CN FORUMS ARCHIVE Telescope Reviews: Some news about planetary eyepieces

Some news about planetary eyepieces

The German astronomy magazine Inter Stellarum number 41 shows
a comparison of five planetary eyepieces, written by Carsten Reese
and Ronald Stoyan.

I found this information in the internet and by performing a rally to town,
I was able to get it just 5 minutes before the kiosks in the main station closed!

I try to give you an impression. The text is four pages long...

The tested eyepieces are:

Televue Nagler zoom 3 - 6mm (used only in the 5mm position) (5 elements in 3 groups)
5mm Pentax XO (5 elements in 3 groups)
5mm Astro Physics Super Planetary (3 elements in 2 groups)
5mm TMB Supermono (3 elements in 1 group)
5mm Televue Radian (7 elements in 5 groups)

The used telescopes were:

8" Newtonian f-5
14" Newtonian f-5
4.7" Astro Physics APO f-8
4" TMB APO f-8

The tests were performed by both astronomers independently.

Now only what I found interesting:

They got the construction designs only from Pentax and TMB.
Televue and Astro Physics were not willing to give the drawings of
the lens assembly or any other informations, even when they asked
these two companies about them.

I skip the laboratory measurements as the observation part is more
interesting.
My thoughts are in {}.

Under not perfect observation conditions there were no differences
between the eyepieces to be noticed with 8". But with the 14"er and
the high quality APOs the differences were already obvious at a medium
seeing.
{I have suspected since quite a time that eyepiece comparisons performed
with small scopes under not optimal seeing conditions don't show enough:
Ouch! for several, well many, eyepiece comparisons I have read...}

Definition (or sharpness)
The test object was a seldom shadow-sickle shown by the shadow of Io
when passing in front of Jupiter. The sickle was here because Io covered its
own shadow (this is shown very clearly by a drawing and a foto in the actual test).
In all scopes the Pentax XO showed the best sharpness on-axis with a
minimal unsharpness at the border. It was followed very close by the TMB
Supermono which was sharp to the border. The Nagler Zoom was not able to
show such a sharp view, followed by the AP SPL. Last was the Radian.

I skip the eye relief and observation-comfort part as this can be read elsewhere.
(They were "more or less satisfied" with all EPs - except by the Radian which
showed "shadow-phaenomenas" if one does not get the right eye position).

Colour fidelity
Observing Jupiter with the two Televue eyepieces one doesn't notice any error in
the colours. But if one observes after with the extremely clear and white Pentax
or TMB eyepieces so the slightly yellow tint of the TV Radian and Nagler zoom
becomes obvious. Also the AP SPL shows this yellow.

I skip the distortion as there were only slight differences by observing.

Ghost pictures (reflections)
No reflections in the TMB.
Faint ones in the Pentax XO when the planet enters or leaves the field of view.
Nagler zoom shows some reflections when Jupiter is in the field of view,
but they disappear as soon as Jupiter gets out of the FOV.
Radian shows obvious reflexions when Jupiter enters or leaves the field of view.
Strongest reflections showed by the AP SPL.

Quality of coatings (scatter)
{I hope I translate "Streulicht" correctly by "scatter".}
The two moons of Saturn (Tethys, mag10.1, and Dione, mag10.3) were used
to judge the quality of the coatings, since they are situated near the bright planet.
This is not to be confused with transmission, as a transmission difference of 10%
will lead to a magnitude difference of circa 0.1mag which will be hard to notice
{finally a clear definition of transmission differences, finally!

}.
With the 8" telescope the Nagler zoom shows both moons when using averted vision.
The TMB shows them also (always with averted vision), but fainter than the zoom.
The Pentax XO shows Tethys constantly, but Dione only sporadically.
The AP SPL shows Tethys sporadically, but Dione not at all.
The Televue Radian does not show any of them.

Conclusions
The best performer when observing Jupiter and Saturn was the Pentax XO with
a very clear and very white view.
A tad behind is the TMB Supermono, which is very free of reflections. It is also the
least expensive of all tested eyepieces, but shows only a 32° field.
Unbeatable in its manifoldness is the Nagler zoom, which, being a zoom, can replace
several single eyepieces, unfortunately it shows a slightly yellowish colouring.
The Televue Radian is the most comfortable of the five tested eyepieces, but shows
the same yellow as the zoom.
Disappointing is the performance of the Astro Physics Super Planetary. It can only
keep up with the other four eyepieces regarding sharpness on-axis and off-axis.
{in the section "definition" they did not describe it so well...}

I have tried to translate as well as I can and to sum up as well as I can.
I hope to have been able to give you an impression of this test and to
give you the main results. There were some posters in the past who asked
for a comparison TMB Supermono vs. AP Super Planetary. Here it is.
If you have questions, I will see if the text tells something and write you back.

I have worked far more than three hours on this text.
If you think it was interesting, and don't even write a thank you -
so I wish you very bad dreams tonight!

Amalia

Edit: Corrected the section about reflections.

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Edited by Amalia (07/31/05 11:11 PM)