[AZ-Observing] Encke minima/gap, was Re: Observing the weekend of Jan 2-5, 2003

  • From: "Matt Luttinen" <mluttinen@xxxxxxxxx>
  • To: az-observing@xxxxxxxxxxxxx
  • Date: Mon, 30 Dec 2002 01:05:33 -0700

Silvio,

I am not Thad (darn), but I have some experience viewing
Saturn through a small scope.

I have seen the Encke minima twice in my Synta 120 mm
f8.3 refractor. The first time was about a year ago from
my back patio in Glendale with a 2x barlowed Nagler 9 mm 
type 6 yielding 222x. The detail level that night was
amazing, it was like looking at a miniature Hubble image.
The second occasion was recent and also on my back patio.
This time I used a Meade UWA 8.8 mm barlowed for 227x,
so the mag was virtually the same. The day and time was 
Friday the 13th at 2-3 am. The atmosphere had been mediocre
earlier, but it calmed nicely as it got late, and Saturn was 
at (almost) the zenith. I actually placed the barlow in front 
of the diagonal for somewhere in the area of 340x and the view
was still worth looking at, if somewhat soft. Floaters become an issue
though when working at ~0.35 mm exit pupil and 72x per
inch! I think that my objective must be one of the better of
the Chinese achromats out there to deliver (sort of) clean 
images at this kind of power.

That said, most of the time the views of Saturn can't take
the 8.8 UWA barlowed, and you are lucky to get the "under water"
effect to stop for more than a split second. Sometimes it is
impossible to nail down focus it is so bad. The vast majority
of nights are like this for me. 

However, on the two nights I have mentioned the image of the planet 
would steady up for many seconds at a time, and focus was nice and
snappy at 227x. All the brighter moons were present except Mimas at
mag 12.6, which is probably a little beyond my urban mag limit 
with this scope. 

I am going to try for Mimas at Sentinel this weekend, as I believe
it is a test of my visual acuity with the 4.7". 
It is no Tak or A-P, and the brightness of Saturn makes for dicey
averted viewing. I hope the seeing is good enough.

How small a scope can resolve the Encke? I imagine a 3" APO/ED 
could do it on a great night in the hands of a skilled observer . . .

Matt

-----Original Message-----
From: az-observing-bounce@xxxxxxxxxxxxx
[mailto:az-observing-bounce@xxxxxxxxxxxxx] On Behalf Of Silvio Jaconelli
Sent: Sunday, December 29, 2002 3:16 PM
To: az-observing@xxxxxxxxxxxxx
Subject: [AZ-Observing] Re: Observing the weekend of Jan 2-5, 2003


Thad,
I think I recall from a recent posting that you had seen the Encke Gap.

Would you mind a few questions ?

- What scope and which eyepieces did you use ?
- What was your magnification ?
- Would you happen to know the minimum aperture required to see this ?

Thanks in advance for your inputs ...
Silvio.


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