Welcome to JP Astrocraft,
my little astro manufacturing
company. I'm John Pratte. I spent over 40 years as an
for a large manufacturer. I recently retired and can now
devote more time to my telescope making activities. I've made
telescopes for over 50 years, including mirrors up to 20
In my search for the
perfect size personal telescope, I designed and built a 16" F4 which
became nicknamed the "Sweet
Sixteen". Well, actually I built four.
are currently available for sale. The 16" aperture provides
enough light gathering, and the F4 optic allows an eyepiece height of
about 62" at the zenith. The compact design is several inches
smaller than most other 16" scopes. Refer to the telescopes
page for specifications and construction details. You will
see why I am proud of the Sweet Sixteen. It is
available with a mirror from Mike Lockwood
or Dick Wessling.
For the discriminating
observer desiring more aperture than the Sweet Sixteen, we are
introducing The Twenty-Five. Same fine craftsmanship, more innovations.
Click on The Twenty-Five tab to see all the details.
Twenty-Five is available in (from left to right) an f/5, f/4, and now
"No Ladder" f/3 configuration. All feature Lockwood primary and
matching secondary optics.
20 Inch Tip-out Mirror Cell
I have also built a number
of custom mirror cells over the years.
My cells mount the mirror on it's own support framework and use a
pivoting support at the mirror edge to prevent binding. I do not
believe slings or glued on supports are the best way to support the
edge. The larger cells feature spherical bearings at the
support triangles to reduce slop in the pivot. The sweet
sixteen cell uses channels that are shaft mounted for the levers,
further controlling slop. This frame is spring loaded with
stainless Belleville washers to the mirror box frame. This construction
results in a strong, easily collimated cell that resists collimation
change as the scope is moved while properly supporting the precision
I was fortunate
enough to have acquired a reasonably complete machine shop for my
telescope making activities. It is great to be able to make
the proper part for a scope rather than having to adapt hardware store
or commercially available parts. See my shop section for my equipment and custom projects for pictures
of special stuff I have done.
Custom Mirror Cells Custom