Tuesday, May 28, 2013

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.

Saturday, May 25, 2013

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)

Friday, May 24, 2013

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.)

Friday, May 17, 2013

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.)

Wednesday, May 15, 2013

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
(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.

Tuesday, May 14, 2013

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.

Monday, May 13, 2013

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.

Wednesday, May 01, 2013

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.