PST central obstruction?

Started by RLH, 08/24/2004 08:18PM
Posted 08/24/2004 08:18PM Opening Post
I have spent about four days with my new PST and have come up with a couple of questions. Any replies will be greatly appreciated.

1. The PST front objective looks different from any other Coronado example that I have had the pleasure to use. Does the PST have a central obstruction? Is this a new direction for Coronado or is the etalon hidden behind the objective and its dark coating?
2. Why does the 40mm filter (for stacking) cost twice as much as the PST?

I am happily shocked at the quality of the PST and its views. It seems to show more detail than a Helios 1 that has more aperture (70mm).

Also, I would like to comment that the Cemax 12mm eyepiece is noticeably better than my Nagler and Takahashi eyepieces IMO. My TMB eyepieces would not come to focus.

Russell

www.flickr.com/photos/61135315@N00/
Posted 08/24/2004 11:09PM #1
Russell,
I am waiting for a Cemax 12mm, but I do have the Cemax 18mm which I like quite a bit. However, I have been using an Orion Sirius 10mm plossl that has been blowing me away, hands down!
As far as a central obstruction, I can't see it, but if you have a 40mm EP, that would show it I would think.
Al

Alan Koff
Palm Beach Gardens, Florida 8)

XT10i & StarBlast 6 w/ VersaGo II Mount w/ Steel Legs
Oberwerk 15x70, 25x70
Siebert Optics 5.0,5.4 & 7.5 Starsplitters and 10,15 & 22.5 Ultras and 26 Performance
TMB Planetary II 3.2 & 4
Always shopping for more!



Xpert skier and spearfishing------>
Posted 08/25/2004 01:10AM #2
Russell:

The PST is similar in design to the MaxScope 70 - or Helios 1 in that the etalon is down inside the tube, between corrective lenses, instead of infront of the objective. This allows the etalon to be smaller - and less costly - than a full 40mm front mounted etalon would be. This also explains why a second, front mounted etalon for doublestacking is more expensive. Cost scales rather quickly with etalon size.

Although I can't say for sure, I'd assume the design is the same for the PST etalon as it is for other Coronado scopes so I bet it contains a central spacer.

I too was shocked at the performance of the PST - and I'm a 90mm filter owner. To me it shows that Coronado is always striving to improve on its designs as time goes by. The cost/performance of the PST blows me away. And how they did it for <$500!!!??? Hummm... maybe captured Alien technology is being used?

Clear, sunny, high contrast and narrowband skies.

Tom M

Clear, sunny skies.
Tom Masterson
Coronado-Lunt-Daystar Solar Filters forum Moderator