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 2025-07-06.

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% 4 9% 5% 5% 4 3 5% 6% 32%	120221
	Night	17% 11% 4 9% 5% 5% 4 3 5% 6% 30%	118536
Transparency	Day	51% 6% 11% 20% 10% 1	123757
	Night	53% 6% 11% 19% 9% 1	123161
Seeing	Day	22% 17% 31% 19% 8% 3	15227
	Night	22% 14% 30% 24% 9% 1	24380

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% 6% 14% 9% 7% 5% 3 4 4 20%	3597
	11th to 20th	Day	12% 16% 6% 14% 9% 5% 5% 3 5% 5% 20%	3570
	21st to end	Day	11% 18% 7% 15% 7% 6% 4 3 4 5% 21%	4216
February	1st to 10th	Day	13% 15% 5% 13% 7% 5% 5% 4 5% 4 23%	1800
	11th to 20th	Day	11% 15% 7% 10% 7% 5% 4 3 4 6% 27%	1753
	21st to end	Day	19% 12% 4 10% 7% 6% 5% 4 5% 4 25%	1621
March	1st to 10th	Day	19% 14% 6% 11% 6% 4 4 2 4 5% 26%	4566
	11th to 20th	Day	12% 12% 4 10% 6% 5% 5% 4 6% 6% 29%	4980
	21st to end	Day	16% 12% 3 8% 5% 4 3 3 4 5% 38%	5694
April	1st to 10th	Day	21% 14% 3 7% 4 4 4 2 5% 5% 32%	2400
	11th to 20th	Day	21% 10% 3 6% 4 4 4 3 4 3 37%	2374
	21st to end	Day	22% 10% 3 8% 4 4 4 3 4 5% 32%	2550
May	1st to 10th	Day	23% 9% 3 8% 5% 4 4 3 5% 6% 29%	6346
	11th to 20th	Day	16% 9% 3 8% 5% 5% 5% 4 5% 7% 32%	6318
	21st to end	Day	20% 8% 3 6% 5% 4 4 4 5% 6% 35%	6949
June	1st to 10th	Day	20% 9% 3 7% 5% 5% 5% 3 6% 6% 32%	2800
	11th to 20th	Day	14% 5% 2 7% 5% 5% 5% 4 6% 7% 40%	2800
	21st to end	Day	18% 7% 2 6% 4 5% 5% 4 7% 8% 33%	2800
July	1st to 10th	Day	12% 7% 3 7% 5% 5% 5% 4 7% 9% 35%	4510
	11th to 20th	Day	13% 4 2 7% 5% 5% 5% 4 7% 8% 41%	4440
	21st to end	Day	11% 5% 2 6% 4 4 4 4 6% 9% 46%	4814
August	1st to 10th	Day	15% 6% 3 8% 5% 5% 4 4 7% 7% 36%	4278
	11th to 20th	Day	17% 6% 2 7% 5% 4 4 4 5% 7% 38%	4044
	21st to end	Day	12% 5% 2 6% 4 4 5% 4 6% 10% 41%	4185
September	1st to 10th	Day	14% 6% 2 6% 5% 5% 5% 3 5% 7% 43%	2280
	11th to 20th	Day	13% 5% 2 6% 4 5% 5% 3 5% 7% 46%	2280
	21st to end	Day	17% 7% 2 6% 4 4 4 3 6% 7% 40%	2015
October	1st to 10th	Day	20% 8% 3 8% 4 5% 4 4 4 5% 35%	1900
	11th to 20th	Day	21% 10% 3 8% 5% 5% 5% 3 5% 7% 28%	1900
	21st to end	Day	25% 12% 3 8% 4 3 4 3 5% 6% 27%	1968
November	1st to 10th	Day	15% 11% 3 7% 6% 4 5% 4 5% 6% 36%	1727
	11th to 20th	Day	17% 12% 5% 9% 5% 6% 5% 4 5% 6% 28%	1600
	21st to end	Day	21% 15% 4 10% 6% 6% 5% 4 5% 5% 21%	1600
December	1st to 10th	Day	22% 20% 6% 12% 6% 5% 5% 3 4 5% 13%	2600
	11th to 20th	Day	16% 17% 5% 12% 6% 5% 4 3 4 3 25%	2986
	21st to end	Day	23% 17% 6% 14% 5% 5% 4 2 3 4 19%	3960
January	1st to 10th	Night	13% 19% 9% 14% 6% 5% 4 3 4 4 18%	6349
	11th to 20th	Night	11% 13% 6% 16% 8% 6% 6% 3 5% 5% 22%	6315
	21st to end	Night	13% 18% 6% 12% 7% 6% 5% 3 4 4 21%	6738
February	1st to 10th	Night	12% 15% 5% 12% 7% 6% 5% 4 5% 6% 23%	2600
	11th to 20th	Night	12% 14% 5% 11% 7% 5% 5% 2 4 6% 28%	2533
	21st to end	Night	15% 12% 5% 10% 6% 5% 4 4 6% 5% 28%	2008
March	1st to 10th	Night	21% 14% 4 10% 5% 4 3 2 3 3 29%	5258
	11th to 20th	Night	11% 11% 4 9% 5% 6% 5% 5% 7% 8% 30%	4979
	21st to end	Night	17% 10% 4 10% 5% 4 4 3 5% 6% 32%	5224
April	1st to 10th	Night	21% 10% 3 8% 5% 4 4 4 4 5% 32%	2000
	11th to 20th	Night	20% 10% 3 7% 4 4 4 3 4 5% 36%	1975
	21st to end	Night	21% 10% 3 8% 5% 5% 4 3 4 5% 33%	1867
May	1st to 10th	Night	23% 9% 3 7% 5% 5% 5% 4 6% 6% 27%	3594
	11th to 20th	Night	15% 6% 2 7% 4 5% 4 3 6% 7% 41%	3575
	21st to end	Night	18% 8% 2 7% 5% 5% 5% 4 6% 7% 34%	3926
June	1st to 10th	Night	15% 6% 3 7% 6% 5% 5% 5% 6% 8% 35%	1600
	11th to 20th	Night	13% 7% 3 6% 4 3 3 4 6% 7% 45%	1600
	21st to end	Night	17% 6% 2 6% 6% 4 4 4 6% 7% 37%	1600
July	1st to 10th	Night	11% 7% 3 8% 6% 6% 6% 4 6% 6% 37%	2560
	11th to 20th	Night	13% 5% 2 6% 5% 4 4 4 5% 8% 44%	2520
	21st to end	Night	10% 5% 2 7% 4 5% 4 4 6% 8% 45%	2739
August	1st to 10th	Night	12% 5% 2 8% 5% 4 5% 4 6% 9% 41%	2649
	11th to 20th	Night	14% 6% 2 7% 4 4 4 4 5% 7% 43%	2785
	21st to end	Night	14% 4 2 6% 4 4 5% 3 6% 8% 43%	3439
September	1st to 10th	Night	12% 6% 2 7% 4 4 4 4 5% 7% 47%	1900
	11th to 20th	Night	14% 4 2 4 4 4 4 3 4 6% 50%	1900
	21st to end	Night	17% 6% 2 6% 4 4 4 4 5% 6% 43%	2163
October	1st to 10th	Night	18% 7% 3 7% 4 4 4 4 4 6% 39%	2280
	11th to 20th	Night	20% 10% 3 7% 4 5% 5% 4 5% 6% 31%	2280
	21st to end	Night	22% 11% 3 7% 5% 4 5% 3 5% 7% 27%	2629
November	1st to 10th	Night	19% 11% 3 7% 5% 4 4 3 5% 5% 34%	2567
	11th to 20th	Night	18% 12% 3 8% 6% 4 5% 4 5% 6% 30%	2800
	21st to end	Night	21% 14% 5% 11% 6% 4 4 3 5% 5% 22%	2800
December	1st to 10th	Night	19% 17% 5% 13% 6% 5% 5% 4 5% 5% 15%	4580
	11th to 20th	Night	21% 15% 4 11% 6% 4 4 3 4 4 25%	5208
	21st to end	Night	26% 17% 5% 11% 5% 4 3 2 4 3 20%	6996

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	65% 8% 9% 12% 6%	3598
	11th to 20th	Day	65% 6% 9% 12% 8%	3600
	21st to end	Day	66% 6% 8% 12% 8% 1	4216
February	1st to 10th	Day	63% 5% 9% 16% 6% 1	1800
	11th to 20th	Day	58% 5% 13% 15% 9% 1	1762
	21st to end	Day	60% 6% 10% 13% 10% 2	1621
March	1st to 10th	Day	60% 5% 8% 12% 13% 2	4569
	11th to 20th	Day	52% 7% 15% 14% 10% 2	4980
	21st to end	Day	50% 4 6% 19% 18% 3	5694
April	1st to 10th	Day	54% 5% 8% 18% 13% 3	2400
	11th to 20th	Day	50% 5% 6% 21% 15% 2	2374
	21st to end	Day	54% 5% 8% 15% 15% 3	2550
May	1st to 10th	Day	54% 6% 8% 19% 10% 3	6357
	11th to 20th	Day	48% 9% 12% 18% 13% 1	6322
	21st to end	Day	49% 6% 12% 20% 12% 1	6949
June	1st to 10th	Day	51% 7% 9% 20% 12% 1	2800
	11th to 20th	Day	42% 7% 11% 24% 13% 2	2800
	21st to end	Day	47% 8% 13% 21% 11% 1	2800
July	1st to 10th	Day	42% 7% 14% 26% 11% 1	4440
	11th to 20th	Day	38% 8% 15% 30% 10%	4365
	21st to end	Day	35% 7% 13% 33% 11%	4661
August	1st to 10th	Day	46% 7% 14% 23% 10%	4264
	11th to 20th	Day	44% 7% 14% 27% 7% 1	4083
	21st to end	Day	37% 7% 16% 28% 11% 1	4185
September	1st to 10th	Day	40% 7% 14% 29% 11%	2280
	11th to 20th	Day	37% 7% 13% 30% 14% 1	2280
	21st to end	Day	43% 7% 14% 25% 10%	2015
October	1st to 10th	Day	48% 6% 10% 29% 7%	3160
	11th to 20th	Day	46% 6% 14% 23% 10%	3140
	21st to end	Day	50% 6% 19% 19% 6%	3219
November	1st to 10th	Day	48% 7% 15% 23% 6% 1	1727
	11th to 20th	Day	56% 7% 12% 15% 8% 1	1600
	21st to end	Day	65% 7% 13% 9% 6% 1	1600
December	1st to 10th	Day	74% 5% 11% 8% 2	2600
	11th to 20th	Day	64% 5% 9% 14% 7%	2986
	21st to end	Day	71% 4 7% 14% 4	3960
January	1st to 10th	Night	68% 6% 10% 11% 4	6349
	11th to 20th	Night	64% 6% 11% 13% 5%	6360
	21st to end	Night	66% 5% 8% 10% 10% 1	6738
February	1st to 10th	Night	61% 6% 10% 16% 6% 1	2600
	11th to 20th	Night	58% 6% 10% 19% 7% 1	2535
	21st to end	Night	55% 6% 11% 18% 9% 1	2008
March	1st to 10th	Night	60% 4 7% 15% 11% 3	5268
	11th to 20th	Night	50% 7% 17% 16% 8% 2	4980
	21st to end	Night	51% 5% 8% 21% 11% 3	5224
April	1st to 10th	Night	53% 5% 9% 18% 13% 2	2000
	11th to 20th	Night	49% 5% 8% 22% 15% 2	1975
	21st to end	Night	53% 5% 6% 17% 16% 3	1867
May	1st to 10th	Night	54% 7% 9% 18% 8% 3	3600
	11th to 20th	Night	40% 8% 15% 20% 15% 2	3576
	21st to end	Night	47% 7% 14% 17% 13% 1	3927
June	1st to 10th	Night	44% 9% 12% 24% 10% 1	1600
	11th to 20th	Night	38% 7% 12% 24% 18% 2	1600
	21st to end	Night	44% 9% 14% 20% 13% 1	1600
July	1st to 10th	Night	44% 7% 15% 20% 13% 1	2520
	11th to 20th	Night	37% 7% 14% 33% 10%	2472
	21st to end	Night	36% 8% 14% 27% 14%	2651
August	1st to 10th	Night	38% 8% 14% 26% 12% 1	2639
	11th to 20th	Night	40% 7% 16% 30% 8%	2812
	21st to end	Night	37% 7% 16% 27% 11% 2	3439
September	1st to 10th	Night	36% 8% 12% 28% 15% 1	1900
	11th to 20th	Night	34% 6% 14% 34% 10% 1	1900
	21st to end	Night	42% 6% 12% 29% 10%	2163
October	1st to 10th	Night	39% 5% 12% 31% 13%	3800
	11th to 20th	Night	47% 6% 16% 23% 9%	3779
	21st to end	Night	49% 7% 18% 19% 7%	4328
November	1st to 10th	Night	51% 6% 14% 20% 9%	2567
	11th to 20th	Night	55% 7% 11% 18% 8% 1	2800
	21st to end	Night	62% 6% 13% 15% 4	2800
December	1st to 10th	Night	70% 6% 13% 10% 2	4580
	11th to 20th	Night	64% 4 8% 14% 9% 1	5208
	21st to end	Night	69% 5% 5% 12% 9%	6996

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% 22% 36% 18% 4	200
	11th to 20th	Day	29% 17% 38% 11% 5% 1	200
	21st to end	Day	21% 21% 38% 17% 4	277
February	1st to 10th	Day	29% 27% 30% 11% 3	300
	11th to 20th	Day	28% 28% 38% 5% 1	300
	21st to end	Day	30% 23% 35% 11% 1	385
March	1st to 10th	Day	28% 20% 35% 15% 3	500
	11th to 20th	Day	26% 20% 34% 16% 3 1	500
	21st to end	Day	32% 21% 28% 14% 4	550
April	1st to 10th	Day	32% 21% 29% 12% 5%	500
	11th to 20th	Day	33% 21% 21% 15% 8% 2	492
	21st to end	Day	29% 19% 33% 12% 5% 1	500
May	1st to 10th	Day	27% 15% 31% 18% 7% 2	503
	11th to 20th	Day	19% 17% 32% 22% 8% 3	527
	21st to end	Day	22% 16% 30% 20% 10% 2	573
June	1st to 10th	Day	23% 14% 32% 21% 9% 1	530
	11th to 20th	Day	17% 15% 32% 23% 11% 3	530
	21st to end	Day	18% 16% 33% 20% 11% 2	530
July	1st to 10th	Day	10% 9% 32% 32% 13% 3	505
	11th to 20th	Day	11% 10% 34% 27% 14% 4	484
	21st to end	Day	14% 9% 34% 29% 12% 3	532
August	1st to 10th	Day	15% 6% 29% 31% 14% 5%	486
	11th to 20th	Day	13% 7% 27% 31% 16% 6%	479
	21st to end	Day	13% 12% 28% 26% 13% 6%	539
September	1st to 10th	Day	15% 11% 31% 22% 14% 8%	490
	11th to 20th	Day	12% 11% 23% 24% 19% 11%	490
	21st to end	Day	18% 14% 29% 20% 13% 6%	490
October	1st to 10th	Day	24% 16% 25% 21% 11% 4	490
	11th to 20th	Day	24% 22% 30% 17% 6% 2	490
	21st to end	Day	29% 21% 27% 19% 4 1	474
November	1st to 10th	Day	26% 19% 29% 18% 6% 1	361
	11th to 20th	Day	24% 24% 34% 13% 4 2	200
	21st to end	Day	31% 26% 31% 9% 3 1	200
December	1st to 10th	Day	30% 21% 34% 13% 3	200
	11th to 20th	Day	33% 23% 33% 8% 3 1	200
	21st to end	Day	28% 22% 33% 12% 4 2	220
January	1st to 10th	Night	25% 18% 37% 17% 3	800
	11th to 20th	Night	26% 20% 28% 20% 5% 1	800
	21st to end	Night	18% 16% 37% 24% 5%	880
February	1st to 10th	Night	21% 18% 37% 21% 3	800
	11th to 20th	Night	20% 20% 39% 19% 3	783
	21st to end	Night	24% 20% 29% 23% 4	660
March	1st to 10th	Night	25% 18% 34% 21% 3	800
	11th to 20th	Night	24% 20% 33% 19% 5% 1	800
	21st to end	Night	23% 17% 31% 21% 8%	880
April	1st to 10th	Night	27% 16% 30% 22% 5%	800
	11th to 20th	Night	24% 19% 29% 20% 8% 1	791
	21st to end	Night	26% 14% 28% 23% 8% 1	667
May	1st to 10th	Night	24% 9% 31% 26% 10% 1	400
	11th to 20th	Night	21% 10% 34% 27% 7% 1	394
	21st to end	Night	14% 9% 37% 28% 11%	433
June	1st to 10th	Night	16% 9% 33% 35% 8%	400
	11th to 20th	Night	15% 9% 32% 32% 11% 1	400
	21st to end	Night	19% 9% 27% 32% 13%	400
July	1st to 10th	Night	8% 9% 28% 41% 14% 1	380
	11th to 20th	Night	11% 6% 28% 41% 14% 1	368
	21st to end	Night	9% 5% 27% 45% 12% 2	416
August	1st to 10th	Night	10% 7% 23% 41% 19% 1	456
	11th to 20th	Night	12% 2 25% 36% 22% 3	564
	21st to end	Night	13% 8% 26% 34% 18% 2	812
September	1st to 10th	Night	14% 7% 29% 30% 18% 2	760
	11th to 20th	Night	16% 6% 21% 30% 23% 4	760
	21st to end	Night	19% 10% 24% 25% 20% 2	760
October	1st to 10th	Night	23% 11% 26% 24% 14% 1	760
	11th to 20th	Night	24% 16% 31% 20% 9% 1	760
	21st to end	Night	26% 18% 28% 23% 5%	836
November	1st to 10th	Night	26% 15% 28% 25% 7%	780
	11th to 20th	Night	24% 18% 34% 15% 9% 1	800
	21st to end	Night	30% 19% 25% 20% 6%	800
December	1st to 10th	Night	30% 17% 32% 18% 4	800
	11th to 20th	Night	27% 19% 31% 18% 4 1	800
	21st to end	Night	31% 16% 31% 17% 4	880

Page generated at 2025-07-03 01:30:12. Version ac07

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