eyepiece help

[Kevdan]

Hi all,

Just wondered what all the abbreviations mean which ar eattached to eyepiece sizes, for example TS,E,K,H,SR,SP,ED

Is this just the manufacturer or does it refer to something else?

I have ordered a Skywatcher 130p and it comes with a 25mm and 65mm eyepiece, what others would you get for this scope?

Also are all moon filters neutral density and more to the point what does it mean?

Kev.

[Cornelius Varley]

Most of the abbreviations stand for the type of eyepiece,

TS I think is Telescope Service which is a German retailer.

K = Kelner

H = Huygens

SR = Super Ramsden

SP = Super Plossl

The four above are optical designs

ED stands for (E)xtra low (D)ispersion - a type of optical glass.

Neutral density filters are filters which reduce the amount of light passing through them without adding any colour. ND filters are gray in colour. A variable polarizing filter can also be used as a moon filter to adjust the amount of light transmitted.

Peter

[Kevdan]

Thanks for the reply, are there any to avoid ? I have heard that S & HR arent very good.

Kev

[Ags]

Thanks for the reply, are there any to avoid ? I have heard that S & HR arent very good.

Kev

H and SR, lol! Nothing wrong with my TS Planetary HR EPs :-)

Don't know what HR stands for though - I think it is just marketting blah.

[SimonR]

Ramsden [R], Huygens [H] and Kelners [K] are quite early designs, in the 20th Century they were largely overtaken by Orthoscopics [Or], Erfles [E] and then Plossls. There is an interesting (and I think down to earth) article here Eyepiece Review Pitfalls

On another matter - are you sure that eyepiece is 65mm? Seems very long.

[pvaz]

Stick with orthos for planetary observation and plossl for widefield low mag. These are the ones that will give you the best quality for your money. If you use glasses while observing then you'll need more complex designs to get a large eye relief.

The complex designs can be as good as a quality Ortho/Plossl in terms of light transmission, baffling, aberrations correction and contrast while being more confortable to use and displaying more sky. The problem is, for them to tick all this boxes, the price rises to 5x to 15x the price of a good ortho/plossl as they are much more expensive to produce, with several glass elements to be polished and coated.

On the planetary end there is a complex design EP, the TMB planetary clones, that seam to have great quality and cost less then the best plossls/orthos.

On the widefield end, it depends on your scope focal ratio. Above f/6 most will behave well enough, under f/6 you either ignore the soft-out-of-focus edges or you need to spend a lot of money for perfect edge-to-edge views.

[John]

Just to complete the picture:

TS = Telescope Services - a german based retailer who puts their brand on some of the eyepieces they sell.

[SiriusB]

Kev,

you're as well to ask questions, there are that many different eyepieces available these days its quite confusing.

When i started, my choice was pretty limited- Kellners or Orthoscopics were about all i could find to buy in the UK that were halfways decent, Eventually i ended up with 2 Kellners & 3 Orthoscopics, & that did me for a good few years.,Anyway i digress.

Enjoy the eps you have for a week or three, then you should have an inkling about what objects you enjoy observing the most, which may influence your choice of type & magnification required.

Plossls are probably the best VFM general purpose ep.

If you buy from a reputable astronomical supplier eg :FLO , you are VERY unlikely to get a truly bad eyepiece these days- but ask questions first, or you may not end up with the eyepiece best suited to YOUR needs & telescope.

Hope that helps.

[Kevdan]

Thanks Guys,

I ws wrong about the supplied eyepieces though, they will be 10mm and 25mm super modified achromatic (MA) which in turn give 26x and 65x magnification.

Am I right in saying now that with a 2x barlow i can achieve 52x and 130x magnification and with 3x barlow 78x and 195x magnification, and would that be more or less the limit of the scope as far as magnification is concearned but how will that effect the quality of images?

Kev.

[pvaz]

As a general rule you can go up to 2x per millimeter of aperture, but best views usually end at around 1.5x per mm. I would stick with a 2x barlow for visual, 3x won't see much use, I suspect.

The MAs supplied with SW telescopes are not very good. The 25mm will be ok but the 10 is not very sharp and displays noticeable color aberration on the bright objects.

I purchased a 90mm skywatcher evostar for my sister. This are the upgrades I did to make it enjoyable:

- Replaced EPs with 3 wide field low budget EPs (around 50£ each). They behave well at f/10. 3 EPs on a scope where you can't push the mag over 180x are more then enough for all situations.

- Added a reflex type finder (telrad). The original was useless. I have some experience and it was a nightmare to point the telescope at anything. The telrad is maybe a bit big for the scope but works like a charm.

- I'm waiting for a 2/h 90º diagonal. It's hard to make a decent session when you spend 15min with your knees on the cold wet floor...

The scope itself is nice and the AZ3 mount is stable. Color aberration is kept down even for an achromat and it displays decent views of planets. It's not too shabby on the brightest DSOs, though the aperture doesn't allow much detail resolution on them. M13 for example, is filled with countless individual stars on my 8" dob. The 90mm fractor displays it as an out of focus light blob which fails to impress most observers.