Sky & Telescope - December 2023 - 60

UNLESS OTHERWISE NOTED, ALL IMAGES COURTESY OF THE AUTHOR;
GRID PAPER: DASTAGIR / SHUTTERSTOCK.COM; MEASURING TOOLS:
OLEKSI I ARSENIUK / SHUTTERSTOCK.COM
CUSTOMIZATION by Jerry Oltion
I
often tell people, " You don't truly own your telescope
until you've drilled a hole in it. " I can immediately tell the
builders from the buyers, because the builders all nod and
agree, whereas the people who just buy things from commercial
vendors laugh nervously and edge away, often carrying
their precious factory-built optics with them.
It's true, though: Ownership brings with it the opportunity
to change the way something works - to customize it
to match your wants and needs. It may seem a little scary to
poke holes in something brand-new, but if those holes make
it more useful to you, then why not?
In my monthly Astronomer's Workbench column I often
describe specific modifications that people have made to
improve the way their scope works, but in this article I want to
talk about the concept behind them all. Why should you alter
a scope that you paid good money for? Can you really improve
on something that was designed by professional engineers?
Of course you can!
Without disparaging commercial telescope manufacturers,
let me say that everyone has to make compromises between
cost and quality, between form and function, between desire
and reality. No design can be everything to everyone; that's
why we have more than one telescope to choose from. And
that's why you might find yourself contemplating a change to
a scope that's close to but not exactly what you want.
Lefty or Righty?
Consider something as simple as which side of a Dobsonian
you prefer to view from. People argue about the merits of
pushing a Dob away from you as you track objects in the sky
versus pulling it toward you, but there's no right or wrong way.
It's a personal choice. Some like it lefty, some like it righty.
But suppose you got a great deal on a scope, only it's rigged for
pushing and you're more of a puller. What can you do?
You can move the focuser to the other side of the tube.
On some scopes that's as easy as rotating the tube 180°
when you set it in the rocker box. But even if you can't do
that - if your altitude bearings are semicircles, for instance,
or if the focuser isn't perpendicular to the side bearings -
you can still move the focuser itself. Yeah, that means cutting
a big ol' hole on the other side of the tube, plus drilling
holes for the mounting screws. You also have to swivel
the secondary mirror around and cover the hole where the
focuser used to be. So what? It's a simple modification. You
know exactly where to drill the holes and how big to make
them, because the manufacturer already did that for you
on the original side. And here's a little secret: If you're off a
little, you can fudge it into place by elongating the mount
holes, shimming the focuser, or even shifting the secondary
up or down the optical axis.
This modification isn't restricted to solid optical tube
assemblies (OTAs), either. In fact, it's often even easier with a
truss-tube scope. You can usually just re-mount the secondary
cage 90° or 180° around without modifying anything.
Your focuser will be upside-down, but it'll still work. If that
bothers you, you can turn it around, using the exact same
mounting holes as before. No drilling required. Some focusers
are even rotatable within their mounts, so check for that
first before you go to more trouble than necessary.
Flipping the OTA or the secondary cage means your finder
will wind up underneath rather than on top. So, unless you
want to crawl under your scope to aim it, you'll have to remount
the finder. Big whoop. It's easy: Drill two more holes.
Righting Wrongs
One of my astronomy-club members, Dan Beacham, bought
a 20-inch f/3.6 ultra-compact Dob in the hope that he
wouldn't need a ladder for observing, but the focuser was
NOT QUITE LADDER-FREE Dan
Beacham's scope came from the
manufacturer with the focuser at an
awkward angle.
60 DECEMBER 2023 * SKY & TELESCOPE
TURN THE CAGE Rotating the secondary
cage on a truss Dob is simple. You might have
to make new mounting brackets, but that's
what angle iron is for. Note the original factory
mounting point farther back to the right.
ALL BETTER With the focuser now
aimed horizontally, Dan's scope is
much easier to use.
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Sky & Telescope - December 2023

Table of Contents for the Digital Edition of Sky & Telescope - December 2023
