Stirling-Rawdon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stirling-Rawdon clear sky chart from 2005-11-06 to 2024-02-05.

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	17% 9% 4 7% 6% 3 5% 5% 5% 6% 34%	78140
	Night	17% 10% 4 7% 6% 3 5% 4 5% 6% 33%	80711
Transparency	Day	51% 3 11% 22% 11% 1	77846
	Night	52% 3 12% 21% 11% 1	80539
Seeing	Day	24% 14% 31% 19% 9% 3	13404
	Night	22% 13% 29% 24% 10% 1	22808

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	17% 15% 5% 8% 6% 3 3 3 4 5% 30%	2517
	11th to 20th	Day	13% 17% 6% 12% 8% 4 5% 4 4 4 22%	2520
	21st to end	Day	20% 19% 6% 11% 6% 3 4 4 3 3 20%	3124
February	1st to 10th	Day	15% 14% 5% 11% 8% 4 5% 5% 5% 5% 23%	1656
	11th to 20th	Day	13% 15% 6% 10% 8% 4 4 4 4 4 27%	1573
	21st to end	Day	20% 14% 6% 8% 6% 4 5% 4 4 5% 25%	1422
March	1st to 10th	Day	16% 11% 4 8% 7% 4 5% 4 5% 6% 30%	1900
	11th to 20th	Day	15% 14% 4 8% 6% 4 4 3 4 5% 33%	1980
	21st to end	Day	20% 10% 3 6% 4 3 3 4 4 5% 38%	2222
April	1st to 10th	Day	21% 12% 4 6% 5% 3 4 4 4 6% 32%	2160
	11th to 20th	Day	22% 8% 2 4 4 3 5% 3 4 6% 40%	2134
	21st to end	Day	21% 9% 3 7% 6% 3 5% 4 4 5% 33%	2312
May	1st to 10th	Day	18% 7% 3 6% 7% 3 5% 5% 5% 6% 35%	2452
	11th to 20th	Day	15% 6% 4 6% 4 4 4 5% 6% 7% 40%	2478
	21st to end	Day	13% 5% 2 6% 5% 3 5% 5% 6% 8% 41%	2725
June	1st to 10th	Day	18% 6% 3 6% 5% 4 5% 5% 6% 7% 33%	2520
	11th to 20th	Day	14% 5% 3 6% 5% 3 6% 5% 6% 9% 39%	2520
	21st to end	Day	16% 7% 3 6% 5% 3 5% 5% 6% 8% 36%	2520
July	1st to 10th	Day	11% 4 2 5% 5% 4 6% 6% 6% 8% 43%	2520
	11th to 20th	Day	11% 6% 2 5% 6% 4 5% 6% 7% 8% 40%	2520
	21st to end	Day	10% 5% 2 6% 6% 4 6% 7% 7% 9% 37%	2733
August	1st to 10th	Day	10% 5% 2 6% 5% 3 5% 6% 7% 10% 40%	2327
	11th to 20th	Day	11% 6% 3 5% 6% 3 6% 6% 6% 7% 39%	2303
	21st to end	Day	13% 6% 2 6% 5% 3 5% 5% 6% 9% 40%	2408
September	1st to 10th	Day	13% 5% 2 5% 6% 4 5% 5% 6% 8% 43%	2160
	11th to 20th	Day	11% 5% 2 5% 5% 3 4 5% 6% 8% 48%	2160
	21st to end	Day	16% 6% 2 6% 5% 3 4 4 5% 7% 40%	1882
October	1st to 10th	Day	19% 8% 4 6% 6% 3 5% 5% 4 7% 34%	1800
	11th to 20th	Day	23% 8% 3 7% 5% 4 5% 4 6% 7% 29%	1800
	21st to end	Day	26% 10% 3 7% 5% 3 5% 4 4 6% 26%	1940
November	1st to 10th	Day	15% 8% 4 6% 6% 3 5% 4 6% 7% 35%	1614
	11th to 20th	Day	17% 11% 3 8% 7% 3 4 5% 6% 6% 30%	1520
	21st to end	Day	21% 13% 4 8% 7% 2 5% 4 6% 5% 25%	1520
December	1st to 10th	Day	19% 16% 5% 9% 6% 5% 5% 4 5% 5% 21%	1520
	11th to 20th	Day	20% 13% 6% 8% 5% 3 4 4 4 5% 28%	1906
	21st to end	Day	29% 14% 5% 8% 5% 3 4 3 3 5% 21%	2772
January	1st to 10th	Night	19% 14% 6% 9% 7% 4 5% 4 4 5% 22%	4429
	11th to 20th	Night	15% 13% 7% 10% 9% 4 6% 5% 4 5% 22%	4436
	21st to end	Night	19% 15% 7% 9% 7% 4 5% 5% 4 5% 22%	4532
February	1st to 10th	Night	15% 14% 5% 9% 8% 4 5% 4 5% 6% 26%	2399
	11th to 20th	Night	15% 13% 6% 8% 6% 4 5% 5% 5% 5% 29%	2273
	21st to end	Night	16% 12% 3 8% 6% 3 4 4 6% 6% 31%	1834
March	1st to 10th	Night	15% 10% 4 6% 7% 4 5% 5% 5% 6% 33%	2042
	11th to 20th	Night	17% 12% 4 7% 5% 3 4 3 4 5% 35%	1979
	21st to end	Night	17% 7% 3 6% 6% 3 5% 4 4 6% 40%	2134
April	1st to 10th	Night	19% 9% 4 6% 5% 3 4 4 5% 6% 36%	1800
	11th to 20th	Night	18% 8% 3 6% 5% 3 4 5% 4 5% 38%	1775
	21st to end	Night	19% 8% 3 6% 4 3 4 6% 6% 7% 33%	1663
May	1st to 10th	Night	19% 6% 2 7% 5% 3 4 4 5% 6% 37%	1508
	11th to 20th	Night	13% 6% 2 5% 5% 3 4 5% 7% 8% 43%	1415
	21st to end	Night	10% 5% 2 5% 5% 3 5% 4 5% 7% 49%	1550
June	1st to 10th	Night	15% 6% 2 5% 6% 3 5% 5% 5% 9% 38%	1440
	11th to 20th	Night	11% 5% 3 5% 7% 3 4 5% 6% 7% 44%	1440
	21st to end	Night	14% 6% 2 5% 6% 3 4 4 6% 8% 43%	1440
July	1st to 10th	Night	7% 4 2 5% 6% 3 4 4 6% 8% 51%	1440
	11th to 20th	Night	10% 5% 2 4 5% 3 5% 5% 5% 9% 46%	1440
	21st to end	Night	10% 4 2 4 5% 2 4 5% 7% 8% 49%	1582
August	1st to 10th	Night	8% 5% 3 6% 5% 3 3 4 6% 8% 49%	1611
	11th to 20th	Night	9% 5% 2 5% 5% 4 5% 4 6% 9% 46%	1598
	21st to end	Night	9% 5% 3 6% 5% 3 4 5% 6% 8% 47%	1930
September	1st to 10th	Night	11% 6% 2 5% 4 4 4 4 6% 8% 45%	1800
	11th to 20th	Night	12% 4 2 3 4 3 4 4 5% 7% 52%	1800
	21st to end	Night	17% 5% 3 6% 4 3 5% 4 4 6% 43%	2073
October	1st to 10th	Night	18% 7% 3 6% 5% 3 6% 5% 5% 6% 38%	2160
	11th to 20th	Night	22% 8% 3 7% 6% 3 5% 4 4 6% 32%	2160
	21st to end	Night	23% 10% 3 7% 6% 3 4 5% 5% 6% 28%	2416
November	1st to 10th	Night	19% 7% 3 5% 5% 3 4 4 5% 7% 38%	2460
	11th to 20th	Night	18% 10% 4 6% 6% 3 5% 4 6% 7% 32%	2660
	21st to end	Night	21% 11% 3 6% 6% 3 5% 5% 6% 7% 27%	2660
December	1st to 10th	Night	22% 13% 4 8% 6% 3 5% 5% 6% 7% 21%	2660
	11th to 20th	Night	20% 14% 4 8% 6% 3 4 4 3 5% 28%	3288
	21st to end	Night	30% 16% 4 8% 6% 3 4 4 4 5% 16%	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	58% 2 15% 17% 7% 2	2518
	11th to 20th	Day	67% 2 11% 12% 8%	2520
	21st to end	Day	71% 2 8% 12% 5% 1	3124
February	1st to 10th	Day	63% 3 9% 18% 6% 1	1656
	11th to 20th	Day	61% 2 7% 16% 11% 2	1582
	21st to end	Day	64% 2 7% 15% 11% 1	1422
March	1st to 10th	Day	55% 3 14% 16% 11% 2	1903
	11th to 20th	Day	55% 2 10% 19% 12% 2	1980
	21st to end	Day	51% 3 6% 21% 15% 5%	2222
April	1st to 10th	Day	55% 2 7% 21% 12% 3	2160
	11th to 20th	Day	48% 2 8% 24% 17% 1	2134
	21st to end	Day	55% 2 7% 19% 14% 3	2312
May	1st to 10th	Day	50% 3 9% 20% 16% 3	2452
	11th to 20th	Day	44% 3 9% 26% 16% 2	2482
	21st to end	Day	42% 4 15% 22% 15% 2	2725
June	1st to 10th	Day	48% 4 12% 20% 15% 2	2520
	11th to 20th	Day	42% 3 12% 26% 15% 2	2520
	21st to end	Day	45% 4 13% 24% 13% 1	2520
July	1st to 10th	Day	37% 4 11% 29% 17% 1	2450
	11th to 20th	Day	39% 4 16% 31% 11%	2445
	21st to end	Day	42% 5% 14% 26% 12% 1	2580
August	1st to 10th	Day	38% 4 16% 28% 12% 1	2314
	11th to 20th	Day	42% 4 15% 27% 12% 1	2303
	21st to end	Day	41% 4 12% 30% 12% 1	2408
September	1st to 10th	Day	39% 4 13% 30% 13% 1	2160
	11th to 20th	Day	35% 3 13% 33% 16% 1	2160
	21st to end	Day	44% 4 13% 30% 9%	1882
October	1st to 10th	Day	51% 3 11% 22% 12% 1	1800
	11th to 20th	Day	54% 4 13% 20% 7% 1	1800
	21st to end	Day	61% 2 10% 18% 9%	1940
November	1st to 10th	Day	49% 3 15% 23% 10% 1	1614
	11th to 20th	Day	55% 3 12% 18% 11% 1	1520
	21st to end	Day	61% 4 12% 15% 8%	1520
December	1st to 10th	Day	65% 3 12% 14% 6%	1520
	11th to 20th	Day	61% 4 12% 14% 8%	1906
	21st to end	Day	69% 2 8% 14% 6%	2772
January	1st to 10th	Night	65% 1 13% 15% 5%	4429
	11th to 20th	Night	65% 2 12% 15% 5% 1	4436
	21st to end	Night	66% 2 11% 14% 6% 1	4532
February	1st to 10th	Night	61% 3 10% 19% 7% 1	2399
	11th to 20th	Night	58% 3 8% 21% 10% 1	2275
	21st to end	Night	54% 3 11% 21% 11% 1	1834
March	1st to 10th	Night	52% 3 10% 21% 12% 2	2052
	11th to 20th	Night	53% 2 10% 22% 11% 1	1980
	21st to end	Night	47% 2 7% 23% 17% 4	2134
April	1st to 10th	Night	51% 3 7% 23% 14% 3	1800
	11th to 20th	Night	49% 3 8% 21% 18% 2	1775
	21st to end	Night	49% 4 10% 18% 16% 3	1663
May	1st to 10th	Night	48% 3 7% 21% 17% 4	1508
	11th to 20th	Night	39% 3 9% 28% 17% 3	1416
	21st to end	Night	37% 2 16% 21% 20% 4	1551
June	1st to 10th	Night	44% 3 12% 25% 15% 1	1440
	11th to 20th	Night	39% 3 12% 23% 21% 3	1440
	21st to end	Night	41% 3 15% 26% 14% 2	1440
July	1st to 10th	Night	31% 5% 12% 28% 22% 3	1400
	11th to 20th	Night	35% 4 12% 32% 16%	1392
	21st to end	Night	33% 3 16% 35% 13% 1	1494
August	1st to 10th	Night	34% 4 17% 31% 13% 1	1600
	11th to 20th	Night	36% 4 17% 28% 14% 2	1598
	21st to end	Night	35% 5% 12% 33% 15% 1	1930
September	1st to 10th	Night	38% 4 15% 28% 15% 1	1800
	11th to 20th	Night	33% 3 14% 34% 16% 1	1800
	21st to end	Night	43% 3 11% 30% 13% 1	2073
October	1st to 10th	Night	48% 4 10% 24% 14% 1	2160
	11th to 20th	Night	55% 2 11% 22% 9%	2160
	21st to end	Night	57% 4 12% 16% 11%	2416
November	1st to 10th	Night	48% 3 12% 25% 12% 1	2460
	11th to 20th	Night	52% 3 13% 20% 11% 2	2660
	21st to end	Night	56% 4 15% 18% 6%	2660
December	1st to 10th	Night	62% 3 12% 18% 5%	2660
	11th to 20th	Night	60% 3 12% 17% 7% 1	3288
	21st to end	Night	72% 2 10% 12% 4	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	27% 21% 32% 14% 4 1	180
	11th to 20th	Day	34% 18% 29% 15% 3 1	180
	21st to end	Day	31% 20% 31% 13% 4 1	297
February	1st to 10th	Day	34% 24% 32% 9% 1	252
	11th to 20th	Day	30% 26% 35% 8% 1	240
	21st to end	Day	38% 19% 34% 8% 1	288
March	1st to 10th	Day	26% 20% 34% 15% 4	420
	11th to 20th	Day	30% 18% 33% 15% 4	420
	21st to end	Day	35% 16% 29% 13% 6% 1	462
April	1st to 10th	Day	32% 17% 33% 11% 6%	420
	11th to 20th	Day	33% 17% 23% 15% 8% 4	412
	21st to end	Day	30% 20% 32% 12% 4 2	420
May	1st to 10th	Day	27% 15% 29% 19% 6% 5%	423
	11th to 20th	Day	21% 13% 34% 21% 7% 3	447
	21st to end	Day	18% 14% 35% 18% 12% 4	485
June	1st to 10th	Day	22% 12% 36% 21% 8% 2	450
	11th to 20th	Day	16% 14% 32% 23% 12% 3	450
	21st to end	Day	22% 12% 29% 24% 11% 2	450
July	1st to 10th	Day	12% 8% 29% 31% 15% 4	445
	11th to 20th	Day	16% 9% 29% 26% 15% 5%	444
	21st to end	Day	12% 9% 38% 26% 11% 4	488
August	1st to 10th	Day	11% 7% 31% 29% 15% 7%	446
	11th to 20th	Day	14% 6% 28% 28% 17% 7%	439
	21st to end	Day	16% 9% 30% 24% 13% 8%	495
September	1st to 10th	Day	14% 9% 33% 24% 11% 8%	450
	11th to 20th	Day	14% 7% 30% 24% 17% 10%	450
	21st to end	Day	18% 13% 27% 24% 12% 6%	450
October	1st to 10th	Day	27% 14% 24% 17% 13% 5%	450
	11th to 20th	Day	29% 15% 33% 15% 6% 2	450
	21st to end	Day	32% 16% 28% 20% 4	475
November	1st to 10th	Day	28% 17% 26% 19% 10% 1	308
	11th to 20th	Day	31% 20% 31% 13% 4 1	180
	21st to end	Day	30% 19% 33% 13% 4 1	180
December	1st to 10th	Day	33% 14% 33% 17% 3	180
	11th to 20th	Day	36% 22% 29% 10% 3 1	180
	21st to end	Day	39% 18% 32% 9% 2 1	198
January	1st to 10th	Night	29% 18% 30% 18% 4 1	760
	11th to 20th	Night	29% 18% 28% 19% 6%	760
	21st to end	Night	23% 16% 33% 23% 4 1	836
February	1st to 10th	Night	25% 20% 33% 20% 2	739
	11th to 20th	Night	24% 21% 34% 17% 4	703
	21st to end	Night	26% 20% 34% 18% 3	592
March	1st to 10th	Night	23% 17% 36% 20% 3	720
	11th to 20th	Night	27% 17% 31% 20% 4 1	720
	21st to end	Night	23% 16% 31% 23% 7% 1	792
April	1st to 10th	Night	25% 17% 31% 23% 4	720
	11th to 20th	Night	25% 20% 26% 21% 8% 1	711
	21st to end	Night	24% 13% 30% 23% 10% 1	583
May	1st to 10th	Night	23% 10% 27% 26% 13% 2	428
	11th to 20th	Night	17% 9% 34% 30% 10%	354
	21st to end	Night	12% 8% 33% 31% 14% 1	389
June	1st to 10th	Night	16% 8% 33% 31% 12% 1	360
	11th to 20th	Night	14% 9% 31% 30% 15% 1	360
	21st to end	Night	16% 7% 26% 35% 15% 1	360
July	1st to 10th	Night	7% 5% 29% 43% 16% 1	350
	11th to 20th	Night	11% 1 30% 36% 20% 1	348
	21st to end	Night	11% 2 31% 40% 16% 1	402
August	1st to 10th	Night	10% 3 24% 34% 26% 3	537
	11th to 20th	Night	10% 5% 21% 37% 24% 3	534
	21st to end	Night	12% 5% 28% 33% 19% 2	742
September	1st to 10th	Night	14% 6% 28% 32% 18% 3	720
	11th to 20th	Night	14% 6% 24% 26% 26% 4	720
	21st to end	Night	20% 9% 22% 27% 19% 3	720
October	1st to 10th	Night	22% 11% 26% 23% 16% 2	720
	11th to 20th	Night	26% 12% 30% 22% 9%	720
	21st to end	Night	30% 14% 29% 23% 5%	792
November	1st to 10th	Night	27% 11% 25% 27% 10% 1	740
	11th to 20th	Night	25% 18% 29% 20% 7% 1	760
	21st to end	Night	29% 16% 28% 21% 6%	760
December	1st to 10th	Night	31% 17% 29% 19% 4	760
	11th to 20th	Night	28% 18% 33% 18% 4	760
	21st to end	Night	36% 15% 31% 16% 2	836

Page generated at 2024-02-02 05:20:29. Version ac07

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