Showing posts from 2015

Total Lunar Eclipse, September 27-28 2015

Jill and I went eclipse chasing this evening.  I did initial research on the Clear Dark Sky site to see what conditions were going to be like.  After digging, I decided that somewhere south and east of Briggsdale was likely to have clear skies.  We ended up on the grounds of an old church called Osgood Church.  We were greeted by this raptor, which we took as an auspicious omen:

We were rewarded with gorgeous skies - only a few wispy clouds floated through occasionally.  Here is an all-sky shot taken with my Canon EF 8-15mm f/4.0L lens on a Canon 5DmkII camera that shows how nice the skies were:

Jill and I are there in the foreground next to the telescopes.  You can see the eclipsed Moon, as well as the Milky Way and the skyglow from Fort Morgan, Sterling, and smaller towns off past the horizon.

For the eclipse photos, I used a Canon 7DmkII camera on an Orion ED80T CF refractor - an 80mm diameter, f/6.0 480mm focal length triplet.  I mounted it all on my handy portable iOptron MiniTo…

Armchair science

I noted with interest this update from the DSCOVR mission:

Cool!  The DSCOVR mission is an Earth-imaging mission that takes a continuous stream of Earth images to monitor it for climate and other changes over time.  It happened to catch the Moon crossing the face of the Earth (go to the link for the animation - you'll be glad you did).  This will happen twice a year, when the plane of DSCOVR's orbit intersects the plane of the Moon's orbit in line with the Earth.

The DSCOVR web page says that the satellite orbits "a million miles" from Earth.  It turns out, you can calculate that distance just from this image and from the known sizes of the Earth and the Moon.  The Earth has a mean radius of 3,959 miles, and the Moon has a mean radius of 1,079 miles.  The ratio between the two is 3.67 - meaning the Earth is 3.67 times as big as the Moon.  But if you open up that image in Photoshop and measure the Earth and Moon in pixels, you will find this:

The Earth is 1595 pi…

*Big* Pluto Icosahedron

I made a Pluto icosahedron from my previous post, and I decided it was nice - but it needed to be bigger.  So I spent today figuring out the geometry to maximize size while minimizing paper.  Here's what I came up with - an icosahedron twice the size as the previous one, taking 4 sheets of paper.  It will be a little more complicated to assemble - you have to match all of the tabs just so - but it makes a nice model when it is complete.

It is in PDF format, since it is four pages.  Without further ado - Pluto.

More Icosahedral Models

A few years ago, I converted various planet maps to icosahedral models.  You can print these out, cut along the solid lines, fold along the dotted lines, and have a nice icosahedron to play with.  Since then, two more robot spacecraft have created global maps of planetary bodies.  Most recently, the New Horizons spacecraft flew past Pluto.  Here is an icosahedral projection of the data we have so far:

Also fairly recently, the Dawn spacecraft has orbited both Vesta and Ceres, two of the largest asteroids (or "dwarf planets" as the new nomenclature has it) in the Solar System.  Here are icosahedral projections of those two.  First, Vesta:

Next, Ceres - note the mysterious white spots toward the upper right:

All of the data used to create these projections was taken from Steve Albers' Planetary Maps Page, which I highly recommend.

Edit: A PDF file of helpful hints on assembling these can be found here.

Addendum - new vs. old Canon 100-400mm

In my previous post on this lens, I used a 1.4x teleconverter on both lenses.  I got a request to repeat the test without the teleconverters, so here are the results.

These are all shot at ISO 400, f/5.6 at 400mm, 1/1600s, autofocus with the center point, RAW.  It is later in the day, and it looks like light clouds and shadows moving in the breeze are slightly changing the lighting between the shots, so caveat emptor.  First the whole image with the old lens:

Next, the new lens:

Here are the locations of the crops I took:

First, the center crop.  The old lens:

The new lens - again, sharper even in the center (although the moving shadows from the windy day make it a little harder to tell):

The left edge crop, the old lens:

The new lens - significantly sharper:

And now, the corner crop, the old lens:

And the new lens.  It is no contest:

The chromatic aberration is not as bad with the old lens without the teleconverter - but the sharpness is still much worse than the new lens.  And auto…

Old versus new Canon 100-400mm zoom

Late last year, Canon introduced a new lens, the EF 100-400mm f/4.5-5.6L IS II USM (say that three times fast!).  Reviews held that it was a significant improvement over its predecessor (which is named the same, but does not have the "II" between "IS" and "USM"), and, in fact, was equivalent to their 400mm prime in image quality, but with tons of feature advantages.  I acquired the new lens this week, and have put it through a test to compare, stealing some techniques from my brother-in-law Edward Plumer.

Note - I have an addendum without the teleconverter in the mix.  It does not change the conclusion.

I set the lenses up on a tripod, pointed at a fork in the tree.  The contrast and colors in the tree are similar to those I find when taking wildlife shots.  Image stabilization was disabled in both lenses.  The new lens was attached to a Canon Expander 1.4x III and the old was attached to a Canon Expander 1.4x II (the previous model).

The lenses were att…