Sky Designs

I hope I have the name correct, but does anyone remember these Dobsonians? They were crude by today's standards, but a real step up from the Coulter closed tube Dobs. The first one I recall seeing was a 17.5"(?) owned by a vacuum cleaner store owner from Harlington TX, out at TSP, in the early '80s. The diagonal mirror was "glued" to a piece of dowel & adjusted by 6 bolts in a metal "spider of sorts".

Actually, they were very nice looking scopes for their time.

Darian Rachal said:

I hope I have the name correct, but does anyone remember these Dobsonians? They were crude by today's standards, but a real step up from the Coulter closed tube Dobs. The first one I recall seeing was a 17.5"(?) owned by a vacuum cleaner store owner from Harlington TX, out at TSP, in the early '80s. The diagonal mirror was "glued" to a piece of dowel & adjusted by 6 bolts in a metal "spider of sorts".

Actually, they were very nice looking scopes for their time.

Darian,

Our club owns two 18" Sky Designs. One has been heavily modified and work is in progress on the second. I just got the upper cage assembly for a 15" Sky Designs from a friend today. It needs some work.

One of the biggest drawbacks to the design is the secondary adjustment. The secondary is mounted on a large wooden dowel, which is inside a larger thick walled tube. Screws through the tube go against the dowel for adjustments. Argh!

Clear skies, Alan

Hello Darian,

My good observing buddy has a 14.1" Sky Design with a wonderful primary mirror. The scope has passed through a couple of club members hands since it was built. It did indeed have a very annoying secondary mounting system. The primary mount was not much better with three triangles glued to a leather cover. But the woodworking is very solid.

After one Copper Breaks Star Walk when the wind actually knocked it over and broke the focuser, we decided to do a major remodel of the scope. It lives on with a homemade curved secondary support, a Moonlight focuser, four quick setup truss poles, new ventilation holes in the primary box, a new primary mirror mount with four collimation adjustments in front of the mirror, and fitted with an Argo Navis.

The scope keeps working--a real deepsky workhorse. As I said a wonderful mirror.

Daniel

I bought a 18" Sky Designs new back around '90. Still have it.
The diagonal adjustment system (wood dowel centered captured
by 8 screws) is "simplistic" but I find it works well and is
very accurate. The large distance between the front and rear
screws makes fine adjustments possible. An interesting feature
of this design is that you can fine-tune the secondary
sideways offset. You can also adjust the position towards / away
from the primary without upsetting the other adjustments.
The secondary support may look cheesy, but its one of the best
designs I've used. I just got done upgrading the diagonal mirror
with a flatter one (0.05 wave PTV vs the old 0.25 wave PTV) though
the change-out is a bit laborious making a new "broom stick" and
gluing it accurately to the new mirror, etc.

The truss is surely a bit time consuming to field assemble with
wing nuts, wrenches, etc. But unlike some other Dobs I've owned,
it is solid as a rock. Some other scopes I spent months and
years trying different ways to stiffen the "EZ quick" truss
assembly so the collimation didn't change all over the sky.

One big upgrade it needs is some ventalation in the mirror
box. I think thats the biggest issue with the design -- the
mirror is totally enclosed in the deep mirror box. It needs
a couple holes near the back with some fans. Next on my
to-do list....

I still think its one of my better astro-purchases, even if
the design is a bit out-of-date.

I had a 14.5" f/5.5 with a Galaxy mirror. I too was bemused by the secondary arrangement, but I found it worked well enough. The lack of any primary ventilation was a big problem. This was made worse by the presence of a large amount of lead in the mirror box to balance the front end.