Beauty of sky

Total lunar eclipse, 28.09.2015, Cambridge (England)

This lunar eclipse was exeptional, because the event happened during the full supermoon. For next lunar eclipse like this we need to wait until 2033. I was watching on the Moon during the night between 27 and 28.09.2015. Due to my poor equipment I couldn't aim at Moon's disk and snap a nice seas, mountains and craters. I decided to look for this phenomenon from the different angle, namely capture how the light is diminishing. I was gonna to set the moments, when it starts getting dark during the partial lunar eclipse. I put together all my bracketed photos with the Earth's shadow patterns below. I was taking the pictures in 5 directions in around 10-15 minutes intervals. I framed the characteristic portions of my view: south-south west (SWS), west-south west (WNW), north west (NW), south east (SE) and south (S). Just after the mid-eclipse I terminated my observation because fog was coming from the city centre.

My observation point was situated on the hill just outside the city. I was staging my pictures on fields on both sides of Limekiln Road. The hills east of Cambridge raise up to 60m above Cambridge bottomland. Under the normal conditions this is a quite good vantage point e.g Little Trees Hill opposite to the Wandlebury Park.
Basically I was situated at least 1.5km from the nearest illuminated areas and around 6km from the city centre. Thanks to this I would enjoy far better conditions to watching the lunar eclipse.

The weather was fine. There were a few high-altitude clouds (cirrus) drifting across the sky and briefly veiling the Moon sometimes. As the Earth's shadow shallow more and more of the Moon's disk the weather was worsen due to fog coming frim the river Cam valley. At the beginning of my observation the Moon was shining on the south west.

I had commenced the observation at 1.12 BST (UTC+1), when the first contact occured up to mid-eclipse at. 3:47 BST (UTC +1). Finally I put together 10 moments of this celestial event. To simulate the eclipse phenomenon I used an open-source software Cartes du Ciel Sky Charts ver.3.1.
The whole observation imagery has been uploaded as an movie file, which you can see below:

To know what time the pictures were captured you need to refer to the big attachment below. There you can find a few rows, which represent each aforementioned direction:
- 1st row contains observation towards south west, the actual Moon position,
- 2nd row represents view towards Addenbrooke's Hospital, west-north west,
- 3rd row is the Cartes du Ciel simulation,
- 4th row shows the pictures headed south,
- 5th row includes the photos of the south east part of the horizon,
- 6th row is another Cartes du Ciel simulation with more zoom into the Moon,
- 7th row is the last and displays the north west portion of the surrounding with city glow beyond. The observation in this direction started 20 minutes after 1st contact.

Next picture includes the eclipsed Moon observation. Due to poor quality of my photos made by simple compact camera the Silver Globe does not display many details of the surface.

In order to clearly show of the light decreasing I cropped a small portion of the sky from 4 directions and a smallish pieces of the horizon to compare the moonlight with light glow.


When I gathered those cropped images I put them together and finally recieved the light decreasing compilation. The initial part of the observation was interrupted by cirrus clouds spoiling the Moon. Hence second attempt looks slightly brighter.

I would also see the moment when the moonlight is equal a light glow seen above the horizon. Usually it depends of the city size and distance. In my case I saw the lights produced by a small towns with around 5k inhabitants situated around 15km from the observation point.

Conclusions

1. When the lunar disk is cover in around 65-70% by prenumbra it starts getting darker.
2. There is no big difference in the lunar light density between 65-70% Moon umbra's obscuration and total phase.
3. The prenumbra presence on the 65-70% lunar disk sets the moment, when the light glow is equal with moonlight in case of long distance to the city glow.

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