Starmere Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starmere Observatory clear sky chart from 2005-11-06 to 2024-11-08.

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	15% 8% 3 7% 5% 4 5% 4 6% 7% 35%	101381
	Night	17% 9% 3 7% 5% 4 4 3 5% 6% 35%	97696
Transparency	Day	43% 9% 14% 21% 12% 1	104888
	Night	45% 8% 14% 21% 12% 1	102278
Seeing	Day	21% 16% 30% 21% 9% 2	14883
	Night	21% 14% 32% 26% 7% 1	23942

By Month

Percentage Cloud Cover NE (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	14% 11% 3 7% 5% 4 5% 4 6% 7% 34%	2517
	11th to 20th	Day	15% 12% 4 10% 6% 6% 6% 4 5% 6% 27%	2520
	21st to end	Day	18% 11% 4 9% 7% 6% 5% 4 6% 6% 26%	2882
February	1st to 10th	Day	15% 11% 4 8% 6% 6% 5% 5% 7% 6% 28%	1710
	11th to 20th	Day	12% 11% 4 8% 6% 5% 5% 4 5% 7% 33%	1835
	21st to end	Day	19% 9% 4 8% 6% 4 4 3 5% 6% 32%	1570
March	1st to 10th	Day	23% 14% 4 9% 5% 3 3 2 3 4 29%	3116
	11th to 20th	Day	12% 12% 4 8% 5% 5% 5% 4 5% 7% 33%	3288
	21st to end	Day	20% 8% 3 7% 4 4 4 3 4 6% 36%	4161
April	1st to 10th	Day	18% 10% 3 8% 5% 4 4 4 4 6% 35%	2280
	11th to 20th	Day	16% 7% 2 7% 5% 4 5% 3 5% 6% 39%	2254
	21st to end	Day	20% 6% 3 6% 5% 4 5% 3 6% 7% 35%	2356
May	1st to 10th	Day	23% 9% 2 7% 4 4 4 4 5% 7% 30%	4154
	11th to 20th	Day	18% 8% 3 7% 5% 5% 4 4 6% 7% 33%	4398
	21st to end	Day	12% 5% 2 5% 4 4 5% 5% 7% 9% 42%	4837
June	1st to 10th	Day	15% 7% 3 6% 5% 5% 6% 5% 6% 9% 34%	2660
	11th to 20th	Day	14% 6% 2 6% 5% 5% 5% 5% 7% 10% 35%	2660
	21st to end	Day	14% 6% 3 7% 5% 5% 6% 5% 7% 8% 35%	2660
July	1st to 10th	Day	9% 6% 2 7% 6% 5% 6% 5% 8% 10% 37%	4440
	11th to 20th	Day	9% 5% 2 6% 5% 5% 6% 4 8% 10% 38%	4440
	21st to end	Day	12% 6% 3 7% 6% 5% 5% 5% 7% 8% 34%	4814
August	1st to 10th	Day	15% 7% 3 8% 6% 5% 6% 4 6% 8% 31%	4347
	11th to 20th	Day	12% 7% 3 7% 5% 5% 5% 4 7% 10% 36%	3730
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 5% 6% 9% 41%	4180
September	1st to 10th	Day	13% 5% 2 7% 4 5% 5% 3 5% 7% 44%	2280
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 5% 7% 49%	2190
	21st to end	Day	15% 6% 2 5% 4 3 5% 4 6% 8% 41%	2090
October	1st to 10th	Day	20% 6% 3 7% 5% 4 5% 2 4 6% 38%	1990
	11th to 20th	Day	14% 8% 2 7% 4 3 4 3 5% 7% 42%	1900
	21st to end	Day	20% 9% 3 7% 5% 4 4 4 5% 6% 32%	1895
November	1st to 10th	Day	14% 8% 2 5% 4 4 3 4 5% 7% 44%	1734
	11th to 20th	Day	16% 8% 3 8% 5% 5% 4 3 6% 6% 37%	1710
	21st to end	Day	18% 9% 2 5% 5% 4 5% 4 6% 7% 35%	1585
December	1st to 10th	Day	17% 12% 4 8% 5% 5% 6% 5% 5% 6% 27%	1520
	11th to 20th	Day	23% 10% 4 7% 4 3 3 3 5% 5% 34%	1906
	21st to end	Day	24% 15% 4 9% 5% 4 3 3 5% 5% 23%	2772
January	1st to 10th	Night	15% 12% 4 8% 5% 4 4 3 4 5% 36%	4429
	11th to 20th	Night	13% 13% 5% 13% 6% 5% 4 3 4 6% 29%	4440
	21st to end	Night	23% 13% 4 8% 6% 4 4 3 5% 5% 26%	4756
February	1st to 10th	Night	16% 10% 3 9% 6% 5% 5% 4 5% 6% 31%	2470
	11th to 20th	Night	13% 11% 4 9% 6% 5% 5% 4 6% 6% 32%	2229
	21st to end	Night	18% 10% 3 7% 6% 4 5% 3 5% 6% 33%	1884
March	1st to 10th	Night	26% 10% 3 7% 5% 4 4 3 4 5% 30%	3724
	11th to 20th	Night	15% 13% 4 8% 5% 4 5% 4 5% 6% 32%	3653
	21st to end	Night	17% 12% 3 9% 5% 4 4 3 4 5% 35%	3471
April	1st to 10th	Night	17% 10% 4 8% 6% 4 5% 4 6% 7% 30%	1900
	11th to 20th	Night	21% 8% 3 6% 5% 4 3 3 5% 6% 37%	1875
	21st to end	Night	21% 7% 2 7% 4 3 4 3 6% 5% 38%	1823
May	1st to 10th	Night	23% 10% 3 7% 4 4 4 3 4 6% 31%	2815
	11th to 20th	Night	17% 10% 3 8% 5% 5% 5% 4 5% 6% 31%	2495
	21st to end	Night	12% 6% 2 7% 4 5% 5% 4 7% 8% 39%	2738
June	1st to 10th	Night	16% 6% 3 7% 4 3 4 4 6% 8% 39%	1520
	11th to 20th	Night	14% 7% 2 5% 5% 5% 4 4 7% 9% 39%	1520
	21st to end	Night	13% 5% 2 6% 4 5% 5% 4 6% 8% 42%	1520
July	1st to 10th	Night	12% 5% 2 6% 5% 5% 5% 5% 6% 9% 41%	2520
	11th to 20th	Night	13% 6% 2 7% 4 4 5% 3 7% 11% 36%	2520
	21st to end	Night	13% 7% 3 7% 5% 5% 5% 4 6% 7% 38%	2739
August	1st to 10th	Night	19% 7% 3 8% 5% 5% 4 4 6% 6% 35%	2535
	11th to 20th	Night	14% 7% 3 7% 4 4 5% 4 6% 8% 38%	3096
	21st to end	Night	11% 5% 2 7% 4 5% 4 3 5% 7% 46%	3476
September	1st to 10th	Night	14% 6% 2 6% 4 5% 4 3 6% 6% 41%	1900
	11th to 20th	Night	13% 5% 1 4 3 3 4 2 4 7% 54%	1990
	21st to end	Night	15% 6% 3 7% 4 4 4 3 5% 6% 43%	2090
October	1st to 10th	Night	19% 7% 2 7% 4 4 4 4 5% 6% 38%	2186
	11th to 20th	Night	15% 7% 2 6% 4 4 4 4 5% 6% 41%	2280
	21st to end	Night	23% 9% 2 6% 4 4 4 3 5% 6% 33%	2702
November	1st to 10th	Night	15% 7% 2 6% 4 4 3 3 6% 6% 43%	2505
	11th to 20th	Night	19% 8% 3 7% 5% 4 4 3 5% 6% 37%	2470
	21st to end	Night	16% 8% 3 7% 5% 5% 4 4 6% 6% 37%	2593
December	1st to 10th	Night	19% 11% 3 6% 6% 5% 5% 4 5% 7% 29%	2660
	11th to 20th	Night	21% 10% 4 8% 4 4 4 4 5% 6% 31%	3288
	21st to end	Night	23% 14% 4 9% 5% 5% 4 3 4 5% 24%	4884

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	43% 7% 18% 26% 6% 1	2518
	11th to 20th	Day	53% 9% 15% 18% 5% 1	2520
	21st to end	Day	56% 10% 10% 17% 6% 1	2882
February	1st to 10th	Day	52% 9% 13% 16% 9% 1	1710
	11th to 20th	Day	48% 8% 11% 20% 11% 2	1844
	21st to end	Day	50% 7% 12% 19% 11% 1	1570
March	1st to 10th	Day	56% 6% 13% 16% 8% 1	3119
	11th to 20th	Day	40% 12% 20% 19% 8% 1	3288
	21st to end	Day	45% 7% 10% 17% 19% 3	4161
April	1st to 10th	Day	49% 7% 10% 20% 11% 3	2280
	11th to 20th	Day	43% 7% 12% 20% 14% 2	2254
	21st to end	Day	46% 7% 11% 19% 14% 3	2356
May	1st to 10th	Day	51% 10% 12% 16% 10% 1	4168
	11th to 20th	Day	46% 10% 15% 19% 8% 1	4402
	21st to end	Day	32% 11% 16% 26% 14% 1	4837
June	1st to 10th	Day	44% 10% 15% 20% 11% 1	2660
	11th to 20th	Day	41% 11% 15% 21% 11% 1	2660
	21st to end	Day	44% 9% 14% 21% 11% 1	2660
July	1st to 10th	Day	39% 11% 14% 21% 14% 1	4370
	11th to 20th	Day	36% 11% 18% 23% 12%	4365
	21st to end	Day	44% 10% 16% 16% 14% 1	4661
August	1st to 10th	Day	47% 11% 16% 18% 8%	4333
	11th to 20th	Day	39% 10% 19% 26% 6%	3766
	21st to end	Day	34% 10% 16% 28% 11% 1	4180
September	1st to 10th	Day	39% 8% 13% 23% 15% 1	2280
	11th to 20th	Day	34% 7% 13% 24% 21% 2	2190
	21st to end	Day	38% 8% 15% 22% 14% 2	2090
October	1st to 10th	Day	39% 8% 10% 20% 21% 1	3302
	11th to 20th	Day	33% 6% 11% 27% 22% 1	3140
	21st to end	Day	35% 8% 14% 26% 14% 2	3095
November	1st to 10th	Day	38% 6% 16% 25% 14% 2	1734
	11th to 20th	Day	45% 7% 13% 19% 14% 2	1710
	21st to end	Day	45% 8% 16% 23% 8% 2	1585
December	1st to 10th	Day	54% 9% 15% 13% 9%	1520
	11th to 20th	Day	49% 8% 16% 20% 7% 1	1906
	21st to end	Day	59% 9% 12% 15% 5%	2772
January	1st to 10th	Night	45% 8% 15% 22% 8% 1	4429
	11th to 20th	Night	52% 9% 13% 16% 9% 1	4440
	21st to end	Night	57% 7% 11% 17% 7% 1	4756
February	1st to 10th	Night	51% 8% 13% 19% 8% 2	2470
	11th to 20th	Night	49% 7% 13% 18% 12% 1	2231
	21st to end	Night	48% 7% 14% 18% 9% 3	1884
March	1st to 10th	Night	53% 8% 10% 19% 9% 1	3734
	11th to 20th	Night	44% 12% 16% 19% 8% 1	3654
	21st to end	Night	47% 6% 9% 16% 18% 3	3471
April	1st to 10th	Night	52% 6% 12% 18% 11% 2	1900
	11th to 20th	Night	47% 6% 11% 19% 16% 1	1875
	21st to end	Night	47% 6% 10% 19% 14% 3	1823
May	1st to 10th	Night	53% 8% 11% 16% 10% 2	2821
	11th to 20th	Night	49% 11% 13% 17% 8% 2	2496
	21st to end	Night	37% 11% 16% 20% 14% 1	2739
June	1st to 10th	Night	41% 7% 13% 24% 12% 2	1520
	11th to 20th	Night	39% 11% 15% 23% 10%	1520
	21st to end	Night	37% 11% 15% 23% 14% 1	1520
July	1st to 10th	Night	38% 10% 16% 19% 16% 1	2480
	11th to 20th	Night	39% 10% 16% 22% 12%	2472
	21st to end	Night	43% 8% 15% 20% 13% 2	2651
August	1st to 10th	Night	47% 9% 16% 19% 9% 1	2525
	11th to 20th	Night	40% 10% 18% 24% 8%	3126
	21st to end	Night	32% 9% 16% 32% 11% 1	3476
September	1st to 10th	Night	40% 8% 12% 25% 15% 1	1900
	11th to 20th	Night	32% 6% 12% 26% 23% 1	1990
	21st to end	Night	39% 7% 12% 24% 18% 1	2090
October	1st to 10th	Night	42% 8% 13% 22% 14% 1	3654
	11th to 20th	Night	31% 7% 12% 26% 23%	3779
	21st to end	Night	36% 6% 14% 29% 14% 1	4452
November	1st to 10th	Night	38% 8% 12% 22% 17% 2	2505
	11th to 20th	Night	46% 6% 14% 20% 11% 3	2470
	21st to end	Night	44% 8% 18% 22% 7% 1	2593
December	1st to 10th	Night	50% 9% 15% 18% 8%	2660
	11th to 20th	Night	50% 8% 16% 15% 10% 1	3288
	21st to end	Night	55% 9% 14% 16% 6%	4884

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	26% 23% 33% 13% 5%	180
	11th to 20th	Day	27% 27% 32% 12% 3	180
	21st to end	Day	21% 26% 35% 14% 3 1	231
February	1st to 10th	Day	33% 24% 33% 8% 1	270
	11th to 20th	Day	27% 29% 31% 12% 1	443
	21st to end	Day	29% 24% 33% 12% 2	382
March	1st to 10th	Day	25% 22% 36% 15% 2	460
	11th to 20th	Day	24% 25% 33% 14% 2 1	460
	21st to end	Day	33% 20% 27% 12% 5% 2	506
April	1st to 10th	Day	30% 22% 27% 15% 6%	460
	11th to 20th	Day	26% 26% 27% 15% 5% 2	452
	21st to end	Day	27% 19% 32% 16% 5% 1	460
May	1st to 10th	Day	29% 18% 29% 17% 5% 2	463
	11th to 20th	Day	21% 15% 34% 21% 8% 1	487
	21st to end	Day	19% 11% 29% 27% 11% 3	529
June	1st to 10th	Day	19% 10% 32% 25% 12% 2	490
	11th to 20th	Day	16% 14% 30% 26% 11% 2	490
	21st to end	Day	16% 13% 32% 26% 12% 2	490
July	1st to 10th	Day	11% 8% 32% 29% 16% 3	485
	11th to 20th	Day	10% 6% 30% 34% 17% 2	484
	21st to end	Day	11% 8% 34% 30% 15% 2	532
August	1st to 10th	Day	10% 7% 29% 35% 15% 4	486
	11th to 20th	Day	14% 6% 27% 30% 17% 7%	479
	21st to end	Day	11% 9% 29% 29% 16% 6%	539
September	1st to 10th	Day	18% 9% 23% 30% 13% 7%	490
	11th to 20th	Day	13% 11% 27% 23% 15% 12%	490
	21st to end	Day	19% 10% 28% 26% 13% 4	490
October	1st to 10th	Day	22% 13% 25% 21% 13% 5%	490
	11th to 20th	Day	18% 16% 33% 22% 8% 2	490
	21st to end	Day	26% 14% 33% 19% 7% 1	436
November	1st to 10th	Day	21% 19% 28% 20% 10% 1	386
	11th to 20th	Day	22% 24% 30% 17% 6% 1	370
	21st to end	Day	26% 20% 30% 22% 2	245
December	1st to 10th	Day	23% 25% 32% 14% 6%	180
	11th to 20th	Day	27% 31% 29% 9% 3	180
	21st to end	Day	22% 21% 40% 14% 3 1	198
January	1st to 10th	Night	21% 17% 40% 20% 2	760
	11th to 20th	Night	24% 20% 35% 20% 1	760
	21st to end	Night	19% 20% 39% 20% 2	836
February	1st to 10th	Night	23% 18% 37% 21% 2	760
	11th to 20th	Night	23% 21% 40% 16%	743
	21st to end	Night	27% 18% 36% 17% 3	628
March	1st to 10th	Night	24% 20% 35% 18% 3	760
	11th to 20th	Night	22% 21% 38% 16% 3	760
	21st to end	Night	24% 22% 31% 18% 5%	836
April	1st to 10th	Night	23% 21% 32% 20% 3	760
	11th to 20th	Night	24% 17% 33% 19% 6%	751
	21st to end	Night	25% 16% 32% 22% 5%	683
May	1st to 10th	Night	24% 16% 32% 22% 6%	564
	11th to 20th	Night	19% 13% 37% 28% 4	374
	21st to end	Night	14% 10% 30% 36% 9%	411
June	1st to 10th	Night	16% 9% 32% 34% 9% 1	380
	11th to 20th	Night	16% 7% 31% 33% 12% 1	380
	21st to end	Night	13% 6% 27% 42% 12% 1	380
July	1st to 10th	Night	14% 4 22% 42% 17% 1	370
	11th to 20th	Night	13% 4 22% 42% 18% 1	368
	21st to end	Night	13% 5% 22% 46% 13% 1	416
August	1st to 10th	Night	11% 4 21% 47% 17% 2	394
	11th to 20th	Night	13% 4 19% 40% 21% 2	749
	21st to end	Night	14% 5% 23% 37% 19% 2	836
September	1st to 10th	Night	15% 6% 29% 34% 15% 1	760
	11th to 20th	Night	15% 8% 25% 28% 19% 4	760
	21st to end	Night	17% 8% 28% 34% 12% 2	760
October	1st to 10th	Night	23% 10% 24% 28% 13% 1	760
	11th to 20th	Night	18% 12% 33% 29% 8% 1	760
	21st to end	Night	27% 13% 31% 24% 4	836
November	1st to 10th	Night	20% 14% 33% 25% 7%	771
	11th to 20th	Night	24% 13% 35% 21% 7% 1	760
	21st to end	Night	19% 17% 35% 24% 5% 1	760
December	1st to 10th	Night	24% 18% 35% 18% 5%	760
	11th to 20th	Night	24% 18% 32% 24% 2	760
	21st to end	Night	27% 17% 36% 18% 2	836

Page generated at 2024-11-05 08:15:52. Version ac07

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