Interesting Test

[W2DU]

Interesting, Tom, didn't know you are an astronomer too!

Yes, I knew Porter designed the Hale scope. In fact, the mirror in Dad's Daytona scope came from the same Pyrex pour as the Hale mirror. Incidentally, you left the 't' out of Stellafane, hi.

The attached pic shows the scope with its shelter in the background at the Daytona location. The shelter is on rails, which allows it to be moved over the scope when not in use. A similar shelter was used in the Stetson U installation.

Walt

[K1JJ]

Walt, what a classic picture that is!  The old car, the scope using an old car rear end as its equatorial mount...

OK on the shelter with wheels, riding on the rails. I did the same for my binocs, though after a number of years the shelter started to rot from exposure. But it's good to make it easy to "get on the air" or we will come up with excuses for not using it.

Looking at the mount, do you think there is are some blind spots in motion when looking at the zenith? I wonder if the bottom of the scope would hit one of the concrete piers at certain orientations?  That may be the disadvantage of the English mount vs: a single pier, I dunno. But stability is certainly more important. My siderstat has a blind spot at the zenith when the flat is looking directly at the parabola.

Anyway, those old pics you posted deserve to be in the display up at Stellafane in the club house. They look so much like the Russell Porter era. A comment that Russell actually inspected the scope would put it over the top...

T


Here's some shots of my scope. Notice the military shelter where the eyepieces are for viewing comfort from the bugs or cold.  The 28" Russian Astro-sital flat is on top of the roof, controlled by a computer and steppers. The 22" parabola is on the 18' tower looking down. Light enters the flat, reflects up to the f 8.5 parabola and then reflects down thru the 6" hole in the flat to the eyepiece inside the shelter. Except for a blind spot at the zenith, I can cover the whole sky from horizon to horizon via remote control inside the shelter. (and except for treeline)  The flat sits on a homebrew alt/az mount. It uses a turnstile bearing from a large crane for the az..

Right now I'm working on mapping the sky for error correction pointing. This will make it accurate to about 2-3 arc minutes across the sky. Mel Bartels supplies the stepper software.

[W2DU]

Tom, I'm pleased that you find my pics of interest, and that they might be useful at Stellafane. I have quite a number of them, more than I posted, some showing details that aren't visible in the ones I posted. If you think the people at Stellafane would like to have copies of them I can make a CD that will hold all of them. I'll leave it to you to determine how I should handle it. Incidentally, I took all of the pics. Those taken in Mt. Pleasant, MI were in 1938, those in Daytona were taken in 1940 while I was working at WMFJ, and the ones at Stetson U, in DeLand, FL were taken in 1962. You probably know that my home is in DeLand.

In the meantime I'm recalling a little more about the subject. I'm sure you're aware of Albert Ingalls' book, 'Amateur Telescope Making'. In addition to the book he also had a monthly column on the subject published in the Scientific American. In one of his articles he described the scope my Dad built. It's been more than thirty years since I looked at the copy containing that article, but if I remember correctly it was in the October 1938 issue. I'm in Mt. Pleasant, MI, now, the home of my alma mater, Central MI University, and its library has copies of the Scientific American. At this point I'm not physically able to visit the library, but I'll try to get some help in finding the article. If I do I'll post it on the Forum. If I can't get a copy perhaps you have access to a library that would have it. If this fails I'll be back home in FL in November, where I can dig out my copy and scan it.

Concerning the possible blind spots with the equatorial mounting, I don't know whether there were any such problems or not--never heard that that there were. However, considering the zenith angle, I know the piers were constructed sufficiently high so that the bottom end of the scope would clear the ground underneath it when positioned vertically.

Your setup is amazing! It's been a long time since I delved into the mechanisms of telescoptics, so some of the explanation of your pics is a little over my head. I've forgotten how the flat plate enters into the picture. Are you saying the flat plate views the sky and reflects the view up onto the parabolic mirror, which then focuses the image down through a 6" hole in the flat and onto the eyepiece?

What I don't understand is how the mirror follows the line normal to the flat plate as the flat plate scans the sky if the mirror is stationed on a tower ? I must be missing something.

Walt

[K1JJ]

OK Walt -

What you might do is look up Stellafane and go to their website. Find the email contacts and send them a few samples of the pics you posted here. Be sure to say Russell inspected one of them and your dad corresponded with him. Let them go from there.. They will probably be very interested and look to put some copies in a permanent place for future generations of tele-makers. They really do have a love for history in that club.

You have the light path correct for my scope. The parabola on top stays stationary. The flat moves and is always directing light into the parabola. As you can see, unless the flat is looking at near to the zenith, only a fraction of the light will hit the parabola.  This is why the flat is bigger than the parabola. Fortunately, the majority of light is available in the higher angles of the sky and tapers off at the horizon where the seeing is poor anyway.   Picture it like using a standard refractor scope that is looking at a large flat mirror 18' away. The light is uncolimated until it hits the refractor (or parabola), so the flat mirror can be far away. Only when the flat takes on very acute angles to cover areas away from the zenith does the light quantity taper off.  I figure the "effective" scope aperature goes from about 21" to maybe 18" at the horizon using this method.

Porter's turret used a moving frame with the flat tracking the parabola, whereas my parabola is stationary and makes use of a computer which permits a simpler alt/az mechanical structure for the moveable flat. Just imagine a 22" and 28" set of mirrors on a moving 18' frame. It would be way out of my league.  The advantage is in the winter I have heat in the shelter and have it insulated enuff so the seeing is FB. Also no bugs or ladders. I sit and listen to jazz while watching. The computer software will do a "grand tour" where it will cruise the Messier 100+, galaxies or whatever automatically.  The software is the whole heart of the system. I've have  maybe 10 eypieces of various powers for planetary to wide field work.

T