The Scheiner Method, Revisited

My interests in the very early history of solar astronomy has been documented on these pages before. I wanted to explore some more, so I set out to replicate the early solar telescope designs of Christoph Scheiner. 

While many of his theories about cosmology were wrong (he was an ardent supporter of the geocentric model that the Catholic Church at the time held as dogma), and he was initially wrong about sunspots, he did produce the first practical solar telescope. 

He called it "machina helioscopica".

The design went through two iterations, as found in the pages of Scheiner's work "Rosa Ursina". The initial design simply had the helioscope supported by two legs.

Image from "Rosa Ursina", courtesy Wikipedia

Later, he improved the design, making in the process one of the first equatorial mounts.

Image from "Rosa Ursina", courtesy Wikipedia

Common to both is how the telescope and screen are joined in unison, a backbone of sorts. This technique is still in use to this day for solar studies, namely sunspot counts.

I set out to make an improved version over my experiments in 2013. This will ultimately lead to a permanent setup, akin to his later design. For now, the setup will be like his earlier design.

I used a piece of lumber, a 1"x4"x60" (25mm x 100mm x 1.524 meters) as the backbone. 

My initial setup was with cardboard, a proof of concept, to see how the entire design would work.

Two of my telescopes were used for this first test setup; my old Tasco 25x-50x 40mm zoom telescope-

And a Meade 40mm f/15-

Both telescopes worked well. There were concerns about the Tasco telescope, however. When first used, the images were a little dark. However, when used again, the images seem to work better, definitely more contrast. Incidentally, these images do not do these images justice.

Initial Tasco zoom telescope image, with levels adjusted.
This is how it appears to the eye.

The image processed a little further to bring out details.

The positions for all the components were worked out. 

For instance, I discovered that I needed the projection screen closer, as I planned to use a smaller one, for projection of a 100 to 125mm solar disk.

Once all of the positions were determined, work on the improved helioscope began in earnest. This mount would be designed to hold the telescope in two methods; either with a 1/4"-20 bolt, or a hose clamp. To make that mount, two 4" (100mm) "L" brackets were bolted together to form a "U" bracket. This bracket was then attached to the helioscope backbone with screws. Once in place, pieces of self adhesive foam rubber were attached to the mounting surface, to protect the telescopes. The hose clamp would also be likewise covered over most of its inner surface with the rubber foam, allowing space for adjustments.

For the forward mask, I used a piece of 18" x 14" (45cm x 35cm) Corroplast sign material, cut in half to make two 9" x 14" (22.5cm x 35cm) pieces. A 2" (50mm) opening was cut in the center of the mask. As designed, the helioscope will mount the Tasco perfectly. Once satisfied, the mask was attached with smaller "L" brackets.

Once the mask was in place, it was necessary to test the distances again to the projection screen. While the design was built around the Tasco zoom telescope, I felt it necessary to test the distance with other telescopes. To that end, the Galileoscope was used, sans its forward dew/glare shield. I was reticent to do so, knowing how the Galileo's 20mm Plossl was damaged the last time it was used for solar projection. While it didn't line up perfectly with the opening (it is a larger diameter), it did provide the necessary information.

For the projection screen, I chose a small clipboard. To mount it to the backbone, I used another 4"/100mm "L" bracket. While the bolt head does look like it would interfere, for the sized paper that will be used on this design, it really isn't a problem. With the clipboard mounted, the backbone was completed.

As luck would have it, when it came time to test the design, the weather turned fickle. However, initial tests with the Tasco telescope proved satisfactory.

The images it produced were again fairly sharp, especially when set to 40x magnification.

The problem is that the Tasco has a far more complex optic train than Scheiner would have used. It is a terrestrial telescope with a number of elements between the objective lens and the eyepiece. Scheiner would have used a Keplerian telescope with a very simple optic train, just two convex lenses, in fact. While I currently lack Keplerian eyepieces of the correct focal length, the Galileoscope with its 20mm Plossl is sufficient.

Eventually, this design will be setup with a permanent host telescope, no doubt on an equatorial similar to Scheiner's later design. In the meantime, I can use this setup for investigations into those early methods, which laid out the path that we follow to this day. 

In short, it worked. And still does. 

The Galileoscope Revisited - Doing More

The Galileoscope has been with us now for five years. Some in the amateur astronomy community have embraced the small 50mm telescope, while others still view it as an educational tool only, and only a mediocre telescope at best. Personally speaking, I sort of belong to both groups, having found that the telescope has plenty of use, but far from mediocre.

I have used my telescope for a number of projects, and have even extended its use. In that time, I have learned the following.

1. Other eyepieces - Since the Galileoscope uses the standard 1 1/4" diameter, other eyepieces can be used. Caveat: weight. Since the eyepieces are simply a friction fit, it is crucial to limit weight.

2. Diagonals - Not exactly. You can use a diagonal if you use a Barlow ahead of the diagonal. Again, the problem is weight. While I converted a commercial eyepiece by adding a 29mm plano concave lens, this isn't always practical. The Galileoscope could of course be modified by shortening it up, but this is probably more trouble than it is worth. Best avoided.

3. Barlows - Yes. The Galileoscope already comes with a simple Barlow, and other commercial units can be used. In the image, a small inexpensive (and lightweight) Meade 2x Barlow is being used. Again, the biggest problem is weight. 

4. Solar work - Certainly. While I caution users about problems with the projection method, others have reported success. My preferred method is with a solar filter. Baader film is inexpensive, and it is easy to build a solar filter. 

5. Tripod and other mounting systems - The Galileoscope works best as a straight through, traditional telescope. Depending upon what you plan on viewing, you could find yourself being contorted into some extremely odd angles. When it comes to tripods, the taller, the better with the Galileoscope. Using a chair to effectively sit under the telescope is recommended. A tripod will probably be the single most expensive purchase you could make in conjunction with this telescope. Certainly, there are probably other ways you could mount this telescope, depending upon how imaginative the user is.

There are still plenty of projects planned for my Galileoscope. As the top image shows, recently, it was used in alongside my main sunspot telescope, a Monolux 60mm f/7.5 I call "Bianca", and it performed flawlessly. Who knows, I may one day use it for a Messier hunt. As an experimenter's telescope, I believe that it is without peer for its small size.

The Celestron FirstScope Reevaluated

Being an advocate for smaller telescopes is sometimes a daunting task. I am as guilty as others when it comes to the aperture game. When I had larger aperture telescopes at my disposal, the smaller instruments just didn't seem up to the task. It took some retrospect to once more find utility in those smaller telescopes.

My definition of "small" is anything less than 200mm (8 inch) aperture. This means that the great bulk of amateur telescopes falls into that category; professionals have another definition for small, of course. "Smaller" is anything with less than a 152mm (6 inch) aperture. This is the realm of most beginner telescopes, including the nearly ubiquitous 60mm.

60mm has its limitations, of course, and some companies have endeavoured to create beginners telescopes of a larger aperture whilst keeping the price down.

Thus enters the 76mm Celestron FirstScope, and similar Orion FunScope.

My initial assessment of the FirstScope was perhaps a little flattering. It was the first telescope I had purchased new in some time, even if it was a bit  less than $50 USD. It was a design I like; in effect, a tabletop Dobsonian. It was cleverly designed and seemed sturdy enough. I looked forward to putting it to immediate use.

Which is what I did, after a cursory test of the optics. 

The one eyepiece I was certain was going to give me grief on the little telescope was the 4mm SR (which I wrote about not long ago). It was put aside. I did try the 20mm Huygens, and it performed well enough, I thought, but it too was to be put aside. Instead, the FirstScope was used with some of my better Kellners, an 18mm and 20mm. That has been the situation ever since, and I have been quite happy.

But that is not an honest assesment of the telescope out of the box.

After reading a few more reviews for the FirstScope, most of which agreed with my findings, though a couple were particularly critical, I decided it was time to reevaluate the little scope with both of its original eyepieces, and then with some of the least expensive commercial eyepieces available.

I should stress that my FirstScope still lacks a finder. For the low magnification that it is used at, it is easier to look down the tube and use a lower power eyepiece to help locate the target.

However, the first test was with the 4mm (actually 5mm) SR. As expected, poor. It was extremely difficult to focus. Even with an inexpenive Meade 2x Barlow (the kind one finds in their smaller telescopes), "forcing" a longer focal length, it was still difficult, even for an object like the Moon. That eyepiece is best with longer focal length telescopes.

The 20mm H was better (not really that hard, considering), but had distortion near the edges. No surprise again; I've used this eyepiece with my longer focal length refractors and it works better, though still with a narrower field of view. With the 2x Barlow, it performed slightly better, though only slightly.

My next eyepieces are typically found in some of Meade's smaller telescopes, starting with the Meade 17.5mm MA (Modified Achromat). This eyepiece performed far better than expected. The field was much better, though a little distortion persisted again towards the edge. With the Barlow, that distortion was even less. Color was good as well. 

The final eyepiece was a Meade 20mm Kellner. This performed well, though I thought it possessed more edge distortion than the MA. This was alleviated somewhat with the Barlow.

Conclusion - 

What did I learn from this? 

For one, the FirstScope performs better with better eyepieces, bottom line. While Celestron included two eyepieces that would normally be found in their inexpensive 60mm telescopes, they were not suited for this telescope. As some of the others have observed, I could not recommend the accessory kit for the FirstScope as well. The money spent for that would be far better spent on obtaining better eyepieces. The other option would be to buy the almost identical Orion FunScope. According to reviews, it includes a couple of three element eyepieces that are far better performers. Also included in the price is a red dot finder, which is a far better choice for this design. In the end, however, I maintain that this little telescope is a fine performer, as long as its limitations are understood.

The SR Eyepiece Reconsidered

The SR eyepieces for this comparison.
Left to right, the Meade tall .965" 4mm "SR", the Meade
.965" short 4mm SR, and the Celestron 1 1/4":4mm (5mm) SR.

Recently, I came across a rather harsh thorough review of the Celestron FirstScope 76mm table top Newtonian. While I did not necessarily agree with all of the author's findings, one item stood out; he rated the 4mm SR included in the telescope rather highly. 

SR eyepieces have not been generally appreciated in my experience. They have very poor eye relief, the images are frequently dark and murky, the view is narrow. Most of my SR eyepieces have ended up either in the spares box or the parts bin. To be honest, based upon my experience with smaller SR eyepieces, I simply did a cursory test of the Celestron 4mm model, and it too ended up in spares.

Perhaps I should have tried it again. Most of my astronomy has been solar, deep sky (clusters primarily), and lunar, with a smattering of planetary work. I tend to use optically friendlier eyepieces, in my case a number of Kellners and a Plossl or two. Higher magnifications have seldom been used. The SR eyepieces have been there if I needed them. I seldom have.

Let us look for a moment at what an SR eyepiece technically is. I've come across several definitions for "SR"; "symmetrical Ramsden", "super Ramsden", "achromatic Ramsden", and simply "symmetrical". The classic Ramsden design consists of two plano convex lenses. For the unfamiliar, plano convex are flat on one side, convex on the other. In the Ramsden design, the flat sides face "out", with the field lens (forward) larger in diameter and with a longer focal length than the eye lens (rear), with a space between them. There is a specific formula for this, but for now we'll simply deal with the design's geometry. 

As it turns out, while most of those definitions are probably incorrect; they are certainly "symmetrical" in some sense, but have very little else in common with the "Ramsden" design aside from having two elements. 

To that end, I decided to take apart each of my SR eyepieces to study their construction. By the way, this is not something I recommend doing. It is very easy to to get dust on the lenses, and when dealing with such small focal lengths the result is dreadful.

The 1 1/4" Celestron 4mm SR, which actually yields a focal length closer to 5mm (as initially confirmed in the linked article), appears to have two symmetrical convex lenses of similar diameter.

The field lens looks identical to the eye lens, but may have a slightly longer focal length. Beyond that, this eyepiece has more in common with what was once called the continental variant of the even older Huygens eyepiece Both lenses are double convex. The only exception is how similar the lenses are to one another. 

How then does the 1 1/4" Celestron 4mm (5mm) SR compare in design to a smaller .965" version?

Currently I have two that are still intact and in use, and both were imported by Meade at various times. Externally, they look different, with one being longer.

I decided to open the shorter one up first. Again, I was greeted with two lenses, but much smaller in diameter than those found in the newer Celestron 1 1/4" design. They can only be described as tiny, around 3.5mm in diameter a piece. Like the Celestron lenses, both were double convex, and again the field lens apparently had a slightly longer focal length. But again, they were extremely small. This will explain much, as you will read later.

How about the taller .965" Meade 4mm SR? One thing that stands out immediately is the diameter of the field lens opening. It is close to twice the diameter of the one found on the smaller SR. In construction, however, there is a big difference. When opened, there is another lens.

Ahead of the field lens is a double concave. In effect, this forward lens serves as a built in Barlow, increasing the magnification. Otherwise, the construction of this SR is almost the same, though using larger lenses than the ones found in the shorter .965" SR. The spacing between the field and eye lense, however, is rather close, being more akin to simplified symmetrical eyepiece.

Optically, how do they compare?

For the test, I used my 60mm f/7.5 refractor "Bianca" and chose the top of a nearby pine as a target. 

As expected, the Celestron model provided a nice, bright image that was fairly crisp, though typical with the design the eye relief was a little poor. The shorter Meade SR, with its small lenses, had a narrower view and poorer eye relief. The view was adequate, with a slight discoloration at the edges. For stellar work, this is fine, provided the target is centered.

I was not quite sure how the taller faux SR would compare, as I had never really used it. I expected it to be somewhat darker, as smaller, simpler Barlow lenses tend to produce that. Not surprisingly, it was indeed darker and narrower than the Celestron version, though the eye relief was better. It makes one wonder how would this eyepiece behave without the Barlow? Would it create an 8mm eyepiece of some sort?

This little test proved that sometimes judging an eyepiece by its designation is tricky. SR eyepieces, regardless of what SR really means, are a mixed bag. The newer, cheaper, smaller .965" are iffy at best, while the larger 1 1/4" Celestron model is a fairly decent performer. The only real test is with the individual. The older .965" standard is fading, and chances are likely that the only time you'll encounter them is on older equipment, or very inexpensive equipment. It is probably best to err on the side of caution and go with the better performer. In this case, that would be the Celestron. Just remember, it is closer to 5mm than 4mm.

Solar Astronomy, My Way

Bianca, my current choice for observing the Sun

In this digital age, we have become perhaps too reliant on things being available to us in an instant. I'm as guilty as anyone else in that regard; I have scanners and digital cameras and all sorts of image processing software, as well as specialized (albeit lower tech) video gear for my telescopes. 

Yet here I am, everyday before noon if possible, setting up my old 60mm, 450mm FL telescope "Bianca", complete with solar filter and 9mm Kellner eyepiece, to study, and sketch, the Sun.

The business end. My old scratch built Baader film solar filter.

The goals here are multiple. Chief among them is the simple task of improving my observation skills. When you set out to draw something, you it pay a lot of attention. True, I can be remarkably fastidious when it comes to noting small details. Doing so when the subject is in the night sky, and being observed directly, is another matter entirely.

The other goal is to improve my ability to record the information. Currently, I have three astronomical journals. The first is for written record. The second and third are for the visual recording of observations, with the second being specifically for solar observations. 

This is my so called "Green Book".

All of my journals are simple composition books, but numbers two and three are graph ruled, 5mm to the square. I use an old COX (an office supply company from Taiwan) compass for drawing my solar disk, and have set a standard radius of 76mm (3 inches) inside the front. I also do my best to ensure that the circles are all set in the exact same position on each page.

I did say I could be fastidious.

After each observation, I compare my data to the information at SpaceWeather.com. This is to double check on my alignment and number of spots observed. I miss some, make no mistake, but keep my observations true; no corrections are made.

Since early April, I have been keeping a steady log of the Sun. To date (15th June, 2014), I have recorded forty four complete observations. I hope to fill this journal by year's end, weather permitting.

Again, this isn't to say that using digital methods is bad and that I am a Luddite of sorts. Far from it. The idea here is to improve my ability as an observer. When it comes to astronomy, that is something we should all strive for.

Just A Little Note About Eyepieces

There's no substituting good eyepieces.

Aside from being a somewhat awkwardly phrased sentence, it is an utter truth. At a minimum, you need three eyepieces for any telescope. Years of practice, experience, and standing on the shoulders of giants has taught me that.

Traditionally, and for a very long time, most telescopes came with Huygenian eyepieces. These simple, two element eyepieces are just okay, and not much better. Their biggest problem is eye relief, making viewing through them a less than desirable experience. I use them, to be honest, but I don't really recommend them. The lowest quality eyepiece I recommend is a Kellner. Think of this as an evolved Huygenian eyepiece with better eye relief and a much better field of view. Next up the ladder, and still very affordable, are Plossls. From there, you start to climb somewhat in expense and complexity, almost always corresponding with better viewing.

Yet I still use cheap eyepieces and accessories. Why?

I don't know, perhaps I'm lazy.

Here I am, in Charlotte Hall, Maryland, and the one eyepiece I choose to bring is a 9mm Kellner. This isn't so bad, but I've chosen to couple it with an inexpensive 2x Barlow, one that appears to be a single element, a lone plano-concave lens.

And it is not quite okay.

For stellar work, it seems to be okay, though just slightly. However, for planetary work (and right now, the evening sky is blessed with three planets to choose from), it fails miserably, at least in combination with my old Monolux 60mm F7.5 "Bianca".

The lesson here?

I have a much better Orion 2x Barlow. Use it.

Live and learn.

After all, there is no substituting good eyepieces.

The Blood Red Moon & The Tetrad

The total lunar eclipse of 20-21 February, 2008,
as seen from one of my CCTV cameras.
The Moon is just entering the umbra. 

Before the sun rises on Tuesday, the 15th of April, 2014, the Moon will have gone through the first of four total lunar eclipses that will be visible from the Americas. There is a lot of confusion arising from this, apparently, and some misinformation floating about.

After all, it's not like total lunar eclipses are very rare events. But first, let's talk about the actual eclipse itself. 

For those of us on the east coast, the eclipse begins at 1:20 AM EDT, according to the folks at "Sky &; Telescope". Other sources list this time as closer to 2:00 AM EDT. Regardless, this is the penumbra portion of the eclipse, and for the most part is barely noticeable. The Moon really begins to darken at 1:58 AM EDT; this is the beginning of the real eclipse. Slowly, the Moon will continue to move eastward in our sky (contrary to the direction the sky's moving, in fact, and with the Earth's rotation), until 3:47 AM EDT, when it will be mid-eclipse, deep within the umbra portion of the Earth's shadow. But it is not going to be dead center in our shadow; it will be off and towards the south. This should be manifest in a southern section of the lunar disk that is brighter, the variable being cloud cover on our planet, which effects the light that shines around the edge of our planet. This light is being lensed through our atmosphere. If the Earth did not have an atmosphere, a lunar eclipse would in fact be total as long as it passed through the Earth umbra. 

The total portion of the eclipse ends at 4:25 AM EDT, as the Moon begins exiting the umbra portion of the Earth's shadow and begins getting brighter. The final partial portion of the eclipse ends for us here on the east coast at 5:33 AM EDT (earlier for us here in New England; due to the fact that we are further east, the Moon will be setting, and the Sun rising, of course). For our friends just a little further west, the entire eclipse will be visible. For the most part, though, both North and South America will see a total eclipse, for again as I mentioned, the penumbra eclipse really isn't that noticeable.

Now on to the bad information that's floating around.

Eclipse visibility chart from the
Wikipedia entry for the 15th April 2014 lunar eclipse.
(Image couresy Wikipedia)

First, unlike a solar eclipse, it doesn't matter where you are during a lunar eclipse. From Boston, you will see the same part of the eclipse as Buenos Aires. This is because we are looking at the shadow being cast, not from it. 

Second, there is no guarantee that the Moon will turn just "blood red". There is a good chance that it will, but remember what I mentioned up there; the real variable is going to be cloud cover around the Earth's atmosphere. The more clouds, the more likely it will be darker. The fewer, the brighter. In short, it could go from blood red to dark chocolate. 

Finally, there is much ado about this eclipse and the "tetrad" that it marks the beginning of. A "tetrad" in this case refers to a series of four lunar eclipses spaces at six month intervals. Usually, it is not uncommon for there to be three lunar eclipses over a one year period. This tends to be the most common pattern, a "triple". Tetrads are not as rare as it would seem, in fact. The last tetrad occurred in 2003-2004 (not quite eleven years ago). What's unusual about this tetrad is that it will be visible from the Americas. 

So, what does this mean?

Nothing.

Absolutely nothing.

There are people who are desperately looking for some sort of meaning in this, yet in reality one does not exist. Have historic events occurred near or around these events? Certainly; after all, really triples, tetrads and just good old lunar eclipses are not that uncommon. As one of my high school teachers used to say "correlation does not equal causation". In other words, they are coincidences, and nothing more. We seek answers, we look for them hard enough and think we see patterns. It is our desire to find those patterns that actually produces them. 

If you get a chance, try and stay up late to catch this wondrous event. For my friends further west, you won't need to stay up nearly so late. For us here in the east, it looks like an all nighter.

And sadly, it's looking increasingly like a no-go here in Connecticut. Clouds are rolling in, and the rain is coming. 

We'll see.

Solar "Reflections", Part 2

As the warmer weather gets underway here in New England, I turn my attention to more things astronomical. For the first time in weeks, I no longer fear being exposed to bitter cold. While there may be plenty to do at night, I have turned my attention to solar astronomy. 

As mentioned on my entry for the 1st of this month ("Solar "Reflections""), I decided to play with an alternate method of viewing the Sun, and the initial results showed promise. One thing I failed to mention with regards to these recent attempts is that on the 29th of January of this year, there was an chance alignment that produced a solar image on the wall between the foyer and the half bathroom. It wasn't the sharpest of images, but was clearly the Sun.

I decided to make a "screen" (a cardboard box top) to see what type of image could be gleaned. 

It turned out the the source was light coming through the kitchen window and passing between the freezer and refrigerator doors and handles. 

It wasn't much of a pinhole, but it was just enough to produce an image. It was just sharp enough for me to make a simple animation of the Sun heading down.

Now on to the current work.

After my initial foray into pinpoint reflection this month I decided to try again, but this time setting going even further. Additionally, I made a dedicated solar filter and Hartmann mask for my Celestron FirstScope, and have been undertaking a series of observations with that as well. But I wanted to see to what limits pinpoint reflection could be taken. 

As I had already set up for my daily solar session, I felt that it was also the best time to try for a projection into the house. With the Sun at such a high angle, it was guaranteed to be much brighter, and therefore able to provide that much more contrast. It was almost 13:00 EDT, and the Sun rode high.

I chose to set up, as I had before, on the back porch, taking advantage of the recently unpacked table to mount the pinpoint mirror. As I mentioned in the previous piece, this is a small fragment of a first surface mirror, but what is important to note is the size; not quite 5 mm square. In my first attempts back in the autumn of 2013, I had reduced that area to a point 3 mm in diameter. Since then, the paint has come off. While we may have lost some detail, we gained contrast. 

I set up my drawing pad and easel on the dining room table. Total distance between the mirror and the paper was perhaps 9 meters (30 feet). The resulting image was around 125 mm (5 inches), but a measurement wasn't taken. The solar disk showed, but didn't provide enough detail.

For my second attempt, I slowed my camera's shutter speed. This allowed for a little more contrast. Something began to show up. The third attempt was pretty much the same.

It was at this point that I decided that what was really needed was more distance between the mirror and the screen. I chose to go another 2.4 meters (8 feet). This resulted in the easel being set up straddling the kitchen sink. Here, the details started to become a little clearer. Sunspots were beginning to become visible. 

After adjusting the the image's contrast and light levels, the sunspots in the Sun's northern hemisphere became very visible. The small group coming around the Sun's western limb was even there, albeit faintly. 

North is to the left in the projected images.

Compare this to the official Space Weather image for today.

By this time, high altitude clouds began making rolling in, so I put away my gear and waited. 

At a few minutes before 16:00 EDT, I decided to go even further afield, this time into the yard beyond the porch.

My "screen" was taped to the wall in the living room. Overall distance was now about 18 meters (60 feet). The projected image was around 200 mm (8 inches). There were still some high altitude clouds, but not as bad. Not surprisingly, some work with the image still needed to be done. While some of the contrast was lost, after the image was worked, the sunspots once again showed very clearly. They were, however, noticeable to the naked eye.

Perhaps what is really needed is a lot of distance and a very dark room into which the image is projected. No doubt larger sunspots would show even better. 

Still, I think we can call this little experiment a success. If anything, it was fun.

Solar "Reflections"

1st April, 2014. 

Today was the first really nice day we've had since November. The temperatures weren't terribly high still, just 49° F (9° C), but in the sunlight, it feels so much better than the winter we've had. It was also remarkably clear today, with that wonderful Sun shining like mad up there in that sapphire sky.

In other words, it was a perfect day for solar astronomy and a little experimentation. 

Back in early fall of 2013, I took a small chunk of broken first surface mirror I had and attached it to a piece of cardboard, and played around with solar pinhole mirror projection. This is the opposite of regular pinhole projection, since there is no hole, instead just a very small reflective source. My test last year weren't perfect, but they showed that yes, a solar disk could be projected. The problem was that I was projecting the image onto a screen outside, where it was too bright. 

For today's experiment, I chose to cast the reflection into the condominium, and with much better results. 

The mirror and its base were taped onto the head of one of my tripods, in a manner that allowed it to be easily aimed (much like a camera, in fact). 

The tripod was then carried outside onto the back porch. It was shortly before noon, and the Sun was fast approaching the meridian. It took a little work to get it aimed. I chose a spot on the dining room wall, next to the large decorative clock that hangs there. This allowed for an image that was a little over 5" (125 mm) across). This was perhaps 25 feet (8 meters) from the mirror. 

It worked, though the resulting image was not as sharp as I would have liked. 

This is the trade off. You can choose sharpness over contrast, making the pinhole (or in this case the reflective surface) smaller. The resulting image would be darker, however. For today's experiment, I chose contrast over detail. 

Amazingly, after the images were pulled and processed, I was surprised to discover that the largest patch of sunspots on the main disk, group 2021, was faintly visible in the image. A little sharpening, and you can sort of pick them out. 

In this projection of the Sun, north is to the left.

The Sun, 1st April 2014, courtesy Spaceweather.com

Certainly, the method can be improved, but it is severely limited. You will never have the acuity that a lens system will provide. As a safer method for observing things like eclipses, transits and larger sunspots, this method should be sufficient.

I do wonder to what extreme it could be taken. Maybe that will be a "project" for the future.