Re: [ATM] Astigmatism

[waldo kitty <wkitty42@windstream.net>]

David Harbour wrote:
> Bob-
> 
> I know that you guys have worked out this astig. monster for thin blanks 
> over the years, and rather brilliantly. I have a rhetorical question:  why 
> did we, as the atm-ing community, go kind of crazy over these extra thin, 
> large blanks? As a proposal, why not just not worry about it, and use a more 
> traditional thickness ratio for the blank? (I am anticipating your answer)- 
> still would like to see your short version in print- thanks,

hiya davey...

i dunno 'bout everybody else but i've considered one because it is easier to get 
thin glass than thick...

i've always wanted to make a scope of my own and so i started reading this list 
before y2k came around... i've been gathering info and data and all kinds of 
stuff over the years... finally i decided that i should take a look at pricing 
some glass to actually make the mirror with... i literally fell out of my seat 
when i saw the prices! i've been looking at a "decent" sized "light-bucket" in 
the range of 8 to 10 inches... i have really been wanting to get a nice scope 
built and was hoping to be able to do something for less then $200US or so... it 
doesn't look like i'll be able to stay in that range considering that all the 
prices for glass in that size, that i've seen, have been a bit more than that :?

i even went looking for portholes recently and they've all been driven up in 
price due to folk buying them to put in their houses, campers, and (yeah) on 
their boats... i've seen some that were obviously plain glass in a porthole 
mount... considering those applications, sure, i can see that but it isn't what 
i was looking for for making a scope mirror...

i probably really should start a bit smaller for my first mirror and after 
seeing a video taken recently of the ISS flying overhead as viewed thru a 5 inch 
reflector has me kinda reconsidering my stance...

i just want something to replace the 4 inch refractor that we got some 40+ years 
ago when in japan when my father was in the US NAVY and stationed there... it's 
never been all that much and cost more than $200US back then... we've seen the 
planets with it and some of the moons... even the rings of saturn but the views 
leave a lot to be desired as they are/were (to me) very small and it is hard to 
track with manually twisting spring-like flexible tracking knobs... i think the 
mount is an equatorial as i have to set an angle equal to my latitude to be able 
to do much of anything... i really hate it because i just can't turn, lock and 
track like i'd really like to do... if/when i actually get a reflector built, i 
probably should look into cleaning the refractor up and ensuring that it is in 
proper order... i caught one of my kid brothers, years and years ago, attempting 
to put parts of it back together after he had taken them apart to see how they 
worked :?  i've already found one or two lenses that i had to flip around to be 
able to at least see thru them :roll:

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