Saturday, October 19, 2013

Plato Crater, Stray Light

Just doing a quick observation session, the full Moon beckons, and the weather is (almost) good.
  • Full Moon was yesterday (and even a partial lunar eclipse), today the Moon was waning gibbous (Illuminated fraction: 0.993 Phase: 350°)
  • Some seeing visible on the Moon's limb (in both the 150/750 and the 114/500), still not sure if this is atmospheric seeing or tube seeing
  • The 114/500 has awful stray light problems. It depends a bit on where the Moon is in the FOV, and at what angle one looks into the eyepiece. I then looked into the focuser's tube without an eyepiece: The body of the secondary is made from shiny plastic – what could possibly go wrong with such an design??? Well for one thing: the light passing the plastic obstruction before hitting the primary is glaring, which is visible through the focuser tube (when viewed without an eyepiece). And secondly the area around the secondary is visibly shiny when viewed through the focuser.
  • The 150/750's secondary has an similar plastic body, but much less problems. I will have to baffle both, I'm afraid…
  • Plato Crater really stands out quite dark from the somewhat brighter Montes Alpes.
  • The Moon is a good target to asses things like stray light and focusing. 
  • I'm so glad to have bought the 150/750 Newton! 6-inch vs. 3-inch means twice the resolution and four times the light gathering. Can't wait to take a shot at Jupiter, and the Andromeda galaxy.
  • My eyepieces are fogging over. Had to take a break and put the eyepiece case inside to warm up again… (Maybe I'm dressed a bit too warm, as I'm slightly sweaty…)
  • I wanted to hold out and view Jupiter – but I got unbearably tired, my muscles started to hurt and clouds started to roll in – so I packed up again.
  • I ask for only one thing: A house in the south of France…

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