Coronado PST (2005)

40mm Hydrogen Alpha Solar Scope

Coronado PST

The Coronado PST is a great solar scope. The views of the sun are amazing.  The bigger, tighter H-alpha filters and scopes do show even more detail, but cost a whole lot more. 

As with any solar viewing, time and effort are needed to learn how to properly use it and to train your eye to see the maximum amount of detail. 
PST Front
Front of Scope

PST Collar
Adjustment Collar

PST Focus

PST Mounting holes

PST Finder
Eyepiece & Finder


Aperture - 40mm
Focal Length - 400mm
F/Ratio - f/10
Bandwidth - <1.0
Thermal Stability - 0.005 /C
Safety Blocking - >10-5 from EUV/IR
Eyepiece - 20mm Kellner


Hard case
MALTA table top tripod
Coronado CEMAX eyepieces


Body - machined out of a single aluminum block.  A panel is removable on the left side of the body to should you ever need to get into the mechanics of the scope.

Tube - anodized aluminum.

Front Element - an aluminum cell appears to hold a thin, clear lens covering the highly reflective rejection filter.  You can add a SolarMax 40 to the front of the element to tighten the bandwidth to <0.6.

H-alpha Filter - an internal filter is used.  It is tuneable through 130 degrees of rotation using the external adjustment collar.

Focus - a knob moves an internal prism to achieve focus.  While it is a simple and reliable system, it really restricts the focus range.  Many eyepieces will not come to focus. 

Finder - "Sol Ranger"  - a small pinhole in the front of the scope body admits the sunlight.  An angled mirror reflects the Sun's image to the top of the body.  When the scope is aimed at the Sun, the Sun's image appears in a small, opaque window in front of the eyepiece.  Super simple and it works very well. 

Eyepiece Tube - nonadjustable aluminum tube threaded into the top of the body.  A single nylon setscrew secures the eyepiece.


There are  a pair of 1/4 x 20 mounting holes on the bottom of the body.   These are not near the center of balance so the scope is quite nose heavy in use.  A photo tripod works fairly well, just be aware of the nose heaviness when you loosen the locks.  I prefer to use an equatorial mount so I am not having to continually chase the Sun.

To aim the scope at the Sun move the scope around until you have the smallest shadow on the ground, this normally puts it close enough to see the Sun in the finder.  A little nudging centers the Sun in the finder and it will be fairly close to centered in the eyepiece

Simpler eyepieces tend to show greater overall detail.  My 9mm Nagler Type I really shows the prominences, but makes most surface detail invisible.  Many of the more complex eyepieces I have tried could not come to focus due to the very limited mechanical focus range of the scope. 

After focusing on a section of the Sun turn the adjustment collar to fine-tune the filter for the best image.  You will notice that no single setting will show all details.  One setting will show nice surface detail, another will show the spots fairly well.  Another setting is required for prominences around the rim.  You will also find that most H-alpha filters have a "sweet spot".  Moving the object you are viewing into that spot will greatly enhance the details.

It is tough to image through, but I'm working on it.  Sometimes I get something usable, most of the time I don't.  The biggest issue is the range of brightness across the face of the Sun.  Expose to see edge details and the center is completely blown out.  Expose for the center and the edge fades to black.  I stack two or more images of different exposures, combined in Photoshop, to get near a constant exposure across the face.

The biggest improvement you can make to any solar scope is to block the sun from your vision. The light reflecting off of the surface of the eyepiece robs a lot of contrast. A hat is a big help, but I keep banging the scope with the brim and have to slide the hat back on my head to get to the eyepiece. Ive tried umbrellas, awnings, etc., to block the sun, but none worked real well.   A towel draped over my head and scope works best, but it gets real warm to stay under for very long.  Check out my solution: PST Sunshade (use your Back button to return here)

PST Shade   PST Shade

For more info: Coronado

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