Joseph
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Joseph clear sky chart from 2005-11-06 to 2024-11-05.

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	4 7% 3 7% 5% 5% 5% 4 6% 7% 45%	105251
	Night	3 6% 3 7% 5% 5% 5% 5% 7% 8% 46%	102458
Transparency	Day	35% 8% 13% 20% 16% 8%	104995
	Night	34% 10% 14% 21% 15% 6%	102303
Seeing	Day	9% 12% 29% 30% 16% 5%	14372
	Night	7% 7% 26% 37% 19% 3	23549

By Month

Percentage Cloud Cover SW (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	1 9% 6% 13% 8% 7% 8% 6% 9% 9% 24%	2539
	11th to 20th	Day	2 8% 4 13% 10% 9% 7% 6% 7% 7% 28%	2540
	21st to end	Day	1 9% 4 11% 8% 8% 8% 6% 8% 9% 27%	2794
February	1st to 10th	Day	2 12% 6% 9% 7% 6% 6% 5% 8% 8% 30%	1579
	11th to 20th	Day	1 14% 6% 12% 7% 7% 7% 5% 7% 8% 26%	1841
	21st to end	Day	2 8% 5% 14% 9% 9% 7% 7% 8% 8% 24%	1570
March	1st to 10th	Day	2 7% 4 12% 8% 7% 8% 6% 10% 9% 29%	3138
	11th to 20th	Day	1 10% 4 8% 5% 5% 6% 5% 5% 6% 45%	3289
	21st to end	Day	3 15% 5% 16% 10% 8% 8% 6% 7% 7% 14%	4117
April	1st to 10th	Day	6% 15% 5% 11% 8% 6% 6% 6% 7% 7% 24%	2280
	11th to 20th	Day	6% 13% 4 9% 6% 6% 5% 5% 6% 7% 33%	2277
	21st to end	Day	10% 15% 4 9% 6% 4 4 4 7% 7% 30%	2470
May	1st to 10th	Day	6% 11% 4 9% 6% 6% 5% 5% 6% 7% 35%	4169
	11th to 20th	Day	7% 6% 2 5% 4 4 5% 4 5% 8% 51%	4377
	21st to end	Day	11% 11% 3 9% 6% 6% 5% 4 6% 8% 31%	4813
June	1st to 10th	Day	11% 10% 3 8% 6% 6% 5% 5% 7% 9% 31%	2660
	11th to 20th	Day	11% 9% 3 7% 6% 5% 5% 3 6% 7% 39%	2660
	21st to end	Day	5% 3 1 4 3 3 5% 4 6% 8% 58%	2660
July	1st to 10th	Day	1 1 1 2 2 2 3 3 5% 5% 75%	4420
	11th to 20th	Day	1 1 1 2 2 2 4 3 4 5% 76%	4420
	21st to end	Day	1 1 2 2 2 4 4 5% 6% 74%	4790
August	1st to 10th	Day	3 2 1 4 3 3 5% 4 6% 8% 61%	4400
	11th to 20th	Day	3 2 1 3 2 3 4 4 5% 8% 66%	4020
	21st to end	Day	2 3 1 3 2 3 4 3 5% 6% 68%	4180
September	1st to 10th	Day	3 3 1 4 2 3 3 3 4 6% 68%	2280
	11th to 20th	Day	5% 5% 2 5% 3 5% 5% 4 6% 8% 53%	2157
	21st to end	Day	7% 5% 2 5% 4 3 5% 4 5% 5% 55%	2090
October	1st to 10th	Day	5% 5% 2 4 3 3 3 3 4 4 63%	3413
	11th to 20th	Day	5% 6% 2 5% 4 4 5% 4 6% 8% 50%	3010
	21st to end	Day	5% 9% 4 9% 6% 6% 5% 6% 7% 8% 37%	3101
November	1st to 10th	Day	5% 11% 3 8% 7% 7% 7% 5% 7% 8% 32%	1710
	11th to 20th	Day	3 8% 4 9% 6% 6% 7% 6% 10% 11% 31%	1710
	21st to end	Day	2 8% 4 8% 6% 6% 7% 6% 9% 8% 36%	1535
December	1st to 10th	Day	2 9% 3 11% 7% 6% 6% 6% 7% 8% 35%	1520
	11th to 20th	Day	2 9% 3 10% 6% 7% 7% 7% 9% 10% 30%	1928
	21st to end	Day	4 9% 4 9% 6% 7% 7% 5% 7% 9% 33%	2794
January	1st to 10th	Night	2 9% 4 10% 7% 7% 8% 7% 9% 10% 27%	4406
	11th to 20th	Night	3 11% 4 12% 7% 7% 7% 6% 7% 10% 26%	4420
	21st to end	Night	1 7% 3 8% 7% 7% 7% 6% 9% 11% 34%	4862
February	1st to 10th	Night	3 10% 5% 11% 8% 7% 7% 6% 8% 7% 28%	2599
	11th to 20th	Night	2 9% 5% 10% 7% 7% 7% 6% 8% 9% 30%	2225
	21st to end	Night	2 8% 3 11% 8% 7% 7% 7% 11% 9% 27%	1884
March	1st to 10th	Night	2 6% 3 8% 5% 5% 7% 6% 11% 11% 37%	3736
	11th to 20th	Night	1 7% 2 6% 4 5% 6% 6% 7% 8% 47%	3690
	21st to end	Night	3 10% 4 9% 7% 9% 8% 6% 11% 11% 22%	3533
April	1st to 10th	Night	4 10% 4 8% 6% 7% 6% 5% 8% 9% 33%	1900
	11th to 20th	Night	6% 9% 3 7% 7% 5% 6% 4 6% 7% 40%	1850
	21st to end	Night	7% 10% 2 7% 6% 5% 6% 4 6% 8% 38%	1710
May	1st to 10th	Night	10% 8% 2 6% 4 4 6% 4 6% 8% 42%	2796
	11th to 20th	Night	5% 5% 1 5% 3 4 4 4 6% 7% 56%	2516
	21st to end	Night	11% 11% 3 7% 4 4 4 3 5% 6% 43%	2762
June	1st to 10th	Night	8% 6% 3 5% 6% 4 5% 5% 7% 9% 42%	1520
	11th to 20th	Night	10% 6% 2 5% 4 3 5% 3 6% 8% 49%	1520
	21st to end	Night	4 3 1 3 3 3 4 3 5% 6% 64%	1520
July	1st to 10th	Night	1 1 1 1 1 2 2 3 4 83%	2540
	11th to 20th	Night	1 1 1 1 2 1 2 3 5% 85%	2540
	21st to end	Night	1 1 1 1 2 2 3 3 5% 6% 76%	2761
August	1st to 10th	Night	2 2 1 3 2 2 3 3 5% 7% 70%	2529
	11th to 20th	Night	1 1 2 1 2 3 3 4 6% 77%	2816
	21st to end	Night	2 2 1 3 2 2 3 2 4 5% 73%	3498
September	1st to 10th	Night	3 2 1 3 2 3 3 3 4 6% 70%	1900
	11th to 20th	Night	3 4 2 4 3 4 5% 4 5% 7% 58%	2023
	21st to end	Night	5% 5% 2 4 3 4 3 3 4 6% 59%	2090
October	1st to 10th	Night	5% 4 1 4 2 2 3 3 5% 6% 65%	3552
	11th to 20th	Night	3 6% 2 5% 4 4 5% 4 6% 9% 53%	3922
	21st to end	Night	3 7% 3 8% 4 5% 6% 6% 7% 9% 42%	4457
November	1st to 10th	Night	4 9% 3 8% 7% 6% 6% 6% 7% 9% 36%	2469
	11th to 20th	Night	4 7% 3 8% 6% 6% 7% 6% 8% 11% 34%	2470
	21st to end	Night	3 6% 3 7% 6% 7% 7% 5% 8% 9% 40%	2644
December	1st to 10th	Night	2 6% 2 8% 6% 7% 8% 6% 8% 10% 37%	2660
	11th to 20th	Night	2 7% 3 8% 6% 6% 8% 6% 9% 11% 33%	3276
	21st to end	Night	1 10% 4 9% 6% 7% 6% 5% 8% 9% 36%	4862

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	50% 16% 16% 15% 2	2539
	11th to 20th	Day	50% 10% 16% 14% 8% 2	2540
	21st to end	Day	52% 16% 15% 11% 5% 1	2794
February	1st to 10th	Day	51% 13% 14% 16% 4 1	1579
	11th to 20th	Day	54% 12% 14% 13% 6% 1	1851
	21st to end	Day	55% 11% 14% 13% 6% 1	1570
March	1st to 10th	Day	49% 8% 19% 14% 10%	3138
	11th to 20th	Day	37% 8% 12% 37% 6%	3289
	21st to end	Day	60% 16% 14% 8% 3	4117
April	1st to 10th	Day	56% 8% 17% 15% 4	2280
	11th to 20th	Day	48% 9% 16% 15% 11% 1	2280
	21st to end	Day	51% 9% 12% 19% 9%	2470
May	1st to 10th	Day	42% 9% 17% 23% 9% 1	4169
	11th to 20th	Day	30% 5% 18% 30% 13% 4	4380
	21st to end	Day	44% 10% 21% 21% 5%	4814
June	1st to 10th	Day	48% 10% 13% 22% 7%	2660
	11th to 20th	Day	42% 8% 13% 22% 12% 3	2660
	21st to end	Day	21% 7% 13% 31% 23% 5%	2660
July	1st to 10th	Day	11% 3 8% 15% 26% 38%	4351
	11th to 20th	Day	10% 3 7% 11% 23% 46%	4345
	21st to end	Day	10% 3 7% 18% 39% 24%	4639
August	1st to 10th	Day	19% 4 9% 16% 35% 18%	4384
	11th to 20th	Day	16% 4 9% 29% 31% 12%	4059
	21st to end	Day	16% 4 10% 30% 26% 14%	4179
September	1st to 10th	Day	17% 5% 10% 24% 29% 15%	2280
	11th to 20th	Day	28% 6% 13% 21% 23% 9%	2157
	21st to end	Day	30% 6% 11% 28% 21% 4	2090
October	1st to 10th	Day	24% 5% 11% 22% 32% 6%	3413
	11th to 20th	Day	30% 5% 17% 29% 17% 1	3010
	21st to end	Day	41% 9% 11% 27% 12%	3101
November	1st to 10th	Day	47% 9% 17% 18% 8% 1	1710
	11th to 20th	Day	44% 13% 18% 18% 6%	1710
	21st to end	Day	42% 12% 17% 15% 12% 2	1535
December	1st to 10th	Day	46% 14% 18% 10% 10% 2	1520
	11th to 20th	Day	50% 18% 14% 12% 4	1928
	21st to end	Day	46% 10% 18% 19% 6% 1	2794
January	1st to 10th	Night	48% 15% 14% 19% 3 1	4406
	11th to 20th	Night	50% 12% 14% 13% 9% 1	4420
	21st to end	Night	45% 20% 15% 15% 4	4862
February	1st to 10th	Night	53% 13% 14% 15% 5% 1	2599
	11th to 20th	Night	47% 14% 14% 16% 8% 1	2226
	21st to end	Night	51% 13% 15% 13% 6% 1	1884
March	1st to 10th	Night	39% 11% 20% 14% 16%	3736
	11th to 20th	Night	34% 10% 13% 36% 7%	3690
	21st to end	Night	47% 19% 16% 14% 4	3533
April	1st to 10th	Night	46% 11% 18% 19% 5%	1900
	11th to 20th	Night	42% 8% 16% 22% 11% 2	1850
	21st to end	Night	42% 12% 14% 20% 12%	1710
May	1st to 10th	Night	37% 10% 15% 23% 13% 2	2796
	11th to 20th	Night	25% 7% 13% 33% 22%	2516
	21st to end	Night	39% 9% 21% 26% 6%	2762
June	1st to 10th	Night	38% 12% 15% 27% 8% 1	1520
	11th to 20th	Night	33% 8% 17% 26% 14% 3	1520
	21st to end	Night	21% 7% 13% 29% 25% 4	1520
July	1st to 10th	Night	7% 3 7% 15% 28% 40%	2500
	11th to 20th	Night	5% 3 7% 16% 20% 49%	2492
	21st to end	Night	10% 2 7% 20% 36% 25%	2674
August	1st to 10th	Night	13% 3 8% 18% 45% 12%	2521
	11th to 20th	Night	10% 5% 7% 33% 35% 11%	2843
	21st to end	Night	15% 3 8% 32% 30% 12%	3498
September	1st to 10th	Night	15% 4 10% 27% 27% 17%	1900
	11th to 20th	Night	24% 7% 12% 24% 23% 10%	2023
	21st to end	Night	28% 6% 11% 28% 20% 7%	2090
October	1st to 10th	Night	23% 6% 8% 25% 30% 9%	3552
	11th to 20th	Night	27% 7% 22% 23% 20% 2	3922
	21st to end	Night	34% 9% 13% 29% 14% 1	4457
November	1st to 10th	Night	43% 12% 15% 18% 10% 2	2469
	11th to 20th	Night	43% 13% 16% 21% 7%	2470
	21st to end	Night	40% 11% 13% 19% 14% 2	2644
December	1st to 10th	Night	41% 15% 19% 16% 8% 2	2660
	11th to 20th	Night	44% 20% 14% 17% 4 1	3276
	21st to end	Night	43% 12% 18% 19% 8% 1	4862

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	4 16% 36% 24% 16% 3	180
	11th to 20th	Day	8% 12% 36% 28% 9% 7%	180
	21st to end	Day	10% 13% 35% 25% 16% 2	198
February	1st to 10th	Day	11% 18% 40% 23% 7% 1	239
	11th to 20th	Day	7% 21% 39% 22% 10% 1	451
	21st to end	Day	8% 24% 28% 30% 9% 1	382
March	1st to 10th	Day	8% 20% 38% 26% 7% 1	460
	11th to 20th	Day	9% 19% 28% 30% 11% 3	460
	21st to end	Day	16% 20% 31% 26% 6% 2	506
April	1st to 10th	Day	12% 22% 31% 23% 11% 2	460
	11th to 20th	Day	11% 21% 33% 22% 10% 4	452
	21st to end	Day	15% 15% 30% 27% 10% 2	460
May	1st to 10th	Day	11% 13% 28% 32% 12% 4	463
	11th to 20th	Day	20% 12% 24% 24% 14% 6%	488
	21st to end	Day	19% 9% 22% 25% 19% 6%	529
June	1st to 10th	Day	11% 11% 26% 26% 18% 7%	490
	11th to 20th	Day	12% 17% 33% 23% 12% 3	490
	21st to end	Day	6% 8% 27% 33% 21% 5%	490
July	1st to 10th	Day	3 7% 28% 36% 21% 6%	486
	11th to 20th	Day	1 7% 32% 36% 19% 5%	484
	21st to end	Day	1 4 30% 36% 23% 7%	531
August	1st to 10th	Day	4 6% 22% 36% 22% 9%	487
	11th to 20th	Day	2 5% 21% 37% 24% 11%	477
	21st to end	Day	4 9% 23% 35% 21% 8%	539
September	1st to 10th	Day	6% 7% 23% 31% 24% 10%	490
	11th to 20th	Day	8% 8% 26% 32% 19% 8%	490
	21st to end	Day	9% 9% 24% 34% 18% 5%	490
October	1st to 10th	Day	12% 10% 25% 28% 18% 6%	490
	11th to 20th	Day	6% 12% 28% 30% 18% 6%	403
	21st to end	Day	11% 11% 32% 28% 16% 3	330
November	1st to 10th	Day	10% 14% 32% 33% 10%	282
	11th to 20th	Day	6% 11% 33% 33% 14% 3	270
	21st to end	Day	5% 9% 31% 37% 16% 2	187
December	1st to 10th	Day	6% 12% 27% 32% 14% 8%	180
	11th to 20th	Day	8% 11% 44% 26% 10% 1	180
	21st to end	Day	7% 14% 38% 27% 12% 3	198
January	1st to 10th	Night	8% 12% 35% 28% 15% 2	760
	11th to 20th	Night	7% 12% 33% 29% 15% 3	760
	21st to end	Night	6% 8% 31% 35% 19% 2	836
February	1st to 10th	Night	8% 12% 37% 33% 9% 1	760
	11th to 20th	Night	7% 8% 38% 31% 14% 2	744
	21st to end	Night	7% 14% 33% 32% 12% 3	628
March	1st to 10th	Night	6% 9% 37% 32% 14% 2	760
	11th to 20th	Night	8% 8% 33% 32% 16% 3	760
	21st to end	Night	10% 11% 31% 35% 12% 1	836
April	1st to 10th	Night	9% 8% 31% 36% 15% 2	760
	11th to 20th	Night	10% 9% 31% 31% 16% 3	722
	21st to end	Night	12% 9% 25% 37% 16% 2	570
May	1st to 10th	Night	11% 7% 24% 39% 16% 2	532
	11th to 20th	Night	10% 5% 18% 34% 28% 5%	374
	21st to end	Night	13% 6% 14% 34% 28% 5%	411
June	1st to 10th	Night	10% 6% 18% 41% 22% 3	380
	11th to 20th	Night	12% 6% 19% 41% 19% 3	380
	21st to end	Night	6% 1 13% 47% 32% 1	380
July	1st to 10th	Night	1 2 12% 48% 35% 3	370
	11th to 20th	Night	2 1 10% 58% 27% 1	368
	21st to end	Night	2 1 8% 55% 31% 3	416
August	1st to 10th	Night	2 1 8% 48% 36% 4	378
	11th to 20th	Night	1 1 10% 46% 34% 7%	556
	21st to end	Night	4 2 15% 42% 33% 6%	836
September	1st to 10th	Night	4 2 12% 43% 32% 7%	760
	11th to 20th	Night	4 3 14% 36% 34% 9%	760
	21st to end	Night	9% 3 19% 35% 26% 8%	760
October	1st to 10th	Night	11% 4 19% 39% 23% 5%	760
	11th to 20th	Night	6% 6% 24% 37% 20% 7%	760
	21st to end	Night	8% 6% 28% 38% 15% 5%	836
November	1st to 10th	Night	10% 7% 32% 40% 11% 1	760
	11th to 20th	Night	8% 11% 34% 34% 12% 2	760
	21st to end	Night	6% 9% 31% 34% 16% 4	760
December	1st to 10th	Night	8% 8% 33% 34% 15% 2	760
	11th to 20th	Night	7% 8% 36% 35% 11% 2	760
	21st to end	Night	7% 12% 39% 33% 8% 1	836

Page generated at 2024-11-02 23:11:09. Version ac07

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