Encoders can have some benefit with wind gusts but will not eliminate movement entirely. That's because they act after the fact and cannot predict when a gust comes along or how big it will be. They do stiffen up the system and bring the axis back quickly from a disturbance, but not in zero time, instantly. Even a direct drive mount with encoder control will not fully counter a sudden wind impact on a scope. I have a 17" astrograph on our 1600 encoder mount and find almost no effect during gusty windy conditions simply because the tube assembly is an open carbon fiber strut design and the wind simply blows right thru. This is also the scope construction that I have seen at all major observatories that have a number of small patrol telescopes set up (small meaning between 16" and 24"). They even remove the shroud that surrounds the mirror.
Having dual axis encoders does enhance guiding over our non-encoder 1600 mount. The axes respond in milliseconds and very accurately to the smallest move command. This is especially true of the Dec axis where reversals take no appreciable time with encoders. The need for PEM correction is gone, and it is quite nice to be able to take long guide exposures of 20 seconds without having errors due to PE during that time. Periodic error just goes away forever and Dec backlash is gone also, no matter how the worms wear. This is one reason (among many others) the encoder mounts are preferred in remote setups.
[ap-gto] < ap-gto@...
To: ap-gto < ap-gto@...
Sent: Thu, Jun 20, 2019 1:47 pm
Subject: [ap-gto] encoders for 1600 is it worth it
There is a 100$ discount on encoders for the 1600 mount presently at AP.
I have a 12" f/4 newton on this mount. The tube is carbon sandwich and spider and cell are both of good quality, yet there is still some minor mirror movement. I guide well on the system with QSI660 wsg-lodestar. Do you think I would get any improvement from the encoders (I mainly think wind gusts)? I doubt that I will get unguided 5 min subs due to the mirror system with its inherent flex and movement of the mirror?
After all it is a substantial investment