From: "Jerald F. Wright" 
To: DAVID K OESTREICH 
CC: ATM shore 
Reply-To: "Jerald F. Wright" 


    Anyone's first mirror is not likely to be their dream telescope.  So I
wouldn't spend much time crying about what you don't like about number one.
 Do spend time making plans to make number two more to your liking.  You
should do better on number two.  And take some time out to appreciate that
you finished number one.

    I second Vladimir's points.  You make the mirror. You measure the radius.
You decide when it is polished. and you decide when the figuring is
finished. And you pick from all those various methods for doing those
processes which to use.  It is nice to have experienced advise available.
But you should learn each
process yourself as you proceed, what the desired outcome of each is, and how to
know you have reached the desired outcome.

    I don't really know, but I think Michael Burr's take is probably correct
about John Dobson having more of a bent toward getting scopes to the masses
so to speak. There is really nothing wrong with that.  Like I said in the
beginning, your first mirror is not likely to be your dream scope. Get
someone through that first mirror and if they have TM in their genes they
can make and learn more.

    Also I would think that most classes would have time limits that would not
allow time to be meticulous. Unless the class instructor has unlimited time
the instruction would have to be limited to helping students through each
stage in time to move to the next. Not likely all will be truly ready to
move to the next
step. But if you only have a limited time you move to the next ready or
not. Learning the process is more important than each mirror being
perfectly made. Most classes teach you methods to make a mirror. After
making that mirror you hopefully know enough to learn to do them well
enough to make a high quality mirror. I have helped individuals make
mirrors. I can't imagine what it is to help  a number of people in a class
to do a good job on each step of making a mirror. Some of those mirrors are
going to have flaws. They will probably still work and the maker will have
a mirror to make a telescope with. It would have to
be extremely bad not to bring a smile to the makers face on viewing first light.
Class mission accomplished. An ATM is born. This is good.

    I recommend Texareau's "How to Make a Telescope" as the best
book on mirror
making.  I wouldn't send someone off to make their first mirror without it.
 It is unlikely you will run into a problem that he doesn't cover.  I don't
do everything the same way as in his book. There are many different
techniques. All of his will work.  If you use a different technique and it
does what needs to be done that is ok. I suggest reading the book before,
during and then especially after making you mirror.  If you are like me
there will be much you missed in that book that you will see after you know
from experience what Texareau  is talking about. It will make the important
things stick to your grey
matter better.

    As for advise on what to do with your mirror tool and lap, I know what I
would do.  But I have seen all of my suggestions given already although it
was split up between about 4 responses to you.  Well there is one idea I
haven't seen mentioned.  Keep the f8. It is your first mirror.  Get another
blank for your f6. It will only add to the work by the amount required to
hog out to f8. Once you have done that you will be where you are with your
"first mirror" regarding grinding it to f6. The expense is for
one blank and you still have the
number one mirror that you may want to do something with later. You can refigure
it if it has a bad figure.  In fact it wouldn't be such a bad idea to see if you
can put a good curve on the f8 before doing the f6.  If you can't get a
good curve on the f8 you probably won't get a good curve on an f6.  I'll
say if it is
fully polished from center to the edge the turn down can be polished out.

    I wouldn't want a 12.5" f8 to be my only scope. But If I were able to
permanently mount it I would like it. An f8 telescope makes the best use of
commonly available eyepieces. You can get the lowest reasonable power with
eyepieces around 50mm. And the commonly available short fl eyepieces will
get you to the upper limits of reasonable power. I wouldn't want to carry
around a monster though.

Jerry

--- BBBS/NT v4.00 MP