Intrusted Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Intrusted Observatory clear sky chart from 2005-11-06 to 2024-06-30.

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	10% 6% 2 6% 4 4 4 3 5% 7% 49%	89697
	Night	9% 6% 2 5% 4 3 4 3 5% 7% 52%	89485
Transparency	Day	35% 5% 11% 26% 19% 4	89472
	Night	33% 4 11% 26% 21% 5%	89315
Seeing	Day	12% 9% 29% 29% 16% 3	15070
	Night	12% 9% 34% 33% 11% 1	25005

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	10% 7% 3 10% 5% 5% 4 3 4 7% 41%	2847
	11th to 20th	Day	9% 8% 4 7% 6% 6% 6% 3 5% 5% 41%	2850
	21st to end	Day	11% 13% 5% 8% 4 3 2 2 3 6% 43%	3135
February	1st to 10th	Day	11% 11% 3 6% 3 3 3 3 5% 6% 44%	1710
	11th to 20th	Day	9% 7% 3 7% 5% 4 3 3 6% 6% 48%	1817
	21st to end	Day	9% 7% 2 5% 4 4 4 5% 5% 7% 48%	1570
March	1st to 10th	Day	10% 7% 2 5% 3 3 3 2 4 5% 56%	3393
	11th to 20th	Day	9% 5% 2 4 3 3 2 2 5% 7% 59%	3480
	21st to end	Day	12% 8% 4 7% 5% 4 4 3 6% 6% 42%	3814
April	1st to 10th	Day	10% 6% 2 5% 4 3 4 3 5% 7% 50%	2090
	11th to 20th	Day	14% 7% 2 5% 5% 4 4 4 5% 6% 45%	2321
	21st to end	Day	17% 7% 3 6% 4 5% 4 3 5% 5% 43%	2470
May	1st to 10th	Day	17% 10% 3 7% 5% 4 4 3 4 5% 39%	4082
	11th to 20th	Day	11% 5% 2 6% 4 4 3 4 5% 7% 48%	4082
	21st to end	Day	11% 6% 3 6% 5% 4 5% 4 5% 8% 43%	4477
June	1st to 10th	Day	5% 4 2 4 3 5% 4 4 7% 10% 51%	2470
	11th to 20th	Day	7% 4 1 5% 5% 4 5% 4 5% 9% 53%	2470
	21st to end	Day	6% 3 1 3 4 4 4 4 7% 9% 56%	2458
July	1st to 10th	Day	8% 5% 2 5% 4 4 5% 5% 7% 9% 47%	2340
	11th to 20th	Day	4 2 1 3 4 4 5% 5% 7% 9% 57%	2340
	21st to end	Day	7% 4 2 5% 5% 5% 5% 5% 7% 9% 45%	2546
August	1st to 10th	Day	5% 4 2 6% 4 4 6% 5% 7% 10% 46%	2328
	11th to 20th	Day	7% 4 2 5% 5% 4 5% 3 5% 8% 53%	2301
	21st to end	Day	4 3 2 5% 3 3 4 3 6% 8% 58%	2517
September	1st to 10th	Day	11% 6% 2 5% 4 3 4 2 4 6% 54%	1980
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 4 7% 52%	1980
	21st to end	Day	9% 4 2 5% 3 4 3 3 5% 6% 57%	1980
October	1st to 10th	Day	11% 5% 2 5% 3 4 4 3 6% 6% 53%	1896
	11th to 20th	Day	10% 4 1 4 2 2 3 2 4 6% 61%	1800
	21st to end	Day	13% 7% 2 4 3 3 4 2 4 5% 54%	1980
November	1st to 10th	Day	7% 5% 2 4 3 3 3 2 5% 7% 61%	1747
	11th to 20th	Day	8% 4 2 5% 4 2 3 3 4 6% 59%	1710
	21st to end	Day	14% 5% 2 4 3 3 1 2 3 6% 56%	1710
December	1st to 10th	Day	9% 6% 2 5% 3 3 3 3 5% 7% 52%	1710
	11th to 20th	Day	10% 7% 2 7% 5% 4 4 3 4 6% 48%	2161
	21st to end	Day	12% 12% 5% 13% 5% 5% 4 3 5% 7% 31%	3135
January	1st to 10th	Night	9% 8% 3 11% 4 5% 3 2 4 5% 46%	4108
	11th to 20th	Night	6% 6% 2 6% 6% 5% 5% 4 5% 6% 48%	4120
	21st to end	Night	14% 12% 4 5% 3 2 3 2 3 4 47%	4532
February	1st to 10th	Night	10% 9% 3 7% 4 3 4 3 5% 6% 45%	2470
	11th to 20th	Night	11% 8% 3 5% 3 4 3 3 4 6% 49%	2266
	21st to end	Night	10% 7% 2 5% 4 3 4 3 3 6% 54%	1884
March	1st to 10th	Night	9% 7% 2 4 3 3 3 3 5% 6% 56%	3463
	11th to 20th	Night	8% 5% 2 5% 3 3 4 3 5% 6% 56%	3480
	21st to end	Night	13% 8% 3 4 4 4 4 3 5% 5% 47%	3817
April	1st to 10th	Night	11% 5% 1 6% 3 3 3 3 6% 8% 53%	2090
	11th to 20th	Night	12% 6% 2 5% 4 3 3 3 5% 7% 49%	1804
	21st to end	Night	13% 7% 2 6% 4 4 4 3 4 6% 48%	1710
May	1st to 10th	Night	14% 9% 2 5% 4 4 4 4 5% 6% 43%	2823
	11th to 20th	Night	12% 6% 2 5% 4 3 4 3 5% 8% 48%	2823
	21st to end	Night	9% 5% 2 4 3 2 4 3 5% 8% 54%	3090
June	1st to 10th	Night	4 3 2 4 4 4 4 4 7% 10% 54%	1710
	11th to 20th	Night	4 3 2 4 4 4 5% 4 8% 11% 53%	1710
	21st to end	Night	5% 3 2 4 3 3 4 4 5% 7% 60%	1701
July	1st to 10th	Night	7% 4 1 4 3 3 4 4 7% 9% 54%	1620
	11th to 20th	Night	3 3 1 4 3 3 4 4 7% 9% 58%	1620
	21st to end	Night	5% 3 2 5% 5% 4 5% 4 7% 11% 49%	1772
August	1st to 10th	Night	4 3 1 5% 3 4 5% 4 7% 10% 52%	1611
	11th to 20th	Night	6% 4 1 5% 3 4 4 3 5% 8% 55%	1600
	21st to end	Night	4 3 1 4 4 3 4 4 5% 7% 62%	1835
September	1st to 10th	Night	9% 4 2 4 2 3 3 3 3 6% 61%	1980
	11th to 20th	Night	9% 5% 1 5% 3 4 3 3 5% 8% 53%	1980
	21st to end	Night	6% 4 2 4 3 3 3 3 5% 6% 61%	1980
October	1st to 10th	Night	11% 5% 2 5% 4 3 2 3 5% 6% 55%	2044
	11th to 20th	Night	10% 4 1 3 2 2 3 2 4 6% 62%	2160
	21st to end	Night	12% 5% 2 5% 2 2 2 2 3 5% 59%	2376
November	1st to 10th	Night	8% 4 2 4 2 3 2 3 4 5% 64%	2328
	11th to 20th	Night	8% 6% 2 4 2 3 3 4 5% 6% 58%	2470
	21st to end	Night	13% 7% 2 3 2 2 3 3 4 6% 56%	2470
December	1st to 10th	Night	9% 7% 2 4 4 3 3 4 5% 7% 53%	2470
	11th to 20th	Night	9% 7% 2 5% 4 4 4 3 5% 6% 51%	3036
	21st to end	Night	15% 9% 4 8% 4 4 4 3 5% 5% 38%	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	43% 5% 9% 24% 18% 1	2848
	11th to 20th	Day	44% 6% 11% 24% 11% 5%	2850
	21st to end	Day	46% 2 10% 22% 18% 1	3135
February	1st to 10th	Day	41% 4 12% 26% 13% 4	1710
	11th to 20th	Day	37% 4 11% 28% 15% 4	1827
	21st to end	Day	35% 3 9% 25% 21% 7%	1570
March	1st to 10th	Day	32% 3 6% 23% 28% 9%	3393
	11th to 20th	Day	26% 4 12% 27% 27% 3	3480
	21st to end	Day	42% 6% 11% 28% 10% 2	3814
April	1st to 10th	Day	34% 4 11% 26% 20% 5%	2090
	11th to 20th	Day	40% 4 10% 25% 17% 4	2321
	21st to end	Day	43% 4 10% 29% 13% 1	2470
May	1st to 10th	Day	48% 5% 8% 20% 15% 3	4120
	11th to 20th	Day	35% 8% 10% 27% 19%	4086
	21st to end	Day	38% 7% 11% 23% 17% 4	4489
June	1st to 10th	Day	27% 6% 17% 30% 16% 3	2470
	11th to 20th	Day	28% 5% 13% 28% 21% 4	2470
	21st to end	Day	23% 6% 14% 28% 23% 6%	2458
July	1st to 10th	Day	31% 7% 14% 28% 17% 3	2276
	11th to 20th	Day	22% 6% 15% 29% 22% 6%	2271
	21st to end	Day	32% 6% 13% 31% 17% 1	2405
August	1st to 10th	Day	31% 7% 15% 29% 14% 3	2314
	11th to 20th	Day	30% 6% 12% 32% 18% 4	2301
	21st to end	Day	24% 4 15% 28% 20% 9%	2517
September	1st to 10th	Day	32% 4 11% 25% 21% 7%	1980
	11th to 20th	Day	32% 4 9% 28% 23% 3	1980
	21st to end	Day	28% 4 9% 26% 27% 6%	1980
October	1st to 10th	Day	31% 5% 11% 24% 26% 3	1896
	11th to 20th	Day	26% 4 8% 26% 29% 8%	1800
	21st to end	Day	34% 3 9% 26% 20% 8%	1980
November	1st to 10th	Day	25% 3 10% 30% 25% 7%	1747
	11th to 20th	Day	29% 3 9% 27% 28% 5%	1710
	21st to end	Day	32% 2 8% 28% 25% 4	1710
December	1st to 10th	Day	33% 3 11% 32% 18% 2	1710
	11th to 20th	Day	38% 4 8% 28% 19% 3	2159
	21st to end	Day	53% 4 8% 22% 10% 2	3135
January	1st to 10th	Night	42% 3 7% 29% 16% 3	4108
	11th to 20th	Night	35% 6% 12% 26% 18% 2	4120
	21st to end	Night	42% 3 10% 23% 19% 2	4532
February	1st to 10th	Night	41% 3 12% 23% 16% 5%	2470
	11th to 20th	Night	37% 4 11% 26% 18% 4	2266
	21st to end	Night	34% 3 8% 22% 23% 9%	1884
March	1st to 10th	Night	30% 3 7% 25% 26% 8%	3463
	11th to 20th	Night	28% 4 10% 23% 31% 3	3480
	21st to end	Night	38% 6% 13% 28% 12% 2	3817
April	1st to 10th	Night	31% 3 12% 23% 24% 7%	2090
	11th to 20th	Night	34% 4 12% 24% 21% 4	1804
	21st to end	Night	37% 5% 12% 23% 18% 4	1710
May	1st to 10th	Night	41% 6% 12% 20% 16% 5%	2850
	11th to 20th	Night	35% 6% 15% 29% 15%	2824
	21st to end	Night	28% 6% 16% 28% 20% 1	3099
June	1st to 10th	Night	25% 7% 21% 29% 16% 3	1710
	11th to 20th	Night	25% 6% 15% 30% 21% 3	1710
	21st to end	Night	23% 5% 13% 31% 21% 7%	1701
July	1st to 10th	Night	26% 5% 15% 30% 20% 4	1575
	11th to 20th	Night	21% 5% 12% 32% 24% 6%	1566
	21st to end	Night	27% 7% 15% 30% 19% 1	1673
August	1st to 10th	Night	25% 7% 15% 33% 16% 4	1601
	11th to 20th	Night	27% 5% 12% 30% 23% 3	1600
	21st to end	Night	23% 5% 12% 27% 26% 8%	1835
September	1st to 10th	Night	26% 4 11% 26% 23% 10%	1980
	11th to 20th	Night	31% 5% 11% 22% 27% 5%	1980
	21st to end	Night	24% 4 9% 26% 30% 7%	1980
October	1st to 10th	Night	30% 3 9% 23% 26% 9%	2044
	11th to 20th	Night	26% 3 6% 27% 28% 9%	2160
	21st to end	Night	31% 2 7% 23% 28% 9%	2376
November	1st to 10th	Night	25% 3 9% 29% 26% 9%	2328
	11th to 20th	Night	28% 3 8% 28% 28% 5%	2470
	21st to end	Night	32% 2 9% 25% 24% 7%	2470
December	1st to 10th	Night	31% 4 12% 29% 21% 3	2470
	11th to 20th	Night	35% 4 7% 29% 22% 4	3037
	21st to end	Night	47% 6% 8% 24% 12% 4	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	19% 14% 35% 24% 8%	270
	11th to 20th	Day	17% 19% 43% 19% 3	270
	21st to end	Day	12% 11% 51% 23% 3 1	297
February	1st to 10th	Day	17% 20% 42% 17% 3 1	270
	11th to 20th	Day	15% 17% 44% 21% 3	270
	21st to end	Day	14% 24% 43% 14% 5%	225
March	1st to 10th	Day	15% 17% 40% 24% 4	270
	11th to 20th	Day	19% 18% 38% 21% 5%	270
	21st to end	Day	21% 23% 37% 16% 2 1	297
April	1st to 10th	Day	16% 19% 44% 17% 5%	270
	11th to 20th	Day	17% 17% 41% 20% 4	519
	21st to end	Day	21% 16% 36% 17% 8% 1	650
May	1st to 10th	Day	16% 13% 37% 24% 9% 1	653
	11th to 20th	Day	17% 10% 28% 29% 12% 4	675
	21st to end	Day	16% 9% 30% 26% 15% 3	734
June	1st to 10th	Day	5% 5% 25% 37% 25% 5%	680
	11th to 20th	Day	7% 4 30% 39% 17% 3	680
	21st to end	Day	6% 4 31% 42% 16% 2	676
July	1st to 10th	Day	8% 2 13% 36% 31% 10%	621
	11th to 20th	Day	4 2 15% 41% 31% 7%	618
	21st to end	Day	8% 1 11% 39% 33% 8%	684
August	1st to 10th	Day	7% 3 18% 39% 29% 4	626
	11th to 20th	Day	7% 2 15% 38% 32% 5%	615
	21st to end	Day	5% 2 15% 33% 36% 9%	636
September	1st to 10th	Day	11% 1 12% 39% 31% 5%	270
	11th to 20th	Day	5% 4 20% 37% 30% 4	270
	21st to end	Day	13% 4 26% 34% 18% 6%	270
October	1st to 10th	Day	12% 7% 31% 26% 16% 7%	270
	11th to 20th	Day	9% 11% 46% 24% 9% 1	270
	21st to end	Day	22% 12% 36% 21% 7% 2	297
November	1st to 10th	Day	10% 10% 37% 30% 10% 2	270
	11th to 20th	Day	13% 21% 34% 20% 10% 1	270
	21st to end	Day	19% 13% 34% 27% 6% 1	270
December	1st to 10th	Day	10% 13% 40% 26% 9% 3	270
	11th to 20th	Day	13% 15% 35% 28% 9%	270
	21st to end	Day	18% 21% 40% 20% 2	297
January	1st to 10th	Night	10% 11% 41% 31% 6%	950
	11th to 20th	Night	13% 13% 39% 28% 6%	950
	21st to end	Night	12% 12% 39% 32% 4	1045
February	1st to 10th	Night	16% 13% 41% 26% 4	950
	11th to 20th	Night	16% 15% 39% 27% 3	792
	21st to end	Night	14% 14% 41% 27% 3	628
March	1st to 10th	Night	13% 13% 40% 30% 4	603
	11th to 20th	Night	19% 13% 39% 25% 5%	570
	21st to end	Night	20% 16% 37% 23% 4	627
April	1st to 10th	Night	14% 14% 42% 22% 7%	570
	11th to 20th	Night	16% 15% 40% 24% 5%	563
	21st to end	Night	15% 16% 37% 26% 5% 1	570
May	1st to 10th	Night	16% 11% 36% 31% 5%	570
	11th to 20th	Night	13% 8% 30% 37% 11% 1	561
	21st to end	Night	11% 8% 31% 35% 13% 2	617
June	1st to 10th	Night	5% 3 28% 41% 22% 1	570
	11th to 20th	Night	4 3 37% 42% 15%	570
	21st to end	Night	6% 4 36% 41% 12% 1	567
July	1st to 10th	Night	7% 2 17% 46% 27% 2	525
	11th to 20th	Night	3 1 18% 52% 22% 3	522
	21st to end	Night	6% 1 16% 47% 28% 2	591
August	1st to 10th	Night	4 1 18% 50% 25% 1	537
	11th to 20th	Night	8% 2 16% 48% 25% 2	534
	21st to end	Night	5% 1 16% 42% 33% 2	594
September	1st to 10th	Night	10% 3 24% 42% 19% 1	540
	11th to 20th	Night	10% 3 26% 40% 19% 2	540
	21st to end	Night	8% 5% 28% 41% 17% 2	540
October	1st to 10th	Night	14% 5% 28% 32% 19% 2	604
	11th to 20th	Night	13% 8% 41% 31% 7%	720
	21st to end	Night	14% 12% 34% 30% 9% 1	792
November	1st to 10th	Night	9% 8% 40% 32% 10%	848
	11th to 20th	Night	10% 14% 39% 29% 7%	950
	21st to end	Night	16% 12% 33% 32% 6%	950
December	1st to 10th	Night	13% 10% 37% 32% 7% 1	950
	11th to 20th	Night	14% 11% 40% 31% 4	950
	21st to end	Night	14% 16% 37% 30% 4	1045

Page generated at 2024-06-26 21:18:39. Version ac07

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