A portable Observing Chair is really helpful for you to comfortably observe objects for longer periods of time. Observing astronomical objects takes practice and some dedication, which is enhanced when you can
look at objects for a while without bending over and contorting your body to look through your eyepiece.
This is very important if you want to observe the planets - the best views of the planets occur when you observe them for long-enough periods of time that atmospheric distortion/turbulence occasionally settles down and you catch a very clear view of our solar system neighbors. (This has been the experience and advice of seasoned planetary observers.) But deep-sky objects also need some study for you to resolve their details.
You need to determine what range of seat heights is necessary for your body height and scope height. Place your scope on its tripod and take two steps: aim it near the horizon and then aim it at the zenith. Figure out what seat height makes you comfortable at both of these conditions. An easy way to do this is to place a 6� folding ladder next to the scope, and use it as a temporary (albeit uncomfortable) seat. Plop your posterior on a low step and look through an eyepiece with the scope aimed at the zenith, and then a high step with the scope aimed near the horizon. See which two steps place you at comfortable heights (low and high) for your scope, and measure the height of both steps from the ground. (You can do this during the daytime - you don�t really need to look at stars to do this.) This will determine what range of observing seat heights you need (although you might include a consideration that other folks may be looking through your scope). In my case, I�m 5�11� tall and I�m comfortable looking through an eyepiece with a seat height of 9� when the scope is aimed at the zenith, and 34� when aimed near the horizon. That�s a rather large, but fairly typical range of necessary seat height adjustments.
There are two primary styles of observing chairs commercially available: a simple round stool, and a sliding-seat chair. These are illustrated in this
photo on the right, from Orion�s offerings although Orion doesn�t necessarily carry the best examples of each, as I explain below.
I am aware of three round stools marketed as observing chairs. Orion has a �Standard Chair� shown on the left in the photo at right, for $37; it has several
fixed height settings requiring manual changes. The �Heavy-Duty� chair, for $120 and shown at the far right in the photo, has variable height settings that
are more easily adjustable. However, in both cases you must get off of the chair to change the height. A more convenient round stool is sold by Al Nagler�s TeleVue company. The Televue Air-Chair sells for $175 and has a pneumatic piston with a lever under the seat similar to typical office chairs,
that allows you to change the seat height without getting off the chair.
These �round-stool� chairs have one major disadvantage in my opinion: they are only adjustable in height from around 20� to around 28� (depending on the model) and that�s not enough of a range for an SCT
as I�ve noted above. In my experience the eyepiece of an SCT moves across a very large height range when you move from
objects overhead to objects near the horizon, and an observing chair needs a much larger height range than these
round stools provide. And note that a SCT scope is relatively compact and thus has a much lesser eyepiece
height variation than refractors or newtonians/ dobsonians. So I recommend you look at the second category of observing chairs:
The classic design for an observing chair is a sliding seat on a folding mount, like the one shown in the middle of
the top photo on this page. In most of these chairs, the seat is held in place by friction - its cantilevered weight
holds it in place and to move it you lift up on the front of the seat to slide it up or down. For most of the chairs of
this style, the cantilever/friction system doesn�t work very well. It is easy to kick the bottom front of the seat with
the back of your foot (which is easier to do in the dark than you might think, when you are maneuvering yourself out
of the chair and your legs from between a tripod leg, the chair, and an observing table). Also, in many of the chairs
of this style the seat can slide down if you put your posterior too far back in the seat. Many of the members of the Yahoo SCT-User Discussion Group have noted that the popular metal StarBound
Viewing Chair, sold by many of the major astronomy mail-order vendors, suffers from these problems.
Many of the members of the Yahoo SCT-User Discussion Group have also noted that the metal
observing chair (shown here on the right) sold by BuyAstroStuff for $95, does not suffer from the
accidentally-kick-the-seat-and-have-it-crash-down problem and they have been happy with this chair. I purchased one and I�m also very happy with it.
Another good but more expensive product ($170) is the StarDust
Chair sold by Hands on Optics (shown here on the left). The movable seat is held on place by positively hooking onto the cross
-bars rather than by friction, so the seat cannot slip down if you accidentally lift the front of the seat. The seat is mounted on rubber bushings so it is able to tilt a little - you can lean forward or to the
side and still have the comfort of your posterior contacting the whole seat. Also, it has a folding footrest for those times when you�re
sitting high up in the chair (i.e. observing objects near the horizon). I�ve used this chair and it solves the problems with most of the sliding-seat chairs including the one I
built for myself. It does have one disadvantage over other sliding-seat designs, in that moving it up or down requires both hands to unhook it and hook it in a new position,
so you must get out of the seat to raise or lower it. I�ve found that the BuyAstroStuff chair discussed above, is easier to use.
Wood observing chairs available and if you have some woodworking skills you can build your own chair from wood and plywood; click here for plans for various observer�s seats in the classic sliding seat design that you can build
for yourself. However, I�m a good woodworker and I made myself a wood observing chair. The seat suffered from
the unintentional sliding problems discussed above. I retired it and now use the StarDust chair. I don�t think wood
is the right material for an observing chair - the seat needs to lock in place and that is best done with metal, in my experience.
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