wpo - Coronado PST  fix by Maurice Gavin

my spectroscopymy main PST page ...Sketching H-alpha ...my Canon 300D DSLR ...BCF/Telescope House   Coronado homepage

Coronado H-alpha PST

A friend’s Coronado Personal Solar Telescope [PST] may have had a jolt that disturbed the vital etalon filter assembly for it no longer revealed hydrogen–alpha phenomena on the sun no matter how the tuner collar was adjusted but only a red image with sunspots like a white-light view.  Glauco Uri’s homepage   http://www.uriland.it/astronomia/articles/halfa/pst_eng.html hereby acknowledged shows the PST dissected.   My fix was less drastic - a side-by-side test afterwards showed comparable performance to my virgin PST above right.

Prior to returning the PST I tried a relatively unintrusive tweak and fix thus...The owner reports the PST works fine as before!
The rubber gaiter [covering the Philips screw] can be drawn forward towards the OG clear of the tuning collar [above right].  The Philips screw is removed and the tuning collar slid aside to expose the series of  thread holes in a recessed lower collar.
Rotate lower collar until H-alpha is tuned and reassemble with Philips screw central in the tuning arc.  Replace rubber gaiter.

There is thus no need, as described below, to unscrew the lens barrel and expose either the base unit interior or the rear etalon lens.  A Philips screwdriver will cut through the security tag avoiding its removal.   Work in a clean area and avoid any contact with the optics.  Clean surfaces of any oil smears on completion.


1] unscrew the lens barrel, complete with the tuning collar containing the etalon, from the base unit.
2] Expose a single Philips screwhead by rolling back the rubber gaiter over the etalon housing being sure to avoid touching the rear lens.
3] Screw the lens barrel back onto the base unit and mount PST on tripod to view sun.

3a] Remove the security tag over the Philips screwhead with the finger nails.

4] Remove the 12mm screw and slide aside the tuning collar to expose a series of threaded holes in a 90 degree recessed arc.

5] Mark the hole that the screw came from for reference.

6] Replace the screw into a hole two or three removed from the reference hole.

7] Turn the tuning collar the full range via the screwhead until the H-alpha features come into view in the eyepiece.

8] If no improvement repeat 7 above by moving the screw even further from the reference hole.  Note: I had to use a hole 5 removed [anti-clockwise viewed from OG end] from the reference hole to get H-alpha viewing central in the tuning arc.

8a] Replace tuning collar and secure the Philips screw in the new selected position [eg reverse of item 4 above].

9] Remove lens barrel, replace rubber gaiter over tuning collar and replace lens barrel in base unit.   Job complete!

images/text copyright - Maurice Gavin aka Nytecam - June 2006  206 16/06/06 - revised not added