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.

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Paracorr-Newtonian for Visual and Imaging to f/3! Part 1

At left is the original Paracorr with the Parrot Mascot. “Strawberry Fields” was a set of stickers on Al Nagler’s backyard shed (built by Al, David, and grandpa Max!) that were used to illustrate how the Paracorr eliminates coma in the corners. Within “Strawberry Fields” are superimposed various versions of the Paracorr.
Paracorr and the Evolution of Newtonian / Dobsonian Telescopes
Chromatic aberration in a simple glass lens. In this exaggerated image, each color (wavelength) of light focuses a different distance behind the lens. (public domain image)
Invented from lenses used to make eyeglasses, refractors were the first telescopes when introduced in the 1600s. However, the early refractor builders could not avoid building scopes that displayed color fringes (chromatic aberration) around bright objects. It was Sir Isaac Newton (1642–1727) who figured out that white light is composed of different wavelengths that we see as colors. Each wavelength will refract (bend) by a different amount as it passed through the refractor’s objective glass. The longest wavelengths (red) refract less while the shorter wavelengths (blue) refract more. As a result, the red component of the image focuses behind the blue component. Pinpoint images and higher magnification were out of the question with these primitive scopes. Even after the cause of chromatic aberration was revealed, refractor builders didn’t have the glass types and manufacturing skills to counter it for another century. Sir Newton, however, had an idea to build a second type of telescope that avoided refraction: a reflector.
 

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Powermate Solar Imaging from Kent, UK!

Proms Mono by flickr user Paul Andrew. All rights reserved. Used by permission. Lunt LS152 Solar Telescope (obj: 152mm / fl: 900mm) with Tele Vue 2.5x Powermate and imaged with ZWO ASI290MM monochrome camera (1936px x 1096px, color added in post-processing). Taken 20th May 2020 from Kent, UK. Solar prominences dance along magnetic field lines on the limb of the active Sun while fibrils of super-heated plasma fill the foreground.
Paul Andrew has been an amateur astronomer since the age of 11. He is the founder and Honorable President of the South East Kent Astronomical Society in the UK. He’s had a number of his astrophotographs published  — in particular, his solar images  — in national newspapers and on websites as far afield as Russia. He’s been short-listed for the prestigious Insight Astronomy Photographer of the Year competition four times now. We’ve noted his high-quality solar images and discovered that many were made with our Tele Vue 2.5x Powermate in the imaging train. So, we present a selection of his work in this week’s blog.
 

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Tele Vue’s Year End: Behind the Scenes!

As we close-out the year, we’d like to update you on what is going on “behind the scenes” at Tele Vue! From the arrival of the Apollo 11mm eyepieces to the ongoing GoodBuy 2019 Sale, and answering your questions in between, our employees in upstate New York are somewhat like Santa’s “elves” this time of year!

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Tele Vue APO Design and Build “Secrets”

Over the years, we’ve seen conversational topics in online amateur circles that repeatedly crop up concerning the definition of apochromatic refractor, triplet vs. doublet design, and how glass designation might define performance.  We expect these questions to continue to appear as new amateurs discover the hobby. So bookmark this blog post because here you’ll find notes on Tele Vue’s philosophy and build practices concerning our telescope line of 100% APO refractors.

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TNVC Night Vision Direct from Tele Vue

(TNV-1400) TNV/PVS-14 L3 Gen3 Un-Filmed White Phosphor

Tele Vue has taken its collaboration with Tactical Night Vision Company one step further! We are happy to announce that we now offer their TNV/PVS-14 L3 Gen3 Un-Filmed White Phosphor night vision monocular plus accessories direct from Tele Vue.

Al Nagler Goes “Full Circle” on Night Vision
Back in 1971, while an employee of Farrand Optical Company, Al Nagler was given the task of designing an eyepiece for a spiffy-new, high-tech gadget designed by ITT Corporation: a night vision device. He designed an eyepiece to view the 40° field of view created by the image intensifier tube. Now, after almost 40-years of evolution, the latest generation night vision  monocular that Tele Vue is selling uses an eyepiece at least inspired by Al’s Design — if not exactly the same!
 

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Jupiter Opposition June 2019!

Solar System (Jupiter) by flickr user Eugene Beygin. All rights reserved. Here Jupiter’s Great Red Spot is facing Earth with the four Galilean satellites (labeled) on either side of the giant planet. Taken through Celestron C6-N Newtonian (6″, f/5) with Tele Vue 3x Barlow through QHY5III224 color CMOS planetary camera and tracked by Celestron AVX mount.
On June 10th, Jupiter was closest to the Earth and rose at sunset — placing it in the sky all night long. The timing makes it well placed for observation throughout much of the summer. Currently, the planet is at its best for the year, at magnitude -2.6 with an angular diameter of 46-arc-seconds. It will “fade” slightly to a still very bright magnitude -2.1  and shrink to 36-arcseconds by the start of fall, where it will be in the west at sunset, setting just a few hours later. So, now is prime-time to view and image this gas giant planet, its famous Great Red Spot (GRS), and attendant giant moons.

The Sun from Sunny Barcelona, Spain

protuberancias y superficie solares – 18/11/2017 by flickr user Jordi Sesé. All rights reserved. Used by permission. In this impressive image, a massive solar prominence erupts above the limb of the Sun. Furry spicules are visible along the entire edge of the disk. The roiling surface appearance of the Sun is caused by filaments and fibrils (prominence and spicules away from the limb — see blog text for details). All these solar features are usually invisible in ordinary white light. These phenomena are only revealed through narrow-band hydrogen-α light filters. Tele Vue 2.5x Powermate™ into ZWO ASI174MM monochrome camera using 100mm f/10 achromatic scope with modified Coronado PST Hα and BF10 blocking filter.

If you’re suffering from the cold northern winter like we are at Tele Vue headquarters in upstate New York, you’ll instantly be “warmed” by these “hot” solar images made by Jordi Sesé Puértolas from his balcony in Barcelona, Spain. These photos appear to show a blazing inferno on the “surface” of the Sun. However, science tells us this is not fire we are seeing but hot plasma (ionized gas) and gas in the wavelength of Hydrogen-α light.

Return to the Moon with Michel Deconinck

This year all eyes will turn to the Moon to mark the 50th Anniversary of the first Moon landing. The Moon is the natural first target for new amateur astronomers, yet all too often as observers become seasoned, the Moon becomes a nuisance that blots the stars from the sky. This week we explore the Moon through the eyes and talented hands of Michel Deconinck. As you will see, there is much to see in the monthly dance between shadow and light on the lunar surface.

The Crater Copernicus © Michel Deconinck. All rights reserved. Used by permission. Tele Vue 10mm Delos eyepiece (100x) with 4” f/10 Bresser refractor. The 93 km Crater Copernicus was drawn on July 26, 2015, during a waxing gibbous Moon phase. “It is rather difficult to draw, many subtle details emerge such as the arc of small impact craters and its network of lighter lines that are visible over several hundred km. Some landslides are also visible, …”.

Michel Deconinck is an artist in the South of France with a passion for astronomical watercolors. He is very involved with the international astronomical community and his artistic works have been published in magazines, scientific journals, and displayed at conferences and school events. His artistry is augmented with a background in nuclear physics, engineering and astrophysics.

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Tack Sharp Stars: Overcoming Eyesight Astigmatism

Simulated image of DIOPTRX™ astigmatism correction. Your experience may vary.

This guest blog post is written by Phil Ressler, a longtime amateur astronomer who lives in Los Angeles, though his observing life began on the east coast. Phil is a veteran software industry executive, currently CEO of Sixgill, LLC.

I had never seen pinpoint or round stars — apart from observing our round Sun.

I’m old enough to remember when “pinhole” eyepieces with “soda straw” views defined what a telescope offered to the average amateur astronomer. More than anyone, Al Nagler, and more than any company, Tele Vue, changed that by opening up the sky and making it easier to explore through wider field viewing. Mr. Nagler and his company also showed us that a relatively rich field refractor could not only capably serve as an amateur’s sole telescope: it is the best telescope to own if you’re only having one. We can thank Al Nagler and Tele Vue for laying the foundation for the way visual astronomy is pursued today. Yet despite all that, until I tried a DIOPTRX™ on my 22mm Panoptic last year, I had never seen pinpoint or round stars — apart from observing our round Sun. I’ve been observing the sky through scope optics since 1961, my astigmatism never absent. For people like me, DIOPTRX™ is arguably Tele Vue’s most essential product, because it makes all of Al Nagler’s original work in eyepieces and refractors unmistakably worthwhile to the astigmatic viewer.

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