Jim,
Yes if
you are able to handle the physical size of the scope when ... in Storage,
Transportation, Setup and breakdown, it is worth building a large aperature
scope. In the 22" size, you will need to built a dobsonian, or build a
HUGE mount. I have a large mount coming which would be able to support a
scope of that size, but the mount is so heavy that it has to be on a permanent
pier, and it's scope will be left at home unless I build a custom trailer for
the mount and pier. (It's 175 lbs for the mount alone, not counting the
counterweights drives or electronics. The entire setup will probably end
up being 500-700 lbs total. Too heavy to be portable)
When
building a 22" scope, you are gaining additional resolution and light
grasp. But remember that the long 11' focal length will limit how wide a
field of view you can see. Even with a 32mm super wide field eyepiece, you
will have 103 power and somewhere around 1/2 of a degree true field of
view. If you are wanting to do deep sky viewing, you may want to go with a
shorter focal ratio. Properly figured, a 22" F4 scope will have minimal
off axis aberations, will be able to handle high powers easily, but will still
give you a wider field of view when hunding DSO's. The additional benefit
is that the scope assembly will be much easier to design and construct than the
F6. Remember that the physical size of a 22" F6 scope will pretty much
dictate that you have a dedicated trailer to transport it, or have a large van
or truck just for the scope, and will not have much room left for camping gear
or the rest of the family. While a F4 will be small enough that you might
be able to fit it behind the back seat of a suburban and still bring the family
along and have some space in the back for camping gear. That extra 4' of
focal length realy does have an impact on transportation.
Just
food for thought.
John Zeigler
John
thanks
for the reply. I have been toying with the idea of building a 22" f 6. That
would make the focal length 11 feet long. I wonder if it's worth it
having to climb a 10' latter.
I made
a 12.5" f 7. It should be about a foot shorter than yours. I am kind of
wishing that I had made my f 8 now. Oh well.
Jim