Looking for advice on "draw tube length". I've searched around however didn't really find anything definitive. I have a older 12.5" Portaball with the aluminum ball and it has a decent older JMI focuser that I am thinking about upgrading because I would really like a dual speed focuser. When I use my Nagler 31mm it does not reach focus - there is not enough in-travel. So I am considering the Starlight Instruments Feather Touch lightweight focuser as it has a lower profile than my current focuser and as I understand it that should allow my 31mm to achieve focus (if I'm incorrect please educate me). The FT has options for 1.5", 2.0" and 2.5" draw tube lengths so I need to understand how to figure out which one is best for me.
I don't use binos however I do have several Naglers from 31mm to 3.5mm and I also have a couple of Powermates in 2" and 1.25". I will be doing visual observing only of planets, the moon, and deep sky objects.