(ATM) Ferguson's mirror 1

[kferguson@aquilagroup.com]

Before starting my first project, I spent many hours in the archives reading 
nearly everything but the administrative posts.  I found Allan Killian's 
"log" to be very inspiring, so I'm planning to do the same.

HOWEVER, I realize that some will object on the grounds that "we've heard it 
all before".  If you're one of those, then please e-mail me directly, and try 
to dissuade me. Encouragment would, of course, also be welcomed. It is, 
hwever, too late to stop the first installment, as you're already reading it 
:-).  There are some embedded questions so please read this even if you don't 
need the inspiration.
                                                            
I received the  abrasives kit yesterday from Willmann-Bell. I bought from 
them based on positive remarks from this group, and got the same prompt, 
accurate service others have reported.         

I'm still trying to come up with a good grinding stand..Steel drums just 
don't seem to be as common as when I was a kid.  Ideas for alternatives, or 
suggestions as to where to find a drum, would be most welcome.

I was quite anxious to see if my ceramic tool would work, so I put some wet 
newspaper on top of my washing machine (ahhh...the joys of bachelorhood!) 
Threw on some #60 (came with kit..books say start at 80??) and went at it.

To my great relief, the tool seems to work great.  Books say to expect my 
first wets to last "hardly a minute" with plate glass tool, but I got ~ 5-7 
minutes out of each of the two wets I did, with a nice "crunchy" sound/feel 
the whole time. I stopped there, because I can see that I am too lazy to turn 
the tool often enough..barrel walking seems like a better approach.  

The ceramic breaks down into clay, forming a runny paste with the water..this 
seems to do a nice job of lifting the grit up out of the channels. 
                                                           
I have Sam Brown's book (Edmund) and have borrowed older editions of 
Texereau, and Barry from public library.  Brown assumes I'm doing a 6".  I 
presume I should pretty much double everything (pressure, time, amount of 
grit, etc.) for my 8" due to ratio of surface area, and volume of glass to be 
removed?? If this is wrong, somebody please clear this up for me. (I think 
Tex or Barry may have had a table..I'll go to library and check them out 
again tonight)

f ratios???
I was (niavly, I now think) first thinking of going for a f/4.5, but after 
playing around with sketches, and doing a lot of reading, I have toned down 
my aspirations to f/6.0, which may still be a bit ambitious for a first 
mirror. Looking at the coma, and difficulty of figuring a fast mirror, it 
hardly seems worth the FOV or slightly enhanced portability.  I was thinking 
I wanted "rich-field" performance of the 4.5, but with the coma at field 
edges that  this would have, the  extra FOV doesn't, now, seem to me to be 
worth the bother.   I need to commit to a f/ratio before continuing with the 
mirror, so here is my proposed design, for the group to throw rocks at:

primary      8" , f/6
diagonal:    1 7/8" minor axis (~5% obstruction)
tube:        Plywood, octagonal, 11" minimum interior dimension
             interior mounted focuser.

other details "To Be Determined".
                                                               
I will glady pay 2 cents (less 1/2 buck shipping and handling!) for your 
comments. But please don't delay, as I hope to finish rough grinding this 
weekend.

Enough for now...Clear skies,

Kevin