Tuesday, April 16, 2013

Going Lower Tech

I am typing this on my old Palm IIIxe via its GoType keyboard. I've had this Palm PDA for over a decade and still rely on it for many simple tasks that I'm afraid smart phones aren't really good at. With the keyboard plugged in, it becomes an instant laptop, and many articles have been written on it.
I'm a firm believer, these days at least, in trying to do things more simply.  There was a time when dragging a laptop into the field to do astronomy seemed logical. Now, I'm finding that it really gets in the way most nights I choose to do so. The only time the laptop gets used at all is for imaging.
Many astronomers use portable computers in the field for a number of tasks, including having a handy reference for star charts. There may be an easier way to go about this. What is needed is some prior planning.
For one, there are plenty of smart phone astronomy apps that allow you to guide your telescope, check the position of Jupiter's moons, check the phase of the Moon, etc.  Smart phones, though, tend to be bright, even if you go to "night" mode.
This is where I found that e-readers have a real advantage.
Many of the lower end e-readers, whether they be low costs or simply older devices, use e-ink technology. They are not backlit, instead relying on external light. Their screens, though small, are very clear and easy to read. Perhaps most impressive is battery life; they can run for hours on a single charge. These e-readers make the perfect astronomical companion.
The two units I've used for my tests have been a third generation Kindle (Kindle 3) and a new Nook Simple Touch. 
Of the two, the Kindle 3 shows the most potential. Not only does it handle a variety of e-book formats, it can also display JPEG's, PNG's and GIF's. Create a folder called "My Pictures" and place the images in there. When you access the folder, it launches the built-in image viewer. This viewer is able to zoom in on the image as well, so you do not need to limit yourself to the 600 x 800 resolution of the screen. The hotkeys on the Kindle 3 are "q" to zoom in, "w" to zoom out, "f" for full screen, "c" for actual image size and "e" for reset zoom.
PDF star charts are another matter on the Kindle. If you are not familiar with Taki Toshimi's star charts, you should be. These charts are fantastic, but they are also much larger than the screen resolution on an e-reader. In the case of the Kindle, you can zoom in. Be aware, however, that it can be a little sluggish.
The other e-reader I tested was my much newer Nook Simple Touch, one of the more inexpensive units out there.  While the Kindle 3 has support for multiple formats, the much simpler Simpler Touch is limited to two, EPUB and PDF. Fortunately, images can be converted to PDF's easily with the right software. Unfortunately, on the Simple Touch, you are limited to the 600 x 800 resolution. This, sadly, eliminates the really nice Taki charts. There are still options, however, and the ones I want to cover are free.
A quick search on the Internet can provide you with plenty of free star charts aside from the ones mentioned, but it is very important to remember that these e-readers have very small screens, 600 x 800 on average. Roban Hultman Kramer has compiled a set of PP3 generated star charts that are designed to be used with the Kindle (for those unfamiliar with PP3, it was once used to provide the original star chart images for Wikipedia. It is not for the faint of heart, however). Installing them is very easy if you have one of the older e-ink models (he supplies instructions), and the charts are fairly easy to read, provided you switch to full screen mode. If you have a Nook Simple Touch, you will need to convert these images to PDF in order for them to be used. Also, they display ever so slightly smaller on the Nook, with no full screen, and unlike the Kindle, you can't page from chart to chart. The charts are still usable however.

Another option is to make your own star charts, using some of the various software packages and making sure to create images that are limited to the size of the screen (though, again, PDF's on the Kindle can be zoomed in on). 
The final solution is to look for astronomy e-books, and there are many that have passed into the public domain. One of the books I have tried on both devices is "A Field Book of  the Stars" by William Tyler Olcott . This simple book, first published in 1907, has plenty of very easy to read charts.  Olcott concentrated on what can be observed as opposed to many of the theories that abounded about the cosmos, and it looks as if the charts were custom made for e-readers. One thing I have noticed is that these charts are not centered properly on the Nook; they are off to the right, but fortunately still quite usable.

Another, even older, book is Garret P. Serviss' "Astronomy With An Opera Glass" , initially written in 1888. Much like Olcott, the concentration is on what can be seen modestly, in this case with the smallest of optical instruments available, the opera glass. Like the later Olcott, Serviss does not go much into the theories of the period but instead concentrates on the stars and constellations themselves. My only complaint is that the charts are done white on black. On the Nook, they look fine though a little dark. They turn out smaller on the Kindle, but you can zoom in on them; the Kindle even rotates them to better fit the screen.
There are no doubt other ways to use e-ink e-readers in the field, and these are really just a few suggestions. Give it a shot, lighten your load and go lower tech on your next night out.

Monday, April 15, 2013

Wiggle Animation of Crater on Mercury!

This evening, "Lights in the Dark", a Facebook astronomy page, posted a 3D two color (red/cyan) image taken by the Messenger probe. 

Since not everyone has access to those 3D glasses, I decided to make a 3D "wiggle" GIF animation by subtracting out the colors with GIMP and composing the two resulting images into this.

The Celestron FirstScope, A Review

My propensity for buying small telescopes tends to be a gamble. Many times, they are just not that good. Other times, there are components that show so much promise yet fall short due to small details (some of these are salvageable). Every once in a while, you find a real gem.
So it is with the Celestron FirstScope. This is a very small Newtonian telescope, 76mm in aperture with a focal length of 300mm focal length. That last number, the focal length, is important, yet somehow Celestron neglected to include it, at least not directly. More on how we determine that in a bit.
So, what comes in the box?

The telescope is very well made for the price. The focuser is set for standard 1 1/4" eyepieces. Around the outside of the optical tube assembly are the names of astronomers, plus the occasional "Galileo 400"; like the GalileoScope, this telescope was made for the International Year of Astronomy 2009, the four hundredth anniversary of Galileo's first telescopic observations. While most of the components are made of plastic, they are very well engineered. 

The telescope is mounted on a sidearm Dobsonian mount. There is no tripod, this is a tabletop design, but one that is very well made. The base moves easily and can be easily tightened if necessary. The altitude axis features a large knob for tightening. 

The instructions are really pretty basic, but then again this is a pretty basic telescope.

There is also a flyer advertising an accessory pack, including a finder scope, something which is not included in the kit. The separate accessory kit also contains two more eyepieces and some astronomy software as well as a carrying bag. This separate kit would be useful for the finder scope and carrier, but we will discuss the eyepieces in a moment.

Now, back to the optics. Included are two eyepieces, an H 20mm (Huygens) and an SR 4mm (Symmetrical Ramsden). 

They yield 15 and 75 power respectively. This information is included on the box, and provided us the necessary information to determine the focal length (for the uninitiated, magnification is obtained by dividing the focal length of the objective, the primary lens or mirror, by the focal length of the eyepiece). By working backwards, multiplying the focal length of the eyepieces by their power, the result was 300mm, our focal length. 
Our main mirror is not parabolic, like you'd find on most Newtonian telescopes, but spherical. A spherical mirror is easier to make, therefore making the price lower (the FirstScope can be had for between $25 to $49.99). The problem is that spherical mirrors have a reputation for being somewhat hard to work with on short, fast focal lengths, and our little FirstScope has a focal ratio of 3.95, making it quite short and fast. Unlike parabolic mirrors, spherical mirrors do not focus colors to a single point. Normally spherical mirrors work well for longer tubes, but our little mirror seems to work fine, but with caveats.
The included eyepieces are adequate, but could (or should) be replaced. The 20mm works the best, but has distortion as you head out towards the edge. It's field is also not terribly wide. The eye relief, how easy it is to view using the eyepiece, is decent, but not great. The 4mm is worse all the way around. It is serviceable, but not great.
It is that smaller eyepiece that pushes this instrument to the limit of its capabilities. The eyepieces included in the accessory kit are a 12.5mm and a 6mm. 6mm would yield 50 power, probably the most comfortable maximum this scope can achieve. However, this telescope works better with lower power eyepieces, ones with longer focal lengths.
I decided to test the FirstScope out on the thin crescent Moon this evening. The included 20mm eyepiece worked fine with the aforementioned considerations. But the view was good enough. Through the 4mm eyepiece, going to 75 power, the field of view was narrower but still yielded a recognizable Moon. Be aware, though, that the eye relief on this eyepiece is not very good.
As I said, the included eyepieces are probably best replaced, though the 20mm is better and should suffice. I switched to an older 20mm Kellner eyepiece, a sort of eyepiece that can be obtained cheaply. The view, while still 15 power, was vastly improved. The field of view was flat edge to edge with no distortion or discoloration.  From there I tried a variety of eyepieces, even some of my better .965" eyepieces, and the views were great.
Additional targets were chosen. The Pleiades looked good even with the included 20mm, but really improved with the 20mm Kellner. The sword of Orion, as well as the nebula, really incandesced, even under suburban skies. My last target was the optical binary Alcor and Mizar and searching for Sidus Luduviciana, their even fainter "companion". Again, satisfactory to great depending upon the eyepiece.
Bottom line - I recommend this telescope, but also recommend replacing or supplementing the eyepieces (you can probably keep the 20mm, as I've previously mentioned). It is great for looking at the Moon, but really excels at sky sweeping, taking in wide sections of the night sky and looking at groups of stars. In fact, if that is the route you choose for this instrument, you can probably do away with the notion of a finder scope entirely and simply use a lower power eyepiece to "sweep" in on an object and then switch to a higher power eyepiece as needed.
Otherwise, it is definitely worth the money, and should make a great "first scope".