2021: The Giants at Opposition!

(L-to-R) Jupiter, Saturn, Uranus, and Neptune will reach opposition at some point this summer and fall. The planets will be far apart in the sky but are shown together in this composite image scaled to their relative sizes on opposition date. Your actual view in the telescope will differ. Jupiter & Saturn © Chuck Pavlick (Celestron 9¼ Edge HD with 2.5x Powermate and ZWO ASI 224MC camera), and Uranus & Neptune © Dane Hankin (Celestron NexStar 6SE with 2.5x Powermate and ZWO ASI 224MC camera).
Opposition: Earth and outer planet line up on the same side with Sun (bottom of diagram). Conjunction: Earth and outer planet line up on opposite sides of the sun (top of diagram). Courtesy NASA/JPL-Caltech.

An “opposition” happens on the day that Earth and an outer planet line up on the same side of the Sun. For Earth observers, a planet in opposition will rise when the Sun sets and will be in the sky all night. Around the time of opposition, the planet is brightest, practically fully illuminated, and displays the largest angular diameter for the year. Right before, during, and after opposition are prime-time for viewing and imaging a planet!
 
Amateur and large observatory scopes can do best when imaging planets at opposition. It was just announced this summer that amateur astronomer Kai Ly discovered an unknown moon of Jupiter while examining opposition images taken with the 3.6-meter Canada-France-Hawaii Telescope at Mauna Kea Observatory in Hawaii. This news comes just in time to take some confirmation images as Jupiter opposition season is upon us now!
 

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Paracorr-Newtonian for Visual and Imaging to f/3! Part 2

 
At top is a cropped image of the Pinwheel Galaxy (M101) by AstroBin user Luca Marinelli. All rights reserved. Imaged through Teleskop Service ONTC 10″ f/4 Newtonian with Tele Vue Paracorr Type 2 coma corrector and ZWO ASI1600MM Pro mono camera. At right is the Tele Vue Paracorr logo. At bottom are the placement and back focus diagram for the 3″ BIG Paracorr.

In the last blog, we covered the history of the Newtonian reflector, its inherent aberrations, and how Tele Vue’s Paracorr enlarged the “sweet spot” of fast scopes to cover the entire field. We also compared the Paracorr – Newtonian combination against more “exotic” telescope designs for imaging. If you missed it, you can read Part 1 before continuing.

Which Paracorr to Use?
Over the years there have been two optical versions of the Paracorr.  The original Paracorr came in various mechanical designs which developed as we developed new eyepieces. For this BLOG, we’ll focus on the currently available three versions of the Type-2 Paracorr: 2″ Photo/Visual, SIPS, and 3″ Photo models. Performance improvement over the original Paracorr is most noticeable on all Newtonian/Dobsonian telescopes of f/4.5 and faster.

Continue reading “Paracorr-Newtonian for Visual and Imaging to f/3! Part 2”