Detail on Ceres?
Posted 24 September 2013 - 06:50 PM
Posted 25 September 2013 - 07:09 AM
Thank you for your input here. More over, the link showing Sussenbachs image compliments yours well as it shows well the effect of aperture-resolution on an object just above diffraction pattern size. Based on your success with the Gallilean moons and other challenging targets then it would appear this one is out of reach in terms of seeing any surface details. The imaging forum turned up nothing as well here. Too bad really - though like Titan which Ive seen resolved Im sure it is a captivating site.
- incidentally, Curt Renz in private message was kind enough to pass along the following information on Ceres most favorable apparitions:
"For its current apparition, according to my calculations Ceres will come closest to Earth at 1.6450 AU on 2014 APR 14. According to my friend Jean Meeus in "Mathematical Astronomy Morsels V" the next time it approaches closer than 1.6 AU will be on 2023 MAR 21 at 1.5990 AU and then on 2032 FEB 24 at 1.5848 AU"
My thanks here to Mr.Renz as well - Im hoping and confident he doesn't mind my posting this correspondence.
Lastly, David, I read the Vesta can become as 0.7" so that's surely one that'd show we'll in your scope - perhaps even slightly out of round?
Posted 25 September 2013 - 07:48 AM
Ceres: I guess there are not contrasty enough features for me to get anything with it. Similarly with Europa which has never yielded anything to me.
Vesta: since my previous post I have been trying to locate a file similar to the Ceres one, but never reported. It is from 2010 Feb. when it was in the Sickle/Leo and was quite pinkish and elongated. I know I included a very tight double nearby (elongated-below 0.2") for comparison, also a single star. Thing is other nights, at that time, it looked virtually stellar/round. I could conjecture that this latter aspect could be when it was narrow 'end' on. I believe my impressions now could be checked out with JPL Horizons Ephemeris Generator for CMs.
Back to the search - think it is in some other object's file: Saturn perhaps!
Posted 25 September 2013 - 09:19 AM
I think your depiction above is exactly what we could expect to see: an enlarged or slightly elongated (maybe) PSF. It would not be much different from a star in more modest apertures, but it's extended object characteristic (bigger than a point source PSF) might well be detectable.
Posted 25 September 2013 - 10:16 AM
Note that the p.a. of the double is suspiciously near that of Vesta - hence the additional inclusion of the single star which tends to rule out any abberation or seeing vagaries I feel.
A2145: Sky Map Pro 11 gives 0.14" 23.6º for 2010; but cross-checking with 6th Orbit Cat. data (2011 on) suggests this to be a misplaced decimal point (p.a) in Sky Map.
I have to say that I've never attempted detail on either asteroid, but many failed attempts with Europa.
Titan: as we know there is a N/S hemisphere brightness difference and have suspected glimpsing this several times but never sure enough to report it.
Ceres: Please note that the out-of-roundness with the linked drawing is simply artistic incompetence on my part - a slip of the mouse/'brush' in Photopaint!
Posted 25 September 2013 - 05:54 PM
I'm curious about the light that surrounds Vesta and Ceres - Ive seen it around Titan in 9 Pickering and it appears like a diffused diffraction ring. Hovering so close to *the limit" it would make sense that such a thing is seen . I would imagine this is that threshold when the diffraction pattern and extended objects share some similar artifacts. Would you say this is proximity glare or the beginning of diffraction ring encircling the small orb?
Thanks again for the words and illustrations.
Posted 25 September 2013 - 09:51 PM
Posted 25 September 2013 - 10:13 PM
I thinks it's a blast he got Ceres' egg shape.
Posted 27 September 2013 - 05:52 AM
What you say about the blurred ring around Ceres & Vesta I feel is correct - a sort of mushied (that's a technical term ) Airy diffraction ring perhaps. Actually Mars (4.3") showed it to a degree in the poorer moments of otherwise very good seeing yesterday a.m.
The drawings here show a sort of average appearence in the stated seeing; it being more suppressed in the very best moments I find. As I said earlier with Vesta some nights it was as drawn and a following one I found it virtually stellar (and quite round) and that includes the appearance of the the ring/s. Possibly its smaller 'end' presented??
Pete: when you say Ceres potato/egg-shaped in my drawing - did you mean Vesta? I know the linked Ceres one shows departure from roundness but that was my Photopaint ineptitude. I have attached a corrected version - done yesterday hoping for internet co-operation.....!!
Posted 27 September 2013 - 08:06 AM