Custom
Sized Three Aperture Masks
"Testing
this new aperture mask on my 10" f/5.7 Dobsonian, I was
literally stunned at the clean crisp star images. Having observed
(several hundred) double stars over the past two years (2019-2021)
at full aperture, dealing with a secondary spider creating
spikes and other abbreviations, I can see why observers love
refractors and their unobstructed views. Using the mask was
a revelation. Alberio showed small circular stars with clean
airy disks, and pure colors. I found stopping down to the
50% mask was best, and it was so easy to change mask sizes.
Epsilon Lyrae (Double Double) revealed its magnitude differences
clearly with clean separations and perfect individual airy
disks." - Mark W.
When observing detailed objects such as double stars, the
secondary spider of your Newtonian will create spikes in the
image that can hide detail. An aperture mask will "remove"
those spike distortions. And, having varying size openings
will afford you more choices in brightness for achieving separation
of otherwise impossible double star splits. This is really
a function of increasing the focal ratio: A 10" f/6 masking
to a 3" opening becomes an f/20 telescope - increasing
contrast in an "unobstructed system; wonderful for brighter
detail targets such as Jupiter, its moons, Saturn, our Moon,
and of course bright tight double stars or tight pairs of
widely divergent magnitudes.
1/8
" thick flat black acrylic; rigid, lightweight and durable.
Aperture masks have three openings: 100%, 67%, 50%.
100% is largest possible opening based on primary and secondary
size.
See
this sample detailed Aperture
Mask Diagram.pdf.
Adheres securely to tube using Velcro dots.
Separate
acrylic covers for two openings are included.
Photo
is an original single opening aperture mask.
Shipping
cost quoted upon request.
Price calculated by square area, $0.1465 per square inch
rounded to nearest whole dollar. Pricing examples:
|
Tube Outside Diameter
|
Sq. "
|
x
|
Price
|
|
8"
|
64
|
$0.1465
|
$9.00
|
|
10"
|
100
|
$15.00
|
|
12"
|
144
|
$21.00
|
|
14"
|
196
|
$29.00
|
|
16"
|
256
|
$38.00
|
