Orion Hardware Useful to
Occultation Work
Ernie Iverson
Sunday, October 21, 2012
IOTA Annual Meeting
Las Vegas, Nevada
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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.
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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
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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.
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Orion Recently Improved the Slow
Motion Control Tripod Head
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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
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B
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C
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Attaching the Slow Motion Head to
a Tripod
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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
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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
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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
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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
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Micro-Motion head attaches to the
tripod using 3 Allen head screws.
Center bolt tightens the azimuth
joint.
Possible Tripod Problem Points
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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.)
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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.)
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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
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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.
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Counter Weight System
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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.)
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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
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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
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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?
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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
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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.
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Green Laser Finder (cont.)
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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.