Telescope clock drives from the 1980’s or earlier often used AC synchronous motors. These commonly available AC motors are used to power timeclocks, record player turntables, and telescopes, anyplace a motor needed to run at a very accurate speed.
A Celestron telescope drive configured as a sidereal rate tracking camera platform
The speed of a synchronous motor is set by the frequency of the powerline, in North America and many other places this is 60Hz. As the frequency must be synchronized for every power station on the grid the frequency is quite accurate, a feature exploited by clockmakers and telescope builders. Once found everywhere these motors are less common, but are still around.
Drive Correctors
It was the common use of these motors in telescope drives that led to the invention of the drive corrector, a device that was once a required piece of kit for serious amateur astronomers. Drive correctors like this were needed when operating from a battery at some remote location, generating AC from a 12Vdc car battery.
You also needed a drive corrector for guiding while doing astrophotography. The corrector could speed up or slow down the telescope drive a bit to correct the telescope drive speed and stay on target, something not possible with the fixed 60Hz of the mains supply. Thus the term drive corrector.
It was a last minute request. OK, not actually the last minute, but two days is not much lead time to plan a public outreach event.
Fortunately there was not much to arrange, a single solar telescope and the standard table setup we keep packed and ready to go, all we had to do was show up. Drive up to the Pōhakuloa Training Area to join in their Earth Day events. There would be several hundred students from local schools, tables and displays from other organizations, a good outreach opportunity.
A solar telescope set up at Pōhakuloa Training Area for Earth Day.In ten years of driving past the front gates of PTA, I had never been inside. Why not, just an easy drive from Waikoloa, and I have a telescope that will do the job perfectly.
It seems odd that a military base would celebrate Earth Day. What do attack helicopters, live munitions, and troops have to do with the environment? The answer should not be that surprising… Military bases are often large effective nature reserves.
Large areas of land, much of which sits unused and undisturbed, are closed to public access. An active range needs huge safety and buffer zones around the firing ranges. Of the 133,000 acres that makes up PTA, only a small percentage is directly impacted by the training activities. The rest is home to a endemic and endangered species, closed to any activity that can disturb the land.
Where do you go to show a bunch of students from Hawaii Preparatory Academy the stars? Located in Waimea the school has a very nice campus, that is usually under heavy clouds every afternoon and evening. After looking around we settled on Mauna Kea Recreation Area in the saddle between Mauna Loa and Mauna Kea. At 6,700ft elevation the site can offer very good skies for stargazing. This area in the saddle at Pōhakuloa is often cloud free, a curious hole in the clouds between the mauna that tower on either side.
Students and chaperones from HPA enjoy dark skies with the 20″ obsession telescopeThe recreation area has recently been undergoing a 10 million dollar renovation. While the renovated cabins are not open yet, the new bathrooms and playground have proven immensely popular to travellers crossing the saddle from Hilo to Kona.
With the opportunity for a reasonably dark sky I brought the 20″ obsession. Tony and Maureen brought 12″ dobs. Tony’s friend Steve brough the 8″ he had just bought from Tony, a first night out with a new ‘scope. Cliff brought his 6″ imaging system set up to show objects on the screen. We had a lot of glass available, good telescopes, and surprisingly good skies.
Even when Venus is high in the sky and well placed for observation I will seldom take the effort of turning a telescope towards the planet. Why? Because Venus is pretty boring to look at. Perpetually cloud covered it has all the detail of a cue ball. It is a white disk with nothing of note to be seen. Yeah, pretty boring. Now turn the telescope to Jupiter.
Venus approaching inferior conjunction, 24Dec2013One exception to this occurs when Venus is approaching, or just emerging from inferior conjunction. As the planet passes between the Earth and the Sun we are looking at the nighttime side of the planet, with only a little of the daytime side to be seen. As a result Venus will appear as a brilliant crescent.
This begins as the planet passes maximum eastern elongation, about two months before inferior conjunction. At this point the planet is seen from the side with respect to the sunlight, the planet will be about half illuminated. In the weeks after maximum elongation the planet will appear ever more crescent.
Venus on 28May2012, about 12°44′ from the SunThe last weeks before conjunction, as Venus is very low in the sunset, or the first weeks after conjunction as it sits very low in the dawn are the most interesting. During this time the planet is a very fine crescent, quite a beautiful sight in the telescope. Many observers, including myself, have made a point to observe Venus at this time, the one time this planet really becomes interesting to view.
Imaging Venus in the daytime a mere 12°44′ from the Sun.As the planet is quite low in the sky it makes it a challenging telescopic target and distortion by the atmosphere can be troubling, blurring the view.
It is possible to enjoy this sight in the daytime, while the planet is high in the sky, the seeing can be better and the view sharper. Of course this also occurs when the planet is near the Sun, thus extreme caution should be practiced at the telescope to avoid any direct sunlight and possible eye damage.
A page from Galileo’s 1623 treatise The Assayer—Il SaggiatoreThe phases of Venus are quite interesting from a historical standpoint. The phases of Venus clearly show that the planet revolves around the Sun. The phases were one of the primary arguments used by Galileo in his treatise The Assayer—Il Saggiatore published in 1623, where he lays out many of his ideas on science itself and how observation and experimentation should be primary.
While the the evidence challenged prevailing ideas of the time, some astronomers attempted to explain the phases of Venus by any other means to preserve their Earth centered universe, which led to rather tortured models of planetary motion. But it was clear to most that Galileo was right, the simple and elegant answer was that the Sun lay at the center. The orbits of Mercury and Venus, the phases, along with other observations like the moons of Jupiter, were hard evidence that few could ignore.
In 2017, eastern elongation occurred on January 12th. By now Venus has begun to show a substantial crescent, about 30% illuminated if you look today, Feb 12th. Over the next few weeks as the planet sinks into the sunset, the crescent aspect will thin dramatically.
By the end of February the planet will be only 17% illuminated, another week after that it becomes only 11%, by which time the planet will be difficult to spot in the sunset. Inferior conjunction will occur on March 25th. A couple weeks later and it will be possible to spot the planet in the dawn and observe the now thickening crescent.
Gluing the mirror box for Deep Violet, and 18″ f/4.5
The 18 point mirror cell, built to the plans from Barry & Kriege
The primary mirror support strap
The ground board with center pivot and teflon pads in place
Drilling a pocket to accommodate a carpet pad in the side of the rocker box
Deep Violet fully assembled and nearly ready for dark
Looking at the mounted mirror cell and primary mirror
Deep Violet at Sentinel, Arizona for the 2015 Pierre Schwarr Star Gaze
Looking in the rear of the tube at the mirror cell
Detail of the tripod head, latitude adjustment and the RA and declination axis
Primero setup at Jarnac Observatory among a friendly crowd of other telescopes
Stripping and cleaning the 14×100 binoculars
A completely disassembled Celestron Cometron telescope
Detail of the upper truss tube with the lever type latch
Detail of the brass threadserts used to hold the lower truss clamp
A 12.5″ dobsonian telescope after the refit
Machining the mirror cell from a piece of scuba tank
The mirror cell prior to installing the primary mirror with the focus knob at the back of the strut
A very standard design for the mirror mount
A front view of Makaʻiki ready to observe
Makaʻiki with the main strut extended for use
Makaʻiki under the stars for the first time at Hale Pōhaku on the side of Mauna Kea
The forms for the pier upright filled and leveled
Bill Lofquist pouring concrete into the upright part of the pier
The completed pier with a telescope atop
Looking at what remains of the paint on an old Celestron C8 orange tube telescope
The orange paint just crumbles away under a few sweeps of a power sander
Parts of the mount prepped and taped for painting
Paint drying on the front and rear castings of the old orange tube
A restored Celestron C8 on a similarly restored TeleVue Renaissance mount.
The C8 set up along the old Saddle Road for Mercury Transit
Re-assembling the secondary cage on the 20″ Obsession. The truss tube clamps still need to be cleaned up and re-installed, same with the focuser.
Grinding the heads off a few screws
The rusted hardware removed from a 20″ Obsession telescope
Opening up the truss tube clamps by widening the slot with a hacksaw.
A fix for the secondary mount
A failed plywood joint
Clamping the rocker box of a 20″ Obsession
Installing the primary mirror. This is a Galaxy Optics 20″ f/4. Oddly enough Sky Hudek, the son of John Hudek, the owner of Galaxy is a good friend and dive buddy.
Trunk handles added to the rocker box to make picking it up and loading it in a vehicle easier. They are mounted just high enough to avoid the wheelbarrow handles when installed.
My copy of The Dobsonian Telescope by David Kriege and Richard Berry
20″ f/4 Obsession #004 fully assembled for the first time in over a year. Ready for alignment and use!
Cherry Blossom Festival is a huge event where a large segment of the island population descends upon Waimea for a day of celebration. there are booths and events all across town. There are cultural demonstrations, cooking demonstrations, performances, and lots of food available for an all day, all town festival.
Viewing the Sun at the Cherry Blossom FestivalWith most of the parking on the south side of Keck observatory, the shopping mall parking lots, and the main event venue north of Keck at Church Row where the cherry trees are, a huge number of people cross the observatory lawns on their way to the festival. It is a natural fit for us to use the day for an outreach event.
The festival is also a very local event. Sure there are a few tourists drawn to Waimea for a festival. But, by and large this is a local event, the majority of attendees are island residents.
