GSO-based two speed crayford focuser info

This is my focuser. The link under the image goes to the great instructions on its disassembly and tuning.

DIY Barlowed collimator

I've got a stock laser collimator with my Dob. Its construction is based on some primitive China made keychain laser pointer enclosed in the aluminum tube with a side window. It's really frustrating to work with, so I've been looking for alternatives for a while.

After searching online I've realized that this construction is quite common in cheap accessories from many vendors, the Orion for example.

Primary's alignment mod

Finally installed the famous Bob's Knobs mod. Specifically crafted for the Zhumell 12" model, these screws are almost perfect solution for a tool less collimation of the primary telescope mirror in the field. The transaction with these guys went smoothly. The delivery time was surprisingly quick.

Installation was done in place without the mirror cell removal necessary, one knob at a time. Just hold the springs in place.

My Zhumell 12" dob specifications

Apperture - 305 mm (12 inch)
Focal Length - 1500mm
Focal Ratio - f/4.93
Star Diagonal - 1.25 Inches (32 mm)

Finderscope - 8x50

GoTo - No

Weight Complete - 75 lbs (34 kg)

Total height - 63 inches (160 cm)

OTA length - 60 inches (152.5 cm)

Base height - 27 inches (68.5 cm)

Base diameter - 25.5 inches (65 cm)

Calculated

Aperture Gain - 1900

Visual magnitude limit - 14.2

Max FOV - 1.9 deg

Resolution - 0.38 - 0.68 sec
Maximal Magnification - 300
Optimal Magnification - 150
Minimal Magnification - 42
Absolute Maximum Magnbification - 750

See the great Telescope Equations site for the underlying theory and formulas.