- Triple Piggy Back Works!
Re: Triple Piggy Back Works!
toggle quoted messageShow quoted text
A +1 what Roland said about balance in all directions/axes. In the 11" F7.2 Newtonian on the 1200, I have 85 pounds worth of weights. I very carefully balanced the tube in RA but also paid particular attention to the DEC. You can't see it because it's on the other side, out of view, but I added an aft ring with a weight counterpoise to the focuser/bino-viewer/finder assembly to counteract their combined off axis torque. Works well. I also decrease the slew speeds to 600x (if I could, I'd probably go down to 500X or maybe even 400x).
To make something like this work, be sure to balance both axes very accurately. Once in balance, the torque required by the drive motors is no higher than a completely un-loaded mount. What happens when you have some imbalance, especially in the Dec axis, is that the pressure on the worm teeth increases dramatically. This causes high friction that impedes precise motion of the Dec axis at sub-arc sec levels. You may get increased delay when the axis is commanded to reverse during guiding and possible overshoot if the friction is really high.
With good balance the encoders will command the Dec axis to move almost instantly for same or reversing directions. With out of balance, the encoders will try to compensate but if the friction is too high you will get jerky motions at sub-arc sec levels.
From: Peter Bresler via groups.io
Sent: Thu, Dec 24, 2020 11:01 am
Subject: Re: [ap-gto] Triple Piggy Back Works!
[Edited Message Follows]
In spite of the inertia the guiding with the OAG appeared to be good. The mount is balanced as is. I cannot add an extension bar because the shed doors would not close. There are some processing issues with that image that I still am working on. I have been working on organizing the wires and lengthening them. Cable snags are infrequent now. I probably will remove the small scope when not in use. It still is easier than switching them around. The mount is a 1200.
Join firstname.lastname@example.org to automatically receive all group messages.