Hi all,
Just wanted to let you know about a great site that shows you how to build and use a telescope for visual observing:
Regards Neil.
Hi all,
Just wanted to let you know about a great site that shows you how to build and use a telescope for visual observing:
Regards Neil.
To be accurate, the site offers to sell me the instructions rather than show me how.
And it does not appear to offer any infomation that is not available for free from multiple sources.
DAGS "Dobsonian", "Newtonian", and "Amatuer Telescopre Making".
I presume this was intended for another group? too much gazing into a long tube is not good for the sight.
I almost didn't get it.
Like most jokes about the sky, that was was over my head.
On a more serious note, I have casual observed that myopia is less common among amatuer astronomers than in the population at large. They do spend more time focussed at infinity and with a fully expanded pupil than do most. Maybe that has something to do with it.
: On a more serious note, I have casual observed that myopia is less : common among amatuer astronomers than in the population at large. : They do spend more time focussed at infinity and with a fully expanded : pupil than do most. Maybe that has something to do with it.
More likely that they didn't have myopia to begin with. And people that have myopia not getting into astronomy because they can't see all that well in a scope.
-- Andy Barss
Spammers don't care what group they pollute Mac
Not correct -- myopia normally develops in childhood.
Typically, the construction of an amateur astronomy telescope is largely a precision woodworking project; sometimes metalworking, sometimes ultra-precision glass grinding/polishing as well. Rather appropriate to your part of the planet I should suspect (having previously spent 11 years in Arizona). DAGS on ATM.
David Merrill
You aren't kidding about precision woodworking, though I don't think this one is typical:
-Leuf
My childhood was pre-teen.
About 20% of the population develops it between the ages of 5 and 20.
About 8% between 20 and 40.
And some develop it later.
Exactly.
To equate, as you did, "pre-teen" with "pre-myopia" implies that myopia typically develops during the teen years or _later_.
That's just not true.
>
And how does that break down into the 5-12 and 13-20 age ranges?
Doubtful. A more accurate statement would probably be that about 20% of the population is *diagnosed* between those ages. That figure undoubtedly includes some children who are congenitally myopic, or who developed myopia during their first five years, but were never diagnosed until their first routine vision screenings conducted by their respective public schools. I don't pretend to know how many children fall into that category, but I'm quite certain the number is greater than zero.
If you take a class from John Dobson or just follow his instructions, or just build any Dobsonian mount, the woodworking and other construction involved is hardly precision nor does it need to be.
Nowadays I am given to understand using a Dobsonian mount is by far the norm for a amateur telescope; I know I have seen a bunch of homemade Dobsonians but very few other kinds. Of course, that may be because Dobson stops by in my little town (pop 8000) to teach telescope making. He actually stays a couple houses down from me.
His whole focus is to teach how to construct a decent reflector with commonly available materials. The only items that were purchased specifically for the purpose in his class was the secondary reflector. Everything else is from materials adapted to making the telescope. The eyepiece for example was taken from a decent pair of old binoculars purchased at a pawn shop.
And, grinding and polishing and testing and adjusting the primary mirror, is done completely by hand and Dobson claims to get better results that way than by using equipment to grind it. He corrected my mirror after inspection of the diffraction pattern it produces off a reflection from a power line insulator, by pushing around the polishing rouge with his thumb in a circles for a few minutes.
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