David W. Knisely . . . . . . "If you aren't having fun in this hobby, you aren't doing it right." Hyde Memorial Observatory http://www.hydeobservatory.info Prairie Astronomy Club http://www.prairieastronomyclub.org
Quote: As you know the relative rarelty of great seeing in CT is quite seasonal with hot balmy summer nights the best.
Quote:Pete, Encke was a regular feature in my 8" newton, provided the rings were open enough and seeing was good. However, I could not spot it clearly with a 10" newton a couple of mornings ago, seeing being about III. Keeler of course is a different can of worms, I never saw it.I'm using the old nomenclature by the way, not the (confusing) official IAU one.Steady skies,Ivano
The Encke minimum feature may be visible in smaller apertures (and at relatively modest powers), but the actual ultra-narrow division right next to the outer edge of the A-ring? Well, I have a hard time believing it to be seen in any telescope much smaller than 10 inches. The diffraction effects would tend to make it blur into the darkening of the soft outer edge of the A-ring, making it invisible. As I have said before, as hard as the actual division has been to see in 10 and 14 inch apertures, I don't see it being visible in anything much smaller. Clear skies to you.
Quote:Oh tell me about it. I swear its tethered to my condo. Last good seeing for me was Thanksgiving week - a good 5 nights of it were 7/10. After that between 4-6/10.
150mm MCT f/13, 31% CO
"People say I'm in denial. I disagree."
Pentax XL 10.5mm, 14mm
Meade 5000 SWA 34mm, 28mm, 24mm, 20mm
Televue Plossls 21mm, 17mm,
Televue Nagler T1 7mm
Orion Ultrascopic 30mm
Celestron Ultima 18mm
U.O. Orthoscopic HD6mm, HD9mm, HD12mm
Televue 2x Barlow
U.O. Klee 2.8x Barlow
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Celestron Nexstar 40mm
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Celestron 2x Barlow
Quote:... Seeing Encke depend on everything being just right.
18" f/4.2 homebuilt truss 12.5" f/6 hybrid tube dob
Quote:Quote: David, what about Enke's division, ever seen it in your 16 incher
This is what I said in reply to Asbytec [not Ivano] on my "Saturn April 4" thread (Sketching Forum). [Edit Note: apologies for the original error]
If you mean the Encke Minima (what I call the ‘classical Encke’): yes on very many occasions. If the IAU Encke then on average some five or so times per apparition (edge-ons excepted!), but only during better seeing. This latter to me is the true Keeler Gap: the IAU compounding the silliness by calling an impossibly fine line even nearer Ring A’s outer edge the Keeler. Can I see the IAU Encke as a ‘black’ gap like Cassini? Definitely not. On the BAA intensity scale (0 = White/Bright; 10 = Black) I usually make it twixt 7 & 8. Appropriately it looks to me quite like a fine lead-pencil line tho’ often a little diffuse – especially on the inner edge. I can’t rule out contrast effects entirely, but in my view perhaps 60/40: and undecided which predominates: real or illusion!! Nature seems to like hiding real features, at least to some eyes, under illusion/contrast effects; Saturn’s rings seemingly being particularly prone.
Somewhere in the BAA Saturn archive is a drawing of the only time I saw IAU Encke in my 10” (1970s?) also in their Journal – will need to check.
Attached is a graphic to illustrate what I was trying to get across: I have digitally photo'd the 2003 drawing and rescaled vertically to nearer the Hubble image
StarStructure 24" f/3.3 | ServoCAT/Argo Navis
Astro-Physics 175EDF | AP1100GTO | ATS Portable Pier
Psalm 19.1 - A Psalm of David. "The heavens declare the glory of God, and the sky above proclaims his handiwork".
Quote:Amazing how light the hex is in that image. Ok back on topic...
---John 14.5" Dall-Kirkham w/Royce optics Celestron 11 AP140EDF,TEC140,Tak FS60-C ZWO ASI120MM and ASI120MC DMK21AU618.AS SBIG ST-10XE http://www.spacescenes.com
Quote:I've seen the Encke Gap with my past 20" f/4.3 Zambuto Starmaster dob during the winter of 2006 when Saturn was in its northern-most apparition in the sky and the rings were open all the way. I was bino-viewing at about 500X with Saturn directly over head. The Gap was seen steadily as a fine black line with a contrasty appearance, not the gray, blurry and thicker line shown in the photos. It was a lot thinner appearing, but very black. See attached NASA image. The Gap appeared more like 'this' image -- very thin and black.
Quote:Once for Encke, and once for 8 Trap stars 3 years ago- Both times with 8" F/6, and the UO VT 9mm Ortho. Fantastic eyepiece. Conditions have to be essentially perfect; the least disturbance makes them disappear.