Relative Planets

Evenings of July 6th through July 8th, 2018

The weather was amazing this weekend, especially for early July.  Clear skies, no humidity, and bugs only became a problem on the final night.

On Friday evening I took another set of Jupiter pictures.  These are not shown, as the following day’s images were far superior.

After Friday’s Jupiter session, I kept the telescope out after midnight, so technically on Saturday, to image Saturn for the first time this year.  As always, I have to wait for the planets to clear trees to the Southeast.  Since Saturn is now a few weeks past opposition, I get a clear few of the planet shortly after midnight.

For Saturn, I checked my written log for the settings I used last year (ISO 3200 and 100 exposure).  These, according to my log, gave me my best results.  But thinking I could do better based on my recent Jupiter work, I decided to try ISOs at 1600 and 800 and exposures of 60 and 30, respectively.  Lower ISO means less noise.  The results were not too bad, but I think the 3200/100 settings are still the best, and will try those next time.

On Saturday night, I took what I think may be my best Jupiter yet.  The finder focus on my first attempt was near perfect, if not perfect.  Look at the cloud band detail!  I only wish the Great Red Spot was facing us more at the time.  You can also see Io next to the GRS.

Then on Sunday I dragged my big telescope to my front lawn to capture Venus setting in the West.  This is the first time I did that.  The results were much better than I expected.  You cannot get much from Venus beyond its general shape.

What is neat about lining all three images side-by-side is that they were taken with the same telescope and same equipment setup, so you get a great sense of their relative sizes as seen from Earth.  Venus is noticeably smaller even though it is the closest to Earth and approximately the same size as Earth.  Right now, Venus is just over 90 million miles (145 million km) away.  Jupiter is about 450 million miles (724 million km) past, and Saturn is 840 million miles (1350 million km) from us.

What I should have done was take an image of a star, to show its relative size as well.  Next time!

Equipment used this weekend:

  • 254mm homemade Dobsonian
  • Canon EOS at prime focus
  • TeleVue x5 Barlow
  • Neodymium filter

4 thoughts on “Relative Planets

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