BTW, If the eyepiece height is low enough to avoid a ladder you may be able to angle the focuser like smaller dobs to make it more comfortable at lower declinations.
Do you mean position the focuser further around the telescope? I will look into it thanks
Looked thorugh George's scope at the SPSS which is the same design and also throught the 25" Obsession. Liked the idea of not climbing ladders in the night
Climbing up the ladder is what put me of the 25" at Lostock.
There were three of us looking through Georges scope the Wednesday night at Lostock before everyone arrived and the views through his 18" Nasmyth weren't half bad!
Being a mate he agreed to do the optics on the 24"
Nice work, I have been intending doing the same project for too long. One question, collimating? The tertiary mirror will certainly test these skills. IMO this design isn't exploited enough, for people restricted to a wheel chair it gives them easy access to the ep. I am waiting on the 16" mirrors to hit main stream, but the PMC silvered-silicon can't happen quick enough. I hope they utilize the technology and not keep it for the rich. Even at 14" trying to separate your memory recognition from visual resolution switches in and out. I know you are going to enjoy all the clear and easy views when this princess is completed.
I am waiting on the 16" mirrors to hit main stream, but the PMC silvered-silicon can't happen quick enough. I hope they utilize the technology and not keep it for the rich.
Eh, wot? PMC was a joke in the APRIL edition of the Bintel magazine!
I think this was the article courtesy from Night Sky Bintel.............
Precious Metal Clay, PMC, was developed and patented in the 1990’s by
Mitsubishi Materials of Japan and has been used since then to create handmade
items of jewelery. Microscopic particles of silver are mixed with a
moist binder to create a material that has the feel and working properties of
modeling clay. Using simple tools, objects are easily given shape, texture,
and character. After air-drying, the objects are heated to temperatures
approaching the melting point of the metal, where the particles fuse together
to make a dense, fully metallic object. Fired PMC work can be polished,
soldered, enameled, and worn as jewelery like any other silver item.
By substituting powdered Zerodur for eighty percent of the silver, test mirrors
have been made using the same process. Astronomical mirrors produced in
this manner are self-reflective coated and require only a very thin dielectric
coating to be made 98% reflective.
By utilising a pressure mould and injecting the PMC/Zerodur/silver slurry
into the mould under high temperature and pressure, a very accurate, thinwalled,
honeycomb mirror is produced. The surface accuracy, when removed
from the mould, is of a very high order and requires minimal ‘finishing’ to
produce a useable mirror.
The problem of ‘print-through’, which has always been the bugbear of
honeycomb mirrors, is avoided because of the added thermal stability due to
the Zerodur content and the open back of the honeycomb. Cost compares
extremely well with conventional mirror production. PMC mirrors are one
third the weight of a similar-sized glass mirror and are subject to less than a
tenth of the flexure. Thermal stability is almost as good as Zerodur.
PMC Glass Corporation has made a number of 1.45metre mirrors available
for evaluation by amateur astronomical societies under different climatic
conditions. Two of the mirrors are allocated to Australia. The first has arrived
and will be installed in a large Dobsonian-style mount. The second is yet to
be allocated to an astronomical society, but will be fitted into an equatorial
mount for comparison purposes.
Here are some pics showing my progress. I started working on the tertiary light baffle and curved spider veins. While I was doing that I decided to cut some ellipses with the minor axis being 78mm.
The cutting tool I made was out of an old pipe that was machined to the right thickness and diameter. To cut six layers of glass it took around 3 hours which gave me some time to make the spider veins.
All in all everything turned out well and tomorrow I'll finished the tertiary holder.
I was pleasantly surprised when I had the top half of the telescope assembled I got accustomed to seeing it as a drawing on the computer and when it's right in front of you you get a real perspective on size.
I was pleasantly surprised when I had the top half of the telescope assembled I got accustomed to seeing it as a drawing on the computer and when it's right in front of you you get a real perspective on size.
Looking great Ed Those Moonlirte truss blocks sure save a lot of work and calculation.
I was interested in your stratedgy of fitting a curved spider for the tertiary mirror rather than the more traditional approach of using another 4 vane spider and adjusting their position optically to line up with the secondary 4 vane spider .
Looking great Ed Those Moonlirte truss blocks sure save a lot of work and calculation.
I was interested in your stratedgy of fitting a curved spider for the tertiary mirror rather than the more traditional approach of using another 4 vane spider and adjusting their position optically to line up with the secondary 4 vane spider .
Well I am still experimenting with the veins.
I want to stay away from having the four veins aligned with the secondary because it is hard to do it precise and if it is off by a fraction the defraction spikes on a star image will be quiet long.
There are still other options to try. The thing in desinging and biulding your own scope is that if something dosen't work.... well, you find something that does.
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