First Look At Ed Grissom's "Pinball Machine"
Posted 22 June 2010 - 11:24 AM
Based on looks, this is probably the last telescope you would want to look through at a star party, but then again, that's actually true. It is the last telescope you will look through at a star party. During the Carlton Flat days, many planetary buffs would bring their best telescopes up. Charlton could drop to .7 .6 arc seconds or less. They would cut each-others throats. Grissom just did it quite calmly. Hey there Danny, how-ya doing? I would ask, soooo ah? Did you come to destroy us Mr. Grissom? Grissom is a humble man and being on the west coast, we are sometimes treated to memorable views. This is a first glance of the actual telescope Grissom used in this SHOOTOUT
The photos from that review were actually never shown, since this is the actually fan configuration Grissom used on all occasions. I felt like a dog without a bone. I've tested many optical telescopes from the 60" at Mt. Wilson to 8" to 10" apos, to 20" Dobs with the highest quality optics. Out of all of them, This piece of junk produces the finest planetary images I've ever seen in any telescope regardless of design. It's almost bizarre in a way. I asked Grissom if I could share these pics. It houses a rare Steve Kennedy 13" F-6 with all the trimmings, but most of all, it obeys the basic fundamentals of what makes you walk away wondering. How does it make the planets look like that? The true space ship effect? It's basically a "Pinball Machine". That's the best way to describe it. Sure it's got great optics and some may believe that's what it is, but it isn't just that. It's simply the way the Ed Grissom executes the total design.
The mirror hangs out the back, mainly because he uses the same tube for several mirrors he owns, but it also continues to run air through the tube. If you are standing in front of it, you will feel the air flowing in your face at all times. It's a totally aesthetic viewing experience. Notice how the fan is resting on pedestal and simply positioned behind the telescope. And for all those skeptics who read math figures about aperture rules and curved spiders are not as good as straights. You'll be putting your clip boards in the closet. Enjoy.
Posted 22 June 2010 - 11:43 AM
Posted 22 June 2010 - 11:54 AM
Posted 22 June 2010 - 12:05 PM
This is a first glance of the actual telescope Grissom used in this SHOOTOUT
^^^^^ Best. Thread. Ever. (Well, for those interested in building planetary reflectors.)
I've tended towards the opinion that although "pretty" scopes look nice, it's what you see in the eyepiece, ultimately, that matters most. If you're not happy with that, who cares about the external aesthetics? Thanks for those pics, Daniel. Wish I could get out west to take a look through that scope!
Posted 22 June 2010 - 12:15 PM
Posted 22 June 2010 - 01:15 PM
my question is... why is it a dark reflection?
Posted 22 June 2010 - 01:21 PM
Posted 22 June 2010 - 02:32 PM
Posted 22 June 2010 - 03:04 PM
Perhaps the secondary is sized so marginally small as to barely see the primary's edges?... or any light sneaking past its edges?
Or perhaps there's an optional drape, backing, or blackened backstop set directly behind the scope while its viewing?
If its truly a "planetary instrument", its probably not used in a careening-all-over-the-sky manner... like a DSO or multi-porpoise scope. It likely sits there for hours, leisurely tracking a single planet while the viewer sketches or directs traffic.
Posted 22 June 2010 - 04:41 PM
A lot of light can come through the back. This is often a big concern with dob builders. Why isn't it here? - j
There should be a post mirror baffle so that the image plane in the focuser is not illuminated by anthing from the back end of the telescope. That is you should not be able to see the ground from the focuser with the telescope pointing anywhere near zenith.
Posted 22 June 2010 - 04:46 PM
Posted 22 June 2010 - 05:43 PM
Posted 22 June 2010 - 05:49 PM
This is a great reminder that pretty has nothing to do with great views.
ummmm.... cant tell a book by its (outside) cover?
Posted 22 June 2010 - 05:53 PM
Ever think he doesn't view in light polluted skies like most us?
Actually, i believe he observes from the hills above Los Angeles- Mt. Wilson? Excellent seeing... LP off the scale.
So they observe planets, instead.
Posted 22 June 2010 - 06:24 PM
Well said, and good advice. 100%!
Posted 22 June 2010 - 07:04 PM
In Summary: (arranged in order of importance according to my own opinion)
- High quality mirrors
- Sufficient multi-point mirror cell supports (secondary too)
- Perfectionist collimation
- Constant active fan cooling during all observing
- Solid tube of a thermally stable material (fiberglass / sonotube) that acts as chimney to flush thermals out and away from light path
- A significantly over-sized tube diameter (to further facilitate the above) and allow light to enter without passing through so many thermal currents associated with tube walls
- Ultra thin curved spider made in his own workshop (due to no commercially available curved spiders being created with the requisite dimensions that provide stability and thinness)
- Solid EQ mount for tracking of target
Posted 22 June 2010 - 10:12 PM
Thanks for those pics, Daniel.
No problem. You're welcome
Posted 22 June 2010 - 10:20 PM
Why does the mirror look un-aluminized in the image shot looking down the tube?
I haven't asked Grissom if the mirror is aluminized or not at this time but just in case you are wondering, there are sometimes certain angles in certain light where you can almost see through the optic even when there is a coating on it.