Size Matters

  • John D. Clark
Part of the Patrick Moore's Practical Astronomy Series book series (PATRICKMOORE)

This is something I have not talked about much. There is a reason.

I needed to derive some geometrical and statistical results to get us this far. Our hardest work is now over. The thrust of this chapter is actually very simple. Since I know how big the planets look in my photos, and I now know how far away they are, I can calculate their sizes.

I also need the stuff in Chap. 4 about converting lengths on photos to angles in arcminutes, which I showed you how to do in (4.1)–(4.7). The only slight difference from this treatment is that when taking planet photos, I used a Barlow lens. You have to multiply the image size you calculate in arcminutes by the magnification of the Barlow. Do remember to calibrate your Barlow: the quoted magnifications are not exact.

Do not forget that the Planet–Sun distance is not the Planet–Earth distance. The latter varies all the time as both planets orbit. This is obvious from, say, Fig. 1.12. The effect is less obvious in Fig. 6.22, but it is there. The...


Astronomical Unit Conjunction Date Walk Away Small Angle Approximation Minimum Standard Deviation 
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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  1. 1.King’s Lynn, NorfolkUnited KingdomEngland

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