Bootland Farm
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bootland Farm clear sky chart from 2005-11-06 to 2026-10-29.

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% 5% 5% 4 5% 7% 33%	150262
	Night	16% 11% 4 9% 5% 5% 4 4 5% 6% 31%	141775
Transparency	Day	50% 6% 12% 21% 10% 1	153755
	Night	52% 6% 12% 19% 10% 1	146371
Seeing	Day	22% 17% 31% 19% 8% 3	16946
	Night	21% 14% 30% 25% 9% 1	26004

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% 15% 5% 13% 8% 7% 5% 3 5% 5% 20%	4661
	11th to 20th	Day	11% 19% 6% 15% 8% 5% 4 3 5% 5% 18%	4650
	21st to end	Day	9% 16% 7% 16% 9% 8% 5% 3 4 4 20%	5462
February	1st to 10th	Day	13% 14% 5% 13% 7% 5% 5% 4 5% 4 24%	1890
	11th to 20th	Day	11% 15% 7% 10% 7% 5% 4 4 5% 6% 27%	1843
	21st to end	Day	19% 12% 4 10% 6% 6% 5% 4 5% 4 24%	1700
March	1st to 10th	Day	18% 14% 6% 11% 6% 4 4 2 4 5% 26%	4668
	11th to 20th	Day	12% 12% 4 10% 6% 5% 5% 4 5% 6% 29%	5090
	21st to end	Day	16% 12% 3 8% 5% 4 3 3 4 5% 37%	5820
April	1st to 10th	Day	21% 13% 3 7% 4 4 4 2 5% 5% 31%	2520
	11th to 20th	Day	22% 11% 3 6% 4 4 4 3 4 3 36%	2494
	21st to end	Day	21% 10% 3 8% 4 4 4 3 4 5% 33%	2677
May	1st to 10th	Day	21% 9% 3 8% 5% 4 5% 4 5% 7% 29%	8237
	11th to 20th	Day	16% 8% 3 7% 5% 5% 5% 4 5% 7% 34%	8221
	21st to end	Day	20% 8% 2 6% 4 4 4 3 5% 6% 37%	9060
June	1st to 10th	Day	20% 9% 3 7% 5% 5% 5% 3 5% 6% 32%	2940
	11th to 20th	Day	15% 5% 2 7% 5% 5% 5% 4 6% 7% 39%	2940
	21st to end	Day	17% 7% 2 6% 4 5% 5% 4 7% 8% 33%	2940
July	1st to 10th	Day	13% 5% 2 6% 5% 5% 5% 4 6% 9% 38%	8280
	11th to 20th	Day	10% 4 2 6% 4 4 5% 4 6% 8% 48%	8280
	21st to end	Day	13% 4 2 6% 4 4 5% 4 6% 10% 42%	8993
August	1st to 10th	Day	17% 7% 3 8% 5% 5% 5% 4 6% 6% 36%	6277
	11th to 20th	Day	15% 6% 2 6% 5% 4 4 4 6% 8% 40%	5951
	21st to end	Day	13% 5% 2 7% 4 5% 5% 5% 7% 10% 37%	6085
September	1st to 10th	Day	14% 6% 2 6% 5% 5% 5% 3 5% 8% 42%	2520
	11th to 20th	Day	12% 5% 2 6% 4 5% 5% 3 5% 7% 47%	2520
	21st to end	Day	17% 6% 2 6% 4 4 4 3 6% 7% 41%	2226
October	1st to 10th	Day	19% 8% 3 7% 4 5% 4 4 5% 6% 36%	2100
	11th to 20th	Day	21% 9% 3 7% 5% 5% 5% 3 5% 7% 30%	2100
	21st to end	Day	24% 11% 3 7% 4 4 4 3 5% 6% 28%	2148
November	1st to 10th	Day	15% 11% 4 7% 5% 4 5% 4 5% 6% 35%	1815
	11th to 20th	Day	17% 12% 5% 9% 5% 5% 5% 4 5% 6% 27%	1680
	21st to end	Day	21% 15% 4 10% 6% 6% 4 3 4 5% 21%	1680
December	1st to 10th	Day	21% 20% 6% 12% 6% 5% 5% 3 4 5% 13%	2680
	11th to 20th	Day	16% 17% 5% 12% 7% 5% 4 3 4 3 25%	3066
	21st to end	Day	22% 16% 6% 14% 5% 5% 4 2 3 4 19%	4048
January	1st to 10th	Night	12% 18% 8% 14% 6% 5% 5% 3 4 5% 19%	8234
	11th to 20th	Night	12% 16% 6% 16% 8% 6% 5% 3 4 5% 19%	8235
	21st to end	Night	10% 16% 6% 11% 8% 7% 6% 4 4 5% 22%	8717
February	1st to 10th	Night	11% 15% 6% 12% 7% 6% 5% 4 5% 6% 24%	2730
	11th to 20th	Night	12% 14% 5% 12% 7% 5% 4 3 4 6% 28%	2663
	21st to end	Night	15% 12% 5% 10% 6% 5% 5% 4 6% 5% 27%	2105
March	1st to 10th	Night	21% 14% 4 10% 5% 4 4 2 3 3 29%	5376
	11th to 20th	Night	12% 12% 4 9% 5% 6% 5% 5% 7% 8% 29%	5089
	21st to end	Night	17% 11% 4 10% 5% 4 4 3 5% 6% 32%	5340
April	1st to 10th	Night	21% 11% 3 8% 5% 4 4 3 4 5% 32%	2100
	11th to 20th	Night	20% 10% 3 8% 4 4 4 3 4 5% 36%	2075
	21st to end	Night	21% 10% 3 8% 4 4 4 3 4 6% 34%	1960
May	1st to 10th	Night	21% 9% 3 8% 5% 5% 5% 4 6% 6% 28%	4660
	11th to 20th	Night	15% 7% 3 7% 4 5% 4 3 6% 7% 39%	4639
	21st to end	Night	20% 7% 2 7% 4 4 4 4 6% 7% 35%	5114
June	1st to 10th	Night	15% 6% 3 7% 6% 5% 5% 5% 6% 8% 35%	1680
	11th to 20th	Night	13% 7% 3 7% 4 3 3 4 5% 7% 45%	1680
	21st to end	Night	16% 6% 2 6% 6% 4 4 5% 7% 7% 37%	1680
July	1st to 10th	Night	12% 6% 2 7% 5% 5% 5% 4 6% 9% 39%	4680
	11th to 20th	Night	12% 4 2 5% 4 3 4 4 5% 8% 48%	4680
	21st to end	Night	12% 5% 2 7% 5% 5% 5% 4 6% 7% 43%	5084
August	1st to 10th	Night	14% 5% 2 7% 5% 4 5% 4 7% 9% 38%	3869
	11th to 20th	Night	13% 6% 2 7% 4 4 4 4 5% 7% 43%	4095
	21st to end	Night	12% 5% 3 7% 5% 4 5% 4 6% 8% 42%	4994
September	1st to 10th	Night	11% 5% 2 7% 4 4 4 3 5% 6% 46%	2100
	11th to 20th	Night	13% 4 2 4 4 4 4 3 5% 7% 51%	2100
	21st to end	Night	16% 6% 2 7% 4 4 4 3 5% 5% 44%	2391
October	1st to 10th	Night	17% 7% 3 7% 4 4 4 4 4 6% 41%	2520
	11th to 20th	Night	20% 10% 3 7% 4 5% 5% 4 5% 5% 32%	2520
	21st to end	Night	21% 10% 3 7% 4 4 5% 3 5% 7% 30%	2868
November	1st to 10th	Night	18% 11% 3 8% 5% 4 4 3 5% 5% 33%	2699
	11th to 20th	Night	18% 12% 4 8% 6% 4 5% 4 5% 6% 29%	2940
	21st to end	Night	20% 14% 5% 11% 6% 4 4 3 5% 5% 22%	2940
December	1st to 10th	Night	19% 17% 5% 13% 6% 5% 5% 4 5% 5% 15%	4720
	11th to 20th	Night	21% 15% 4 11% 6% 5% 4 3 4 4 25%	5348
	21st to end	Night	26% 17% 5% 11% 5% 4 3 2 4 3 20%	7150

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	64% 7% 11% 13% 5%	4662
	11th to 20th	Day	68% 5% 8% 10% 9%	4680
	21st to end	Day	67% 5% 8% 11% 8% 1	5462
February	1st to 10th	Day	63% 5% 8% 17% 6% 1	1890
	11th to 20th	Day	57% 5% 12% 16% 8% 1	1852
	21st to end	Day	61% 6% 9% 13% 9% 2	1700
March	1st to 10th	Day	60% 5% 8% 12% 12% 2	4671
	11th to 20th	Day	53% 7% 15% 14% 10% 2	5090
	21st to end	Day	50% 4 6% 19% 18% 3	5820
April	1st to 10th	Day	54% 5% 8% 18% 13% 3	2520
	11th to 20th	Day	51% 5% 6% 21% 15% 2	2494
	21st to end	Day	54% 4 8% 15% 15% 3	2677
May	1st to 10th	Day	52% 7% 8% 21% 10% 2	8249
	11th to 20th	Day	46% 8% 12% 21% 11% 1	8225
	21st to end	Day	48% 5% 11% 23% 13% 1	9061
June	1st to 10th	Day	51% 7% 9% 19% 13% 1	2940
	11th to 20th	Day	43% 7% 11% 24% 13% 2	2940
	21st to end	Day	46% 7% 13% 22% 11% 1	2940
July	1st to 10th	Day	40% 7% 15% 26% 11%	8210
	11th to 20th	Day	32% 6% 13% 35% 13% 1	8205
	21st to end	Day	36% 7% 15% 33% 9%	8795
August	1st to 10th	Day	48% 6% 14% 19% 12% 2	6263
	11th to 20th	Day	41% 7% 17% 29% 6%	5990
	21st to end	Day	40% 7% 19% 25% 8%	6085
September	1st to 10th	Day	40% 7% 13% 29% 10%	2520
	11th to 20th	Day	35% 7% 12% 32% 14%	2520
	21st to end	Day	43% 7% 13% 25% 12%	2226
October	1st to 10th	Day	47% 6% 10% 30% 7%	3360
	11th to 20th	Day	46% 6% 14% 22% 11%	3340
	21st to end	Day	49% 6% 18% 19% 7% 1	3399
November	1st to 10th	Day	49% 7% 14% 22% 6% 1	1815
	11th to 20th	Day	57% 7% 12% 15% 8% 1	1680
	21st to end	Day	65% 7% 13% 9% 6% 1	1680
December	1st to 10th	Day	74% 5% 11% 8% 2	2680
	11th to 20th	Day	64% 5% 9% 14% 7%	3066
	21st to end	Day	71% 4 7% 14% 4	4048
January	1st to 10th	Night	67% 6% 11% 12% 5%	8234
	11th to 20th	Night	66% 6% 9% 13% 6%	8280
	21st to end	Night	63% 5% 7% 13% 11% 1	8717
February	1st to 10th	Night	61% 6% 10% 17% 6% 1	2730
	11th to 20th	Night	58% 5% 10% 19% 7% 1	2665
	21st to end	Night	56% 6% 10% 18% 9% 1	2105
March	1st to 10th	Night	60% 4 7% 15% 11% 3	5386
	11th to 20th	Night	50% 7% 17% 16% 8% 2	5090
	21st to end	Night	52% 5% 8% 20% 11% 3	5340
April	1st to 10th	Night	54% 5% 9% 18% 13% 2	2100
	11th to 20th	Night	50% 5% 8% 22% 14% 1	2075
	21st to end	Night	52% 5% 6% 18% 17% 3	1960
May	1st to 10th	Night	53% 7% 10% 20% 8% 3	4666
	11th to 20th	Night	41% 8% 13% 23% 14% 2	4640
	21st to end	Night	46% 7% 13% 20% 14% 1	5115
June	1st to 10th	Night	44% 9% 11% 23% 11% 2	1680
	11th to 20th	Night	39% 6% 11% 25% 17% 2	1680
	21st to end	Night	43% 9% 14% 21% 12% 1	1680
July	1st to 10th	Night	40% 7% 17% 22% 13% 1	4640
	11th to 20th	Night	33% 6% 14% 31% 15%	4632
	21st to end	Night	39% 7% 12% 29% 13%	4967
August	1st to 10th	Night	41% 8% 15% 21% 13% 2	3859
	11th to 20th	Night	38% 7% 17% 31% 7%	4122
	21st to end	Night	39% 7% 18% 27% 8% 1	4994
September	1st to 10th	Night	36% 8% 12% 29% 13% 1	2100
	11th to 20th	Night	33% 6% 14% 35% 11% 1	2100
	21st to end	Night	42% 6% 12% 28% 12%	2391
October	1st to 10th	Night	39% 5% 12% 31% 13%	4040
	11th to 20th	Night	47% 6% 15% 22% 10%	4019
	21st to end	Night	48% 6% 17% 20% 8%	4567
November	1st to 10th	Night	51% 6% 14% 20% 9%	2699
	11th to 20th	Night	55% 7% 12% 18% 8% 1	2940
	21st to end	Night	62% 6% 12% 15% 4	2940
December	1st to 10th	Night	70% 5% 13% 10% 2	4720
	11th to 20th	Night	63% 5% 8% 14% 9% 1	5348
	21st to end	Night	69% 5% 5% 12% 9%	7150

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	22% 21% 36% 18% 3	220
	11th to 20th	Day	29% 20% 36% 10% 5%	220
	21st to end	Day	19% 21% 39% 17% 3	305
February	1st to 10th	Day	27% 24% 32% 12% 5%	330
	11th to 20th	Day	27% 27% 39% 6% 1	330
	21st to end	Day	29% 23% 35% 11% 1	416
March	1st to 10th	Day	28% 21% 34% 14% 2	540
	11th to 20th	Day	29% 19% 33% 16% 3 1	540
	21st to end	Day	33% 21% 28% 13% 4	594
April	1st to 10th	Day	33% 20% 30% 12% 5%	540
	11th to 20th	Day	35% 21% 20% 15% 8% 2	532
	21st to end	Day	29% 19% 33% 13% 5% 1	540
May	1st to 10th	Day	26% 17% 30% 18% 7% 2	543
	11th to 20th	Day	20% 17% 32% 21% 8% 2	567
	21st to end	Day	23% 17% 30% 19% 9% 2	617
June	1st to 10th	Day	23% 14% 32% 21% 9% 1	570
	11th to 20th	Day	17% 15% 33% 22% 11% 2	570
	21st to end	Day	18% 15% 34% 20% 11% 2	570
July	1st to 10th	Day	11% 9% 33% 31% 13% 3	565
	11th to 20th	Day	11% 10% 35% 27% 14% 3	564
	21st to end	Day	14% 10% 33% 28% 12% 3	620
August	1st to 10th	Day	14% 6% 29% 32% 14% 5%	566
	11th to 20th	Day	14% 7% 28% 30% 15% 6%	559
	21st to end	Day	14% 12% 29% 26% 13% 6%	627
September	1st to 10th	Day	16% 11% 31% 22% 12% 8%	570
	11th to 20th	Day	11% 12% 22% 26% 18% 11%	570
	21st to end	Day	18% 13% 31% 20% 14% 6%	570
October	1st to 10th	Day	23% 16% 26% 20% 11% 4	570
	11th to 20th	Day	24% 22% 31% 17% 5% 2	570
	21st to end	Day	27% 20% 27% 19% 6% 1	540
November	1st to 10th	Day	28% 20% 29% 17% 6% 1	389
	11th to 20th	Day	23% 23% 35% 13% 4 2	220
	21st to end	Day	32% 26% 30% 8% 3	220
December	1st to 10th	Day	30% 20% 35% 12% 2	220
	11th to 20th	Day	32% 22% 35% 7% 3	220
	21st to end	Day	28% 23% 32% 11% 4 2	242
January	1st to 10th	Night	25% 18% 36% 18% 3	840
	11th to 20th	Night	27% 20% 28% 20% 5%	840
	21st to end	Night	18% 16% 37% 24% 4	924
February	1st to 10th	Night	20% 18% 37% 21% 4	840
	11th to 20th	Night	19% 19% 40% 19% 3	823
	21st to end	Night	24% 21% 29% 23% 4	692
March	1st to 10th	Night	24% 18% 34% 20% 3	840
	11th to 20th	Night	25% 19% 32% 18% 5%	840
	21st to end	Night	23% 17% 32% 21% 7%	924
April	1st to 10th	Night	28% 16% 30% 22% 4	840
	11th to 20th	Night	24% 19% 30% 20% 7%	831
	21st to end	Night	26% 14% 29% 23% 8% 1	700
May	1st to 10th	Night	23% 10% 30% 26% 10% 1	420
	11th to 20th	Night	21% 10% 35% 26% 7%	414
	21st to end	Night	15% 10% 37% 28% 11%	455
June	1st to 10th	Night	16% 9% 32% 36% 7%	420
	11th to 20th	Night	15% 10% 32% 32% 11% 1	420
	21st to end	Night	19% 9% 26% 33% 13%	420
July	1st to 10th	Night	8% 9% 29% 41% 14% 1	410
	11th to 20th	Night	12% 6% 29% 40% 13%	408
	21st to end	Night	10% 5% 28% 44% 12% 2	460
August	1st to 10th	Night	10% 6% 24% 41% 19% 1	504
	11th to 20th	Night	12% 3 25% 37% 20% 3	624
	21st to end	Night	12% 8% 27% 34% 17% 2	898
September	1st to 10th	Night	14% 8% 30% 30% 17% 2	840
	11th to 20th	Night	15% 7% 21% 31% 23% 3	840
	21st to end	Night	18% 10% 25% 26% 20% 2	840
October	1st to 10th	Night	22% 12% 27% 25% 14% 1	840
	11th to 20th	Night	24% 16% 32% 20% 8% 1	840
	21st to end	Night	25% 16% 28% 25% 6%	913
November	1st to 10th	Night	26% 15% 27% 24% 6%	820
	11th to 20th	Night	24% 18% 33% 16% 9%	840
	21st to end	Night	30% 19% 26% 20% 5%	840
December	1st to 10th	Night	29% 18% 32% 18% 4	840
	11th to 20th	Night	27% 20% 31% 18% 3	840
	21st to end	Night	32% 16% 31% 17% 4	924

Page generated at 2026-10-26 04:37:48. Version ac07

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