Eye Relief:
The distance between the outer (or eye) glass lens and the observer's eye in which the entire field produced by the eyepiece is visible. This is an important consideration as a small eye relief (<5mm) becomes frustrating and more importantly produces fatigue in the eye of the observer while monitoring the planet for delicate detail. Some manufacturers have improved this factor by placing a barlow lens before the inner (or field) lens (e.g. Lanthanum eyepiece with a 20 degree eye relief). A quality barlow (e.g. 2x Ultima) coupled with a medium focal-length eyepiece (e.g. 12-18mm) can provide adequate eye relief at higher magnifications.
The above are vital factors that must be considered in the purchase of an eyepiece to be used for planetary observation.
The following are secondary factors that must also be considered in the purchase of an eyepiece;
5) Apparent field of view
6) Cost ($)
7) Weight (of the eyepiece)
I personally use the University Optics Abbe Orthoscopic, Zeiss Abbe Orthoscopic, Televue Plossl, Apogee Easy-View, and Meade Ultra-wide in my planetary observations. I would like to hear from other observers what their experiences are with different designs and brands of eyepieces.
Respectfully,
Carlos E. Hernandez
The distance between the outer (or eye) glass lens and the observer's eye in which the entire field produced by the eyepiece is visible. This is an important consideration as a small eye relief (<5mm) becomes frustrating and more importantly produces fatigue in the eye of the observer while monitoring the planet for delicate detail. Some manufacturers have improved this factor by placing a barlow lens before the inner (or field) lens (e.g. Lanthanum eyepiece with a 20 degree eye relief). A quality barlow (e.g. 2x Ultima) coupled with a medium focal-length eyepiece (e.g. 12-18mm) can provide adequate eye relief at higher magnifications.
The above are vital factors that must be considered in the purchase of an eyepiece to be used for planetary observation.
The following are secondary factors that must also be considered in the purchase of an eyepiece;
5) Apparent field of view
6) Cost ($)
7) Weight (of the eyepiece)
I personally use the University Optics Abbe Orthoscopic, Zeiss Abbe Orthoscopic, Televue Plossl, Apogee Easy-View, and Meade Ultra-wide in my planetary observations. I would like to hear from other observers what their experiences are with different designs and brands of eyepieces.
Respectfully,
Carlos E. Hernandez
