Re: (IAAC) FWD: What should I buy? (rich field scopes)

Nick Martin wrote:
> I just got a 12 mm Nagler and have had one night to use it before we reached
> zero darkness as we have now. It was a very impressive view, contrast was
> much better than my 15 mm Plossl and if anything the field of view was
> wider. I also got a second hand 4.8 mm Nagler a couple of months before.
> This gives excellent contrast on deep sky objects or comets but for the moon
> the contrast was much poorer than with a 4.5 mm Orthoscopic, quite
> surprisingly so really but Naglers are deep sky eyepieces. The thought does
> occur that this may be related to poor baffling in the scope and hence
> greater intake of scattered light with the large field lens and wide angular
> apeture of the Nagler so their reputation for poor planetary or lunar
> contrast may relate more to the scope than the eyepiece.
> For low power I have an eyepiece from a stereo microsope. I am not sure of
> its FOV but it is probably about 40' judging from the moon. It works
> reasonably well considering I got it free (Its microscope was stolen leaving
> the spare eyepieces behind))
> I think I will sell on the 4.8 mm as at X466 it is too high a power to be
> easy to use with my Dobsonian and too expensive to keep for the odd time it
> might be useful. I will probably go for a 7 mm. or stick with my 9 mm
> Orthoscopic. What does anyone think?
> Your
> Nick
> Nick Martin, Bonnyton house, By Ayr, Ayrshire KA6 7EW ,Scotland, UK.
>  Longitude 55 24'56" Latitude 4 26' 00".
> "Thou star of evening's purple dome
>  That lead'st the nightingale abroad,
>  And guid'st the pilgrim to his home."
>    To the Evening Star by T.Campbell
The 12mm Nagler T2 is one fine eyepiece for deep-sky observing with a fast Dob.  Of
all the eyepieces that I own I use it and a 19mm Panoptic most often with my 12.5".
I'm not sure what you mean by "wide angular ape(r)ture" (wide apparent field of
view?), but I believe the consensus opinion is that the fewer lens elements in a
planetary ocular the better.  Each lens element robs a little of the incident
light.  (And a Nagler has a lot of lens elements.)  Thus 4 element orthoscopics are
usually the eyepieces of choice for planetary observers.  (I have used the
legendary Zeiss orthos on a few occasions.)
Did you mean a 7mm Nagler?  That would be better choice than keeping the 4.8mm,
IMHO.  It will still produce over 300x in your scope but that will be a far more
usable magnification than 466x!
Dave Mitsky

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