Can anyone identify this lens?

[richardda1st]

Hi forum,

Can anyone identify this lens? (see attached pics).

I purchased this lens (thru the internet) in a vane hope to improve my Tasco 114mm reflector. All I know is it's a 1.25" and supposed to be a plosyl lens. I hope to be able to use it with my forthcoming purchase of a 10" dobsonian reflector57780

57779

57781. How does it rate.

Any info much appreciated
Richard

[Wavytone]

Eyepiece designs rank more or less as follows:

1 Huygens (17th century), Ramsden (18th century) primitive, not made anymore
2 Kellner or "Achromat" - cheap entry level eyepiece, low power 25mm-60mm, small field of view, common in the 1970's
3 Plössl (OK as a general purpose low - medium power), moderate eye relief, moderate field of view, suitable for 15-40mm focal lengths. In short focal lengths (less than 12mm) eye relief and field of view are very small and orthoscopic would be a better.
4 RKE - good eyerelief, moderate FoV, design suitable for 8-30mm focal lengths, budget eyepiece from about 1980.
5 Abbe or Orthoscopic - low distortion, high contrast, moderate FoV, suited to high power lunar & planetary. Very short eye relief (about nil).
6 Erfle, König, excellent design for medium power, suited to scopes of f/7 or slower. Not suitable for scopes at f/5.
7 Assorted "Superwides" and "Ultrawides". Huge FoV (65-85 degrees) but not optimal with respect to lateral colour, distortion, sharpness.
8 LVW, Panoptic, Speers-Waler, Stratus (barely) or Hyperion (barely) - large FoV (65-70 degrees), good eye relief, design spans the entire range 3.5 to 30mm. LVW and Panoptic are the pick. Excellent with respect to lateral colour, distortion, sharpness. Only negative aspect is large size.
9 Nagler, Ethos - Huge FoV (75 - 100 degrees), sharp edge to edge.

And there is a special case - the Monocentric (planetary high power).

A lot depends on:

- the telescope you will use it with (especially focal ratio) - a Ramsden eyepiece will work fine with an f/15 refractor, for example, but is useless on a fast f/5 reflector;

- who the manufacturer was - there is a huge difference between eyepieces made by Zeiss, Clave, Brandon or Televue (best) vs those from say Tasco or the chinese clones.

- when it was made and the glass types used - great improvements have been made with the advent of modern ED glass types in recent years.

So on this scale I'd rate yours as a 3 out of 9. Eyepieces like this will be fine on longer focal ratio scopes - f/8 or more. But for a scope that is f/4 or f/5 (such as a 10" Dobsonian) you will find it disappointing and very hard to use. For an entry-level dob I would suggest two of the cheap chinese superwides from www.andrewscom.com.au would be a good idea.

[Miaplacidus]

Hi Richard,
Good luck with the dob. It'll trounce what you have already.
Most new telescopes will come with one or two reasonable eyepieces (usually Plossls), so you should haggle to have them included if they aren't included already. And if you do get them, often they are good enough and useful enough for a lot of practical observing, sometimes forever, and at least for months.
So don't be too impatient. Finding items that you want to spend your money on isn't usually a problem in this hobby. (E.g. one or two choice eyepieces will end up being better value than a drawer full of mediocre glass.)
Cheers,
Brian.

[TJD]

it says its a 6.5mm fully coated optics

[richardda1st]

There's always one in every crowd.
Thanxs Trev

[TJD]

your welcome:p

[Galactic G]

My tip is that it's a Meade 3000 series, 6.5mm Plossl like this one:-
http://www.ioffer.com/i/Brand-New-6-5mm-Meade-3000-Superior-Plossl-Eyepieces-66989721

[richardda1st]

Hi
I'd say it's a perfect match. Good to know what brand. I'm sure I paid a lot more then $13.10 for it a few years ago.

Thanks Galactic G for the answer.
Thanks to Wavytone for the info.
Thanks to Miaplacidus, I have been haggling for a 2nd plossl to clinch a deal.
Thanks again to Trev for the wise-crack.

Richard:thumbsup::doh:

[TJD]

any time richard congrad on your new sccope