Last updated: 19 July 2002

Uranus and Neptune Observations with the ETX-90RA

Sent:	Thursday, July 18, 2002 13:02:48
From: (martyn)
Here's my observation of Neptune and Uranus of a couple of days ago.
The observations were made with an ETX90RA.

NEPTUNE and URANUS, 16 July 2002 01:30hUT - 02:55hUT.

This night I stayed up with the purpose of viewing Neptune and Uranus,
as I had never seen them before and tonight was very clear with very
low humidity - no dew on the scope at the end of the night.
Until Neptune-time I visited several clusters and nebulae.
The night started out with some wind, so the seeing was nothing to be
excited about. Arcturus was twinkling quite heavily, but at the zenith
it didn't seem to be bad afterall.
But at around 04:00h(local) the atmospere seemed to have quited down a
Also, at about 01:30h(03:30h local time) I noticed that the sky was
allready past it's darkest for this night.
I was setup in the backyard with a wall of the house at my back, and
to the right. A streetlight was brightly reflected against that wall
and a large window in it and the paving as well, so I shielded my eye
from that light with a hand. I should  have rather put a cloth over my
head, but oh well, I didn't think of that at the time. There was also
a slight haze in the air which -added to the lightpollution- must have
impaired my view to some extent.
After I had found Neptune the sky gradually brightened due to dawn
being on the way.

ETX 90 RA, #884 tripod, Orion dewshield, manual RA-tracking, digital
voice recorder for note-taking without looking away from the eyepiece,
Redshift planetarium software for relevant data and searching for
starpatterns to use for starhopping my way to the planets.


NEPTUNE, transit at 00:51hUT (02:51h local).
Located Neptune @ 16 July 2002 01:30UT (03:30h local), alt: 19d 09'35"

Starhopping to the planet Neptune with the 10X50:

Secunda Giedi(Alpha 2 Capricorni) & Prima Giedi(Alfa 1 Capricorni)
Beta Capricorni
Rho Capricorni
SAO163895 and SAO163910, a conspicious "pair" in the 10X50.
Neptune, just to the upper left of SAO163895, the planet and the above
conspicious "pair" form a little triangle.
The planet was thus easy to locate, however it took some time checking
the Redshift software whether I had the correct stars....running in-
and outside all the time.

With a plossl 40mm it was easy to centre the planet in the field of
view, and then I went almost fullblast right away....with the UWA4.7mm
at 266X.
What I saw was a tiny bluish fuzzy with a brighter centre. Not quite a
disc, but clearly not a star. I compared the image of Neptune with
that of a star and immediately saw the difference.
I followed Neptune until about 03:45h(local) at which time it had an
altitude of 18d 41'54". When I found this planet it was allready past
transit(02:51h local) and viewed it at a decreasing altitude at a time
when the atmosphere hadn't quieted down to it's best for the night
quite yet.

So, no clearly defined disc on Neptune tonight, maybe another day.
Although I have allready picked-up from the literature that the limb
of Neptune should be darker than the rest of the planet and might
therefore not show a nice disc in my little ETX 90. I'll keep on
trying anyway.

URANUS, transit at 02:04hUT (04:04h local).
Located Uranus @ 16 July 2002 01:55UT (03:55h local), alt: 24d 27'07"

Starhopping to the planet Uranus with the 10X50:

SAO164520(Epsilon Capricorni) and SAO164593(Kappa Capricorni)
SAO164560(Gamma Capricorni or Nashira) and SAO164644(Delta Capricorni
or Deneb Algedi)
SAO164861(Iota Aquarii)
Uranus, which was to the upper right of this last star.
There were no other bright stars confusing the scene, so Uranus was
found quite easily. There was no need to check my Redshift software
several times.

03:55h (local), alt=24d 27'07":
With a plossl 40mm I centred the planet in the field of view and
exchanged the lowpower-eyepiece for the UWA4.7mm, 266X.
What I saw was a small, pale-greenish DISC, clearly!!! Seeing was not
superb but the disc is clearly made out.
It's limb wavers at times but is overall quite well defined. It's a
REAL little DISC!!!
It's color is very conspicious, clearly: pale-greenish.

04:00h (local), alt=24d 28'24":
Through the plossl 3.8mm, at 328X I see the same, just a bit larger. A
fairly well defined disc.
I prefer the view through the UWA4.7mm at 266X.
Sky is getting blue-ish, but the planet shows very well.

04:04h (local), alt=24d 28'40":
Uranus in transit. Sky is dark-ish blue. Uranus' disc intermittently
VERY WELL defined at 266X. Pale-green color seen continiously and

04:07h (local):
Uranus still easy to find in the 10X50. NE horizon is quite bright
allready. Capella is blazing away in the dawn.

04:10h (local):
Sky noticably brighter, through the UWA4.7mm Uranus' disc and color
are still very well seen.

04:15h (local):
The plossl 3.8mm shows the same image, possibly slightly less bright
than at 266X. It now also seems that the atmosphere has quieted down a
bit. Uranus shows very well through the UWA4.7mm.

04:17h (local):
I am starting to notice a difference in image-contrast, as dawn is
creeping upon the sky.

04:30h (local), alt=24d 13'45":
Through the UWA4.7mm Uranus' disc and pale-green color are still
clearly visible.

04:40h (local):
Uranus is now noticably getting less easy to see....52 minutes before
sunrise. But still, Uranus' limb and color are still quite well
visible, just at a lower contrast. The sky is rather "bright" and blue

04:50h (local), alt=23d 42'52":
Contrast is now getting seriously low at 266X. In the eyepiece
(UWA4.7mm) field of view the sky had also become a "bright"
blue...almost(but not quite) starting to look like a daytime-sky.
But still.....Uranus' disc was quite well defined and it's pale-green
color just kept piercing through. I never saw any markings at all  on
the planet's disc. I wonder how long I would have been able to follow
Uranus at this magnification. I wasn't going to find out as I wanted
to get some sleep. I still viewed Uranus through the plossl 40mm for
another five minutes and marveled at how bright the planet still was
at 31X. Even at this low magnification and bright skybackground there
seemed to be a perceptible greenish tinge to that beautiful bright
star in the eyepiece.

As I packed up, I felt very satisfied with my night outside...and with
my etx90RA as well!!!

clear skies
observing from the Netherlands
52 40.30 N
 5 56.10 E

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