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 2024-11-03.

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% 10% 3 8% 5% 5% 4 3 5% 6% 33%	101564
	Night	17% 11% 4 9% 5% 5% 4 3 5% 6% 32%	97406
Transparency	Day	50% 7% 12% 20% 10% 1	101322
	Night	52% 7% 12% 19% 9% 1	97268
Seeing	Day	22% 16% 31% 20% 9% 3	14436
	Night	22% 14% 30% 24% 9% 1	23540

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% 16% 6% 12% 7% 5% 5% 3 5% 4 22%	2517
	11th to 20th	Day	13% 15% 6% 15% 7% 5% 5% 3 5% 5% 21%	2520
	21st to end	Day	15% 19% 7% 14% 7% 6% 4 3 3 4 18%	2944
February	1st to 10th	Day	13% 15% 6% 13% 7% 5% 5% 4 5% 4 23%	1710
	11th to 20th	Day	11% 15% 7% 10% 7% 5% 4 3 4 6% 28%	1663
	21st to end	Day	19% 12% 3 10% 6% 6% 5% 4 5% 4 25%	1542
March	1st to 10th	Day	20% 15% 5% 10% 5% 4 4 2 4 5% 27%	3178
	11th to 20th	Day	12% 16% 5% 11% 6% 5% 4 3 4 5% 28%	3480
	21st to end	Day	12% 9% 3 8% 5% 4 3 3 4 6% 43%	3974
April	1st to 10th	Day	22% 14% 3 6% 4 4 4 3 5% 5% 31%	2280
	11th to 20th	Day	22% 10% 3 6% 4 4 4 3 4 4 37%	2254
	21st to end	Day	22% 10% 3 8% 4 4 4 3 4 5% 32%	2422
May	1st to 10th	Day	21% 8% 3 8% 5% 4 4 4 5% 7% 32%	4426
	11th to 20th	Day	16% 9% 3 8% 5% 5% 5% 3 5% 8% 33%	4398
	21st to end	Day	15% 7% 3 6% 5% 5% 4 4 6% 7% 39%	4837
June	1st to 10th	Day	20% 9% 3 7% 5% 5% 5% 3 6% 6% 31%	2660
	11th to 20th	Day	15% 5% 2 7% 5% 4 5% 4 6% 7% 39%	2660
	21st to end	Day	18% 7% 2 6% 4 5% 5% 5% 7% 8% 32%	2660
July	1st to 10th	Day	12% 7% 3 7% 5% 5% 5% 4 7% 9% 35%	4440
	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	14% 11% 3 7% 5% 4 5% 4 5% 6% 36%	1657
	11th to 20th	Day	18% 12% 5% 9% 5% 5% 5% 4 5% 5% 28%	1520
	21st to end	Day	21% 15% 4 10% 6% 5% 4 4 5% 5% 21%	1520
December	1st to 10th	Day	21% 19% 6% 12% 6% 4 4 3 4 5% 15%	1520
	11th to 20th	Day	20% 16% 4 10% 5% 5% 4 3 5% 4 26%	1906
	21st to end	Day	28% 17% 6% 13% 4 3 3 2 3 3 19%	2772
January	1st to 10th	Night	15% 17% 8% 12% 6% 5% 4 3 5% 5% 19%	4429
	11th to 20th	Night	12% 13% 5% 14% 8% 6% 6% 3 5% 5% 23%	4440
	21st to end	Night	16% 20% 6% 10% 7% 6% 4 3 4 4 20%	4710
February	1st to 10th	Night	12% 15% 6% 11% 7% 6% 5% 4 4 6% 23%	2470
	11th to 20th	Night	13% 13% 5% 11% 7% 5% 5% 2 4 6% 29%	2403
	21st to end	Night	16% 12% 4 10% 6% 5% 4 4 6% 5% 29%	1911
March	1st to 10th	Night	21% 13% 3 8% 5% 4 3 2 4 4 32%	3646
	11th to 20th	Night	15% 15% 5% 10% 5% 5% 4 4 5% 6% 25%	3479
	21st to end	Night	14% 9% 3 8% 5% 5% 4 3 5% 7% 38%	3644
April	1st to 10th	Night	21% 10% 3 8% 5% 4 4 3 4 5% 33%	1900
	11th to 20th	Night	20% 9% 3 7% 4 4 4 3 4 5% 36%	1875
	21st to end	Night	21% 10% 3 8% 5% 5% 4 3 4 5% 33%	1774
May	1st to 10th	Night	20% 9% 3 7% 5% 5% 4 4 6% 6% 32%	2514
	11th to 20th	Night	19% 8% 3 7% 4 5% 4 3 5% 7% 35%	2495
	21st to end	Night	12% 7% 2 7% 5% 5% 5% 4 6% 7% 40%	2738
June	1st to 10th	Night	15% 6% 3 7% 6% 5% 5% 5% 6% 8% 34%	1520
	11th to 20th	Night	13% 7% 3 7% 4 3 3 4 6% 7% 44%	1520
	21st to end	Night	17% 7% 2 6% 5% 4 4 4 6% 8% 37%	1520
July	1st to 10th	Night	11% 7% 3 8% 6% 6% 6% 4 6% 6% 37%	2520
	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% 3 4 3 5% 5% 34%	2462
	11th to 20th	Night	18% 12% 3 8% 6% 4 5% 4 5% 6% 29%	2660
	21st to end	Night	21% 14% 5% 10% 6% 4 4 3 5% 5% 23%	2660
December	1st to 10th	Night	20% 18% 6% 11% 6% 4 5% 4 4 5% 17%	2660
	11th to 20th	Night	20% 16% 4 10% 6% 4 3 3 4 4 25%	3288
	21st to end	Night	29% 18% 5% 11% 4 4 3 2 3 3 17%	4884

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	62% 10% 12% 9% 6%	2518
	11th to 20th	Day	64% 7% 9% 12% 6% 1	2520
	21st to end	Day	70% 7% 8% 9% 5% 1	2944
February	1st to 10th	Day	64% 5% 9% 16% 5% 1	1710
	11th to 20th	Day	57% 5% 13% 15% 9% 1	1672
	21st to end	Day	59% 6% 10% 13% 10% 2	1542
March	1st to 10th	Day	60% 5% 9% 16% 10% 1	3181
	11th to 20th	Day	56% 7% 11% 15% 10% 2	3480
	21st to end	Day	42% 5% 8% 24% 18% 4	3974
April	1st to 10th	Day	54% 5% 8% 18% 12% 3	2280
	11th to 20th	Day	50% 6% 7% 21% 15% 2	2254
	21st to end	Day	55% 4 8% 14% 15% 4	2422
May	1st to 10th	Day	49% 8% 9% 20% 12% 2	4440
	11th to 20th	Day	45% 10% 14% 19% 10% 1	4402
	21st to end	Day	44% 7% 12% 20% 15% 2	4837
June	1st to 10th	Day	52% 8% 10% 20% 11% 1	2660
	11th to 20th	Day	42% 7% 11% 23% 13% 3	2660
	21st to end	Day	48% 8% 13% 20% 11% 1	2660
July	1st to 10th	Day	42% 7% 14% 25% 11% 1	4370
	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	50% 7% 11% 22% 10% 1	1900
	11th to 20th	Day	54% 7% 14% 17% 7% 1	1900
	21st to end	Day	58% 6% 13% 15% 7% 1	1968
November	1st to 10th	Day	48% 7% 15% 23% 6% 1	1657
	11th to 20th	Day	56% 7% 13% 14% 8% 1	1520
	21st to end	Day	64% 7% 12% 9% 6% 1	1520
December	1st to 10th	Day	70% 7% 11% 9% 3 1	1520
	11th to 20th	Day	61% 7% 13% 13% 6%	1906
	21st to end	Day	74% 3 7% 13% 3	2772
January	1st to 10th	Night	65% 8% 14% 10% 3	4429
	11th to 20th	Night	62% 8% 14% 12% 4	4440
	21st to end	Night	68% 6% 9% 10% 6%	4710
February	1st to 10th	Night	61% 6% 10% 15% 6% 1	2470
	11th to 20th	Night	57% 6% 10% 19% 7% 1	2405
	21st to end	Night	55% 6% 11% 18% 9% 1	1911
March	1st to 10th	Night	56% 6% 10% 19% 8% 1	3656
	11th to 20th	Night	57% 7% 13% 15% 7% 1	3480
	21st to end	Night	43% 7% 9% 22% 15% 4	3644
April	1st to 10th	Night	53% 5% 9% 18% 13% 2	1900
	11th to 20th	Night	49% 5% 8% 22% 14% 2	1875
	21st to end	Night	54% 5% 6% 16% 16% 3	1774
May	1st to 10th	Night	49% 8% 10% 20% 9% 3	2520
	11th to 20th	Night	44% 10% 13% 21% 10% 2	2496
	21st to end	Night	40% 9% 13% 20% 17% 2	2739
June	1st to 10th	Night	44% 9% 12% 23% 10% 1	1520
	11th to 20th	Night	38% 7% 11% 24% 17% 2	1520
	21st to end	Night	43% 9% 15% 19% 13% 1	1520
July	1st to 10th	Night	44% 7% 15% 19% 13% 1	2480
	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	46% 6% 11% 23% 14%	2280
	11th to 20th	Night	53% 8% 12% 19% 8%	2280
	21st to end	Night	56% 7% 14% 15% 8%	2629
November	1st to 10th	Night	50% 6% 14% 20% 9%	2462
	11th to 20th	Night	55% 7% 12% 17% 8% 1	2660
	21st to end	Night	62% 6% 13% 14% 4	2660
December	1st to 10th	Night	69% 6% 11% 12% 3	2660
	11th to 20th	Night	63% 5% 9% 15% 7% 1	3288
	21st to end	Night	73% 5% 6% 12% 3	4884

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% 33% 19% 4	180
	11th to 20th	Day	29% 18% 36% 11% 5%	180
	21st to end	Day	22% 19% 37% 18% 4	249
February	1st to 10th	Day	28% 27% 31% 11% 3	270
	11th to 20th	Day	28% 27% 39% 5% 1	270
	21st to end	Day	31% 23% 33% 12% 1	354
March	1st to 10th	Day	27% 19% 35% 15% 3	460
	11th to 20th	Day	25% 20% 35% 17% 3 1	460
	21st to end	Day	31% 22% 28% 14% 5%	506
April	1st to 10th	Day	31% 20% 31% 13% 6%	460
	11th to 20th	Day	33% 21% 20% 16% 8% 2	452
	21st to end	Day	28% 19% 32% 13% 6% 1	460
May	1st to 10th	Day	27% 15% 30% 19% 8% 2	463
	11th to 20th	Day	19% 17% 31% 23% 8% 3	487
	21st to end	Day	20% 17% 31% 20% 10% 2	529
June	1st to 10th	Day	23% 12% 32% 22% 9% 1	490
	11th to 20th	Day	17% 15% 31% 23% 11% 3	490
	21st to end	Day	19% 15% 32% 21% 11% 2	490
July	1st to 10th	Day	11% 9% 31% 33% 13% 4	485
	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	25% 19% 30% 18% 7% 1	339
	11th to 20th	Day	24% 23% 34% 12% 4 2	180
	21st to end	Day	29% 27% 31% 9% 3 1	180
December	1st to 10th	Day	29% 21% 36% 12% 2	180
	11th to 20th	Day	33% 23% 33% 8% 2 1	180
	21st to end	Day	29% 24% 32% 11% 4 1	198
January	1st to 10th	Night	25% 17% 37% 18% 3	760
	11th to 20th	Night	26% 20% 28% 20% 5%	760
	21st to end	Night	19% 15% 37% 24% 4	836
February	1st to 10th	Night	21% 18% 37% 21% 3	760
	11th to 20th	Night	19% 19% 39% 19% 3	743
	21st to end	Night	24% 20% 29% 23% 4	628
March	1st to 10th	Night	24% 17% 34% 21% 3	760
	11th to 20th	Night	23% 20% 33% 18% 6% 1	760
	21st to end	Night	22% 17% 32% 22% 8%	836
April	1st to 10th	Night	27% 16% 30% 22% 5%	760
	11th to 20th	Night	24% 20% 29% 19% 7%	751
	21st to end	Night	26% 14% 28% 23% 8% 1	634
May	1st to 10th	Night	23% 9% 30% 26% 11% 1	380
	11th to 20th	Night	21% 10% 33% 28% 7% 1	374
	21st to end	Night	14% 9% 36% 28% 12%	411
June	1st to 10th	Night	16% 9% 33% 35% 8%	380
	11th to 20th	Night	15% 9% 31% 32% 12% 1	380
	21st to end	Night	19% 9% 25% 33% 13%	380
July	1st to 10th	Night	8% 8% 28% 41% 14% 1	370
	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% 14% 28% 25% 7%	749
	11th to 20th	Night	24% 18% 33% 15% 9% 1	760
	21st to end	Night	30% 18% 26% 20% 6%	760
December	1st to 10th	Night	30% 18% 32% 17% 3	760
	11th to 20th	Night	27% 19% 32% 18% 4 1	760
	21st to end	Night	32% 16% 31% 17% 3	836

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