working out precise polar alignment for permanent pier

icytailmark (Mark) · #1 10-03-2012, 10:32 PM

how do i work out the precise polar alignment for a pier? I dont wanna stuff it up and waste all the money. I have a friend who is making a pier and top plate for my losmandy g11 Eq head. All i will need to do is carry out the Eq head and screw in the 3 bolts. Then put telescope on top each night.

I plan on doing both planet and deep sky photography so i want the tracking to be perfect.

Marke (Mark) · #2 10-03-2012, 10:37 PM

Well I am about to put my adapter plate on and will use the Day time Solar align method . You use a plumb bob of some sort and suspend it over the pier plate when the sun is at exact transit. The shadow points exactly South .

mikerr (Michael) · #3 11-03-2012, 12:50 PM

Mark, Mark, (sounds like a dog with a hair lip)

I used Als Astro Clock to determine Solar Noon to align my pier using the Plumbob method.

http://alsworld.topcities.com/astro/AlsClock.htm

Michael.

scagman (John) · #4 11-03-2012, 02:37 PM

Hi Mark,

here's a easy link to work out your solor noon
http://www.esrl.noaa.gov/gmd/grad/solcalc/

Just click on your location.

mithrandir (Andrew) · #5 11-03-2012, 03:03 PM

Mark,

CdC shows solar transit in its calendar. For you, Ken and me, on the next few days (11/12/13th) it is at 13:06, at 13:05 for the 14/15/16th and at 13:04 for the 17/18/19th.

If you miss that time, you can draw the line and then use a protractor to adjust it by 15deg/hour to give you North/South.

Here a line drawn from where I put the mount to the corner of the garage is within a degree or 2 of South. If SHMBO can be talked into it, and the landscapers are happy to excavate a hole for me (sure beats digging), I might put a pier on that spot.

icytailmark (Mark) · #6 11-03-2012, 03:14 PM

13:05 EDT for Sydney does that sound right for solar noon? Does this calculate true south? 12.5 degrees east of south? I plan on putting my pier thru my pool decking because thats the best spot in my backyard. A 2.5m steel pier and im gunna concrete in around it. I will take some pictures as im going.

mithrandir (Andrew) · #7 11-03-2012, 03:26 PM

Quote:

Originally Posted by icytailmark

13:05 EDT for Sydney does that sound right for solar noon? Does this calculate true south? 12.5 degrees east of south?

Maybe Mark. (Too many Marks in this thread. Almost as bad when all the Andrews chime in.)

At 151E (which runs very close to here and Mark's place) the shadow points true south at 13:06 today. The exact civil clock time depends on your longitude, and don't forget daylight saving.

When you talk about degrees east/west you are talking about the difference between true and magnetic. There is so much steel around my place that I can never trust a magnetic compass, even though I know what the variation according to Geoscience Australia is. If the compass was fixed I could compensate for it but not when hand held.

Poita (Peter) · #8 11-03-2012, 06:07 PM

The solar method works a treat, but make sure you leave a few degrees adjustment in the top-plate, you will never get it dead-on accurate, I was amazed how much I still had to adjust my mount when drift aligning. It was only a few degrees, but you need that adjustment available.

multiweb (Marc) · #9 11-03-2012, 07:02 PM

Quote:

Originally Posted by icytailmark

how do i work out the precise polar alignment for a pier? I dont wanna stuff it up and waste all the money. I have a friend who is making a pier and top plate for my losmandy g11 Eq head. All i will need to do is carry out the Eq head and screw in the 3 bolts. Then put telescope on top each night.

I plan on doing both planet and deep sky photography so i want the tracking to be perfect.

You don't need to be dead-on as the G11 has a fair bit of azimuth range.

Barrykgerdes · #10 12-03-2012, 07:59 AM

I got my true south information from the house allotment plans that give the boundary true bearings. From the pegs, some string (measured length) and trig tables I was able to plot a true north south line through the base of the telescope mount. Maths we learnt in first year at high school. Sorry for you poor chaps who go to schools that think maths is a waste of time.

You can also do this from google earth with a bit of maths and identified points.

Barry

Marke (Mark) · #11 12-03-2012, 08:52 AM

Sounds like a lot of effort Barry when the solar method takes a couple minutes and gives true south.

Barrykgerdes · #12 12-03-2012, 10:36 AM

Quote:

Originally Posted by Marke

Sounds like a lot of effort Barry when the solar method takes a couple minutes and gives true south.

That is no good when the sun don't shine. and you still need to no the exact time the sun crosses the meridian. My way can be done any time and can give arc minute accuracy (arc second if you know your stuff).

Barry

Poita (Peter) · #13 12-03-2012, 12:49 PM

Quote:

Originally Posted by Barrykgerdes

I got my true south information from the house allotment plans that give the boundary true bearings. From the pegs, some string (measured length) and trig tables I was able to plot a true north south line through the base of the telescope mount. Maths we learnt in first year at high school. Sorry for you poor chaps who go to schools that think maths is a waste of time.

You can also do this from google earth with a bit of maths and identified points.

Barry

My pegs aren't even close to those on the allotment plans, and the last google earth pics of my house are nearly 10 years old