Outreach EP Suggestions?

I'm doing outreach solar viewings with my 5" f8 achromat with a Coronado 60mm etalon / BF15 combination. My 40mm Plossl is a tad weak, and my 20mm Burgess W.A. is too strong; any suggestions for a *budget* 26mm to 32mm or so W.A. eyepiece? Not sure if a 30mm Plossl would have adequate F.O.V.

Thanks

It depends on your definition of "wide field" and "budget," but Explore Scientific's 82-degree eyepieces are very nicely priced.

Gotta have cheaper? Look at the same company's 68-degree oculars...

The Edmund RKE 28 has a very generous fov and are still "low cost". You could also try some of the Rini and Siebert wide fields, although some of the Seiberts are entering collector's status now. Both of these offer huge fovs for fraction costs and still work VERY well. I've used them in rich newts and in a C11.

James Adams said:

I'm doing outreach solar viewings with my 5" f8 achromat with a Coronado 60mm etalon / BF15 combination. My 40mm Plossl is a tad weak, and my 20mm Burgess W.A. is too strong; any suggestions for a *budget* 26mm to 32mm or so W.A. eyepiece? Not sure if a 30mm Plossl would have adequate F.O.V.

Thanks

The short answer first: I think a standard 30mm Plossl would work fine for you to frame the full disk of the sun with enough sky between the Sun's edge and the eyepiece's field stop. You could even try a 26mm Plossl and get acceptable results in my opinion. Andy's suggestion of the 28 RKE is a good one in my opinion.

Now for the long answer: What I have in my eyepiece collection (much more limited that Andy's or Rod's) is (1) a very modest Celestron 32mm Plossl (I have several) that you can find used here on Astromart pretty often because it was the longest focal length of the set that came in the Celestron eyepiece & filter set that came in the nice silver case. I use this 32mm with a C-102, f9.8 and it gives me a nice moon with some sky to frame it in. The 40mm gives me more sky (which is what I think you meant by "My 40mm Plossl is a tad weak"). The other eyepiece I would reach for in my eyepiece case is (2) the Celestron Ultima 35mm (which may be harder to find on the used market these days. It would be a nicer quality eyepiece, but may be too much of a collector's item to put out into an "Outreach" situation and might be too much sky for me.

In my 8 inch, 2000mm f10, SCT, I use a 2 inch Televue 55mm (that I bought from Andy to step up from a 50 mm Surplus Shed 50mm) to "nicely frame" the full moon's disk or (with the full aperture solar filter) I enjoy the Sunspots with a very comfortable amount of sky surrounding the sun's full disk like you seek, if I understand your situation.

Doing the math, 2000/55 or 2000/50 gives around 36 or 40 power which is a nice, comfortable half degree disk (sun or moon) framed by what I think is about right amount of sky in my scope with the 55mm or the 50mm (40 mm isn't enough field of view for me to enjoy the full disk, the field stop is just too close). With your 125mm * f8 gives you about 1000mm focal length being half of what I'm used to, so, I would say Andy's suggestion of a 28mm is really close with the RKE's generous field of view (or it might be a little more sky than I would like). I would try a 26 mm Plossl and see how you like it as a very low cost experiment and adjust the power from there.

My final thought is about field of view vs eye relief: I need to use my glasses to observe because I have astigmatism bad enough to need the glasses to correct to get decent views. That means that I go for eyepieces that have about 20mm or more of eye relief. For outreach, this delights the others who need glasses, but I find that I have to "coach" the better sighted to back away from my eyepieces enough to avoid the "blackout" that comes from "missing the exit light with the pupil" light by being too close.

Best regards & Clear skies,

Ed

Thanks for your kind replies and suggestions. I've picked up a vintage Meade 26 Plossl [two, actually, for the binoviewer] and have a line on a 30mm Plossl when I have funds available.

AM has been a great resource! Thanks again.

J. Adams