Choosing eyepieces

I have a f/5, 8'', Dobsonian reflecting telescope and a f/5, 4'', rich field refractor.

At the present, most of my eyepieces are lousy Kellners but I do have a UO 16mm Erfle. I would like to obtain three to four eyepieces under $800 which would cover a good spread of powers.

I'm currently interested in the below eyepieces:
Low power:
40mm UO MK-70, 31mm Proxima, 30mm Widescan II, 42mm Vixen Lanthanum Superwide

Medium Power
21mm Siebert Standard Kellner 80*, 24mm TAL UWA, 8-24mm Vixen LV Zoom

Low Power
7mm Speers-Waler, 9mm Nagler Type I

Any ideas? Any experiences with the above eyepieces? Your views would be greatly appreciated......

Well, at f/5 I think you will do well to steer towards the better corrected eyepieces out there. I'm not that keen on any of the low power eyepieces you mentioned for an f/5 scope. I use a 40mm Pentax XL in my 10" f/5 and like it better than the 40mm UO MK-70 and 30mm Widescan II.

Siebert seems to use the singular word "element" to refer to a cemented groups of lenses as well as singlets, so it's hard to be sure how complex some of his designs are, but I am guessing that at f/5 the field correction of the 21mm would not satisfy me, even when considering only the central 65 degrees.

I do like the older 9mm Nagler a lot, as well as most Pentax XLs (especially the 5.2mm, 7mm, and 10.5mm), other Naglers with 12+ mm or eye relief, and the Meade Ultrawides. The Vixen LV Zoom is okay.

A small set of eyepieces needs to take into account your observing habits and preferences. For example, I'm mainly into planets and globulars with an occasional excursion to look at the showcase DSOs of other types. In my 10" f/5 I think I could get along fine with my 40mm Pentax XL, 10.5mm Pentax XL, and 5.2mm Pentax XL. I also occasionally use 21mm and 7mm Pentax XLs and a 3.5mm eyepiece made by combining a 7mm Nagler T6 with a Tele Vue 2x Barlow, but I'm sure I would not feel deprived if I had only the first three that I mentioned. Those who tend to regard the moon as light pollution would doubtless pick a different three, and of course being satisfied gets easier as you allow for more eyepieces.
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Mike