Coronado hydrogen alpha solar filters

More Information  · Supplied Accessories  · Recommended Accessories  · Related Products  · Images of Some Features Price $499.00 Shipping $14.95 List Price $599.00 Focal Length 400mm Focal Ratio f/10 Resolution 2.9 arc seconds Aperture 1.6" Shipping Weight 3 lbs. Warranty 5 years

The PST consists of a 400mm focal length 40mm aperture f/10 refractor with an integrated hydrogen alpha solar filter using a full aperture energy rejection filter and a 20mm clear aperture internal etalon. The scope’s achromatic doublet objective lens is fully multicoated. The filter has a <1.0 Ångstrom passband, centered on the 6562.8 Ångstrom H-Alpha line. The passband width gives balanced views of prominences and surface detail alike. The filter is thermally stable, so there is no drifting off the H-Alpha line as the filter heats up during use. The 5mm clear aperture of the blocking filter portion of H-alpha system (built into the diagonal housing) is ideally matched to the focal length of the telescope to give full disk views of the Sun.

The scope uses proprietary internal optical focusing (operated by the external focusing knob shown in the product feature image). The scope and focuser are a completely integrated unit, with no external moving or extending parts (focuser drawtubes, etc.) to gather dust or grit during windy daytime observing sessions. A rotary collar on the optical tube allows you to fine-tune the filter etalon for the sharpest and highest contrast image. Do not confuse this collar with the focusing knob on the rear of the right angle filter housing. The fine-tuning collar has a limited range of motion and can be damaged if you try to force it to turn in a vain attempt to focus the scope. A thread-in metal lens cover protects the objective lens of the PST.

You can use most 1.25” eyepieces with the PST. To get you started observing, a 20mm (20x) 1.25” Kellner comes as standard equipment. While optically acceptable, most observers eventually will want to replace this economy eyepiece with one of better quality. Either a 12mm (33x), 18mm (22x), or 25mm (16x) Coronado CEMAX eyepiece would be an excellent choice for observing, as they are optimized for high contrast solar viewing of subtle prominence and surface detail.

The PST includes an internal modified Coronado Sol Ranger Sun Finder to make it easy to center the Sun’s image in the eyepiece. You can see the Sol Ranger screen in the product feature image. An optional hard case is available to carry and store the PST. The case uses the snug-fitting die-cut foam that the PST ships in to hold the PST securely. A 1/4”-20 thread tripod adapter socket is built into the base of the filter/diagonal housing of the PST to allow mounting the 15” long x 2.1” wide x 3” high telescope on a photo tripod. You can also install the lightweight (3 lb) scope onto a piggyback camera adapter that’s mounted on a larger scope for motorized tracking.

Each PST has a “sweet spot” in its field of view where subtle prominences pop into clearer view and the larger prominences show more contrast and detail. Experimentally moving the telescope around so that the Sun’s limb and prominences move to different parts of the field will soon reveal where your particular scope’s “sweet spot” is located.

An often-asked question concerns the difference between the economical PST and the SolarMax 40 solar scope at better than three times the price. The most obvious differences are in the filter bandwidth and the clear aperture of the blocking filter. The SolarMax 40 has a passband of <0.7 Ångstrom, which provides the ideal balance between prominence and surface detail. Below 0.5 Ångstrom detail in prominences is less visible and the resolution and detail on the Sun’s surface is enhanced. At <1.0 Ångstrom, the passband of the PST, prominences are favored over surface detail although major surface details are still easily observable. If additional contrast is desired for observing subtle disk details (although at the expense of somewhat dimmer prominences), an optional SolarMax 40 filter can be mounted on the front cell of the PST, using a T-Max assembly (although the T-Max’s Doppler tilt function is not usable). Stacking filters in this fashion provides a narrower and higher contrast <0.6 Ångstrom passband to show even more subtle detail on the face of the Sun. The SolarMax 40 has a blocking filter with a 10mm aperture, while that of the PST is 5mm. The larger blocking filter aperture allows you to use a Barlow in front of the SolarMax 40’s blocking filter. This makes digital photography easier and allows the uses of a binoviewer with the SolarMax.

In addition, the SolarMax 40 uses an external 40mm full aperture <0.7 Ångstrom etalon that is mounted on the front objective of the telescope. It is supported by a T-MAX assembly that can be "tilted" off bandwidth to observe Doppler-shifted events. The objective itself is a special H-Alpha doublet lens designed by Dick Buchroeder (including optimized anti-ghosting). The PST, while it has a 40mm conventional doublet objective, has a smaller fixed internal 20mm <1.0 Å etalon. It has no capacity for Doppler shifting.

Another difference is in the focusing method. The SolarMax 40 uses a helical focuser that allows both visual observing and prime focus imaging. The focusing system of the PST is an internal mechanism that keeps the eyepiece in a fixed position. It is primarily for visual use, although you can do high magnification imaging with a suitable afocal set up.

To sum up the differences, you’ll see a better balance of prominence and disk detail with a SolarMax 40, will be able to use a binoviewer, and will be able to do prime focus digital camera photography, but you’ll spend over three times as much to see those improvements. The SolarMax 40 is the better solar scope. The PST is the better solar scope buy.