One of the things that bugs me the most is changing eyepieces. When looking at something having to fiddle around with the eyepiece, take it out of the case, decap it, etc....can be very annoying. Of course you loose the caps in the dark!
It need not be such a problem. I have all my eyepieces in a case, I take the caps off once a night, replace them once a night. The rest of the time I keep them in the case and it takes only a moment to remove the eyepiece from the scope, open the lid, put the eyepiece back and then choose another eyepiece, place it in the focuser and focus. I will generally swap eyepieces several times per object.
For some of my scopes I have a large Rubbermaid plastic container mounted on the tripod spreader for the eyepieces. If the dewing is substantial, then I just keep the cover on the container.
I suspect that one issue for you is that your eyepieces are not "parafocal" so it can take you a fair amount of time and effort with an SCT to reach focus. Rack and Pinion and Crayford type focusers allow one to reach focus much more quickly.
As far as what one is giving up with a Zoom. Good simple 4 element eyepieces like your Orthoscopics are difficult to beat in a slower scope. Vlad suggests that a premium Zoom will "always" beat a "medium" quality eyepiece.. I am not so sure about that one. Always is a big word... My experience suggests otherwise but of course it mostly a question of semantics.
So what are you trading away? as John said, field of view. An 8 inch F/10 SCT even at it's best has a limited True Field of View and a Zoom eyepiece will limit it even more. From Andreas's numbers, I calculate that you would be limited to a TFoV of just about 0.5 degrees, about the size of the moon and less than half of the TFoV possible. At the minimum, I would suggest adding an eyepiece like a 32mm Plossl with a full sized field stop, this will provide a 0.8 degree TFoV. A full sized Focal reducer can provide noticeably more.
And too, for many of us, we have been seduced by the pristine wide fields that single focal length eyepieces can provide, those 68 and 82 degree AFoVs can be addictive. You are giving those up with a zoom.
(Myself, I love the big widefield/richfield views, wandering around the Milky Way with a 2 degree TFoV in an 8 inch is quite the wonderful experience..)
All that said, I have a Vixen LV Zoom, it is the same Japanese made 24mm-8mm Zoom that has been sold by many vendors, Celestron, Meade, TeleVue to name a few. For many years it was the standard "premium zoom." It starts out with a 38 degree effective AFoV at 24mm and at 8mm provides something around 58 degrees as measured by drift timing (and of course assuming my memory is correct.) These generally sell new for between $150 and $200. Used, they can be found for around $100:
http://www.astromart.com/classifieds/details.asp?classified_id=644646
I primarily use it with my PST ({Personal Solar Scope) but occasionally use it with one of slower focal ratio Newtonians or refractors. It does a reasonable job but for the most challenging high power views, when I want the best I can get for a given scope, I will most always choose a fixed focal length eyepiece.
I am one who believes you can never have too many eyepieces, adding one decent quality zoom to your collection is a reasonable thing to do. There are some very inexpensive zooms, Celestron makes a 24mm-8mm that is around $50, I would suggest avoiding the inexpensive zooms. I have heard good things about the Hyperion Zooms but they tend to be relatively expensive and rare on the used marketplace. Depending on your budget, one of the Hyperions or one of the Japanese made 8mm-24mm Zooms would be a good choice IMHO.
Jon
