toryglen-boy
20-07-2009, 09:43 AM
I recently went to buy an 8" OTA from one of our esteemed forum members, due to a bill i got from my lawyers (dont ask) i had to put the sale on hold. My good lady seen how fed up i was over this, and bought me a shiny new OTA a surprise! she is a wee diamond, although i am posting this, as i now have an issue ...
I am pretty sure its balance, but i thought i would share here for some professional insight. If i try to guide, with something that has just risen in the west, the guiding slips. I can see the guide stars move on PHD, as if i am looking through high magnification, and the tracking has been turned off.
As the object aproaches the zenith, the guiding gets better, and it seems to hold its own.
If the object has passed over the zenith, and the weights are higher than the OTA, then it can guide all night for hours and hours, although if it does a meridian flip, the guiding starts slipping again, as the weights are below the OTA. The strange thing is, if i alter the weight, by moving one of the two counterweights up the shaft, it still behaves in the same way, i even remove one of the weights, to make the scope end obviously heavy, and unbalanced, it still happens, but yet, when the weighted end is level with the OTA, or higher than the OTA, it doesnt, i know its balance but it seems a bit odd .... and when i put the ED80 on there it has no issues whatsoever, it can guide, flip, everything without slipping.
Any ideas? i have tried to balance it on both axis, and it seems fine ... and there cant be anything wrong mechanically, the ED80 runs all night on it.
bahhhhh !!
I am pretty sure its balance, but i thought i would share here for some professional insight. If i try to guide, with something that has just risen in the west, the guiding slips. I can see the guide stars move on PHD, as if i am looking through high magnification, and the tracking has been turned off.
As the object aproaches the zenith, the guiding gets better, and it seems to hold its own.
If the object has passed over the zenith, and the weights are higher than the OTA, then it can guide all night for hours and hours, although if it does a meridian flip, the guiding starts slipping again, as the weights are below the OTA. The strange thing is, if i alter the weight, by moving one of the two counterweights up the shaft, it still behaves in the same way, i even remove one of the weights, to make the scope end obviously heavy, and unbalanced, it still happens, but yet, when the weighted end is level with the OTA, or higher than the OTA, it doesnt, i know its balance but it seems a bit odd .... and when i put the ED80 on there it has no issues whatsoever, it can guide, flip, everything without slipping.
Any ideas? i have tried to balance it on both axis, and it seems fine ... and there cant be anything wrong mechanically, the ED80 runs all night on it.
bahhhhh !!