Re: encoders for 1600 is it worth it

CHRISTOPHER FORD <cford81@...>

Same for me with my AP1600. Zero periodic error is one less thing to worry about.

However I am also using a 7" refactor so that is a pretty rigid setup. 


On June 20, 2019 at 1:59 PM "Craig Anderson craig@... [ap-gto]" <ap-gto@...> wrote:



I upgraded my AP1600 mount with the encoders last year and love them. Periodic error is essentially gone, backlash is gone, pointing accuracy is up, tracking RMS is down and same in RA and DEC, comet tracking w/ custom rates is great (sans squiggles even when tracking in both RA and DEC). I image with an AP155 f7, which is pretty forgiving, and I  still noticed a what seem to me to be significant improvements with the encoders. If you can afford them, I would get them. Did I mention that installation was easy? 


On Jun 20, 2019, at 4:47 PM, chris1011@... [ap-gto] < ap-gto@...> wrote:

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. 


-----Original Message-----
From:   lacour.morten@...  [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







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