Ready References
A Guide to Backyard Astronomy
The Art of Using a Telescope
Power and Aperture in Binoculars
Variable Stars Explained
Essential Technologies for Making Accurate PC-Based Measurements
Optical Instruments
Notes on the Construction and Design of Instruments and Apparatus
Ready References Power and Aperture in Binoculars Essential Technologies for Making Accurate PC-Based Measurements 
Notes on the Construction and Design of Instruments and Apparatus 