22" Obsession UC

I use 3 fans at the rear of the mirror for extraction and two fans opposite each other projecting air at the front mirror.

Vibration of the fans is eliminated by specially selected rubber grommets. The two opposite fans at the front face
of the mirror 'fight each other to a draw' so to speak. This method destroys the boundary layer and prevents dewing.
I've done stretches of 5/6 hours with good results.

Measurement of oscillation was carried out by a trial and error while checking star images using video camera. The image of the Airy disc was consistent after some geometrical positioning of the fans in relationship to each other.

Eamonn A

www.kingslandobservatory.com

Keeping with the topic at hand I was just looking at prices of the obsession 18" F4.5 and the 20" f5, the 18" been $6,495(4,415E) and the 20" been 6995(4,775E) this equals to 360 euro in the difference, Now when it comes to the 18" UC its the same price as the 20" F5, Iv two questions to ask,

1) Would you go for the 20" over the 18" UC? More bang for the buck Vs Compactness.

2) Since less wood and crafts/work is needed in the 18" UC compared to the standard 18" wouldn't you think it be some way cheaper than the standard? meaning less material is used.

Yea good points there John, I suppoose that newness of the UC design is gonna mean it'll cost more.

As for selecting one, its like this.
If you can transport the heavier scope and dont have any plans on trying to get it on a plane, then go for it as its a larger aperture, otherwise get the lighter UC scope.
That'd be my thinking if I was getting one now.

Jononeill wrote:

1) Would you go for the 20" over the 18" UC? More bang for the buck Vs Compactness.

2) Since less wood and crafts/work is needed in the 18" UC compared to the standard 18" wouldn't you think it be some way cheaper than the standard? meaning less material is used.[/quote]

This one would depend on intended use. The bulk and weight of the 20" would prevent portablity, if you need to travel to dark sites then the 18" is the way to go and I guess that's why it commands a a bit of a premium even though less materials go into its manufacture (plus when you take shipping into account the cost does vary significantly).

That said, as Michael has noted below an 18 inch mirror is pretty heavy to be lifting in and out of a car, the mirror box on the 18" UC weighs 28 kgs (the total weight of the scope when assembled is 41 kgs) - you might want to befriend a chiropractor before buying one of these as a portable scope!

Joking aside, if you have a lot of boot space in your car the 18" UC allows you to attach wheels to the mirror box so with a couple of ramps you can wheel it into and out of your car with litle effort. The rest of the pieces are certainly manageable.

For me though, I'd prefer to spend that sort of money on something else as dobs have limited use for astrophotography. The Celestron CGE 1400 (XLT) 14” SCT or Meade 14" LX200 ACF are both in the same price bracket. But if portability was an issue (or if I had no interest in astrophotography) I'd have a different opinion! Although the heaviest component in the Celestron weighs less than the mirror box in the 18" UC - although I'm sure this wouldn't be enough for anyone suffering with aperture fever!

Some very good points there anthony. But for me seeing with the naked eye far beats photographs well depends on what your viewing.

As for putting the money into astrophotography I much rather invest in a good mount like an AP 1200 and a fast refractor like a WO 110. but I wouldnt say no to a 14" CGE PRO

A question for all would you rather more aperture or easy of transport, reason I ask this is some people can manage both :laugh:

I think the question is really about weather you would buy
the UC or a regular Obsession.
To bring C14s and mounts into it is kinda like opening it up
to a question of if you had X amount of money what would you buy
to suit you?

The 22'' Obsession UC would hands down be the ultimate
portable large scope.
Bad backs or not - it would be a breeze to transport as opposed to
something similar in mirror size.

I have to say though that the UC design is simply not suitable
for the Irish weathe
The open design would cause you too much heartache with moisture /
due and IMHO you would simply not get the use out of it on this island.

Buy it to have as a compact large ap scope to bring to another place
(eg Canarys) then WOW, yeah... It'd be the D's B's.

For me I'd still consider the smaller 18'' one as a travelling companinon,
but the 22'' would be a monster and too heavy in reality.
As far as I am concerned now,
the bigger an aperature I can get for my money the better.
Imaging is one thing and like computers is changing fast,
but a big scope for visual observing will always hold it's own.