Hi, Vi,
I guess it all depends on how portable you want your 'scope to be.
A Six inch Dobsonian would be an excellent option, if it is light and small enough. However, get a 5 inch if you must.
Also, aside from considering the expensive "5 inch refractor" option, you should seriously consider a 5 inch or 6 inch Schmidt-Cassegrain, before you make your buying decision.
As per the table of relative LGP, you can see that there is a very big jump in deep sky performance between 3 and 4 inches, and another substantial (but somewhat smaller) jump in LGP between 4 and 5 inches. A 5 inch in a good sky gives you decent, though not super-bright, views of most deep sky objects,
with the exception of galaxies
(unfortunately, galaxies need all the aperture you can throw at them, and more!!)
You would certainly want to use a 5 inch with good quality eyepieces, to somewhat mitigate the effects of the relatively small aperture!
I used to own a 5 inch Schmidt-Cassegrain (it was a Celestron C5), which is a
very portable and
very compact and
very light-weight Optical Tube Assembly, but the mounting requirements are still a problem, even for a 5 inch telescope; because a decent and stable and precisely-moving mount always adds substantial weight.
I currently use a Synta (Sky-Watcher) AZ-4 mount with my 4 inch F6 apochromatic refractor, the version of the mount that has broad metal tripod legs (the wooden-tripod version of this mount is less stable). This is a well-made (it is stable)(it has precise motions up to 150-200 power) altazimuth mount and tripod that can be adapted for compact telescopes of up to 5-6 inches of aperture. (These mounts come in at about $300-450 depending on where you buy them)
This mount and tripod are easy enough to lift and move around, and a lightweight tube assembly would maintain this portability. However, even the AZ-4 mount does not quite meet the requirements of "grab and go".
Here is a picture of the AZ-4, in the version with the thick tubular metal tripod legs :
This mount uses the Vixen dovetail, making it easily adaptable to many different small telescopes. Careful! as there is another "AZ-4" on the market which is a different mount entirely.
The metal tripod is quite beefy, and the rigidity is good, though this rigidity also adds extra weight.
The altazimuth mounting itself was designed without a counterweight, so it is not suitable for heavy instruments:
NOTE ADDED in EDIT:
There are many different ways to mount a 5 or 6 inch Schmidt-Cassegrain Optical Tube Assembly. The above is just one possibility.
I seem to recall that Satchmo (Mark) had a 5 inch Apochromatic refractor on this AZ4 mount, and the setup worked very well, though his 5 inch refractor had a shortish tube. As Satchmo remarked in this thread, you can spend an
awful lot of money on a
small telescope, if you go for the "apo" refractor option!! (But apos are pretty cool, anyway)
Best regards,
from Bad Galaxy Man