Orion Hardware Useful to Occultation Work Ernie Iverson Sunday, October 21, 2012 IOTA Annual Meeting Las Vegas, Nevada • • • • • I didn’t plan to give a talk this year, but Ted Blank asked if I would share some of my techniques. Most of the individuals in the room have been observing occultations decades longer than I have so my techniques are probably not that useful. However, Orion has updated an old version and introduced a new version of their slow motion control head that warrant consideration by IOTA. A demonstration of these products made up the bulk of my presentation. David Dunham suggested after the annual meeting that I put together a Power Point presentation that could be included with the other meeting presentation slides. The advantage to creating slides after the fact is that I can include things overlooked during the presentation and add comments about the discussion afterward. • Topics: 1. Improved slow motion control tripod head 2. New Mini system mount 3. New AZ-4 Micro-Motion Altazimuth Telescope Mount 4. The value of using a green laser The Old Tripod Slow Motion Control Head • • • • The main disadvantage is that the joints loosen up over time and can not be retightened. (See arrows 1 and 2 on the right.) The course altitude adjustment (arrow 3) can be over tightened or subjected to too heavy a load which will damage the joint. The result is that this joint becomes loose and floppy. The bottom line is that as the slow motion head ages, it loosens up from normal wear and becomes unstable. In that condition it is not much of an improvement over the standard plastic head tripod. 3 1 2 Orion Recently Improved the Slow Motion Control Tripod Head • • • • • • Notice the Allen head screws, at points 1 and 2, which allow you to tighten the fit and remove any slop when needed. The course altitude adjustment (arrow 3) does not appear to have been upgraded. But considering all the other upgrades, it is hard to imagine they did not do something internally. I recommend never attaching heavy scopes or over tightening this joint. Course Altitude Adjustment = A Fine Altitude Adjustment = B Fine Azimuth Adjustment = C 1 B A 3 C 2 Attaching the Slow Motion Head to a Tripod • • • The slow motion control head can replace the normal tripod head Attachment hardware is a long ¼ 20 bolt and 3 large washers. I made a wooden spacer for inside the tripod tube to keep the bolt centered. A New Mount for the Mini System Using the Slow Motion Head • • • • • Sorry, I forgot to mention this idea at the annual meeting. The slow motion head can be bolted to a sturdy piece of plywood instead of a tripod. If the ground permits, the plywood can be secured to the ground using large nails or spikes (shown) inserted into loose fitting, predrilled holes with a hammer. Removal is easy by just using the claw part of the hammer. If the ground does not permit using nails then the plywood can be secured using large rocks or bags filled with dirt. Advantages of Plate Mounting the Mini System • • • • Very low profile minimizes exposure for better concealment in brush, weeds, etc. Low profile also gives better wind stabilization than larger tripods. Depending on the tripod used, this arrangement probably takes up less space and cost less than standard tripod mounts. It should be possible to scale this design up to the Midi system using a spacer and a longer bolt. New Orion AZ-4 Micro-Motion Altazimuth Mount • • • • • • • Weight is just 7 lbs without OTA By comparison the AstroView equatorial tripod weighs 27.5 lbs. and costs over $100 more. The AZ-4 is designed for scopes less than to 10 lbs. The Orion 120 mm Maxi OTA with rail and clam shell attachment is 9.6 lbs. Tripod height, as shown, is 31 inches (legs not extended). Height with Micro-Motion head removed is 25 1/4 inches. Tripod fits in a large suitcase with the head removed. AZ-4 Micro-Motion Head Attachment • • Micro-Motion head attaches to the tripod using 3 Allen head screws. Center bolt tightens the azimuth joint. Possible Tripod Problem Points • • • • • Upper leg attachment is made from hard plastic and is pop riveted to the metal leg. If the pop rivets fail they can be drilled out and replaced with machine screws. Or the leg can be glued to the bracket with epoxy. If the plastic breaks, it can be replaced with a wooden dowel inserted into the leg and a metal bracket. Notice that the legs can be easily removed by just loosing the clamping bolt. Possible Tripod Problem Points (cont.) • • • • Lower leg hardware is made from hard plastic also. Notice it is attached to the metal tube using machine screws and not pop rivets. You should be able to shorten the legs, if desired, by removing the plastic base and cutting the metal tube. Threaded height adjustment uses a brass insert. Possible Tripod Problem Points (cont.) • • • • The spreader bar system is made from hard plastic. If it breaks it can be replaced with a cord to prevent over spreading and a weight to give some downward pressure. The top plate just snaps into place with just a ¼ turn. I consider this feature a plus. Notice that there are no screws securing the plate. Screws could get lost in the dark and they take time to install. Micro-Motion Head Problem • • • • • • The mount is rated for less than 10 lbs. so the 120 mm OTA (9.6 lbs) is right at the limit. At low altitude the OTA is steady, but as altitude increases the tendency to slip backwards also increases dramatically. This is caused by the OTA resting on top of the pivot point. Steve Preston suggested the dove tail bracket with a Wimberley bracket to lower the CG below the pivot point. Note that there are 2 Allen head screws (1) that will tighten the joint. One screw is located on each side of the joint. Care should be taken to not over tighten the quick release elevation knob (2). This can damage the joint. 1 2 Counter Weight System • • • • • • To fix the balance problem I added a simple counter weight made from parts on hand. The rail is standard T-nut stock purchased from Rockler Woodworking. Scope Stuff also carries rail material that is a little less beefy, but it’s more expensive. You can buy just the 1 lb. weight from Scope Stuff with mounting car for $25. Part number #CW10. Cheaper weights could be made using plastic pipe parts and BB’s. The ¼ 20 all thread rod is available from any hardware store. Steve Preston also suggested using a spring. I think it is a good idea, and I will look into creating a spring counter weight design. Details of the Counter Weight System Details of the Counter Weight System (cont.) • • Notice that I cut off about 2 inches of the dove tail bar so that it did not interfere with the altitude micro adjustment knob. Also observe that the micro adjustment knobs use a screw collar locking system. The days of trying to tighten a set screw in the dark are over! General Comments on the Counter Weight System • • • • Placement of the counter weight is variable in this design, but this feature is probably not needed. You can probably replace the T-nut rail with a piece of aluminum angle stock with fixed mounting holes. The upper weight just provides a convent way to twist tighten the counter weight onto the rail by screwing it up against the rail. Two weights are probably not necessary, although if I was going to use only one, it would be the lower weight. If needed a longer all tread rod can be used. Bottom Line Assessment of the AZ4 Micro-Motion Altazimuth Mount • • • • • • • Using the counter weight system the mount will hold a 120 mm Maxi system vertical with out slipping. The camera image shakes more than I’m use to with my AstroView mount (a much heavier mount) when adjusting the micro-motion controls. Once set, the mount was stable and did not shake when used for the (521) Brixia occultation. It remains to be seen how the mount will perform in windy conditions. I’m encouraged, and I will be more likely to take a 120 mm Maxi system on the airplane in the future. At just 7 lbs. it saves a lot of weight. Remember this is not a heavy duty mount and therefore it needs to be handled with some care. If you need a heavy duty mount then get the AstroView equatorial mount. What is the Fastest Way to Find a Prepoint Star? • • • • • • Use a green laser!! First put the laser spot in your video monitor by pointing at a GROUND target 100 to 200 feet away using the adjustment screws. The closer the ground target the greater the error when you point it at a star. Be very careful to turn it off when an airplane is in the area. If you don’t need it, turn it off. The back scatter from the laser is visible in binoculars so even a faint prepoint stars can be used. Once the laser is aligned to the scope, you can be on a bright prepoint star in just a few seconds. Green Laser Finder • • • • The Orion green laser finder bracket fits in the accessory shoe located on both the 120 mm and 80 mm telescopes. A metal collar is secured over the on/off button with 3 set screws (1). The threaded screw (2) allows easy on/off control without disturbing telescope alignment. I have two lasers, one for the 120 mm scopes and one for the 80 mm scopes. This helps keep the alignment close when it is moved between scopes of the same aperture. 2 1 Green Laser Finder (cont.) • • • • The laser has to be realigned to the scope for each Mini system, because the accessory shoe and scope are not in a standard fixed alignment. When on target carefully remove the laser and take it to the next station. In cold weather, the crystal inside the pointer to drift out of the sweet spot and this will cause the laser to first decrease in light intensity and then it will eventually shut off. When this happens, simply attach a hand warmer packet with a rubber band. One bag will keep the batteries and crystal happy all night.