How Many Of You Ever Owned A Coulter... back in the day

[Paul Chuck]

Hi star drop et all ! I'm New to this Forum and glad I found it ! I believe I'm the guy you reference, live in Springwater, NY and indeed have the 29-inch up and using it. The cell is from AS 27-point whiffle tree and I built the scope as a pretty standard truss AS-like but beefed up because it is in a dome (Luxury!) The BIG improvement I made was to add 12 force-actuators around the mirror judiciously-placed twixt the tree triangles to mechanical ground. I invented that and call it the "Tweaker Clock." It comprises simple (pull) springs tuned with wing nuts. These pull on the back of the mirror against mech ground making it "heavier" (AKA mass-density) where pulled. My intent was to tweak out axial (global) astigmatism just by racking thru focus as my son twisted on the wing nuts. What it does is to pull the shorter astigmatic surface radius Longer to match the longer one. Long story short - It works magnificently! Very objectionable astigmatism reduced to undetectable with only a blush or (Zernike) Trefoil left. The mirror went from depressing to Very Good! I use it routinely at 400X+ with the brightest stars showing only slight triangle shape and the dimmer ones looking like dots. Central star in the Ring always easy. Umm...I got it recoated at EMF (Evaporated Metal Films) which is close to here and high-quality EnAl, fair price and personable staff. I LOVE this scope! I'm on 16 acres in Upstate NY Rural Hills - surprisingly DARK for NY! Other equip: 20+ TV eyeps, 3ea ITT Gen 3 Night Visions, JMI RB6 and RB16, APM 100/90 deg Binos, Zeiss 20x60 IS Binos. I had another Coulter 29 but sold it off. Jim Jacobsen knocked himself out trying to produce the 29s but lost his shirt on them. Fortunately, mine ONLY suffers astig, but I found this solution which works magically and holds figure very stable! The mirror is otherwise very smooth and the correction (parbolization) is text book perfect. I’d like to post pictures of this stuff if there is a way. Tom Dey pics--->>> tom at 29.jpgtweaker 1.jpgtweaker 2.jpg

Hi Tom,

I am the first person to have ordered a 29'' Coulter mirror (according to Coulter). During two years, roughly every month, Mrs Dorothy Jacobsen replied to my claims not to worry : the mirror would be shipped next month to France where I am living. I remember I was afraid of an upcoming bankruptcy of the company. But as I was living far away, it was difficult and expensive to hire a lawyer to recover my money. Then, I noticed in the reviews Astronomy and S&T that some 29'' have already been sold and were used. I though wrongly that as I was the first to order a 29 '' , I would be the first to get one.
Fortunately I had then a bright idea. I made to the editors of Astronomy and S&T a copy of the whole correspondence I had with Mrs Jacobsen, asking them to stop Coulter advertising. By return mail, S&T wrote me that they have sent a telegram to Coulter company asking them to ship the mirror within 15 days.

Very efficient indeed. The mirror was in France 3 weeks later. Since the mid 1980 the mirror is installed on an offset cradle mounts which allows to point the polar. In addition, that mount is very stable. In my telescope, the counterweight is about 1000 kgs. Very kindly, Jean Texereau has calculated for me a cell with 15 astatic levers. The result is far from perfect but good up to 150x magnification, due to the imperfect optic.

May be your idea to add fixed constraints on the mirror to correct its optical surface could help me a lot.
Where and how do you glue the 12 springs at the back of your 29'' ?
Please, perhaps could you send me a scan of a layout of your cell and pics on details of the cell ?

[carolinaskies]

I had one of the old 'box' style Coulter 13.1" about 16 years ago. Sold it due to the heavy weight and having an LX200 and acquiring a 16" Starfinder mirror for a future truss project. Sadly I lost my job and had to set aside regular observing and the truss project.

The sling style box setup was notoriously bad for having to colimnate and for the mirror moving slightly as you went vertical. Still it was a fun telescope for fuzzies that smaller scopes just can't reach.

Fortunately for me a couple weeks ago I actually found another 13.1, this time a red tube version. Found it in the local thrift store of all places! I have yet to use it for first light to check optics, but I will try it out next month as our southern skies stabilize with the temperature drop.