I'm considering changing the 1.25" focuser on a Newtonian for a 2" one. It is a commercially made small reflector, but what would the image problems be for changing to the 2" format?
I'm aware that using a larger secondary reduces contrast, but what would be the consequences of using smaller secondary be at the eyepiece, assuming that the secondary is at the optimal light cone position and the EP achieves focus?
I just recently finished swapping my 1.25" (cheap) rack & pinion for a nice 2" Crayford focuser ($150 US) on my 130mm f/5 Newtonian. All I did was to drill 4 1/4" carefully placed holes in my steel tube and fastened the new focuser with the help of some washers to shim the new focuser properly. You should not have to move the primary or get a larger secondary if you get a low profile focuser. My new Crayford is made by Antares and has a nice 2" extension tube built into the focuser. I did not even have to cut a larger hole in my tube to allow the focuser to extend a bit into the tube. The fully racked in distance, from the tube to the eyepiece hole, was actually a bit less than the old focuser without opening the hole for the 2" focuser tube. The Antares, as most 2" focusers do, came with a flush mounted 1.25" adapter which aided in the low profile. I installed the 2" focuser because I wanted to do some photographic work and the 1.25" rig was too flimsy and typically had backlash and side shift issues. The Antares has a second stage 10:1 fine focus knob which is very nice for critical high power work. All my EPs are 1.25", but I just purchased a very nice GSO 2" 2X & 1.5X Barlow and an Orion 2" moon filter all for less than $100 US.
Ta, Gary, . I was starting to think along the same lines too. I had a bit of a look at the height of the focuser, and with the focuser I have I'll just need to make a little jig to raise the focuser to the optimal height.
No stuffing around with wider openings, etc. Just a staight swap really, though a little fiddly
Mental, I have a small 6" diam. telescope tube so there were no adapter plates available for my focuser. If your 2" focuser is flush mounted, there are radiused adapter plates available for 8" tubes on up. You usually don't find a 2" focusers on reflectors below 8". Good luck on the project!
. I was starting to think along the same lines too. I had a bit of a look at the height of the focuser, and with the focuser I have I'll just need to make a little jig to raise the focuser to the optimal height.
