A Telescope in the Works ...

An ATM buddy of mine (Kevin F.), whom I met and helped during a project of his, kindly offered to send me a 6" f/10.6 mirror of very high quality that was made by another mutual ATM friend (Mark H.).  I was hesitant to accept such a gracious offer, knowing the pedigree of the mirror; however, Kevin insisted that he was unlikely to use it (he likes BIG mirrors ... currently working a couple of 36" mirrors) and that he REALLY wanted me to have it.  So, I finally accepted his offer and the next day, he had delivered the mirror and a matching secondary (also figured by Mark H.) to the shipping company, where it commenced a journey that would take it half-way around the world from Pennsylvania, USA to Sri Lanka.  Shipping estimates the mirror's arrival on Friday, 17 January ... Kevin does not mess around when it comes to ATM projects ... :)

I had accepted the mirror, thinking I'd eventually use it in a CHief design (an unobstructed reflecting telescope, that uses two commercially available lenses, that are tilted to correct for image aberrations resulting from tilting the primary mirror).  I was hoping Ed J. (the designer of the CHief telescope design) would work up an optimized solution for that particular mirror using ZEMAX (a sophisticated optical design program).  Ed worked up a good design for me; however, I desired a slightly different arrangement to improve the performance and am currently awaiting those changes to be made.  More about CHiefs can be found in the Yahoo Groups "Spiderless": http://groups.yahoo.com/neo/groups/spiderless/info

Meanwhile, as there will be some delay in getting the CHief design finalized as well as requiring the purchase and delivery of the two corrector lenses and a larger 'flat' folding mirror; I have decided to use the mirror in a (much easier to construct) Newtonian configuration, until such time as the CHief can be built.

Living in Sri Lanka at a latitude of 7 degrees North of the equator presents some interesting mounting challenges.  I was originally thinking of constructing an inexpensive equilateral 'pipe' mount; however, the low latitude results in the polar axis being nearly horizontal ... which leads to problems with the counter-weight and scope clearing the pedestal supporting the equilateral head.  A lot of searching and head scratching, trying to find a way around this difficulty, finally convinced me that an Alt-Az mount, such as those used on the very common Dobsonians would be the most friendly so near the equator.  A clever device, known as an equilateral platform can be placed under the Alt-Az mount, which allows for tracking the stars for short periods of time ... perfectly acceptable for a telescope intended for visual use.

Next: Working up a Design ...