Long Eye Relief 12.5mm 1.25" eyepiece

by Astro-Tech Print

What would you like to print?
(Reviews and Documents/Videos will not be printed)

Basic Product Information
Full Description
Tech Details
Supplied Accessories
Recommended Accessories
Images

Print
More product information
This medium focal length Astro-Tech 12.5mm Long Eye Relief eyepiece is usable with any telescope type, under virtually any seeing conditions – from fair to superb. (Rain, snow, or fog might limit its usefulness, however.) It has a long 20mm eye relief that provides comfortable full field viewing for all observers, including eyeglass wearers. Its very flat field keeps small details sharply in focus from one edge of its 55° field of view to the other, making it an appropriate choice for resolving star clusters (both globular clusters and the more compact open clusters) and for scanning the lunar surface.

It is also exceptional for low to medium power viewing with short focal length refractors and fast focal ratio Dobsonian reflectors. With short focal length refractors, such as those from Astro-Tech, it’s into the low power range. With the 72mm aperture 430mm focal length AT72ED, for example, it provides 34x and a field over three times as wide as the Moon. This is well suited for observing open clusters such as the Pleiades and large nebulas such as the Lagoon. Both will fit nicely into the AT72ED’s 1.58° field, with a framework of black sky around them to set them off.

The 12.5mm Astro-Tech Long Eye Relief is also excellent for medium high magnification observing with long focal length refractors, reflectors, or catadioptric scopes. On an 8" f/10 catadioptric, for example, it yields 160x. This is an excellent magnification for planetary and close-up lunar observing. Its performance makes it a much better choice as a second eyepiece than merely doubling the power of most scopes’ standard 25-26mm eyepiece with a Barlow.

The Astro-Tech’s very high contrast makes it an exceptional choice for resolving faint low contrast lunar details and for seeing subtle detail in planetary nebulas, while its sharpness across the field makes globular clusters vivid and nearly three-dimensional.

Field of view:
The field of view (FOV) is the amount of observable world one can see at any given moment.
55°
Eye Relief:
Eye relief is the distance from the last surface of the eye lens of an eyepiece to the plane behind the eyepiece where all the light rays of the exit pupil come to a focus and the circular image is formed, sometimes called the “Ramsden Disk.” This is where your eye should be positioned to see the full field of view of the eyepiece. If you must wear glasses because of astigmatism, you’ll usually need at least 15mm of eye relief or longer if you want to see the full field of view with your glasses on.

A note on our eye relief figures: Quite often, our eye relief figures will differ from those of the manufacturer. This is because we measure the “usable” eye relief, while the manufacturers specify their usually-longer (but technically correct) “designed” eye relief.

The eye lens of the eyepiece is normally recessed below the rubber eyeguard or rubber rim of the eyepiece to keep the lens from being scratched during use. An eyepiece might have a “designed” eye relief of 15mm (and the eye relief will truly measure 15mm from the eye lens to where the image forms). However, if the eye lens is recessed 3mm below the eye guard, the Ramsden Disk forms only 12mm above the eyepiece body (the 15mm “designed” eye relief, less the 3mm of eye relief made unusable by having the eye lens recessed into the body of the eyepiece). This “usable” eye relief of 12mm (measured from the rolled-down eyeguard – the closest point you can get your eye to the eye lens – to where the image forms) is the eye relief figure we would measure and list in this website.

Why is it important to list the “usable” eye relief? For those people who don’t wear eyeglasses while observing, a few mm difference between the eye relief they expect from the manufacturer’s literature and the shorter eye relief they actually get in real life doesn’t mean a lot. They can simply move a little closer to the eyepiece to see the full field, and never realize that the eye relief is a little shorter than they expected. However, some people must wear eyeglasses while observing, because of severe astigmatism. These observers can’t move closer to the eyepiece if the eye relief is shorter than expected because their glasses get in the way. For these people, the real life “usable” eye relief is more important than the technically correct but sometimes not fully usable “designed” eye relief. We measure and list the actual usable eye relief so that people in the real world can pick the eyepieces that will work best for them.

20mm
Focal Length:
This is the length of the effective optical path of a telescopeor eyepiece (the distance from the main mirror or lens where the lightis gathered to the point where the prime focus image is formed). Focallength is typically expressed in millimeters.

The longer the focallength, the higher the magnification and the narrower the field of viewwith any given eyepiece. The shorter the focal length, the lower themagnification and the wider the field of view with the same eyepiece.

12.5mm
Number of optical elements:
7
Barrel Size:
The industry standard diameter, as of 2011, is 1.25" and is the most common.  Other sizes available are .965" and 2".
1.25"
Weight:
The weight of this product.
6.4 oz.
Warranty:
2 years
Reviews from Cloudy Nights (www.cloudynights.com)
These reviews have been written by astronomers just like you and posted on the Cloudy Nights astronomy forums . . .
Review of Astro-Tech LER Eyepieces

User Ratings/Reviews from our Customers (www.astronomics.com)
Overall Product Rating: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics(5.00)   # of Ratings: 1   (Only registered customers can rate)

(Only registered customers can rate)

5 - Great (100.00%) (1 user)
4 - Good (0.00%) (0 users)
3 - OK (0.00%) (0 users)
2 - Bad (0.00%) (0 users)
1 - Very Bad (0.00%) (0 users)
0% 50% 100%
astronomics image

Sort Ratings: 

  Show these ratings: ALLGreatGoodOKBadVery Bad

loading request
Showing comments 1-1 of 1
1. Neil on 5/27/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
I love this eyepiece for planetary viewing in my 90mm Mak. Nice contrast and eye relief - especially for allowing others to view who may wear glasses. I have a 10mm plossl, but I prefer the view from this eyepiece.
Was this comment helpful? Yes No   (0 people found this comment helpful, 0 did not)
Showing comments 1-1 of 1
We haven't recommended any accessories for this product quite yet... check back soon or call one of our experts (1-405-364-0858).
This product does not have supplied accessories... or supplied accessories have not been assigned.
Documents
No documents have been associated with this product.
Videos
No videos have been associated with this product.
Helpful Formulas
Telescope Eyepiece Formula
To calculate the magnification and approximate actual field of view of this eyepiece on your telescope, enter the focal length of your telescope below and press the "Calculate" button.

Enter your telescope's focal length: mm   



Astro-Tech - Long Eye Relief 12.5mm 1.25" eyepiece

Click icon(s) below & hover image above for zoom

Astro-Tech - Long Eye Relief 12.5mm 1.25" eyepiece
Wait List
 AstronomicsAstronomicsAstronomicsAstronomicsAstronomics (Average: 5.00 | Users: 1)  Only registered users can submit ratings - Register Here
Our Product #: ATL12
Price: $59.95  Ground shipping for this item is $8.95 - Click for more info
By adding 1 of these items to your cart your order total will be less than $100, and will ship within the 48 contiguous United States for $8.95. Add $40.05 to your order, however, and you qualify for free ground shipping (heavy items with fixed shipping, such as counterweights, excluded).
Quantity:   

 E-mail this product to a friend E-mail this product to a friend

Your Email:  
Your Friend's Email:  
Confirm Friend's Email:  

Comments:
  200 characters or less
 

An email containing a link to this product has been sent to the email address you provided.

Clear Skies!
Astronomics

 Have a question? Do you have a question about this product?
 Found a better price? Found a lower price? Click to let us know... or call 800-422-7876 before you buy.

If you’ve found a lower delivered price on this product, let us know about it below. We’ll do our best to meet or beat that price and will get back to you within one business day with our best offer. Thanks for giving us the opportunity to give you a better deal.

Your Name:  
Price:  
From Who:  
Context:  Magazine AdOnline
Website Address:  
Cut and paste the web address into the box above
Your Email:  
Confirm Email:  


We’ll do our best to meet or beat that price and will get back to you within one business day with our best offer. Thanks for giving us the opportunity to give you a better deal.

Clear skies,
Astronomics


This Astro-Tech 12.5mm Long Eye Relief eyepiece has great flat field optics and a comfortable 20mm of eye relief that any observer with any type of telescope (not just eyeglass wearers) will appreciate all night long . . .





. . . our 34th year