The Sun is an incredibly dynamic and active body that offers minute-to-minute changes, especially filaments and prominences, which can appear and sometimes disappear in the span of hours.
If you’re not interested in a dedicated solar telescope:
Every so often, with an inexpensive full-aperture film or a glass solar filter (white light) attached to the front of any of my regular telescopes (except my truss tube or collapsible telescopes), I do safely observe features such as sunspots, the sun’s grainy surface, and even eclipses.
But with a more expensive hydrogen-alpha telescope, I can look at solar flares and prominences in addition to the aforementioned features.
White Light, Hydrogen-Alpha, and Calcium-K Filters: Decide Which One You Want
White light solar filters are typically removable and attach to the front end of our telescopes. The entire visible light spectrum of the light hitting the filter is let past into the telescope objective, while the rest (including especially harmful UV rays) is reflected or absorbed. Depending on the exact material used in the filter, the sun may appear white, yellow, orange, or with a slight greenish or blueish tone.
White-light filters show the Sun’s photosphere, the Sun’s “surface”. So we’ll often see sunspots and the photosphere’s grainy surface. When there are no sunspots to be seen, I see the sun as essentially featureless, with nothing at all but a blank disk.
Hydrogen-alpha filters work a little differently, using a Fabry-Perot etalon and a dichroic blocking filter to filter the sun’s light down to a very narrow wavelength (1 angstrom or less). This also dims the image enough that less additional filtering is needed.
In dedicated solar telescopes, the etalon is located at the front with an additional blocking filter located inside the telescope or in the diagonal, while in the $1200 DayStar Quark Hydrogen Alpha eyepiece that I own, the etalon is located within the device. While using Quark, depending on what telescope I’m using it with, I may or may not need an energy reduction filter for additional filtering.
The Sun in Hydrogen-Alpha appears reddish, and it shows me the Sun’s chromosphere, the lower “atmosphere,” where solar prominences, filaments, plages, and spicules (a phenomenon in the Sun’s atmosphere) occur. I can still see granulation and sunspots, too.
These features can change by the hour, making H-Alpha solar astronomy an extremely entertaining “live” experience to me, albeit a pricey one.
Seldom seen but also available are Calcium-K filters, which work basically the same way as hydrogen-alpha filters do with an etalon.
They show more details in the chromosphere (mainly brighter and darker regions with sunspots) at the expense of not being able to reveal prominences/flares very well.
Some people also cannot see far enough into the deep blue/near-ultraviolet light that Calcium-K appears as, so you may also want to try viewing with one of these telescopes/filters first to make sure it works for you.
Why I Mostly Ignore The Aperture Spec In Solar Telescopes
As Sun is already blindingly bright and only being filtered down by our telescope, I don’t need the extra light-collecting area provided by a larger telescope. All the aperture does for me is increase resolution.
There’s a problem, though: atmospheric seeing or air turbulence.
Seeing is typically pretty bad during the daytime, and the area of sky around the sun is the worst. The result is that solar scopes above 4 to 6 inches or so have to resort to costly measures to eliminate the effects of bad seeing. Even imaging and stacking with cameras and computer software is limited in what it can compensate for.
This is the reason why we see most solar telescopes tend to be below five inches in aperture. Also, they’re almost all refractors so as to provide the highest contrast and resolution for the given aperture.
Solar Telescope Recommendations I Can Vouch For
I Personally Went for the Meade Coronado Personal Solar Telescope
My Choice Between $700-$900
The Coronado PST revolutionized solar observing when it was introduced in the early 2000s. Prior to the PST, H-alpha solar telescopes were extremely expensive affairs, only found in the hands of very wealthy and skilled amateurs or professional astronomers of that time.
As is generally true of most H-alpha scopes, a mount is not provided with the PST. But Meade sells lightweight, inexpensive alt-azimuth and equatorial mounts designed to match the aesthetics of the PST. The PST can be easily adapted to fit a Vixen dovetail plate and thus most mounts, which is what I did personally. You can also screw it directly to a photo tripod.
The PST comes with a single 18mm Plossl eyepiece, which works okay, but I often use couple of my other eyepieces as well.
The PST, in my experience, has only one major weakness: its focuser.
The PST focuses by moving a pentaprism, which keeps the eyepiece fixed and the scope compact, but it has limited travel. This means that many cameras and even certain eyepieces or eyepiece/Barlow combinations cannot reach focus. Otherwise, the PST is an absolutely great solar telescope at an affordable price.
Lunt LS50 is One Scope I Aspire For Based On My Short Usage
My Choice Between $900-$1300
Serious solar observing and solar imaging require 50mm of aperture, and the Lunt LS50 delivers on both.
It’s capable of high magnification (75-100x) and takes stunning solar images with even relatively inexpensive cameras. The scope’s tuning system is also far superior to the one I’ve spotted being supplied with the Coronado PST that I own.
My only complaint is the focuser.
By default, the LS50’s focuser is a nonrotating 1.25” helical. It’s usable and provides plenty of travel, though it’s not my favorite.
You can buy an aftermarket 1.25” Moonlite or FeatherTouch focuser which will easily attach to the scope. But keep in mind that either is several hundred dollars, which puts you close to the price of Lunt’s LS60, which comes with a built-in 2” dual-speed Crayford focuser.
The LS50 lacks a finder or mount.
The Tele-Vue Sol Searcher attaches right to the tube clamshell and is relatively inexpensive if you need a finder. I aimed the scope using its shadow on the ground and used to get dead-accurate pointing.
For mounting, you can attach the scope directly to a photo tripod or buy a Vixen dovetail plate and an equatorial or alt-azimuth mount; anything rated to hold at least ten pounds will do for visual or photography.
Lunt LS60 is Even Better than the LS50
My Choice Between $1300-$1600
The Lunt LS60 shares relatively little in common with its little brother.
Sporting a completely different internal tuning system and a GSO dual-speed 2” focuser (with an optional upgrade to a Feathertouch), I’ve always considered it to be far superior to the LS50 in form and function.
Like the LS50, the LS60 could use a finder like the Tele-Vue Sol Searcher.
It has a ¼ 20 hole on the bottom of the tube clamshell for attaching to a photo tripod. However, the LS60 operates at enough magnification and is hefty enough that I’d suggest you consider a quality astronomical alt-azimuth or equatorial mount with at least 10-15 pounds of weight capacity, which will also necessitate purchasing and attaching a Vixen dovetail to the LS60’s tube clamshell.
Meade Coronado 0.5PST has an extra etalon on the front, reducing its bandpass from 1 angstrom to 0.5 angstroms, as compared to my cheaper Coronado PST version. You can take off the extra etalon to revert it to a normal PST if need be.
While reduced bandpass offers more surface detail, the downsides are that the scope becomes less portable, significantly more expensive, and the images are dimmer.
For less money, you can get the Lunt LS50, which has a 0.7 angstrom bandpass—nearly as narrow—and more aperture. However, some people swear by double stacking and the slightly narrower bandpass, so it’s up to you to decide whether it’s worth your money or not.
Accessories That I Typically Use With My Solar Observation
Tele-Vue Sol Searcher
I usually line up my solar telescope with the Sun using its shadow. But if you’d like to save yourself some time and frustration, then there’s Tele-Vue’s Sol Searcher. It operates using similar principles to a pinhole camera and attaches to your scope via screws, or you can use Velcro or double-sided tape to install it.
Coronado Cemax Eyepieces & Barlow
These eyepieces and Barlow are designed specifically for solar use with special blackening, baffling, and solar-optimized coatings.
Sky-Watcher Star Adventurer Pro Mount
The Sky-Watcher Star Adventurer is not only a great mount for wide-field astrophotography with your DSLR, but it’s great for mounting any small telescope, including an H-alpha solar telescope. However, it does not come bundled with a tripod, so you’ll need to buy that separately–a heavy-duty photo tripod is best.
1. I’m surprised you don’t recommend buying a Baader white light filter for the telescope you likely already own, they’re under $50 and fit almost all sizes and designs.
2. The Coronado AZS Mount appears to be identical to the Meade Infinity refractor mount, and very similar to the Celestron “Heavy Duty” mount if you can’t the Coronado one.
3. What are your thoughts on the new Lunt 40mm? Seems to better than the PST and slightly cheaper too.
The Lunt 40mm is great, and yes the AZS mount is the same. This article is for dedicated solar scopes, not filters.
Sir, just curious to know, can solar eruptions affect MF/HF communications? Thank you. Respectfully, Ryan Namaka
Yes, they do all the time.