Review: Eyepieces for PST Solar Telescopes

[iceman (Mike)]

Hi all

John Wilkinson (John W) has kindly written a review of Eyepieces for PST Solar Telescopes. It's the first eyepiece review in 5 years so I'm very happy to receive it!

You can read the review on the IceInSpace Equipment Reviews page, or directly by clicking on the link below:

Eyepieces for PST Solar Telescopes

Thanks to John for writing the review. If you'd like to contribute an article or review to IceInSpace, please check out Write for IceInSpace and get in touch!

[iceman (Mike)]

Review uploaded.

[koputai (Jason)]

Correct me if I'm wrong, but I think the magnifications in this article are incorrect.

The PST has a FL of 400mm at the input end, but then at the output end there is effectively another scope with an FL of 200mm.

If this is the case, then a 12mm eyepiece will give a magnification of 16.7x, not 33x as shown in the article.

Cheers,
Jason.

[Merlin66 (Ken)]

Jason,
No. The final effective focal length is 400mm.
The "barlow" on the front of the etalon is positioned 200mm inside focus, and the "refocusing" lens is a 200mm focal length.
We have (400-200)+200 = 400

[koputai (Jason)]

Mmm, I kinda understand what you're getting at. To me, it seems that the second 'objective' is 20mm f/10 and takes the parallel rays from the etalon and focuses them 200mm later. The f/10 ratio remains the same, so is it that the 40mm objective has previously concentrated the 40mm aperture into 20mm space that the 400mm focal length is still valid?

Cheers,
Jason.

[Merlin66 (Ken)]

Yes,
The effective aperture is 40mm and the effective focal length is 400mm, hence it stays at f10.

If you remove the PST etalon for a PST "mod" - the ideal donor scope is an f10.
If you put the etalon say into a 150mm f6 scope (900mm focal length) you'll end up with an effective aperture of 900/10 =90mm!
Much cheaper to use a 90/900 scope in the first place!

[koputai (Jason)]

First up for me is a donor Tasco 700/60 (f/11.7), but stopped down by the 58mm ERF. That's effectively 700/54 = f/13 I guess.

[Merlin66 (Ken)]

Yes.
f13 is OK. And almost double the plate scale of the PST.

[brian nordstrom (As avatar)]

Hi , I have a Coranado SolarMax 40 with BF10 and the 3 Coranado eyepieces 12.5mm , 18mm and 25mm with a 2x Barlow that come with it work very well in my scope .
They all look like the millions of generic plossl's out there , but Coranado say they are tuned towards 'Ha' light , and I would believe them as the 12.5mm shows much more prominance and surface detail when tuned into either than both my 12.5mm Orthoscopic and 12mm Vixen LV , both very good eyepieces on night time sky .
The 18mm and 25mm and Barlow all do a better job at Ha observing than similar f/l Ortho's , TV's , Lv's and Meades that I have .
I really thought the Coranado spheel on their eyepieces was hype , but the proof is in the viewing , they are better in my scope , using my eyes .
Brian.

[gawainduncan]

I have the Coronado PST and agree the Meade 4000 15mm works well.
I have purchased Meade 8-24mm zoom and note that this lens is not focusing correctly with the PST. Any ideas on how to modify either to fix this?

[Andre888]

Hi, i want to buy a coronado PST for visually use so, i think about the CEMAX 12 mm and add for higer mag a CEMAX 2x barlow i think is a nice adition. Or is 15 mm 4000 made and 2x made barlow better? ( becource its cheeper) thanks! ( i want to wait for a basic zoom i think its to heavy for my foto trypod...). Thanks for advice!!

[Merlin66 (Ken)]

Andre,
I've been using the PST for many years, both with the CEMAX and "normal" plossl eyepieces.
IMO the plossl's work just as well.
I'd suggest a 10mm and a 15mm to start with.

[N1 (Mirko)]

Agree, regular Plössls work fine.