I forgot to mention your 6mm and 12mm probably have a trademark that will tell you the maker like this:
Posted 05 August 2014 - 05:02 PM
My eyepieces don't have anything like that on them and their boxes give no hint either.
Posted 06 August 2014 - 09:08 AM
I heard a story of why some of the Coulter mirrors in their Dobs weren't so good. Coulter was looking for away to quickly test their mirrors and get them pretty close to a perfect parabola. I heard that Coulter was using a highschool kids to build the scopes and make the mirror so they wanted a straight forward test that was easy to understand. So they used Mobys Inverse Ronchi ratings to test their mirrors vs more time consuming and error proven Foucault test. How the Mobsy test works is that the Ronchi grating doesn't have the usual straight lines but three lines that are curved inward by a calculated amount. The grating needs to be placed an exact distance inside the radius of curvature of the mirror and when the mirror is a perfect parabola the lines are dead straight. The test works well when done correctly and Willmann Bell still sells the gratings. What I heard happened was that the gratings weren't being placed at the correct distance and that results in the mirrors being undercorrected by a large amount.
I've own13.1" red tube unit since the mid 80's and while the optics aren't perfect I have had many enjoyable hours doing deepsky observing with it. For the $499 I paid for it new, it was great bargain.
- Jon Isaacs likes this
Posted 10 August 2014 - 03:23 PM
Whats interesting about the brown tube is the tube is open and the cell allows air movement. The red and blue tubes I've owned do not have this feature.
I have only seen one brown tube (mine) so I'm not sure if it came from the factory like this but it appears to be original.
Posted 10 August 2014 - 03:28 PM
Here is the whole telescope. Coulter Odyssey 8 "brown tube".
Posted 10 August 2014 - 03:36 PM
For reference here is a red tube cell. Notice the cell does not allow air flow past the mirror.
Posted 10 August 2014 - 03:47 PM
And the blue tube. I rather prefer the blue tube system of having a "tailgate" like a pickup truck. This idea originally came from John Dobson. The main purpose was so you could test your uncoated mirror in the tube and quickly open the tailgate and scrub off a billionth of a inch zone with your thumb and just as quickly see the results.
What I like about the tailgate is you can leave it open to cool the tube and have the mirror cooling to ambient and install it in seconds. Index marks on the cell and mirror edge allow this procedure to be done without even touching collimation most of the time.
Posted 10 August 2014 - 04:04 PM
Close up of the 9-point flotation cell in the 17.5" ( I really miss this scope ) The mirror is centered on the cell and held in place on its edge by the white sling in the picture. I have marked the cell index with a red 1 in the picture. The mirror edge will have the mating index mark.
Edited by actionhac, 10 August 2014 - 04:05 PM.
Posted 11 August 2014 - 01:04 AM
What years were the Brown tube scopes produced?
How well did the blue tube scopes hold collimation? It seems to me that I would want to upgrade the mirror cell.
Edited by TCW, 11 August 2014 - 01:05 AM.
Posted 11 August 2014 - 05:24 AM
I remember, a few years ago, there was another thread on the brown tube Odyssey.
Posted 11 August 2014 - 10:23 AM
I remember, a few years ago, there was another thread on the brown tube Odyssey.
Wow Rich your right.
I just used the search box in the upper corner and typed in "Coulter brown tube" lots of stuff appeared. I don't remember the search function working so well with the old Cloudy Nights.
I want to go back and read all those posts when I can.
The blue tube holds collimation fine. I never had any problems with the collimation changing anywhere between zenith and horizon, gravity kept everything in place. It worked surprisingly well considering it is f4.5 and the cell is not really what you would expect to see in a scientific instrument.
I have a very thin 15 inch mirror I need a cell for and I was told to use Bubble Wrap, the size with about 1 inch air cells. I said BUBBLE WRAP! then I thought why not! so I'll try it.
Posted 12 August 2014 - 03:24 AM
Now that sillyness is over, lets get back on track to the points asked....
Coulters were fairly typical of inexpensive scopes, Some were good most were OK 1/2 wave some were terrible.
They used a thin mirror that if not mounted properly, would warp and produce horrible images.
Many were figured properly, so if yours is not giving good images, scrap the factory mirror mount (a piece of Plywood with dobs of adhesive and a huge Radiator hose type clamp around the mirror edge, squeezing it 1/2 on the wood and other 1/2 on the glass)!!!
The secondary mirrors used were" ALL over the place" in quality, again Glued to an angle iron bar spider!
Many times things were not centered properly in the light path. These were designed as a Deep Sky Light Bucket, and not a Zambuto Planetary Scope!
With the 13.1 and 17" you could make an off axis Planetary Mask, about 4.5" clear on the 13 and 5.5 or 6" Clear on the 17" These provided quite superb Planetary results
as they were unobstructed light paths and worked like a fair APO!!! The Red series up to the final 18 months of Company operation were superior to the early Square box
versions. Mostly due to the mirror just flopped in the base box and not centered!!!
I found a users manual/info packet for the Coulter series if anybody is interested..
PM me... Those are impossible to find, because they just got pitched.... Coulter was pretty much a one trick Pony operation with the owner doing everything mostly!
I still find it amazing to number of scopes he got built!
If you can find a decent 17" for about $900.00 they are a steal!! Plus the Magellan 1 and 2 designed for the Starfinder Dobs fit right on!!!
they are not Y2K BUT the DSO's and Digital setting circles are right on so they work just fine! The trick is looking back to a year with the same
Day and month dates the same (about every 5-7 years or so).... I used this to great success with my Compustar 14 before I bought the Y2K chips and installed them.
Posted 12 August 2014 - 05:24 AM
I had the 10" Compact back in 1982. It give a coma filled mushy view.
Posted 12 August 2014 - 07:50 PM
I had one of the Compact 10's as well. 10-4 on the coma, mine was mushy too till I put a new
Primary holder and Spider in it, but that cost 1/2 as much as the whole scope..
It sure blew away my C8 for Deep Sky objects and could be set up and used in 2 minutes!!!
Everybody should have one at some point!
Love this Thread, brings back SOOOOOO many memories!
With that scope I found Girls liked Astronomy, or, at least the Blanket on the ground
looking up at the sky ( ) Only problem was she kept taking my mind off Astronomy..
Not that a 25yr old Guy minded Much! ( )......
Posted 13 August 2014 - 08:04 AM
Great Topic! Anyone familiar with or have built a scope using optics from their custom line of mirrors? Back in 1986 I obtained a 14.25" f/7 set and built a scope using these optics. It was my first homebuilt system that required a small step ladder to get to the eyepiece especially when it was pointed to anything near the zenith. At the time I considered that to be a minor inconvenience because optically it was excellent using orthoscopics especially on Jupiter. A few years later I moved and had to dismantle the system. The mount was a home built industrial quality pillow block type that was taller than it should've been and made from 2-inch steel pipes and 1/2" thick steel plates. Eventually I got rid of that mount and put the optics away , eventually selling them in 2005.
However , I've never gotten past the excellent views provided by that first scope so I obtained another set. The plan is to build another 14.25" scope using these optics. I hope these are as good as was the ones that were in my first scope. I got this second set in 2009 and have been keeping them in storage until I'm ready. This first view (2009) was taken of me after I opened the package. Coulter Mirror.jpeg3.jpg 142.55KB 28 downloads
- terraclarke likes this
Posted 13 August 2014 - 08:57 AM
That's cool that you found another mirror. I remember photos in S&T years ago of Ralph Nye's 14.25" f/7 on custom GEM. I believe he used Coulter optics in that one. Made my heart beat fast just looking at those photos, it was the "ultimate" telescope in my mind.
Posted 14 August 2014 - 06:39 PM
I still got me a notion the brown tube was the "Western Ranch Special" I reckon.
Edited by actionhac, 14 August 2014 - 07:03 PM.
Posted 16 August 2014 - 03:45 PM
- mdowns likes this
Posted 16 August 2014 - 07:51 PM
Great collection of instruments from the "good old days". I think the 70's were just about perfect and the 80's were not far behind.
It looks like you poured a concrete pad for the blue tube, very nice.
Posted 16 August 2014 - 08:41 PM
Here's my 10 inch blue tube. I still own this astronomical marvel.
Edited by actionhac, 16 August 2014 - 08:42 PM.
Posted 16 August 2014 - 09:07 PM
there were some very nice coulters and not so nice coulters. However, I always found with a mask of about half the mirror diameter if the optics were halfway decent this would turn into a great unobstructed scope.