The Dobsonian Telescope Book Pdf

The Dobsonian Telescope: A Practical Manual for Building Large Aperture Telescopes. Kriege, David; Berry, Richard. Published by Willmann-Bell, 1997. ISBN 10: ISBN 13: 552. The unassembled Dobsonian base. Be careful unpacking the boxes.We recommend keeping the original shipping contain-ers. In the event that the telescope needs to be shipped to another location, or returned to Orion for warranty repair, hav-ing the proper shipping containers will help ensure that your telescope will survive the journey intact. Web-book that will help and there are many other web pages to check out. I'd highly recommend that you read the books Build Your Own Telescope by Richard Berry and Making and Enjoying Telescopes by Miller and Wilson. You should also know that you can buy a telescope much like this for about $400 or $500.

Building 20 inchtruss-tube Dobsonian telescope

The courage to undertake this projectresulted from successful completion of 24inch f4.5 Venor Telescope by fellow membersof RASC - Kingston Centre. While many construction steps werecarried alone in my basement, I have enjoyed a tremendous help ofDoug Angle. His persistence and inventiveness cannot beoverstated!

To construct my truss-tube telescope, Ihave generally followed instructions outlined in the book'The Dobsonian Telescope: A Practical Manual to BuildingLarge Aperture Telescopes' by David Kriege and Richard Berry(Willmann-Bell, 1997). While great on woodworking and otherconstruction techniques, it contains only short (though veryuseful) chapter on making large aperture optics. To tackle mirrormaking, I dipped extensively into vast knowledge compiled in'Amateur Telescope Making' edited by Albert G. Ingalls(Scientific American, editions: 1928, 1933 and Book Two - 1949).Making a flat diagonalmirror is described on the separate page.

  • At the end of February 2002, I finally decided to plunge into it. First step consisted of ordering BVC (black vitrified ceramic) blank from ASM Products in St.Basile, Quebec. To save some time, it was ordered with pre-generated rough f4 curve.

  • By that time three 7 inch Pyrex disks were polished flat already (all to about 1/16 wave). Two 4.5 inch (minor axis) elliptical mirrors were cut for Venter Scope and the third was cut to make 4 inch secondary for my future beast.

  • While waining for 20 inch blank (expected to be delivered in late March), I started to build other vital part of the telescope - follow links below for individual steps:

  • Finished scope is still quite a bit bottom heavy leaving about 2.5 lbs for additional gadgets to be attached to secondary cage (counterweight for now). There is enough room for CCD camera in the future as well ;-)

Scope overview

  • primary mirror: diameter = 20' (508 mm), FL = 2033.7 mm (f4), enhanced aluminum coating

  • secondary mirror: minor axis = 4' (101.6 mm), enhanced aluminum coating

  • finders:

  1. red-dot 1x finder

  2. homebuilt 6' f4 scope (primary and secondary mirrors coated with enhanced aluminum) with 25mm eyepiece (24x)

  • eyepiece height at zenith: 78' (no ladder needed - just a step stool)

  • total weight (without wheelbarrow handles): 192 lbs (87.2 kg)

  • portability: long distance - fits inside Ford Escort stationwagon with room to spare (left image below)

short distance - everything rolls together in one compact package (including step stool)

  • setup time: 15 min. with practice

  • construction time: March 2 - July 16, 2002 (not including diagonal)

First light

After some testing and adjustments, thefirst official night of observing started on the evening of July30, 2002. After setting up and cooling the scope, I havere-colimated it and then star-hopped to a newly discovered comet2002 O4. It was noticable in 6 inch finder but 20 inch showed ita7 133x as a quite large oval with point nucleus (no tail,though). Below are two images taken about an hour later with aCookbook CCD camera on Celestron 8 inch f6.3 SCT (both are 30sec. unguided exposures). Motion of the comet is quite apparent -UT of midexposure and coordinates of the nucleus are listed.North is up. Only part of the frame is shown. The scale wasreduced to 75% as well.

Some other objects observed that nightincluded:

The Dobsonian Telescope Book Pdf

The Dobsonian Telescope Book Pdf Download

  • M4 (red giants stand out nicely)

  • M6 (tested seeing low over horizon, bright orange star on one side of the cluster of blue stars)

  • Trifid Nebula (beautifully defined dust lanes)

  • Ink Spot (very low over horizon but still clearly 'a hole' in the Milky Way)

  • Swan Nebula (faint outer loop of nebulosity easy to see as well)

  • M11 (my all time favourite)

  • Veil Nebula (well, 20 inch shows a lot, even without nebular filter with rising Last Quarter Moon!)

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I have also located Pease 1planetary in M15- that was my second challenge for the first light observing!Blinking with nebular filter confirmed sighting of this extremelydifficult object.

The Dobsonian Telescope Book Pdf Downloads

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© Jan Wisniewski