View Single Post
  #8  
Old 20-12-2018, 12:12 PM
FredinBroome's Avatar
FredinBroome (Fred)
Registered User

FredinBroome is offline
 
Join Date: Dec 2018
Location: Broome WA
Posts: 74
Quote:
Originally Posted by gary View Post
Hi Fred,

First a disclaimer. Obsession Telescopes are a customer of ours.

In fact, many telescope manufacturers are customers of ours
but since you were asking about the Obsession I will confine
my comments to them.

When you mention the 22" and "transportable" you will be referring to
the Obsession 22" UC (Ultra Compact).

Dave Kriege of Obsession literally wrote the book on building large
Dobsonian telescopes and the design outlined in that book gave
rise to many amateur telescope makers (ATMs) and small businesses
either making scopes identical to the blueprints in the book
(commonly termed 'Obsession clones') or inspiring them to customize,
refine and embellish the "classic" design further into bespoke designs.

All the Obsession telescopes use a truss pole design that allows the
scope to be broken down into three primary components - namely
the base with the groundboard, rocker and mirror boxes, the top end,
which holds the secondary mirror and focuser and the truss poles
themselves.

The original Obsession design - what is now referred to as 'the Classic' -
the base components are fabricated in marine ply. This, along with
a top end that has a diameter slightly larger than the primary mirror
and is roughly the size of a musical drum, makes the scope, even when
broken down, relatively heavy and bulky to transport.

For example, when I transport an Obsession 18" Classic I have stored in
my garage, it takes up the entire back of a Subaru Forester with the
back seats folded down with not very much room to squeeze in much else.

Around 2006, when fuel prices began rising in the United States, Americans
began to downsize their cars.

Responding to this, Obsession brought out a new design called the
Ultra Compact or UC for short.

Dave Kriege showcased the 18" UC at the Texas Star Party in 2007
and in front of an astonished audience, removed the components of the
scope from a compact carrier box and assembled it on stage in the
space of a few minutes.

Dave had designed a scope that would fit in the 'trunk' of a small car.

A group I volunteer with, which already owned a large number of
Obsession Classics, purchased one of the first 18" Obsession UC's
and Dave Kriege, a regular visitor to Australia, brought it with him
on the flight to Sydney.

I was custodian for the scope for a while and by comparison, the entire
18" UC fitted in the back of the Forester station wagon area with the
back seats folded up and room to spare.

Whereas when I move the 18" Classic I use a ramp and wheelbarrow
handles to get the base in and out of the vehicle, the 18" UC can
safely be lifted by a couple of average people or by an individual fit
and strong one.

Later, Obsession introduced the 22" UC.

Whereas with the 18" Classic I transport a step ladder with it in order
for an observer to view through the eyepiece at modest zenith distances,
with the 18" UC I can observe at the zenith by standing on a milk crate.

If you have young children, it is much easier for them to access the
eyepiece on the 18" UC compared to the 18" Classic.

The Classic design is heavier, the truss poles thicker and as a result the
Classic is a sturdier scope to use in a breeze. If you have a larger
vehicle and transportation is not an issue, stick with a "Classic" design.

If you have a family and the vehicle won't accommodate both them and
the scope and you don't want to resort to transport the scope in a trailer,
consider a "UC" design.

As they say, the best scope is the one that gets used most often.

You are lucky to live in Broome because of the skies. The one disadvantage
is that it puts some distance between you and the nearest sizeable
club or star party in order to look at and operate other people's
scopes, which is what most of us would normally recommend before
buying a new scope.

The premium Dobs, like the Obsessions, come with mirrors made by
mirror makers in the United States or Australia and as a result, across the
board of all mirrors made, the mirror performance, due to better
quality control, tends to be guaranteed to be better than the commodity
mirrors manufactured in the Far East. If for some reason you are not
happy with the mirror's performance, with the premium Dobs one has
the opportunity to strike up a dialogue with the actual mirror maker.

The movement of the premium Dobs also tends to be much nicer
compared to the commodity Dobs out of the Far East. When one reads
the Kriege book on Dobsonian telescope design, it is filled with the physics,
engineering and mechanics of why the scope is built the way it is.
Moments of inertia, friction and stiction, truss pole rigidity as a function
of truss pole diameter and so on.

The Dobsonian designs out of the Far East are often dictated by other
requirements, such as can they be sold in a flat pack and how many
will fit into a standard shipping container.

When you first push a nice premium big Dob around, I find the experience
akin to having the opportunity to drive some premium high performance
European sports car. Dave Kriege uses the expression "buttery smooth"
when referring to the feel of the motion of his own scopes around
their respective axes. It's a good description and it comes as a revelation
the first time you get to push one around. Like behind the wheel of the
European sports car, it is very refined, which is really nice.

Best Regards

Gary Kopff
Managing Director
Wildcard Innovations Pty. Ltd.
20 Kilmory Place
Mount Kuring-Gai NSW 2080
Australia
Phone +61-2-9457-9049
Fax +61-2-9457-9593
sales@wildcard-innovations.com.au
http://www.wildcard-innovations.com.au

Image 1 - Obsession 18" UC in the back of my Subaru - room for passengers
Image 2 - Obsession 18" Classic in the back of my Subaru - a bit of a squeeze
Hello Gary,


Thank you for a very concise history on Obsession telescopes. Very interesting read.


Cheers,
Fred
Reply With Quote