Re: [ATM] Why Lurie-Houghton telescope very rare in the ATM

["Bob May" <bobmay@nethere.com>]

Paul, the LH design is not hard to buiild.  It's problem is that
the cost of refractor glass goes up as the size of the scope by
more than the size by a fair margin.  The curves on the corrector
are spherical and complementary so there really are no tools
needed to grind them.  Unfortunately, the volume of the glass
goes up fast.
When it comes to focal ratio, the basic Newtonian works well at
the slower focal ratios so there is no need to build a bit more
difficult scope which has 4 glass to air interfaces to reduce the
light input.  Without good anti-reflection coatings, you lose
about 20% of the light in the corrector.
The corrector is going to have gentler curves with a longer focal
ratio so that can become a bit of a problem as one pair of
surfaces will have a long ROC which can be a bit difficult to
test if you don't have the space to do the test.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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