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 2024-11-04.

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	16% 12% 4 9% 5% 4 4 3 5% 6% 30%	101624
	Night	16% 14% 5% 10% 5% 4 4 3 4 5% 28%	97411
Transparency	Day	54% 6% 11% 18% 10% 1	105184
	Night	56% 6% 11% 16% 9% 1	101940
Seeing	Day	22% 13% 28% 22% 11% 4	15100
	Night	22% 11% 29% 27% 10% 1	24250

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% 23% 10% 20% 8% 5% 3 2 2 4 10%	2221
	11th to 20th	Day	10% 22% 10% 21% 15% 6% 3 2 2 2 6%	2717
	21st to end	Day	17% 23% 10% 16% 6% 6% 4 3 4 3 9%	3124
February	1st to 10th	Day	13% 22% 7% 19% 9% 6% 3 3 3 4 11%	1710
	11th to 20th	Day	14% 16% 8% 18% 9% 5% 4 3 5% 4 14%	1663
	21st to end	Day	14% 22% 7% 13% 8% 5% 5% 4 4 4 15%	1519
March	1st to 10th	Day	18% 15% 6% 10% 6% 4 3 3 3 5% 26%	3360
	11th to 20th	Day	12% 17% 9% 12% 6% 4 4 3 4 5% 24%	3480
	21st to end	Day	16% 14% 6% 9% 5% 4 5% 4 5% 6% 27%	3815
April	1st to 10th	Day	19% 17% 5% 8% 4 4 4 4 4 6% 26%	2190
	11th to 20th	Day	20% 13% 3 7% 2 4 4 3 5% 6% 34%	2426
	21st to end	Day	21% 11% 4 7% 4 3 3 3 5% 6% 33%	2470
May	1st to 10th	Day	20% 9% 3 6% 3 4 4 4 5% 7% 36%	4108
	11th to 20th	Day	17% 9% 2 7% 5% 4 4 4 6% 8% 35%	4260
	21st to end	Day	17% 6% 1 5% 3 4 4 3 5% 7% 45%	4837
June	1st to 10th	Day	16% 8% 2 7% 4 4 4 4 5% 7% 37%	2735
	11th to 20th	Day	13% 5% 2 6% 4 4 5% 4 6% 9% 41%	2850
	21st to end	Day	19% 6% 2 6% 5% 4 5% 4 5% 8% 37%	2850
July	1st to 10th	Day	16% 6% 2 6% 5% 6% 5% 4 7% 8% 36%	4760
	11th to 20th	Day	14% 5% 2 5% 5% 4 5% 4 6% 8% 42%	4558
	21st to end	Day	12% 6% 2 6% 5% 4 4 4 6% 8% 44%	4466
August	1st to 10th	Day	14% 6% 2 7% 5% 5% 5% 4 7% 8% 36%	4104
	11th to 20th	Day	15% 6% 2 7% 5% 5% 5% 3 7% 8% 35%	4044
	21st to end	Day	11% 5% 2 6% 5% 5% 4 5% 6% 9% 43%	4473
September	1st to 10th	Day	15% 7% 3 7% 5% 4 4 4 5% 7% 38%	2271
	11th to 20th	Day	13% 7% 2 6% 4 4 5% 3 5% 7% 44%	2090
	21st to end	Day	19% 8% 3 8% 4 4 6% 4 4 8% 33%	2090
October	1st to 10th	Day	21% 10% 3 6% 4 4 4 3 5% 6% 33%	1916
	11th to 20th	Day	25% 15% 3 8% 5% 4 5% 4 4 6% 21%	1900
	21st to end	Day	28% 18% 4 8% 4 4 4 3 4 5% 18%	2043
November	1st to 10th	Day	17% 20% 4 8% 6% 4 4 2 4 6% 25%	1655
	11th to 20th	Day	17% 20% 5% 11% 6% 4 5% 4 5% 6% 17%	1520
	21st to end	Day	20% 26% 8% 8% 5% 4 3 4 5% 4 13%	1520
December	1st to 10th	Day	15% 29% 10% 16% 6% 4 4 2 4 4 7%	1520
	11th to 20th	Day	20% 22% 8% 15% 7% 4 4 3 4 4 10%	1906
	21st to end	Day	26% 24% 8% 15% 4 4 3 2 3 4 8%	2453
January	1st to 10th	Night	15% 24% 10% 22% 7% 4 3 2 3 3 6%	4720
	11th to 20th	Night	14% 17% 9% 23% 10% 7% 5% 3 3 4 6%	4243
	21st to end	Night	17% 19% 11% 16% 7% 6% 4 3 3 3 10%	4532
February	1st to 10th	Night	13% 20% 7% 16% 11% 6% 4 4 4 3 12%	2470
	11th to 20th	Night	13% 16% 9% 17% 8% 4 4 3 4 5% 18%	2403
	21st to end	Night	16% 16% 6% 13% 7% 5% 4 3 4 6% 21%	1932
March	1st to 10th	Night	13% 15% 5% 9% 4 4 4 3 4 6% 31%	3479
	11th to 20th	Night	11% 17% 7% 9% 5% 4 4 3 4 5% 31%	3479
	21st to end	Night	15% 10% 6% 12% 5% 5% 4 4 4 5% 30%	3817
April	1st to 10th	Night	20% 14% 5% 8% 5% 3 3 3 5% 6% 28%	1990
	11th to 20th	Night	19% 11% 3 6% 5% 4 3 3 4 6% 36%	1720
	21st to end	Night	19% 12% 4 8% 5% 4 5% 3 4 5% 31%	1710
May	1st to 10th	Night	15% 8% 3 7% 4 4 3 4 5% 8% 40%	2833
	11th to 20th	Night	17% 7% 2 6% 5% 4 4 3 5% 7% 41%	2633
	21st to end	Night	12% 6% 2 5% 4 3 4 3 5% 7% 48%	2738
June	1st to 10th	Night	15% 8% 3 6% 5% 4 3 4 6% 7% 39%	1440
	11th to 20th	Night	12% 5% 2 5% 5% 4 5% 4 8% 9% 40%	1330
	21st to end	Night	15% 6% 3 5% 4 3 4 3 6% 7% 43%	1330
July	1st to 10th	Night	10% 6% 3 6% 4 4 4 3 5% 8% 48%	2210
	11th to 20th	Night	16% 5% 2 4 3 3 3 3 5% 7% 50%	2402
	21st to end	Night	9% 7% 2 5% 5% 4 4 4 6% 7% 48%	3087
August	1st to 10th	Night	14% 6% 3 7% 4 4 4 3 4 6% 45%	2825
	11th to 20th	Night	18% 6% 3 6% 4 3 4 4 5% 8% 40%	2785
	21st to end	Night	15% 5% 2 6% 4 4 3 4 4 6% 47%	3149
September	1st to 10th	Night	12% 6% 2 6% 4 4 4 3 6% 8% 46%	1907
	11th to 20th	Night	14% 5% 2 4 3 3 4 3 5% 7% 49%	2090
	21st to end	Night	17% 7% 3 7% 5% 4 4 4 6% 7% 37%	2090
October	1st to 10th	Night	20% 8% 3 7% 4 4 5% 3 5% 5% 36%	2263
	11th to 20th	Night	24% 13% 3 8% 4 5% 4 3 4 5% 26%	2280
	21st to end	Night	26% 15% 4 7% 6% 4 4 3 5% 6% 21%	2554
November	1st to 10th	Night	18% 18% 3 8% 5% 4 5% 3 4 5% 26%	2494
	11th to 20th	Night	18% 19% 5% 10% 6% 5% 4 4 5% 6% 19%	2660
	21st to end	Night	21% 20% 6% 10% 5% 4 4 3 4 6% 15%	2660
December	1st to 10th	Night	19% 27% 8% 12% 6% 5% 4 3 4 3 9%	2660
	11th to 20th	Night	15% 24% 9% 15% 6% 4 4 4 4 4 12%	3288
	21st to end	Night	24% 24% 8% 16% 5% 4 3 2 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	61% 5% 12% 13% 8% 1	3363
	11th to 20th	Day	62% 5% 11% 15% 5% 1	3480
	21st to end	Day	55% 7% 13% 15% 8% 1	3815
April	1st to 10th	Day	60% 5% 10% 16% 8%	2190
	11th to 20th	Day	51% 5% 9% 20% 14% 1	2426
	21st to end	Day	53% 6% 10% 17% 12% 2	2470
May	1st to 10th	Day	45% 8% 13% 20% 14% 1	4120
	11th to 20th	Day	46% 9% 14% 22% 9% 1	4264
	21st to end	Day	38% 6% 12% 20% 18% 6%	4837
June	1st to 10th	Day	45% 7% 12% 22% 14% 1	2735
	11th to 20th	Day	38% 8% 12% 24% 17% 1	2850
	21st to end	Day	43% 7% 14% 23% 13% 1	2850
July	1st to 10th	Day	45% 7% 13% 19% 15% 2	4686
	11th to 20th	Day	38% 6% 12% 31% 12% 1	4477
	21st to end	Day	38% 6% 11% 24% 18% 2	4324
August	1st to 10th	Day	44% 7% 13% 21% 14% 1	4091
	11th to 20th	Day	46% 8% 14% 23% 10%	4083
	21st to end	Day	37% 7% 14% 30% 11% 1	4473
September	1st to 10th	Day	44% 8% 13% 22% 11% 2	2271
	11th to 20th	Day	39% 6% 15% 27% 13%	2090
	21st to end	Day	48% 7% 13% 23% 8% 1	2090
October	1st to 10th	Day	48% 6% 11% 22% 12% 1	3176
	11th to 20th	Day	52% 7% 12% 19% 10%	3140
	21st to end	Day	62% 4 12% 17% 4	3345
November	1st to 10th	Day	61% 5% 12% 15% 6%	1655
	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	53% 6% 14% 18% 8%	3489
	11th to 20th	Night	53% 7% 13% 16% 9% 1	3480
	21st to end	Night	52% 8% 10% 19% 10% 1	3817
April	1st to 10th	Night	57% 5% 9% 17% 11% 1	1990
	11th to 20th	Night	50% 5% 8% 20% 16% 1	1720
	21st to end	Night	54% 6% 8% 15% 15% 2	1710
May	1st to 10th	Night	42% 7% 11% 20% 16% 4	2840
	11th to 20th	Night	42% 8% 13% 22% 13% 2	2634
	21st to end	Night	34% 7% 12% 24% 20% 3	2739
June	1st to 10th	Night	43% 6% 12% 21% 17% 2	1440
	11th to 20th	Night	36% 8% 13% 25% 17% 1	1330
	21st to end	Night	39% 6% 13% 25% 15% 2	1330
July	1st to 10th	Night	35% 5% 14% 23% 18% 5%	2175
	11th to 20th	Night	34% 5% 11% 34% 15% 1	2360
	21st to end	Night	35% 7% 14% 26% 16% 1	2988
August	1st to 10th	Night	39% 6% 11% 27% 16% 1	2814
	11th to 20th	Night	43% 7% 15% 23% 12% 1	2812
	21st to end	Night	38% 6% 11% 31% 13% 1	3149
September	1st to 10th	Night	36% 8% 13% 29% 13% 2	1907
	11th to 20th	Night	35% 5% 14% 29% 17% 1	2090
	21st to end	Night	46% 7% 13% 23% 10%	2090
October	1st to 10th	Night	41% 7% 9% 25% 17% 1	3783
	11th to 20th	Night	52% 4 13% 18% 13%	3779
	21st to end	Night	54% 7% 15% 19% 5%	4202
November	1st to 10th	Night	59% 6% 12% 17% 6% 1	2494
	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% 31% 19% 6% 1	506
April	1st to 10th	Day	24% 18% 33% 17% 7% 1	460
	11th to 20th	Day	31% 17% 25% 15% 8% 5%	452
	21st to end	Day	29% 12% 27% 23% 7% 2	460
May	1st to 10th	Day	25% 11% 25% 26% 10% 3	463
	11th to 20th	Day	21% 11% 28% 22% 15% 3	487
	21st to end	Day	20% 9% 25% 26% 16% 4	529
June	1st to 10th	Day	18% 12% 28% 27% 14% 2	565
	11th to 20th	Day	15% 10% 33% 27% 12% 3	680
	21st to end	Day	20% 9% 34% 25% 11% 2	680
July	1st to 10th	Day	12% 8% 28% 29% 20% 3	671
	11th to 20th	Day	15% 9% 29% 28% 13% 7%	606
	21st to end	Day	13% 5% 28% 32% 17% 5%	532
August	1st to 10th	Day	13% 6% 26% 29% 16% 9%	486
	11th to 20th	Day	15% 5% 20% 28% 21% 10%	479
	21st to end	Day	17% 6% 23% 29% 17% 8%	539
September	1st to 10th	Day	16% 11% 26% 24% 15% 8%	490
	11th to 20th	Day	11% 8% 22% 27% 21% 12%	490
	21st to end	Day	20% 11% 26% 24% 15% 5%	490
October	1st to 10th	Day	25% 12% 24% 23% 12% 4	490
	11th to 20th	Day	28% 20% 29% 16% 5% 1	490
	21st to end	Day	40% 13% 28% 15% 4	492
November	1st to 10th	Day	28% 23% 28% 15% 7%	257
	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	27% 12% 31% 25% 5%	760
	11th to 20th	Night	24% 12% 28% 24% 10% 1	596
	21st to end	Night	27% 9% 26% 27% 10%	570
May	1st to 10th	Night	20% 6% 28% 34% 12% 1	570
	11th to 20th	Night	19% 6% 25% 37% 11% 1	460
	21st to end	Night	14% 3 28% 40% 15%	411
June	1st to 10th	Night	18% 6% 30% 35% 11% 1	380
	11th to 20th	Night	14% 6% 26% 41% 12%	380
	21st to end	Night	19% 4 23% 38% 15% 1	380
July	1st to 10th	Night	9% 4 17% 50% 18% 1	370
	11th to 20th	Night	13% 4 24% 37% 22% 1	414
	21st to end	Night	13% 3 19% 44% 22% 1	624
August	1st to 10th	Night	14% 2 17% 38% 27% 1	567
	11th to 20th	Night	15% 2 14% 37% 28% 4	564
	21st to end	Night	16% 3 22% 32% 24% 2	639
September	1st to 10th	Night	15% 6% 23% 34% 19% 4	760
	11th to 20th	Night	15% 4 18% 38% 21% 4	760
	21st to end	Night	19% 7% 23% 31% 16% 4	760
October	1st to 10th	Night	23% 7% 28% 28% 13% 1	760
	11th to 20th	Night	31% 11% 25% 24% 7% 1	760
	21st to end	Night	33% 12% 30% 20% 4	836
November	1st to 10th	Night	29% 12% 30% 20% 7% 1	755
	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 2024-11-01 22:47:46. Version ac07

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