Hey Guys,
some time ago I was quite astonished to hear that there are tak toa users that support their focusers with rubber bands to get rid of slippage.
First time hearing that people support their premium scopes with rubber bands I thought, that can’t be real.
my esprit 120 always had very slight slippage I guess. i recalibrated my focuser maybe once a year, because it lost a few thousand focus positions points within that time. the slippage or whatever it was, was really slow, and my data and focus consistency was great.
that changed yesterday night.
imaging sh-240 with the scope in Zenit my Sesto senso 2 just could not hold the weight of the imaging train anymore.
i lost around 500 focus points with every autofocus run (head to head runs), which led Nina to give me the “hfr is worse after autofocus blabla error message” every time.
imaging was impossible at this point and after spending a whole night and some more hours today I still couldn't resolve the problem.
what I have done and observed until now is the following:
- I upgraded nina
- I upgraded the sesto senso
- I activated the “hold” function of the Sesto senso within the play software
- I did multiple calibration rounds
- checked my Nina settings
- I tightened the esprit 120 fine focus grub screw (it already was very tight, and i am not sure if I have actually turned it because of that)
- I tightened the Sesto senso 2 grub screws that hold on to the fine focussing knob
- I partly engaged the locking screw of the esprit. guess that made a difference. with the locking screw partly engaged the area around my focus point seems to don’t or only very slowly slip. Imaging at around 60 degrees, I only went from an hfr of 2.33 to 2.45 within a hour of imaging
- and yes, it is cold right now, but I have used the exact same setup on nights like this, like a thousand times already
and still… once I point the scope into Zenit, manually moving the focuser to specific positions, there are huge amounts of slippage.
for example, if I manually focus around the 8 mark of the focuser draw tube, the draw tube instantly slips around half a point.
there are a few of this points all over the draw tube.
looking at those specific points where the focuser slips, it is clearly visible that the Sesto senso 2 itself is moving as well. guess that means it isn’t a problem with the Sesto senso not holding tight enough on the focuser knob but more a problem of the Sesto senso 2 being too weak to support the weight of my imaging gear.
well, whats now?
- buying a new electronic focuser?
- changing the draw tube of my esprit to something better like a feather touch?
- using cheap rubber bands on an expensive scope/imaging setup to make it work?
these are my latest autofocus runs in Nina. right now it seems to work but maybe someone more knowledgeable can give me feedback on them.
focus still seems to move inwards a bit but the runs are 45 minutes apart, the scope is well temperated and was outside all day but still, maybe it is just the temperature falling.
i am thankful for any inputs you guys can give me.
thx and clear skies
Anderl
