Recent Astronomy Articles at Cosmic Pursuits

Refracting Telescopes for Astronomy

June 15, 2020 by Brian Ventrudo Filed Under: Astronomy Equipment

A top-quality refractor telescope (credit: Televue)

When the members of the great unwashed masses think of an astronomical telescope, they usually think of a refractor. With a large glass objective lens at the top of the tube and an eyepiece down at the bottom, refractors are the most robust and conceptually simplest type of telescope. They offer amazingly crisp views of the Moon and planets and double stars. But they are not for everyone. This short article goes through the pros and cons of refractors for astronomy and helps you decide if such a telescope is right for you [Read more…] about Refracting Telescopes for Astronomy

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Galaxies and Comet C/2017 T2 (PanSTARRS)

May 28, 2020 by Brian Ventrudo Filed Under: Celestial Events

Comet C/2017 T2 PanSTARRS Passes by Galaxies M81 and M82. Imaged at Grand Mesa Observatory by Terry Hancock and Tom Masterson (Credit and Copyright: Terry Hancock and Tom Masterson).

While a couple of promising comets have fizzled out this spring, the slow and steady Comet C/2017 T2 (PanSTARRS) is keeping astrophotographers happy as it moves through the northern constellation Ursa Major. On May 24, the comet passed the lovely pair spiral galaxies M81 and M82 near the bowl of the Big Dipper. The event was framed spectacularly in the above image by Terry Hancock and Tom Masterson using the Takahashi E-180 Astrograph at Grand Mesa Observatory in Colorado. This image is a testament to a high level of expertise and it shows how astrophotography at the hands of skilled and talented practitioners can approach high art [Read more…] about Galaxies and Comet C/2017 T2 (PanSTARRS)

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Newtonian Reflectors and Dobsonian Telescopes

May 26, 2020 by Brian Ventrudo Filed Under: Astronomy Equipment

A Newtonian reflector telescope on an equatorial mount (credit: Skywatcher).

Reflecting telescopes (or reflectors) collect light using a curved mirror at the rear of the main tube rather than a lens at the front end. Isaac Newton gets credit for inventing the first reflecting telescope in the late 17^th century. He used a second small diagonal mirror to direct light out the side of the telescope to an eyepiece. His immensely practical design, now called the Newtonian reflector, is the main type of purely reflecting telescope in use today by amateur astronomers [Read more…] about Newtonian Reflectors and Dobsonian Telescopes

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Supernova in Messier 61

May 20, 2020 by Brian Ventrudo Filed Under: Celestial Events

The Type II supernova SN2020jfo in the face-on spiral galaxy Messier 61 in the constellation Virgo. Captured on May 19, 2020 with a TV85 refractor, TRF-2008 0.8x focal reducer, and ASI290MM camera. Stack of 20x10s images.

The galaxy M61 has done it again: it’s produced another supernova, the eighth such event since 1926. That makes this lovely face-on spiral galaxy in the Virgo cluster one of the most prolific supernova producers of the past century.

The supernova, cataloged as SN2020jfo, was discovered on May 6, 2020 at the Zwicky Transient Facility at Palomar Observatory near San Diego. Upon discovery, the exploding star was magnitude 14.7. It’s since brightened to about 14.3. To see it visually requires at least a 10″ telescope, but it is relatively easy to take a snapshot with an astronomy camera and a much smaller scope. I took the 20x10s stack of images at the top with an 85mm Tele Vue refractor, an 0.8x focal reducer, and an inexpensive ZWO ASI290MM camera.

One of the more prominent members of the Virgo cluster, Messier 61 is a lovely barred spiral with winding arms knotted with star-forming nebula and clouds of blue-white stars. It’s a starburst galaxy, one wracked with prodigious star formation which explains why so many supernovae have been seen here. With lots of massive, fast-burning young stars forming, it’s inevitable that they reach their spectacular end as a Type II supernova during which the star, as it runs out of fuel, collapses and snaps back in a spectacular explosion. It releases as much energy in a few weeks as our Sun releases in its entire 10 billion year life span.

The face-on spiral galaxy Messier 61 in the constellation Virgo. Image courtesy of the European Southern Observatory (ESO).

M61 is about the same size as our Milky Way and lies about 52 million light years away, so the progenitor star detonated when Earth was in the Eocene period back when Australia and Antarctica were still connected and most of the planet was covered in lush forest.

And since astronomy is not just a matter of contemplating space but also time, keep in mind that the light from thousands more supernovae from M61 are on the way to us now, events to be detected by generations of Earth-bound astronomers yet to be born.

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Schmidt-Cassegrain Telescopes

May 14, 2020 by Brian Ventrudo Filed Under: Astronomy Equipment

A Schmidt-Cassegrain telescope (credit: Celestron)

In the most recent article on telescopes, you had a look at Newtonian reflectors, the oldest type of mirror-based telescope for astronomy. Newtonians, as you learned, have one big drawback: they are big. Because they use a single primary mirror to direct light back to a flat secondary mirror, which in turn reflects light to the eyepiece at the side of the tube, the physical length of a Newtonian is roughly equal to its focal length. So a 12″ aperture f/6 Newtonian, for example, is at least six feet long and more than a foot wide. But in 1672, shortly after Issac Newton developed his famous design, an obscure French Catholic priest named Laurent Cassegrain invented a reflector that used two mirrors to fold a long optical path into a much shorter tube. Now many reflectors, and nearly all professional astronomy telescopes, use some variation of the Cassegrain design [Read more…] about Schmidt-Cassegrain Telescopes

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