Erfle?

[Greenswale]

I am experimenting with eyepieces, and am looking for a 32mm with not a lot of glass between my eye and the scope. I recall using an Erfle type in the past, and it performed really well on faint fuzzies, and had a much better field of view than plossls.

Erfles are offered by several manufacturers and reviews are varied. Thus I am seeking local opinion on which is 'best', to suit my 9.25 with or without a focal reducer.

Whaddyareckon?

[mental4astro]

From what I recall, the GSO Superview is an Erfle design. I have the 30mm and 15mm, but I don't recall using them in my C8 - I've used them pretty much exclusively in fast Newtonians. The 15mm is good and fairs better than the 30. But that's not hard as the Erfle is designed for refractors which have the same focal plane shape as SCT's, and opposite to Newt's. Next time I have my C8 out I'll pull out the Superviews and give them a going over and let you know.

Mental.

[Wavytone]

Wren,

if you really want one buy this:: http://www.edmundoptics.com.au/microscopy/eyepieces/edmund-32mm-rke-wide-angle-erfle-eyepiece/2074/

But... the Erfle is a very old design and there are better choices.

I should add I once had a monster war-surplus Erfle around 35mm, but these babies were uncoated so the light transmission loss is ~40% of the light just by virtue of that. For something comparable around the 30-35mm mark in your scope I would suggest:

a) TMB Paragon 30mm, this is a modified orthoscopic, 4 elements, fully multicoated. There is also a 40mm version of this eyepiece but many (self included) reckon the 30mm is by far the one to pick.

The snag is finding one, as you will have to trawl Astromart or Cloudynights to find one secondhand.

I had one, it was pinpoint sharp right across the field and gives a view like diamonds on black velvet. Only reason I sold mine is that I had a few things that better suited my f/15 Maksuotv...

b) Televue Plossl 32mm, which will be superior to any Erfle.

[Kunama]

Takahashi have just released a new 28mm Erfle eyepiece.
About $195 but 20mm ER 60ºAFOV and Tak quality.

[clive milne]

Seriously... Erfles were a cute but fundamentally flawed concept at inception.
The integration of contemporary eyepiece design with modern manufacturing techniques should have consigned the idea to the anachronism bin, 20 years ago, never to return.

[AG Hybrid]

Couldn't agree more. Less glass doesn't necessarily mean more light transmission. It certainly doesn't mean a better view either.

That being said F/10 is pretty forgiving. If you really must have one and you have the money to burn - that Takahashi sounds over priced but interesting.

[Greenswale]

Thanks for the replies. Seems that I was being a bit wistful, I'm over it now!

Erfles are off my toy list!

[dannat]

if you want good light transmission in a simple design at f10 you can get away with one of the cheap kellner's, small no of elements & better transmission of faint stuff than the superviews; ive got either a 26 or 40 i could give you but have no 32


anyway the less glass elemenst ep's are really all about the planets- pulling out detail i certain regions: if you want good DSO details you need modern mltiocatings -if you can find one dig up a sterling plossl 30mm -

[clive milne]

Masuyama might be a design of interest as well.

Celestron cloned it and called the range 'Ultima'
They are one of the things that Celestron managed to get right in an otherwise undistinguished history of optical fabrication. Several other companies did basically the same thing.

[Greenswale]

Daniel, thank you for the offer, but I'm over it. Gonna stay modern!

Clive, I recall having an Ultima a while back. Now I know why it was pretty good, thanks!!

[croweater]

I have had an "Ultima" Barlow for over 20yrs. Excellent quality but were Jap. made back then. I don,t know about now.