Guided prime focus photography is what is needed to get color photos of nebulae and
galaxies. It is more exacting, because the exposures take time
to complete. First of all, you will need a telescope that has dual-axis drive and a hand
controller. Then, in addition to the camera and T-ring,
you will need the following: 1) an off-axis guider, which attaches to your T-ring on one
end and screws onto your catadioptric rear cell or your drawtube on the other.
It allows you to attach a camera to the telescope, but also to use an illuminated reticle
eyepiece to keep visual track of a guide star; 2) an
illuminated reticle eyepiece, which goes into the eyepiece holder of the off-axis guider.
The illuminated reticle is either run by batteries or plugs into the power panel of the
telescope. The eyepiece has a crosshairs in it, and lights up
red when you turn it on. While you are taking a photo, you place a star that is in the field
of view of the object you are photographing into the center
of the reticle, and using the hand controller to adjust your telescope, you can make sure
that guide star stays right where you placed it.
A cable release is imperative for all astrophotography. Touching the camera with your
hand when you press the shutter button will shake the camera a
little, which will throw your picture off by thousands of miles.
If you have a equatorial reflector, you will not be able to use an off-axis guider and
illuminated reticle to guide on a star, since there is no way
for the off-axis guider to attach to the telescope. Instead, you will need to use a basic
or variable camera adapter attached to your focuser,
just as you would when doing eyepiece projection. Then, you need to attach a "guidescope" to the top of your telescope (a small refractor works well,
among other choices). You place an illuminated reticle in the focuser of your guidescope, and after making sure that your guide scope is aligned
with your main tube, you guide that way, making corrections with your hand controller if
the star drifts from the center of the reticle.
CCD Imaging
CCD Imaging is the ultimate in astrophotography today. Not too long ago, the science
of capturing photons of light onto a light sensitive microchip was
for observatories and the very rich. Today, thanks to the computer age and the fact that
the amateur market was hot for less expensive imagers, we
have several cameras to choose from, ranging from about $300 to over $6,000. if you
are willing to spend
approximately $750+ for a camera, already have a telescope with a dual-axis drive,
and you are also the owner of a computer that is not a
relic... you too can produce images of galaxies and nebulaes with pretty darned good
resolution that you can be proud of. More money equals more
resolution.