T-mount questions

On Jul 11, 10:22*am, (Paul Ciszek) wrote:
In article ,

wrote:

Depending on your finances and other factors you might be better off
using different scopes and prime lenses to obtain a range of focal
lengths, and use a Barlow to obtain a specific FL.

My original desire was for a telephoto lens with a focal length of
at least 400mm. *As camera lenses, these are hideously expensive.
Then I discovered "mirror lenses", but it sounds like the ones being
made today stink. *Someone here pointed me to the Orion Maksutov-
Cassegrain scopes which are nicely priced and will go on a camera
tripod, but their focal lengths start at twice what I had in mind.
My worry with refractor telescopes is that any affordable ones are
going to have chromatic aberration.

Consider a 1.25-inch Prime Focus Kits, # KM43:

http://www.telescopeadapters.com/ind...ll_olympus.htm

and an astro-photo-modded Orion Starblast:

http://www.telescope.com/Astrophotog.../57/p/9974.uts

Orion should be able to tell you if the scope will reach focus with
your camera and adapter.

For terrestrial photography you might need an extension tube to reach
focus.

On Jul 11, 9:33*am, (Paul Ciszek) wrote:
In article ,

wrote:
On Jul 10, 11:58 pm, (Paul Ciszek) wrote:
In article
,

What kind of camera do you have? Specific model please. There are
short t-rings for DSLR and long t-rings for MIL cameras.

My Olympus OM-D E-M5 is a micro-four-thirds system camera.

Based on that info, I would conclude that you need the second of the
three links that you included in your original post since your camera
appears to be a DSLR and not an MIL.

No, the micro-four-thirds standard is mirrorless. *Lenses made
specifically for the micro-four-thirds system can take advantage
of this and get the lens closer to the sensor.

And all of the links I included were T-mount adapters claiming to
be specifically for the micro-four-thirds standard.

Then, you would likely use the products shown in your first and third
links to connect an older or third-party lens to your camera, or
perhaps use the product in the second link along with an additional
adapter to connect your camera to a telescope's focuser.

On Wed, 11 Jul 2012 12:49:07 -0500, William Hamblen
wrote:
Mirror lenses, even the ones from the big camera companies, are
notorious
for being soft. Plus they are slow - typically f/8. If you said
what
camera this is for, and what you are going to shoot, I've forgotten.
You can still get a second hand Nikkor mirror lens for a reasonable
price. It won't autofocus. I don't think Canon ever put out an EF
mount
mirror lens.

There are adapters. And the Canon EOS has a mount larger than most so
you can, with an appropriate adapter, mont almost any lens on a Canon
EOS. You can for instance, with an adapter, mount a Nikon lens on
Canon EOS, but you cannot mount a Canon lens on a Nikon camera
because there isn't space enough on the Nikon camera.

I have gathered a collection of mirror lenses, with focal lengths of
300, 500, 600 and 1100 mm. They all require adapters to fit on the
EOS.