Adapters for the LX200 and the Takahashi
Most of these adapters were made using a small lathe that I have had for
many years. I used to use it to make german mounts for telescopes and many
other turned parts for hobbies , it has been one of the most useful tools
I have ever purchased. However many other people have access to this type
of tool and so I am merely showing pictures here of things you can make
for the telescopes.
These are some of the things I have made
Going from the top left to right they are as follows ,a mechanical
shutter for film photography of planets,tv camera,focal plane focusser
for camera, on the second row down from left to right is a short screw
on one and a quarter inch eyepiece holder for the LX200 meant for holding
the CCD camera as close as possible to the back of the scope.Next across
is a projection eyepiece holder for the back of the LX200.Last on this
row is an adapter to be able to mount screw on LX200 fittings to the back
of the takahashi.Notable being the 2 inch mirror diagonal off the LX200.Third
row down left to right again is a sliding filter holder that will fit the
LX200 and with the previous adapter the Takahashi as well.Next across the
third row is a polarizing filter holder for rotating a pair of these I
have, and finally on the third row a collimator without anodising as yet.The
fourth row is the narrow band in line light pollution filter for
the takahashi.This assembly fits the back of the focusser rack before the
camera,the camera adapter being screwed onto this adapter.
There are two main problems with film photography..
The first is getting a focus and the second is timing photographs from
fractions of a second to an hours exposure assuming tracking is being corrected
by some other method.For focussing I made an adjustable
adapter to replace the camera assembly on the back of the LX200.A camera
has to be on the film plane to within thousandth of an inch accuracy and
normally you can achieve this by the foucalt test. You normally open the
camera back and slide a knife edge back and forth across the film plane
doing the foucalt test to find prime focus.This is a pain when you have
a film in the camera it is also easy to damage your camera especially if
you use razor blades and things like that.The adapter is fitted in place
of the camera, the back of it then is exactly on the equivalent film
plane of the camera. In the back is a hole and it is across this that you
move an adjustable knife edge.In my case it is a brass one moved by a knob.When
you have found focus you take off the adapter and refit the camera which
is now in focus.The adapter was made as two tubes one sliding over the
other locked by screws.A precision inside micrometer was used with the
camera to find the correct distance the adapter had to be adjusted to in
length before being locked up permanently by the locking screws.
Planetary images are bright so you can not use the cap on telescope,cap
off telescope method for short exposures. You also wiggle the scope,conventional
shutters that whack up and down also do the same.The
shutter shown here is the type that irises radially in and out so there
is very little imparted shaking energy dissipated into the scope from shutter
movement. There is also an iris built in to this assembly so you have control
with that as well. Shutter vibration as low as this is easily dissipated
by the mass of the scope and mount but still the more weight to fight against
the better. I made fittings to adapt this shutter which I won from a professional
photographers junk box.
Collimation is important ...
However this
was made for the takahashi as I have had to strip its objective assembly
for cleaning before now and re-align everything afterwards.Recently made
and yet to be anodised black.
The LX200 I collimate in the normal way but the last item comes in
useful for that purpose in the form of a ...
Simple television Camera
This was made out of a
security camera module cost £65 uk. The camera is black and white
but there is an incredible sensitivity in the form of one tenth of a lux.
With the LX200 this resolves stars down to magnitude 9 and is great for
planetary and moon imaging.The camera board is only one and a half inches
square complete with lense.You can use it at prime focus or poke it with
its own lense into the back of eyepeices.It is shown here mounted into
a die cast box with connectors for the 12 volt power and external monitor
or video connection. I intend to video planets and frame grab images and
stack them and anything else it will resolve. I was amazed at the
noise performance of this camera uncooled. It may be possible to cool it
in the future.Yes you can use these to look at a defocussed image while
you collimate an LX200 if you are on your own or have short arms.