152 > Optical Tube
O.T.A. (OPTICAL TUBE ASSEMBLY)
GOOD FIRST IMPRESSIONS
First impressions on unpacking the 6" Maksutov OTA is that it has been
built well owing to how big and heavy
it is. Everything is solid metal, even the corrector dust cap!
Without plastic parts like the Meade ETX-125 and Konus Motormax
130 have it feels very solid. The dust cap is felt lined and slides off
fairly easily so readers
warned to watch their toes while transporting the OTA!
With accessories mounted the OTA weighs in at 6.5kg/14.4lbs. The tube
is 178mm/7" wide and 432mm/17" long.
The ring around the corrector lets everyone at the star party know what
you've got. Maksutov-Cassegrain design with a focal length of 1900mm,
152mm making it a f-ratio of 12.5. The manufacturers
specification suggests a limiting magnitude of 14.8, angular
resolution of 0.75 arc seconds and a maximum
useful magnification of 300x.
Looking into the front of the scope it was a bit shocked to
find almost no evidence of corrector coatings like many of the Meade
telescopes have. There is a slight hint of blue tint to the corrector,
in many of
the supplied accessories that came with it, but it's hard to notice on
large piece of glass. I did later get to take the corrector off and I
can now confirm from the inside it has an obvious red-brown colour
similar to EMC or UHC. I've heard many horror stories of users damaging
their external corrector coatings so to have them on the inside seems
to be a bonus for cleaning optics and for the
While inspecting the OTA a line was found drawn in with permanent
marker! This is evidence that
someone has taken the front corrector lens off the scope after it was
manufactured. Annoying that whoever did this didn't use a more subtle
method so not to ruin the tube aesthetics. I expect the corrector was
taken off to fit the dovetail.
DOVETAIL MONKEY AT WORK
The OTA attaches to the tripod via a dovetail and instead of using
tube rings, whoever put this together decided to save a
few pounds by screwing it directly to the tube. Looking into the
telescope it was a bit
worrying to see the
mirror riding almost up to the screws. In
practice though I've not had any problems reaching focus but it could
be problem if
you were unlucky enough to get one with the screws mounted just 1cm
There are no baffles in the OTA but the inside is coated with a
none-reflective black paint. On close inspection there were some
scratches in this paint probably due to the dovetail fitter!
DEBRIS ON THE PRIMARY
Looking at the large primary mirror on the back it gives the impression
that whoever made the less than professional dovetail install
also left debris from drilling into the OTA. There were no
specifications given on the quality of the mirrors and glass but I have
seen retailers describe this scope as BK7 and 1/5 wave. I've
since had the corrector off and cleaned away the flakes of black paint.
The corrector was pleasingly easy to remove unlike some scopes I've
owned in the past.
A NICE REAR!
On the back of the OTA there is a 2 inch threaded back. A 1.25" step
down ring with 90 degree diagonal are also provided. The diagonal as
many parts on this scope was dirty and required cleaning before use.
The focusing knob on the back of the OTA is large was smooth to use
a lot of focus travel and no noticeable image shift. The knob loosens
before stiffening up towards the end of the focusing range giving
plenty of warning that there is no more travel left.
Three rubber covers on the back can be removed to
reveal six collimation Allen screws. Collimation on Maksutov's is
legendary for staying in place so readers are not advised to mess with
them until they have ruled all other issues such as bad seeing. The
collimation on this scope was very bad when it arrived but I managed to
sort it out. I tried various methods but by far the easiest and most
accurate was by focusing on a point of light on a TV mast in the
The OTA was of higher quality materials than expected but was let down
by debris from the amateur dovetail installation, and bad collimation.
issues can be corrected, however Joe Public may not have the skills to
do it themselves so I would recommend resellers check their scopes
before shipping to avoid unnecessary returns.