5mm 70° field AF Series eyepiece, with dual 1.25" and 2" barrels

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
The very short 5mm focal length of this Astro-Tech 70° Field AF Series dual-barrel eyepiece is designed for unsurpassed high magnification wide field observing with short focal length refractors and fast focal ratio/short focal length reflectors. Its high contrast makes it an exceptional choice for splitting close binary stars and for seeing faint low contrast lunar and planetary details. With its dual barrel design, it can be used in both 2” and 1.25” focusers and star diagonals with no adapters needed.

It can also be used with longer focal ratio Schmidt-Cassegrains and Maksutov-Cassegrains. However, its exit pupil becomes small and the images dim with these scopes, so its use is generally limited to observing the Moon and planets and splitting close binary star pairs. However, it does provide about the maximum usable magnification attainable with a typical 8” f/10 catadioptric, where it provides a magnification of 400x (50x per inch of aperture) and a 0.5mm exit pupil. Both of these figures are right at the values generally accepted as the rule of thumb maximums for usable observing under good or better seeing conditions.

The 17mm eye relief of this 5mm Astro-Tech is ideal for those who must wear eyeglasses while observing due to astigmatism. Vignetting will be minimal for eyeglass wearers, although the very wide field may require some moving of the head from side to side to see the entire field, even for those who don’t wear glasses.

This Astro-Tech comes with both 1.25” and 2” barrels, dust covers for both ends of the eyepiece, and a plastic bolt-type eyepiece container.

The optical performance of this 5mm Astro-Tech is exceptional at any price, but is truly outstanding at its very sensible price. It is well corrected, high in contrast, flat and sharp across its entire 70° field. We feel that this Astro-Tech 70° Field AF Series eyepiece equals or surpasses the performance of exotic designs costing twice its very reasonable price. It would be a welcome addition to any astronomer’s observing kit.

Field of view:
The field of view (FOV) is the amount of observable world one can see at any given moment.
70°
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.

17mm
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.

5mm
Number of optical elements:
8
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"/2"
Weight:
The weight of this product.
16.8 oz.
Warranty:
2 years
There are currently no Cloudy Nights reviews associated with this product

User Ratings/Reviews from our Customers (www.astronomics.com)
Overall Product Rating: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics(0.00)   # of Ratings: 0   (Only registered customers can rate)

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 - 5mm 70° field AF Series eyepiece, with dual 1.25" and 2" barrels

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

Astro-Tech - 5mm 70° field AF Series eyepiece, with dual 1.25" and 2" barrelsImage showing the fixed 1.25" barrel and the removable thread-on 2" barrel of the Astro-Tech 5mm AF Series 70° field eyepiece.
In Stock
   · No ratings/reviews   Only registered users can submit ratings - Register Here
Our Product #: ATAF7005
Price: $119.95  FREE ground shipping - Click for more info
Congratulations. Your order qualifies for free ground shipping within the 48 contiguous United States.
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 very wide 70° field Astro-Tech AF Series 5mm focal length dual-barrel eyepiece is outstanding for medium to medium high magnification viewing with short focal length refractors and fast focal ratio/short focal length reflectors, and provides about the maximum usable magnification with a typical 8” f/10 catadioptric . . .





. . . our 34th year