Bill's Doghouse Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bill's Doghouse Observatory clear sky chart from 2005-11-06 to 2025-02-06.

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	14% 9% 4 8% 5% 4 4 4 5% 7% 35%	108365
	Night	15% 10% 4 8% 5% 4 4 3 5% 6% 36%	110007
Transparency	Day	46% 6% 11% 22% 13% 2	112022
	Night	47% 5% 10% 21% 14% 2	114490
Seeing	Day	17% 9% 26% 24% 16% 7%	15814
	Night	18% 8% 28% 29% 14% 2	25741

By Month

Percentage Cloud Cover SE (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% 15% 9% 15% 7% 4 3 3 5% 5% 20%	3617
	11th to 20th	Day	12% 14% 7% 15% 8% 7% 5% 4 3 3 21%	3620
	21st to end	Day	21% 15% 7% 13% 5% 4 3 3 3 4 22%	4309
February	1st to 10th	Day	18% 14% 6% 10% 6% 4 4 3 4 5% 25%	1910
	11th to 20th	Day	15% 12% 4 12% 6% 5% 4 3 4 6% 28%	1848
	21st to end	Day	18% 14% 5% 10% 5% 3 4 3 4 5% 30%	1570
March	1st to 10th	Day	21% 19% 6% 8% 4 4 3 2 4 4 26%	3120
	11th to 20th	Day	14% 8% 3 7% 5% 3 4 4 5% 7% 41%	3411
	21st to end	Day	18% 10% 5% 9% 5% 5% 4 4 5% 7% 29%	3902
April	1st to 10th	Day	15% 12% 3 8% 5% 4 4 3 5% 7% 33%	2280
	11th to 20th	Day	17% 9% 3 6% 4 4 4 4 5% 6% 38%	2259
	21st to end	Day	20% 9% 3 7% 4 4 4 4 4 7% 34%	2470
May	1st to 10th	Day	20% 10% 3 7% 5% 5% 5% 4 6% 7% 28%	4082
	11th to 20th	Day	19% 7% 2 6% 4 3 4 3 5% 7% 38%	4081
	21st to end	Day	10% 6% 3 7% 6% 6% 5% 5% 8% 10% 34%	4476
June	1st to 10th	Day	11% 7% 2 6% 5% 5% 5% 5% 6% 8% 41%	2650
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 7% 8% 44%	2660
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 5% 7% 9% 41%	2660
July	1st to 10th	Day	13% 6% 3 7% 4 4 5% 5% 7% 10% 35%	4440
	11th to 20th	Day	7% 4 2 5% 4 4 5% 4 8% 11% 47%	4440
	21st to end	Day	9% 6% 3 8% 5% 6% 6% 5% 8% 9% 36%	4574
August	1st to 10th	Day	7% 5% 2 6% 5% 4 5% 4 7% 9% 46%	4104
	11th to 20th	Day	9% 6% 2 6% 5% 5% 5% 5% 7% 11% 39%	3954
	21st to end	Day	7% 5% 2 4 3 4 5% 3 6% 9% 51%	4180
September	1st to 10th	Day	11% 6% 3 7% 3 5% 5% 3 5% 7% 46%	2218
	11th to 20th	Day	11% 5% 2 5% 3 4 4 4 7% 9% 47%	2090
	21st to end	Day	15% 6% 2 5% 4 3 3 3 5% 6% 47%	2090
October	1st to 10th	Day	12% 5% 3 6% 5% 3 4 3 3 7% 49%	2090
	11th to 20th	Day	13% 7% 2 5% 3 4 5% 4 6% 7% 44%	1954
	21st to end	Day	20% 11% 3 7% 4 3 3 3 5% 7% 34%	1881
November	1st to 10th	Day	9% 7% 3 6% 4 3 4 3 5% 6% 51%	1762
	11th to 20th	Day	16% 12% 4 8% 5% 3 4 3 5% 6% 34%	1800
	21st to end	Day	19% 13% 4 9% 4 4 3 3 4 6% 31%	1800
December	1st to 10th	Day	16% 12% 4 8% 4 3 3 3 4 5% 37%	2930
	11th to 20th	Day	17% 15% 6% 10% 5% 5% 4 3 4 5% 24%	3151
	21st to end	Day	25% 19% 8% 10% 5% 4 3 3 4 6% 13%	3982
January	1st to 10th	Night	16% 16% 8% 15% 7% 4 4 3 5% 5% 18%	6348
	11th to 20th	Night	12% 18% 8% 15% 7% 7% 5% 3 3 4 18%	6360
	21st to end	Night	21% 13% 5% 8% 4 4 4 3 4 6% 27%	6650
February	1st to 10th	Night	20% 12% 5% 9% 6% 5% 4 3 5% 4 28%	2379
	11th to 20th	Night	14% 12% 4 10% 6% 4 4 3 6% 7% 31%	2218
	21st to end	Night	19% 13% 4 9% 5% 4 3 3 5% 5% 30%	1884
March	1st to 10th	Night	21% 13% 3 7% 3 4 3 3 4 6% 34%	3733
	11th to 20th	Night	13% 8% 3 5% 4 4 4 3 5% 6% 46%	3549
	21st to end	Night	18% 9% 3 7% 5% 4 3 3 5% 6% 38%	3758
April	1st to 10th	Night	14% 10% 4 7% 4 4 4 3 5% 7% 37%	1900
	11th to 20th	Night	16% 9% 2 6% 5% 4 4 3 6% 7% 39%	1868
	21st to end	Night	16% 8% 3 7% 5% 4 5% 4 6% 6% 35%	1710
May	1st to 10th	Night	19% 11% 3 9% 5% 5% 5% 3 6% 6% 28%	2813
	11th to 20th	Night	19% 7% 2 5% 4 4 4 3 5% 7% 40%	2812
	21st to end	Night	10% 5% 2 6% 5% 4 4 3 6% 9% 45%	3079
June	1st to 10th	Night	10% 6% 2 5% 5% 5% 5% 3 6% 6% 49%	1525
	11th to 20th	Night	9% 5% 2 6% 4 4 4 4 5% 10% 47%	1520
	21st to end	Night	6% 4 2 6% 5% 5% 6% 5% 7% 11% 45%	1520
July	1st to 10th	Night	10% 5% 2 7% 4 4 4 3 6% 9% 47%	2530
	11th to 20th	Night	6% 4 1 4 3 3 4 4 7% 9% 55%	2530
	21st to end	Night	11% 7% 2 6% 4 5% 5% 4 8% 10% 38%	2981
August	1st to 10th	Night	9% 6% 2 6% 4 4 5% 3 5% 9% 48%	2825
	11th to 20th	Night	7% 7% 2 7% 5% 5% 5% 4 6% 8% 45%	2871
	21st to end	Night	4 3 1 6% 4 5% 5% 4 7% 8% 53%	3476
September	1st to 10th	Night	11% 6% 2 5% 3 4 4 3 5% 7% 49%	1942
	11th to 20th	Night	9% 3 1 5% 4 3 4 3 5% 8% 55%	2090
	21st to end	Night	13% 6% 2 5% 5% 3 4 3 5% 6% 48%	2090
October	1st to 10th	Night	10% 4 2 6% 3 4 4 3 5% 6% 55%	2090
	11th to 20th	Night	16% 7% 3 6% 4 3 4 3 4 6% 45%	2223
	21st to end	Night	18% 7% 3 6% 4 4 4 3 5% 6% 40%	2717
November	1st to 10th	Night	13% 8% 3 6% 3 3 4 3 5% 5% 48%	2536
	11th to 20th	Night	15% 10% 3 7% 5% 4 4 3 5% 7% 37%	2600
	21st to end	Night	19% 14% 4 9% 4 4 4 4 4 5% 30%	2600
December	1st to 10th	Night	16% 11% 4 8% 5% 4 3 3 4 6% 37%	4250
	11th to 20th	Night	19% 15% 6% 11% 5% 4 4 3 4 5% 24%	5034
	21st to end	Night	26% 18% 7% 11% 5% 4 4 3 4 4 16%	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	66% 4 5% 18% 6%	3618
	11th to 20th	Day	70% 3 8% 9% 8% 2	3620
	21st to end	Day	68% 3 8% 13% 7% 2	4309
February	1st to 10th	Day	62% 5% 9% 13% 10% 1	1910
	11th to 20th	Day	57% 4 9% 19% 9%	1858
	21st to end	Day	56% 6% 9% 19% 8% 2	1570
March	1st to 10th	Day	63% 4 7% 17% 9% 1	3120
	11th to 20th	Day	42% 5% 11% 28% 12% 1	3411
	21st to end	Day	53% 7% 13% 22% 5% 1	3902
April	1st to 10th	Day	51% 6% 11% 19% 13% 1	2280
	11th to 20th	Day	46% 6% 11% 23% 11% 3	2259
	21st to end	Day	49% 6% 11% 21% 10% 2	2470
May	1st to 10th	Day	51% 9% 12% 21% 7%	4120
	11th to 20th	Day	45% 7% 13% 24% 10%	4085
	21st to end	Day	38% 9% 15% 21% 15% 1	4489
June	1st to 10th	Day	39% 7% 12% 25% 16% 2	2650
	11th to 20th	Day	35% 7% 12% 25% 19% 2	2660
	21st to end	Day	37% 9% 16% 19% 16% 4	2660
July	1st to 10th	Day	43% 6% 12% 21% 17% 2	4371
	11th to 20th	Day	28% 8% 15% 28% 20% 1	4365
	21st to end	Day	41% 9% 15% 17% 14% 3	4429
August	1st to 10th	Day	31% 8% 17% 29% 13% 1	4091
	11th to 20th	Day	36% 8% 13% 29% 13% 1	3993
	21st to end	Day	28% 7% 14% 30% 17% 4	4179
September	1st to 10th	Day	37% 6% 11% 23% 18% 5%	2218
	11th to 20th	Day	33% 6% 11% 25% 22% 4	2090
	21st to end	Day	38% 4 9% 25% 23% 1	2090
October	1st to 10th	Day	25% 4 8% 29% 32% 2	3480
	11th to 20th	Day	32% 5% 10% 28% 25% 2	3222
	21st to end	Day	41% 3 10% 23% 20% 2	3081
November	1st to 10th	Day	35% 4 13% 28% 18% 3	1762
	11th to 20th	Day	51% 5% 9% 19% 13% 4	1800
	21st to end	Day	54% 4 10% 21% 9% 2	1800
December	1st to 10th	Day	50% 3 10% 26% 10%	2930
	11th to 20th	Day	63% 5% 9% 17% 6%	3148
	21st to end	Day	73% 5% 8% 10% 4	3982
January	1st to 10th	Night	67% 5% 7% 14% 7%	6348
	11th to 20th	Night	71% 4 7% 10% 7% 2	6360
	21st to end	Night	59% 4 9% 19% 8% 1	6650
February	1st to 10th	Night	59% 4 10% 17% 8% 1	2379
	11th to 20th	Night	52% 5% 11% 18% 12% 1	2219
	21st to end	Night	57% 5% 10% 16% 10% 2	1884
March	1st to 10th	Night	52% 4 9% 23% 11% 1	3733
	11th to 20th	Night	37% 5% 12% 26% 17% 2	3549
	21st to end	Night	46% 6% 11% 28% 8% 1	3758
April	1st to 10th	Night	45% 6% 10% 24% 13% 2	1900
	11th to 20th	Night	44% 5% 10% 20% 17% 4	1868
	21st to end	Night	46% 7% 10% 21% 12% 4	1710
May	1st to 10th	Night	54% 8% 10% 20% 6% 2	2840
	11th to 20th	Night	43% 7% 13% 27% 9% 1	2813
	21st to end	Night	32% 9% 16% 25% 14% 4	3087
June	1st to 10th	Night	34% 5% 11% 26% 20% 3	1525
	11th to 20th	Night	33% 7% 13% 24% 20% 4	1520
	21st to end	Night	30% 9% 15% 24% 17% 4	1520
July	1st to 10th	Night	35% 6% 11% 27% 16% 6%	2490
	11th to 20th	Night	24% 6% 16% 31% 22% 2	2482
	21st to end	Night	39% 7% 14% 22% 15% 4	2886
August	1st to 10th	Night	31% 7% 16% 32% 13% 1	2814
	11th to 20th	Night	35% 6% 12% 27% 18% 1	2898
	21st to end	Night	27% 7% 13% 28% 22% 3	3476
September	1st to 10th	Night	33% 6% 11% 22% 20% 7%	1942
	11th to 20th	Night	28% 6% 10% 27% 26% 4	2090
	21st to end	Night	35% 6% 10% 24% 22% 3	2090
October	1st to 10th	Night	21% 4 7% 28% 38% 2	3480
	11th to 20th	Night	29% 3 10% 23% 33% 1	3694
	21st to end	Night	35% 4 8% 26% 24% 4	4467
November	1st to 10th	Night	38% 4 10% 23% 22% 3	2536
	11th to 20th	Night	46% 4 9% 22% 16% 3	2600
	21st to end	Night	57% 4 10% 19% 9% 1	2600
December	1st to 10th	Night	49% 4 11% 24% 12%	4250
	11th to 20th	Night	62% 4 10% 15% 8% 1	5036
	21st to end	Night	72% 4 9% 11% 3	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% 17% 35% 22% 4 1	300
	11th to 20th	Day	22% 21% 35% 17% 5%	300
	21st to end	Day	28% 15% 34% 19% 4 1	330
February	1st to 10th	Day	28% 14% 36% 18% 4	285
	11th to 20th	Day	24% 20% 33% 19% 5%	270
	21st to end	Day	26% 16% 37% 17% 3	225
March	1st to 10th	Day	23% 21% 34% 18% 3	270
	11th to 20th	Day	24% 16% 34% 18% 6% 1	417
	21st to end	Day	30% 14% 31% 19% 7%	506
April	1st to 10th	Day	21% 15% 32% 22% 9% 3	460
	11th to 20th	Day	21% 13% 30% 21% 11% 4	452
	21st to end	Day	25% 12% 34% 20% 8% 2	460
May	1st to 10th	Day	23% 11% 31% 23% 8% 4	463
	11th to 20th	Day	20% 7% 30% 20% 15% 7%	487
	21st to end	Day	14% 4 26% 26% 17% 13%	529
June	1st to 10th	Day	12% 5% 26% 29% 22% 6%	670
	11th to 20th	Day	13% 3 23% 30% 24% 7%	680
	21st to end	Day	11% 5% 27% 29% 20% 8%	680
July	1st to 10th	Day	13% 3 16% 26% 25% 18%	671
	11th to 20th	Day	8% 3 20% 32% 23% 14%	668
	21st to end	Day	11% 3 15% 28% 29% 14%	601
August	1st to 10th	Day	9% 2 13% 29% 29% 17%	486
	11th to 20th	Day	14% 3 18% 27% 26% 12%	479
	21st to end	Day	9% 4 11% 28% 34% 15%	539
September	1st to 10th	Day	11% 3 17% 25% 31% 11%	490
	11th to 20th	Day	11% 1 12% 29% 30% 17%	490
	21st to end	Day	18% 8% 18% 22% 23% 10%	490
October	1st to 10th	Day	12% 4 23% 34% 18% 9%	490
	11th to 20th	Day	12% 14% 32% 25% 14% 3	466
	21st to end	Day	29% 11% 35% 20% 5%	330
November	1st to 10th	Day	15% 13% 33% 23% 13% 3	300
	11th to 20th	Day	23% 14% 31% 21% 9% 2	300
	21st to end	Day	26% 11% 38% 22% 4	300
December	1st to 10th	Day	19% 18% 40% 16% 6% 1	300
	11th to 20th	Day	23% 14% 38% 19% 4 1	300
	21st to end	Day	29% 16% 34% 16% 5%	330
January	1st to 10th	Night	24% 14% 34% 23% 5%	1000
	11th to 20th	Night	26% 14% 38% 19% 3	1000
	21st to end	Night	23% 12% 38% 23% 4	949
February	1st to 10th	Night	26% 10% 37% 25% 2	781
	11th to 20th	Night	21% 14% 39% 24% 2	743
	21st to end	Night	25% 11% 39% 22% 3	628
March	1st to 10th	Night	23% 11% 35% 24% 6%	760
	11th to 20th	Night	21% 12% 35% 25% 6% 1	760
	21st to end	Night	25% 10% 33% 26% 6% 1	802
April	1st to 10th	Night	17% 11% 37% 27% 7% 1	570
	11th to 20th	Night	19% 9% 33% 29% 9% 1	563
	21st to end	Night	21% 6% 40% 22% 10% 1	570
May	1st to 10th	Night	21% 8% 34% 28% 9% 1	570
	11th to 20th	Night	20% 4 23% 33% 17% 3	561
	21st to end	Night	10% 4 23% 38% 24% 2	617
June	1st to 10th	Night	11% 3 23% 41% 22%	570
	11th to 20th	Night	11% 4 18% 42% 22% 2	570
	21st to end	Night	8% 2 23% 38% 28% 2	570
July	1st to 10th	Night	11% 2 12% 35% 33% 7%	555
	11th to 20th	Night	9% 4 12% 39% 31% 5%	552
	21st to end	Night	11% 1 11% 42% 33% 3	624
August	1st to 10th	Night	9% 2 11% 39% 35% 4	567
	11th to 20th	Night	7% 3 12% 41% 32% 6%	564
	21st to end	Night	7% 2 12% 34% 39% 6%	627
September	1st to 10th	Night	13% 3 13% 35% 32% 5%	612
	11th to 20th	Night	10% 2 14% 34% 33% 6%	760
	21st to end	Night	14% 5% 21% 34% 22% 4	760
October	1st to 10th	Night	11% 5% 25% 33% 21% 5%	760
	11th to 20th	Night	19% 10% 29% 27% 14% 1	760
	21st to end	Night	21% 9% 35% 25% 9%	836
November	1st to 10th	Night	17% 9% 33% 27% 12% 1	780
	11th to 20th	Night	19% 14% 32% 27% 7% 1	800
	21st to end	Night	25% 11% 30% 27% 7%	800
December	1st to 10th	Night	24% 11% 37% 23% 5%	800
	11th to 20th	Night	26% 8% 35% 25% 5% 1	900
	21st to end	Night	30% 14% 31% 21% 4	1100

Page generated at 2025-02-03 03:05:52. Version ac07

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