H and SR

[andyc277]

With my FirstScope i got 4 Eps. They all have either an H or SR before the mm size. What does this mean?

[brantuk]

Can't find any info on them - they seem pretty basic eyepieces according to the scopes they come with. Not even described on the Celestron site. Is there nothing about them in the manual - you can download it from Celestron

[John]

H = Hygenian and SR = Special Ramsden

They are eyepiece optical designs - pretty simple ones using just 2 single lenses.

[andyc277]

For the price i guessed they are pretty low level eye pieces. Nevertheless they do the job

[brantuk]

Here's a couple of links with a bit more info thanks to John for identifying them:

Eyepiece - Wikipedia, the free encyclopedia

Microscopy-UK Micscape Microscopy and Microscopes Magazine

[John]

... thanks to John for identifying them....

No probs Kim - one of the advantages of i) being an eyepiece nerd and ii) being older

"When I was a lad I used to dream of owning a kellner :rolleyes:"

(this has to be said in a Yorkshire accent !)

[brantuk]

Lol - I was born in Yorkshire haha!

[Polar Bear]

Don't dismiss the eyepieces they will be fine to get you started.

I have had some fine views of the Moon , Jupiter, Saturn and Venus with low grade eyepieces.

When you do wish to upgrade the forum members have a wealth of knowledge to point you in the right direction.

Paul

[Pete Presland]

i think they use to come with the old tasco scopes.i am sure i remember having them in the 80's

[glowjet]

They really do go back a long way, as far as 1783 for the Ramsden "R" two element design and then the SR Special Ramsden or Achromatic Ramsden which was a 3 element design circa 1849, see the pdf Evolution of Astronomical Eye Pieces, Chris lord. Most useful with the long focal length Achro refractors of earlier years

[John]

.... and then the SR Special Ramsden or Achromatic Ramsden which was a 3 element design circa 1849....

The Special Ramsden that I had with my 1960's Tasco 60mm refractor was not that "special" - just two singlet lenses with the convex sides facing each other. With a focal length of 4mm I think the eye relief was around 1mm

It was my double star eyepiece - pretty sharp as long as the object was bang in the centre of the FoV.

[glowjet]

I suppose it was dependent on who was manufacturing them, some of our American cousins report having some SR with three elements, of which two were cemented, I should think these were the Achromatic Ramsdens which were talked about. It would seem there has also been much confusion, as SR have been referred to as super, special and even symmetrical.

John.

[andyc277]

Thats some serious in depth knowledge. I am certainly not dismissing them ( if i do that it will be back to Mk 1 eyeball). I knew they wouldnt be high quality for the price. The best views ive had so far have been of the moon last month, jupiter has been in just the wrong position to get a good view from home but being on leave this week hopefully ill be able to put it to more use.

[John]

Thats some serious in depth knowledge......

Or as my wife would say "a mine of useless information"

These simple eyepieces can work OK if you don't expect too much from them. As you say, better than nothing at all

[andyc277]

Thats my wife to a tee. Any subject shecomes up with a random fact or story

[Ad Astra]

Huygens EP's are named after Christian Huygens, the rival of Isaac Newton in the late 1600's. Seran-Ramsden are similarly named for the originator (and Seran, who improved the design). Both are typical of EP's delivered in small 60mm scopes in the 1950's - early 1980's, when Orthoscopic (3-element) and Plossl (4-element) designs became popular.

H and SR designs tend to feature smaller lenses, and less eye relief / narrower field of view than their Ortho and Plossl cousins. The smaller lenses made them ideal for 0.925 (25mm) EP's common in the day, and less expensive to manufacture. They were often uncoated and uncemented - with low cost being a priority.

Some Astro accessory makers here in the USA offer "hybrid" diagonals, allowing you to put the larger 1.25" EP common today into a refractor with a 0.925" focuser. These cost about $50 (plus the EP's), but you can then take the EP's with you when you upgrade the scope - and you will see a huge performance gain with a basic Plossl compared to these other centuries old designs. I restored a classic 60mm like that just recently - you can see it <HERE>.

The other alternative is just to enjoy what you've got - then hand it over to the kids when you are ready to upgrade to say a 150mm Dobsonian.

Wondrous worlds await you!

Dan

[glowjet]

That is an interesting piece of information Dan, I am unable to trace any reference to a Seran Ramsden, after the Dutch Physicist Christiaan Huygens came up with the first two element design in circa 1703 this was followed by the, Ramsden, designed by the London optical instrument maker Jesse Ramsden circa 1783, the variations being the Achromatic Ramsden three element as also there was an achromatic three element Huygens. I would recommend you have a look at Chris Lord`s pdf " The Evolution of The Astronomical Eye Piece " it would appear this a well respected in depth study of the subject. At the end of the day perhaps SR would be better standing for "Simply Ramsden"

John.

[John]

... I am unable to trace any reference to a Seran Ramsden......

Me neither

I've come across the term Symmetric (or Symmetrical) Ramsden, which you mentioned in an earlier post John. This seems to refer to a design using 2 singlet lenses with matching piano-convex faces with the convex faces toward each other.

There is more on this here:

Telescope Reviews: Super Ramsden?

I'm not sure the eyepiece design deserves this much discussion though

[Ad Astra]

I've seen many attributions to SR EP's, there seems to be lots of disagreement as to the "S" and what it stands for. I've seen references in print to a Mr. Seren who supposedly improved or modified the original design, but as others have said - the EP is not of terrific quality or highly capable, so does not merit further discussion. I also tried to backtrack my references, but was unable to find them on the web. They would be at least 30 years out of date, and I wouldn't be surprised to find out that they were inaccurate.

Much ado about nothing, I think. I still stick by my recommendation that the OP consider upgrading to standard 1.25" Plossl EP's though!

Dan

[glowjet]

I could not agree more John, SR Ramsden RIP

[John]

.... I still stick by my recommendation that the OP consider upgrading to standard 1.25" Plossl EP's though! ......

I'll stick by your recommendation on that as well Dan