Sunday, 15 August 2010

How to find the South Celestial Pole (SCP)

How to find the South Celestial Pole (SCP) almost accurately.

It is always difficult to find the (almost) exact spot when you are aligning your telescope. I hope this will help!

Why find the SCP?
- To set up your Barn door mount (Scotch Mount, Star Tracker) to ensure round stars on your image.
- To do a proper polar alignment with your Go To Telescope on a wedge to take astro photographs.
- To store it in your head and show your knowledge at a star party.
Why this method?
- You get pretty close to the SCP without guessing where the lines from wherever should cross.
- With a green laser mounted on binoculars (on a tripod) you should get very close to that magical unmarked spot in the Southern hemisphere. Not even the North star is precisely on the dot.

Whose idea?
When I was setting up my Barn door mount  to take photographs at the Britstown Star Party (6 - 9 August 2010)  it all came back to me. I used this pattern  some years ago to set up my SCT at Boyden Observatory.  I tried to find it on the web, but Google was of no help. So if I stole the idea from someone, please let me know and I will credit you. 

What you need to plot the SCP
  • 7 X 50 m binoculars
  •  A steady hand or a tripod for the binoculars.
  • A green laser pointer will help. Mount the laser and binoculars on a tripod.
    Adjust the laser light to show in the center of the binocular view.
How to find the SCP
1. Find the constellation Octans. Use a planisphere, software like The Sky 6, Cartes du Ciel etc. or Map 1 below.
2.  Zoom in and plot the Table mountain figure on map 2. It is almost magnitude 6 stars. So be patient. When you get familiar with the star environment you will find them with the first pointing of the binoculars. PRACTICE!

3. Use the third map to pinpoint the SCP
  • Upsilon Octantis
    Object name: SAO 258932 Other ID: HIP 111196 Magnitude: 5.76 Flamsteed-Bayer: Upsilon Octantis
  • Tau Octanti
    Object name: SAO 258970 Other ID: HIP 115836 Magnitude: 5.50 Flamsteed-Bayer: Tau Octantis
  • Sigma Octantis
    Object name: SAO 258857 Other ID: HIP 104382 Magnitude: 5.45 Flamsteed-Bayer: Sigma Octantis
  • Chi Octantis
    Object name: SAO 258799 Other ID: HIP 92824 Magnitude: 5.29 Flamsteed-Bayer: Chi Octantis
I hope there is method to my madness.
- Connect Tau Octantis and Chi Octantis
- Draw a 90° line through Sigma Octantis. This line will pass very close to the SCP.
- Sigma Octantis is 01°02'37" from the SCP
- The star (mag 6.8) is 00°13'41.818" from the SCP.

How close do you want to get to the SCP?

Charts: TheSky6

Hannes Pieterse
ASSA Bloemfontein
South Africa