Hey all,
For the last few years, whenever I have tried performing V-curves in FocusMax, I have always ended up with skewed curves which resemble hockey sticks.
This is with a relatively heavy setup (but, probably quite modest considering what today's payloads are like) of a RoboFocus focusing an FSQ-106N (4" focuser), CAA, SBIG STL-FW8 and SBIG STL-11000M.
I had figured that it was likely better for the focuser to work against gravity and push the camera/filterwheel inwards, rather than let the pull of gravity influence the V-curve run.
It used to annoy me as I could never find anywhere on the web where other people were having these same issues, but, I didn't concern myself too much with it as I was getting perfect focus (FWHM often around 1.5 (or lower) for luminance).
I had reason to pull apart my gear the other day to install an AO-L (which was a waste of time as I've run out of inwards focus travel -- need to mortgage the house and have PreciseParts make a thinner adapter between the CAA and AO-L, replacing the chunky Feldstein #6 adapter (CAA to FW8/STL) I've been using for the last few years).
Anyway, once I'd removed the AO-L and installed the camera and filterwheel again, I thought I might redo my V-curves. However, this time, set the final move direction to outwards, rather than what I'd been using previously.
Miraculously, I had /perfect/ V-curves with the apex of the V splitting the X-axis precisely!
I am still facing an issue (which I've had since I installed the RoboFocus) where my centre focus position keeps shifting. For instance, after the first V-curve's autofocus run, my focus was at 4040 counts. On the next run, that shifted down to 4037. This progressively moves downwards. I wish I knew the cause of this problem so that I could reliably use filter offsets instead of wasting 10-20 minutes every hour performing refocus routines. The Baader Planetarium 2" filters I use are meant to be parfocal, but, at f/5, I believe there are some slight differences between each filter. Probably not enough to really worry about, but, I'm a stickler for this kind of thing.
Could this issue have anything to do with backlash settings? They're currently set to the default of 20 in the RoboFocus software. Do I set that to 0 and then change the backlash settings within FocusMax itself?
Anyway, thought I'd share this as it brought a massive smile to my face seeing the V-curve perfectly split the X-axes for the first time in over 4 years!
If anyone has suggestions as to my other issue, I'm all ears!
H