Mookie Mountain Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mookie Mountain Observatory clear sky chart from 2005-11-06 to 2024-11-25.

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	11% 8% 3 8% 5% 5% 5% 4 6% 8% 37%	101169
	Night	11% 8% 3 7% 5% 5% 5% 4 6% 8% 40%	98280
Transparency	Day	43% 5% 11% 20% 17% 4	104976
	Night	41% 5% 11% 21% 18% 5%	102611
Seeing	Day	17% 12% 21% 21% 18% 11%	14917
	Night	16% 10% 20% 29% 21% 4	24952

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	13% 10% 5% 8% 5% 5% 4 3 6% 6% 34%	2836
	11th to 20th	Day	13% 9% 7% 11% 4 4 3 3 4 5% 38%	2840
	21st to end	Day	15% 17% 5% 6% 3 3 3 3 4 5% 35%	3184
February	1st to 10th	Day	14% 11% 4 8% 5% 4 5% 4 5% 5% 36%	1900
	11th to 20th	Day	16% 11% 4 8% 4 4 4 3 5% 6% 34%	1848
	21st to end	Day	16% 10% 4 8% 5% 6% 3 3 4 5% 36%	1570
March	1st to 10th	Day	19% 11% 4 7% 4 3 4 3 4 7% 34%	3211
	11th to 20th	Day	11% 8% 2 6% 4 4 4 3 4 5% 49%	3480
	21st to end	Day	14% 10% 3 8% 5% 4 4 3 5% 6% 38%	3815
April	1st to 10th	Day	9% 7% 2 7% 5% 5% 5% 5% 6% 7% 42%	2154
	11th to 20th	Day	11% 8% 3 7% 5% 3 4 4 5% 6% 43%	2254
	21st to end	Day	10% 7% 2 7% 4 5% 5% 4 6% 7% 43%	2456
May	1st to 10th	Day	10% 7% 3 8% 6% 6% 6% 5% 6% 8% 35%	4082
	11th to 20th	Day	14% 9% 4 9% 6% 5% 5% 4 6% 7% 30%	4081
	21st to end	Day	7% 5% 2 7% 6% 6% 6% 5% 7% 10% 38%	4476
June	1st to 10th	Day	8% 7% 2 9% 6% 6% 7% 6% 7% 9% 32%	2470
	11th to 20th	Day	5% 5% 2 7% 5% 7% 6% 6% 9% 10% 37%	2470
	21st to end	Day	7% 5% 3 7% 6% 7% 7% 5% 9% 10% 35%	2470
July	1st to 10th	Day	6% 5% 3 9% 7% 7% 8% 7% 9% 11% 28%	4120
	11th to 20th	Day	8% 6% 2 8% 7% 7% 8% 6% 8% 9% 31%	4120
	21st to end	Day	11% 10% 4 12% 9% 9% 8% 6% 8% 7% 16%	4466
August	1st to 10th	Day	6% 4 2 8% 6% 6% 7% 6% 8% 12% 34%	4104
	11th to 20th	Day	7% 6% 2 8% 5% 5% 6% 5% 8% 11% 39%	3862
	21st to end	Day	8% 5% 2 7% 5% 6% 6% 4 6% 7% 43%	4180
September	1st to 10th	Day	10% 7% 3 8% 7% 5% 6% 5% 6% 8% 36%	2104
	11th to 20th	Day	13% 7% 2 8% 5% 5% 5% 5% 6% 9% 34%	2090
	21st to end	Day	13% 5% 1 6% 5% 5% 5% 4 6% 8% 42%	2090
October	1st to 10th	Day	9% 4 2 6% 4 5% 4 4 5% 5% 52%	2090
	11th to 20th	Day	10% 6% 2 5% 3 3 4 4 5% 6% 53%	1968
	21st to end	Day	10% 7% 2 5% 3 3 4 3 5% 5% 53%	2083
November	1st to 10th	Day	10% 6% 2 5% 3 4 4 3 5% 6% 54%	1762
	11th to 20th	Day	10% 7% 2 5% 4 4 4 4 5% 7% 48%	1800
	21st to end	Day	12% 8% 3 5% 4 4 4 4 4 7% 44%	1746
December	1st to 10th	Day	16% 10% 4 9% 5% 4 5% 4 4 6% 34%	1710
	11th to 20th	Day	12% 10% 4 8% 5% 4 5% 4 5% 6% 38%	2153
	21st to end	Day	13% 12% 6% 7% 5% 4 4 4 6% 8% 31%	3124
January	1st to 10th	Night	14% 10% 4 9% 5% 5% 5% 4 5% 7% 33%	4109
	11th to 20th	Night	10% 11% 4 10% 6% 4 4 4 4 6% 36%	4120
	21st to end	Night	15% 16% 4 9% 5% 4 4 3 3 4 33%	4468
February	1st to 10th	Night	12% 11% 3 7% 4 4 4 3 5% 7% 39%	2280
	11th to 20th	Night	17% 11% 4 9% 5% 3 4 3 4 5% 36%	2218
	21st to end	Night	16% 10% 3 8% 5% 5% 5% 4 5% 5% 34%	1884
March	1st to 10th	Night	18% 13% 4 8% 5% 5% 4 3 5% 5% 30%	3642
	11th to 20th	Night	11% 7% 2 4 3 3 4 4 6% 8% 48%	3480
	21st to end	Night	13% 8% 3 8% 5% 4 4 3 5% 6% 40%	3817
April	1st to 10th	Night	10% 6% 2 5% 5% 4 5% 4 6% 8% 46%	2041
	11th to 20th	Night	10% 7% 2 6% 5% 4 4 3 5% 7% 48%	1875
	21st to end	Night	9% 7% 2 5% 5% 3 4 3 5% 8% 48%	1723
May	1st to 10th	Night	9% 7% 3 7% 6% 5% 5% 5% 7% 10% 37%	2813
	11th to 20th	Night	10% 10% 4 9% 6% 5% 5% 4 5% 8% 34%	2812
	21st to end	Night	5% 5% 2 7% 4 5% 5% 6% 8% 12% 41%	3079
June	1st to 10th	Night	6% 5% 2 7% 7% 5% 6% 5% 8% 12% 36%	1710
	11th to 20th	Night	3 2 2 5% 5% 5% 6% 5% 9% 13% 45%	1710
	21st to end	Night	4 5% 2 5% 5% 6% 5% 5% 9% 10% 45%	1710
July	1st to 10th	Night	8% 6% 3 8% 5% 6% 6% 5% 9% 11% 33%	2840
	11th to 20th	Night	7% 5% 3 5% 5% 5% 5% 4 8% 11% 42%	2840
	21st to end	Night	12% 9% 4 9% 7% 7% 7% 5% 8% 10% 23%	3087
August	1st to 10th	Night	6% 5% 3 6% 5% 6% 5% 5% 7% 12% 41%	2825
	11th to 20th	Night	10% 7% 2 5% 4 5% 5% 3 6% 8% 44%	2963
	21st to end	Night	6% 6% 2 5% 4 4 5% 5% 6% 9% 48%	3476
September	1st to 10th	Night	7% 7% 3 7% 5% 6% 6% 4 6% 8% 40%	2057
	11th to 20th	Night	10% 6% 3 7% 5% 5% 5% 4 7% 8% 40%	2090
	21st to end	Night	8% 6% 2 6% 4 4 5% 4 7% 7% 47%	2090
October	1st to 10th	Night	10% 5% 2 4 3 3 4 3 5% 6% 56%	2090
	11th to 20th	Night	11% 5% 2 5% 4 4 4 3 5% 6% 52%	2210
	21st to end	Night	10% 6% 2 5% 4 3 3 4 4 4 55%	2512
November	1st to 10th	Night	11% 7% 2 5% 3 4 3 3 5% 6% 51%	2536
	11th to 20th	Night	11% 8% 2 5% 5% 4 3 3 4 6% 49%	2600
	21st to end	Night	12% 9% 2 6% 5% 4 3 4 6% 6% 43%	2529
December	1st to 10th	Night	16% 9% 4 8% 6% 5% 4 4 6% 7% 32%	2470
	11th to 20th	Night	12% 13% 4 7% 4 3 3 3 4 6% 41%	3042
	21st to end	Night	13% 12% 4 8% 6% 5% 5% 4 6% 8% 29%	4532

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	49% 4 4 16% 24% 3	2837
	11th to 20th	Day	49% 2 6% 15% 24% 4	2840
	21st to end	Day	52% 3 5% 17% 20% 3	3184
February	1st to 10th	Day	50% 3 6% 18% 19% 4	1900
	11th to 20th	Day	51% 3 6% 17% 18% 5%	1858
	21st to end	Day	52% 2 7% 14% 20% 6%	1570
March	1st to 10th	Day	51% 4 7% 15% 16% 8%	3211
	11th to 20th	Day	38% 4 7% 20% 22% 9%	3480
	21st to end	Day	47% 4 7% 23% 16% 3	3815
April	1st to 10th	Day	41% 4 10% 22% 19% 4	2154
	11th to 20th	Day	42% 3 8% 19% 24% 5%	2254
	21st to end	Day	40% 4 11% 28% 15% 3	2456
May	1st to 10th	Day	46% 4 14% 21% 14% 2	4120
	11th to 20th	Day	53% 5% 10% 23% 9% 1	4085
	21st to end	Day	39% 5% 14% 24% 16% 1	4489
June	1st to 10th	Day	45% 8% 16% 21% 8% 1	2470
	11th to 20th	Day	38% 8% 17% 23% 12% 1	2470
	21st to end	Day	41% 8% 17% 19% 12% 2	2470
July	1st to 10th	Day	42% 12% 20% 19% 6% 1	4055
	11th to 20th	Day	44% 9% 21% 18% 6% 1	4051
	21st to end	Day	63% 9% 12% 11% 4	4324
August	1st to 10th	Day	38% 9% 17% 28% 7%	4091
	11th to 20th	Day	34% 9% 20% 22% 13% 1	3901
	21st to end	Day	37% 8% 11% 29% 14% 2	4179
September	1st to 10th	Day	43% 7% 12% 17% 17% 4	2104
	11th to 20th	Day	44% 6% 12% 19% 17% 1	2090
	21st to end	Day	39% 5% 12% 17% 20% 6%	2090
October	1st to 10th	Day	27% 5% 6% 16% 34% 12%	3480
	11th to 20th	Day	21% 3 6% 20% 28% 21%	3247
	21st to end	Day	27% 4 5% 26% 26% 12%	3409
November	1st to 10th	Day	32% 3 8% 16% 32% 9%	1762
	11th to 20th	Day	35% 4 6% 20% 26% 9%	1800
	21st to end	Day	41% 3 7% 19% 26% 5%	1746
December	1st to 10th	Day	52% 4 6% 18% 17% 4	1710
	11th to 20th	Day	47% 3 7% 14% 23% 5%	2150
	21st to end	Day	51% 3 7% 21% 16% 3	3124
January	1st to 10th	Night	50% 4 4 16% 22% 3	4109
	11th to 20th	Night	48% 4 6% 15% 17% 9%	4120
	21st to end	Night	55% 3 5% 12% 21% 4	4468
February	1st to 10th	Night	45% 3 9% 18% 21% 4	2280
	11th to 20th	Night	52% 4 5% 17% 17% 5%	2219
	21st to end	Night	51% 4 7% 16% 17% 5%	1884
March	1st to 10th	Night	56% 3 8% 13% 14% 5%	3642
	11th to 20th	Night	35% 3 9% 22% 22% 9%	3480
	21st to end	Night	47% 3 8% 23% 17% 4	3817
April	1st to 10th	Night	36% 4 12% 22% 23% 4	2041
	11th to 20th	Night	37% 3 9% 23% 21% 7%	1875
	21st to end	Night	36% 4 12% 30% 17% 2	1723
May	1st to 10th	Night	41% 5% 19% 23% 12% 1	2840
	11th to 20th	Night	48% 5% 14% 23% 10%	2813
	21st to end	Night	33% 7% 18% 29% 13% 1	3087
June	1st to 10th	Night	38% 9% 19% 23% 9% 1	1710
	11th to 20th	Night	26% 9% 26% 27% 10% 1	1710
	21st to end	Night	32% 9% 21% 21% 14% 3	1710
July	1st to 10th	Night	41% 11% 22% 20% 5%	2795
	11th to 20th	Night	34% 11% 25% 22% 5% 2	2786
	21st to end	Night	55% 12% 15% 13% 5% 1	2988
August	1st to 10th	Night	33% 10% 22% 29% 6%	2814
	11th to 20th	Night	35% 8% 21% 23% 12% 1	2990
	21st to end	Night	30% 7% 17% 30% 15% 1	3476
September	1st to 10th	Night	39% 8% 15% 19% 15% 4	2057
	11th to 20th	Night	40% 8% 13% 20% 18%	2090
	21st to end	Night	35% 5% 12% 22% 21% 6%	2090
October	1st to 10th	Night	25% 5% 9% 19% 31% 10%	3480
	11th to 20th	Night	22% 3 6% 20% 33% 17%	3670
	21st to end	Night	24% 4 4 28% 27% 12%	4136
November	1st to 10th	Night	34% 4 8% 21% 24% 9%	2536
	11th to 20th	Night	38% 3 5% 20% 25% 9%	2600
	21st to end	Night	41% 4 6% 22% 22% 5%	2529
December	1st to 10th	Night	51% 4 8% 17% 15% 4	2470
	11th to 20th	Night	46% 4 7% 14% 26% 4	3044
	21st to end	Night	53% 3 7% 20% 15% 2	4532

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	27% 25% 34% 11% 4	270
	11th to 20th	Day	29% 24% 28% 14% 6%	270
	21st to end	Day	23% 32% 28% 13% 5% 1	297
February	1st to 10th	Day	27% 21% 33% 15% 3	270
	11th to 20th	Day	37% 26% 27% 8% 2	270
	21st to end	Day	37% 27% 25% 9% 2	225
March	1st to 10th	Day	29% 18% 29% 17% 7% 1	322
	11th to 20th	Day	25% 19% 26% 20% 8% 1	460
	21st to end	Day	24% 22% 26% 19% 8% 1	506
April	1st to 10th	Day	23% 17% 26% 21% 11% 2	460
	11th to 20th	Day	18% 19% 27% 20% 15% 2	452
	21st to end	Day	19% 14% 25% 25% 13% 5%	460
May	1st to 10th	Day	15% 16% 28% 21% 13% 6%	463
	11th to 20th	Day	16% 9% 22% 25% 17% 11%	487
	21st to end	Day	11% 5% 21% 28% 20% 15%	529
June	1st to 10th	Day	10% 4 21% 27% 23% 15%	490
	11th to 20th	Day	9% 3 17% 24% 27% 20%	490
	21st to end	Day	11% 4 19% 26% 22% 18%	490
July	1st to 10th	Day	11% 3 10% 23% 26% 27%	485
	11th to 20th	Day	10% 2 8% 26% 28% 26%	484
	21st to end	Day	10% 5% 8% 23% 27% 28%	532
August	1st to 10th	Day	14% 4 14% 22% 21% 26%	486
	11th to 20th	Day	13% 4 12% 21% 26% 24%	479
	21st to end	Day	14% 3 9% 16% 29% 28%	539
September	1st to 10th	Day	9% 2 13% 23% 32% 20%	490
	11th to 20th	Day	15% 6% 13% 19% 29% 18%	490
	21st to end	Day	16% 5% 14% 25% 29% 11%	490
October	1st to 10th	Day	14% 6% 18% 28% 25% 10%	490
	11th to 20th	Day	14% 13% 23% 24% 20% 6%	490
	21st to end	Day	16% 12% 21% 27% 20% 4	532
November	1st to 10th	Day	18% 13% 32% 22% 12% 4	300
	11th to 20th	Day	21% 17% 31% 20% 10% 1	300
	21st to end	Day	17% 18% 36% 19% 8% 3	282
December	1st to 10th	Day	28% 24% 23% 20% 4 1	270
	11th to 20th	Day	26% 16% 29% 19% 9% 1	270
	21st to end	Day	27% 23% 28% 14% 7% 1	297
January	1st to 10th	Night	24% 18% 31% 22% 6%	760
	11th to 20th	Night	23% 18% 29% 24% 7%	760
	21st to end	Night	19% 20% 31% 27% 2	836
February	1st to 10th	Night	22% 16% 28% 29% 6%	760
	11th to 20th	Night	27% 19% 30% 22% 2	743
	21st to end	Night	25% 23% 30% 20% 3	628
March	1st to 10th	Night	20% 16% 32% 26% 5%	760
	11th to 20th	Night	19% 18% 27% 26% 8% 1	760
	21st to end	Night	20% 13% 28% 29% 9%	836
April	1st to 10th	Night	16% 14% 28% 31% 10% 1	711
	11th to 20th	Night	15% 13% 26% 31% 14% 1	563
	21st to end	Night	12% 9% 24% 36% 18% 1	570
May	1st to 10th	Night	12% 8% 24% 34% 20% 2	570
	11th to 20th	Night	12% 6% 19% 33% 24% 6%	561
	21st to end	Night	10% 2 12% 34% 33% 8%	617
June	1st to 10th	Night	8% 3 12% 36% 37% 5%	570
	11th to 20th	Night	4 3 11% 32% 38% 13%	570
	21st to end	Night	6% 2 8% 31% 44% 9%	570
July	1st to 10th	Night	10% 2 5% 25% 47% 12%	555
	11th to 20th	Night	9% 2 6% 18% 49% 16%	552
	21st to end	Night	7% 2 5% 22% 49% 14%	624
August	1st to 10th	Night	9% 2 5% 25% 44% 15%	567
	11th to 20th	Night	9% 3 7% 25% 48% 8%	564
	21st to end	Night	13% 2 5% 24% 45% 11%	627
September	1st to 10th	Night	11% 3 8% 27% 42% 9%	727
	11th to 20th	Night	13% 3 13% 28% 38% 5%	760
	21st to end	Night	11% 4 12% 36% 33% 4	760
October	1st to 10th	Night	12% 6% 18% 30% 28% 6%	760
	11th to 20th	Night	14% 8% 21% 33% 22% 2	760
	21st to end	Night	14% 9% 19% 36% 19% 2	836
November	1st to 10th	Night	15% 8% 20% 35% 19% 3	780
	11th to 20th	Night	17% 13% 24% 32% 13% 2	800
	21st to end	Night	18% 15% 22% 30% 14% 1	779
December	1st to 10th	Night	24% 16% 23% 28% 9% 1	760
	11th to 20th	Night	21% 14% 26% 29% 9% 1	760
	21st to end	Night	25% 15% 25% 29% 6%	836

Page generated at 2024-11-22 08:02:25. Version ac07

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