Hi Raymond,
bit of a quandary really. My 14"f5.1 and 25"f4.7 (Also have 25"f5 and f5.3 mirrors, [need varying amounts of figuring to finish off properly]) use 3.1"ma and 4" ma secondaries sourced from Hubble Optics, (reasonably priced, and work quite well).
For a 33"f4, going to need at least a 6 1/2"ma (for good size fif). Looking around the "net", looks like US$1000 HO to US$1350 Astro Systems + Freight + GST etc, so wouldn't have much change out of NZD$2000, so way out of my budget, (want to build entire scope for less than NZD$2000).
So looking at my options, and seems only to be the one, make it myself. Got plenty of thick glass lying around (still 1/2 ton), included are a number of 12.2"/12.6" diameter blanks 1 3/8"/1 1/2" thickness. So will probably take out three of these, and do the ABC grind for a flat surface, waterjet from one a 7"ma ellipse, and with "net" help, hope to be able to successfully reasonably figure same.
Takes me back to my mid teens when the biggest scope I could locate, and buy in NZ (1961), was a 3" reflector I paid 17pounds 10shillings($35),which cost me a months wages, (farm hand) at the time. Also had a 2 1/2" refractor (used) 22pounds.($44). In those days the moto was, "if you cant get it, then you have to make it". As this was the only option, built my first 5 3/4"/7"(made two mirrors-the second the 7" mirror was really quite good to 50x per inch) EQ mounted Newt from the mirror up. Really things haven't changed that much, "necessity being the mother of invention".
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