[ATM] FW: questions about the condition of this mirror

[jcmulherin]

Roman:

It's better to use square tiles because it's easier to clean the channels
when it's time to go the next grade of abrasive. Start with #600, then 12
micron, then your 9 or 5 micron. I prefer 9 as it's less likely to sleek
during the final stages.

Inspect the surface with your magnifier while shining a light through the
back of the blank. Back-lighting the surface of the mirror makes residual
tool marks more visible. Keep working with the 600 until all tool marks and
pits are gone. Make sure you check the center and near the edge of the
blank. When the surface is ready, move on to 12 micron.

To make the grinding tool fist, press all the channels out of your pitch lap
so you have a solid surface. Cover the mirror surface with wax paper.
Arrange your tiles on the paper. The back of each tile should receive a very
thin coat of linseed oil. Heat the tiles with a hair dryer or heat gun. Heat
the pitch surface the same way, just to the point of tackiness. Press the
pitch onto the tiles. Ideally the pith will fill the channels between the
tiles about half way. If the tile don't press in far enough re-heat and
re-press. If they press in too far, clean the pitch out of the channels with
a single edge razor. 

James

James Mulherin
President/Lead Optician
Optical Mechanics, Inc.
jcmulherin at opticalmechanics.com
www.opticalmechanics.com
Tel (319) 351-3960
Fax (319) 351-3943
 

-----Original Message-----
From: Roman Toledo [mailto:rtoledo2002 at yahoo.com] 
Sent: Sunday, July 08, 2007 3:11 PM
To: jcmulherin
Subject: RE: [ATM] questions about the condition of this mirror

I was afraid of that, you know I'm new to this but this mirror looked like a
jewel to me so it never occurred to me it needed fine grinding, well you
have
now made me resolute to make a tool. it's amazing I went to black rouge
after
the regular polishing, this mirror reflects so good i just found it
impossible
to think those sleeks were on the front, but i used a eyepiece as a loupe
and
sure enough it's the front. lots of lessons learned on this, but still
having a
lot of fun and this is the best therapy I've ever found.

If I may ask, in making a grinding tool , should I go out and buy some real
nice 
smooth porcelain hexagon tiles and sit them on face of the glass covered in
parchment paper so it's mated?  OR

can I use the pitch tool covered in polishing pads go back to 600 and trow
it
out once I get ready to do the final CEO polish?

don't hold back and tell me what should be done the RIGHT way as I want to
come
as close to as possible to the quality finish you make, I have a couple of
scopes to use while i make this one.

thanks James for time.
Roman


--- jcmulherin <jcmulherin at opticalmechanics.com> wrote:

> Hi Roman:
> 
> If I understand correctly you started polishing the mirror without first
> fine grinding it? If this is correct, then you definitely have to do some
> fine grinding first. You can start with #600 silicon carbide or 18 to 20
> micron aluminum oxide.
> 
> A blank that has been curve generated may look smooth enough to polish to
> the naked eye but it definitely has some tool marks if you inspect it with
a
> magnifier.
> 
> James
> 
> James Mulherin
> President/Lead Optician
> Optical Mechanics, Inc.
> jcmulherin at opticalmechanics.com
> www.opticalmechanics.com
> Tel (319) 351-3960
> Fax (319) 351-3943
>  
> 
> -----Original Message-----
> From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf
Of
> Roman Toledo
> Sent: Sunday, July 08, 2007 2:09 AM
> To: atm at atmlist.net
> Subject: [ATM] questions about the condition of this mirror
> 
>      Mark it looks like it's on the surface, that old saying "if you don't
> use
> it you loose it" is at work here, I forgot some useful things I learned
last
> year and since I put it all away for a while I forgot them.
> 
>     First mistake is I did not check the surface when I got it, mainly
> because
> this mirror looked so smooth, it never occurred to me to look for sleeks.
I
> got
> up this morning and decided to polish out the back some more, and got it
> looking really good but not 100%, I probably ended up adding some more
> sleeks
> but i was very careful, for what ever reason I took apart a eyepiece t use
a
> loupe glass and inspected it and sure enough the scratches specially the
one
> that looks like a V or Y  and bunch of others are on the top.  the
scratches
> look like the Grand Canyon so fine grindind looks to me like 320? or a lot
> of
> 600?
> 
>     So my dilema is I never made a fine grinding tool, I went straight to
> pitch
> (73 modified with some linseed oil )so I may have to do one.
> 
>     can I do a fine grind by using pads on top of pitch?  and then discard
> it
> and make a new pitch lap  or should I just do what I think I know must be
> done,
> make a new tool, and should I buy smooth porcelain tiles ?
> 
> Mark Holm thank you.
> 
> anyone please feel free to comment
> 
> PS: Greetings go out to Richard Schwartz and David Harbour have not seen
> much
> in here from you gents lately
> 
>   
> Regards
> Roman
> 
> 
> 
> regards,
> Roman Toledo
> Celestron Nexstar GPS 9.25
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 
> 


regards,
Roman Toledo
Celestron Nexstar GPS 9.25