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Coronado PST HA Solar Telescope


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I Need One of These!

The Coronado Personal Solar Telescope (PST) is a 40 mm (1.6 in) refractor designed for observing the sun. It contains an internal hydrogen-alpha filter. At $500, the PST has brought h-alpha observing within the realm of ordinary mortals. Before Coronado, most h-alpha systems were prohibitively expensive.
In this article, I will also explain how I came to purchase the PST. I will also describe the features of the PST and its performance.

I had looked through several h-alpha setups at various star parties, but I never seriously considered purchasing one until the PST came out. When I first saw the PST advertised on the Internet, I called my wife into the office and proclaimed my intention to buy one. She quickly shot the idea down, and she said that the scope was ugly. I reluctantly agreed, but I still wanted to get a one and was able to eventually. I purchased my PST from Orion Telescopes, and it took a little over two months to arrive. Considering the demand for this scope, I feel lucky.

The Longest Two Months

As I waited for the scope to be delivered, I had the opportunity to look through two PSTs at a star party. One of the scopes was unable to obtain a sharp focus, and the other was plagued with a swarm of ghost images. I wasn't impressed. I was tempted to cancel my order, but I reckoned that I should assess the scope on my own time.

My fears were unwarranted. The scope is wonderful. It is the coolest astronomy gadget that I own.

The PST's arrival was followed by the obligatory period of cloudy weather. After two days, I finally got to use the scope on a beautifully clear, autumn morning. I was able to see many large prominences interspersed around the edge of the sun. I could also see surface details such as dark filaments and areas of bright plage. I was excited by the quality of the views and felt as though Christmas and my birthday had arrived on the same day. I must have walked around all day with a silly grin on my face. Whenever I look through the scope, I feel like giving someone a high five.

My wife and father-in-law also looked through the scope, and they seemed impressed with the views. My wife asked, "What would it take to make the prominences look bigger?" I said, "Thousands of dollars." "Okay, never mind."

Observing at the Edge

The PST comes with a 12.5 mm Kellner eyepiece, and you achieve focus by rotating a small aluminum knob on the rear of the scope. The focuser action is smooth, and I have been able to focus all of my eyepieces.

The eyepiece holder is fixed atop the boxy rear end of the scope and features a plastic set screw. Other than the setscrew and lens cap, the scope is all metal and robust in construction.

The dedicated case that I purchased separately is constructed of vinyl-covered wood and features metal corners and fasteners. The foam insert from the shipping box fits into the case and holds the scope very tightly. I generally pull one end of the insert completely free of the case in order to remove the scope.


Caption: The PST and case:

One sun to go, please hold the photosphere...

I mount the PST to my Tele Vue Tele-Pod alt-azimuth mount. This setup is lightweight and stable. The PST balances easily. I use one of the threaded rods and knobs that came with my Tele Vue Pronto refractor to attach the PST to the Tele-Pod's cradle. This is infinitely easier than trying to insert a bolt through the cradle and into the scope's base. I have also attached the PST to my CG5 equatorial mount with the Tele Vue adapter that I use with my Pronto.

This bottom view of the PST shows the Tele Vue threaded rod and knob.

The aluminum focus knob is on the angled surface.The clever built in sun finder provides an easy and safe way to aim the scope. The finder projects a tiny solar disk onto the inner surface of a small frosted window imbedded within the top of the boxy rear end of the scope. To aim the scope, the user centers the solar disk in the frosted window.

The scope has a sweet spot located in the center of the eyepiece field. The sweet spot provides the best views of prominences and surface features. Details will appear and disappear as you slew the telescope back and forth through this area.

The scope features a tuner that you can use to obtain the best contrast in viewing either surface features or prominences. The tuner is located at the junction of the tube and boxy rear end of the scope and features a knurled rubber ring for easy gripping. The tuner moves easily and smoothly. It is fascinating to watch features appear and disappear while rotating the tuner. At its clockwise limit, the tuner erases most of the h-alpha detail and provides a view similar to that provided by a white light filter.

Using the tuner helps you to grasp just how tenuous this sort of observing is. What I mean is that the h-alpha details seem to be just at the edge of perception. Any slight deviation in the tuner or the scope's position will make the h-alpha view disappear. The sudden appearance of h-alpha detail while tuning seems rather magical. I feel privileged to be able see such things.

The PST's small blocking filter, which is located just below the eyepiece holder, vignettes the field in the lower power eyepieces that I generally use. Even with this restriction, the scope will deliver full disk views of the sun. The vignetting has not proved to be a great hindrance to my enjoyment of the scope.

The views through the scope are very sharp, and it is easy to find the correct focus. The focuser turns smoothly and precisely. I have been able to focus various Tele Vue Plossls, Naglers, a 24 mm Panoptic, and a 4 mm Radian.

The PST's dedicated 12.5 mm Kellner eyepiece provides 32x. Despite being a peephole eyepiece, it works really well with this scope. Since your daytime exit pupil is already constricted, the tiny viewing lens of the eyepiece doesn't matter and seems to enhance the view by reducing glare from the bright outdoors.

After using my other eyepieces with the PST, I found my 20 mm Tele Vue Plossl (20x) to be a good eyepiece to supplement the Kellner. I enjoy the lower power, full-disk view that the 20 mm Plossl provides. When I want to see more detail in the prominences, I use the 12.5 mm Kellner. I now leave the 20 mm Plossl in the case as a dedicated eyepiece. Both the Kellner and Plossl feature circular rubber eyecups, and these are very helpful when observing with the PST. I am able to center my eye within the shaded area provided by the eyecup. Although I have used a black cloth, I usually block the right side with my hand. A baseball cap is also very helpful in shielding the view.

The PST does have some ghost images. When using an alt-azimuth mount, I can see two overlapping disks of light that are confined to the lower left quadrant of the sun. Rotating the tuner does not affect their appearance. These ghost images are mild and do not detract from my enjoyment of the scope.

In person, the scope looks much better than it did in the original images that came out on the Internet. Now that I own one, I like the PST's appearance. I find the design to be elegant and pragmatic, and I think that the gold-anodized tube is particularly attractive. The scope is not nearly as boxy and cumbersome as I had originally thought.

The PST is a solidly built, integrated unit. Since the PST's filter is internal, I feel safe using the scope. I am usually apprehensive when using objective-mounted, white light solar filters.

"Disasters on the Sun"

Observing in h-alpha reminds me of the "disasters" phrase from Hamlet. When observing through the PST, I get the feeling that I am witnessing an angry red nuclear furnace. The sun in the PST is scary, dynamic, and awe-inspiring.

I have often observed the sun in white light using my Tele Vue Pronto and a Baader solar filter, and the views through this setup are sharp and beautiful. I enjoy the stately procession of sunspots across the sun's apparent disk or photosphere, and other white light features show up well. Despite this, the sun in white light has a static appearance that is not nearly as exciting as the h-alpha sun. In h-alpha, the sun appears different each day that you observe it.

Solar prominences, or "disasters on the sun," are diverse in appearance. In the short time that I have had the PST, I have seen prominences that resemble a line of bushes, vertical spikes, faint loops, and one huge prominence on October 22nd that resembled a great tree. On Thanksgiving Day, I saw a prominence that resembled a stubby cigar complete with a thin wisp of smoke. Some prominences are faint and ghostly, while others are bright and opaque. I have often seen detached prominences hovering above the solar rim.

I have found it remarkably easy to observe surface features. I was surprised at the amount of surface detail observable in the PST. From what I have read on the Internet, I wasn't expecting much of this to be visible.

The chromosphere, the red layer of gas just above the photosphere or apparent disk of the sun, is visible in the PST as a thin fringe around the edge of the solar disk. It often has an irregular, spiky appearance. When superimposed across the solar disk, the chromosphere is a chaotic witch's brew of swirling red gas. At first view, the intense red of the chromosphere tends to dazzle my eye, but after a moment, the fine details emerge. Under good seeing conditions, the chromosphere resembles an assembly of crisp waves frozen in time.

As I previously stated, the PST will reveal dark filaments in a wide range of sizes. These dark filaments resemble opaque, reddish-gray tubes that hover above the chromosphere. In reality, they are prominences seen from above instead of from the side. On Thanksgiving Day, I was able to see a remarkable filament that stretched across about one-third of the sun. Once I was able to watch a filament drift across the solar disk over a couple days. I noticed that the shape of the filament changed, and a smaller nearby filament disappeared. Occasionally, I have seen dark filaments that continue over the apparent edge of the sun and terminate in a prominence. Such views give the sun a very 3-D appearance.

The h-alpha view tends to minimize the appearance of sunspots. The penumbral areas disappear, and just the umbral cores remain visible. As I previously stated, you can obtain more traditional views of sunspots by rotating the tuner. Active regions of sunspots often display a turbulent blend of dark filaments and bright plage. The chromosphere near these active groups often has a curved appearance that resembles the magnetic field lines around a bar magnet. It is fascinating to be able to see these features in person.

Flares should be visible in the PST, but I haven't been able to observe any yet. It is late autumn in the Midwest, and the weather has been lousy. I am lucky if I get one PST session a week.

The PST operates best at low magnifications such as the 32x provided by the dedicated Kellner eyepiece, and the 20x provided by my 20 mm Tele Vue Plossl. Even at such low powers, the prominences and filaments visible in the scope display much detail. I don't consider the low powers to be a drawback. I enjoy wide-field viewing through telescopes, and I really like full-disk views of the moon and sun. Along with the full-disk views, another advantage of low magnifications is that the scope is somewhat immune to bad daytime seeing.

You Need One of These!

With the PST, Coronado has provided a small, portable, safe, and easy to use integrated system for observing the sun in hydrogen light. The Coronado PST is an optical and mechanical marvel that reveals the ephemeral and vibrant detail of the solar chromosphere. The introduction of the PST will open a new realm of observation for many amateur astronomers such as myself.

I have really been amazed at what the PST will reveal on the sun. The views through the scope are wonderful and fascinating. In the short time that I have owned one, the PST has brought new joy to my hobby. Also, it gives me something to do in the day and, as I said before, even my wife is impressed with the views.

I have no undisclosed interest in Coronado or any other vendor that I have mentioned in this article, and I have purchased my equipment via normal channels. All of the photographs that I have included in this article are my own property. I hope that this article has been helpful and informative. Please contact me at the above email address if you have any questions or comments

Advantages

* Inexpensive compared to other h-alpha systems
* Complete telescope with eyepiece
* All metal construction
* Portable, lightweight, and small
* Enclosed filter is safe to use
* Scope attaches to ordinary photo tripod
* Provides full-disk views of the sun
* Scope reveals prominences and surface details
* Tuner to dial in the best views
* Handy built in finder

Disadvantages

* Small aperture discourages high magnifications
* Plastic dust cover
* Minor ghost images
* Vignetting at low powers
* Case is sold separately
* Requires a separate mount




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