Re: ATM First project ( Bit off too much? )

[GregJ888@aol.com]

The Houghton is a nice project.  The design is quite forgiving and very
interesting to make and you'll learn a lot.  I built an 8" several years ago,
and for a small astrograph/telescope recommend it highly.  IMHO BK7 is better
behaved and easier to deal with than Pyrex.  You will need some extra
equipment, jig to check for wedge and a monochromatic light source (florescent
tube).  Did I mention you'll learn a lot (:-)?

The critical step is to match the 2 like curves on the correctors, but you
interference test these so it's not hard, just takes some time.  You may want
to get a copy of the Newport Glass catalog, it has some information on lens
making that was most useful, to me anyway.

Now the bad news.  You will need to make and polish 4 more surfaces, not at
all hard, just takes a lot of time.  The mounting is also more difficult than
a standard Newtonian due to the lens cell.  I used Al for my tube and cell
assemblies and had them machined at a local shop (before I got my own lath)
which worked well.  

I used a fork mount, But would suggest you look at a GEM.  The tube of a LH
balances in the center due to the weight of the lens and cell.  This requires
fairly long fork arms, think the GEM would be a better fit.

Bottom line is the parabola will be easier to attain ( I like the 60% star
lap) than the Houghton.  The Houghton is a bit more interesting IMHO, and you
will LEARN LOTS...

If I can answer any questions, please let me know.


Greg Jones