In this installment, we travel to Kitt Peak in the Arizona-Sonoran Desert to “speckle” binary stars and finally learn what the impressive-sounding Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne group does! (If you missed our prior Tele Vue Scientific installments, you can click to read Part 1 and Part 2).
4x Powermate and Speckle Imaging at Kitt Peak
Introduction Often practiced by amateur astronomers doing planetary work, “lucky” imaging was invented by professional astronomers to try to “freeze” distortion of starlight passing through our planet’s turbulent atmosphere. This is done by taking many short exposures of a target, instead of one long one. Amateurs usually align and stack the best quality photos to create an image. Professionals use their data to perform speckle interferometry involving complex math. Speckle interferometry is useful in refining the orbits of close binary stars. The introduction to a 2014 paper, “Kitt Peak Speckle Interferometry of Close Visual Binary Stars,” explains how this works.
The resolutions of conventional visual binary observations were seeing limited until Labeyrie (1970) devised speckle interferometry as a way to circumvent seeing limitations and realize the full diffraction-limited resolution of a telescope. The light from a close binary passing through small cells in the atmosphere produces multiple binary star images which, if observed at high enough magnification with short exposures (typically 10 to 30 milliseconds), will “freeze” out the atmospheric turbulence and thus overcome seeing-limitations. Although the multiple double star images are randomly scattered throughout the image (often superimposed), their separation and position angle remains constant, allowing these two parameters to be extracted via Fourier analysis (autocorrelation).
The paper says that this technique, made practical with the introduction of the CCD camera, resulted in an order of magnitude improvement in binary star data measurement over visual observations. Speckle interferometry then became the preferred technique for characterizing close binary stars.
Back in December 2018, we featured some spectacular wide-field, deep-sky images by Diego Cartes Saavedra in Chile. All the images were taken with his Tele Vue-76 APO refractor and Tele Vue TRF-2008 0.8x Reducer/Flattener. This combination achieves a 380mm focal length at f/5, ideal for imaging large swaths of deep sky. You can still read the original blog at Tele Vue-76: Imaging the Southern Hemisphere. At the end of that post, we wished Diego continued success in his astrophotographic journey. Ever since, we’ve followed his progress through his postings on the AstroBin imaging hosting platform for astrophotographers. We felt it was time to “catch up” with him and post some of his latest captures in this gallery blog.
NGC 6188 ─ The Fighting Dragons of Ara (Hubble Palette)
Prior generations of supernovae explosions spread dust and gas in this complicated region of space. Continued explosions compressed this material and sparked the formation of new massive stars. Stellar winds from these stars intricately sculpted the region into areas of glowing gas, reflection nebulae, and dark clouds of dense matter. The resulting dark, dusty lanes conjure up images of two dragons. Light from open cluster NGC 6193 illuminates the large blue reflection nebula where the dragons face off. The dense, blue object at the lower-right is pk336-00.1 (also NGC 6164 & NGC 6165) ─ an emission nebula formed from the expanding outer layers of a giant, hot, O-type star at the center. Around this compact object is the faded outer ring of reflected blue dust from earlier shedding events. This image was awarded an AstroBin “Top Pick” nomination.
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!
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.
Paracorr and the Evolution of Newtonian / Dobsonian Telescopes
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.
In the last installment, our scientific path went from “polar to solar.” (If you missed it, please go back and read Tele Vue Scientific Part 1.) In Part 2 of this multi-part blog post on the use of Tele Vue gear in science, we reveal Sneakey research with Tele Vue Powermates and how a compact Tele Vue-NP101is telescope proved once again that lights are “all askew in the heavens.” All this research was done using our standard gear with products bought off-the-shelf — the same as you would receive from Tele Vue.
The above portrait of the Horsehead and Flame nebulae is stunning. Created in Hydrogen-alpha light, this monochrome image is filled with wispy tendrils, puffy molecular clouds, dark lanes, and glowing gas. It really brings out the interplay of shockwaves and ionizing radiation at work in this region of the much larger Orion Molecular Cloud Complex.
You can compare this image with the color one below of the same region. The red hues are dramatic, but we lose a sense of the “sculpting” that is taking place in the gas and dust.
The Horsehead (Barnard 33) and Flame Nebulae (NGC 2024) are separated by the bright blue supergiant star Alnitak (center-left in the above image), the easternmost star in the “Belt” of constellation Orion. Like a giant neon sign, the “Flame”, below Alnitak in the image, is “lit up” by ultraviolet light from the star. The flame-like appearance is enhanced by dark “branches” of light-absorbing gas in the nebula. As for the Horsehead, its appearance is due to the three-star system Sigma Orionis “above” the “horse” (bright star along a line through the horse’s neck and head). It causes hydrogen gas to glow behind a dark concentration of dust that has the distinctive appearance of a horse’s head.
Tele Vue’s product quality, consistency, and reliability are well known in amateur astronomy circles. So, it shouldn’t come as a surprise that our top-tier optical performance also attracts the interest of professional astronomers looking for “off-the-shelf” solutions for their experimental needs. Tele Vue also provides researchers with the in-depth technical analysis necessary to determine if product integration is feasible or if custom solutions are required.
In this multi-part blog post we’ll explore some of the published science using our standard gear and take a look at a future science mission that called for a custom designed Tele Vue lens. Note that all the studies in the series, except the last one in this part, were produced with products bought off-the-shelf, same as you would receive from Tele Vue.
The lead-off image of this post is certainly an eye-grabber! It is one of the most unique interpretations of the Rosette Nebula (NGC-2237 or Caldwell 49) in Hubble Palette filters we’ve seen. Most striking, the usual Hubble Palette aquamarine color surrounding the central cluster is cobalt blue! The typical outer ring of yellows and burnt ochre now has a deep-orange hue. This color manipulation was done while maintaining the filamentary wisps and dark protostar Bok Globules in the nebula, along with a jet-black sky background. The resulting dimensional quality of this image draws the viewer from the ruddy edges of the nebula into the blue-colored center and then out the “back” aperture of the structure.
In the middle of the Covid pandemic, stuck at home, I decided to resurrect an interest in astronomy, and in particular astrophotography.
This image is from a great collection of Tele Vue NP101is images posted by Linwood Ferguson on SmugMug. At the top of this SmugMug page is stated the motivation for his astro imaging: “In the middle of the Covid pandemic, stuck at home, I decided to resurrect an interest in astronomy, and in particular astrophotography”. In this blog, we present a gallery of Linwood’s NP101is images.
Northeast Astronomy Forum (NEAF) 2021 — “the World’s Largest Astronomy & Space Expo” — is in the history books after streaming 10-hours of material on April 10th. Tele Vue provided seven unique videos for the event and we’d like to thank all who tuned in and showed their support in the chat!
Each of our videos answers a question from one of our blog readers. If you want to review them, they’re all linked below and cued up to the question being answered.
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