Sky and Telescope - February 2018 - 62

S&T Test Report

p The 7-position filter wheel holds enough filters so that imagers can install a full set of LRGB
color filters, as well as 3 additional ones, such as a set of narrowband filters. This image of the
North America and Pelican nebulae (NGC 7000 and IC 5067) was captured with the 102-mm
refractor using 100 minutes of exposures.

tenth of a degree C throughout my test
sessions. A full-resolution, 36-megabyte
image took 15 seconds to read out and
download to my computer.
For years I've wanted to try a largeformat camera on my telescopes, but I
quickly realized that covering the APS-H
chip in the QHY16200A with a wellilluminated, aberration-free image was
more demanding than I anticipated. The
large size of the camera's imaging chip
pushed the illumination limits of some
of my telescope optics. My telescopes and
adapters had been adequate for my KAF8300 CCD camera as well as an APS-C
chip in my modiﬁed Canon T2i DSLR.

p Users with fast f-ratio telescopes that require
a T-adapter to connect cameras may need to
upgrade their focusers. Using a 12½-inch f/4
Newtonian reflector and the T-threaded interface
ring, the author experienced strong vignetting in
this image of NGC 4565 that could not be corrected with flat-field calibration.

FE B RUA RY 2 018 * SK Y & TELESCOPE

The QHY16200A's APS-H format
is roughly ¾ the size of a 35-mm, and
while having a camera with a large chip
is generally a good "problem," astrophotographers considering the QHY16200A
should be mindful of how large and well
corrected the image circles offered by
their telescopes are.
When using the QHY16200A with
my William Optics 102-mm f/6.9 APO
refractor and a 2-inch ﬁeld ﬂattener,
the system produced good corner-tocorner star images with little vignetting. I also had good illumination when
I used a 0.8× reducer/ﬂattener with the
refractor. Users having typical f/7 APO
refractors with ﬁeld ﬂatteners are in
great shape with this camera.
My 8-inch f/5 Newtonian used with
a Tele Vue Paracorr Type-2 coma corrector (which produces f/5.7 with the corrector's 1.15× amplifying factor) showed
some vignetting. But when I mounted
the camera on my 12½-inch f/4 Newtonian reﬂector with its steeper light cone
the image vignetted considerably. Most
of the problem came from the standard
diameter T-adapter I regularly use with
the system. Some of this vignetting was
corrected by ﬂat-ﬁeld calibration, but
the short, fast Newtonian system would
have beneﬁtted from a larger focuser
and coma corrector that offered better
corner-to-corner illumination.

To help with the illumination problem with my f/4 Newtonian scope I had
a friend machine a custom adapter to
mate the camera's 54-mm adapter plate
to the outer threads of the Paracorr
Type 2 coma corrector. This custom
adapter had a clear opening of 50 mm
and was thin enough to maintain the
near-optimum spacing of the imaging
chip to the Paracorr.
The adapter made a huge difference
in corner-to-corner illumination and
should be considered a highly desirable item when using the camera with
2-inch focusers and coma correctors on
fast Newtonians.
Regardless of which scope I used
in my tests, the smooth images were
exciting to view as they downloaded.
The pictures displayed little noise. and
I knew at ﬁrst glance that when several
were stacked together, they had the
potential to produce an outstanding
ﬁnal image.

The Bottom Line
The QHY16200A system is a high
performing, solidly built addition to the
astronomical imaging market. Astrophotographers with beefy mounts, rigid
OTAs, and robust focusers should have
the fewest concerns over the camera's
weight. Folks with lightweight instruments may need to upgrade or shore up
their systems with larger clear apertures, substantial focusers, and perhaps
effective counterbalance conﬁgurations
to realize the camera's full potential.
If you purchase the QHY16200A
ﬁlter wheel and QHYOAG-M and have
an optical system that fully illuminates
its chip with a relatively aberrationfree image circle, you can expect to
have truly outstanding imaging results.
If you are, however, like me, it may
be time to start tinkering with the
telescope you have or consider some
upgrades that would make it a worthy
match to this powerful imaging system.
■ Retired news photographer and
Contributing Editor JOHNNY HORNE has
long known he needs bigger and better
telescopes. Reviewing the QHY16200A
only made that more apparent.

Sky and Telescope - February 2018

Table of Contents for the Digital Edition of Sky and Telescope - February 2018