Stopping down a Starfinder 10" Dob for viewing Mars

I had a look last night at the first edition of "The Backyard
Astronomer's Guide" but could not find info on stopping down a
telescope. I also looked in the index for 'aperture mask' but only
found 'aperture fever'! Nasty ailment!

I have a few questions:

a) What material should I use for making my own aperture mask? I would
imagine a thick, rigid plastic sheet would do the trick. Any other
suggestions?

b) For the 10" f/4.5 scope, what will be the optimum size for the hole
that I should cut into the sheet.

c) How crucial is it to make the edge of the hole smooth?

d) I can imagine that I should place the sheet so that the hole does not
get obstructed by the secondary's support legs.

What else did I miss?

Victor wrote:
I had a look last night at the first edition of "The Backyard
Astronomer's Guide" but could not find info on stopping down a
telescope. I also looked in the index for 'aperture mask' but only
found 'aperture fever'! Nasty ailment!

I have a few questions:

a) What material should I use for making my own aperture mask? I would
imagine a thick, rigid plastic sheet would do the trick. Any other
suggestions?

Anyting which will not pass light nor contaminate your optics .. and can
be held in place.



b) For the 10" f/4.5 scope, what will be the optimum size for the hole
that I should cut into the sheet.


Hole should fit between two legs of the spider so there is nothing in
the light path. Can be bigger with a three leg spider than with a fout
leg spider.

c) How crucial is it to make the edge of the hole smooth?


Dunno; likely not too critical

d) I can imagine that I should place the sheet so that the hole does not
get obstructed by the secondary's support legs.


Yes .. see b)

Victor wrote:
I had a look last night at the first edition of "The Backyard
Astronomer's Guide" but could not find info on stopping down a
telescope. I also looked in the index for 'aperture mask' but only
found 'aperture fever'! Nasty ailment!

I have a few questions:

a) What material should I use for making my own aperture mask? I would
imagine a thick, rigid plastic sheet would do the trick. Any other
suggestions?

Anyting which will not pass light nor contaminate your optics .. and can
be held in place.



b) For the 10" f/4.5 scope, what will be the optimum size for the hole
that I should cut into the sheet.


Hole should fit between two legs of the spider so there is nothing in
the light path. Can be bigger with a three leg spider than with a fout
leg spider.

c) How crucial is it to make the edge of the hole smooth?


Dunno; likely not too critical

d) I can imagine that I should place the sheet so that the hole does not
get obstructed by the secondary's support legs.


Yes .. see b)

Dale wrote:

I have a 10" f/4.5 (Meade DS-10), and I use an aperture mask made of
ordinary cardboard.

Thanks to Dale and Phil for the info.

Dale, what are the effects of the mask when viewing Mars with your 10"?

Regards
V

Dale wrote:

I have a 10" f/4.5 (Meade DS-10), and I use an aperture mask made of
ordinary cardboard.

Thanks to Dale and Phil for the info.

Dale, what are the effects of the mask when viewing Mars with your 10"?

Regards
V

Victor wrote:

Dale, what are the effects of the mask when viewing Mars with your 10"?

Regards
V


Primarily less glare & better detail; also works well with green (#56)
and orange (#21) filters.

Dale

Victor wrote:

Dale, what are the effects of the mask when viewing Mars with your 10"?

Regards
V


Primarily less glare & better detail; also works well with green (#56)
and orange (#21) filters.

Dale

Unless there is a problem with your telescope, you should not stop it down. If
the image is overly bright, use a neutral filter. In some cases, you might
possibly be helped by stopping down if there is air turbulence with "cells"
smaller than the aperture of your scope. For an off-axis mask, black
constuction paper with a 90mm opening would be OK, if you carefully measure so
that it is all on the mirror but does not get blocked anywhere by the
secondary. I prefer a central mask, from about 8"-10" aperture, as a way to
prevent unwanted incident light from interfering with your contrast. With good
seeing and good mirrors, full aperture is best....

Clear, Dark, Steady Skies!
(And considerate neighbors!!!)

Unless there is a problem with your telescope, you should not stop it down. If
the image is overly bright, use a neutral filter. In some cases, you might
possibly be helped by stopping down if there is air turbulence with "cells"
smaller than the aperture of your scope. For an off-axis mask, black
constuction paper with a 90mm opening would be OK, if you carefully measure so
that it is all on the mirror but does not get blocked anywhere by the
secondary. I prefer a central mask, from about 8"-10" aperture, as a way to
prevent unwanted incident light from interfering with your contrast. With good
seeing and good mirrors, full aperture is best....

Clear, Dark, Steady Skies!
(And considerate neighbors!!!)

That's exactly how I made mine for my 13". I just bought an extra cap.
And the cutout made a nice coaster for my big ice water mug...

But over time, I found I much preferred full aperture observing, even on
the moon and planets, and it fell into disuse, and eventually disappeared
(meaning it somehow got thrown away... not by yours truly, of course, but
on the other hand, I wasn't using it, so I guess that's really
irrelevant...)...

--
To reply, remove the "z" if one appears in my address
"Florian" wrote in message
news
Just sitting here looking at my 10" dob across the room and realized i
could
cut a round hole in the lens cap [guess it's not really a lens cap since
there's no lens] and that would make a great aperture mask. Of course,
then
i'd need another lens cap for the hole i just made. I think i'll make
one
out of a sheet of cardboard and try it on Mars tonight.

-Florian