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)Share This:
Recent Astronomy Articles at Cosmic Pursuits
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 17th 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 TelescopesShare This:
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.
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.Share This:
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 TelescopesShare This:
Even the most expensive and carefully crafted telescope isn’t worth much if it’s not on a solid and stable mount that lets you accurately point it anywhere in the sky. A good telescope mount is as important as the optics of a telescope, and it must be sufficiently solid and stable such that if you give the telescope tube a good tap on the side, the mount should damp down vibrations in less than 5 seconds (max), and faster if you’re planning on astrophotography. Most telescopes, especially scopes aimed at beginners, include a mount when you buy them. Smaller telescopes, especially high-end refractors, may just have mounting rings or plates which allows them to be attached to a mount which you buy separately. And if you are contemplating astrophotography, a solid mount is a must-have.
All telescope mounts can be classified as one of two types: alt-azimuth or equatorial. Let’s have look at each [Read more…] about A Primer on Telescope MountsShare This: