#85 | ast01 – Stargazer

Hi everyone!

Last time I’ve told you that working harder is good, but working smarter is also something important. Like I said, to be lazy is a great thing to take a break for your brain and working smarter gives you a lot more time for everything else. The good thing is that our knowledge can be extended almost infinitely so, working harder and smarter is a good start to build your own mind encyclopedia. I also think it is important to have free time and learn other things than what you use to work in your comfort zone: extending the knowledge is always a good thing for a personal development.

Today, let’s talk about how to set up the Right Ascension circle. To be honest, I had not understood how it worked, but it was really easy and the reason why I couldn’t find the good set up was that I needed to know the coordinates of a reference star. Let’s me explain: the Right Ascension (R.A) is calculated with Hours, Minutes, Seconds. The Declination (DEC) is calculated with Degrees, Arcminutes, and Arcseconds. However, your R.A disk can move and the reference point is not necessarily on 0h0min, so you need to know exactly by how far your telescope will go from a star to another on the disk. Which means that you need to know a localization of a constellation and its stars.

For example, you can take Dubhe, one star of Major Ursa constellation. The coordinates are written in a catalog of stars (easily found online) so you can check where is its position. Dubhe is one of the brightest stars of the Major Ursa constellation and is localized at 11h04min on the RA disk and +61°46′ on the DEC disk. The distance of Dubhe from Polaris is the same as five times the distance of Polaris from the next star of the constellation Minor Ursa.

So when you get Dubhe in check on your finderscope and telescope optical tube, you can change by tightening the screws of your telescope to make it stands still. Then, you just need to change the RA coordinates on the disk with “11h04min”. And now, you only need to turn the RA adjustment screw to follow the star through the sky. Voilà! You can now find other objects in the sky by knowing where are their coordinates!


fig.01 – Boötes constellation with its brightest star at the bottom: “Arcturus“. (By the way, sorry for the bad quality of the picture. I’ve taken it in a rush and just set quick parameters).
fig.02 – Chart 5: “URSA MAJOR, BOOTES, CANES VENATICI, CORONA BOREALIS 12h to 16h +65 to +20”  Copyright@2005 Andrew L. Johnson (Image: http://www.eyesonthesky.com/StarCharts.aspx)

Ps: Remember to look at the two values on your RA disk. The true value depends on which side you turn your optical tube. I know it is a silly tip, but it is really important.
Pps: If you have some difficulties with the coordinates, use a star chart that can show the constellations positions depending on the month and the hours. You can print your own and make it very easily in paper.

What did I learn?

  • Set up RA and DEC disks (and reading them!)
  • Reading and writing star coordinates
  • Stars: Spica, Regulus, Polaris, Arcturus, Cor Caroli
  • Constellations: Major and Minor Ursa, Leo, Cor Caroli, Boötes, Virgo, Corona Borealis
  • Using Star charts

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