P r i m a L u c e L a b i S r l
E SAT TO u s e r m a n u a l
Application example: ESATTO with Schmidt-Cassegrain and EdgeHD telescopes
Schmidt-Cassegrains and EdgeHD are great
instruments because they combine high performance with ease of use (for
example, they are simple to collimate) and portability (they are among the most compact optical tubes, although the dia-
meter can also be large). However, the internal focuser of these telescopes (which allows focusing by moving the primary
mirror) generates image shift and mirror flop problems that we can now avoid
thanks to ESATTO.
Problems caused by internal focuser of
Schmidt-Cassegrain or EdgeHD telescopes
Image shift is generated when the focus with the
internal focuser generates a displacement of the
image: this problem is evident during
high-ma-
gnification astrophotography
of planets and the
Moon
when recovered
object can even be
moved
out of the sensor field of view. By using
ESATTO
as focuser for Schmidt-Cassegrain or
EdgeHD, we can avoid
the image shift since
we
focus with the external focuser (and no longer
using the internal stock
focuser). Since ESATTO
has a precision micrometric control with a 0.04
micron resolution, we can also focus with much
greater precision than you have with standard manual focusing, without introducing vibrations during focusing (since we
don't touch the telescope to focus but we control ESATTO
with a USB connection from EAGLE or an external Windows
computer or through the Virtual HandPad with WiFi connection from smartphone or tablet).
Mirror flop is the displacement of the primary mirror which tends to move due to its own weight and it's a problem for
long-exposure astrophotography of deep-sky objects. This problem was fixed
by Celestron EdgeHD telescopes which in-
troduced an integrated primary mirror locking system. Unfortunately this also
prevents focusing between
expositions
(that is commonly done when doing long-exposure astrophotography, for example when changing filters) and
is therefore a problem also for the remote control of the telescope. Instead, by using ESATTO
as focuser for Schmidt-Cas-
segrain or EdgeHD, we can use the primary mirror locking system (in telescopes equipped with this system) and perform
micrometric focusing using ESATTO. This way Schmidt-Cassegrain telescopes and, especially, Celestron EdgeHD become
ideal instruments also for remote control!
Connect ESATTO to
Schmidt-Cassegrain or EdgeHD telescopes
ESATTO
is available in different diameters but, if you want to use it as focuser for Schmidt-Cassegrain or EdgeHD, we re-
commend the 2" model since
it has the lower thickness
(as we will see later it avoids back focus problems) and it already
has of a larger free aperture
(51mm) than the diameter of the
baffle tube
of these telescopes. As focuser for Schmidt-
Cassegrain or EdgeHD, it is therefore not necessary to use ESATTO
3". Removing the visual back
of Schmidt-Cassegrain or
EdgeHD telescopes, you will find a thread that can be:
p a g e 2 5
