This
seems a very simple subject but experience taught me how to get the
scope as accurately level as possible in the minimum amount of time.
At
first I
was using a small spirit level from a DIY store to set up my
tripod, but it proved difficult to place the level in
order to check all the axes. As part of the ETX alignment
process the OTA
has to be level and it was hard to balance the DIY on the OTA. I
tried a bubble level and this was better but it can take lots of
adjustments to get the bubble centred. So I bought the two
Engineering standard levels shown in the picture. The
two axis "T-level" makes levelling the scope and tripod very easy and I
can normally level with two, or maxiumum three, adjustments of the
tripod legs. The level is aligned with axes A and B as shown in the
diagram. First adjust leg 1 to level axis A then adjust leg 2 to level axis B. Simplicity itself! Sometimes it is necessary to make one more adjustment but most times it has not been necessary. On soft ground always push down on the legs before mounting the scope and always place the level on the mounted OTA.
The small
square level is used for levelling the OTA during the ETX
alignment. It's small enough to sit comfortably on the curve of the OTA
and is visible from all sides.
Training the ETX drives The
set up function in the ETX125 allows the drives to be trained. The
manual says to use a terrestrial object in daylight, but common sense
tells me to use the most distant fixed object visible......in other
words Polaris. It also makes sense to me to train the drives
in darkness in case exrernal light sources affect the optical
sensors used by the ETX drives to measure the motion of the OTA. I use
a home made 26mm reticle eyepiece to accurately position the star in the field of view.
Visitors since 17th Nov 2007