Meade #932 45° Erecting Prism for the ETX-90 and ETX-125: What It Does and How to Use It

The original post on this site was a short listing for the Meade 07210 No. 932 45-degree erecting image prism. This rewrite uses Meade UK’s product page for the #932 and Meade’s ETX-60AT/70AT manual, which describes the matching prism for the smaller ETX models, to explain what this accessory does and who needs it.

Why ETX telescopes need an erecting prism

Meade UK explains that all ETX-90 and ETX-125 models have an internal flip mirror that reflects light to the telescope‘s 90° astronomical observing position. In this position the image is upright but mirror-reversed from left to right. For the sky, this does not matter: stars and planets have no “correct” left and right for most observers. But for land viewing, such as reading a sign or watching wildlife, a reversed image is confusing.

Orion’s AstroView 90 manual describes the same effect with a standard star diagonal on a refractor: the view is correctly oriented up and down but reversed left to right. It recommends a 45° correct-image diagonal for daytime use.

What the #932 does

According to Meade UK, the #932 45° Erecting Prism attaches in seconds and gives an image that is both right side up and correct left to right, with a 45° observing angle that is more convenient for daytime work. Meade suggests it for observing wildlife, the view from your home, or other Earthly applications.

Verified specifications

From Meade UK:

• Meade product code (SKU): 07210
• Prism type: erecting
• Viewing angle: 45°
• Fitting: ETX-90 and ETX-125
• Attachment: threads to the telescope’s rear camera port
• Weight: 75 g
• Dimensions: 8.5 cm x 4.5 cm x 6 cm

Which telescopes does it fit?

Meade UK lists the #932 for all ETX-90 and ETX-125 models. The smaller ETX-60AT and ETX-70AT use a different prism: Meade’s ETX-60AT/70AT manual describes the #933 45° Erecting Prism, which threads onto those telescopes’ photo port.

Corrections to the original listing

• Compatibility: the original said the #932 suits “all Meade ETX models except ETX-60, 70 and 80AT”. Meade UK lists only the ETX-90 and ETX-125, so check your model before buying. Owners of the ETX-60AT and ETX-70AT should look at the #933 instead.
• Magnification factor: the original claimed a built-in magnification factor of 1.08x. Meade UK’s page gives no such figure, so we removed it. (The different #933 prism, by contrast, contains a relay lens that increases each eyepiece‘s power by 2.4x, according to Meade’s ETX-60/70 manual.)
• Weight: the original gave 0.20 lb; Meade UK lists 75 g, which is about 0.17 lb.
• Not an eyepiece: the original title called it a “telescope eyepiece”. It is a prism; you still insert an eyepiece into it.

How to use an erecting prism on an ETX

Meade’s ETX-60/70 manual explains the steps for the #933, and the same idea applies to the #932 on the larger ETX models:

• Thread it onto the rear port: the prism attaches to the telescope’s rear (photo or camera) port.
• Flip the mirror down: on the ETX-60/70, the manual says the flip-mirror control must be in the “down” position so light goes straight out the back to the prism. Check your ETX manual for the equivalent setting.
• Insert an eyepiece: an eyepiece of any focal length can go into the prism.
• Focus: refocus, as the eyepiece position changes.

When to use the standard eyepiece position instead

Meade’s ETX-60/70 manual makes a useful point: for the most demanding views, such as delicate bird-feather detail at long distance, the telescope’s internal, optically flat mirror gives a higher-resolution image than any prism. In those cases it advises observing through the standard 90° eyepiece holder and accepting the reversed image. For astronomy, use the normal 90° position too.

Tips for daytime viewing

• Never point at or near the Sun: Orion’s AstroView 90 manual warns never to look at the Sun without a proper full-aperture solar filter, and children should only observe with adult supervision.
• Use low power: Orion’s manual suggests correct-image diagonals are best at low magnifications, around 50x or less, for land viewing.
• Mind the heat: Orion’s manual advises avoiding viewing over asphalt and rooftops, where rising heat blurs the image.

Quick summary

• The #932 gives a correctly oriented image and a 45° viewing angle on the ETX-90 and ETX-125.
• It threads onto the rear camera port; weight 75 g.
• ETX-60AT/70AT owners need the #933 instead.
• For astronomy and maximum sharpness, use the standard 90° eyepiece position.