Star parties at Hale Pohaku are very informal affairs. You never really know who is and who is not going to show up. We just don’t plan that much.
It had just been too long, I had not had a good night out with the telescope for months. This dark moon Saturday was not going to be missed, I packed up Deep Violet and headed for The Mountain. I knew a few folks would be there, certainly Cliff and Tony. The rest of the folks were a surprise to me. As the evening progressed more and more ‘scopes showed up, a few more familiar voices in the darkness.
Almost all of the big dobsonian telescopes to be found on Hawai’i show up at the VIS for the night.We had picked a decent night. The transparency was fairly good, and the seeing was great. We enjoyed views of Jupiter better than I had seen in quite a while, Probably years. There was the red spot, moon shadows, even the moon Io could be clearly seen transiting the disk.
The only real issue was the wind, it was annoying. A couple of us moved our telescopes into the patio area of the MKVIS, where the building offered some shelter at the expense of blocking some of the sky.
The view was pleasing sharp and crisp, revealing decent optics and steady air over the mountain. I could just make out the central star on M57, something I had only done before with and even larger telescope.
The instrument may date to the 1800’s but at that time it was powered by water and muscle as there was no electricity on the mountain. It was not until much later, in the middle of the twentieth century that the telescope was refitted with electrical controls and motors.
The control console for the 36″ Refractor at Lick Observatory
The visitor directions on the website had specifically cautioned that the summit road was curvy, something I found to be a drastic understatement. From the very bottom it is curve after curve all the way up, with almost no straight sections. S-curves followed sharp bends leading to hairpins. Nearer the observatory the curve intensity only increases as the road narrows. Local history indicates that the horse-drawn wagons that transported heavy equipment up this road could not negotiate steep grades, the only solution was to follow the contour of the mountain, resulting in an incredibly curvy road.
On a sunny Saturday afternoon there were other users, the road is apparently popular with local cyclists. With the density of the sharp curves there was often little choice but to follow at bicycle speeds at times. I would much rather drive up Mauna Kea than this road again. Next time up Saddle to the summit I will recall Mt. Hamilton road and consider myself lucky.
The reason I was climbing this winding road was simply to be a tourist. Unlike the previous seven days, this day was to be fun. For much of the previous week there had been full day sessions of lectures and labs covering the intricacies of adaptive optics systems. Spending a full week in Santa Cruz might be considered a vacation, aside from the fact there had been very little open time to explore the surrounding area. There was only one open day in my travel plans, and I had specific plans for that day, a visit to an observatory.
The 36″ refractor at Lick ObservatoryI arrived well ahead of my late afternoon tour appointment, no problem, just play tourist for a while. At the gift shop / information desk I met Lotus Baker, a longtime Mt. Hamilton resident. She was full of stories and information. We chatted for a while, until her turn to lead a tour of the classic 36″ Lick refractor. Lotus proved to be an excellent tour guide, providing an enjoyable tour of this beautiful telescope.
The massive set of cables going into the telescope must twist as the telescope rotates. Besides cables there are also hoses to carry high pressure oil, glycol coolant and compressed air. To accommodate the rotation, these cables and hoses go through a large assembly called the Azimuth Wrap. Looking a bit like an oversize bicycle chain with cable laced through the links, the wrap insures the cable does not kink, tangle or stretch as the telescope sweeps back and forth.
Lacing new cable through the wrap is an intricate task of threading through the metal comb that supports the cables in each link. See the little pink one in the middle, just did that…
The many cables needed to operate the Keck 2 telescope thread through the azimuth wrap.
Apparently the purple refractor was quite the hit on yesterday’s webcast. Not only did it provide beautiful imagery of the Transit of Venus for everyone to enjoy, but caught the attention of many viewers. There we many comments… “Where can I get one?”, “How much?”, and my favorite… “…paint Keck purple!”
Violet Haze really is a great telescope, an entirely hand-made instrument, with the exception of the focuser. The lens set is a full apochromatic triplet by Roger Ceragioli, a true expert in refractor design and manufacture. The purple optical tube is my own machine work. The result is a truly unique telescope that is a joy to use.
Imaging Venus in the daytime a mere 12°44' from the Sun.
Aiming a telescope at the Sun is deceptively difficult. You can not use a optical finder for risk of eye damage. Unit power finders, like a Telrad, are of little use as you can not see the projected image. Telrads can also be damaged by sunlight. In a pinch you can simply use the shadow of the telescope, positioning for a minimum shadow. This at least gets you close.
A Sun Finder mounted to a TeleVue 76mm 'scopeThe best solution is to build a finder designed just for the Sun… A Sun Finder.
There are many plans for Sun Finders posted to the web. Most use a shadow or projected point of light. The version I built is no exception, using a pinhole to project a point of light on a translucent screen. The trick is to make such a device simple and accurate.
With simple metal working capability a Sun Finder like this one can be made from sheet metal, or machined from solid aluminum. I chose the latter as I had the capability. This design uses a pinhole that projects a similarly sized dot of light at the rear of the finder. The front face or the finder, through which the pinhole is drilled, creates a shadowed area for in which the projected dot can be seen.
A Sun Finder in use with the projected dot visibleA longer distance from the pinhole to the screen will increase the sensitivity in aiming. In practice I have found that at least three inches is sufficient for most telescopes while keeping the device compact. Experimentation with the design can be entertaining and educational. No need to stick strictly with this design, just borrow the basic ideas, a lot of variations will work.
This design is based on an aluminum extrusion, a 3″ x 1.5″ channel. This save a good deal of machine work in creating the finder. As much of the machining is done along the length, a number of finders can be made at the same time. I made six finders from a seven inch scrap of extrusion out of the shop scrap pile.
Plans for the Sun FinderThe screen is made from a small piece of 1/8″ thick acrylic. Common 0.1″ thick material will work as well. One side is frosted with sandpaper to create a translucent screen. Use of a clear screen allows the solar dot to be seen from front or behind while aiming the telescope. The screen is simply secured with a glue, preferably RTV. The frosted side should be mounted towards the pinhole.
To keep the device simple there is no adjustment in aiming. If the finder is mounted reasonably well, the dot of light will be on the screen. The first time out it is necessary to first get the Sun in the field of view. You can then mark the position of the projected dot with a permanent pen (Sharpie or similar). After that aiming is simply a matter of positioning the dot on the mark. If the mark is made on the smooth side of the acrylic screen it can be easily erased and re-marked if necessary.
Done, a simple and reliable Sun Finder to work with just about any small telescope.
