Looking at deep sky in city skies is like driving a 900hp car at 30mph. I am sure a 25" or 30" F/5 or 6 would be great for the planets. But i am gonna need a much bigger house. A 18" is as much as i want to handle and even have trouble getting it out the door that it just sits most of the time well until prime time for planets in about 2 months.
I want a scope i can roll out all setup easy and a longer FL like F/6 not F/4.5. A 16" f/5.5 would be my choice for my door.
Live in a big city? Want a 30-inch? John Dobson taught us the way!! Get an old school bus almost ready for the dump - remove 2/3 of the seats to open up the back - install a ramp in the tail to get the scope in/out -- head with your friends to the high country national parks in 'observing season', use your 6" in the city during the winter to look at Saturn and maybe M-42. If you get caught in a high-country snow storm -- pull over and sleep inside the telescope tube!
For a planetary observer - I agree that it would be hard to believe that anything bigger than a 20" in the F/5 to F/6 range is needed - and even that is pushing it.
We've had some very experienced observers tell us in this thread - yes, under good sky, a 30" will show more than a 25" - especially if your goal is to "push" beyond what you have seen before. Is the better view of 'show objects' like the Messier list improved in a 30? Probably a little - but I always wonder when seeing a 30+ incher pointed at something like M-27 -- unless of course at a star party and the owner has a long line of APO/SCT owners waiting to be impressed!
Can using "NV" catch up? It will certainly show a lot more in the 25 if that's 'your thing' -- but it will show even more in a 30. I've looked thru Al Nagler's electronic gizmo on a 36" -- very impressive -- so impressive that Al was practically dancing around in joy! It also was 'impressive' on a 90mm APO 20 feet away - but nothing like the 36.
So -- a potential 30" owner is back to the old questions -- can I get it under good sky (darkness and seeing)? can I transport it if need be? storage? can I climb up to the high eyepiece all night, 4 nights in a row and still take it apart to go home? - am I healthy enough to use such a beast? maybe the biggest -- do I have the $$$???? Very few will answer 'yes' to all those questions -- and they are the lucky few who should have a 30-inch...... that the rest of us can maybe look thru at the next star party.
Personal note - of limited value to readers here - my NI (natural intelligence system) went thru this exercise a while back and concluded - I could handle, live with, and afford a 22" to 25" sub-F/4 Dob of the 'modern design' made by one of the top say 5 or 6 pro makers -- but -- how much longer will my health hold out? My final decision was to stick with the old familiar 20-inch Dob size - re-imagined as a F/3.5 and in the 100 lb weight range. So -- now I have extra $$ to spend on more imaging gear!! Tak e-150 on a G-11 mount??? What works for me certainly will not work for you!
Anyone with a 30-inch -- message me your phone # and when I can come over!
Edited by George N, 25 July 2021 - 10:39 AM.