See <http://www.telescopes.ru/manuals/tal1/tal1_manual.phtml#62> where
you will discover that your telescope is designed to do wide field sky
photography using the telescope as a guiding device and not as the lens.
You are expected to attach the camera (with its own lens) to a
supplied bracket attached to the declination axis (the one with the
counterweight). You then take wide angle views of the sky using the
camera's normal lenses.
While it is possible to use this scope as the lens for the camera it
will not be easy. When using a telescope as a lens there are two
fundamentally different methods. The first is the telescope as the
prime lens (of 805mm focal length) and the second is eyepiece projection.
In the case of using the scope itself as the prime lens your first
problem is that the focal plane of the scope must extend beyond the side
of the tube sufficiently far to reach the focal plane of the camera.
Most newtonian telescopes are *not* designed to allow you to do this.
Whether this one is able is hard to tell but I suspect not. In
addition, when using a reflecting telescope as the prime lens it's
desirable to have the secondary mirror of larger diameter than when used
visually in order to avoid vignetting since the camera's field of view
is much larger than that of the eye.
When used for eyepiece projection the eyepiece of the telescope is used
to project an image onto the camera's focal plane. In this case the
telescope and eyepiece together are serving as the prime lens but of
much longer focal length than the telescope alone. A variation of the
eyepiece projection method has the eyepiece focused for your eye which
is then projecting a beam of parallel rays focused at ininity. The
camera is then placed behind the eyepiece but this time with one of its
own lenses attached and focused at infinity. Since the rays emerging
from the eyepiece appear at infinity the camera's lens will properly
focus them at the camera. This method can even be used with non-SLR's
as long as the camera lens can be focused at infinity.
With any method not utilizing the camera's own lens you need first a "T
adapter" which has the camera's specific lens mount on one side and 42mm
diameter "T threads" on the other. Various other adapters are then
available to adapt the T mount to other adapter tubes fitted to the
telescope.
In the case of prime focus photography the adapter would be a tube of
1-1/4" outer diameter with T threads on one end to screw into the
camera's T adapter. The 1-1/4" tube is the same diameter as a standard
telescope eyepiece and the camera and adapter tube would be inserted
into the focuser the same as an eyepiece. 2" eyepieces and focusers are
also available and are better suited to prime focus photography in order
to reduce vignetting from the small 1-1/4" tube.
In the case of eyepiece projection the adapter tube will be 1-1/4" OD on
one end and 1-1/4" ID on the other plus an outer threaded sleeve to
connect to the T adapter. You insert the eyepiece into the inner tube,
screw the end with eyepiece into the T-adapter and insert the whole
assembly with camera into the focuser.
When using the T adapter the camera is supported by being physically
attached to the focuser via the adapter tubes. When using projection
through the camera's lens some other support must be found to hold the
camera in alignment with the eyepiece. It's possible that the sun
projection screen could be adapted to perform double duty here.
Also problematic with cameras attached to newtonian scopes is
longtitudinal and radial balance. If the camera is heavy it may be
desirable to attach counterweights to the opposite side of the tube for
radial balance. Strategic placement on the opposite end of the tube may
also handle the longititudinal balance problem but that can also be
solved or at least mitigated by sliding the tube in its saddle.
Good luck,
Chuck Norcutt
orava@xxxxxxxx wrote:
>
> Hi there!
>
> I just fulfilled my very long dream and bought a nice little astronomy
> telescope TAL-1 (see http://www.telescopes.ru/product.html?cat=1&prod=7 ).
>
> Now I would like to attach my OM-4Ti (and E-1) to this telescope so that I
> could take photos of the moon through the telescope. But I am so new to
> telescope optics that I really don't know the best way to do it. Surely I
> must
> attach the camera to the same "pipe" where the eyepiece sits. But do I have
> to
> have an eyepiece there also or do I only need the camera body? Or should I
> have
> a lense in the OM also? I doubt that...
>
> All ideas, experiences and theories are wellcomed!
>
>
> Best wishes,
>
> Olli
>
> ==============================================
> List usage info: http://www.zuikoholic.com
> List nannies: olympusadmin@xxxxxxxxxx
> ==============================================
>
==============================================
List usage info: http://www.zuikoholic.com
List nannies: olympusadmin@xxxxxxxxxx
==============================================
|