November 2025, Nikon Kenkyukai 1

November 2025, Nikon Kenkyukai 1

Shinjuku Tokyo

Autumn November

Saturday, November 15, 2025. A clear autumn sky. The Nikon Kenkyukai November regular meeting was held. I took a walk from the subway station to the venue.

Shinjuku West Exit

Hacchobori

Autumn Sky

Street Tree

Red Autumn Leaves

Autumn November

Presentation Session

The Tokyo Meeting started with a presentation session. This is the story of the discovery of a historical masterpiece of astronomical observation equipment, an important cultural property, in Japan.

JOICO Telescope

Astronomical Telescopes in the Early Days of Nippon Kogaku

Here is the PowerPoint content (PDF) :
Astronomical Telescopes in the Early Days of Nippon Kogaku

Reference handouts (PDF) :
History of the founding of Nippon Kogaku

JOICO 2-inch Telescope

A member of the Nikon Kenkyukai discovered a JOICO 2-inch telescope in Japan. This is an extremely rare cultural asset.

As you know, the product name is taken from the initials of the company's name, Nippon Kogaku K.K., which translated into English is the Japan Optical Industry Co.

Objective Lens

The Elegance of Japanese Crafts

We have considered the year of manufacture of the JOICO 2-inch telescope. The Nikon Kenkyukai estimates that it was manufactured between the end of the Taisho era (1925) and the early Showa era (around 1930).

51 mm Caliber (2 inches)

The objective lens has a diameter of 51 mm (2 inches) and a total length of 730 mm. The optical tube assembly is wrapped in brown leather, reminiscent of a work of art. This is a Keplerian type and uses a JOICO microscope objective lens (4X) as the erecting lens. If you actually look through the eyepiece, you will see an upright image. It seems that this telescope was set up as a ground-based telescope rather than for astronomical observation.

Remove the Eyepiece Parts

Eyepiece and Erecting Lens

In this state, it can be used as a high-quality magnifying glass similar to a simple microscope for magnified observation.

JOICO objective lens is used as an erecting lens

JOICO Objective Lens

JOICO 1240

JOICO B4 N. A. 0.1

The specifications from a product brochure from around 1925 are shown below.

No. 233 B 2-inch Telescope

Objective lens effective diameter: 50mm
Objective lens focal length: 500mm
Magnification: 55X for astronomical observation, 20X for terrestrial observation
Accessories: sunglasses, metal tripod, storage box
List price: 100 yen

Eyepieces (Huygens):
For astronomical observation
7mm (7.00 yen), 9mm (6.00 yen), 12.5mm (6.00 yen), 18mm (6.00 yen), 25mm (6.00yen)
For terrestrial observation
22mm

Nikon Shimbun

The next presentation is titled "Nikon Shimbun Research." The presenter is a member of the Nikon Kenkyukai and has been researching Nikon Shimbun. He has collected and carefully examined 47 months' worth of Nikon Shimbun from the 1960s to the 1980s.