Ultima Duo 17mm 1.25"/2" visual/imaging eyepiece

by Celestron 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

More product information
This dual purpose viewing/imaging Celestron Ultima Duo 17mm eyepiece uses a new eight element/five group fully-multicoated optical system to provide a wide 68° field of view for visual use. Integral 42mm T-threads under the removable roll-down rubber eyecup allow solar system imaging use with a SmartPhone, DSLR, or CCD camera. 

The Ultima Duo 17mm is usable with any scope type, under virtually any seeing conditions – from fair to superb. (Rain, snow, or fog might limit its usefulness, however.) An f/4.5 Dobsonian will yield a 3.8mm exit pupil, putting it into the rich field observing range. 

With short focal length refractors, the 17mm Ultima Duo is a low power, very wide field eyepiece. With the 430mm focal length Astro-Tech AT72ED, for example, it gives you 25x and a 2.49° field that is five times as wide as the full 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 its field when used with the Astro-Tech AT72ED, with a framework of black sky around the objects to set them off. 

This 17mm Celestron Duo is excellent for medium magnification observing with long focal length refractors, reflectors, or catadioptric scopes. On an 8" Schmidt-Cassegrain, for example, it yields 118x and a 0.57° field. This is an excellent magnification for lunar observing, where the Moon will nearly fill the eyepiece field at this magnification. 

Its full multicoatings provide high contrast that makes it a good choice for resolving lunar detail and planetary nebulas, while its edge-to-edge sharpness makes it well-suited for lunar, planetary, and globular cluster observing with an SCT. Some of the larger globulars, such as M13, will fill half of its 0.57° field with such a scope, with a nice framework of black sky around the object.

Click on the "Telescope Eyepiece Formula" link in the "Formulas" tab above for a calculator that will show you the magnification and approximate actual field of view of this 17mm Celestron Ultima Duo eyepiece with your particular telescope.
Field of view:
The field of view (FOV) is the amount of observable world one can see at any given moment.
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.

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.

Number of optical elements:
Barrel Size:
The industry standard diameter, as of 2011, is 1.25" and is the most common.  Other sizes available are .965" and 2".
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)

Photographic Accessories
Camera Adapters (3)
Ultima Duo eyepiece to Apple iPhone 4 or 4S imaging adapter
by Celestron
Ultima Duo eyepiece to Apple iPhone 5 or 5S imaging adapter
by Celestron
Ultima Duo eyepiece to Samsung Galaxy S4 smartphone imaging adapter
by Celestron
This product does not have supplied accessories... or supplied accessories have not been assigned.
No documents have been associated with this product.
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   

Ultima Duo 17mm 1.25"/2" visual/imaging eyepiece

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

Ultima Duo 17mm 1.25"/2" visual/imaging eyepieceImage showing the Celestron 17mm Ultima Duo eyepiece with eyecup removed to show the T-threads.
In Stock
   · No ratings/reviews   Only registered users can submit ratings - Register Here
Our Product #: CULD17
Manufacturer Product #: 93444
Price: $129.95  FREE ground shipping - Click for more info
Congratulations. Your order qualifies for free ground shipping within the 48 contiguous United States.

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

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

  200 characters or less

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

Clear Skies!

 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:  
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,

This dual purpose 17mm Celestron Ultima Duo eyepiece is good for medium power 68° field viewing with long focal length scopes, as well as through-the-eyepiece solar system imaging with a SmartPhone, DSLR, or CCD camera.

. . . our 38th year