Eyepiece shootouts have two sets of guidelines that can be used. If you are performing a shootout centered on deep sky and/or wide field views, the following categories are recommended: *On-Axis Sharpness: How good is the snap to focus? How tightly focused are the stars? *Off-Axis Sharpness: How tightly does the eyepiece focus off axis? If the eyepiece is showing astigmatism, how bad is it? If the stars are focusing into "seagulls" you have readily apparent astigmatism. *Contrast: How much definition is apparent in the deep sky objects? Does the eyepiece have a dark background that helps bring out the faint details? *Field Flatness: If you focus on a star in the center of the field and then move the star to the edge, how badly does it defocus? *Light Transmission: Which eyepiece shows the faintest stars? Is it a big difference that's easy to see, or one that's painfully difficult to detect? *Coatings: Do the coatings appear to be evenly applied without any blemishes? If you cap the bottom with a black cap, how much ambient light is reflected back? *Chromatic Aberrations: Is there false color in the eyepiece around bright objects? How bad is the lateral color? If the color spreads, blue towards the middle is a sign of overcorrection and red towards the middle is a sign of undercorrection. *Eye Relief and Comfort: Is the eye relief adequate? How will glasses wearers fair? Is it easy to get your head/eye in the right position and keep it there? Is kidney beaning problematic? Does the eyepiece have a positionable eyecup (i.e. Instajust, Pentax XL/XW style, etc)? Is there an eyecup at all? If you are performing a shootout that focuses on observing the planets, the following categories are recommended: *Sharpness: We're really focusing on-axis where the eyepiece is the best. *Contrast: Low-level planetary detail is one of the toughest tests for a planetary eyepiece and an optical system as a whole. How detailed are the planetary markings? Is one eyepiece showing more features? *Scatter: Does the background have a velvety-black or a milky quality around the planetary disc? How extensive is the scatter? *Ghosting: If you notice ghosting, how intrusive is it? *Color: How rich are the planetary details? Does the glass appear to have a warm or cool cast to it? *Eye Relief and Comfort: Is the eye relief adequate? How will glasses wearers fair? Is it easy to get your head/eye in the right position and keep it there? Is kidney beaning problematic? Does the eyepiece have a positionable eyecup (i.e. Instajust, Pentax XL/XW style, etc)? Is there an eyecup at all? Other things to watch for: *Field Stop Condition: Is the edge of the field stop sharp? A soft field stop can mean that it's misplaced or that there’s residual spherical aberration. Is there a ring of color around the field stop? A yellow, green, or blue ring may signify overcorrection. A reddish ring may signify undercorrection. (Undercorrected eyepieces usually don't work as well with fast optical systems.) *Geometric Distortion: This is sometimes referred to as the pincushion effect. If you see it, how objectionable is it? *Even Illumination: If the field is not evenly illuminated when the entire apparent field is visible, there may be spherical aberration of the exit pupil. This may be problematic if the exit pupil and the eye pupil are the same size. Also, how well is the eyepiece made? Does the barrel have a safety under cut? Does it fit well in the focuser? Of course there's nothing that says you can't combine all of the categories and make a really big shootout!