Australian Sky & Telescope - April 2018

70 AUSTRALIAN SKY & TELESCOPE April 2018

imagetook15secondstoreadoutand

download to my computer.

ForyearsI’vewantedtotryalarge-

format camera on my telescopes, but I

quicklyrealisedthatcoveringtheAPS-H

chipintheQHY16200Awithawell-

illuminated, aberration-free image was

moredemandingthanIanticipated.The

largesizeofthecamera’simagingchip

pushedtheilluminationlimitsofsome

of my telescope optics. My telescopes and

adaptershadbeenadequateformyKAF-

8300CCDcameraaswellasanAPS-C

chip in my modified Canon T2i DSLR.

TheQHY16200A’sAPS-Hformat

isroughly¾thesizeofa35-mm,and

whilehavingacamerawithalarge

chip is generally a good ‘problem,’

astrophotographers considering the

QHY16200Ashouldbemindfulofhow

large and well-corrected the image

circles offered by their telescopes are.

WhenusingtheQHY16200Awith

my William Optics 102-mm f/6.9 APO

refractoranda2-inchfieldflattener,the

system produced good corner-to-corner

star images with little vignetting. I

alsohadgoodilluminationwhenI

useda0.8×reducer/flattener with the

refractor.Usershavingtypicalf/7APO

refractors with field flatteners are in

great shape with this camera.

My20-cmf/5Newtonianused

with a Tele Vue Paracorr Type-2 coma

corrector(whichproducesf/5.7with

the corrector’s 1.15×amplifying factor)

showed some vignetting. But when

Imountedthecameraonmy31.8-

cm f/4 Newtonian reflector with its

steeperlightconetheimagevignetted

considerably.Mostoftheproblemcame

fromthestandarddiameterT-adapter

Iregularlyusewiththesystem.Some

of this vignetting was corrected by

flat-field calibration, but the short,

fastNewtoniansystemwouldhave

benefittedfromalargerfocuserand

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, 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

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 realise

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 aberration-

free 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 JOHNNY

HORNE has long known he needs bigger

and better telescopes. This review only

made that more apparent.

SThe 7-position filter wheel holds enough filters so that imagers can install a full set of LRGB

colour filters, as well as three 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.

SUsers with fast f-ratio telescopes that

require a T-adapter to connect cameras may

need to upgrade their focusers. Using a 31.8-

cm 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.

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