Q: 10" six point primary cell

Someone asked about six point cell before and as I am in the same
situation I will continue with more questions.

The plan is to use three aluminium bars, with "hinge" in the middle.
Should I put small bolts in the end of bars and then glue the mirror to
them with silicone? Or should I glues the mirror directly to the end of
the bars? What about the strength of the bonding, will the small patches
of silicone, even smaller with the bolts, hold the mirror?
--
Lauri

Never tried 6 points but isn't 9 point prefered for this size? Here is a
link to my telescope whith a nine point cell using marbles and three
triangular aluminum supports. Have a look and see what you think.
http://www3.sympatico.ca/richlauzon/telescope.html



"Lauri Uusitalo" wrote in message
...
Someone asked about six point cell before and as I am in the same
situation I will continue with more questions.

The plan is to use three aluminium bars, with "hinge" in the middle.
Should I put small bolts in the end of bars and then glue the mirror to
them with silicone? Or should I glues the mirror directly to the end of
the bars? What about the strength of the bonding, will the small patches
of silicone, even smaller with the bolts, hold the mirror?
--
Lauri

Six point cell for 10" primary, lower portion of this page:

http://astronomy-mall.com/regular/pr.../cpt/cell.html

Mark

On Tue, 23 Mar 2004 12:14:01 -0500, "Rich Lauzon"
wrote:

Never tried 6 points but isn't 9 point prefered for this size? Here is a
link to my telescope whith a nine point cell using marbles and three
triangular aluminum supports. Have a look and see what you think.
http://www3.sympatico.ca/richlauzon/telescope.html



"Lauri Uusitalo" wrote in message
...
Someone asked about six point cell before and as I am in the same
situation I will continue with more questions.

The plan is to use three aluminium bars, with "hinge" in the middle.
Should I put small bolts in the end of bars and then glue the mirror to
them with silicone? Or should I glues the mirror directly to the end of
the bars? What about the strength of the bonding, will the small patches
of silicone, even smaller with the bolts, hold the mirror?
--
Lauri

It can be glued directly to the bars. Make the silicone blobs 2-3 mm thick
and 10-12 mm. wide. For alumium you need to use a primer for better bonding
of the silicone glue (I have experimented with that). Before applying primer
or silicone, the metal has to be cleaned well, with acetone or
trychloorethyleen. If done well, there is absolutely no change the mirror
will come loose.

--
Jan
http://home.wanadoo.nl/jhm.vangastel/


"Lauri Uusitalo" schreef in bericht
...
Someone asked about six point cell before and as I am in the same
situation I will continue with more questions.

The plan is to use three aluminium bars, with "hinge" in the middle.
Should I put small bolts in the end of bars and then glue the mirror to
them with silicone? Or should I glues the mirror directly to the end of
the bars? What about the strength of the bonding, will the small patches
of silicone, even smaller with the bolts, hold the mirror?
--
Lauri

Rich Lauzon wrote:

Never tried 6 points but isn't 9 point prefered for this size? Here is a
link to my telescope whith a nine point cell using marbles and three
triangular aluminum supports. Have a look and see what you think.

http://www3.sympatico.ca/richlauzon/telescope.html

Nice scope. What were the factors that caused you to choose a 1.83"
secondary? I'm building a 10" f/5.8 and I haven't decided which size
secondary to use. The 'Newt' design program indicates a 2.14" secondary
will cause some vignetting of the 75% light cone in my case, so that's
why I'm considering using a 1.83" secondary.


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Jan van Gastel wrote:

It can be glued directly to the bars. Make the silicone blobs 2-3 mm thick
and 10-12 mm. wide. For alumium you need to use a primer for better bonding
of the silicone glue (I have experimented with that). Before applying primer
or silicone, the metal has to be cleaned well, with acetone or
trychloorethyleen. If done well, there is absolutely no change the mirror
will come loose.

Thank you for the answer. What are you using for the primer?

--
Lauri

"Rich Lauzon" wrote in message ...
Never tried 6 points but isn't 9 point prefered for this size? Here is a
link to my telescope whith a nine point cell using marbles and three
triangular aluminum supports. Have a look and see what you think.
http://www3.sympatico.ca/richlauzon/telescope.html

According to PLOP, a 20" scope 2" thick can be supported with 6 points
and have 1/128 wave (or better) of mount-induced error. Tom Krajaci
has a 16" by 1.6" mirror on a 6 point cell working great.

A 4 point cell would be adequate for a 10" with reasonable thickness.

In addition, PLOP, also indicates that the better arrangement for 9
points is a ring of 9 rather than two rings of 3 and 6. Further PLOP
studies show that a ring of 8 and a single point in the center
outperforms all other 9 point arrangements.

Mitch

(Mitch Alsup) wrote in message . com...
"Rich Lauzon" wrote in message ...
Never tried 6 points but isn't 9 point prefered for this size? Here is a
link to my telescope whith a nine point cell using marbles and three
triangular aluminum supports. Have a look and see what you think.
http://www3.sympatico.ca/richlauzon/telescope.html

According to PLOP, a 20" scope 2" thick can be supported with 6 points
and have 1/128 wave (or better) of mount-induced error. Tom Krajaci
has a 16" by 1.6" mirror on a 6 point cell working great.

A 4 point cell would be adequate for a 10" with reasonable thickness.

In addition, PLOP, also indicates that the better arrangement for 9
points is a ring of 9 rather than two rings of 3 and 6. Further PLOP
studies show that a ring of 8 and a single point in the center
outperforms all other 9 point arrangements.

I understand how to make the two rings of 3 and 6 supports support
their share of the load - just three triangles each of which carry two
of the points from the outer ring and one of the points from the inner
ring. If you then support each triangle at the right point,
everything balances and the mirror is supported properly. But how in
the world do you come up with an arrangement of triangles and lever
arms to make the correct load sharing between a center point and the
ring of eight points?
Clif
Mitch

It's a primer especially made to apply before applying silicone RTV. I buy
it in the same shop I buy the RTV.

--
Jan
http://home.wanadoo.nl/jhm.vangastel/Astronomy/

"Lauri Uusitalo" schreef in bericht
...
Jan van Gastel wrote:

It can be glued directly to the bars. Make the silicone blobs 2-3 mm
thick
and 10-12 mm. wide. For alumium you need to use a primer for better
bonding
of the silicone glue (I have experimented with that). Before applying
primer
or silicone, the metal has to be cleaned well, with acetone or
trychloorethyleen. If done well, there is absolutely no change the
mirror
will come loose.

Thank you for the answer. What are you using for the primer?

--
Lauri

(Clif) wrote in message . com...
(Mitch Alsup) wrote in message . com...
"Rich Lauzon" wrote in message ...
Never tried 6 points but isn't 9 point prefered for this size? Here is a
link to my telescope whith a nine point cell using marbles and three
triangular aluminum supports. Have a look and see what you think.
http://www3.sympatico.ca/richlauzon/telescope.html

According to PLOP, a 20" scope 2" thick can be supported with 6 points
and have 1/128 wave (or better) of mount-induced error. Tom Krajaci
has a 16" by 1.6" mirror on a 6 point cell working great.

A 4 point cell would be adequate for a 10" with reasonable thickness.

In addition, PLOP, also indicates that the better arrangement for 9
points is a ring of 9 rather than two rings of 3 and 6. Further PLOP
studies show that a ring of 8 and a single point in the center
outperforms all other 9 point arrangements.

I understand how to make the two rings of 3 and 6 supports support
their share of the load - just three triangles each of which carry two
of the points from the outer ring and one of the points from the inner
ring. If you then support each triangle at the right point,
everything balances and the mirror is supported properly. But how in
the world do you come up with an arrangement of triangles and lever
arms to make the correct load sharing between a center point and the
ring of eight points?
Clif
Mitch

Two triangles handle 6 of the 8 points on the outer ring. These triangles
are long and not very wide. The third triangle handles 2 points on the
outer ring and the center point. This triangle is wide and not so
long. To utilize the power PLOP brings to the game of mirror support
you (basically) have to loose the mental concept of pure symetry.
You also need to loose the concept that each point needs to carry the
same load.

Mitch