Taigh nan Reul
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Taigh nan Reul clear sky chart from 2005-11-06 to 2025-12-03.

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	16% 11% 4 8% 5% 4 4 3 5% 6% 32%	127714
	Night	16% 13% 5% 10% 5% 4 4 3 5% 6% 29%	122949
Transparency	Day	51% 6% 12% 20% 10% 1	131283
	Night	55% 6% 11% 18% 10% 1	127456
Seeing	Day	23% 15% 31% 20% 9% 3	16327
	Night	23% 13% 28% 25% 9% 1	25271

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% 17% 9% 10% 4 5% 5% 3 4 5% 26%	3226
	11th to 20th	Day	10% 20% 9% 19% 10% 6% 5% 3 4 3 11%	3780
	21st to end	Day	12% 19% 8% 15% 7% 6% 5% 3 5% 4 16%	4466
February	1st to 10th	Day	12% 19% 7% 16% 9% 5% 4 2 3 3 19%	1800
	11th to 20th	Day	13% 16% 6% 13% 6% 5% 4 3 4 5% 24%	1753
	21st to end	Day	17% 18% 6% 10% 6% 5% 5% 3 4 4 21%	1515
March	1st to 10th	Day	19% 14% 5% 10% 5% 4 4 3 3 5% 29%	4925
	11th to 20th	Day	11% 14% 5% 10% 6% 6% 5% 4 5% 7% 26%	4980
	21st to end	Day	18% 14% 6% 9% 4 4 3 3 4 5% 33%	5465
April	1st to 10th	Day	20% 14% 4 8% 5% 4 3 3 4 6% 30%	2363
	11th to 20th	Day	21% 12% 3 6% 4 4 4 3 4 4 36%	2494
	21st to end	Day	22% 11% 3 7% 3 3 4 3 5% 5% 34%	2600
May	1st to 10th	Day	18% 9% 3 6% 4 5% 5% 4 5% 7% 34%	5952
	11th to 20th	Day	14% 10% 3 7% 4 4 4 3 5% 7% 40%	6318
	21st to end	Day	21% 9% 3 6% 4 4 4 3 5% 6% 35%	6949
June	1st to 10th	Day	18% 7% 2 7% 5% 5% 4 4 5% 6% 37%	2816
	11th to 20th	Day	13% 6% 2 6% 5% 4 5% 4 6% 8% 39%	3000
	21st to end	Day	17% 8% 3 6% 4 4 4 4 6% 7% 36%	3000
July	1st to 10th	Day	14% 6% 3 6% 5% 4 5% 4 6% 9% 38%	6819
	11th to 20th	Day	12% 6% 2 5% 4 4 4 4 6% 6% 47%	6508
	21st to end	Day	8% 5% 2 6% 4 4 4 4 5% 9% 49%	6616
August	1st to 10th	Day	12% 7% 3 7% 4 5% 5% 4 6% 8% 38%	4234
	11th to 20th	Day	15% 6% 2 7% 4 4 5% 4 8% 9% 36%	4174
	21st to end	Day	9% 4 2 6% 5% 5% 5% 4 7% 9% 45%	4547
September	1st to 10th	Day	14% 5% 3 6% 5% 5% 4 4 6% 7% 41%	2400
	11th to 20th	Day	14% 6% 2 5% 4 4 4 3 6% 7% 45%	2277
	21st to end	Day	18% 8% 3 7% 5% 4 5% 3 5% 6% 35%	2164
October	1st to 10th	Day	20% 7% 3 7% 5% 4 4 4 4 7% 35%	2000
	11th to 20th	Day	25% 10% 3 9% 5% 4 4 3 6% 7% 24%	2000
	21st to end	Day	29% 12% 4 9% 4 4 4 3 5% 4 22%	2197
November	1st to 10th	Day	19% 16% 4 7% 5% 4 4 3 5% 7% 26%	1699
	11th to 20th	Day	17% 16% 5% 10% 5% 5% 6% 3 6% 5% 22%	1680
	21st to end	Day	20% 22% 3 11% 5% 5% 5% 4 4 5% 15%	1680
December	1st to 10th	Day	16% 25% 8% 10% 4 4 5% 3 5% 5% 14%	2616
	11th to 20th	Day	18% 23% 9% 14% 5% 3 2 2 3 4 17%	2986
	21st to end	Day	24% 19% 5% 13% 5% 4 3 2 3 4 17%	3715
January	1st to 10th	Night	13% 20% 8% 13% 6% 5% 4 4 4 5% 18%	6701
	11th to 20th	Night	11% 17% 7% 19% 8% 6% 6% 3 4 5% 13%	6087
	21st to end	Night	12% 20% 8% 13% 7% 6% 5% 3 4 5% 18%	6490
February	1st to 10th	Night	12% 19% 7% 12% 8% 4 5% 3 5% 6% 19%	2600
	11th to 20th	Night	12% 17% 6% 12% 7% 5% 5% 4 5% 5% 23%	2533
	21st to end	Night	16% 16% 5% 10% 7% 5% 4 4 4 5% 23%	2111
March	1st to 10th	Night	16% 14% 4 9% 5% 4 4 3 5% 6% 30%	4913
	11th to 20th	Night	10% 14% 6% 10% 6% 6% 5% 4 5% 6% 28%	4979
	21st to end	Night	21% 12% 5% 7% 4 4 4 3 5% 5% 31%	5467
April	1st to 10th	Night	21% 12% 3 8% 5% 4 4 3 4 5% 30%	2036
	11th to 20th	Night	18% 11% 3 8% 3 4 3 3 6% 5% 35%	1872
	21st to end	Night	18% 10% 4 8% 5% 4 4 4 5% 6% 31%	1800
May	1st to 10th	Night	17% 8% 2 7% 5% 5% 4 4 6% 7% 35%	3989
	11th to 20th	Night	13% 7% 2 6% 5% 4 4 4 5% 8% 42%	3575
	21st to end	Night	18% 8% 3 6% 4 5% 4 3 5% 7% 37%	3926
June	1st to 10th	Night	15% 7% 3 7% 5% 4 4 4 6% 8% 35%	1579
	11th to 20th	Night	12% 5% 2 6% 4 4 4 4 5% 10% 43%	1400
	21st to end	Night	16% 7% 3 7% 4 4 4 4 6% 7% 40%	1400
July	1st to 10th	Night	13% 8% 3 7% 4 4 5% 4 6% 8% 40%	3160
	11th to 20th	Night	14% 5% 2 6% 4 3 3 4 4 7% 48%	3454
	21st to end	Night	10% 6% 2 5% 4 4 4 3 5% 8% 50%	4234
August	1st to 10th	Night	10% 6% 2 6% 4 4 5% 4 6% 8% 45%	2915
	11th to 20th	Night	16% 7% 3 6% 4 3 4 3 5% 6% 44%	2875
	21st to end	Night	14% 5% 2 5% 3 3 3 4 5% 7% 48%	3317
September	1st to 10th	Night	10% 6% 3 6% 4 4 4 4 6% 7% 46%	2000
	11th to 20th	Night	12% 5% 2 6% 4 3 3 4 5% 7% 49%	2120
	21st to end	Night	19% 6% 2 7% 5% 4 3 3 5% 6% 39%	2235
October	1st to 10th	Night	18% 8% 3 6% 5% 5% 4 3 6% 6% 37%	2400
	11th to 20th	Night	24% 11% 4 8% 5% 4 4 3 5% 6% 26%	2400
	21st to end	Night	26% 11% 5% 9% 5% 4 4 3 4 5% 24%	2640
November	1st to 10th	Night	20% 14% 3 7% 5% 4 4 3 4 6% 29%	2818
	11th to 20th	Night	17% 17% 5% 8% 5% 5% 5% 3 5% 6% 23%	2940
	21st to end	Night	23% 20% 5% 10% 6% 4 4 3 5% 6% 15%	2940
December	1st to 10th	Night	18% 26% 7% 11% 5% 4 4 3 5% 5% 13%	4609
	11th to 20th	Night	16% 22% 8% 18% 6% 5% 4 3 4 4 11%	5208
	21st to end	Night	23% 21% 6% 14% 5% 4 3 3 3 4 14%	7226

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	59% 6% 9% 17% 9%	3227
	11th to 20th	Day	76% 6% 6% 7% 5%	3812
	21st to end	Day	71% 6% 8% 9% 7%	4466
February	1st to 10th	Day	72% 4 6% 13% 4 1	1800
	11th to 20th	Day	64% 4 10% 13% 8% 1	1762
	21st to end	Day	67% 4 8% 14% 6%	1515
March	1st to 10th	Day	58% 5% 12% 10% 14% 1	4928
	11th to 20th	Day	57% 5% 14% 16% 7% 1	4980
	21st to end	Day	54% 4 9% 19% 12% 1	5465
April	1st to 10th	Day	56% 4 10% 18% 10% 1	2363
	11th to 20th	Day	52% 4 8% 23% 13%	2494
	21st to end	Day	52% 5% 9% 18% 13% 3	2600
May	1st to 10th	Day	48% 5% 12% 20% 10% 5%	5961
	11th to 20th	Day	43% 6% 12% 20% 18% 1	6322
	21st to end	Day	49% 5% 11% 19% 13% 3	6949
June	1st to 10th	Day	46% 7% 10% 24% 13%	2816
	11th to 20th	Day	40% 8% 12% 24% 16% 1	3000
	21st to end	Day	45% 8% 14% 21% 11% 1	3000
July	1st to 10th	Day	40% 7% 16% 27% 10% 1	6746
	11th to 20th	Day	35% 6% 13% 32% 14%	6429
	21st to end	Day	31% 6% 14% 34% 15%	6427
August	1st to 10th	Day	42% 7% 15% 25% 10% 1	4221
	11th to 20th	Day	41% 8% 17% 26% 8%	4213
	21st to end	Day	34% 7% 15% 35% 10% 1	4547
September	1st to 10th	Day	42% 6% 14% 27% 10% 1	2400
	11th to 20th	Day	38% 6% 14% 30% 12% 1	2277
	21st to end	Day	50% 7% 11% 24% 9%	2164
October	1st to 10th	Day	44% 6% 13% 26% 10% 1	3260
	11th to 20th	Day	51% 6% 13% 23% 7%	3240
	21st to end	Day	58% 6% 13% 17% 6%	3523
November	1st to 10th	Day	58% 6% 14% 17% 5%	1699
	11th to 20th	Day	63% 7% 13% 12% 5% 1	1680
	21st to end	Day	71% 6% 9% 10% 3	1680
December	1st to 10th	Day	71% 6% 12% 8% 3	2616
	11th to 20th	Day	73% 4 6% 12% 4	2986
	21st to end	Day	73% 3 6% 11% 6%	3715
January	1st to 10th	Night	69% 5% 6% 13% 6%	6701
	11th to 20th	Night	72% 7% 7% 8% 5% 1	6130
	21st to end	Night	68% 5% 9% 10% 8% 1	6490
February	1st to 10th	Night	66% 5% 10% 14% 4 1	2600
	11th to 20th	Night	62% 5% 9% 16% 7%	2535
	21st to end	Night	63% 5% 10% 16% 6%	2111
March	1st to 10th	Night	55% 4 12% 13% 12% 4	4923
	11th to 20th	Night	54% 6% 16% 16% 7% 1	4980
	21st to end	Night	55% 5% 7% 19% 14% 2	5467
April	1st to 10th	Night	57% 4 9% 19% 10% 2	2036
	11th to 20th	Night	49% 5% 8% 21% 15% 2	1872
	21st to end	Night	53% 6% 8% 15% 16% 1	1800
May	1st to 10th	Night	47% 6% 11% 20% 12% 5%	3996
	11th to 20th	Night	39% 7% 11% 23% 19% 2	3576
	21st to end	Night	45% 6% 11% 23% 14% 1	3927
June	1st to 10th	Night	45% 7% 9% 22% 15% 2	1579
	11th to 20th	Night	37% 5% 12% 25% 19% 1	1400
	21st to end	Night	43% 7% 14% 24% 12% 1	1400
July	1st to 10th	Night	41% 6% 13% 25% 13% 2	3125
	11th to 20th	Night	36% 5% 12% 33% 14%	3410
	21st to end	Night	33% 5% 8% 36% 17% 1	4108
August	1st to 10th	Night	37% 5% 16% 26% 15% 1	2904
	11th to 20th	Night	40% 6% 17% 24% 12% 1	2902
	21st to end	Night	34% 6% 13% 35% 12% 1	3317
September	1st to 10th	Night	35% 8% 17% 26% 14% 1	2000
	11th to 20th	Night	34% 7% 13% 32% 13%	2120
	21st to end	Night	45% 6% 12% 26% 11%	2235
October	1st to 10th	Night	37% 7% 11% 28% 17%	3920
	11th to 20th	Night	50% 6% 14% 22% 8%	3899
	21st to end	Night	54% 6% 16% 18% 7%	4252
November	1st to 10th	Night	56% 5% 12% 19% 7%	2818
	11th to 20th	Night	62% 6% 11% 14% 6% 1	2940
	21st to end	Night	70% 6% 11% 10% 3	2940
December	1st to 10th	Night	73% 6% 11% 7% 2	4609
	11th to 20th	Night	75% 6% 8% 8% 3	5208
	21st to end	Night	76% 5% 6% 9% 5%	7226

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	17% 28% 37% 14% 5%	200
	11th to 20th	Day	24% 24% 33% 13% 5%	247
	21st to end	Day	27% 18% 35% 17% 3	330
February	1st to 10th	Day	32% 26% 31% 6% 3	300
	11th to 20th	Day	26% 26% 39% 8% 1	300
	21st to end	Day	40% 23% 32% 5%	249
March	1st to 10th	Day	27% 22% 33% 15% 3	493
	11th to 20th	Day	24% 21% 35% 16% 4	500
	21st to end	Day	34% 16% 30% 15% 5% 1	550
April	1st to 10th	Day	28% 21% 30% 15% 6%	500
	11th to 20th	Day	36% 17% 22% 15% 8% 2	492
	21st to end	Day	32% 15% 33% 13% 5% 2	500
May	1st to 10th	Day	25% 12% 33% 20% 7% 2	503
	11th to 20th	Day	19% 15% 32% 21% 11% 2	527
	21st to end	Day	20% 15% 31% 21% 11% 2	573
June	1st to 10th	Day	20% 16% 30% 27% 6% 1	546
	11th to 20th	Day	17% 13% 33% 25% 10% 2	730
	21st to end	Day	22% 11% 35% 22% 9% 2	730
July	1st to 10th	Day	13% 9% 34% 27% 15% 2	721
	11th to 20th	Day	16% 11% 27% 30% 12% 5%	590
	21st to end	Day	13% 9% 33% 28% 11% 6%	576
August	1st to 10th	Day	14% 8% 26% 31% 14% 7%	526
	11th to 20th	Day	15% 6% 26% 29% 14% 9%	519
	21st to end	Day	14% 10% 31% 24% 15% 6%	583
September	1st to 10th	Day	16% 11% 27% 24% 14% 8%	530
	11th to 20th	Day	12% 8% 25% 24% 21% 11%	530
	21st to end	Day	20% 13% 25% 25% 14% 3	530
October	1st to 10th	Day	24% 16% 26% 18% 12% 4	530
	11th to 20th	Day	27% 21% 32% 15% 5% 1	530
	21st to end	Day	34% 20% 29% 14% 3	580
November	1st to 10th	Day	33% 19% 31% 14% 3	248
	11th to 20th	Day	27% 23% 36% 10% 3	220
	21st to end	Day	30% 23% 36% 10%	220
December	1st to 10th	Day	29% 23% 31% 14% 3	204
	11th to 20th	Day	34% 28% 25% 11% 2 1	200
	21st to end	Day	36% 23% 29% 9% 3	220
January	1st to 10th	Night	29% 19% 31% 16% 4 1	958
	11th to 20th	Night	30% 16% 32% 17% 4 1	800
	21st to end	Night	22% 12% 35% 23% 7% 1	880
February	1st to 10th	Night	23% 22% 32% 20% 3	800
	11th to 20th	Night	22% 19% 33% 21% 5%	783
	21st to end	Night	25% 21% 30% 21% 4	660
March	1st to 10th	Night	23% 19% 33% 22% 3	800
	11th to 20th	Night	21% 17% 35% 21% 4 1	800
	21st to end	Night	22% 16% 30% 24% 8%	880
April	1st to 10th	Night	29% 14% 30% 23% 4	800
	11th to 20th	Night	26% 13% 28% 23% 9% 1	688
	21st to end	Night	25% 11% 29% 25% 9%	600
May	1st to 10th	Night	22% 6% 26% 33% 11% 1	575
	11th to 20th	Night	19% 8% 30% 31% 11%	394
	21st to end	Night	15% 5% 30% 36% 14%	433
June	1st to 10th	Night	16% 8% 33% 33% 10% 1	400
	11th to 20th	Night	14% 9% 27% 39% 12%	400
	21st to end	Night	18% 7% 25% 36% 14%	400
July	1st to 10th	Night	11% 6% 20% 45% 18% 1	390
	11th to 20th	Night	13% 5% 26% 35% 20% 1	388
	21st to end	Night	11% 5% 25% 37% 22% 1	567
August	1st to 10th	Night	13% 4 19% 37% 25% 3	597
	11th to 20th	Night	13% 5% 18% 38% 23% 3	594
	21st to end	Night	16% 7% 26% 29% 21% 2	715
September	1st to 10th	Night	13% 7% 28% 29% 19% 4	800
	11th to 20th	Night	14% 7% 21% 32% 22% 4	800
	21st to end	Night	20% 9% 20% 31% 18% 2	800
October	1st to 10th	Night	21% 12% 28% 26% 13% 1	800
	11th to 20th	Night	29% 15% 25% 22% 8% 1	800
	21st to end	Night	31% 17% 29% 20% 3	880
November	1st to 10th	Night	30% 14% 28% 21% 7% 1	820
	11th to 20th	Night	27% 21% 30% 17% 5%	840
	21st to end	Night	36% 15% 31% 16% 3	840
December	1st to 10th	Night	34% 22% 27% 13% 4 1	809
	11th to 20th	Night	28% 21% 33% 14% 4 1	800
	21st to end	Night	35% 15% 30% 18% 2	980

Page generated at 2025-11-30 01:00:55. Version ac07

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