A 3D Printed Finder ‘Scope

I wanted a smaller, lighter finder ‘scope for the Astrola, and I wanted right angle to stop straining my neck!

3D model of the 40mm finder ready for printing
3D model of the 40mm finder designed in OpenSCAD

I have been using a big Orion 9x60mm finder on the Astrola, the only telescopic finder ‘scope I have among the Telrads. It is nice, with a bright image that shows many faint fuzzies. It is also huge, and very heavy, it is also straight through, requiring one to crane your neck around to view through it on the Newtonian ‘scope.

A small, lightweight finder was in order, a perfect project for a newly arrived 3D printer.

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Neptune at Opposition

Today the planet Neptune will pass through opposition, directly opposite the Sun in our sky. The planet will be well placed for observation all night long, rising at sunset, transiting at midnight, and setting at sunrise. If you are looking to observe Neptune, it is currently shining at magnitude 7.8 in eastern Aquarius.

Neptune from Voyager 2
Neptune from Voyager 2, Credit: NASA /JPL

As the outer planets Uranus and Neptune move so slowly across the sky, the timing of oppositions is driven by the Earth’s orbit and occur each year at nearly the same time. Neptune’s orbital period is 164.8 years, taking over a century and a half to circle the celestial globe once. As Neptune was discovered in 1846, it has completed a little over one orbit since discovery.

A Conjunction Moon

I rolled the telescope out of the garage to view and photograph the conjunction of Jupiter and Saturn. It is impressive to see the two gas giants side by side like that. The photos were less of a success, with soft seeing they are not great. OK, the photos suck.

The Moon was a different story, high in the sky the seeing was much better. Since I had the camera on the telescope I shot a few photos of the first quarter Moon.

Look closely along the terminator and you can find the Lunar X, the V, and the Vallis Alpes…

Conjunction Moon
The Moon at first quarter on Dec 21, 2020

A View from the Past

As an evening pastime in these COVID restricted days I have been delving into the past again. Again reading the work of an amateur astronomer from long ago.

Frontspiece of Bedford Catalogue, 1844
Frontspiece of Bedford Catalogue, 1844, Capt. William Henry Smyth

I had previously read through the work of Rev. Thomas Webb, a vicar and amateur astronomer active in the late 1800’s. Webb frequently referred to the work of an earlier observer, Capt. William Henry Smyth.

Retired British Navy Captain Smyth was a backyard observer, gazing at the stars with a 150mm refractor from a garden behind his home in Bedford England. His telescope was quite good for the time, made by Tully of London, the best money could buy. This telescope was eventually purchased by the British Government to be used in the 1874 transit of Venus expedition to Egypt and the 1882 Venus transit in Jamaica. It now sits in the collection of the Science Museum, London.

Capt. William Henry Smyth's Telescope at Bedford
Capt. William Henry Smyth’s Telescope at Bedford

Smyth published two volumes on astronomy in 1844 under the title A Cycle of Celestial Objects . Volume II of this set, commonly called The Bedford Catalogue, contains descriptions of more than 1600 double stars, clusters, and nebulae, serving as a guide to what may be observed with a small telescope. The Bedford Catalogue became the standard at-the-telescope reference for other amateur observers for many decades until it was generally replaced by Webb’s Objects for Common Telescopes.

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