WWW.ASTRONOMY.COM 59camera. This camera’s detector is a stan-
dard 36x24 mm chip with 9-micrometer
pixels. It provided an image scale of 5.35"
per pixel, which yielded a huge field of
view of 6° by 4°.
This setup can take in sweeping views
of large objects. The scope’s advertised
image circle is 42 mm, and the full-frame
camera worked well with it. Once in focus,
I used CCD Inspector to measure the col-
limation and curvature.
Collimation was spot on (within 1 pixel).
Curvature measured 10 to 11 percent, a
quite respectable number. My f lat-field
analysis shows light loss to be 8 to 9 percent
in one corner and less in others. This means
vignetting is minimal and probably due to a
bit of tilt in the system with the large chip.
When I zoomed in to a full-size image,
I noticed that the stars in the extreme
corners of the chip were not perfectly
round but slightly elongated. It wasn’t
objectionable, however. Being right at the
edge of the image circle, the optics did a
decent job of providing good correction
out to the edge of the field.
Also, as far as I could tell, the focuser
did a good job holding this nearly 5-pound
camera without sagging. With an adapter
and a spacer on the camera, it threaded
right onto the rear of the focuser. The
camera-scope combination came to focus
about 15 mm out from the fully racked-in
point. The camera was easy to rotate to any
desired angle. Because the focuser held this
large camera well, it will have no issue
holding other CCD cameras and DSLRs.
I also tested the scope with my QSI 583
camera, which uses an APS-C Kodak 8300
chip with a diameter of 22.5 mm and
5.4-micrometer pixels. This camera
resulted in a image scale of 3.21" per pixel
and a large field of view of 3° by 2°. With
just the adapter threaded into the camera,
this setup came to focus about 9 mm out.
The first test images showed excellent cor-
rection all the way into the corners.
Curvature measured again around 10 to
11 percent, and a f lat-field analysis showed
light loss in the corners to be only around
4 percent. I saw no vignetting. With either
camera, the focal length measured out at
349 mm, which is right on the money with
the advertised 350 mm focal length.
From these initial tests, I concluded that
excellent images are possible with either a
full-frame or APS-C camera.Imaging
After waiting a week for the weather to
improve (including a near miss by a tropi-
cal storm), I finally got some clear nights
to put the scope through its paces. With
the SBIG camera, I targeted the globular
cluster M53 and its companion NGC 5053.
With the QSI camera, I imaged the globu-
lar cluster M5 and later at night the region
of the Lagoon and Trifid nebulae (M8 and
M20) in Sagittarius.The extremely wide field afforded by
the latter instrument allowed me to cover a
huge portion of the sky. This scope’s fast
(f/5) focal ratio made acquiring the data
quick. After processing the images, I was
happy to see that there were no optical
issues whatsoever.Final thoughts
The 70mm Astrograph Quadruplet APO
Refractor is an excellent scope for imag-
ing. The optics are tack-sharp, and I didn’t
notice any chromatic aberration, telling
me that the lens elements are matched
well. The scope produces little vignetting
using 48 mm adapters. Its ability to bring
all the colors to focus at nearly the same
point was excellent.
Meade’s focuser is also well made and
smooth. I had no issues with sagging, even
when I used a heavy camera. It comes with
a manual rotator, which makes it easy to
set your camera to any angle. The focuser
also can accept focus motors from several
different suppliers.
The rings supplied with the scope could
use some help. You’ll need risers to be able
to set up the scope with a camera on a
Losmandy-style dovetail plate. If you use it
on a mount with a Vixen-style plate, you
may be able to use your camera without
risers. In either case, risers will definitely
come in handy. When I tightened the rings,
the two halves bottomed out, so I wasn’t
sure if the scope was secure within them.
Using a bit of tape as a shim will help
tighten the ring connection.
All in all, Meade’s Astrograph is an
extremely capable and well-corrected
telescope that should let you capture
some spectacular wide-field images.Meade 70mm Astrograph
Quadruplet APO Refractor
Optical design: Petzval system
Focal length: 350 millimeters
Focal ratio: f/5
Focuser: 2 .5" two-speed rack-and-pinion
Dimensions: 12 ¼" by 4½" by 5½" (311 by
114 by 140 millimeters)
Weight: 4.5 pounds ( 2 kilograms)
Includes: Aluminum carry case
Price: $1,19 9
Contact: Meade Instruments
2 7 Hubble
Irvine, CA 9 2618
949.451.1450
http://www.meade.comPRODUCT INFORMATION
Jonathan Talbot is a longtime imager and
equipment tester who lives in Ocean Springs,
Mississippi.The author attached his QSI 583 camera to the Meade and combined 96
minutes of exposures through R, G, and B filters to create this wide-field
image of the Lagoon and Trifid nebulae (M8 and M20). JONATHAN TALBOT
The author captured this image of globular clusters M53 and its fainter
companion NGC 5053. He used an SBIG STL-11000 CCD camera and captured
RGB exposures totaling 80, 80, and 65 minutes. JONATHAN TALBOT