70 AUSTRALIAN SKY & TELESCOPE July 2019
witha smallregionofinterest.The
manualdoeswarnaboutthis,butit was
stillaneyeopenertofillmorethan 50
gigabytesofdiskspacerecordingabout
a dozenvideoclipsmyfirstnightout.
Thesevideoswerelaterprocessedwith
third-partysoftwareincludingRegiStax
andthefreewareAutoStakkert!3.Ontothedeepsky
OncetheMoonwasoutoftheevening
skyit wastimetotrytheDSI-IVfordeep
skyimaging.It’sherewhereI found
roomforimprovementwithSkyCapture
thatI hadn’tnoticedwhenshooting
stillimagesduringmybenchtesting
ina relativelybrightenvironment.For
example,whenframingfaintdeepsky
targets,I usuallymakeshortexposures
of 20 to 60 secondsandstretchthemto
extremestoseewhat’sinthefield.With
SkyCapture, theimagethatappearsat the
endofeachexposurecan’tbestretched
onscreenasis.Youcanexaminea
histogramofthedisplayedimageand
makeadjustmentstosettheblackand
whitepointsfordisplayinga stretched
image,butthesesettingsdonottake
effectuntilyoumakethenextexposure.
Thebestworkaround,apartfrommakingmultipleexposuresorguessing
at thecorrecthistogramsettingsbefore
shootingthefirstone(somethingthat
is possiblewithexperience),is tofirst
savetheimageandthenre-openit with
SkyCaptureandusetheRangefunction
intheProcessmenutoactivelystretch
theimageonscreen.It’sa bitclumsy,
nottomentiontime-consuming,
especiallyif you’retypingfilenames
andthelikeinthedarkwithgloveson.
Therewerealsofeaturesofthe
softwarethatI couldn’tgettowork,
includingtheautomaticfunctionsfor
dark-framesubtractionandflat-field
correction.Theseissuesmaybeunique
totheDSI-IVupdateofthesoftware,
sinceI noticedthattheflat-field
functionisn’teven
discussedintheolder
user’smanualthat
I mentionedearlier.
Regardless,I don’t
likeusingautomatic
calibrationroutines
duringimage
capture,sinceI prefer
havingunmodified
rawdatathatcanbe
processedlaterwith
variouscalibration
methods.Assuch,Isimply made standard dark and flat-
field exposures with the DSI-IV and
processed my light frames with third-
party software.
Despite my nit-picks with
SkyCapture, I did use the software
exclusively for all the imaging I did
with the DSI-IV, and I’m happy with
my results. Indeed, most astronomical
cameras come with only the most
rudimentary image-capture software
(and some don’t come with any),
so getting a package as decent as
SkyCapture included with the purchase
of the DSI-IV is really a plus.
In the end I found the DSI-IV to
be a very versatile camera that can
satisfy the needs of many of today’s
astroimagers. It’s a camera that can
shoot excellent astronomical video and
seamlessly transition to shooting decent
long-exposure deep sky images. It can’t
quite match the deep sky performance
of a cooled, 16-bit, astronomical CCD
camera, but the DSI-IV is still a big step
up from the astrophotography that can
be done with DSLRs. And it comes with
a very attractive price tag, especially
given the software that’s included.■DENNIS DI CICCO has been reviewing
astro equipment for more than 45 years.pSwitching the DSI-IV from shooting astronomical videos to making long exposures of deep
sky objects involves only a few mouse clicks with the camera’s included Meade SkyCapture
software and, for optimum results, connecting the 12-volt power supply for the cooling system.
These views of the Cone Nebula and Christmas Tree Cluster in Monoceros (left) and Horsehead
Nebula in Orion (right) were each assembled from fifteen 10-minute exposures through a
hydrogen-alpha filter with a 20-cm f/3 telescope.qDuring his testing, the author exclusively
used the SkyCapture software supplied with
the DSI-IV for his astronomical imaging.
As explained in the accompanying text, he
feels the software’s long-exposure mode
could stand some improvement but was still
effective for capturing images. The screen
grab seen here displays one of the 10-minute
exposures used for the image above and was
made while the camera was in the process of
running the automated exposure sequence.AS&T TEST REPORT