RE: [ATM] Telescope Focusing at Public

[Mark Holm <mdholm@telerama.com>]

Quoting Donald Good <donald.good@comcast.net>:


 >>
 >>
 >> Whadiyathink?
 >>
 >>

It is certainly possible.  Whether useful enough to warrant the work, I 
don't know.

It is an intersting idea to have a standardized system that could work 
for all suitably equipped telescopes.  You don't really need a 
computerized or motorized focuser to join in the fun.  A calibrated knob 
would gain a substantial fraction of the benefit at lower cost and 
complexity.  Still, if you are going to have a computer controlled 
focuser for some other reason, this would be a relatively simple add on 
that would require extending only the software.

One useful question to answer is what the eye diopter correction versus 
focus distance function looks like for different eyepieces and 
telescopes.  Having at least the form of the equation, and then knowing 
how to fit data to the equation to derive the specifics for a particular 
eyepiece or eyepiece - telescope combination would go a long way to 
answering practical questions.  I am thinking of practical questions 
like how would you calibrate an eyepiece or eyepiece - telescope 
combination?

Some possible answers involve:

	A Hartmann style focusing mask to provide a focus indication that is 
independant of individual vision.  (Dead simple to make and commercial 
versions are already available for the lazy.)

	A set (perhaps as small as two) of lenses with known diopter 
corrections to go over the eyepiece to simulate eye focus errors.  These 
lenses really shouldn't be a huge barrier.  They could easily be made by 
an ordinary eyeglass lab, so long as you could actually convince them to 
do something that simple.

One question can be answered right off the bat.  The standard unit of 
measurement to use should be the diopter.  This is, at least in the 
U.S., universally used for specifying eyeglass corrections.  A person 
that knew her eyeglass prescription would not have to be retested in the 
field to learn a datum that has already been measured with good 
precision and accuracy by the optometrist.

Mark Holm
mdholm@telerama.com

_______________________________________________
ATM mailing list http://www.atmlist.net/