Dry Sandy Crossing
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dry Sandy Crossing clear sky chart from 2005-11-06 to 2024-11-01.

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	3 5% 2 6% 5% 5% 5% 4 6% 8% 51%	101403
	Night	3 6% 2 7% 5% 5% 5% 4 6% 8% 49%	97797
Transparency	Day	30% 4 12% 24% 20% 10%	101158
	Night	32% 4 13% 25% 18% 7%	97632
Seeing	Day	6% 8% 27% 32% 20% 6%	15626
	Night	6% 6% 30% 41% 15% 2	25725

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	2 5% 2 11% 7% 7% 10% 8% 11% 11% 26%	2545
	11th to 20th	Day	2 6% 3 8% 8% 7% 7% 5% 7% 9% 38%	2860
	21st to end	Day	1 5% 3 14% 15% 11% 8% 5% 5% 7% 25%	3146
February	1st to 10th	Day	2 7% 4 9% 5% 6% 6% 5% 6% 10% 39%	1710
	11th to 20th	Day	2 7% 4 8% 5% 5% 6% 4 7% 8% 44%	1665
	21st to end	Day	2 8% 3 8% 6% 6% 4 4 7% 9% 42%	1491
March	1st to 10th	Day	1 7% 3 8% 6% 5% 6% 6% 8% 10% 40%	3444
	11th to 20th	Day	1 4 3 6% 5% 7% 8% 6% 7% 9% 45%	3490
	21st to end	Day	3 10% 4 10% 7% 6% 5% 5% 7% 8% 35%	3825
April	1st to 10th	Day	4 9% 3 8% 4 4 5% 4 6% 8% 44%	2249
	11th to 20th	Day	4 9% 2 6% 6% 5% 5% 5% 6% 8% 44%	2251
	21st to end	Day	5% 8% 2 7% 5% 4 5% 5% 8% 8% 43%	2467
May	1st to 10th	Day	6% 9% 3 7% 5% 5% 5% 5% 6% 8% 39%	4110
	11th to 20th	Day	6% 4 1 4 4 3 5% 4 6% 8% 53%	4290
	21st to end	Day	4 5% 2 5% 4 4 5% 4 7% 8% 51%	4825
June	1st to 10th	Day	4 4 1 4 4 5% 5% 5% 7% 10% 51%	2660
	11th to 20th	Day	4 4 1 4 3 4 4 3 6% 8% 60%	2660
	21st to end	Day	2 2 1 3 3 4 4 3 5% 7% 66%	2660
July	1st to 10th	Day	2 2 1 2 2 2 3 3 4 6% 74%	4430
	11th to 20th	Day	2 1 1 3 3 4 4 4 7% 9% 61%	4352
	21st to end	Day	3 2 1 4 3 4 4 4 6% 8% 60%	4454
August	1st to 10th	Day	2 2 1 4 3 4 5% 4 6% 8% 60%	4092
	11th to 20th	Day	3 2 1 3 3 3 4 4 6% 8% 63%	4028
	21st to end	Day	2 1 1 3 3 3 3 3 4 8% 70%	4314
September	1st to 10th	Day	3 3 1 3 3 2 3 3 5% 7% 67%	2280
	11th to 20th	Day	3 3 1 4 3 3 4 4 5% 6% 64%	2180
	21st to end	Day	5% 4 1 4 2 3 3 2 3 5% 67%	2058
October	1st to 10th	Day	7% 5% 2 5% 3 3 3 2 5% 6% 59%	1900
	11th to 20th	Day	6% 5% 1 3 3 3 3 3 6% 8% 59%	1900
	21st to end	Day	3 5% 2 7% 3 4 4 3 6% 8% 55%	2090
November	1st to 10th	Day	4 7% 2 6% 4 5% 5% 5% 6% 6% 52%	1697
	11th to 20th	Day	2 5% 2 7% 5% 5% 5% 4 6% 10% 49%	1520
	21st to end	Day	1 7% 2 7% 4 5% 4 4 7% 11% 48%	1520
December	1st to 10th	Day	2 6% 3 8% 7% 6% 6% 4 7% 10% 41%	1520
	11th to 20th	Day	2 7% 3 9% 8% 7% 7% 5% 9% 9% 35%	1926
	21st to end	Day	2 9% 3 11% 7% 8% 7% 6% 9% 11% 27%	2794
January	1st to 10th	Night	1 7% 4 10% 7% 7% 8% 8% 11% 9% 29%	4417
	11th to 20th	Night	1 6% 4 11% 7% 6% 6% 5% 8% 10% 36%	4133
	21st to end	Night	2 9% 4 16% 13% 9% 6% 4 6% 6% 24%	4521
February	1st to 10th	Night	2 7% 4 8% 7% 5% 7% 5% 8% 8% 39%	2470
	11th to 20th	Night	3 8% 3 7% 5% 6% 6% 4 7% 10% 42%	2402
	21st to end	Night	2 7% 4 10% 6% 5% 6% 5% 6% 9% 40%	1961
March	1st to 10th	Night	2 7% 2 8% 5% 5% 5% 4 7% 10% 44%	3430
	11th to 20th	Night	1 6% 3 6% 4 5% 5% 5% 6% 9% 49%	3490
	21st to end	Night	3 10% 4 10% 6% 5% 5% 4 6% 7% 38%	3828
April	1st to 10th	Night	4 9% 3 5% 4 4 5% 5% 5% 8% 48%	1930
	11th to 20th	Night	3 9% 3 7% 5% 4 5% 3 6% 9% 45%	1877
	21st to end	Night	5% 7% 2 6% 5% 5% 5% 4 6% 8% 48%	1710
May	1st to 10th	Night	5% 11% 4 8% 4 4 5% 4 6% 8% 42%	2860
	11th to 20th	Night	4 4 1 5% 3 4 4 5% 5% 8% 57%	2613
	21st to end	Night	5% 5% 2 6% 4 4 4 4 6% 6% 54%	2762
June	1st to 10th	Night	4 4 2 3 2 4 3 4 6% 11% 56%	1520
	11th to 20th	Night	3 3 2 4 4 3 4 3 5% 8% 61%	1520
	21st to end	Night	2 2 1 3 3 3 3 4 4 7% 67%	1520
July	1st to 10th	Night	2 2 1 3 3 3 4 4 7% 7% 64%	2540
	11th to 20th	Night	1 2 1 3 3 4 5% 4 7% 10% 60%	2600
	21st to end	Night	1 1 1 3 3 3 4 5% 7% 9% 61%	3109
August	1st to 10th	Night	2 1 1 4 3 3 4 4 6% 8% 64%	2847
	11th to 20th	Night	2 2 1 5% 4 5% 4 3 5% 7% 62%	2811
	21st to end	Night	2 2 1 3 3 3 3 3 5% 8% 69%	3353
September	1st to 10th	Night	4 3 1 3 3 3 2 3 4 6% 69%	1900
	11th to 20th	Night	3 2 1 3 3 3 3 3 5% 9% 65%	1997
	21st to end	Night	5% 3 1 3 3 2 3 3 3 5% 69%	2121
October	1st to 10th	Night	6% 6% 2 4 3 3 4 3 4 6% 59%	2280
	11th to 20th	Night	5% 5% 2 5% 3 3 3 2 4 7% 61%	2280
	21st to end	Night	5% 5% 2 5% 4 4 4 3 5% 8% 56%	2508
November	1st to 10th	Night	4 5% 2 6% 4 5% 4 3 6% 9% 52%	2363
	11th to 20th	Night	3 5% 3 6% 4 4 4 3 6% 8% 53%	2660
	21st to end	Night	2 7% 3 6% 4 4 4 4 6% 9% 50%	2660
December	1st to 10th	Night	3 7% 3 7% 5% 6% 5% 5% 7% 10% 41%	2660
	11th to 20th	Night	3 8% 3 7% 6% 4 5% 5% 9% 11% 39%	3271
	21st to end	Night	2 8% 4 9% 7% 8% 7% 5% 8% 9% 31%	4873

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	47% 8% 15% 21% 9% 1	2546
	11th to 20th	Day	41% 6% 18% 22% 11% 1	2860
	21st to end	Day	59% 4 17% 13% 6% 1	3146
February	1st to 10th	Day	39% 8% 18% 25% 10% 1	1710
	11th to 20th	Day	37% 7% 20% 24% 9% 2	1674
	21st to end	Day	35% 6% 17% 26% 14% 2	1491
March	1st to 10th	Day	37% 5% 18% 27% 12% 1	3444
	11th to 20th	Day	36% 4 22% 26% 12% 1	3490
	21st to end	Day	47% 4 19% 27% 4	3825
April	1st to 10th	Day	36% 6% 19% 24% 13% 2	2249
	11th to 20th	Day	36% 5% 16% 29% 13% 1	2254
	21st to end	Day	36% 4 15% 32% 13%	2467
May	1st to 10th	Day	42% 4 10% 26% 14% 5%	4110
	11th to 20th	Day	28% 2 10% 38% 16% 6%	4294
	21st to end	Day	31% 4 10% 32% 21% 3	4825
June	1st to 10th	Day	27% 5% 15% 30% 20% 4	2660
	11th to 20th	Day	24% 3 10% 22% 28% 14%	2660
	21st to end	Day	18% 3 4 22% 34% 19%	2660
July	1st to 10th	Day	12% 3 4 16% 29% 35%	4361
	11th to 20th	Day	19% 2 3 15% 30% 30%	4277
	21st to end	Day	22% 2 3 15% 34% 23%	4314
August	1st to 10th	Day	21% 2 5% 20% 30% 21%	4078
	11th to 20th	Day	20% 2 5% 24% 33% 16%	4067
	21st to end	Day	16% 2 6% 17% 36% 23%	4313
September	1st to 10th	Day	17% 3 6% 21% 33% 19%	2280
	11th to 20th	Day	20% 3 8% 27% 27% 14%	2180
	21st to end	Day	21% 3 6% 30% 32% 9%	2058
October	1st to 10th	Day	27% 3 12% 30% 22% 6%	1900
	11th to 20th	Day	24% 3 15% 35% 18% 5%	1900
	21st to end	Day	28% 3 17% 32% 18% 1	2090
November	1st to 10th	Day	32% 5% 16% 28% 17% 2	1697
	11th to 20th	Day	30% 6% 22% 27% 14% 2	1520
	21st to end	Day	30% 7% 19% 27% 16% 2	1520
December	1st to 10th	Day	37% 7% 22% 21% 12% 2	1520
	11th to 20th	Day	42% 6% 20% 26% 6%	1924
	21st to end	Day	49% 5% 10% 17% 14% 5%	2794
January	1st to 10th	Night	45% 8% 14% 23% 9% 1	4417
	11th to 20th	Night	41% 8% 20% 20% 10% 1	4133
	21st to end	Night	59% 5% 15% 14% 6% 1	4521
February	1st to 10th	Night	40% 8% 18% 23% 10% 1	2470
	11th to 20th	Night	36% 7% 18% 26% 12% 2	2403
	21st to end	Night	39% 6% 17% 23% 13% 2	1961
March	1st to 10th	Night	35% 4 13% 35% 12% 1	3430
	11th to 20th	Night	32% 3 19% 32% 12% 1	3490
	21st to end	Night	46% 3 15% 31% 4 1	3828
April	1st to 10th	Night	34% 5% 18% 25% 15% 3	1930
	11th to 20th	Night	36% 4 16% 28% 16%	1877
	21st to end	Night	35% 3 14% 34% 13%	1710
May	1st to 10th	Night	41% 4 11% 24% 18% 3	2860
	11th to 20th	Night	27% 3 13% 39% 12% 7%	2614
	21st to end	Night	31% 3 10% 37% 17% 2	2762
June	1st to 10th	Night	24% 3 20% 29% 21% 4	1520
	11th to 20th	Night	23% 3 10% 24% 27% 14%	1520
	21st to end	Night	19% 2 4 19% 34% 22%	1520
July	1st to 10th	Night	19% 3 4 15% 28% 31%	2500
	11th to 20th	Night	19% 3 3 15% 31% 29%	2552
	21st to end	Night	18% 2 5% 18% 36% 21%	3011
August	1st to 10th	Night	18% 2 4 28% 26% 22%	2838
	11th to 20th	Night	24% 1 6% 19% 32% 18%	2838
	21st to end	Night	15% 2 8% 20% 26% 29%	3353
September	1st to 10th	Night	17% 2 6% 22% 30% 23%	1900
	11th to 20th	Night	18% 3 9% 27% 30% 13%	1997
	21st to end	Night	19% 2 8% 29% 33% 9%	2121
October	1st to 10th	Night	27% 3 10% 29% 24% 6%	2280
	11th to 20th	Night	25% 3 13% 34% 20% 6%	2280
	21st to end	Night	28% 3 16% 32% 18% 2	2508
November	1st to 10th	Night	29% 5% 15% 29% 19% 3	2363
	11th to 20th	Night	29% 5% 20% 32% 12% 2	2660
	21st to end	Night	29% 5% 18% 30% 15% 2	2660
December	1st to 10th	Night	37% 7% 22% 22% 11% 2	2660
	11th to 20th	Night	36% 5% 20% 29% 9%	3272
	21st to end	Night	46% 6% 10% 18% 15% 4	4873

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	7% 7% 26% 40% 12% 7%	270
	11th to 20th	Day	6% 5% 29% 37% 18% 4	270
	21st to end	Day	1 3 35% 42% 14% 5%	297
February	1st to 10th	Day	8% 10% 42% 31% 9%	270
	11th to 20th	Day	4 7% 44% 31% 10% 4	270
	21st to end	Day	5% 12% 40% 33% 9% 2	249
March	1st to 10th	Day	5% 11% 33% 37% 13% 2	460
	11th to 20th	Day	4 8% 27% 42% 17% 3	460
	21st to end	Day	8% 7% 27% 42% 15% 2	506
April	1st to 10th	Day	11% 10% 27% 34% 15% 3	460
	11th to 20th	Day	9% 13% 34% 28% 14% 1	452
	21st to end	Day	11% 14% 27% 25% 20% 4	460
May	1st to 10th	Day	12% 18% 25% 25% 16% 4	463
	11th to 20th	Day	10% 10% 21% 31% 23% 5%	616
	21st to end	Day	9% 9% 24% 27% 21% 10%	734
June	1st to 10th	Day	5% 7% 24% 27% 27% 10%	680
	11th to 20th	Day	5% 9% 32% 32% 18% 3	680
	21st to end	Day	3 5% 24% 37% 24% 7%	680
July	1st to 10th	Day	3 4 17% 37% 31% 8%	671
	11th to 20th	Day	4 6% 18% 33% 31% 8%	629
	21st to end	Day	5% 4 17% 33% 29% 12%	531
August	1st to 10th	Day	3 3 20% 31% 32% 11%	487
	11th to 20th	Day	3 4 22% 28% 26% 16%	477
	21st to end	Day	4 4 25% 26% 29% 12%	539
September	1st to 10th	Day	5% 7% 22% 27% 26% 13%	490
	11th to 20th	Day	4 11% 27% 28% 19% 10%	490
	21st to end	Day	6% 9% 26% 29% 21% 9%	458
October	1st to 10th	Day	10% 6% 22% 28% 25% 9%	300
	11th to 20th	Day	9% 10% 27% 30% 18% 7%	300
	21st to end	Day	7% 13% 36% 29% 12% 2	330
November	1st to 10th	Day	10% 10% 34% 34% 10% 1	270
	11th to 20th	Day	6% 11% 36% 37% 8% 2	270
	21st to end	Day	5% 8% 37% 34% 13% 3	270
December	1st to 10th	Day	4 6% 37% 39% 12% 2	270
	11th to 20th	Day	5% 7% 39% 37% 11% 1	270
	21st to end	Day	8% 7% 32% 33% 14% 6%	297
January	1st to 10th	Night	6% 6% 32% 43% 11% 2	950
	11th to 20th	Night	4 8% 35% 37% 14% 2	770
	21st to end	Night	6% 5% 33% 42% 13% 2	836
February	1st to 10th	Night	5% 5% 45% 36% 8% 1	760
	11th to 20th	Night	6% 7% 35% 40% 9% 2	744
	21st to end	Night	5% 10% 41% 34% 9% 1	628
March	1st to 10th	Night	7% 5% 36% 39% 12% 2	760
	11th to 20th	Night	4 5% 30% 46% 14% 1	760
	21st to end	Night	9% 5% 31% 43% 11% 1	836
April	1st to 10th	Night	9% 8% 35% 39% 7% 1	600
	11th to 20th	Night	10% 9% 37% 34% 9% 1	563
	21st to end	Night	11% 8% 31% 36% 13% 1	570
May	1st to 10th	Night	10% 11% 32% 32% 14% 1	570
	11th to 20th	Night	8% 6% 29% 36% 20% 2	561
	21st to end	Night	8% 6% 27% 38% 18% 2	617
June	1st to 10th	Night	6% 5% 25% 39% 22% 2	570
	11th to 20th	Night	6% 8% 35% 41% 10%	570
	21st to end	Night	3 3 24% 46% 22% 1	570
July	1st to 10th	Night	3 2 21% 42% 30% 1	555
	11th to 20th	Night	1 3 17% 52% 25% 1	552
	21st to end	Night	3 1 12% 52% 31%	624
August	1st to 10th	Night	4 1 13% 51% 29% 1	567
	11th to 20th	Night	3 1 17% 51% 27% 1	564
	21st to end	Night	3 3 16% 46% 28% 4	627
September	1st to 10th	Night	5% 3 20% 46% 24% 2	570
	11th to 20th	Night	3 3 21% 47% 21% 5%	667
	21st to end	Night	6% 3 23% 39% 23% 6%	760
October	1st to 10th	Night	9% 5% 30% 34% 19% 2	760
	11th to 20th	Night	8% 7% 25% 41% 17% 2	760
	21st to end	Night	8% 7% 28% 41% 13% 3	836
November	1st to 10th	Night	7% 6% 38% 37% 12% 1	803
	11th to 20th	Night	5% 10% 37% 39% 8% 1	950
	21st to end	Night	6% 7% 35% 39% 12% 1	950
December	1st to 10th	Night	7% 9% 37% 37% 9% 1	950
	11th to 20th	Night	8% 6% 35% 42% 7% 1	950
	21st to end	Night	7% 9% 36% 36% 10% 2	1045

Page generated at 2024-10-29 09:20:46. Version ac07

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