24 May 2018 at 10:54 am #574044MaksymowiczParticipant
Next 26th october will occur the inferior venus conjunction.
This will be the more favourable period for trying to capture this controversial light visually and by Imaging.
It would be interresting to have a look on this topic, the more observer we can meet the more this will be frutfull.
2018 is a calm period for sun activity. The planet phase at conjunction will be very low (<0.006), the separation between sun and venus will not be tiny, >5°, the elevation above horizon 23° at the best on 49°N lattitude.
This will not help a lot the occurrence of this light by the low sun activity (one hypothesis), by the planet separation to sun (an other hypothesis consisting in the vision of diffracted light beam at the planet limb, the keller cone effect), by the planet elevation above horizon involving some lack of colors, the bluish portion of the Spectrum (an other hypothesis consiting in a phenomena favorising specific colors, result of electro-chemical effects in atmosphere).
Personnally, my favor will consist in the presence of a phenomena involved by a light play, roughly the keller cone, a diffraction effect of the sun light crossing the venusian atmotphere at the limb. Just an hypothesis.
So at final, this is an invitation to observe on the period venus ashen light. We can consider the period commencing from the planet phase 0,50 to 0, before and after conjunction. with color filters, B, G, R, deep red, without.
Your comments will be helpfull and appreciated.
an example24 May 2018 at 10:01 pm #579529Richard McKimParticipant
I hope all observers will have a look. In two papers just accepted for the Journal, I have analysed all 14 elongations of Venus for 2007 till the start of 2018, and the second paper deals with the nocturnal hemisphere. I am copying the Abstract here in case it is of interest to members: Here we discuss the nocturnal hemisphere, with details of infrared thermal emission (IRTE) imaging and the Ashen Light (AL). Images of the IRTE revealed up to nine topographic features upon the surface of the planet and enabled the slow rotation rate of the surface to be measured for the first time from amateur images. D.Gasparri was able to record subtle, large-scale IR-absorbing low-altitude clouds, which were more prominent in 2009 than in 2017. The 2017 inferior conjunction saw remarkable high resolution reached by P. Miles and A. Wesley: the small bright spots they were able to resolve upon the planet’s surface might provide evidence for active volcanism. The AL was recorded in a small number of visual observations, though only a few sightings were confirmed by a second observer. However, on 2009 Mar 12 the AL was imaged in the visible waveband by Gasparri and independently observed at the eyepiece – at the same hour – by G. Adamoli. The few positive AL sightings seem to be linked to solar Coronal Mass Ejection events. We review possible mechanisms to account for the AL.
So there will be quite a lot in print in due course. Meanwhile I remind all serious observers that the Ashen Light can only be searched for against a properly dark sky background, and that the declination at inferior conjunctions determines whether the northern or southern hemisphere will be suitable from which to make observations.
Richard McKim, Director25 May 2018 at 7:24 pm #579532MaksymowiczParticipant
Thanks a lot for the present input you brought here and the fact that Something had been collected visually and by Imaging in visual bands few years ago. This is an information for me. We were always on a controversial subject among the community.
Now, if the AL observation must be undertaken Under night conditions, with evidence this will avoid further discussions. Easy to understand.
However, we could do some analogy with the moon AL, bright Under a night sky. For the anecdote, recently on May the 21st, on daylight, on a transparent sky, the observation of the moon (1st quarter) with the naked eyes allows me to capture the main mare on the mare on the lighted side and some glow on the dark side. Not on the full portion but partially from the Terminator.
Indeed after the sun set time the dark side appears visually clearly also. Surely not the same mechanism of light creation than venus, but this mean some analogy regarding the light levels.
I suggest when somebody see such AL on Venus to practice an exercise consisting in occulting the lighted Crescent in order to fully occult it. The occulter can hide half the eyepiece FOV, so a free portion and the second fully occulted (a TP 2415 kodak film of density >5 located at the focus plan of the eyepice). A second observer can locate the planet behind the occulter, the first observer not knowing this and then try to find the AL not hidden. If well collected then move the scope in order to correlate with the lighted Crescent to see the direct correspondance. This is for avoiding the idea of brain construction of the AL by the lighted Crescent presence. I did personnally with succes.
All these manipulations and arguments donot conduct to built some mechanism of AL creation, but just hypothesis.
I am waiting your publication about the AL occurrences with interest.
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