Well I've decided to build a pier in my backyard. However I won't be able to leave the eq mount out there all the time so I want to have a top plate for my pier which allows me to remove the eq mount head, and re-attach it without losing eq alignment (as much as possible anyways). I'm doing all this as my time that I can dedicate to this hobby is very limited, so when I have a good night I want to be able to setup quickly. (Or just for a quick visual obs).
So I've come up with the design below. This system incorporates the usual two plate system to level the top of the pier, but then has a third plate which screws down on 1.5 inch (or bigger if needed) stainless steel balls which are recessed into both the top plates (sit in 3/4" holes). The top plate would stay permanently attached to the eq mount head and would come away with it when detached from the pier.
The balls would act to automatically centre the top plate into the same position it was in last time it was installed (as long as the top knob bolts are screwed down relatively evenly).
So call me crazy if you think its all a bit silly, but do you think it will work?
This drawing is not to scale, its just to give an idea of what I'm on about.
Dave, the balls idea looks pretty good to me, as long as the holes they mate to are nicely smooth and even.
What I don't understand (and maybe it's for another thread), is that people go to a lot of trouble to make a big solid rigid pier, then sit the mount on a plate supported by four (relatively) little bolts. Surely those little bolts would allow a lot more flex and/or resonation than the rest of the pier?
The pier will be concrete, with 3 threaded bolts (M12).
The top plate (for EQ6) will be mounted on those bolts, and fixed in place with top and bottom set of nuts (so there will be some adjustment available).
The mount should always be in the same position, provided the adjustment screws are not touched (one of azimuth screws will have to be fixed in place by means of counter-nut).
Yes I agree, some top plates do seem compromised by tiny bolts. Thats why I would use four rather large 15mm bolts for the middle plate. The top plate is then held by contact to 3 large balls plus 3 medium sized bolts. Also I will strive to keep the distances between plates minimal.
My understanding is that the bolts are less of an issue when close to the mount. If the levelling was done at the bottom of the pier for instance they would be more prone to flex.
I thought that as long as the mount is near enough to being level, the head's built-in adjustments allow correct alignment. That's what it says here in 'Basics of Drift Alignment' anyway:
No need for them really.
Unless mount itself does not have them (and EQ6 does..).
Quote:
Originally Posted by koputai
But why the adjustment bolts at all?
I thought that as long as the mount is near enough to being level, the head's built-in adjustments allow correct alignment. That's what it says here in 'Basics of Drift Alignment' anyway:
True, as far as I can tell, the only reason you need to have a level plate is to make drift alignment easier. As its good to build some adjustment into your pier incase the pier shifts/settles over time.
Also we are both talking about "flex" in short lengths of thick bolts. I'm sure someone smarter than me could work out exactly how much flex these bolts add. I'm sure its insignificant, it seems to work for a lot of people.
Flex is not an issue (IMO) as the mount is balanced (by definition..) and it is constant (in case there is unbalance present in NS direction).
More important is possible oscillation of the whole .. and the rigidity axial to the bolts will be quite sufficient.
So I wouldn't worry (and I don't, since I am buildint it myself like this - I have even smaller screws, and 3 only)
It is very easy: (I did it couple of times with tripod - my pier is still under construction)
First you have to un-fasten one of the screws used for azimuth (another one should be fixed by counter-nut)
Then, the central screw at the bottom and the mount can be removed.. and placed back in the same position, provided the elevation and that azimuth knob (secured with counter-nut) is not moved.
It is very easy: (I did it couple of times with tripod - my pier is still under construction)
First you have to un-fasten one of the screws used for azimuth (another one should be fixed by counter-nut)
Then, the central screw at the bottom and the mount can be removed.. and placed back in the same position, provided the elevation and that azimuth knob (secured with counter-nut) is not moved.
That sounds like a good process assuming there isn't too much play in where the mount itself mounts into the tripod/pier.
I think I should just give this method a go before playing with elaborate setups Cheers!
I would have a look into surveying equipment, they utilize a quick switching mechanism so that you can move from one tripod to another without having to move the tripods. it is quick simple and locks things down securely!
Dave, you don't need any double heads. Just a top plate that is level and has a locating pin. Back off the azimuth knobs a quarter turn each and the head will come off. Here's the top of the one I ended up with. Bit of an over kill but I only realign after dragging the head out west and back. I have marked the top plate and the head as to where azimuth should be
Cheers!
