2019-07-01_Australian_Sky_&_Telescope

72 AUSTRALIAN SKY & TELESCOPE July 2019

ASTRONOMER’S WORKBENCH by Jerry Oltion

A 3D-printed binoscope

No workshop? No problem.

WHEN ROBERT ASUMENDI looked

through a binocular telescope, he

realisedseveralthingsat once:

• Binocular vision is vastly more
  comfortable and pleasurable than
  monovision. (So much so that Hans
  Lippershey had to build a binocular
  before the patent office would even
  consider his patent application for
  thetelescopein1608.)


• Binocular vision helps to compensate
  forRobert’ssevereastigmatism.


• Despite wanting a binocular
  scope, he also wanted grab-and-go
  portability, wide fields and enough
  aperture to provide satisfying views
  of deep sky objects.
  Robert searched for a scope that would
  satisfy all his requirements but came
  up empty. “There’s no commercial

ALL IMAGES COURTESY OF THE AUTHOR UNLESS OTHERWISE NOTED

scope that delivers all those things,” he

reports. “So I made it.”

Robert faced two simple challenges:

He had never built a telescope before,

and he didn’t have any workshop space.

He did, however, have a couple decades

of experience with computers. “So

my computer became my workshop,”

he says. “I designed everything in a

parametric computer-aided-design

(CAD) program.”

And because we’re now living in

the 21st century, 3D-printing the

parts became a natural outcome of the

design process. That enabled Robert

to test aspects of his design without

building the entire thing at once. He

could examine a real physical object,

modify its parameters in the computer,

and print another to see how it worked.

He didn’t have a 3D printer at first, so

he jobbed out his designs to an online

printing service. That worked nicely,

but he quickly realised he wanted a 3D

printerofhisown.Besideseliminating

shippingcosts,it madeunit-testingof

smallcomponentsmorepracticaland

eanbledhimtooptimisesettingsfor

eachpart,whichmadeforfantastic,

repeatableresults.

Hestartedwiththefocusers.He

wantedtouse2-incheyepieces,buthe

couldn’tfindanycommercialfocusers

thatwouldputthedrawtubesclose

enoughtogetherformostpeople’s

interpupillarydistance(thespacing

betweeneyes).Hesettledona modified

Crayforddesignthatenablesthe

drawtubestonearlycontacteachother.

Andoncehe’dstarteddesigning,he

justkeptgoing.Couldhe3D-printa

filterwheel?Couldhe3D-printthe

secondarymounts?Couldhedesign

channelsinthosesecondarymountsto

runwiresfordewsensorsandheaters?

Hecould,anddid.It wasan

iterativeprocess,eachstepbuilding

ontheprevious,bothintellectually

andphysically.Robertsays,“The

resultingpartswouldhavebeen

extremelydifficult,costlyorheavy

tomachine.Theuniquehoneycomb

structureof3Dprintsletsyoudesign

lightweight,sturdycomponentsthat

justwouldn’tworkinothermaterials.

And,ofcourse,witha binoscopeyou

needtwoofeverything,andseveralof

thecomponentsaremirrored.With

3Dprinting,youjustusethemirror

tRobert Asumendi’s ‘Drifter’ binocular scope

is a marvel of design and execution.

pTop: The eyepiece adapter fits solidly into

the focuser thanks to neodymium magnets

embedded in each part. Bottom: The 3D

printer generates an eyepiece adapter. This

piece took about 20 minutes to print and cost

about $2.30 in materials.