Thurso
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Thurso clear sky chart from 2005-11-06 to 2024-11-04.

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% 10% 3 8% 5% 5% 4 4 5% 7% 32%	101562
	Night	18% 11% 4 8% 5% 4 4 3 5% 6% 32%	97444
Transparency	Day	49% 7% 12% 21% 9% 1	105032
	Night	51% 7% 12% 19% 9% 1	102063
Seeing	Day	22% 14% 30% 21% 10% 3	14486
	Night	22% 10% 29% 28% 10% 1	23513

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% 17% 6% 13% 7% 5% 4 3 4 4 20%	2517
	11th to 20th	Day	15% 13% 7% 14% 6% 5% 4 4 6% 5% 22%	2520
	21st to end	Day	14% 19% 7% 11% 6% 6% 6% 4 6% 5% 18%	2818
February	1st to 10th	Day	12% 16% 5% 12% 6% 5% 4 4 5% 5% 25%	1710
	11th to 20th	Day	13% 16% 5% 11% 6% 4 4 3 4 5% 28%	1689
	21st to end	Day	19% 13% 5% 9% 6% 5% 4 4 6% 4 25%	1570
March	1st to 10th	Day	21% 13% 4 9% 6% 5% 4 4 4 5% 26%	3116
	11th to 20th	Day	14% 15% 5% 10% 6% 5% 5% 4 5% 5% 27%	3432
	21st to end	Day	15% 8% 2 7% 6% 4 4 3 5% 6% 40%	4064
April	1st to 10th	Day	21% 12% 4 8% 4 4 4 2 4 5% 32%	2280
	11th to 20th	Day	22% 9% 2 7% 4 4 4 4 4 6% 35%	2254
	21st to end	Day	22% 10% 3 8% 5% 5% 4 4 4 5% 31%	2419
May	1st to 10th	Day	20% 8% 3 7% 4 5% 5% 4 6% 7% 30%	4426
	11th to 20th	Day	19% 8% 3 8% 5% 4 4 3 5% 8% 33%	4398
	21st to end	Day	16% 7% 3 7% 5% 4 4 4 6% 8% 36%	4837
June	1st to 10th	Day	21% 9% 3 7% 5% 4 5% 4 6% 6% 30%	2660
	11th to 20th	Day	14% 6% 2 6% 4 5% 5% 5% 6% 8% 37%	2660
	21st to end	Day	20% 7% 2 7% 4 5% 6% 5% 7% 7% 30%	2660
July	1st to 10th	Day	12% 7% 3 7% 6% 5% 5% 4 7% 9% 34%	4440
	11th to 20th	Day	14% 6% 2 7% 5% 5% 5% 4 7% 8% 38%	4440
	21st to end	Day	11% 6% 2 5% 4 4 5% 4 6% 8% 46%	4814
August	1st to 10th	Day	14% 6% 3 8% 5% 6% 5% 4 6% 8% 35%	4423
	11th to 20th	Day	15% 7% 3 6% 3 4 4 4 7% 9% 38%	3964
	21st to end	Day	15% 5% 2 6% 4 4 5% 4 6% 10% 39%	4180
September	1st to 10th	Day	14% 5% 2 6% 4 5% 4 3 5% 8% 42%	2280
	11th to 20th	Day	13% 5% 2 5% 4 4 4 3 5% 8% 48%	2259
	21st to end	Day	19% 5% 2 5% 5% 4 3 3 5% 7% 41%	2061
October	1st to 10th	Day	21% 8% 3 6% 5% 3 5% 3 5% 7% 35%	1900
	11th to 20th	Day	23% 10% 3 7% 5% 5% 5% 3 5% 6% 28%	1900
	21st to end	Day	25% 9% 3 8% 5% 4 4 3 5% 5% 28%	1906
November	1st to 10th	Day	17% 10% 3 6% 5% 5% 4 4 6% 8% 34%	1698
	11th to 20th	Day	20% 12% 4 8% 6% 5% 5% 4 3 6% 27%	1549
	21st to end	Day	22% 14% 4 9% 6% 5% 4 3 5% 6% 21%	1520
December	1st to 10th	Day	22% 18% 4 10% 6% 5% 5% 3 4 5% 18%	1520
	11th to 20th	Day	21% 15% 4 10% 5% 5% 4 3 4 5% 24%	1906
	21st to end	Day	27% 20% 5% 9% 4 3 2 3 3 4 19%	2772
January	1st to 10th	Night	18% 18% 6% 11% 5% 5% 4 3 4 5% 22%	4429
	11th to 20th	Night	13% 15% 5% 12% 7% 6% 5% 4 5% 5% 23%	4440
	21st to end	Night	16% 19% 7% 11% 5% 5% 4 3 4 4 21%	4820
February	1st to 10th	Night	14% 14% 5% 12% 7% 5% 5% 4 5% 5% 25%	2470
	11th to 20th	Night	13% 13% 5% 11% 7% 6% 4 3 4 6% 28%	2376
	21st to end	Night	15% 15% 4 9% 5% 4 5% 3 5% 6% 29%	1884
March	1st to 10th	Night	21% 12% 4 8% 5% 4 4 3 4 5% 30%	3724
	11th to 20th	Night	17% 17% 4 9% 5% 4 4 3 4 5% 27%	3525
	21st to end	Night	15% 9% 3 9% 5% 4 4 3 5% 5% 39%	3567
April	1st to 10th	Night	22% 10% 3 7% 5% 5% 4 3 4 6% 32%	1900
	11th to 20th	Night	20% 8% 3 7% 5% 4 3 4 5% 5% 35%	1875
	21st to end	Night	22% 8% 4 7% 4 3 4 3 5% 6% 34%	1776
May	1st to 10th	Night	20% 9% 3 9% 5% 5% 4 4 5% 6% 30%	2514
	11th to 20th	Night	21% 7% 3 7% 3 4 4 3 5% 6% 36%	2495
	21st to end	Night	16% 7% 2 7% 4 5% 5% 5% 5% 6% 37%	2738
June	1st to 10th	Night	17% 7% 3 6% 4 5% 5% 4 7% 9% 33%	1520
	11th to 20th	Night	14% 7% 3 6% 3 4 5% 4 5% 7% 42%	1520
	21st to end	Night	19% 7% 3 6% 5% 4 5% 4 6% 8% 34%	1520
July	1st to 10th	Night	13% 6% 3 8% 6% 5% 6% 4 6% 7% 35%	2520
	11th to 20th	Night	14% 7% 3 6% 4 4 4 4 7% 8% 41%	2520
	21st to end	Night	11% 6% 2 6% 5% 5% 5% 4 6% 7% 44%	2739
August	1st to 10th	Night	12% 8% 3 7% 4 5% 5% 4 7% 7% 38%	2506
	11th to 20th	Night	16% 6% 2 6% 4 4 4 4 6% 7% 42%	2830
	21st to end	Night	14% 5% 2 7% 5% 4 5% 4 6% 7% 41%	3476
September	1st to 10th	Night	11% 5% 2 6% 5% 4 4 4 5% 8% 45%	1900
	11th to 20th	Night	15% 5% 2 4 3 3 4 3 5% 7% 49%	1920
	21st to end	Night	17% 6% 2 6% 4 4 3 3 4 6% 45%	2118
October	1st to 10th	Night	19% 7% 3 7% 4 4 4 5% 5% 5% 38%	2280
	11th to 20th	Night	20% 8% 3 8% 4 5% 4 4 4 5% 33%	2280
	21st to end	Night	23% 10% 3 8% 5% 4 4 3 4 6% 30%	2690
November	1st to 10th	Night	19% 10% 3 7% 5% 4 4 3 6% 6% 33%	2453
	11th to 20th	Night	19% 11% 4 8% 5% 5% 4 3 5% 5% 30%	2627
	21st to end	Night	21% 14% 4 9% 6% 5% 4 3 5% 6% 24%	2660
December	1st to 10th	Night	22% 16% 5% 10% 6% 5% 5% 3 4 5% 19%	2660
	11th to 20th	Night	23% 15% 4 8% 5% 4 3 3 4 4 27%	3288
	21st to end	Night	30% 19% 4 9% 4 3 3 3 3 3 20%	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	66% 9% 8% 11% 5% 1	2518
	11th to 20th	Day	61% 7% 12% 13% 6% 1	2520
	21st to end	Day	66% 8% 10% 10% 5%	2818
February	1st to 10th	Day	61% 5% 9% 18% 5% 2	1710
	11th to 20th	Day	59% 6% 11% 15% 9% 1	1698
	21st to end	Day	59% 5% 10% 13% 10% 1	1570
March	1st to 10th	Day	60% 6% 8% 16% 9% 1	3119
	11th to 20th	Day	56% 8% 11% 14% 9% 1	3432
	21st to end	Day	44% 5% 8% 22% 18% 3	4064
April	1st to 10th	Day	55% 4 8% 18% 12% 3	2280
	11th to 20th	Day	51% 5% 7% 21% 15% 2	2254
	21st to end	Day	55% 6% 7% 14% 13% 4	2419
May	1st to 10th	Day	51% 8% 9% 21% 9% 2	4440
	11th to 20th	Day	47% 9% 14% 19% 9% 1	4402
	21st to end	Day	44% 8% 11% 21% 14% 1	4837
June	1st to 10th	Day	52% 7% 11% 18% 11% 1	2660
	11th to 20th	Day	42% 8% 13% 23% 12% 2	2660
	21st to end	Day	49% 9% 13% 18% 9% 1	2660
July	1st to 10th	Day	42% 8% 15% 24% 11%	4370
	11th to 20th	Day	40% 8% 15% 29% 8%	4365
	21st to end	Day	35% 8% 14% 33% 11%	4661
August	1st to 10th	Day	45% 8% 16% 22% 9%	4409
	11th to 20th	Day	40% 8% 17% 28% 7%	4003
	21st to end	Day	39% 8% 18% 23% 12% 1	4180
September	1st to 10th	Day	40% 7% 14% 28% 12%	2280
	11th to 20th	Day	34% 8% 13% 31% 13% 1	2259
	21st to end	Day	42% 7% 14% 27% 10%	2061
October	1st to 10th	Day	47% 6% 12% 27% 8%	3160
	11th to 20th	Day	47% 7% 14% 24% 7%	3140
	21st to end	Day	48% 5% 19% 21% 6%	3118
November	1st to 10th	Day	47% 7% 15% 23% 6% 1	1698
	11th to 20th	Day	58% 6% 12% 15% 9% 1	1549
	21st to end	Day	63% 7% 12% 12% 6% 1	1520
December	1st to 10th	Day	68% 6% 12% 10% 3	1520
	11th to 20th	Day	63% 6% 13% 14% 5%	1906
	21st to end	Day	71% 5% 6% 14% 4	2772
January	1st to 10th	Night	64% 7% 15% 10% 4	4429
	11th to 20th	Night	60% 8% 14% 12% 5%	4440
	21st to end	Night	66% 6% 11% 10% 6% 1	4820
February	1st to 10th	Night	60% 5% 11% 17% 6% 1	2470
	11th to 20th	Night	56% 6% 10% 20% 8%	2378
	21st to end	Night	55% 6% 10% 18% 11% 1	1884
March	1st to 10th	Night	56% 6% 9% 18% 9% 3	3734
	11th to 20th	Night	58% 6% 11% 15% 8% 2	3526
	21st to end	Night	45% 6% 8% 22% 16% 3	3567
April	1st to 10th	Night	53% 5% 9% 17% 14% 2	1900
	11th to 20th	Night	48% 6% 9% 21% 15% 1	1875
	21st to end	Night	50% 5% 9% 17% 15% 3	1776
May	1st to 10th	Night	52% 8% 10% 18% 9% 3	2520
	11th to 20th	Night	46% 9% 12% 19% 12% 2	2496
	21st to end	Night	44% 8% 11% 19% 17% 2	2739
June	1st to 10th	Night	45% 8% 13% 23% 10%	1520
	11th to 20th	Night	41% 7% 12% 23% 16% 2	1520
	21st to end	Night	45% 10% 12% 19% 14% 1	1520
July	1st to 10th	Night	44% 8% 15% 19% 12% 1	2480
	11th to 20th	Night	39% 7% 15% 31% 8%	2472
	21st to end	Night	36% 8% 16% 25% 14%	2651
August	1st to 10th	Night	42% 8% 16% 25% 8%	2496
	11th to 20th	Night	41% 6% 17% 29% 7%	2857
	21st to end	Night	39% 7% 16% 23% 12% 2	3476
September	1st to 10th	Night	37% 6% 12% 28% 14% 1	1900
	11th to 20th	Night	34% 7% 14% 34% 10% 1	1920
	21st to end	Night	41% 6% 12% 30% 11%	2118
October	1st to 10th	Night	41% 8% 14% 26% 11%	3800
	11th to 20th	Night	44% 8% 14% 25% 9%	3779
	21st to end	Night	46% 6% 18% 19% 10%	4428
November	1st to 10th	Night	50% 6% 14% 21% 8%	2453
	11th to 20th	Night	55% 6% 13% 16% 9% 1	2627
	21st to end	Night	60% 8% 12% 16% 5%	2660
December	1st to 10th	Night	67% 6% 10% 13% 4	2660
	11th to 20th	Night	61% 5% 9% 17% 7% 1	3288
	21st to end	Night	71% 4 8% 13% 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% 13% 31% 25% 3	180
	11th to 20th	Day	23% 19% 37% 17% 4 1	180
	21st to end	Day	21% 16% 35% 23% 5%	213
February	1st to 10th	Day	26% 26% 34% 12% 2	270
	11th to 20th	Day	25% 25% 36% 13% 1	296
	21st to end	Day	29% 17% 33% 19% 2	382
March	1st to 10th	Day	25% 16% 32% 20% 6%	460
	11th to 20th	Day	24% 19% 35% 18% 4 1	460
	21st to end	Day	28% 18% 30% 14% 8% 2	506
April	1st to 10th	Day	27% 20% 32% 14% 7% 1	460
	11th to 20th	Day	30% 20% 21% 18% 9% 2	452
	21st to end	Day	29% 17% 32% 14% 6% 2	460
May	1st to 10th	Day	23% 13% 35% 20% 6% 3	463
	11th to 20th	Day	18% 16% 32% 21% 10% 2	487
	21st to end	Day	19% 15% 33% 22% 9% 2	529
June	1st to 10th	Day	24% 12% 28% 26% 9% 1	490
	11th to 20th	Day	15% 14% 31% 24% 14% 2	490
	21st to end	Day	22% 12% 28% 23% 12% 2	490
July	1st to 10th	Day	13% 10% 28% 30% 15% 4	485
	11th to 20th	Day	12% 10% 33% 25% 17% 3	484
	21st to end	Day	14% 7% 29% 32% 16% 4	532
August	1st to 10th	Day	14% 7% 26% 34% 15% 3	486
	11th to 20th	Day	14% 7% 21% 32% 18% 8%	479
	21st to end	Day	13% 10% 27% 27% 14% 8%	539
September	1st to 10th	Day	16% 9% 29% 21% 17% 8%	490
	11th to 20th	Day	12% 10% 21% 20% 22% 15%	490
	21st to end	Day	20% 12% 26% 22% 15% 6%	490
October	1st to 10th	Day	24% 14% 22% 22% 13% 3	490
	11th to 20th	Day	26% 19% 28% 17% 9% 1	490
	21st to end	Day	29% 15% 31% 20% 5%	442
November	1st to 10th	Day	26% 15% 27% 23% 8% 1	374
	11th to 20th	Day	27% 20% 34% 13% 4 1	209
	21st to end	Day	27% 20% 32% 16% 5% 1	180
December	1st to 10th	Day	31% 12% 31% 22% 4	180
	11th to 20th	Day	26% 18% 41% 13% 2 1	180
	21st to end	Day	34% 16% 36% 11% 3 1	198
January	1st to 10th	Night	28% 12% 35% 21% 5%	760
	11th to 20th	Night	28% 13% 30% 23% 6% 1	760
	21st to end	Night	19% 10% 35% 28% 6% 1	836
February	1st to 10th	Night	19% 12% 39% 25% 4	760
	11th to 20th	Night	21% 14% 38% 23% 4 1	743
	21st to end	Night	25% 13% 30% 29% 3	628
March	1st to 10th	Night	24% 13% 32% 26% 5%	760
	11th to 20th	Night	25% 13% 33% 23% 5%	760
	21st to end	Night	22% 12% 33% 24% 8%	836
April	1st to 10th	Night	26% 13% 29% 27% 5%	760
	11th to 20th	Night	23% 14% 32% 23% 7% 1	751
	21st to end	Night	26% 11% 31% 24% 7% 1	636
May	1st to 10th	Night	23% 10% 28% 27% 9% 2	380
	11th to 20th	Night	23% 9% 26% 32% 9% 1	374
	21st to end	Night	15% 7% 36% 28% 13%	411
June	1st to 10th	Night	16% 6% 27% 40% 11%	380
	11th to 20th	Night	16% 5% 27% 37% 14% 1	380
	21st to end	Night	18% 6% 26% 34% 14% 2	380
July	1st to 10th	Night	9% 4 28% 41% 18%	370
	11th to 20th	Night	13% 5% 18% 44% 20% 1	368
	21st to end	Night	11% 4 22% 43% 18% 2	416
August	1st to 10th	Night	12% 3 17% 46% 20% 1	378
	11th to 20th	Night	13% 3 19% 35% 27% 3	583
	21st to end	Night	13% 6% 23% 36% 20% 2	836
September	1st to 10th	Night	14% 6% 26% 35% 19% 1	760
	11th to 20th	Night	16% 6% 19% 30% 25% 3	760
	21st to end	Night	19% 8% 24% 29% 19% 2	760
October	1st to 10th	Night	21% 8% 26% 29% 15% 1	760
	11th to 20th	Night	25% 9% 28% 29% 9% 1	760
	21st to end	Night	26% 11% 30% 27% 5%	836
November	1st to 10th	Night	25% 11% 26% 28% 9% 1	755
	11th to 20th	Night	25% 14% 31% 19% 10% 1	760
	21st to end	Night	27% 15% 29% 24% 6%	760
December	1st to 10th	Night	29% 13% 32% 22% 4	760
	11th to 20th	Night	28% 14% 30% 22% 5% 1	760
	21st to end	Night	35% 12% 30% 19% 3	836

Page generated at 2024-11-01 22:47:38. Version ac07

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