Last night, I was watching Jupiter for nearly 2 hours awaiting the emergence of Io from occulation with my 8" Discovery PDHQ Dob. Now, I've this event many times with my 4" TV-102 APO refractor.
At the appointed time and even after 1/2 hour later, I still couldn't see it. Thinking that the Planets applet may have orbital calc. error which I was planning to report, I continue to watch (thanks goodness for the generous eye relief for the Radian eyepiece for extended viewing). At approx. 05:33UT, I noticed a really dim "star" some distant from the following rim of Jupiter and brightening rapidly. I realized then it was Io! But I never saw it when it was emerging from the rim of Jupiter. How can this be?
Then, it dawned on me that it must have been the spider vane of the Dob hiding Io all this time. What do you think? If this is true, the Dob can be a real bummer when trying to time transit/occulation because a Newtonian OTA on EQ mount can be rotated and thus re-positioned the spider vane. While the event was a disappointment (as
this would have been the first time with my Dob), it was most emerging from observational occulation.
Thanks for your comments.
Ron B[ee]
At the appointed time and even after 1/2 hour later, I still couldn't see it. Thinking that the Planets applet may have orbital calc. error which I was planning to report, I continue to watch (thanks goodness for the generous eye relief for the Radian eyepiece for extended viewing). At approx. 05:33UT, I noticed a really dim "star" some distant from the following rim of Jupiter and brightening rapidly. I realized then it was Io! But I never saw it when it was emerging from the rim of Jupiter. How can this be?
Then, it dawned on me that it must have been the spider vane of the Dob hiding Io all this time. What do you think? If this is true, the Dob can be a real bummer when trying to time transit/occulation because a Newtonian OTA on EQ mount can be rotated and thus re-positioned the spider vane. While the event was a disappointment (as
this would have been the first time with my Dob), it was most emerging from observational occulation.
Thanks for your comments.
Ron B[ee]
