Dornoch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dornoch clear sky chart from 2005-11-06 to 2024-04-03.

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% 12% 5% 8% 7% 3 5% 4 5% 6% 28%	78791
	Night	17% 13% 6% 10% 7% 3 4 4 4 6% 25%	81330
Transparency	Day	57% 6% 11% 16% 9% 1	78498
	Night	60% 6% 10% 14% 8% 1	81158
Seeing	Day	22% 13% 28% 22% 11% 4	14206
	Night	22% 11% 29% 27% 10% 1	23593

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	15% 22% 10% 18% 9% 3 4 3 2 4 10%	2221
	11th to 20th	Day	11% 21% 10% 18% 17% 5% 4 2 2 2 6%	2717
	21st to end	Day	17% 22% 11% 14% 8% 4 4 3 4 3 9%	3124
February	1st to 10th	Day	14% 20% 8% 17% 11% 4 4 4 3 4 11%	1710
	11th to 20th	Day	14% 15% 9% 16% 11% 4 4 4 5% 4 14%	1663
	21st to end	Day	15% 20% 8% 12% 9% 4 5% 4 5% 4 15%	1519
March	1st to 10th	Day	15% 13% 6% 11% 10% 3 4 3 4 5% 26%	2037
	11th to 20th	Day	14% 13% 7% 9% 7% 3 6% 4 4 6% 27%	2090
	21st to end	Day	19% 11% 5% 7% 6% 3 5% 5% 5% 5% 29%	2299
April	1st to 10th	Day	19% 15% 6% 7% 5% 3 4 5% 4 6% 25%	2096
	11th to 20th	Day	19% 12% 4 6% 3 2 4 4 5% 7% 34%	2296
	21st to end	Day	21% 11% 4 6% 4 3 4 4 4 7% 32%	2340
May	1st to 10th	Day	19% 9% 3 5% 5% 2 5% 5% 5% 7% 36%	2340
	11th to 20th	Day	17% 9% 3 5% 6% 3 4 4 5% 5% 39%	2396
	21st to end	Day	15% 6% 2 5% 5% 3 4 5% 6% 8% 42%	2725
June	1st to 10th	Day	16% 7% 3 6% 5% 3 4 5% 5% 8% 39%	2591
	11th to 20th	Day	13% 5% 2 6% 4 3 5% 5% 6% 9% 41%	2700
	21st to end	Day	18% 5% 2 5% 5% 3 4 5% 5% 8% 39%	2700
July	1st to 10th	Day	12% 4 3 5% 4 3 4 5% 6% 8% 46%	2700
	11th to 20th	Day	14% 6% 3 5% 6% 3 6% 6% 6% 9% 37%	2596
	21st to end	Day	13% 6% 3 5% 6% 3 5% 5% 7% 9% 39%	2547
August	1st to 10th	Day	12% 5% 2 6% 6% 4 6% 5% 7% 9% 38%	2327
	11th to 20th	Day	12% 6% 2 5% 8% 4 6% 5% 6% 8% 38%	2303
	21st to end	Day	14% 6% 3 5% 6% 3 5% 6% 6% 9% 37%	2543
September	1st to 10th	Day	15% 7% 4 6% 6% 3 4 5% 5% 7% 37%	2152
	11th to 20th	Day	14% 7% 2 6% 5% 2 5% 4 6% 7% 42%	1980
	21st to end	Day	19% 7% 3 6% 5% 4 5% 5% 4 9% 33%	1980
October	1st to 10th	Day	22% 10% 3 6% 5% 3 5% 4 4 6% 32%	1816
	11th to 20th	Day	27% 15% 4 7% 6% 2 5% 5% 4 5% 19%	1800
	21st to end	Day	29% 18% 4 7% 5% 3 4 4 4 4 17%	1936
November	1st to 10th	Day	17% 20% 4 7% 6% 3 5% 3 3 6% 25%	1628
	11th to 20th	Day	18% 18% 7% 10% 6% 3 5% 5% 5% 6% 17%	1520
	21st to end	Day	20% 24% 9% 8% 5% 3 4 5% 5% 4 13%	1520
December	1st to 10th	Day	15% 25% 13% 15% 7% 3 4 3 3 4 7%	1520
	11th to 20th	Day	20% 21% 8% 14% 8% 3 5% 3 4 4 10%	1906
	21st to end	Day	26% 22% 8% 13% 6% 3 3 3 3 4 8%	2453
January	1st to 10th	Night	15% 23% 11% 20% 9% 3 4 3 3 3 7%	4720
	11th to 20th	Night	15% 15% 10% 20% 13% 5% 5% 4 3 4 6%	4243
	21st to end	Night	17% 18% 12% 14% 8% 4 5% 4 4 3 10%	4532
February	1st to 10th	Night	13% 18% 8% 15% 12% 4 5% 5% 4 3 12%	2470
	11th to 20th	Night	13% 14% 9% 15% 10% 3 5% 4 4 5% 18%	2403
	21st to end	Night	16% 14% 7% 12% 8% 4 5% 4 4 6% 21%	1932
March	1st to 10th	Night	14% 12% 7% 12% 7% 4 5% 4 3 5% 28%	2129
	11th to 20th	Night	14% 14% 6% 9% 8% 3 4 4 4 5% 31%	2089
	21st to end	Night	17% 11% 5% 8% 5% 4 4 4 4 5% 32%	2299
April	1st to 10th	Night	20% 12% 6% 8% 5% 3 4 4 5% 6% 28%	1909
	11th to 20th	Night	19% 10% 3 5% 5% 2 4 3 4 7% 37%	1629
	21st to end	Night	18% 12% 4 7% 6% 3 5% 4 4 5% 32%	1620
May	1st to 10th	Night	17% 8% 4 6% 6% 3 3 5% 5% 8% 37%	1620
	11th to 20th	Night	16% 7% 2 6% 5% 3 5% 5% 4 7% 41%	1497
	21st to end	Night	11% 4 2 5% 4 2 5% 6% 6% 7% 47%	1550
June	1st to 10th	Night	15% 7% 3 6% 5% 2 4 5% 6% 8% 40%	1365
	11th to 20th	Night	13% 4 2 4 5% 3 5% 5% 7% 10% 41%	1260
	21st to end	Night	15% 5% 3 5% 5% 3 4 4 6% 7% 44%	1260
July	1st to 10th	Night	8% 4 2 3 3 3 4 4 5% 9% 55%	1260
	11th to 20th	Night	11% 5% 3 5% 4 3 5% 4 7% 9% 45%	1358
	21st to end	Night	11% 5% 2 5% 5% 3 4 5% 5% 8% 47%	1771
August	1st to 10th	Night	11% 5% 2 5% 5% 3 4 5% 4 7% 48%	1611
	11th to 20th	Night	11% 4 2 4 5% 3 4 5% 6% 9% 47%	1598
	21st to end	Night	13% 5% 3 6% 6% 4 4 5% 3 6% 44%	1793
September	1st to 10th	Night	12% 5% 2 5% 4 3 5% 4 6% 8% 45%	1806
	11th to 20th	Night	15% 5% 2 4 4 2 4 4 6% 8% 47%	1980
	21st to end	Night	17% 7% 3 6% 6% 3 4 4 5% 7% 37%	1980
October	1st to 10th	Night	21% 8% 3 6% 5% 3 4 4 5% 6% 35%	2143
	11th to 20th	Night	26% 12% 3 8% 5% 3 4 4 4 5% 25%	2160
	21st to end	Night	27% 14% 4 7% 7% 3 5% 4 4 6% 20%	2419
November	1st to 10th	Night	18% 17% 4 7% 6% 3 5% 5% 4 5% 26%	2448
	11th to 20th	Night	18% 17% 6% 9% 6% 3 5% 5% 5% 6% 19%	2660
	21st to end	Night	22% 18% 7% 9% 6% 3 4 4 4 6% 15%	2660
December	1st to 10th	Night	20% 24% 10% 12% 7% 4 4 3 3 4 9%	2660
	11th to 20th	Night	15% 22% 10% 14% 7% 3 4 4 4 5% 12%	3288
	21st to end	Night	24% 23% 9% 14% 7% 3 3 3 3 3 8%	5208

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	78% 7% 9% 6% 1	2222
	11th to 20th	Day	87% 4 4 3 2	2717
	21st to end	Day	80% 5% 8% 4 2	3124
February	1st to 10th	Day	79% 4 7% 8% 2	1710
	11th to 20th	Day	74% 4 8% 9% 5% 1	1672
	21st to end	Day	73% 4 8% 10% 4	1519
March	1st to 10th	Day	62% 5% 12% 13% 8% 1	2040
	11th to 20th	Day	59% 6% 10% 15% 9% 2	2090
	21st to end	Day	55% 6% 12% 14% 11% 2	2299
April	1st to 10th	Day	60% 5% 10% 16% 8%	2096
	11th to 20th	Day	50% 5% 10% 20% 14% 1	2296
	21st to end	Day	53% 6% 10% 17% 11% 2	2340
May	1st to 10th	Day	48% 6% 9% 22% 13% 1	2340
	11th to 20th	Day	47% 6% 10% 22% 14% 2	2400
	21st to end	Day	41% 6% 15% 21% 14% 3	2725
June	1st to 10th	Day	44% 6% 12% 22% 15% 1	2591
	11th to 20th	Day	38% 8% 12% 24% 17% 1	2700
	21st to end	Day	42% 7% 14% 23% 13% 1	2700
July	1st to 10th	Day	35% 7% 14% 23% 18% 3	2626
	11th to 20th	Day	41% 8% 14% 25% 11% 1	2515
	21st to end	Day	42% 7% 14% 23% 13% 2	2405
August	1st to 10th	Day	41% 8% 16% 23% 11% 2	2314
	11th to 20th	Day	42% 8% 15% 23% 11%	2303
	21st to end	Day	43% 8% 15% 22% 11% 1	2543
September	1st to 10th	Day	44% 8% 13% 22% 11% 2	2152
	11th to 20th	Day	40% 6% 16% 27% 11%	1980
	21st to end	Day	49% 7% 14% 23% 7% 1	1980
October	1st to 10th	Day	53% 6% 11% 17% 11% 1	1816
	11th to 20th	Day	64% 7% 11% 12% 5% 1	1800
	21st to end	Day	70% 5% 8% 11% 4	1936
November	1st to 10th	Day	62% 5% 12% 15% 6%	1628
	11th to 20th	Day	67% 7% 11% 9% 5% 1	1520
	21st to end	Day	73% 7% 10% 9% 1	1520
December	1st to 10th	Day	83% 6% 6% 5% 1	1520
	11th to 20th	Day	76% 8% 8% 7% 1	1906
	21st to end	Day	82% 6% 7% 4 1	2453
January	1st to 10th	Night	83% 6% 6% 4 1	4720
	11th to 20th	Night	84% 4 7% 3 2	4243
	21st to end	Night	79% 7% 7% 4 2	4532
February	1st to 10th	Night	76% 6% 8% 9% 1	2470
	11th to 20th	Night	69% 6% 10% 12% 4	2405
	21st to end	Night	64% 6% 11% 11% 7%	1932
March	1st to 10th	Night	59% 6% 10% 16% 9% 1	2139
	11th to 20th	Night	56% 6% 9% 16% 11% 2	2090
	21st to end	Night	54% 5% 9% 18% 12% 2	2299
April	1st to 10th	Night	58% 5% 9% 17% 11% 1	1909
	11th to 20th	Night	48% 5% 8% 20% 17% 1	1629
	21st to end	Night	54% 6% 8% 16% 14% 2	1620
May	1st to 10th	Night	46% 6% 8% 22% 15% 2	1620
	11th to 20th	Night	43% 6% 8% 24% 16% 3	1498
	21st to end	Night	33% 7% 15% 25% 16% 3	1551
June	1st to 10th	Night	41% 6% 12% 22% 17% 2	1365
	11th to 20th	Night	36% 8% 14% 25% 17% 1	1260
	21st to end	Night	39% 6% 13% 25% 16% 2	1260
July	1st to 10th	Night	27% 6% 13% 28% 23% 4	1225
	11th to 20th	Night	34% 7% 13% 30% 16% 1	1316
	21st to end	Night	35% 8% 15% 24% 16% 1	1672
August	1st to 10th	Night	34% 8% 15% 28% 14% 1	1600
	11th to 20th	Night	32% 9% 15% 28% 15% 1	1598
	21st to end	Night	41% 7% 12% 26% 12% 1	1793
September	1st to 10th	Night	36% 8% 14% 28% 12% 2	1806
	11th to 20th	Night	36% 6% 15% 29% 14%	1980
	21st to end	Night	46% 7% 14% 23% 9%	1980
October	1st to 10th	Night	50% 7% 10% 18% 13% 1	2143
	11th to 20th	Night	60% 5% 13% 16% 6%	2160
	21st to end	Night	66% 6% 10% 11% 6%	2419
November	1st to 10th	Night	59% 6% 12% 17% 6% 1	2448
	11th to 20th	Night	64% 7% 13% 10% 4 1	2660
	21st to end	Night	70% 8% 13% 8% 2	2660
December	1st to 10th	Night	80% 6% 8% 5% 1	2660
	11th to 20th	Night	74% 7% 12% 6% 1	3288
	21st to end	Night	83% 5% 7% 4	5208

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	23% 22% 34% 15% 5% 1	186
	11th to 20th	Day	24% 22% 34% 16% 4	270
	21st to end	Day	28% 16% 30% 23% 4	297
February	1st to 10th	Day	27% 29% 29% 11% 4	270
	11th to 20th	Day	25% 23% 38% 12% 1	270
	21st to end	Day	27% 31% 30% 11% 1	225
March	1st to 10th	Day	23% 19% 35% 16% 6%	410
	11th to 20th	Day	24% 16% 35% 18% 6% 1	460
	21st to end	Day	29% 15% 30% 19% 6% 1	506
April	1st to 10th	Day	24% 17% 33% 17% 7% 1	428
	11th to 20th	Day	29% 16% 25% 16% 8% 6%	412
	21st to end	Day	29% 12% 27% 23% 7% 2	420
May	1st to 10th	Day	26% 11% 25% 25% 9% 3	423
	11th to 20th	Day	21% 11% 29% 20% 16% 3	447
	21st to end	Day	20% 9% 24% 26% 16% 5%	485
June	1st to 10th	Day	17% 12% 27% 27% 14% 2	521
	11th to 20th	Day	16% 10% 32% 27% 13% 3	630
	21st to end	Day	19% 8% 34% 26% 11% 3	630
July	1st to 10th	Day	11% 7% 28% 29% 21% 4	621
	11th to 20th	Day	15% 8% 28% 28% 14% 7%	560
	21st to end	Day	12% 5% 28% 34% 15% 6%	488
August	1st to 10th	Day	13% 6% 24% 30% 16% 10%	446
	11th to 20th	Day	15% 4 20% 29% 22% 10%	439
	21st to end	Day	18% 6% 22% 28% 17% 9%	495
September	1st to 10th	Day	14% 11% 27% 24% 16% 9%	450
	11th to 20th	Day	12% 8% 23% 28% 20% 9%	450
	21st to end	Day	20% 11% 25% 24% 15% 5%	450
October	1st to 10th	Day	25% 12% 23% 23% 13% 5%	450
	11th to 20th	Day	29% 21% 27% 17% 4 1	450
	21st to end	Day	40% 14% 27% 15% 4	451
November	1st to 10th	Day	27% 23% 27% 15% 7%	248
	11th to 20th	Day	29% 21% 31% 16% 2 2	180
	21st to end	Day	29% 27% 31% 12% 1	180
December	1st to 10th	Day	29% 26% 29% 14% 2	180
	11th to 20th	Day	31% 24% 30% 11% 3 1	180
	21st to end	Day	38% 21% 29% 11% 2	198
January	1st to 10th	Night	23% 18% 32% 21% 5%	950
	11th to 20th	Night	30% 15% 29% 19% 6% 1	831
	21st to end	Night	20% 11% 34% 28% 6% 1	836
February	1st to 10th	Night	22% 18% 36% 21% 3	760
	11th to 20th	Night	21% 15% 35% 23% 5% 1	743
	21st to end	Night	22% 18% 37% 20% 3	628
March	1st to 10th	Night	19% 16% 37% 22% 6% 1	760
	11th to 20th	Night	20% 16% 36% 22% 5% 1	760
	21st to end	Night	22% 11% 30% 27% 8% 1	836
April	1st to 10th	Night	26% 13% 31% 25% 5%	729
	11th to 20th	Night	23% 12% 28% 24% 11% 1	565
	21st to end	Night	27% 9% 26% 27% 10%	540
May	1st to 10th	Night	20% 6% 28% 33% 12% 1	540
	11th to 20th	Night	19% 6% 26% 36% 11% 1	436
	21st to end	Night	14% 2 29% 39% 16%	389
June	1st to 10th	Night	17% 4 31% 36% 11% 1	360
	11th to 20th	Night	14% 6% 25% 41% 13%	360
	21st to end	Night	19% 4 23% 38% 16% 1	360
July	1st to 10th	Night	9% 4 16% 51% 19% 1	350
	11th to 20th	Night	13% 4 24% 37% 23% 1	391
	21st to end	Night	13% 3 19% 43% 21% 1	591
August	1st to 10th	Night	14% 2 17% 38% 27% 1	537
	11th to 20th	Night	13% 2 14% 38% 28% 4	534
	21st to end	Night	15% 3 23% 32% 24% 2	605
September	1st to 10th	Night	14% 6% 22% 34% 19% 5%	720
	11th to 20th	Night	16% 4 19% 38% 20% 4	720
	21st to end	Night	19% 8% 23% 31% 16% 4	720
October	1st to 10th	Night	23% 7% 27% 27% 14% 1	720
	11th to 20th	Night	32% 12% 25% 24% 7% 1	720
	21st to end	Night	33% 12% 30% 20% 4	792
November	1st to 10th	Night	29% 12% 30% 20% 7% 1	740
	11th to 20th	Night	26% 17% 31% 19% 6% 1	760
	21st to end	Night	29% 15% 32% 21% 3	760
December	1st to 10th	Night	31% 16% 31% 18% 3 1	760
	11th to 20th	Night	24% 19% 38% 15% 4 1	760
	21st to end	Night	33% 14% 33% 17% 3	1030

Page generated at 2024-03-31 06:08:54. Version ac07

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