Re: [ATM] Astigmatism

[George Blahun Jr <ks1u@att.net>]

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...

Waldo:
      If you have a 100mm Japanese refractor from the 60's, it might  
be worthwhile refurbishing that and putting it on a new Alt Az mount  
(some come with tracking, see IOPTRON for example) for not much  
money.  It is difficult to screw up the making of most achromats as  
the surfaces are generally all spherical.  If the elements are put  
together correctly, the tube could probably benefit from some flocking  
and if it has a diagonal, perhaps a new dielectric unit.    You might  
be surprised at the images it is capable of producing.  If it gives  
decent images and it's uncoated, you could probably get it coated to  
give even better images of the planets.  Of course a good eyepiece  
would be essential and you can get adapters to accommodate modern  
designs.

George
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