Large Alt-Az Telescope at Big Bear

One Meter Photometric Telescope at RTMC (Riverside Telescope Maker’s Conference) on May 15, Big Bear Lake, California

Report from: Russ Genet, Reed Estrada, and VP Chris Estrada

The one meter wooden prototype photometric telescope made it to RTMC this year.  First “sawdust” was this past October, so construction has been underway for about seven months.  The mirror for the telescope, a 1 meter f/4.0 spherical meniscus ¾ inch thick, weights about 70 lbs.  It was kindly donated to the project by DOTI Optical.  The telescope is a prime focus system (no eyepiece) just intended for photometry.  We consider it a science “light bucket” telescope.  An aluminum prototype is nearing completion at Inca Corp. by George Roberts and his associates.

The telescope is still a work in progress with much remaining to be done.  The basic construction has been completed, and the drive components have been installed.  We did not operate the drive system at RTMC due to a short in the altitude cable connection we didn’t have the facilities to repair on the spot.  The instrument rotator/focuser is being built by Andy Saulietis and should be installed next week.  The control system is the new Sidereal Technology brushed servomotor control system that should be ready in a couple of weeks (we are temporarily using the older SiTech control system for checkout).  With the OTA trusses and top altitude trunion sections disassembled, the entire telescope fits in the back of a Jeep Cherokee SUV, although it was brought to RTMC in the back of Reed’s pickup truck (he was doing some last minute work on the telescope while Russ was giving a talk at SAS).  What follows are some photographs of the telescope at RTMC.

Reed checks the 18 point mirror support system while Russ fastens one of the two removable upper trunion sections.  Tom Smith provides moral support.

Chris Estrada fastens down the brace between the two removable upper sections of the altitude trunions.

Chris and Reed Estrada finish fastening the aluminum tubing brace between the upper trunion sections.  Richard Berry, far right, helps hold the brace in place, while Gary Cole (blue jacket and tan hat) looks on.  Dave Rowe (between Chris and Reed) sees something down on the ground.  What could it be?

Russ and Reed move the 1 meter mirror from a transport box to the telescope.  Normally the mirror will ride installed in the telescope, but the transport safety/cushioning arrangements have not yet been completed.

Reed and Russ lower the mirror into the mirror box.  The two yellow items on the side of the rocker box hold wheels that keep the altitude trunions  centered on their drive/idler wheels.  The aluminum “disk” near Russ’s; foot is the toothed altitude drive pulley.  An AT-5 steel reinforced belt can be seen going down to a smaller pulley on the end of the altitude motor.  One of the two main wheels can be seen on the left.

With the mirror in place, Russ looks at the reflection of the clouds.

Reed, Russ, and Chris move the assembled truss structure into place.  The two-bay truss is being redesigned to make its assembly easier.  Cross bracing cables tightened by turnbuckles are being added to stiffen the structure.

Reed and Russ hold the truss in place while Chris fastens down one of the corners.  Note that the mirror cover is in place during assembly.

With the telescope assembled, Reed, Russ, and Chris pose for the camera.

Although not operational yet, Dave Rowe was impressed that after only seven months of work, the telescope had been physically assembled at RTMC, and he gave the telescope a quick kiss.

Chris, Reed, and Russ tilt the 1 meter photometric telescope (aka Packman or Big Blue) down beside the Jeep that it fits inside. Celebration at the Third Annual Large Alt-Az Telescope Dinner.  There were toasts to PlaneWave Instruments CDK 700 telescope, the portable 42-inch CDK wooden telescope (13 years in the making), and the 1 meter photometric telescope.  Seen round the table is Russ Genet, Tom Smith, Rick Hedrick, Floyd Fietchner, Dave Rose, and Deborah Ceravolo.  Peter Ceravolo, Joe Haberman, and a few others were there but did not appear in this photograph.

The 1 meter photometric telescope was just part of the special program at RTMC.  The announcement for the program is below:

Large Alt-Az Telescope Developments

Special Presentation Session and Workshop

Riverside Telescope Maker’s Conference

May 15, Big Bear Lake, California

The Riverside Telescope Maker’s Conference has scheduled a special Saturday morning session that will feature six short talks on large (for amateurs) alt-az telescope developments.   A complimentary two hour workshop follows in the afternoon.

9:15-10:30   Large Alt-Az Telescope Developments

A Brief History of Alt-Az Telescopes (Richard Berry)

The Alt-Az Initiative (Russ Genet)

CDK Direct Drive Telescopes (Rick Hedrick, Joe Haberman, Dan Gray, Dave Rowe, & Allan Keller)

Lightweight Aluminum Telescopes (Tom Osypowski & Howard Banich)

A Portable 1-Meter Photometric Telescope, (George Roberts, Reed & Chris Estrada, & Russ Genet)

A Portable 42″ Broken-focus Corrected Dall-Kirkham Telescope (Dave Rowe & Rick Hedrick)

2:00-4:00   Large Alt-Az Telescope Workshop

Chair: Dave Rowe. Participants: Howard Banich, David Davis, Russ Genet, Dan Gray, & Rick Hedrick.

Topics: primary mirror substrates, spherical and parabolic correctors, the corrected Dall Kirkham optical design, direct drive motors, encoders, bearings, fundamentals of servo control, field de-rotators, material properties and material selection, truss structures, and transportation of large alt-az telescopes.

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