On September 1st, 2005, I took delivery of a Showa 4" Apo refractor. After looking for one for quite some time, I was pleased that the search was finally over.

If you are not familiar with Showa refractors, you are not alone. They are rarely seen in these parts and few US amateurs know of them. However, they are made by Showa Industry Co. LTD., a highly respected maker of observatory-class telescopes in Japan and enjoy an excellent reputation in that country. Showa Industry was founded in 1966. My "new" 4-incher was built in 1991. The lens was figured by ex-Takahashi Master optician Mr. Hidaka. Here are my initial impressions:

OTA:

The optical tube is built like a tank, weighing over 13 lbs. The dew shield is non-retractable and is screwed on to the OTA. The interior of the OTA is fully baffled and a rough flat-black coating is applied. The original focuser is not standard; the same as my Pentax scope, and therefore requires specialized adapters in order to use standard eyepiece sizes. To make the scope more user friendly, the focuser was removed and the "tale end" was modified by APM with a quality draw tube and a Starlight Instrument's "Feather Touch" focuser. Focusing is now accomplished by sliding the draw tube to reach approximate focus; then fine tuning with the "Feather Touch". This arrangement is something I am very accustomed to; my Zeiss refractor is set up in the same way (shown here for comparison). The draw tube is usually only moved once or twice during an observing session and the focuser does the rest. Needless to say, all my eyepieces can be brought to focus. (APM tells me that this arrangement also provides enough in-focus to allow the use of a binoviewer without needing a barlow). Mr. Mathias' work is excellent and the operation of both the draw tube and focuser are very smooth.

Glass:

The lens is a 100mm, air-spaced apochromatic doublet made of SD (Super ED) glass. The focal length is 1000mm (f/10). The lens is coated on all surfaces, and when looking down the tube, the glass disappears. The lens screws onto the OTA, unscrewing the lens provides complete access to the interior of the scope. The lens cell is permanently collimated with no adjustment. I checked collimation with both a laser and star test and it was accurate.

Mounting:

The scope came with two nice 4" tube-clamps for mounting. However, the OTA also has two "feet" and these proved to come in handy. Both my Zeiss refractors are mounted using dovetails attached to the tube which slide into dovetail clamps on my mounts. I decided to keep things consistent and fabricated a dovetail to span the feet on the Showa. It makes for a secure attachment to the mount, with less chance of marring the tube. I mounted the Showa on my Losmandy G9 mount. This mount handles my Zeiss 4" OTA with ease and that scope weighs 4 lbs. more than the Showa.

First light (for me):

I chose a 2nd magnitude star (gamma Draconis) and checked the collimation again at 150X. Seeing was pretty good and the resulting diffraction image was excellent, rivaling my Zeiss; the out-of- focus pattern appeared the same in both directions. I could not detect any color in either the focused or out-of-focus image. I swung the scope over to Vega for a more stringent "color" test. Here I saw no color in the focused image and only after swinging back and forth to each side of focus several times could I convince myself that there was a slight tint in the out-of-focus image. Here is where the Showa bettered my Zeiss semi-apo which shows a small amount of color on bright objects. The lessoning of chromatic aberration seen in the Apo was just what I was looking for in a planetary refractor.

While here, I also checked for light scatter by moving Vega in and out of the field of view. The background sky remained black with only a tiny trace of light scatter seen when the star was at the very edge of the field (the moon was unavailable for a more severe test). I also looked for any telltale evidence of reflection off the interior surfaces of the OTA and could see none.

Convinced that I had a "keeper" and with no dew in sight, I attached TEC turret, filled it with TV plossls and went on a tour of familiar objects. Albireo, Gamma Delphinius and Zeta Aquarii were all stops, with the first two showing rich, clean, contrasting colors and the latter being split into two white "headlights" at just 100X. All displayed a clean airy disc and beautiful diffraction rings that is the trademark of a quality refractor. Next was Epsilon Lyrae, which I was able to split into four components at just 76X.

No planets of interest were in sight, so a few deep sky objects were visited - M13, M27, M11 & M8. All were lovely in the 4", showing reasonable detail for this aperture. I had one last target in mind, but that would have to wait until morning.

Early the next morning (yes it actually stayed clear for a whole night); I set the scope out for an hour cool-down. At about 5:00 AM, I was able to view Mars high overhead. I had checked "Mars Previewer II" earlier to identify albedo features and realized that a relatively featureless side of Mars was available at the time, but I was not expecting too much visually anyway, with the Martian disk being only 14 arc-seconds across and the objective being only 4 inches. I was pleasantly surprised. The color of the disk was natural in appearance and at 200X the image was very steady; revealing the South Polar Cap and some albedo features (Mares Sirenum & Cimmerium). I then inserted my Sirius VFS filter and at different settings subtle improvements in these features were seen. With these promising results, I can hardly wait until the disk reaches 18 arc-seconds when the prime observing window opens in early October!

Conclusion:

The reason I obtained this scope was to have a quality planetary refractor. With planets as the target, my primary concern was having a scope that would provide a view with excellent sharpness, contrast and color correction. A second desire was for a long-focal-length instrument, which would allow for higher powers without the use of barlows. The Showa satisfied both "wants".

Overall I am very pleased with my new acquisition. It has met or even exceeded my expectations and this sample holds up well to the reputation these scopes enjoy. Though I have looked through many Apo's, this is the first I have owned and judging from these first impressions, I look forward to many more observing sessions.