Thomas Harriot's Moon

Between 1609 and 1610, Englishmen Thomas Harriot produced a number of drawings of the Moon, as well as what is probably the first map of its surface as well. The instrument he used was a simple Dutch "trunke", a telescope, of what we generally refer to as "Galilean" in design.

That is, of course, a misnomer; Galileo did not invent this optical design, he refined it. Others proceeeded him, Hans Lippershey in particular, with Sacharias Jansen and Jacob Metius also playing significant roles. 

Yet it was Harriot who aimed a telescope skyward and recorded the results.

It is interesting when we compare his map of the Moon with a modern image.

One of Harriot's Moon maps, Courtesy The Science Museum, Kensington

My image of the full Moon, early morning of the 23rd June, 2013 (the so-called Super Moon)

While not as artistic as Galileo's drawings, it is nevertheless remarkable, and proof of what a small telescope is capable of revealing to the humble viewer.

Galileo, Scheiner, Sunspots & Saturn

I decided to work on my Galilean-Scheiner sunspot study by conducting a test of instruments with those old optical layouts. For this, I used my facsimile Galilean and my small Keplerian.

Someone replied not too long ago that looking through a long tube Galilean telescope was akin to looking through a straw. Nothing could be more frustratingly true, but from a projection standpoint, it works much better.

However, the question must be asked, which telescope did Galileo use? The long tube instruments are incapable of projecting a full Sun; they simply have too much magnification. 

Surely, he used a smaller instrument. It was obvious, though, that it could be done, and the result is simply a mirror image.

Christoph Scheiner, however, preferred the Keplerian telescope. The Keplerian design uses plano-convex lenses for both objective and eyepiece. Like the Galilean, it is a simple two element design, but it produces a much better field of view. The tradeoff is that the image is inverted, but for astronomical purposes, this really isn't a problem. Scheiner was an early proponent of this design, and perhaps to be credited for its greater acceptance.

As expected, the images produced by the Keplerian were brighter and much clearer.

In this case, the image needs to be rotated 180°. I've enhanced it somewhat to bring out some of the sunspots.

The final test will be the creation of a Galilean eyepiece for the small Keplerian telescope, and a projection made to see if that approximates the studies performed by Galileo. In the meantime, it is clear that Scheiner does deserve more recognition for his pioneering work.

Wave At Saturn Night!

Tonight is "Wave At Saturn Night". This showed up on my Facebook page yesterday. This is the first time I've seen or heard of it. Nor am I able to find it again. But it seems like such a fun idea. Silly, yes, but fun.

Holidays like this, though, will forever be moving ones; planets fail to appreciate our calendar and seldom tarry long in one place.

Tonight, Saturn is pretty close to zenith at sunset. with a waxing gibbous Moon to its east. The white moonlight should proved strong contrast to Saturn's yellowish hue. 

If you get the chance to, be sure to take a step outside and look for Saturn, that bright yellow star north and west of the Moon.

Addendum - It was Philip Astore, amateur astronomer and professional firefighter, who made the comment about looking through a straw. Anybody who loves astronomy is a friend in my book, but this fellow also has one of the toughest jobs in the world. Stay awesome, Philip.

First First Light - The Anniversary

A few entries back, I wrote about my first first light with my old Tasco 50mm. The date I included was wrong; it was actually the 14th, not the 18th. It was a Sunday night.

Anyway, to commemorate the event, on the night of the 14th, I decided to recreate that moment with my Tasco 50mm, same model I had back then. I used two of its original eyepieces, a 20 and 12.5mm, both Huygens, as well as a new 20mm MA. All three eyepieces are, of course, .965".As with that night, I chose to observe Saturn, as well as the Moon.

What a difference thirty years makes.

The Moon that night was near full. I knew back then from using my binoculars that the Moon isn't much fun to observe near full. For the 32nd anniversary session, it was waxing crescent, and glorious. In 1981, Saturn and Jupiter were near one another. in 2013, Saturn lies just east of Spica.

The sky over Jacksonville the night of the 14th June, 1981.
(Courtesy YourSky at Fourmilab)

The night sky over Jacksonville, 14 June, 2013.

And like then, the sense of wonder I felt, even with such a small instrument, was the same.

I simply love the heavens.

Such a fine little instrument. The tripod isn't original, but everything else is. I seldom use small telescopes with finder scopes, by the way.

A Fireball, If Ever So Briefly

Last night, at 9:48 PM, I was exiting the van in the driveway when something caught my attention up in the north-northeastern sky. I turned just in time to catch a fireball. It was easily brighter than Venus. Duration was maybe three seconds, tops.

The problem was that the beautiful live oaks that make this part of Jacksonville so alluring were in the way. Still, this object was so bright it showed through the tree canopy. 

It also led to my first fireball report to the American Meteor Society. 

I've seen literally hundreds of meteors, dozens of fireballs and a handful of explosive bolides. I have never taken the time to report the more significant events. Even when I worked as an astronomy educator, this little matter went to the wayside. For me, those astronomical objects of true desire for me, the planets, open and globular clusters, stellar associations and such, were far more important than these errant pieces of Solar System jetsam and flotsam. In light of the interest in the possible recurrence of the legendary Gamma Delphinids, however, I decided to, for once, be a responsible observer and report the fireball. 

From my vantage point, this is the path the object took.

As it turns out, I wasn't alone. There were two other possible sightings from two very different locales; Myrtle Beach, South Carolina and Lakeland, Florida. Taken together, with information gleaned from the pending reports at the AMS site, we get the following. 

The green lines represent line of initial sighting, the red the last. Angles are approximated. The yellow path is a potential trajectory that the object may have taken. Unfortunately, to verify that trajectory, exact times for all the sightings would be needed.

Nonetheless, it was a bit thrilling to catch such a wondrous event, albeit briefly. 

You never know when you have just observed a greater event, and when you contribute that information, you are doing, you guessed it, science.

Next time, better notes.

UPDATE -
The AMS has compiled a total of five reports, of which mine was one. Here is the final analysis -
Event 1267

Three Planets in the Western Sky

The weather finally cooperated this evening to allow me to get some shots of Jupiter, Venus and Mercury in the western sky.

Here it is labelled, for your convenience.

Finally, some of the images worked out perfectly as an animation, so here it is.

Such beauty. Glad to have finally been able to capture it.

Aiming for the Sun

When examining the early designs of "helioscopes", specifically those of Christoph Scheiner, one thing always seemed to be puzzling to me. What method did they use to align the telescope with the Sun?

These days, whenever a solar filter is employed, we tend to use the "least shadow method", that is the smallest shadow cast by the optical tube. If the shadow is fairly circular, you're close, and it then simply becomes a matter of minor adjustments. These early telescopes weren't so forgiving. For one, they had a very narrow field of view, especially the Galilean designs. You could employ the least shadow technique, but you now had the problem of sunlight hitting your screen. That makes the following image somewhat puzzling.

We know that many of these early designs, especially those of Scheiner, had a shield of sorts. In his first design, there was not just one shield but technically two; a smaller one towards the front, followed by the main shade. The main shade was approximately the same size as the "tabella", the rear of the instrument, where the "chartis" was positioned. Since this was all one instrument, all one had to do was align the shadow of the large shade onto the "tabella", and the instrument would be pretty close.

On my little experiment, I chose to try a second shade, towards the back of the instrument. Both shades are about 8" (200mm) square. 

By aligning the shadow of the forward shade onto the rear shade, we were able to aim the telescope.

Not enough contrast, but you get the idea.

In late designs, Scheiner appears to have dispensed with shades. In a more advanced version of his helioscope, the instrument is mounted on an early equatorial mount and aimed through a small hole in the ceiling through which the Sun is visible. This design is advanced yet somehow awkward.

In all the documentation, no mention is made of how the telescopes were aimed. This is purely speculative, but appears to work and truly makes using the "helioscope" a much simpler affair.
(EDIT - It appears as if the second design did have a finder of sorts. According to an article written by H.D. Curtis, "Popular Astronomy", Volume 20 (1912), "the little holes at ε and H served as a "finder."" This is a pretty simple system, using small holes, aligned up with the top of the assembly. Very clever, and definitely present. - RL)

Chasing Galileo's Sunspots

After doing the animation in the previous post, I found myself struck by the amount of detail Galileo put into his drawings, and how they compare to modern observations. His contentious contemporary, Christoph Scheiner, came up with not only better equipment for solar observations (including what can only be described as one of the first equatorial mounts), he also developed methods that would be used for more than a century, and which in evolved form still exists, but Galileo's drawings still look better. The information supplied from the Galileo project at Rice University's website indicate that the drawings that Galileo did of the Sun were around 150-152mm  123 - 125mm in diameter, about  6 " 5". We can only guess which telescope he used (he may have even used one purpose built), but it is certain that it was a Galilean in optical design.

The question, however, is what method did he use? We know that he used solar projection, but what did his setup look like? Here, things become vague. How did he aim the telescope? There are plenty of questions that remain about how he did it.

A few years back, I built a facsimile of one of Galileo's telescopes, and in theory it would be fine for this little experiment in historical astronomy. Instead, I am using the one modern telescope that is most like a Galilean in performance, a nearly fifty year old Tasco 40mm terrestrial telescope. As an astronomical instrument, it is extremely limited. In fact, as a terrestrial telescope it is extremely limited as well, possessing a narrow field and a somewhat dark field of view. That performance is very close to the performance of my long tube Galilean facsimile, in a shorter, easier to handle telescope.

Over the next few days and weeks, I will test out these methods using that old instrument and will, as always, share the results here.
(Edit - The diameters that were initially listed were incorrect; they have been corrected. R.L.)

Galileo's Unintentional Sunspot Animation

In the late spring and early summer of 1613, Galileo Galilei conducted a series of observations of the Sun. At the time, the study of sunspots was still obviously very young. Prior to the telescope, sunspots could be observed at sunrise or sunset (usually the latter), due to the strong filtering effects of the atmosphere at low angles. As the 17th century rolled along, the telescopic projection method of observing became the standard. It was Galileo's protege Benedetto Castelli who developed the method he used. From the 2nd of June through the 8th of July, 1612, Galileo made daily drawings from these observations, though a couple of days were missed (4th and 30th June). If you take the longest set, the 5th through the 29th of June, and arranged them in order, you get a crude animation showing the rotation of the Sun.

(I am not one to take credit where it isn't due. I would like to thank the Galileo Project at Rice University for the initial spark, primarily this page. I would also like to thank Professor Owen Gingerich of Harvard for providing valuable critiques of the work.)

First First Light

Lest anyone think that is a current star chart, let me assure, it isn't.

This is a chart generated from Night Vision for Java (a nice free planetarium

program), and if you look close enough, you'll see a date - 18th June,

1981 (1981/6/18, above the chart). It was on this night that I used my

first telescope, an older Tasco 50mm. It was a great little telescope that

had a pathetic little table top tripod. While I chose to keep the table

top tripod, I re-purposed a Woolco store brand tripod to take the

telescope as needed. That sky you see up there is what awaited me my first

night out with it, and as it turned out, its first light.

For my very first observation session, I set up in my front yard in the

Sandalwood neighborhood of Jacksonville. While we still had light

pollution, as well as the sweeping beacon from nearby Craig Airport, it

was not nearly as bad as it is now. You'll notice that two planets are

fairly close together, Saturn and Jupiter. That night, it was Saturn that

I chose for my primary target, the very first object to be observed. I

would sweep to Jupiter moments later, but once I got the focus on my

little Tasco set, the image of a small, elongated, yellow Saturn set my

heart racing. I do not remember what eyepiece I used initially. I think I

used Dr. Mike Reynold's advice and used my 20mm to locate the object and

then zooming in with the smaller eyepiece, what I think was a 6mm, with

horrible eye relief. Still, there was Saturn, clearly discernible, clearly

ringed, clearly Saturn.

While Saturn may be my favorite planet, I wasn't prepared for Jupiter.

With the smaller, higher power eyepiece in place, it was remarkable. There

it was, the somewhat flattened sphere that we all know and love, with the

Galilean satellites hovering close by. Now my pulse was racing.

As the months went by, I performed many sweeps with that little

instrument. The telescope lasted until at least 1989, when I took it apart

for cleaning and did damage to the objective lens.

The fact that I was able to see so many deep sky objects, as well as

Saturn and Jupiter, with such a small telescope blew me away. What's true

that many of those early astronomers had telescopes that weren't even the

equal of this modest little instrument, and they went on to define the

science so well, to lay the necessary groundwork that future generations

would work from.

Within the amateur astronomy community, you will frequently encounter

people of all sorts, and a good many of them will give you advice like

"stay away from department store telescopes." Those are wise words, but I

also think a bit hasty. Some of those department store telescopes can turn

out to be fine little instruments, if you understand their limitations.

On that summer night, so long ago, my little telescope didn't seem to have

any.
(Edit - the date of my first light is wrong in this entry. It was a Sunday night, and my journal indicates it was 14 June, 1981. The wonder was there, nonetheless. - RL)

This is why you should never do solar astronomy when you're sick.

This is why you should never do solar astronomy when you're sick.

Just A Shot Of The Moon (Or Perhaps Two)

Just some shots of the Moon taken with my Mavica through my Galileoscope.
Not bad for an older camera and a simple afocal setup. First image was
taken on 13th May, 2013, the second the following night.

Some Thoughts on Solar Observing

After my experiments yesterday with my Galileoscope and solar observing, I
find myself thinking more about ways to observe the Sun. The damage to the
inner face of the eyepiece was a visible reminder of the hazards where
amateur solar astronomy is concerned.
Back on the 7th of March1970, I had my first opportunity to observe an eclipse, one that
passed, partially, over Jacksonville, Florida. I was in first grade at the
time, and unlike most of my classmates, I was pretty handy with making
things. They presented instructions to the older children on how to make a
pinhole solar eclipse viewer. My memory gets a little foggy here, but I
also believe that these were available at some of the local stores.
Suffice to say, I managed to make one, but the weather locally did not
cooperate, and soon it became somewhat overcast.
For a few days afterward, though, I used that little viewer to view the
Sun. A few years later, in fifth grade, I found an astronomy book at our
school's annual book fair, and naturally picked it up for something like
$1.98. I was so pleased with it, and one of the first experiments in it
was making a bigger pinhole viewer, one that separated the two pieces by
ten feet or more.
Before I attempted that viewer, the book disappeared from our house. Not
really sure what happened, but I do know that it really upset me.
As time progressed, other ways to view the Sun presented themselves. The
most common seemed to be projecting the image through a telescope and onto
a screen. Prior to my obtaining my first solar filter, that was always the
preferred method.
Still, the idea of viewing the Sun via pinhole projection has fascinated
me. I had the chance to play with the technique again during the 1991
eclipse, which again was a partial one for us here in Jacksonville. The
Museum of Science and History set up booths where visitors could make a
two paperplate version, using aluminum foil to make the pinhole section in
the center of the upper plate. Very simple, but as with other design from
many years earlier, the only real detail visible would be that of the Moon
as it passed in front of the Sun.
Some may be familiar with something called "pinhole photography". This is
a long exposure technique that can produce some beautiful, long depth of
field images. The times necessary to obtain images can be very great, but
if care is taken, wonderfully detailed images can be obtained.
So the question is, what level of detail can be obtained by a long length
pinhole setup, akin to the one from my fifth grade astronomy book?
This is something I am apt to try.
Soon.

The Galileoscope As A Solar Observation Instrument

One of my favorite telescopes from an experimenter's standpoint is my Galileoscope. It has been used with my various video astronomy cameras, my Meade Lunar and Planetary Imager, afocal photography, and of course traditional astronomy. I've been looking at ways to use it for solar work, which is tricky, and of course somewhat risky.

(Warning - looking at the Sun with any astronomical instrument, without the proper filters and tools, is dangerous, period. Not only is it dangerous to your eyes, it is also potentially damaging to your instrument, as we will soon discover)

It was actually Galileo himself who made some of the first solar studies, and used his telescopes in this extensively, primarily through lens projection. These observations were almost always made with the Sun low on the horizon, either at sunrise or set. Contrary to legend, these are not what led to his eventual blindness.

I already have a homemade solar filter that fits the end cap of the Galileoscope perfectly, however due to the straight through nature of the telescope, it is somewhat risky to use, primarily because once you move your eyes away from the eyepiece, you are looking straight down the telescope, and at the Sun itself. What is needed is a shield.

I made a shield from a 10" x 10" (250mm x 250mm) cardboard. In the center of this square, I cut a 2 1/4" (56mm) circular hole that allows the shield to fit smoothly over the back of the Galileoscope dew cap. It should fit flush against the back of the dew cap extension.

Initially setup, it worked great with my solar filter; I normally use a neutral density filter as well, and this fits over the eyepiece.

Here we see it with an afocal setup, which sadly did not work, primarily because the camera has a hard time with focus (wanting to focus on the eyepiece or the shield; you cannot disable the auto-focus on some models). Aiming the telescope proved a little tricky, but was not too difficult.

But what about solar projection?

This is where caution is needed. Even with the Sun at a 30° angle above the western horizon (a point where its energy is cut almost in half), the amount of sunlight coming down is more than enough to damage the inside of the telescope, and especially the eyepiece. The lenses weren't damaged, but the internal face of the eyepiece was.

Still, it worked. I used a circular plastic to-go food container as my screen

One thing I'd recommend, however, is to move the screen back. Optimally, using the 20mm (Plossl) eyepiece, I'd recommend between 12" to 14" (300mm to 350mm) distance from the eyepiece to the screen.

At 8" (200mm); the image is small but bright.

At 12" (300mm), the brightness drops, but contrast improves, allowing for more details.

Using this technique, you can clearly see sunspots. 

The sunspots

Based upon my experiences today, I'd recommend the following to anyone who wants to do solar projection with the Galileoscope - 

• Use another 20mm eyepiece, one that uses metal in its construction. This should prevent the sort of damage we witnessed to our Plossl.
• To help in aiming the telescope, a hole might be cut in the shield that lines up with the sights. This hole should be no more than 1/4" (6mm) in diameter. Try not to look directly into the hole, instead look to see if the sunlight that comes through it projects over the sights and onto, say, the screen or even your hand. 
• Try to focus the telescope before aiming for the Sun. Find some very distant object and preset the focus, not only to simplify the operation but to make it safer for equipment.

As usual, I will share any additional findings and improvements I may make.

But remember, if you choose to try this, remember, again, be careful. And as always, have fun.

The Bucket Solution

One of the biggest challenges facing me whenever I'm doing a little stargazing is, well, my big tuckus. Hours at the telescope get tedious, and for us heavy, older guys, the legs start to ache. Add to that the fact that a few of my favorite telescopes sit low, and you can see how this can be a bother.

The solution is obvious; you need a seat. There are all sorts of folding chairs, and carrying them in your vehicle and unloading them where you plan to set up is easy enough. But what if you are not going to be viewing near where you park? Easy, right? Folding chairs or stools. Now, you've just added another item to carry. 

Let's consider. You are already carrying your telescope, its mount, eyepieces, other assorted odds and ends like repellent, gadgets (possibly a smart phone, tablet or e-reader), laser pointer. Now, we add in a portable seat of some sort. This is becoming a lot to lug. 

There are solutions, such as dollies and other devices with wheels. These aren't perfect either. If the soil is soft, it becomes even more tedious trying to move all of this stuff. 

What we need to do is reduce the number of items to a bare minimum and reduce the number of trips, preferably to one.

This solution might not apply to larger instruments, but for smaller and so called "backpack" telescopes it should suffice. 

The answer is the humble bucket. Five gallon sized.

My initial tests haven't been with one of those readily available buckets but with recycled cat litter buckets. 

The larger ones have a similar capacity to the five gallon bucket that anyone can pick up at the local hardware store. The bucket serves the dual purpose of being a container for lugging most of your stuff to the field and providing you a handy place to sit. You can use the bucket inverted to do just that, or you can buy special "lids" that turn a five gallon bucket into a stool. Or you can make your own; this is DIY astronomy at its finest!

My little experiment with the recycled cat litter buckets proved how easy a concept this is. For most back packer type instruments, two buckets should be the maximum, with one inverted bucket serving as the platform upon which the telescope could sit (they generally have a 10"/25cm diameter). The one that will serve as a stand can carry the cargo bucket, as they are normally designed to fit inside one another. For larger instruments, a single bucket would simply serve the humble task of reducing the number of trips needed to set up. 

Regardless, the bucket solution seems to me to be a great one, especially given my fondness for smaller telescopes. Give it a try.

As for me, just waiting for the next clear night. Anytime now. 

Anytime.

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.

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.

Enjoy.

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".