Custom
Sized Three Aperture Masks
When
observing close objects such as tight double stars with a
Newtonian telescope, the secondary mirror holder's "spider
vanes" can distort the image. Aperture masks eliminate
spider distortions. Varying size openings provide brightness
choices for cleaning up and toning down the image. Aperture
masks increase the effective focal ratio yielding higher contrast
views: a masked 10" f/6 becomes an unobstructed 3"
f/20 telescope; wonderful for brighter detail targets such
as Jupiter and its moons, Saturn, Mars, our Moon, and of course
tight double stars or pairs with wide magnitude deltas.
"My
first views of clean crisp star images were outstanding. Using
my 10" Newtonian on double stars, the secondary spider
created distortions. Using the mask, I can see why refractor's
unobstructed views are so desirable. Alberio showed small
perfectly circular clean airy disks with pure colors. Swapping
the aperture cover, I found stopping down to 50% was best.
Epsilon Lyrae's individual magnitude differences became obvious
showing exquisitely clean separations with perfect individual
airy disks." - Jerome G.
1/8
" thick flat black acrylic; rigid, lightweight and durable.
Aperture masks have three openings: 100%, 75%, 50%.
100% mask size calculated: edge of primary to edge of secondary.
See
a sample mask diagram at left.
Adheres securely to tube using Velcro dots.
Two
opening covers are included.
Shipping
up to 19.5" diameter: US/Canada $15/$20.
Shipping up to 23.5" diameter: US/Canada $18/$25.
Larger sizes or shipping to other destinations quoted upon request.
