Well my big question is what can you do?
Trying to correct my tracking I removed my Canon 400D - which I haven't had to re-focus on my C9.25 CF for 6 months and in its place put a 3" extender and a 12mm illuminated reticle.
I re-set focus by hand and got to experience just how much flop was in the focuser. Once the star approached focus - if I minorly reversed focus on the SCTs main focus knob - well the star jumped about 15 percent of the way across the field of view! Is this normal - or indicative the focuser is too loose?
I had forgotten how much moving the main focuser cause the centre of the star to shift. Ideally you'd want no shift - here the shift is so great as to make focusing near impossible. I remembered that's why I bought a Meade motor focuser and did fine tuning off this - this made it easy.
By way of example:
http://www.astronomiainumbria.org/ad...sh/lx_flop.htm
So three questions:
1. For a well tuned focuser on a moderate SCT - how much should you expect to see a star jump acorss the field of view when you change direction of focus as gently as you can?
2. For the jump I see - is this indicating mirror flop or focuser travel?
3. What can I readily do to improve things (or is this only shop tuneable if at all)?
I am now staring to wonder if my tracking problems (star appearing to gain in RA 1 arc minute and hour is either play in the imaging training (that reduces with the sine of the elevation) or mirror flop!
I also remember one experience imager saying the wound the mirror all the way back to stop mirror play / flop and used an external focuser with I presume alot of play to bring stars into focus! Someone else drilled holes in the back of the OTA, threaded them and inserted plastic screws until they hit the primary to lock it into position permanently!
Hope I am not headed for that path!