46 cm (18") homemade reflector      Updated on July 23, 2017

Old version updated in 2015 is here
Original version updated in 2008 is here 

Multifinctinal ladder
Setting up
Primary & Secondary mirror

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The whole view
Aperture 18" (459 mm, Effective aperture: 455 mm), F 4.5, f: 80.2" (2037 mm). The secondary mirror is 3.1" (79 mm) with 17 mm thick. The optics have recoated in June 2015 by Galaxy Optics, Colorado, USA. The reflectivity of the primary and the secondary are 96% and 97%, respectively.
A wood bar suspending from the top ring is used to move the telescope downward: I grab it and pull down when I sweep the sky vertically. The light shroud was renewed in 2010: the present shroud was made by AstroSystems, Colorado, USA. The light shield is attached over the eyepiece.
Major modification in 2016 and after
* The Pahse 4 Focuser (AstroSystems) was replaced with the Feather Touch Focuser.
* Installing the filter slider: The Astrocrumb FilterSlide Mark II
* The connection method between truss poles and the top ring (secondary cage) was changed from the wooden wedge & pole seat to the crushed-tube method.

Left: Finders and focuser
Two finders, the Telrad and the 50 mm erect finders, are installed. At the beginning in 2001 I employed the Telrad but it was bulky and I chaged to piggyback ride Regal Quick-Finder on the 50 mm finder. I go t back to the Telrad as it is easier to use.
The eyepiece, I usually use for comet hunting, is Ethos 21 mm with 97x and 1.0
˚ actual field of view (FOV). A light shield is placed over a white plastic part on the eyepiece. Another eyepiece that I use is Planocular 30 mm, manufactured in Germany with 88˚ apparent FOV, which is combined with Parracor with 78x and 1.1 ˚ apparent FOV. Once I used Planocular 30 mm alone with 68x and 1.3 ˚ actual FOV.
I replaced the focuser, the Phase 4 Focuser (AstroSystems), with the Feather Touch Focuser in 2016 because the Phase 4 was broken.
Right: The dew caps and light shield
The dew shield made by insulator for water supply pipe (white colored) is placed on the Telrad Finder and the eyepiece of the 50 mm finder. Only when I peer into finders I remove the dew shields.
A long dew shield hood is placed for the objective of 50 mm finder.

Upper left: Nexsus DSC
Nexus DSC
is placed on the lower part of the focuser. A part of the filter slider is seen on the upper right.
Lower left: Filter slider
Three filters, (IDAS LPS-P2, Lumicon Comet, Lumicon OIII, are equipped in the US made filter slider, The Astrocrumb FilterSlide Mark II. The dew remover (heater) is built-in in the slider. I often apply LPS-P2 filter under the condition of the moonlight or enhanced light pollution due to hazy sky.
Right: iPad mini2 (screen shot)
The digital map, SkySarari 5 Pro, is indicated on the iPad mini2. The iPad mini2 receives the signal from the Nexus DSC via WiFi and indicates the map linked with the FOV of the comet-seeker. To identify DSOs is very easy because the map shown on the screen is always linked with the FOV.

Upper left: Cases
A home-made case for iPad mini2 (left) and a carry case for Nexus DSC.
Lower left: Inside the cases
Aluminum form mat is inside of the case for iPad min2 to keep it warm. It makes the lifetime of the battery longer.
Right: Rear view
The power line extends from the rocker box where the battery is placed to the secondary cage via the heater controller. There are three heaters; the secondary mirror, the eyepiece and the filter slider. Kendrick Dew Remover is used in the secondary mirror and the eyepiece.

Left: Disassembled case for iPad mini2.
Right: Front view of the telescope

 Left: Rear view of a mirror cell. There is a cooling fan at the center. Two vertical wood blocks are to protect three light collimation knobs, when the mirror box is placed on the ground.
Right: Top view of 18 point flotation cell.

Insulator used for truss poles
Above: Insulator used after July 2017. There is no split like the insulator below. This sponge is for 22 to 23 mm inner dimameter but applied to 25 mm alminium pole. Upon inserting the insulator into the pole, the lubricant was sprayed both on the pole and the inner part of the sponge. Gripping feeling is better than the previous one and slender. Easy to use.
Below: Insulator used until June 2017. A split type insulator that is fixed using a tape.

Multifunctional stepladder

 Left: iPad mini 2 with the case is placed on the attachment with flexible arm (not detached every session). A clipboard and a pencil is also connected to the stepladder using the sling.
Right: The case of the iPad mini 2 is opened. Only when I look at the map I open the case to keep the inside warm for longevity of the

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 Left: Loaded 46cm comet-seeker
   1: primary mirror with PVC cap (sealed in the plastic bag with a zipper with silica gel), 2: step for loading, 3:
eight truss-tube poles, 4: eyepiece box, 5: bino-viewer box, 6: rocker box, 7: mirror box, 8: top ring (secondary cage), 9: stepladder
Right: insulator is used in summer.

Setting up

Left: Before installing the primary mirror.
Center: Inside the mirror box. There is sling that hold the edge of the primari mirror. Two out of three mirror clips are on the photo.
Right: The primary mirror is installed with the home-made white PVC cap.

Upper left: Removing the PVC cap leaving the primary mirror in the mirror box. After that the sling is slipped around the primary mirror and the mirror clip is rotated to avoid the mirror falling.
Lower left: The white PCV cap removed from the primary mirror and empty plastic bag with the zipper.
Center: Inserted eight truss poles into the pole clumps.
Right: The top ring (secondary cage) placed on the poles. The wooden pole seats that were used with the wooden wedge until June 2017 function as a guide of poles to keep them in correct position.


Left: Overlapping crushed truss poles and fix them using a nut.
Center: All poles were tightened with bolts and nuts.
Right: Tighten the lower end of poles in the pole clumps using the nobs. The other thing to set up is installing the light shroud, finders and etc.

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Primary & Secondary mirror: Galaxy Optics

Left: 18-inch primary mirror RMS: 0.032 lambda (1/31 lambda), P-V: 0.22 lambda (1/4.5 lambda).
        Serial number: SN01797-PS#1
Right: 3.1" secondary mirror RMS: 0.011 lambda (1/91 lambda), P-V: 0.086 lambda (1/12 lambda).
I have ordered a premium mirror: they make ten mirrors per one lot, and this is the best of them. The performance is superb!
The optics were polished in April, 2001.


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