The Telescopes
Got them for €40,00 /pc in a local drug store. The objective lenses
appear to be Fraunhofer (air gap) achromat. The tubes are made from
aluminium - inner side being treated to prevent reflections - and give
good stability. A couple of eye pieces and other backend stuff was
supplied. I dumped it all besides the 25mm eye pieces (all plastics,
all cheap, etc.).
Focal
Length
|
700mm
|
Aperture
|
60mm
|
Focal
Ratio
|
11,6
|
Modification
The basic idea was to directly screw both tubes together, using washers
to determine the required eye to eye distance. In order to access the
inner side of the tubes, i.e. when fixing the screws, it is required to
remove the objective doublet.
Make a
note which way they were in! Each of the objectives is made from two
lenses, separated by some tiny spacers. Watch carefully and think twice.
Next step will be the removal of the objective housings, in my
telescopes, some black plastic zylinders - it night be necessary to
remove some of the outer surface. Now the focusers will go off...
Removal of the tripod connecting pieces is next. Now you should have
two nice aluminium tubes with
Two nice holes are available already, the bold for the azimuthal
adjustment rod. These bores are the only ones in my telescopes, being
more or less at the same position for both tubes. They are held in
position with 5mm screw, which will use to join both tubes in a latter
stage (you might reach you junk-box right now for two 5mm nuts and a
bunch of washers).
With having given two bores next to the focuser, the upcoming event
will be drilling another pair close to the objective housings (or at
least where these were seen last).
To do so, I temporarily screwed both tubes together, using the existing
pair of holes. It is now a trivial part to mark the position for the
drilling exercise. Unscrew tubes... drill... done!
You know the distance your eyes? Counting and fitting sufficiently
enough washers is next.
Everything should be set by now to join both tubes.
Grind off the objective housings' as much touching outer sides as much
as required.
Clean off all the debris caused by your machining.
The focusers now will be ready to go back in place. Now the objective
housing... the lenses. The latter require a little check for dust. Set
the lenses back considering the notes you hopefully took.
Cheapo-Bino in Action
Appearently there are some hotspots of my digital camera.... but you
might clearly see Mars on the second image, just above the bino (see
full scale image!). And, by the way, the aluminium pole in the
background is my short-wave aerial (GPA50) and is not to be found
amongst the delivered items ;-)
Moreover you might wonder why I am using an EQ2 in "azimuthal mode"....
it prevents you from tilting your head, and thereby makes it easier for
you to look
through the bino-scope....
