I have a meade 114mm reflector and have bought a 1.25" variable camera
adapter & t-mount.

I have set it up as follows:

put a meade 25mm plossl in the adapter & held in place with screw.
Attached the t-mount to the adapter.
attached a nikon d70 to the t-mount
fixed the camera adapter to the telescope lens mount.

Hi there

I have a meade 114mm reflector and have bought a 1.25" variable camera
adapter & t-mount.

I have set it up as follows:

put a meade 25mm plossl in the adapter & held in place with screw.
Attached the t-mount to the adapter.
attached a nikon d70 to the t-mount
fixed the camera adapter to the telescope lens mount.

the problem I am having is that I cannot get it focus when looking through
the camera eyepiece. It looks as if I need to move the focusing closer by a
few mm, but the focuser is a far down as it gets.

I have tried increasing the distance of the camera adapter (the variable
bit - the two screws to hold it in place and increase / decrease the length
of the tube), but this makes it worse.

I have also tried to attached the camera directly to the t-mount, then the
t-mount to the bottom silver part of the adapter that slots into the lens
mount (prime method?), but all i get is a total blur that does not change at
all when focusing.

Am I missing something?
Does any one have any links or instructions on how to set up a variable
camera adapter?

Any help would be greatly appreciated.

Thank you
callum


I'm assuming that you know that when using an eyepiece and "looking

Hi there

I have a meade 114mm reflector and have bought a 1.25" variable camera
adapter & t-mount.

I have set it up as follows:

put a meade 25mm plossl in the adapter & held in place with screw.
Attached the t-mount to the adapter.
attached a nikon d70 to the t-mount
fixed the camera adapter to the telescope lens mount.

the problem I am having is that I cannot get it focus when looking through
the camera eyepiece. It looks as if I need to move the focusing closer by a
few mm, but the focuser is a far down as it gets.

I have tried increasing the distance of the camera adapter (the variable
bit - the two screws to hold it in place and increase / decrease the length
of the tube), but this makes it worse.

I have also tried to attached the camera directly to the t-mount, then the
t-mount to the bottom silver part of the adapter that slots into the lens
mount (prime method?), but all i get is a total blur that does not change at
all when focusing.

Am I missing something?
Does any one have any links or instructions on how to set up a variable
camera adapter?

Any help would be greatly appreciated.

Thank you
callum
--

The way I use the inverse eyepiece projection method is to focus both the
scope and the camera in advance and then match them aftewards. To do that,
focus both devices to infinity, i.e. your scope for a relaxed eye at
infinity
so that it focuses properly on, say, a star, and also manually focus the
camera at its infinity setting.

Then when you pair them, the image should be properly focused for inverse
eyepiece projection (IEP). If for some reason that doesn't work, your
scope's
focuser won't be able to accomodate a relaxed eye focused at infinity, which
will be quite bizarre.

If the latter happens, you won't be able to focus properly your scope using
your eyesight and the given eyepiece. I had this problem with my Tasco OTA
and
the new eyepieces I bought, so I had to saw the OTA tube to shorten it, so
that correct focusing fell within the focuser's limits.

Other methods of focusing for IEP will be a nuisance, because you have two
devices to focus and it's kind of hard to do that manually.

On Fri, 9 Feb 2007 18:05:05 -0000, "Callum" <no@spam.com> wrote:

I have a meade 114mm reflector and have bought a 1.25" variable camera
adapter & t-mount.

I have set it up as follows:

put a meade 25mm plossl in the adapter & held in place with screw.
Attached the t-mount to the adapter.
attached a nikon d70 to the t-mount
fixed the camera adapter to the telescope lens mount.

Why are you attempting this sort of afocal imaging? It is difficult to
make work well, and generally the wrong approach if you have a camera
with a removable lens. Dump the eyepiece and adapter, and simply put the
camera (without lens) at prime focus. You'll need a T-mount adapter for
the D70, along with a 1-1/4 insert for it.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Hi there

thank you for the reply.

I have just tried this:

connecting the 1 1/4" insert to the t-mount.
connecting the t-mount to the d70
putting the insert into the lens mount on the telescope & pointed the
telescope at pollux.

I can see the star as a crisp point in a 25mm eyepiece, but I can only see a
blur through the camera, which starts to get sharper as I focus down - but
before I get a crisp point through the camera, the focus movement reaches
the lower limit - which seems to be the same problem I have with the
variable setup and the use of a lens in the adapter.

Any ideas where I am going wrong?

On Fri, 9 Feb 2007 19:11:22 -0000, "Callum" <no@spam.com> wrote:

Hi there

thank you for the reply.

I have just tried this:

connecting the 1 1/4" insert to the t-mount.
connecting the t-mount to the d70
putting the insert into the lens mount on the telescope & pointed the
telescope at pollux.

I can see the star as a crisp point in a 25mm eyepiece, but I can only see
a
blur through the camera, which starts to get sharper as I focus down - but
before I get a crisp point through the camera, the focus movement reaches
the lower limit - which seems to be the same problem I have with the
variable setup and the use of a lens in the adapter.

Any ideas where I am going wrong?

This isn't an uncommon problem when imaging with a Newtonian. When you
use an eyepiece, the proper focus is obtained when the focal points of
the objective and eyepiece coincide, which happens behind the eyepiece,
down inside the focuser tube. To allow the secondary mirror to be as
small as possible, it is desirable to also make this focal point close
to the secondary, so focusers are often rather low profile. Of course,
when you are using a camera there is no way that you can get the sensor
down inside the focuser, so even with the drawtube all the way in you
end up with the sensor behind the focal plane, and with an unfocused
image.

One solution is to switch to afocal imaging, using an eyepiece, a
special adapter, and a lens on your camera (as you have been
attempting). But that is usually not a very good solution, since it
tends to be mechanically unstable, is likely to unbalance the scope, and
presents all sorts of interesting optical aberrations. It is usually
reserved as a method for obtaining high magnification for planetary
imaging, where only a small central field is of concern.

The best solution is to relocate your primary mirror. The mirror cell is
probably held in place by three screws through the tube wall. If you
provide three new holes an inch or two further up the tube, and
reposition the mirror, you will push the focal plane far enough outside
the focuser that you can use a camera. Of course, you may also have a
focuser that is very long, and replacing it with a low profile focuser
may work. In any case, you are looking at some sort of simple
modification of your telescope.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Am I missing something?