Review: Eyepieces for PST Solar Telescopes

[iceman]

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 (http://www.iceinspace.com.au/reviews.html) page, or directly by clicking on the link below:

Eyepieces for PST Solar Telescopes (http://www.iceinspace.com.au/42-630-0-0-1-0.html)

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 (http://www.iceinspace.com.au/write-for-iceinspace.html) and get in touch!

[iceman]

Review uploaded.

[koputai]

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]

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]

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]

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]

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]

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

[brian nordstrom]

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]

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]

Agree, regular Plössls work fine.