ME Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the ME Observatory clear sky chart from 2005-11-06 to 2024-03-06.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	13% 5% 3 5% 5% 3 5% 5% 6% 8% 42%	78923
	Night	13% 6% 2 5% 5% 3 4 5% 5% 7% 45%	80597
Transparency	Day	38% 7% 12% 20% 18% 5%	78646
	Night	37% 7% 11% 19% 20% 6%	80393
Seeing	Day	15% 8% 20% 23% 21% 12%	13945
	Night	15% 8% 23% 29% 22% 4	24095

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	18% 9% 3 5% 5% 3 4 5% 5% 6% 37%	2836
	11th to 20th	Day	13% 5% 2 4 4 3 4 4 4 6% 51%	2840
	21st to end	Day	26% 6% 3 4 4 2 3 3 4 6% 40%	3224
February	1st to 10th	Day	16% 7% 3 7% 5% 3 5% 5% 4 7% 39%	1900
	11th to 20th	Day	22% 6% 2 4 3 2 4 4 4 6% 42%	1848
	21st to end	Day	20% 6% 3 5% 6% 2 4 5% 4 5% 39%	1570
March	1st to 10th	Day	14% 7% 2 4 5% 3 3 4 4 8% 46%	1914
	11th to 20th	Day	18% 6% 3 6% 5% 3 4 4 5% 7% 39%	1980
	21st to end	Day	16% 5% 2 6% 4 3 5% 5% 6% 8% 41%	2178
April	1st to 10th	Day	12% 5% 3 5% 5% 3 4 4 6% 7% 47%	2006
	11th to 20th	Day	13% 4 3 5% 5% 3 4 4 5% 7% 46%	2134
	21st to end	Day	10% 4 2 3 4 2 4 5% 5% 9% 52%	2315
May	1st to 10th	Day	9% 5% 3 4 4 3 4 5% 4 10% 51%	2340
	11th to 20th	Day	10% 6% 2 6% 5% 4 5% 5% 6% 10% 42%	2301
	21st to end	Day	9% 5% 2 5% 4 3 4 5% 7% 10% 44%	2531
June	1st to 10th	Day	9% 6% 2 5% 6% 4 5% 6% 7% 11% 38%	2340
	11th to 20th	Day	5% 3 2 4 5% 3 5% 6% 9% 12% 45%	2340
	21st to end	Day	6% 4 2 6% 7% 4 6% 7% 8% 11% 40%	2340
July	1st to 10th	Day	9% 5% 3 5% 6% 5% 8% 8% 8% 11% 32%	2340
	11th to 20th	Day	9% 5% 3 6% 6% 4 7% 7% 8% 13% 32%	2340
	21st to end	Day	6% 3 3 7% 7% 5% 8% 8% 9% 12% 32%	2547
August	1st to 10th	Day	7% 6% 2 6% 7% 5% 8% 8% 9% 11% 31%	2327
	11th to 20th	Day	10% 6% 3 7% 6% 4 6% 7% 8% 10% 33%	2180
	21st to end	Day	13% 7% 3 6% 6% 4 6% 7% 7% 9% 32%	2369
September	1st to 10th	Day	9% 6% 3 7% 5% 4 5% 5% 7% 9% 40%	1980
	11th to 20th	Day	14% 6% 3 5% 4 3 4 7% 6% 8% 41%	1980
	21st to end	Day	13% 5% 2 5% 5% 2 4 3 5% 6% 49%	1980
October	1st to 10th	Day	11% 5% 3 2 4 3 3 4 4 5% 55%	1980
	11th to 20th	Day	11% 4 1 4 4 2 3 4 5% 7% 55%	1868
	21st to end	Day	13% 4 1 4 4 2 3 4 5% 5% 54%	1980
November	1st to 10th	Day	11% 4 2 4 3 2 4 3 4 5% 57%	1708
	11th to 20th	Day	13% 5% 2 3 4 3 3 4 5% 6% 52%	1710
	21st to end	Day	14% 5% 3 4 4 3 4 4 5% 6% 47%	1710
December	1st to 10th	Day	20% 7% 3 5% 4 3 4 5% 5% 6% 38%	1710
	11th to 20th	Day	17% 7% 3 5% 5% 3 3 4 4 5% 44%	2153
	21st to end	Day	22% 6% 3 5% 4 3 4 4 5% 8% 36%	3124
January	1st to 10th	Night	18% 6% 2 5% 4 3 4 4 5% 7% 42%	4109
	11th to 20th	Night	12% 7% 3 5% 5% 3 5% 4 4 6% 46%	4120
	21st to end	Night	24% 8% 3 5% 4 2 3 3 4 4 40%	4428
February	1st to 10th	Night	16% 6% 3 5% 5% 2 4 4 4 6% 44%	2280
	11th to 20th	Night	20% 7% 3 5% 4 2 3 4 5% 4 43%	2218
	21st to end	Night	21% 6% 3 5% 4 3 3 3 5% 5% 41%	1884
March	1st to 10th	Night	14% 7% 3 5% 4 3 4 3 4 5% 49%	2161
	11th to 20th	Night	15% 6% 3 5% 4 3 4 5% 6% 8% 43%	1980
	21st to end	Night	14% 5% 2 4 5% 3 5% 5% 5% 7% 46%	2178
April	1st to 10th	Night	11% 5% 2 4 4 3 5% 5% 5% 8% 48%	1967
	11th to 20th	Night	13% 5% 2 3 4 2 4 4 5% 7% 51%	1775
	21st to end	Night	8% 5% 2 4 4 3 5% 4 5% 8% 54%	1643
May	1st to 10th	Night	9% 4 2 4 5% 3 4 5% 5% 8% 51%	1620
	11th to 20th	Night	8% 5% 3 6% 6% 4 5% 6% 6% 8% 45%	1592
	21st to end	Night	10% 5% 2 5% 5% 4 5% 5% 6% 8% 45%	1744
June	1st to 10th	Night	7% 5% 2 6% 5% 4 7% 8% 8% 11% 37%	1620
	11th to 20th	Night	4 3 2 4 6% 4 5% 6% 8% 13% 45%	1620
	21st to end	Night	6% 4 1 5% 5% 3 7% 8% 9% 11% 42%	1620
July	1st to 10th	Night	7% 5% 3 6% 7% 4 6% 7% 7% 14% 35%	1620
	11th to 20th	Night	6% 4 3 6% 6% 5% 7% 8% 9% 14% 32%	1620
	21st to end	Night	6% 4 2 7% 6% 4 8% 8% 8% 13% 33%	1771
August	1st to 10th	Night	7% 6% 2 6% 8% 4 6% 6% 9% 12% 34%	1611
	11th to 20th	Night	10% 4 3 7% 6% 3 5% 6% 9% 9% 38%	1715
	21st to end	Night	13% 7% 3 7% 6% 3 6% 6% 6% 9% 34%	1980
September	1st to 10th	Night	9% 4 3 5% 6% 4 5% 6% 7% 10% 43%	1967
	11th to 20th	Night	12% 6% 2 5% 4 3 4 6% 6% 7% 44%	1980
	21st to end	Night	11% 5% 2 5% 5% 3 4 5% 5% 8% 48%	1980
October	1st to 10th	Night	11% 4 2 4 4 2 3 4 5% 7% 53%	1980
	11th to 20th	Night	10% 4 2 4 5% 2 4 4 4 4 57%	2089
	21st to end	Night	12% 4 2 4 3 2 3 4 4 6% 57%	2376
November	1st to 10th	Night	12% 5% 1 3 3 2 3 3 4 5% 58%	2365
	11th to 20th	Night	15% 4 2 4 4 2 3 3 4 6% 54%	2470
	21st to end	Night	16% 5% 2 4 4 3 4 4 5% 6% 48%	2470
December	1st to 10th	Night	17% 6% 3 5% 5% 3 4 4 5% 6% 41%	2470
	11th to 20th	Night	17% 6% 2 4 4 2 3 3 4 6% 49%	3042
	21st to end	Night	19% 9% 3 6% 6% 3 4 5% 5% 7% 35%	4532

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	44% 6% 8% 15% 20% 6%	2837
	11th to 20th	Day	33% 4 8% 25% 24% 7%	2840
	21st to end	Day	47% 3 5% 17% 21% 7%	3224
February	1st to 10th	Day	45% 5% 8% 17% 20% 5%	1900
	11th to 20th	Day	44% 4 7% 18% 20% 6%	1858
	21st to end	Day	46% 5% 8% 15% 19% 8%	1570
March	1st to 10th	Day	38% 5% 10% 17% 22% 9%	1914
	11th to 20th	Day	44% 6% 12% 15% 17% 6%	1980
	21st to end	Day	41% 6% 11% 22% 17% 4	2178
April	1st to 10th	Day	37% 5% 9% 23% 20% 5%	2006
	11th to 20th	Day	37% 6% 8% 19% 23% 7%	2134
	21st to end	Day	29% 6% 12% 29% 22% 3	2315
May	1st to 10th	Day	30% 7% 14% 23% 23% 3	2340
	11th to 20th	Day	38% 8% 16% 22% 14% 1	2305
	21st to end	Day	33% 8% 14% 26% 17% 1	2531
June	1st to 10th	Day	39% 10% 18% 23% 9% 2	2340
	11th to 20th	Day	27% 11% 24% 24% 12% 1	2340
	21st to end	Day	34% 11% 17% 24% 12% 2	2340
July	1st to 10th	Day	40% 13% 20% 18% 8% 2	2275
	11th to 20th	Day	40% 14% 21% 15% 7% 3	2271
	21st to end	Day	38% 15% 20% 20% 7%	2405
August	1st to 10th	Day	41% 14% 19% 21% 5%	2314
	11th to 20th	Day	43% 13% 17% 16% 9% 2	2180
	21st to end	Day	45% 11% 15% 16% 11% 2	2369
September	1st to 10th	Day	38% 9% 17% 16% 17% 4	1980
	11th to 20th	Day	38% 10% 12% 17% 22% 2	1980
	21st to end	Day	36% 5% 11% 20% 22% 6%	1980
October	1st to 10th	Day	31% 5% 10% 17% 29% 7%	1980
	11th to 20th	Day	29% 4 10% 24% 25% 8%	1868
	21st to end	Day	31% 4 6% 18% 30% 10%	1980
November	1st to 10th	Day	30% 4 8% 15% 31% 11%	1708
	11th to 20th	Day	32% 5% 7% 19% 27% 10%	1710
	21st to end	Day	36% 6% 7% 19% 25% 7%	1710
December	1st to 10th	Day	47% 6% 6% 19% 16% 6%	1710
	11th to 20th	Day	43% 4 6% 15% 24% 8%	2150
	21st to end	Day	43% 6% 11% 18% 19% 3	3124
January	1st to 10th	Night	39% 6% 8% 16% 25% 6%	4109
	11th to 20th	Night	38% 5% 6% 22% 20% 8%	4120
	21st to end	Night	48% 4 5% 12% 25% 6%	4428
February	1st to 10th	Night	42% 4 8% 17% 20% 9%	2280
	11th to 20th	Night	44% 4 5% 17% 21% 9%	2219
	21st to end	Night	45% 4 8% 15% 18% 10%	1884
March	1st to 10th	Night	38% 4 8% 17% 21% 12%	2161
	11th to 20th	Night	38% 7% 12% 16% 20% 7%	1980
	21st to end	Night	37% 6% 9% 22% 22% 5%	2178
April	1st to 10th	Night	32% 6% 11% 20% 23% 8%	1967
	11th to 20th	Night	33% 3 9% 21% 24% 10%	1775
	21st to end	Night	29% 6% 11% 27% 22% 6%	1643
May	1st to 10th	Night	32% 6% 13% 21% 23% 4	1620
	11th to 20th	Night	36% 9% 16% 22% 15% 2	1593
	21st to end	Night	35% 9% 12% 23% 17% 3	1745
June	1st to 10th	Night	37% 12% 17% 21% 11% 2	1620
	11th to 20th	Night	28% 9% 22% 27% 12% 2	1620
	21st to end	Night	30% 13% 22% 19% 12% 3	1620
July	1st to 10th	Night	37% 13% 20% 20% 8% 2	1575
	11th to 20th	Night	34% 15% 24% 15% 9% 2	1566
	21st to end	Night	35% 14% 23% 19% 7% 2	1672
August	1st to 10th	Night	38% 15% 18% 23% 6% 1	1600
	11th to 20th	Night	38% 13% 18% 17% 13% 1	1715
	21st to end	Night	43% 11% 17% 17% 10% 2	1980
September	1st to 10th	Night	34% 11% 16% 17% 17% 4	1967
	11th to 20th	Night	36% 10% 11% 20% 19% 3	1980
	21st to end	Night	34% 7% 11% 18% 21% 8%	1980
October	1st to 10th	Night	30% 6% 11% 17% 27% 7%	1980
	11th to 20th	Night	31% 5% 7% 21% 27% 10%	2089
	21st to end	Night	29% 4 6% 18% 30% 13%	2376
November	1st to 10th	Night	30% 4 7% 18% 27% 14%	2365
	11th to 20th	Night	33% 3 6% 18% 27% 13%	2470
	21st to end	Night	36% 5% 8% 18% 25% 8%	2470
December	1st to 10th	Night	42% 6% 8% 20% 19% 6%	2470
	11th to 20th	Night	37% 4 8% 16% 28% 7%	3044
	21st to end	Night	47% 6% 8% 20% 17% 3	4532

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	22% 19% 39% 18% 1	270
	11th to 20th	Day	19% 25% 27% 19% 8% 1	270
	21st to end	Day	22% 21% 37% 15% 4 1	297
February	1st to 10th	Day	21% 18% 33% 22% 5%	270
	11th to 20th	Day	35% 17% 29% 17% 2	270
	21st to end	Day	25% 21% 35% 16% 2	225
March	1st to 10th	Day	22% 13% 29% 26% 9% 1	319
	11th to 20th	Day	21% 16% 31% 24% 8% 1	420
	21st to end	Day	20% 14% 31% 25% 10% 1	462
April	1st to 10th	Day	16% 15% 27% 26% 14% 2	420
	11th to 20th	Day	12% 14% 29% 24% 19% 2	412
	21st to end	Day	15% 9% 24% 27% 20% 5%	420
May	1st to 10th	Day	12% 8% 27% 27% 20% 6%	423
	11th to 20th	Day	13% 3 19% 26% 25% 15%	447
	21st to end	Day	14% 2 13% 25% 28% 18%	485
June	1st to 10th	Day	13% 2 10% 27% 29% 19%	450
	11th to 20th	Day	7% 2 13% 25% 23% 30%	450
	21st to end	Day	9% 4 10% 28% 29% 20%	450
July	1st to 10th	Day	10% 2 4 22% 30% 31%	445
	11th to 20th	Day	8% 1 7% 19% 31% 34%	444
	21st to end	Day	6% 2 6% 19% 40% 27%	488
August	1st to 10th	Day	12% 2 12% 22% 27% 26%	446
	11th to 20th	Day	12% 1 8% 20% 36% 24%	439
	21st to end	Day	16% 2 8% 22% 29% 23%	495
September	1st to 10th	Day	10% 3 12% 24% 32% 19%	450
	11th to 20th	Day	15% 3 10% 22% 34% 16%	450
	21st to end	Day	14% 3 14% 24% 34% 11%	450
October	1st to 10th	Day	14% 4 18% 30% 22% 11%	450
	11th to 20th	Day	12% 8% 25% 24% 24% 8%	450
	21st to end	Day	18% 7% 21% 29% 22% 4	495
November	1st to 10th	Day	18% 7% 25% 26% 18% 5%	306
	11th to 20th	Day	15% 13% 36% 25% 9% 1	270
	21st to end	Day	11% 15% 32% 27% 13% 2	270
December	1st to 10th	Day	28% 15% 31% 19% 6% 1	270
	11th to 20th	Day	22% 15% 31% 25% 6% 1	270
	21st to end	Day	28% 16% 30% 19% 5% 2	297
January	1st to 10th	Night	24% 14% 33% 23% 5%	760
	11th to 20th	Night	19% 15% 32% 25% 9%	760
	21st to end	Night	20% 16% 36% 25% 3	836
February	1st to 10th	Night	18% 13% 32% 31% 6%	760
	11th to 20th	Night	22% 14% 35% 25% 3	743
	21st to end	Night	22% 15% 35% 25% 3	628
March	1st to 10th	Night	17% 12% 34% 32% 5%	743
	11th to 20th	Night	17% 11% 35% 27% 11%	720
	21st to end	Night	17% 11% 28% 32% 11%	792
April	1st to 10th	Night	13% 12% 29% 32% 13% 1	707
	11th to 20th	Night	14% 9% 28% 33% 16% 1	533
	21st to end	Night	11% 7% 24% 35% 21% 2	540
May	1st to 10th	Night	10% 7% 25% 36% 21% 1	540
	11th to 20th	Night	10% 4 22% 33% 26% 5%	531
	21st to end	Night	12% 1 11% 32% 37% 7%	584
June	1st to 10th	Night	9% 1 9% 38% 35% 7%	540
	11th to 20th	Night	5% 1 14% 30% 36% 14%	540
	21st to end	Night	8% 1 8% 31% 41% 11%	540
July	1st to 10th	Night	10% 2 5% 23% 44% 15%	525
	11th to 20th	Night	6% 2 7% 18% 52% 15%	522
	21st to end	Night	7% 1 6% 24% 51% 11%	591
August	1st to 10th	Night	9% 2 6% 26% 44% 12%	537
	11th to 20th	Night	11% 1 7% 26% 44% 10%	534
	21st to end	Night	14% 2 7% 26% 41% 9%	594
September	1st to 10th	Night	9% 2 7% 26% 44% 11%	707
	11th to 20th	Night	14% 2 10% 27% 42% 5%	720
	21st to end	Night	13% 3 12% 33% 36% 3	720
October	1st to 10th	Night	13% 3 18% 32% 27% 7%	720
	11th to 20th	Night	12% 5% 24% 33% 22% 3	720
	21st to end	Night	14% 6% 22% 34% 20% 3	792
November	1st to 10th	Night	15% 7% 22% 32% 23% 1	740
	11th to 20th	Night	17% 9% 31% 28% 15% 1	760
	21st to end	Night	18% 8% 28% 31% 15% 1	760
December	1st to 10th	Night	18% 12% 31% 29% 10% 1	760
	11th to 20th	Night	22% 10% 30% 28% 10% 1	760
	21st to end	Night	25% 12% 28% 28% 7%	836

Page generated at 2024-03-03 06:28:55. Version ac07

Copyright © 2024 Attilla Danko.