Sized Three Aperture Masks
observing detailed objects such as double stars with a Newtonian,
the secondary spider distorts the image creating spikes and
unevenness. 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.
first views of clean crisp star images were outstanding. Using
my 10" Newtonian on double stars, the secondary spider
created distortions. Now with the mask, unobstructed views
showed wy refractors can be so desirable. Alberio gave small
prefectly 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 clean separations and perfect individual airy disks."
- Mark W.
" 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.
a sample mask diagramed at left.
Adheres securely to tube using Velcro dots.
opening covers are included.
up to 19.5" diameter: US/Canada $10/$15.
Shipping up to 23.5" diameter: US/Canada $15/$25.
Larger sizes or shipping to other destinations quoted upon request.