Found an Eyepiece online - advice?

[flawedprefect]

Hi guys. I hope I'm asking in the right thread. If not - apologies to the mods, I'll respect your decisions should this be moved.

I've been looking online for some extra eyepieces, and I came across this site: http://binocularsandtelescopes.com.au

They sell a 2mm Long-Eye Relief eyepiece: http://binocularsandtelescopes.com.au/skywatcher-2mm-long-eye-relief-eyepiece-swlet2-p-817.html

Which I am interested in. I've looked around on this site to see if anyone's reviewed this brand but failed to find anything. Has anyone had experience with this brand, or think it's a decent buy? What does Long-Eye Relief mean exactly? Still coming to grips with the terminology.

Pardon my n00biness. :D

Cheers guys,

Paul C

[Kevnool]

Hi Paul ask the question with which scope you want to use it on.
Cheers Kev.

[astro744]

2mm is the focal length of the eyepiece. The long eye relief (20mm for this eyepiece as stated on the web site) makes this eyepiece suitable for eyeglass wearers but can be used by non-eyeglass wearers. Eye relief is the distance from the eye lens where you place your eye to see the full field of the eyepiece.

2mm is extremely short and will give you very high powers on all but the shortest telescopes and then these 'scopes will need to be high quality apochromatic (APO) refractors to give you a good image. If you are using a high quality APO then you will do better with a high quality 2-4mm zoom eyepiece such as the Nagler Zoom.

What telescope do you have since its type and focal length will determine the best size eyepieces that you can use?

[Jeff]

Hi Paul,

You can get a good range of "value for money" eyepieces from Bintel and Andrews Communications:

https://www.bintelshop.com.au/welcome.htm

http://www.andrewscom.com.au/site-section-10.htm

In many scopes under common viewing conditions (with atmospheric "seeing" limitations), you will fail to under about 200x magnification. This would equate say to a 5mm eyepiece being used with 1000mm focal length scope.

See the "Eyepieces" introduction from Bintel (on the menu bar across the top of their website screen).

Good starting range for many people would be 3 eyepieces to provide say 50x, 100x, and 200x magnification.

In terms of quality and price/value, you typically get what you pay for as there is a fair bit of competition in the market place. I started with relatively economical Bintel, Guan Sheng (GSO), and Meade eyepieces ... and then eventually converted to more expensive Televue and William Optics eyepieces when my interest & investment in the hobby grew within the following year or two.

Hope this helps.

Jeff

[flawedprefect]

Hey guys - cheers for the info. I have a Bintel BT-150 750mm 6" diameter Newtonian on an EQ mount. I've got a Plossl 25mm and plossl 9mm plus a 2x barlow. I like the eye pieces they're fair enough, but I saw some long eye relief models recently and I wonder if their design was more comfortable - ie: do they give you a wider "field" than these plossl eye pieces? Cheers for the advice thus far. Plenty to look at and consider.

[Screwdriverone]

Hi Paul,

Dont confuse eye relief with Field of View (FOV).

Eye Relief is basically how close you need to have your eyeball to the glass on the eyepiece to get a full view of what is coming through the eyepiece.

FYI, Large Focal length eyepieces ie 20-30mm and bigger generally have more eye relief than smaller EP's. The smaller the eye relief, the closer you need to get to the eyepiece and generally the less comfortable it is to take in the view. This is especially important for eyeglass wearers where longer eye relief is generally a must.

Now Field of View, is how WIDE the image you see is when you get to the optimum eye relief position. Easy way to think of this one is looking through a small hole in a fence, you have to get up close to see anything (Eye relief), and then because of the restricted field of view, you dont get to see much anyway. Compare this to a soccer ball hole, the eye relief is great and the field of view is huge because you can put your head through it and look around.

Its a bit simplistic and (possibly a bit technically wrong) but I am just trying to explain what the difference is when it comes to comfort and enjoyment of eyepieces.

Generally, for the price, a 68 degree FOV EP with about 15-20mm of eye relief is going to be comfortable and "widescreen" enough to look through for just about everyone. Sure, you can pay $800-$1000 for a Televue Ethos 100 degree "PORTHOLE" view into space, but for your scope, i would suggest some standard ED type eyepieces from Andrews Comms or similar which are about $60 each and are great performing general purpose eyepieces.

For your FL length of the 6" scope of 750mm, and with Jeff's excellent suggestion of 50x , 100x and 250x (probably the highest limit of that size scope, then the FL EP's for these mags are (in order) 15mm, 7.5mm and 3mm. (to work out the magnifications you divide the FL of the scope by the Eyepiece FL, ie 750 / 15 = 50 x)

Using your 2x Barlow also doubles the magnification, but keeps the Eye Relief of the original FL Eyepiece so you could use a 6mm eyepiece (125x) and then add the barlow to get 250x rather than buy a 3mm and suffer from small FOV and potentially restricted eye relief.

Hope this helps

Chris

[flawedprefect]

SWEET. Thanks for that info Screwdriverone. It was extremely helpful. I'm just beginning this journey and I'm not familiar with most of the jargan. Your post explain ALOT.

[StarGazing]

Great explanation Chris, makes good sense with me :thumbsup:

"Its a bit simplistic and (possibly a bit technically wrong) but I am just trying to explain what the difference is when it comes to comfort and enjoyment of eyepieces."

Cheers Alex.

[Screwdriverone]

You are very welcome, glad I could help.

Cheers

Chris