN" is now painted in white characters on the underside prism panel.

The Vixen-made 45 degree diagonals were under mpn 94111 up until very early 1994. From 1995 until production of this diagonal ceased with Taiwan in 2002, it was then under mpn 94111-A.

These diagonals are rare (both Japan and Taiwan) in comparison to the .965-inch to 1.25-inch hybrid 45 degree diagonals because they were ONLY EVER offered on the Standard C90 as inclusive equipment since its black gloss models appeared in 1985 (possibly December of 1984). No other telescope came with them; not even the C90 Rubberized (Rubber Armored) as those were the top-grade models and came with the hybrid 45 degree diagonal. 

The .965-inch 45 degree diagonal was indeed marketed in the accessory and general catalogs for individual purchase, BUT in many of their telescope catalogs, Celestron did not increase exposure by offering the 45 diagonal as optional upgrade accessories. So sales, and in turn, acquired examples, are very low nowadays. 

Barrel size:  .965-inches

Accepts:  .965-inch eyepieces and barlows

Design:  45-degree prism

Optics:  fully coated

Image orientation:  correct upright

Clear aperture:  22.7mm

Materials:  milled brass and aluminum, polyurethane, glass

Weight:  2.8 ounces

These "Erect Image" diagonals can be a MAJOR upgrade for telescopes like the newer Firstscope 60E, Jason 313 and 454 Discoverer, Meade 291 and 300 refractors, the Tasco 13T, 7TE, and 10TE, and with other small refractors in the 60mm to 80mm aperture range coming from vintage (and antique) brands names like Towa, Gakken, Wetzlar, Penncrest, Selsi, Mayflower, Lafayette, Swift, Carton, and Idai to name a very few. This diagonal uses the exact same size prism and aperture opening as its hybrid relative and has a LARGE, non-aperture stopped exit. This means that your refractor will not show vignetting problems at the eyepiece if its focal ratio is short (f/7 to f/5).

A 45-degree prism diagonal is fantastic for terrestrial viewing as it will make all images appear correct; upright and matching orientation. The "STOP" sign will be seen as "STOP". This also means when you are viewing in your cassegrain or refractor, because the images are not reversed, you can easily flow your target. If you are following birds, boats, deer, cars, planes, ect, in the eyepiece with this diagonal, they will move in the same direction as you are moving the telescope; giving a real feel of orientation.

To a degree, this can be used in astronomy applications as well. I like to use one on the Moon as it can seem more familiar in zoomed-in appearance rather than the typical backwards format I would see in my 90 degree diagonals. The only drawback with using a 45 degree diagonal is after about halfway to the zenith (overhead position), you will be set at an awkward angle for your neck.

It should be noted also that using a 45-degree prism diagonal will require an additional 0.63-inches (16mm) outward focus travel. This is not an issue for maksutov and schmidt cassegrains, but it can be an issue for stubby refractors. Rich field refractors in the f/4 to f/5.9 range may have a limited amount of focus travel ability and incorporating this Erect Image Diagonal may require an additional extender tube to reach true focus at the eyepiece. 

In long refractors like the Celestron C80 and C102, Meade model 395 and 295, Takahashi FC50, and other refractors in the 60mm to 120mm aperture range at f/8.8 to f/16 do not seem to have focus travel issues with this diagonal.

This auction ad was completely, organically written by Veradale Mobile Observatory, not an A.I. software device; an actual honest-to-goodness, real human with over 20 years experience with now over 1000 telescopes made from today and all the way back to 1948.

Packed with great care.