The complete conversion
of a GEM, with 1.5 - 2" shafts for example, will typically cost
between US$1400.00 - US$2500.00. Options chosen by the customer will
alter that base estimate.
Customers who already
have some of the needed parts, (laptop, gears, the controller, motors etc.),
will be charged less if the parts are suitable. However, we have yet to
convert a large GEM for less than US$1400.00.
The total conversion
cost depends on the gear ratio you are wanting on the scope. For visual
use and short ccd work, a small 180:1 Dec. gear and the stock 180-360:1
R.A. gear will work great. It is a little cheaper too. Long exposure CCD
work requires a little more gearing and costs a little more. (the gears
money and the modifications to hold them in place cost money). This is
assuming that you have a good 359/360:1 R.A. gear.
Toothed belts and pulleys
are required on all conversions to achieve the recommended ticks per revolution.
Once converted, your
mount, if it is in decent mechanical shape, can easily achieve sub arc
second pointing accuracy. This is verified on a recent DS-16 conversion,
by the owner.
easily accomplished using one of the large old GEM's. Periodic error for
the gearing we make is typically on the order of 5-6 arc seconds per worm
revolution. This is before any autoguiding corrections or P.E. eliminator
The use of ultra expensive
gears is not necessary. We typically recommend using our own shop
made worm gears.
There is a manual for
using GEM's listed in the interactive support page.
Slewing speeds will
be around 3 degrees per second if you use a 360:1 gear ratio on each axis.
The higher the gear ratio, the slower the slew speed.
Since most of these
mounts will be in an observatory, we do recommend using a laptop to operate
the software. Most observatories are small and an added desktop/monitor
will take up more space.
Laptops can be bought
from E-Bay for $150-$225 daily. Specifications and comments about the laptops
can be found on our "About the Computer" page.
You can interface scope
with any planetarium or camera program that is ASCOM compatible.
Mount time away from
you will be on the order of 4 weeks. We typically charge you at least half
of the total cost up front, order all the parts, get most of it ready for
conversion and then get the mount from you for conversion. This way we
don't have mounts filling up the shop waiting on parts. You don't loose
your mount for very long either.
Do keep in mind that our scope control system
is extensive and has been tested and used by hundreds of scope owners of
a period of many years. It is not a 'hobbled together' system that will
give you problems most of the time and rarely work properly.
When a scope is properly converted, installed and the
end user knows how to operate it, it's accuracy and performance will astound
even the most critical observer. When you consider what others pay for
something that performs only half as well, you truly do get more than you
pay for with this system.