SCP Am I right???

[peter brown]

Thanks to all for advice over setting up my pier. 2 nights ago I tooh a star trail photo and have gestimated that here in Victoria, the Magnetic pole is 12 degrees west of the SCP. Got to get it right before I concrete bolts for my Local Group pier, as it doesn't allow any rotational movement, and the azimuth leeway on the ultrawedge (for LX200GPS 10") doesn't appear to allow for much error in initial SCP alignment.
Would post the photo but I don't know how.
Many thanks again


Peter B

[xelasnave]

Sounds fair so far... true South is not magnetic South.

A photo will convince you of placement.

To post a photo go into "manage attachments" , put in the file, upload, close when complete.

good luck
alex

[Hagar (Doug)]

Hi Peter, Here is the Government guff on magnetic variation.
http://www.ga.gov.au/oracle/geomag/agrfform.jsp

[leon]

Thanks Doug according to the calculations for ballarat I am 10.9 degrees East of magnetic south.

Leon

[peter brown]

Thaks Doug, I get magnetic south is 12.054 to my West therefore I will have to draw my alignment line east of my compass bearing
Thanks again, but I'll still take one more star circles photo to confirm it....before the concrete sets!!!
Cheers
Peter B

[JimmyH155]

HEY, use the method someone mentioned here a few weeks ago, ie use a plumb bob and find out when local noon is (there was a link to a site) Then at the exact time of local noon, the shadow of the string on the plumb bob will point exactly North - South. I tried this and laid a stick along the shadow at the appointed time. Then I hammered into the ground at each end of the stick, a peg and hey presto my north-south line. I checked it out with my compass, and the compass read spot on what it should have done bearing in mind the magnetic variation for Brissie.
You could use this aas a check before pouring the concrete Surely you will have some adjustment won't you? enlarged or slotted bolt holes perhaps?

[peter brown]

Thanks Jimmy,
I remember that article but I can't remember how to determine actual midday. Probably has a relationship with my local sidereal time which I should be able to work out using the formula in the Astronomy 2008 Annual. Thanks again
Peter B

[AndrewJ]

Gday Peter

Just set the scope up Alt Az
Do a std two star align and a few gotos to assure you have it right
Then just "goto" the Sth Pole.
Turn off the scope
Loosen the dec clutch and slew it down till its horizontal
The OTA is now on an exact True N/S axis

Andrew

[astroturf (Bryan)]

G'day Peter & all
I think I'm only a couple of moves in front of you

I downloaded this : http://www.spot-on-sundials.com/calculator.html & set up a plumb bob suspended off a 10 foot ladder and laid a long straight piece of timber on it's shadow as Jimmy did at Solar noon(11.52 am for me)
I then transfered the line to a mark on each opposing wall where upon I use a cheap laser to line up the tripod
,I now get the scp every time I set up

Good luck with it all
Bryan

[astroron (Ron)]

My only comment is that you should build in some form of adjustment, as suggested enlarged bolt holes, that is if you want to be super accurate.
Ron

[acropolite (Phil)]

If you want to check and be sure use a vertical stick to cast a shadow at Solar Noon.