Whats the difference between a Plossl and other EP's

[stardad]

Morning. Its another newbie question.

What is the difference between a Plossl and an 'ordinary' eye piece?

Looking here ...... Celestron ......

you can see Celestrons versions of a Plossl and a X-cel series of Ep's. Why have the two? In another post somebody suggested that using a Plossl would not be a good idea as they were uncomfortable for long periods of time. So why do manufacture's make them then?

This topic is really getting me

Cheers

[Merlin66]

The plossl design has become a basic standard over the past few years. Various manufactures produce similar eyepieces but of varying quality...when they are good they are very very good...when they are bad they're horrid!

I've been using TV Plossl's on various telescopes for almost thirty years and never had cause to complain.

The X-cel series, if you note, highlight the 20mm eye relief - this is the main difference - a good choice for someone who has to wear glasses.

[stardad]

Thanks for the info.

My daughter wears glasses hence the question about the X-cel series but at £60 a pop that's going to be expensive for 3 Ep's.

I've just found a primer about lens's but that shows about 8 different variety of lens's. It says that Plossl's are for medium strength so i'm guessing that is going to be the 18mm lens for an f5 scope after reading the another primer.

[Moonshane]

you could also try the TMB planetary series or BST Discovery from skies the limit. they retail at about £39 and many people feel they are excellent value for money and with good eye relief too.

[Chris H]

Bear in mind that if you do wear glasses you only need to wear them whilst observing if you have an astigmatism.

[great_bear]

There's no such thing as an "ordinary" eyepiece. Each one is a variation on one design or other - the Plossl being just one of many.

The Plossl design is popular because it strikes a good balance between simplicity of design and a wide field of view.

Strictly speaking, a Plossl is made from two pairs of lenses in a very specific configuration, however these days it is not uncommon for a fifth lens to be added between the two pairs for better optical correction.

Plossl eyepieces under 15mm can be uncomfortable because your eye needs to be very close to the eyepiece. One solution to this is to use a Barlow lens with a longer length Plossl to achieve the equivalent focal length.

Another major advantage of Plossl eyepieces is that good ones are available very cheaply.

You will often see different versions of Plossl eyepieces from any particular manufacturer because product ranges change over time due to cost savings and/or product improvements.

[great_bear]

Bear in mind that if you do wear glasses you only need to wear them whilst observing if you have an astigmatism.

And even then, only at longer focal lengths.

[PeterM]

Morning. Its another newbie question.

What is the difference between a Plossl and an 'ordinary' eye piece?

Looking here ...... Celestron ......

you can see Celestrons versions of a Plossl and a X-cel series of Ep's. Why have the two? In another post somebody suggested that using a Plossl would not be a good idea as they were uncomfortable for long periods of time. So why do manufacture's make them then?

This topic is really getting me

Cheers

The main features of Plossl eyepieces is that by modern standards they can tend to have a relatively narrow field of view and have eye relief that lessens that shorter the focal length of the EP. That's it.

The eye relief thing won't really come into play until you get under around 10mm focal length or the the longer end of things, or unless you have to wear glasses to look through the scope (most people prefer not to use their glasses if they can get away with it).

I've never found them any less comfortable than any other EP for extended observation. Things might get a little more troublesome at the short end of things (eg 5mm) but that's partly why manufacturers have introduced variations on the theme like the X-Cel range you mentioned.

It's pretty easy to make a good Plossl EP, hence why there are loads of differently branded ranges but I think it's fair to say that unless you pick an absolute dog then you'll probably be happy with almost any Plossl. There's less glass in them and views can be really crisp, sharp and vibrant especially compared to some of the lesser wide angle alternatives.