Hi all,
I have been rather limited lately in getting out and imaging due to looking after my wife who has just had knee surgery. There's not a lot of spare time when you throw in friends visiting.
Anyway, I did manage to get out on three separate occasions on the night of November 27th. The weather situation and forecast guidance promised very good conditions during the evening with light winds aloft - all having a similar direction and from a favourable direction. The guidance depicted the situation deteriorating by 2 to 3am, with a light northwesterly forecast to develop, especially in the few hours before dawn as winds strengthened further from the west to northwest which is not a good direction for me because of the turbulence induced by the ranges.
So, I set up in the late afternoon and my first test of the conditions was on Venus. At the time the air temperature and the ground temperature were only a couple of degrees apart (ground 24C and air 22C). Solar imagers tell me that they watch these temperatures after sunup and report that seeing gets markedly poorer after the ground temp rises above the air temperature (makes sense).
Anyway, here is a shot of Venus timed at 202411270646Z at an elevation of 44 degrees using a stack of 15,000 images.
On the whole I was fairly happy with this and looked forward to good seeing during the evening. Then my attention shifted to Saturn riding pretty high here at about 50 degrees or so. I could see the planet looked really good on the screen - I hadn't seen it that good for ages, in fact I was wondering if I would ever see good seeing again! I think my fellow Australian imagers have had a lot of poor weather lately.
So here is Saturn. This is a derotation using WinJuPos with 5 images of 10,000 frames each. It is timed at 202411270844Z with elevations varying from 50 to 43 degrees (past the meridian). I estimated the seeing at 7-8/10.
I'm quite pleased with this image. It's the best I have acquired in quite a while. Oddly enough, the colour channels behaved differently from what I usually record and the final colour palette is a little different - I don't know why. The sky looked pretty normal. The rings certainly show the darkening we've been discussing lately. Maybe the overall colour of the planet has shifted a bit.
Part of the plan was to catch Jupiter and Mars in the overnight period. Jupiter transited about 2.00 am at 27 degrees and Mars at 5:25 am at 28 degrees. So I left the gear setup and went out to grab a few images of Jupiter around 2 am. The low-level forecast wind conditions were forecast to gradually increase overnight and take up a light westerly flow at 2,500ft.
Well, I was a bit disappointed when I saw Jupiter. The planet was at about 27 degrees and located northwest towards the ranges. I think seeing was about 5-6/10. Location and elevation took its toll.
Here is a derotated image using 5 images totaling 50,000 images timed at 202411271326Z
I haven't had one decent image of Jupiter so far this season, but it is moving into the late evening sky.
Next was Mars. I haven't got anything of this planet either so far. I could see it rising out of the trees further to the north. I thought I should take a capture before I went back to bed. At 2:59 am I captured 80,00 frames in 4 minutes.
This Mars single image is timed at 202411271359Z using 10,000 frames with the planet at 19 degrees! This was better than I thought I might get at that elevation looking across houses. (Syrtis Major is visible.
Then I went back to bed and made another attempt around 5 am and the planet was a fuzz ball! There was a light wind affecting the telescope at times. So, the winds had increased as forecast. After daylight arrived and I got up, it was windy out.
I know the Jupiter and Mars images are not great but I thought they told a story about paying attention to the low-level winds especially if you have some terrain around you.
One last comment, I noticed that Sky Safari has a field called "Clear Air Turbulence" (CAT) and in my meteorological career we only ever dealt with
CAT at high levels. Then I noticed you could call a field located at 850 hPa or 5,000ft. I thought it would be interesting to follow, and so I am now collecting this field (along with 2,500ft winds, the wind sounding through the column and the MeteoBlue forecasts) in an effort to "calibrate" this CAT field to see if it adds any skill to assessing low level turbulence and therefore Seeing.
That's enough for now!
Cheers Paul
