Peterson Engineering Eye Opener III 2 Inch Visual Back
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The EyeOpener 2-inch Visual Back
- Increase light reaching your eye or camera chip by as much as 65%
- It’s the equivalent of buying the next size bigger scope.
- Fits all Meade 10″, 12″ and 14″ SCTs
Visual observer? 2″ eyepieces are “where it’s at” for the widest and brightest field of view. The EyeOpener enhances the performance of 2″ eyepieces on Meade 10”, 12″ and 14” SCTs by increasing the optical path size from 1 ½” to 2″.
Imaging? With all but the smallest (oldest) chips, all SCT camera setups suffer from vignetting (darkness at the corners of the image). Increasing your scope’s optical path from 1 ½” to 2″ in diameter is almost mandatory for today’s imagers.
History: As Schmidt-Cassegrain Telescopes (SCTs) evolved from 8-inch models to larger-aperture scopes, and as eyepieces evolved from 1 ¼” to 2″, the “Schmidt-thread” couplings used for securing 1¼ inch diagonals and eyepieces to telescope backplates remained unchanged. This “Schmidt visual back” supplied with Meade (and Celestron) SCTs has an internal diameter of 1 ½”, and it functions as a 1 ½” inch-diameter field stop. This field stop effectively limits the performance of modern 2″ optics to the equivalent of 1 ½” optics. When using the 1 ½” visual back with Meade’s 2″ 56mm Plossel (an eyepiece with a full 2″ of glass in the nose) you lose 65% of the light to your eye! For imagers, the same holds true for your camera chip.
The EyeOpener will not improve your viewing with 1-1/4″ eyepieces or with the smaller 2″ eyepieces. But it is hugely beneficial when used with the larger 2″ eyepieces that give you your widest actual field of view.
For a technical explanation of vignetting and how the EyeOpener makes viewing brighter and images both larger and brighter press button.
In the 2008 -2009 period Meade 14″ scopes used a redesigned baffle tube assembly that severely constriction the optical path. A subsequent late 2009 redesign reopened the optical path to a full 2″. Check out your configuration if you have a 2008-2009 era scope. This is for 14″ only.
There are many inexpensive Schmidt thread to 2″ tube adapters being sold. They allow mounting 2-inch optics but DO NOT increase light throughput as the problem is the inside diameter of the Schmidt thread itself.
Which EyeOpener for you?
The EyeOpener directly accepts a 2″ diagonal, 2″ eyepiece, 2″ tube-end focusers and any other 2″ tube used in an optical train. It threads onto a 3-1/4″ male thread found on the backplate of 10″, 12″ and 14″ Meade SCTs. scopes, providing a full 2″ unrestricted optical path. Unscrew your 1-1/2″visual back and check it out for yourself.
The adapter is fabricated from 6061T6 aluminum and black anodized. A brass compression ring is used to prevent marring the inserted 2″ tube while griping it tightly.
The total height of the adapter above the scope’s backplate is only 1-1/2 inches (38 mm). By comparison, with the standard configuration, the nominal height from the scope’s backplate to the back of the microfocuser is 3-1/8 inches. If you need more backfocus this is a solution. With the EZ Focus kit it is possible to make the manual focuser as smooth and precise as a micrometer, pretty much eliminating the need for the microfocuser.
To mount Meade’s #1209 Zero Image-Shift electronic microfocuser you will want the EyeOpener II.