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 2025-02-25.

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	16% 10% 3 8% 5% 4 4 4 5% 7% 34%	108804
	Night	16% 10% 4 8% 5% 4 4 4 5% 6% 33%	109847
Transparency	Day	50% 3 12% 23% 11% 1	112394
	Night	51% 3 12% 22% 12% 1	114420
Seeing	Day	24% 14% 31% 19% 9% 3	14736
	Night	23% 13% 29% 24% 10% 1	24142

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	13% 13% 4 9% 4 4 4 4 6% 7% 32%	3597
	11th to 20th	Day	11% 19% 7% 14% 7% 6% 5% 3 4 4 21%	3570
	21st to end	Day	15% 17% 7% 15% 6% 5% 4 3 4 4 21%	4466
February	1st to 10th	Day	15% 14% 5% 12% 7% 6% 4 4 6% 5% 24%	1800
	11th to 20th	Day	13% 16% 5% 12% 7% 5% 4 3 4 4 27%	1753
	21st to end	Day	19% 14% 5% 9% 5% 6% 4 4 4 5% 24%	1545
March	1st to 10th	Day	22% 12% 3 7% 5% 4 4 2 5% 6% 30%	3303
	11th to 20th	Day	11% 17% 4 10% 5% 5% 4 3 5% 6% 32%	3480
	21st to end	Day	15% 8% 2 6% 4 3 3 3 5% 5% 45%	3900
April	1st to 10th	Day	20% 13% 3 6% 5% 4 3 3 4 6% 32%	2280
	11th to 20th	Day	23% 8% 2 5% 4 4 4 2 4 6% 38%	2254
	21st to end	Day	22% 10% 3 8% 5% 4 4 3 4 5% 33%	2441
May	1st to 10th	Day	20% 8% 3 7% 5% 4 4 4 5% 7% 34%	4317
	11th to 20th	Day	16% 9% 3 8% 5% 5% 4 4 6% 8% 32%	4398
	21st to end	Day	13% 5% 2 6% 4 4 5% 4 6% 8% 43%	4837
June	1st to 10th	Day	18% 7% 2 7% 5% 5% 5% 4 7% 7% 32%	2660
	11th to 20th	Day	13% 6% 2 6% 5% 5% 5% 4 7% 9% 38%	2660
	21st to end	Day	17% 7% 3 6% 5% 4 5% 4 6% 8% 36%	2660
July	1st to 10th	Day	11% 5% 2 6% 5% 5% 5% 4 7% 9% 39%	4440
	11th to 20th	Day	12% 5% 2 4 4 4 5% 5% 7% 9% 44%	4440
	21st to end	Day	7% 5% 2 6% 5% 5% 6% 5% 8% 9% 42%	4790
August	1st to 10th	Day	16% 7% 3 7% 4 4 5% 4 6% 8% 37%	4104
	11th to 20th	Day	15% 7% 3 6% 5% 4 5% 4 6% 8% 37%	4044
	21st to end	Day	12% 5% 2 7% 4 4 5% 5% 7% 9% 40%	4226
September	1st to 10th	Day	13% 5% 2 6% 5% 5% 4 4 6% 7% 43%	2280
	11th to 20th	Day	10% 5% 2 5% 4 4 3 4 6% 7% 49%	2280
	21st to end	Day	16% 6% 2 7% 4 4 4 3 5% 7% 40%	1985
October	1st to 10th	Day	18% 8% 3 7% 5% 4 5% 4 4 7% 34%	1900
	11th to 20th	Day	22% 8% 3 8% 4 5% 4 3 6% 7% 31%	1900
	21st to end	Day	25% 11% 3 8% 5% 4 5% 3 5% 6% 27%	2047
November	1st to 10th	Day	15% 9% 3 7% 6% 5% 5% 3 6% 7% 34%	1701
	11th to 20th	Day	16% 12% 3 9% 6% 4 4 4 6% 6% 31%	1600
	21st to end	Day	21% 14% 4 9% 6% 4 4 3 6% 5% 25%	1600
December	1st to 10th	Day	19% 18% 4 11% 5% 6% 4 4 4 6% 20%	2600
	11th to 20th	Day	17% 18% 6% 10% 4 4 4 2 3 4 26%	2986
	21st to end	Day	25% 14% 4 9% 4 4 4 3 3 5% 25%	3960
January	1st to 10th	Night	15% 14% 6% 11% 6% 5% 5% 3 4 6% 25%	6349
	11th to 20th	Night	12% 14% 7% 14% 8% 6% 5% 4 5% 5% 18%	6297
	21st to end	Night	15% 15% 7% 12% 5% 4 4 3 4 5% 23%	6490
February	1st to 10th	Night	14% 14% 5% 11% 7% 5% 4 4 5% 6% 26%	2600
	11th to 20th	Night	14% 14% 5% 9% 6% 5% 5% 4 5% 5% 28%	2533
	21st to end	Night	16% 12% 3 10% 5% 4 4 4 6% 6% 30%	2003
March	1st to 10th	Night	19% 11% 3 8% 6% 5% 4 3 5% 6% 31%	3532
	11th to 20th	Night	16% 14% 4 9% 6% 4 4 3 5% 6% 29%	3479
	21st to end	Night	16% 8% 3 6% 4 4 3 3 5% 6% 42%	3732
April	1st to 10th	Night	19% 10% 3 7% 4 4 3 3 5% 5% 35%	1900
	11th to 20th	Night	19% 8% 3 7% 4 4 4 4 4 5% 37%	1875
	21st to end	Night	19% 8% 3 8% 3 4 5% 4 6% 7% 34%	1755
May	1st to 10th	Night	21% 8% 3 7% 4 4 4 4 4 6% 35%	2624
	11th to 20th	Night	17% 8% 3 6% 4 4 4 4 6% 7% 36%	2495
	21st to end	Night	11% 6% 2 6% 4 5% 4 4 5% 7% 46%	2738
June	1st to 10th	Night	15% 6% 2 6% 5% 4 5% 4 5% 9% 38%	1520
	11th to 20th	Night	11% 6% 3 5% 6% 4 4 4 6% 7% 44%	1520
	21st to end	Night	15% 6% 2 6% 5% 4 4 4 6% 7% 41%	1520
July	1st to 10th	Night	9% 5% 2 6% 6% 6% 5% 5% 6% 8% 43%	2520
	11th to 20th	Night	12% 5% 2 5% 4 3 4 4 5% 8% 48%	2520
	21st to end	Night	10% 4 2 5% 3 4 4 4 6% 9% 49%	2760
August	1st to 10th	Night	11% 5% 2 6% 4 4 4 4 5% 8% 47%	2825
	11th to 20th	Night	14% 6% 2 5% 3 4 4 3 5% 8% 46%	2785
	21st to end	Night	9% 4 2 5% 4 4 5% 4 7% 9% 47%	3398
September	1st to 10th	Night	11% 7% 2 6% 4 5% 4 3 6% 8% 46%	1900
	11th to 20th	Night	12% 4 1 4 4 4 4 3 5% 7% 53%	1900
	21st to end	Night	18% 5% 2 7% 3 4 5% 3 5% 6% 42%	2189
October	1st to 10th	Night	17% 6% 3 7% 4 5% 5% 4 5% 6% 39%	2280
	11th to 20th	Night	21% 8% 3 8% 6% 5% 4 3 4 6% 33%	2280
	21st to end	Night	23% 10% 3 7% 5% 4 4 4 5% 6% 29%	2551
November	1st to 10th	Night	19% 8% 3 5% 5% 4 4 3 5% 7% 38%	2593
	11th to 20th	Night	17% 10% 3 7% 5% 5% 4 3 6% 7% 32%	2800
	21st to end	Night	21% 12% 3 7% 5% 5% 5% 5% 5% 7% 27%	2800
December	1st to 10th	Night	19% 15% 4 8% 5% 5% 5% 5% 7% 7% 20%	4580
	11th to 20th	Night	19% 15% 5% 10% 5% 4 4 3 4 6% 25%	5208
	21st to end	Night	27% 16% 3 10% 4 4 4 3 4 4 21%	6996

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	52% 2 12% 22% 10% 1	3598
	11th to 20th	Day	68% 2 10% 12% 7%	3600
	21st to end	Day	68% 2 8% 11% 9% 1	4466
February	1st to 10th	Day	62% 3 9% 19% 6% 1	1800
	11th to 20th	Day	61% 2 7% 17% 11% 1	1762
	21st to end	Day	64% 2 8% 15% 10% 1	1545
March	1st to 10th	Day	57% 2 11% 18% 11% 1	3306
	11th to 20th	Day	55% 1 13% 16% 12% 2	3480
	21st to end	Day	42% 2 7% 28% 17% 3	3900
April	1st to 10th	Day	55% 2 7% 21% 12% 3	2280
	11th to 20th	Day	49% 2 8% 23% 17% 1	2254
	21st to end	Day	56% 2 7% 19% 14% 3	2441
May	1st to 10th	Day	52% 2 8% 24% 13% 2	4330
	11th to 20th	Day	51% 2 13% 23% 10% 1	4402
	21st to end	Day	41% 2 13% 26% 16% 3	4837
June	1st to 10th	Day	50% 4 11% 20% 14% 1	2660
	11th to 20th	Day	42% 3 12% 26% 15% 2	2660
	21st to end	Day	46% 3 13% 23% 13% 1	2660
July	1st to 10th	Day	39% 5% 14% 28% 14% 1	4370
	11th to 20th	Day	35% 4 15% 36% 10%	4365
	21st to end	Day	37% 6% 14% 31% 12%	4637
August	1st to 10th	Day	45% 4 15% 24% 12% 1	4091
	11th to 20th	Day	43% 4 15% 29% 9%	4083
	21st to end	Day	38% 4 13% 33% 10% 1	4226
September	1st to 10th	Day	39% 4 13% 30% 13% 1	2280
	11th to 20th	Day	34% 3 13% 34% 16% 1	2280
	21st to end	Day	44% 4 13% 29% 10%	1985
October	1st to 10th	Day	42% 4 12% 31% 11% 1	3160
	11th to 20th	Day	44% 4 15% 25% 11% 1	3140
	21st to end	Day	52% 4 13% 22% 8%	3349
November	1st to 10th	Day	49% 3 14% 23% 10% 1	1701
	11th to 20th	Day	54% 3 12% 18% 12% 1	1600
	21st to end	Day	62% 4 12% 15% 8%	1600
December	1st to 10th	Day	66% 3 16% 11% 4	2600
	11th to 20th	Day	64% 3 9% 15% 8%	2986
	21st to end	Day	64% 3 8% 16% 9%	3960
January	1st to 10th	Night	63% 1 11% 16% 9%	6349
	11th to 20th	Night	68% 3 11% 12% 5% 1	6342
	21st to end	Night	63% 2 10% 11% 12% 1	6490
February	1st to 10th	Night	60% 3 10% 20% 7% 1	2600
	11th to 20th	Night	58% 3 8% 21% 10% 1	2535
	21st to end	Night	54% 2 11% 22% 10% 1	2003
March	1st to 10th	Night	56% 2 7% 24% 11% 1	3542
	11th to 20th	Night	58% 1 12% 19% 10% 1	3480
	21st to end	Night	44% 1 6% 24% 21% 2	3732
April	1st to 10th	Night	52% 3 7% 22% 14% 2	1900
	11th to 20th	Night	49% 3 9% 21% 17% 1	1875
	21st to end	Night	49% 4 10% 18% 16% 3	1755
May	1st to 10th	Night	52% 2 9% 20% 15% 2	2630
	11th to 20th	Night	47% 2 13% 27% 10% 2	2496
	21st to end	Night	40% 1 13% 23% 21% 2	2739
June	1st to 10th	Night	44% 3 11% 25% 15% 2	1520
	11th to 20th	Night	39% 3 12% 24% 20% 3	1520
	21st to end	Night	42% 3 14% 25% 14% 2	1520
July	1st to 10th	Night	38% 5% 13% 25% 18% 2	2480
	11th to 20th	Night	35% 4 13% 34% 14%	2472
	21st to end	Night	32% 5% 17% 33% 12% 1	2672
August	1st to 10th	Night	37% 3 13% 30% 15% 1	2814
	11th to 20th	Night	37% 4 18% 28% 12% 1	2812
	21st to end	Night	32% 5% 13% 37% 12% 1	3398
September	1st to 10th	Night	37% 3 15% 29% 15% 1	1900
	11th to 20th	Night	32% 3 14% 34% 17% 1	1900
	21st to end	Night	44% 3 11% 29% 13% 1	2189
October	1st to 10th	Night	37% 3 10% 30% 20%	3800
	11th to 20th	Night	44% 3 13% 30% 9%	3779
	21st to end	Night	47% 4 13% 26% 9%	4199
November	1st to 10th	Night	47% 3 12% 25% 11% 1	2593
	11th to 20th	Night	52% 3 12% 21% 11% 2	2800
	21st to end	Night	57% 4 15% 18% 6%	2800
December	1st to 10th	Night	61% 4 14% 17% 4	4580
	11th to 20th	Night	62% 4 12% 14% 8% 1	5208
	21st to end	Night	68% 2 9% 12% 9%	6996

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% 22% 35% 13% 4 1	200
	11th to 20th	Day	33% 18% 29% 16% 5% 1	200
	21st to end	Day	30% 23% 31% 12% 4 1	330
February	1st to 10th	Day	33% 23% 31% 10% 3	300
	11th to 20th	Day	32% 26% 33% 8% 1	300
	21st to end	Day	37% 19% 35% 9% 2	333
March	1st to 10th	Day	27% 19% 33% 15% 5%	460
	11th to 20th	Day	30% 19% 32% 15% 3	460
	21st to end	Day	35% 17% 30% 12% 6% 1	506
April	1st to 10th	Day	33% 17% 33% 10% 6%	460
	11th to 20th	Day	36% 17% 23% 14% 7% 3	452
	21st to end	Day	31% 19% 31% 12% 4 2	460
May	1st to 10th	Day	26% 14% 30% 19% 6% 5%	463
	11th to 20th	Day	21% 13% 34% 22% 8% 3	487
	21st to end	Day	18% 14% 36% 18% 12% 3	529
June	1st to 10th	Day	22% 12% 34% 22% 7% 2	490
	11th to 20th	Day	15% 14% 32% 23% 12% 3	490
	21st to end	Day	24% 13% 29% 22% 10% 2	490
July	1st to 10th	Day	13% 9% 31% 31% 14% 4	485
	11th to 20th	Day	16% 9% 30% 26% 15% 5%	484
	21st to end	Day	12% 8% 36% 27% 13% 4	532
August	1st to 10th	Day	14% 7% 30% 28% 14% 7%	486
	11th to 20th	Day	14% 6% 29% 27% 17% 6%	479
	21st to end	Day	16% 9% 30% 26% 12% 7%	539
September	1st to 10th	Day	14% 10% 32% 24% 11% 8%	490
	11th to 20th	Day	12% 6% 28% 23% 18% 12%	490
	21st to end	Day	19% 13% 26% 25% 11% 5%	490
October	1st to 10th	Day	26% 15% 24% 18% 12% 5%	490
	11th to 20th	Day	27% 16% 33% 15% 7% 2	490
	21st to end	Day	31% 16% 29% 20% 4	516
November	1st to 10th	Day	30% 16% 26% 17% 10% 1	335
	11th to 20th	Day	31% 19% 33% 13% 4 1	200
	21st to end	Day	32% 21% 31% 13% 4 1	200
December	1st to 10th	Day	34% 13% 34% 17% 4	200
	11th to 20th	Day	37% 22% 29% 10% 3 1	200
	21st to end	Day	37% 17% 31% 10% 3 1	220
January	1st to 10th	Night	29% 19% 31% 17% 4 1	800
	11th to 20th	Night	29% 18% 28% 20% 5%	800
	21st to end	Night	22% 16% 34% 22% 4 1	880
February	1st to 10th	Night	25% 21% 33% 20% 2	800
	11th to 20th	Night	25% 22% 33% 17% 4	783
	21st to end	Night	26% 19% 34% 18% 3	647
March	1st to 10th	Night	24% 16% 36% 20% 3	760
	11th to 20th	Night	28% 17% 31% 20% 4 1	760
	21st to end	Night	23% 17% 30% 22% 7% 1	836
April	1st to 10th	Night	26% 17% 31% 23% 4	760
	11th to 20th	Night	26% 19% 27% 20% 8% 1	751
	21st to end	Night	24% 13% 30% 23% 9% 1	615
May	1st to 10th	Night	24% 10% 27% 26% 12% 2	451
	11th to 20th	Night	18% 8% 33% 31% 10%	374
	21st to end	Night	12% 8% 33% 32% 14% 1	411
June	1st to 10th	Night	16% 8% 33% 31% 12% 1	380
	11th to 20th	Night	14% 9% 31% 31% 14% 1	380
	21st to end	Night	17% 7% 26% 34% 14% 1	380
July	1st to 10th	Night	7% 5% 28% 44% 15% 1	370
	11th to 20th	Night	11% 2 30% 36% 20% 1	368
	21st to end	Night	11% 2 30% 40% 16% 1	425
August	1st to 10th	Night	11% 3 25% 33% 25% 3	567
	11th to 20th	Night	11% 5% 21% 38% 23% 2	564
	21st to end	Night	12% 5% 28% 34% 20% 2	784
September	1st to 10th	Night	14% 6% 28% 32% 17% 3	760
	11th to 20th	Night	13% 5% 23% 26% 28% 5%	760
	21st to end	Night	20% 8% 22% 28% 19% 3	760
October	1st to 10th	Night	21% 11% 26% 24% 16% 2	760
	11th to 20th	Night	26% 12% 30% 23% 9%	760
	21st to end	Night	29% 14% 29% 22% 5%	836
November	1st to 10th	Night	26% 13% 25% 26% 10% 1	780
	11th to 20th	Night	25% 17% 31% 19% 7% 1	800
	21st to end	Night	30% 16% 28% 21% 6%	800
December	1st to 10th	Night	31% 18% 29% 19% 4	800
	11th to 20th	Night	28% 18% 34% 17% 3	800
	21st to end	Night	36% 14% 31% 16% 3	880

Page generated at 2025-02-22 06:51:33. Version ac07

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