The following should be considered a diversion rather than a recommendation. The whole purpose of scopes is to provide magnification so trying to achieve the minimum magnification would seem to be a pointless exercise, at least for terrestrial use.
I recall that several years ago a birdforum member wanted to observe animals at dusk at the end of his garden and a scope permanently trained on a garden feeder might be another application. However, low magnifications can be visually appealing, just as they are in binoculars, e.g. 7x42.
I don't own an astronomical scope and neither do I know my way around the night sky very well, but have nevertheless acquired a few astro eyepieces for use with my Swaro ATM 65HD and Kowa 883 for occasional looks at the moon, planets and the Mercury transit in 2016.
One often sees comments on birdforum from members wishing to improve on the performance of their scopes with astro eyepieces, but I think that in general that is a vain hope. I see field curvature and pincussion distortion through all my astro eyepieces and in this respect, none of them can compete with the 30x wide on the Swaro or the 25-50x TE11WZ on the Kowa. The eyepieces are tailored to the scopes and probably use a Smyth lens to correct for field curvature.
All waterproof birding scopes have a plain glass window in the body to retain the nitrogen filling. On the Swaro this has a diameter of 26 mm and on the Kowa 24 mm, so it would not make sense using astro eyepieces with larger field stops such as a 32 mm Plössl or 24 mm Panoptic (both 27 mm), which have the maximum available field stops with a 1 1/4" barrel.
Enthusiastic reports on "Cloudy Nights" encouraged me to buy a 28 mm Edmund Optics RKE, which has a 23 mm field stop and should not vignette significantly. It's a simple triplet with single coatings (espoused by some, including Brandon to offer some advantages) and a mere 45° AFOV. The eye lens is 25 mm in diameter so with 21 mm of eye relief the slim eyepiece mount seems to disappear and the image just floats in space. On the Swaro it gives 16,5x magnification with a 4 mm exit pupil and on the Kowa, 18x with a 5 mm exit pupil. Particularly on the latter, the brightness and contrast are absolutely outstanding.
I expect anyone with an astro adapter for his scope and a long FL eyepiece has already tried this. Otherwise forget it. Eyepiece collecting is a really pointless addiction!
John
I recall that several years ago a birdforum member wanted to observe animals at dusk at the end of his garden and a scope permanently trained on a garden feeder might be another application. However, low magnifications can be visually appealing, just as they are in binoculars, e.g. 7x42.
I don't own an astronomical scope and neither do I know my way around the night sky very well, but have nevertheless acquired a few astro eyepieces for use with my Swaro ATM 65HD and Kowa 883 for occasional looks at the moon, planets and the Mercury transit in 2016.
One often sees comments on birdforum from members wishing to improve on the performance of their scopes with astro eyepieces, but I think that in general that is a vain hope. I see field curvature and pincussion distortion through all my astro eyepieces and in this respect, none of them can compete with the 30x wide on the Swaro or the 25-50x TE11WZ on the Kowa. The eyepieces are tailored to the scopes and probably use a Smyth lens to correct for field curvature.
All waterproof birding scopes have a plain glass window in the body to retain the nitrogen filling. On the Swaro this has a diameter of 26 mm and on the Kowa 24 mm, so it would not make sense using astro eyepieces with larger field stops such as a 32 mm Plössl or 24 mm Panoptic (both 27 mm), which have the maximum available field stops with a 1 1/4" barrel.
Enthusiastic reports on "Cloudy Nights" encouraged me to buy a 28 mm Edmund Optics RKE, which has a 23 mm field stop and should not vignette significantly. It's a simple triplet with single coatings (espoused by some, including Brandon to offer some advantages) and a mere 45° AFOV. The eye lens is 25 mm in diameter so with 21 mm of eye relief the slim eyepiece mount seems to disappear and the image just floats in space. On the Swaro it gives 16,5x magnification with a 4 mm exit pupil and on the Kowa, 18x with a 5 mm exit pupil. Particularly on the latter, the brightness and contrast are absolutely outstanding.
I expect anyone with an astro adapter for his scope and a long FL eyepiece has already tried this. Otherwise forget it. Eyepiece collecting is a really pointless addiction!
John
