putting in my pier having trouble working out true south.

[icytailmark]

hi guys im in the process of setting up a perm pier. I have dug 1mx1m and 800 deep hole. I am gunna fill it in with concrete to make a pad and put my pier in concrete. My question is to work out true south do i need to point the telescope head toward 12.5 degree east of south like i normally do? I have heard you can also use solar noon line method. Which is the most accurate?

[mithrandir]

Solar noon is the simplest. Any magnetic material within several metres of the pier location will throw a compass out. There should be enough adjustment in the mount head that you only need to get the mounting plate on the pier within a couple of degrees of true south. http://www.esrl.noaa.gov/gmd/grad/solcalc/ will let you work out the time of solar noon. Today in Castle Hill it is at 12:42 AEDT.

Or http://www.spot-on-sundials.co.uk/calculator.html to generate a spreadsheet for the whole year.

[icytailmark]

thanks andrew

[icytailmark]

andrew do you know a good website that explains step by step how to point the pier directly true south? Do i need to have the EQ head on when doing the measurement? Im setting everything up before i start pouring the concrete and i wanna get it all right.

[mithrandir]

I don't Mark. Someone else might chirp up. Putting the head on would let you mark on the pier where the north/south line should go. You could then take the head off, put the pier in place and match up the marks with your N/S line, set some pier braces, pour the concrete and let it harden.

[bojan]

Calculate the time of your local noon for your location
http://en.wikipedia.org/wiki/Noon
http://education.illinois.edu/noon-project/noontime.html

Then, use a piece of string, with something heavy dangling on the on the end.. Place it (at noon) such that you can clearly see the string shadow over the place where your slab will be (or already is).. mark that direction/line clearly.. and that's about it.

[icytailmark]

where do i hold a piece of string? Across the top of the pier? Across the center of the pier? What do i use as a reference point? If i hold up a piece of string so the shadow casts across the top of the pier it can be anywhere across it.

[mithrandir]

What bojan means is to use a weight on a string to throw a shadow to get your n/s line at solar noon. Thick string works best (easiest to see the shadow), but don't try it on a windy day. Then position the pier so that your n/s line aligns with the polar axis of the head.

[icytailmark]

so it has nothing to do with the screw notches on the actual pier its the CWD axis where u tighten it on the mount head u gotta align to true south?

[mithrandir]

What you need to align depends on the pier design. Got some pictures?

All you are trying to do is get the polar axis pointed at the SCP. That requires setting the azimuth so the RA axis is n/s. Setting the altitude to the latitude is a separate step and has to wait until you have the pier fixed in place. Start by having the pier top plate close to level.

The phrase acronym "CWD" usually applies to a Losmandy mount and refers to a known starting RA position to calibrate a Gemini controller. It doesn't relate to the polar alignment, and does not necessarily have the counterweight shaft hanging precisely down.

[icytailmark]

some pics of what ive done so far

i had the pier top cut to fit a losmandy g11 mount head.


http://postimage.org/image/9no4ukzu1


http://postimage.org/image/66tfjagaf/

[mithrandir]

One of the notches should be aligned to be south. Not the opening at the top. Where the lock screw will be after you turn the head to lock it to the pier.
124531

[icytailmark]

well ive got my pier all aligned to south. Tommorow i pour the concrete. Im very excited!!!!

[icytailmark]

all done. It worked out to be 0.4m of concrete.It only took 20 mins to do. I hired a truck and just wheeled it out the back.I just hope its enough concrete for my C14 scope.