Pre-Selection
Go step by step:
1.
Diameter of sleeve
Eyepieces are available with three different sleeve diameters. At your
telescope you can use only eyepieces of the same or, via an adapter, of smaller
diameter. Please check the insertion diameter at your telescope:
24,5mm (0.96 inch)
31,8 mm (1 ¼ inch)
50,8 mm (2 inch).
24.5mm diameter are to be found normally only on cheap telescopes. It is hard
to find good eyepieces of this diameter.
1 ¼-inch is standard on most telescopes. You can choose between hundreds of
different eyepieces.
2-inch eyepieces are used only for long focal lengths, as they offer a wider
field of view at small magnifications. For small and medium focal lengths use
an adapter for 1 ¼“-eyepieces.
2.
Quality of the telescope
The quality of the telescope itself will have an effect on the selection of
your eyepieces.
If you own an apochromatic refracting telescope for some thousand Euros than
you should not start to save money on buying your eyepieces. Two optical parts
come together, and they should fit.
The majority of amateur astronomers owns Newtons, Schmidt-Cassegrains or
refracting telescopes of the Fraunhofer-type. Here you can use, as a standard,
our Ploessls. They perform very well, and they are not to expensive. If you are
willing to give a few Euros more, select a wide angle, may be in 2“. However,
also for these telescopes a high-end eyepiece makes sense - but do not expect a
big difference at the first look.
Are you owner of a very cheap discounter telescope? Try to exchange your simple
eyepieces against a 25€-Ploessl! Possible, that you will say “Oops - never seen
before in that way!” when looking on Saturn the first time. Your cheap
telescope may be not to bad, but the eyepieces are for sure.
3.
Type of telescope
Here we talk especially about the focal ratio of the telescope. As faster as the
telescope is (F/6 - F/5 - F/4), as harder for the eyepiece especially near to
the edges. A F/10 refracting telescope will be fine with nearly every eyepiece
type, whereas a F/4 Newton needs high-priced, complex eyepieces at least if you
look for wide angle eyepieces at longer focal length. Systems with F/8 or F/10
additionally need only eyepieces of longer focal length to achieve the maximum
magnification, and also this is an advantage, as eyepieces of very short focal
length mostly have problems with contrast and comfortable eye relief.
On our product pages we have added a comment especially on wide angle
eyepieces, if they are suitable for a specific focal ratio.
4.
Use
There is no eyepiece, which is suitable for all observations. E.g. to make
projections of the sun the best suited eyepiece is a Huygens type. Optical simple,
but good for projection, and there are no lenses cemented together - so it is
robust against heat.
For planetary observers and viewers of double stars there is no need for a big
field of view, a Ploessl or a special planetary eyepiece will be the best
choice. The same is valid for condensed deep-sky objects.
For nebula, galaxies and star clusters eyepieces with a big field of view
and good contrast are recommended. If you find 70° apparent field of view
sufficient or if you would like to have more than 80° - I can not tell you. For
this I recommend to have a view to such eyepieces, may be at telescope
meetings.
5. Purse
How
much money do I have to spend for eyepieces? Hopefully we can ease this
decision with our test results as given on the product pages. We recommend to
look for cheaper eyepieces if you need longer focal length and small field of
view. Such eyepieces are generally of good performance, and there is not really
a need for expensive ones. You would like to have a 30mm wide angle for a F/4
Newton? Sorry, but take the Pentax. No way out.
If you are willing to abandon add-ons like rubber eye cap or similar, you can
use simple Ploessls instead of Super Ploessls without optical compromises. What
you should not do is buying 8€-stuff without reasonable coating. You will spend
double money, because the need for better eyepieces will come - for sure.