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Academic & Professional Books  Reference  Physical Sciences  Cosmology & Astronomy

Collimating a Newtonian – The Correct, Easier and Definitive Approach Incorporating the Cave and Laser Telescope Collimators when useful

Handbook / Manual
By: Peter R Clark, FRAS(Author)
65 pages, colour & b/w photos, colour & b/w illustrations
Collimating a Newtonian – The Correct, Easier and Definitive Approach
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  • Collimating a Newtonian – The Correct, Easier and Definitive Approach ISBN: 9780957645400 Edition: 4 Paperback Mar 2017 In stock
    £7.50
    #221923
  • Collimating a Newtonian – The Correct, Easier and Definitive Approach ISBN: 9780957645431 Edition: 4 Paperback Mar 2017 Usually dispatched within 5 days
    £12.50
    #236277
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Collimating a Newtonian – The Correct, Easier and Definitive Approach

About this book

Completed in 2014 after 5 years of work, this is my new and rational approach to the instructions for collimating a Newtonian. A desperate search for support followed. It produced Arthur P. Norton BA on p.50 in the 11th to 15th editions of his Star Atlas. He proposed a change to how the secondary mirror was mounted in which the number of adjusters, 7 right on the limit of the human brain anyway to make the correct choice first time could be reduced to 5.

The metal work was performed by Royce, Hoffman and Ed Jones 50 years later at around the millennium but has not been taken up commercially. They either did without the secondary mirror's two lateral adjusters as per Norton or turned them into strict slaves of the central bolt. I accomplish the same with words alone.

Here then are the first 3 stages. C means for Schmidt–Cassegrain optics also. Please use them indoors straight away with a translucent 35mm film canister eyepiece, they are still available.

Stage [1]. Screw both mirrors fully out then back again dead equally to 2 turns off C. Sense the secondary mirror's adjuster bolts' contact and firm them lightly to begin from mechanically square. Then with dead equal turns on the adjusters experiment with centre bolt turns for the best shape that can be achieved without overlap and seeing the primary mirror's retaining clips. Do not fall for trying to make everything look perfect by intuitive suck-it-and-see with any of the adjusters. New Allen keys may be fiddly but they are the most accurate.

Stage [2]. Against a white background or by fitting one of my Cave Collimator caps, align the peep-hole so that a cursor line inscribed on it lines up with the focus tube axis. Then, if the doughnut is to one side, rotate the mirror gingerly to bring it over the focus tube axis. Minimal loosening is key, whichever one you can turn first.

Stage [3]. Tilt the primary mirror to centre the doughnut. Star testing will now tell you it's all done or shows you fine aberrations to correct for achieving the best results C. The Schmidt–Cassegrain secondary can also be done from the front in bright daylight because the aim is to make all the perimeters concentric. Either way, the adjuster to turn is linear with the distortion direction.

Should fine adjustment to the primary mirror on a slightly defocused star of about the 3rd magnitude still not produce reliable symmetry, something inside is loose, you were interrupted or you have a very fast Newtonian that requires stages 5 to 7 of the book. You can buy it from this site and reap the benefits; the 17pp version has diagrams, setting up an EQ mount for observing, telescope optician checked cleaning of mirrors and lenses, dew covers, and the precise scientific one use for the laser collimator. The 65pp extended version tells the full story plus eyepiece matching and upgrading, a bibliography, two narratives, acknowledgements, adjusting a laser collimator, making the Cave Collimator and contains some one-shot images, all this work has given me time for!

Customer Reviews (3)

  • The instructions work well with good results
    By Peter 2 Mar 2018 Written for Paperback
    "Peter Clark's more scientific technique for Newtonian 'scopes works well and requires just a peephole eyepiece as the only gadget needed. I have used the method on my 6" and 10" telescopes with good results. I do not have either a Cheshire eyepiece or a laser collimator and having seen the latter used can appreciate the risk of an eyeful of laser beam! There is no electronic aid that can substitute for a sound understanding of how a Newtonian is constructed and set up."
    – Christopher Eagleton, Beverley

    Author's notes:
    Christopher's comment about the laser collimator is pretty fair for his two f 5 Newtonians, but by f 3.9 is proving essential for the increasing accuracy in vertical tilt needed by the secondary mirror. Laser collimators do not feature in my instructions until stage[6]. Its beam will then be well within the secondary mirror diameter. Neither big bolt heads nor establishment writer could help the review of a 3.8 on p.94 of Sky at Night Jan 2018.
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  • His Cave Collimator works and the book takes over
    By Peter 2 Mar 2018 Written for Paperback
    "I am currently converting old spherical f3 Newise mirrors to paraboloids for putting them into telescopes for wide angle work, using coma correctors. Naturally, collimation will be an issue so we will be making use of your work."
    – Peter Wise

    Author's notes:
    Peter is a recipient of the BAA's Horace Dall Medal for showing marked ability in the making of astronomical instruments.
    0 of 1 found this helpful - Was this helpful to you? Yes No
  • Taming the dastardly thing.* It's all over now!
    By Peter 3 Mar 2018 Written for Paperback
    It has been very reassuring to have journeyed from adjusting both mirrors at every session for 4 years to just the f/3 primary mirror slightly twice a year since 2013; mainly by eventually regarding the secondary mirror's two lateral adjuster bolts as like the handlebars of a bike. Correction by turning them can cause the rider to fall off by gyroscopic inertia. Similarly, adjusting a Newtonian telescope's two lateral bolts just because they are there causes a fall off from collimation achieved. Then sourced from ideas and trusted writers, lower grade compensation then produces a twisted light path fit for one temperature. The instructions chapter steers you clear of such disasters, rocking the boat and ruffling feathers on the way. Adjustments have become easy and reliable for any f ratio.
    Slipping back into wrong methods again is actually prevented by the re-engineering support suggested in Norton's Star Atlas 11th and 16th editions from 1950 p.50. Then on the internet additionally there's Conrad Hoffman's secondary mirror holder* and in S & T October 2010, Ed Jones's Tracking Travelscope. They either don't fit the two lateral bolts or they lock them into being strict followers of the central bolt. Thus are instructions constrained into exactly the same method that scales up to the fastest optics as the author developed with words arising from his work alone before trawling for like mind support. Commercially, the principle of one adjuster (with slaves) falls foul of the establishment. There's nothing they'd claim three bolts are needed for that rotation about the central bolt doesn't perform more easily within the arc of concern at stage [2] and better for both medium and high magnification interests. Adjustments feel micrometer like with no hit or miss from 4 years into the task, even with the f 3.0 primary mirror of the main development 'scope.
    Was this helpful to you? Yes No
Handbook / Manual
By: Peter R Clark, FRAS(Author)
65 pages, colour & b/w photos, colour & b/w illustrations
Media reviews

"'The Cave Collimator was excellent for my Maksutov–Newtonian telescope and very good for my Rumak–Cassegrain."
– Professor Ian Morison, Jodrell Bank

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