Quote:
Originally Posted by rmuhlack
if you are setting up and packing up each time, is it even possible to achieve an accuracy better than 1-2 arcmins (even with markers on the ground) ??
A reality check from my back-of-the-envelope calcs - to achieve an alignment error of ~2arcmins, the tolerance for placement of my EQ6 tripod on the ground is about 0.22mm with the legs fully retracted. Based on that I'd have my doubts about whether I could repeatably eyeball the mount placement any more accurately than that, even with markers on the ground.  |
I am with you Richard, I think it is near impossible to get complete accuracy by lining up tripod legs to marks in the ground by sight. I have given this problem some thought, as I am in the same situation. The solution I am going to try, although not perfect, is to line up, as accurately as I can, the SCP by drift method, mark where the legs are and then I am going to drill holes in the concrete to take a large (3") bolt, that will sit flush with the concrete and that will be chemically achored. The head of the bolt will have a steep cone recess machined into it (similar to a "centre drill" cone), in order to positively situate the point of the tripod legs each time in the same position. Once that is done, I will situate each leg in these cones and once again drift align using the fine azimuth adjustments. In this way, I should, hopefully, be able to set it up fairly accurately each time. Because of possible vibration problems with this idea, I may substitute bolts with rubber or a rubber/bolt combination, but I have to give this some more thought.
Although I have a permanent set-up in my dome, I need this so that I can quickly set up my refractor next to my dome, without the need to set up a permanent pier, which would be ideal, but in fact would be in the way. So, the above is the only solution I can think of, which isn't too bad an idea, as I can have the same arrangement out the front of my house as well, for those objects I just cant see from my back yard. Also, if this works, I may possibly be able to have the same arrangement at my dark sky site.
Cheers Peter