The following text provides a little
information about my current imaging equipment rig. To see diagrams of
the rig,
please click
here. At some point, I will also try to post some photographs
of the rig
when it is set up.
Telescope mounts come in two broad categories; alt/az mounts
and
equatorial mounts. An alt/az mount allows the telescope to be moved
freely in altitude (up/down) and azimuth (left/right); much like the
telescopes you see on the seafront for checking out ships! An
equatorial mount is aligned with the Earth' axis of rotation, making it
easier to track celestial objects as they traverse from East to West.
Equatorials come in various forms, including the Germen Equatorial
Mount (GEM) and equatorial fork mounts.
Unless you are going to concentrate on lunar and planetary
photography,
you are really going to need an equatorial type mount (GEM or am alt/az
with an equatorial wedge). The mount will need to be driven in the
right ascension and declination axes (the celestial equivalent of
longitude and latitude respectively) and will need to have
sufficient
load capacity to carry for your telescope, guidescope and any
cameras.
While it is a problem if any form of portability is required, sheer
physical heft is also an advantage for any mounting system; physically
massive mounts are less prone to vibration than light mounts, anf a
stable platform is a must for astrophotography.
The EQ6 Pro is a solid and dependable German Equatorial Mount
(GEM) at
a price that will not break the bank. With a precision stepper motor
based GOTO system and an ST-4 compatible guider port, the EQ6 Pro is
well suited to astrophotography. The sheer mass of this mount and its
2" steel tripod is another factor that makes this a good choice for
budding astrophotography, though you'll have to have a strong back if,
like me, you haul this beast out into the backyard every imaging
session ;-)
The EQ6 Pro accepts Vixen style dovetail bars. I have a
Telescope
Service Dual Mount system that permits two Vixen dove tail bar mounted
instruments to be loaded onto the mount in a side-by-side
configuration.
I use two Telescopes in the course of my astrophotography; an
imaging
telescope and a guidescope. The imaging telescope is a GSO 200mm f/4
Newtonian fitted with a Baader Multi-Purpose Coma Corrector (MPCC). I
have the delux version of this telescop
with a
larger secondary mirror to illuminate sensors larger
than APS format.
While Astronomy magazine advertisements are often dominated by
catadioptric
telescopes, most notably Schmitt Cassegrains, do not rule out the good
old
Newtonian. They have a simple optical design whose main flaw, off-axis
coma,
can be easily and well corrected with an inexpensive corrector such as
the
Baader MPCC that I use. My 200mm Newtonian,
complete with MPCC cost in the order of £550. The 200mm GSO
Newtonian has a quality
Crayford style focuser with a 10:1 microfocuser that makes precision
focusing without image shift possible.
My guidescope is a Skywatcher
80mm f/5 achromatic refractor. A telescope of this type can
be
obtained
for a little over £100. While the 400mm focal length is a
little
on the
short side for guiding purposes, I have not found this to be a problem
using the
PHD guiding software. On the plus side, this is an excellent and highly
portable rich filed telescope that can easily be used on a camera
tripod as a
"grab-and-go" instrument. Also, the shorter focal
length
and bigger field of view make it easier to find a suitable guide star
than it might be using a longer focal length instrument.
I use two cameras in the course of my astrophotography; an
imaging camera,
which is placed at prime focus of my GSO 200mm Newtonian, and a
guidecamera,
placed at prime focus of my 80mm refractor.
My imaging camera is my biggest investment to date at £1399.
It is a
QHYCCD
QHY8. This is a single-shot colour 6 MPixel (APC format sized sensor),
Chinese made camera using the same
Sony SuperHAD sensor that is used in the Starlight Xpress SXVF-M25C.
The camera
has two-stage thermoelectric cooling (TEC). I had previously used a
Meade DSI Pro
II, but the lack of TEC and the need to shoot luminance, red, green and
blue
frames made an already difficult task even more challenging! I am
slowly
getting to know this camera, and feel sure that it will produce great
results
over time. Because I live in a twon location with fairly heavy light
pollution, I couple my QHY8 with a Light Pollution Supression (LPS)
filter. I use the Huetech IDAS filter as this is generally recognised
as the best currently available filter. However, I have successfully
used the significantly less expensive Antares LPS filter to good
effect. For more detail on the QHY8, click
here.
My guide camera is a QHYCCD
QHY5. This is a very good choice
for use with the EQ6 Pro as it is compatible with PHD and other free
guiding software such as Guide Master and has an on-camera ST-4
compatible guide port, obviating the need for a USB to ST-4 interface
such as the Shoestring Astronomy GPUSB. What's mode, it only costs in
the order of £150! With a resolution of 1280x1024 pixels, it can even
double as a half decent camera for lunar and planetary work.
Unless
you fancy using a 35mm camera and
making manual guiding corrections for many hours, it is all but
impossible to
avoid computers in the pursuit of astrophotography. Computers can be
used to find
your quarry using digital star charts, control the image acquisition
process,
make automatic guiding corrections, post process the raw data and
finally post
your image on the Internet to share with others!
Astrophotography
is not an inexpensive
hobby. You will need a good mounting system, the best quality optics
that you
can afford and cameras for imaging and guiding. While there is little
that can
be done to short cut on these items, there are free or extremely
inexpensive
software products that can be used to get you going. I am currently
guiding,
imaging and processing on free or inexpensive software and, from
current
experience, I see no reason to do otherwise. To find out more, click here.