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| AT LAST! The NEW: 20 inch f/3.55 is operational and is shown here, September 1st, 2011, at the Oregon Star Party (OSP), | ||||||
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| 20 inch f/3.55 Dobsonian | ||||||
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| 2011 OSP Walk-A-Bout | First Operational use August 26th, 2011 |
First Light January 7th, 2011 5:40pm-Cresent Moon |
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| Double Ring Cage & Focuser Board Support Bridge | Dave Danskey & Scope | Nate & Scope trial dry fit |
| The Telescope was
designed by (me) Greg Babcock and Nate Currier of Aurora Precision
and built by Aurora Precision out of Aluminum
and Plastic. Many components were "off the shelve" products
including the Truss Clamps, The Astro-Systems Spider features
a heated Secondary Holder.
The Mirror is 1-3/4 inch thick Pyrex made by Swayze Optical. This Telescope was built to replace the 24 inch. The 20 has about 30% less light gathering power, but with the new "brighter" Coating and new eyepieces, I could detect little difference even viewing through smoke filed skies. The goal with the new scope was to increase ease of use and mobility. It was patterned after the 12 inch Traveler. A lot of the anxiety comes from transporting the scope. The 12s hard Baltic Birch Mirror Box shell protects the scope during transport. The 20s aluminum case does the same. The 20 is designed to go to more Star Parties more often. The 20's heaviest piece is 7 pounds lighter than the 24s, but it is also physically smaller (22.25 inches square), adding to the ease of handling. |
To
assembly, the Mirror Box can be lowered between the Alt-Bearings
onto a guide track. The Alt-Bearings can be locked into position to
ease assembly. This saves wear on the back. The 24s Mirror Box
placement and removal was a "dead lift" operation. The height of
the 20 permits attaching the Cage, and viewing, without a ladder.
The 24's Cage required a ladder to assemble and view through. The
Mirror box easily goes through a narrow RV door and travels well in
the small vehicles. The Cage design features 2 thin "Alucobond" rings, with Aluminum spacers. Tension from the Spider gives the Cage torsion strength. This strong Cage is attached directly to the Trusses. A del-ran Bridge between a Truss and Focuser Board, supports and stabilizes the Focuser Board. A 20.25 inch Light Baffle just in front of the Primary Mirror and Cage rings only 21 inches in diameter, add contrast to the view. The physical Size of the Scope is closer to that of an 18 inch. The Telescope weighs 114 pounds. Last updated: September 10th, 2011 |
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| 12 inch f/4.9 Traveler | ||||||||
| First Light-March 30th, 2008, 9:00pm - Orion Nebula | ||||||||
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In August of 2006 while sitting in the Atlanta Airport, waiting for the
connecting flight to Portland, I began to sketch the new Traveling Telescope
design. We had just completed our Argentina trip. Lesson
learned from traveling with the 10 inch would be used in the new design. |
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| 12 inch f/4.9 Traveler | ||||||||
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This Traveler vs. a Refractor |
More Improvements: |
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| Front view | The Carry on Box |
At 2009 OSP "walk-a-bout" next to Dave Powell's 12.5 inch Telescope Video on the 12 inch. |
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| The TeleVue 76mm APO Refractor & Takahashi Teegul Mount | ||||||||||
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TeleVue 76 APO on with Coronado H-Alpha Solar Filter on Takahashi Teegal
Mounting |
The 76mm Imaging the 2009 Solar Eclipse. The Teegul Mount has
Counter-weights/Shaft and Latitude Wedges removed for Alt-azimuth
configuration for Shipboard use. |
Takahashi Mount Configured as an Alt-azimuth
for ship board Eclipse Imaging. TV85 & TV76 in Pelican 1450 & 1510
Travel Cases |
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The
TeleVue 76mm APO Refractor (aka TV76) The 76mm is the smallest of the 3 Telescopes, but gets the most variety of assignments. It was fitted with a Coronado H-Alpha Solar Filter. The 8-24mm Zoom Eyepiece gives 20x-60x for Solar Viewing. The APO design makes the 76 excellent for night viewing including Planetary and "Rich Field" viewing. Motorized Focuser Though I am not a serious "Imager", for what imaging I do, Motorized Focuser is essential for fine tuning the focus. I installed a JMI Motor for the Focuser. Because I have motorized the Focuser, I use the lighter 1.25 inch Eyepieces. Unlike with a Dobsonian, the upward aiming of Refractor creates a lot of load on the focuser when the Telescope was aim toward the Zenith. Heavy 2 inch oculars, caused the focuser to grind on the O-Ring "clutch" and wore it out. Commonly, the focuser shaft simply spun without focusing. Eyepieces for Rich Field (RFT) Use Not using 2 inch oculars is a visual sacrifice after viewing through Ethos Eyepieces. I use a 1.25 inch 30mm Takahshi Eyepiece. It weighs only 6 ounces, has a 52 degree Apparent Field of View, gives 15x and gives a 3.25 degree True Field. I also use the 24mm Panoptic. It provides a nice 68 degree Apparent Field and 3.4 degree True Field at 20x, enough to identify the Ring Nebula. But it is heavier (8.4 ounces). It also has a smaller Exit Pupil (3.8mm vs. Tak 30 4.8mm), Attaching the 0.8x reducer makes the Telescope an f/5.1. This gives a field in excess of 4 degrees. The Veil Nebula (2.9 degrees) is a "benchmark" object for RFT use. Attaching Accessories I like the ease of attaching accessories. The Treaded Dew Cap for Mounting the Solar Filter. I prefer this over the nylon threaded screws pressing against the Dew Cap. Also Mounting holes on the "Clam Shell" Tube Clamp allowed me to mount the Solar and Red Dot Finders with ease. Traveling The 76mm is the size of the old Pronto and fits in a Pelican 1450 case. It went to The Venus Transit in 2004 and the Solar Eclipse in 2009 to image these events. Though more Aperture would be preferable, Traveling Telescopes grow in weight and size when being carried onto an Airliner. The compact size and reasonable weight make the TV76 highly tolerable. The Pelican 1450 can fit under the Airliner Seat. |
The Takahashi Teegul Mount This is the only Tracking Mount that I own. I acquired it in 2003. It is accurate, compact and an excellent traveler. I had Solid Aluminum "Latitude Wedges" machined of 30 & 45 degrees. They are interchangeable depending on the Telescopes travel destination. They can be stacked to give Latitudes from 15 degrees up to 75. Latitude Fine tuning is achieved by adjusting the Tripod legs. The "C" Cell Battery pack was replaced by a lighter "AAA" battery pack. For the 2009 eclipse, the counterweight shaft and Latitude wedges were left off to make the Mount a lighter "Alt-az" since ship board observing did not require an Equatorial Mount. Just one month after purchasing the TV85, I learned that the TV76 was coming out. I ordered one at the September 2001 Mt Bachelor Star Party. I eventually received number 31. The 76 is 3 pounds lighter than the 85mm and fits snuggly into a Pelican 1450 Case. Owning 2 TeleVues was unintentional. Actually, for a short time, I owned 3 including the 70mm Pronto. The 70mm was eventually sold. For a while, the 85 and 76 both went to the same Star Parties. The 76 was used for Solar and the 85 was used at nighjt. The 85 was eventually sold 2011 in favor of using the 76mm for all tasks. The 76mm is nearly as capable in terms of Light Gathering Power, but much more portable. Since the TV Refractors have come out, there is a larger variety to choose from that challenge the TVs. But until I have a good reason to change scopes, I stick with TV76 for now. Solar Telescope-H-Alpha Solar Telescope-White Filter Imaging Telescope Lunar-Public Star Party-Astro-Camera / Computer Projection Rich Field Telescope Stand Alone Finder-Scope for 20 inch Travel-Solar Eclipses & Transits |
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| Greg Babcock's Astronomy Website | My Current Telescopes |
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