Braidwood Dark Sky Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Braidwood Dark Sky Site clear sky chart from 2005-11-06 to 2024-11-03.

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	13% 9% 3 7% 5% 4 4 4 6% 7% 37%	101259
	Night	14% 9% 3 7% 5% 4 4 3 5% 6% 38%	97791
Transparency	Day	45% 4 12% 23% 13% 2	101047
	Night	46% 4 12% 22% 14% 2	97675
Seeing	Day	16% 9% 27% 25% 16% 6%	15764
	Night	18% 9% 30% 31% 12% 1	25591

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	15% 13% 7% 12% 5% 4 4 3 5% 5% 26%	2527
	11th to 20th	Day	14% 13% 6% 16% 6% 6% 4 7% 7% 3 18%	2530
	21st to end	Day	21% 23% 6% 12% 4 3 3 2 3 5% 18%	2915
February	1st to 10th	Day	18% 12% 5% 9% 6% 5% 5% 3 5% 6% 27%	1761
	11th to 20th	Day	15% 10% 4 8% 6% 5% 4 3 5% 6% 33%	1848
	21st to end	Day	16% 13% 5% 10% 5% 4 3 3 5% 6% 29%	1570
March	1st to 10th	Day	18% 16% 3 6% 4 3 3 3 4 5% 34%	3120
	11th to 20th	Day	10% 8% 3 7% 5% 4 5% 4 7% 8% 40%	3274
	21st to end	Day	19% 12% 5% 12% 5% 5% 5% 4 5% 6% 22%	4165
April	1st to 10th	Day	16% 12% 3 7% 6% 4 4 3 5% 7% 33%	2280
	11th to 20th	Day	16% 10% 3 7% 5% 4 4 3 5% 7% 37%	2254
	21st to end	Day	20% 8% 3 6% 5% 4 4 4 5% 7% 34%	2361
May	1st to 10th	Day	18% 7% 3 7% 4 5% 4 4 6% 9% 32%	4082
	11th to 20th	Day	15% 7% 3 6% 4 5% 4 4 6% 7% 41%	4262
	21st to end	Day	11% 6% 2 5% 4 4 4 4 6% 9% 44%	4824
June	1st to 10th	Day	10% 5% 2 6% 5% 4 4 4 6% 8% 45%	2660
	11th to 20th	Day	9% 4 2 6% 4 5% 5% 4 7% 8% 45%	2660
	21st to end	Day	10% 6% 2 6% 5% 4 6% 5% 7% 9% 39%	2660
July	1st to 10th	Day	12% 6% 3 7% 5% 6% 6% 5% 7% 9% 35%	4440
	11th to 20th	Day	7% 4 2 5% 4 4 5% 4 7% 10% 47%	4440
	21st to end	Day	9% 5% 2 6% 5% 5% 6% 4 7% 9% 41%	4813
August	1st to 10th	Day	8% 5% 2 6% 4 4 5% 3 7% 10% 46%	4257
	11th to 20th	Day	10% 5% 2 5% 4 3 5% 4 8% 11% 44%	3729
	21st to end	Day	7% 5% 2 6% 4 4 5% 4 6% 10% 48%	4180
September	1st to 10th	Day	10% 6% 2 5% 4 5% 4 3 5% 7% 49%	2280
	11th to 20th	Day	11% 5% 2 4 3 3 4 4 5% 7% 53%	2161
	21st to end	Day	10% 7% 2 6% 5% 3 3 4 6% 8% 45%	2090
October	1st to 10th	Day	11% 7% 3 6% 3 4 3 4 5% 7% 47%	2038
	11th to 20th	Day	18% 7% 2 6% 4 4 5% 3 4 6% 40%	1900
	21st to end	Day	19% 9% 3 7% 3 4 4 4 6% 6% 36%	1886
November	1st to 10th	Day	13% 7% 2 5% 4 3 3 3 5% 7% 48%	1690
	11th to 20th	Day	18% 10% 4 7% 5% 4 3 3 5% 6% 35%	1710
	21st to end	Day	18% 11% 3 9% 4 3 4 3 4 5% 36%	1671
December	1st to 10th	Day	15% 14% 4 9% 6% 5% 4 3 3 5% 31%	1520
	11th to 20th	Day	14% 14% 4 11% 6% 5% 5% 3 5% 5% 29%	1918
	21st to end	Day	22% 21% 9% 13% 5% 4 3 2 3 4 14%	2783
January	1st to 10th	Night	16% 15% 8% 10% 6% 4 3 3 4 4 28%	4428
	11th to 20th	Night	14% 20% 7% 12% 5% 5% 5% 4 5% 4 19%	4440
	21st to end	Night	24% 17% 7% 9% 4 4 3 3 3 4 22%	4751
February	1st to 10th	Night	17% 15% 4 8% 6% 4 3 2 4 6% 31%	2418
	11th to 20th	Night	14% 10% 3 8% 6% 4 5% 3 5% 7% 35%	2218
	21st to end	Night	20% 11% 3 8% 4 4 4 3 5% 5% 34%	1884
March	1st to 10th	Night	18% 11% 3 6% 3 3 3 3 4 6% 39%	3733
	11th to 20th	Night	11% 6% 3 6% 4 4 4 3 5% 6% 47%	3714
	21st to end	Night	21% 11% 4 9% 6% 5% 4 4 4 5% 26%	3466
April	1st to 10th	Night	15% 9% 3 7% 5% 4 4 4 4 7% 39%	1900
	11th to 20th	Night	19% 8% 2 5% 5% 3 4 3 4 7% 41%	1875
	21st to end	Night	20% 7% 2 6% 4 3 5% 5% 5% 7% 35%	1819
May	1st to 10th	Night	17% 8% 2 7% 5% 4 4 3 6% 8% 34%	2813
	11th to 20th	Night	15% 6% 2 6% 4 4 5% 4 7% 9% 39%	2635
	21st to end	Night	11% 6% 2 5% 4 5% 4 4 6% 8% 44%	2743
June	1st to 10th	Night	9% 6% 2 5% 4 3 5% 3 6% 7% 51%	1520
	11th to 20th	Night	9% 5% 2 6% 5% 3 4 4 6% 10% 47%	1520
	21st to end	Night	10% 6% 2 6% 5% 5% 5% 4 7% 8% 43%	1520
July	1st to 10th	Night	11% 5% 3 6% 4 5% 5% 4 7% 9% 40%	2530
	11th to 20th	Night	6% 4 1 5% 4 4 4 4 6% 7% 56%	2530
	21st to end	Night	5% 4 2 8% 5% 5% 6% 4 7% 8% 47%	2750
August	1st to 10th	Night	7% 5% 2 5% 4 4 4 4 7% 9% 50%	2657
	11th to 20th	Night	8% 4 2 5% 4 4 5% 4 6% 8% 52%	3100
	21st to end	Night	7% 4 2 5% 4 4 4 3 5% 9% 54%	3476
September	1st to 10th	Night	11% 5% 1 4 4 3 3 3 4 8% 54%	1900
	11th to 20th	Night	9% 4 1 5% 3 3 4 4 5% 7% 55%	2000
	21st to end	Night	10% 6% 1 6% 5% 5% 6% 4 6% 7% 44%	2090
October	1st to 10th	Night	10% 5% 2 5% 3 4 3 3 4 6% 54%	2137
	11th to 20th	Night	16% 6% 3 6% 3 3 3 3 4 6% 48%	2280
	21st to end	Night	20% 8% 3 6% 4 3 3 3 5% 6% 40%	2710
November	1st to 10th	Night	13% 7% 2 5% 4 3 4 3 4 6% 49%	2433
	11th to 20th	Night	14% 10% 3 8% 4 5% 5% 3 5% 6% 38%	2470
	21st to end	Night	19% 10% 3 6% 4 4 3 3 4 6% 38%	2508
December	1st to 10th	Night	16% 12% 4 10% 6% 3 3 3 4 6% 33%	2660
	11th to 20th	Night	16% 14% 4 9% 5% 4 3 3 4 5% 33%	3279
	21st to end	Night	23% 17% 7% 11% 6% 4 4 3 4 4 16%	4884

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	60% 3 13% 17% 6%	2528
	11th to 20th	Day	65% 4 9% 12% 9% 1	2530
	21st to end	Day	71% 3 8% 13% 5%	2915
February	1st to 10th	Day	58% 4 12% 16% 8% 2	1761
	11th to 20th	Day	51% 4 11% 23% 9% 2	1858
	21st to end	Day	56% 4 10% 21% 6% 3	1570
March	1st to 10th	Day	53% 3 11% 19% 12% 1	3120
	11th to 20th	Day	40% 4 13% 28% 13% 1	3274
	21st to end	Day	61% 4 15% 16% 3	4165
April	1st to 10th	Day	52% 3 11% 20% 13%	2280
	11th to 20th	Day	48% 4 10% 22% 12% 4	2254
	21st to end	Day	50% 5% 13% 18% 12% 2	2361
May	1st to 10th	Day	47% 6% 11% 25% 11%	4120
	11th to 20th	Day	42% 5% 12% 30% 11%	4266
	21st to end	Day	35% 6% 11% 22% 21% 5%	4837
June	1st to 10th	Day	35% 5% 12% 27% 17% 3	2660
	11th to 20th	Day	34% 6% 11% 24% 22% 3	2660
	21st to end	Day	40% 7% 14% 22% 15% 3	2660
July	1st to 10th	Day	45% 4 12% 24% 12% 2	4371
	11th to 20th	Day	31% 5% 16% 30% 17% 1	4365
	21st to end	Day	38% 5% 18% 18% 18% 3	4662
August	1st to 10th	Day	33% 4 17% 31% 13% 1	4242
	11th to 20th	Day	33% 4 12% 33% 16% 1	3765
	21st to end	Day	33% 4 12% 31% 17% 3	4179
September	1st to 10th	Day	34% 5% 13% 25% 19% 5%	2280
	11th to 20th	Day	30% 4 12% 28% 22% 4	2161
	21st to end	Day	37% 4 9% 27% 21% 2	2090
October	1st to 10th	Day	37% 5% 11% 25% 19% 2	2038
	11th to 20th	Day	44% 4 11% 23% 16% 1	1900
	21st to end	Day	49% 4 11% 24% 11% 2	1886
November	1st to 10th	Day	36% 4 15% 26% 16% 3	1690
	11th to 20th	Day	50% 3 12% 22% 12% 1	1710
	21st to end	Day	52% 4 11% 23% 10%	1671
December	1st to 10th	Day	58% 3 11% 20% 7% 1	1520
	11th to 20th	Day	57% 5% 11% 20% 7% 1	1915
	21st to end	Day	76% 3 8% 9% 4	2783
January	1st to 10th	Night	59% 4 11% 16% 9%	4428
	11th to 20th	Night	68% 3 10% 12% 7%	4440
	21st to end	Night	68% 3 9% 14% 6%	4751
February	1st to 10th	Night	56% 4 10% 18% 10% 2	2418
	11th to 20th	Night	48% 4 10% 23% 12% 1	2219
	21st to end	Night	53% 4 9% 20% 11% 3	1884
March	1st to 10th	Night	48% 3 13% 24% 10% 3	3733
	11th to 20th	Night	38% 4 10% 28% 18% 2	3714
	21st to end	Night	59% 4 11% 19% 6% 1	3466
April	1st to 10th	Night	45% 5% 12% 22% 13% 2	1900
	11th to 20th	Night	44% 4 8% 22% 17% 4	1875
	21st to end	Night	46% 6% 12% 21% 12% 3	1819
May	1st to 10th	Night	47% 4 13% 21% 12% 2	2840
	11th to 20th	Night	41% 5% 17% 27% 10% 1	2636
	21st to end	Night	36% 7% 11% 21% 20% 5%	2751
June	1st to 10th	Night	33% 5% 13% 26% 20% 4	1520
	11th to 20th	Night	33% 4 13% 24% 23% 3	1520
	21st to end	Night	37% 6% 16% 22% 15% 4	1520
July	1st to 10th	Night	41% 4 13% 24% 12% 5%	2490
	11th to 20th	Night	28% 4 13% 29% 24% 2	2482
	21st to end	Night	34% 5% 17% 21% 19% 5%	2662
August	1st to 10th	Night	31% 4 19% 29% 16% 1	2648
	11th to 20th	Night	30% 4 15% 29% 20% 2	3130
	21st to end	Night	29% 4 13% 33% 19% 3	3476
September	1st to 10th	Night	30% 4 11% 26% 23% 5%	1900
	11th to 20th	Night	29% 3 9% 28% 26% 4	2000
	21st to end	Night	36% 6% 10% 26% 18% 3	2090
October	1st to 10th	Night	32% 5% 10% 27% 24% 3	2137
	11th to 20th	Night	38% 4 8% 27% 22% 2	2280
	21st to end	Night	47% 3 9% 24% 16% 2	2710
November	1st to 10th	Night	37% 4 10% 27% 18% 4	2433
	11th to 20th	Night	47% 3 12% 23% 14% 2	2470
	21st to end	Night	49% 3 11% 24% 12% 1	2508
December	1st to 10th	Night	54% 3 12% 21% 9% 1	2660
	11th to 20th	Night	55% 4 11% 19% 10% 1	3281
	21st to end	Night	73% 3 8% 11% 4	4884

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	23% 10% 36% 22% 9% 1	270
	11th to 20th	Day	26% 14% 38% 16% 6%	270
	21st to end	Day	24% 19% 25% 25% 7%	297
February	1st to 10th	Day	23% 17% 38% 15% 7%	270
	11th to 20th	Day	24% 13% 36% 22% 4	270
	21st to end	Day	24% 18% 39% 16% 3	225
March	1st to 10th	Day	21% 21% 37% 17% 4	270
	11th to 20th	Day	22% 18% 34% 19% 7%	289
	21st to end	Day	29% 13% 34% 16% 7% 2	506
April	1st to 10th	Day	22% 12% 35% 23% 7% 1	460
	11th to 20th	Day	20% 16% 32% 17% 12% 3	452
	21st to end	Day	22% 13% 33% 22% 7% 2	460
May	1st to 10th	Day	22% 11% 29% 25% 10% 3	463
	11th to 20th	Day	20% 8% 29% 24% 14% 5%	590
	21st to end	Day	16% 8% 29% 22% 18% 8%	734
June	1st to 10th	Day	10% 8% 27% 30% 19% 6%	680
	11th to 20th	Day	11% 5% 28% 32% 20% 5%	680
	21st to end	Day	12% 8% 30% 29% 16% 5%	680
July	1st to 10th	Day	11% 3 17% 28% 26% 15%	671
	11th to 20th	Day	10% 3 20% 32% 22% 13%	668
	21st to end	Day	9% 2 17% 36% 28% 8%	739
August	1st to 10th	Day	7% 3 16% 34% 28% 13%	611
	11th to 20th	Day	13% 3 16% 28% 25% 15%	479
	21st to end	Day	8% 2 14% 33% 30% 13%	539
September	1st to 10th	Day	13% 6% 18% 26% 28% 10%	490
	11th to 20th	Day	11% 3 13% 30% 32% 12%	490
	21st to end	Day	14% 6% 25% 26% 21% 8%	490
October	1st to 10th	Day	15% 6% 29% 26% 19% 6%	438
	11th to 20th	Day	18% 19% 28% 26% 8% 1	300
	21st to end	Day	29% 11% 33% 19% 6% 1	330
November	1st to 10th	Day	14% 9% 39% 20% 13% 5%	276
	11th to 20th	Day	26% 13% 33% 17% 10% 1	270
	21st to end	Day	24% 12% 33% 21% 9%	270
December	1st to 10th	Day	18% 15% 38% 19% 9% 1	270
	11th to 20th	Day	17% 17% 35% 24% 6% 1	270
	21st to end	Day	26% 17% 38% 16% 3	297
January	1st to 10th	Night	20% 15% 38% 22% 5%	950
	11th to 20th	Night	23% 14% 37% 21% 5% 1	950
	21st to end	Night	24% 12% 34% 27% 4	1045
February	1st to 10th	Night	25% 12% 36% 24% 4	898
	11th to 20th	Night	19% 13% 36% 28% 4	743
	21st to end	Night	25% 11% 39% 20% 4	628
March	1st to 10th	Night	21% 15% 35% 24% 5%	760
	11th to 20th	Night	17% 11% 38% 27% 6% 1	732
	21st to end	Night	27% 9% 34% 24% 5%	627
April	1st to 10th	Night	19% 11% 38% 26% 6%	570
	11th to 20th	Night	24% 10% 31% 28% 7% 1	563
	21st to end	Night	23% 8% 34% 28% 7%	570
May	1st to 10th	Night	19% 6% 33% 34% 8%	570
	11th to 20th	Night	17% 5% 31% 34% 12% 1	561
	21st to end	Night	13% 4 29% 35% 18% 1	617
June	1st to 10th	Night	11% 3 27% 45% 13%	570
	11th to 20th	Night	11% 3 26% 44% 15% 1	570
	21st to end	Night	11% 3 25% 42% 17% 1	570
July	1st to 10th	Night	9% 1 14% 41% 30% 5%	555
	11th to 20th	Night	7% 2 18% 43% 27% 3	552
	21st to end	Night	4 1 16% 48% 28% 2	624
August	1st to 10th	Night	7% 2 12% 46% 30% 4	567
	11th to 20th	Night	7% 3 13% 43% 31% 4	564
	21st to end	Night	7% 2 15% 39% 33% 3	627
September	1st to 10th	Night	12% 4 16% 38% 27% 3	570
	11th to 20th	Night	9% 4 15% 37% 30% 4	670
	21st to end	Night	12% 5% 23% 34% 23% 3	760
October	1st to 10th	Night	13% 5% 25% 35% 20% 2	760
	11th to 20th	Night	19% 11% 32% 27% 11%	760
	21st to end	Night	24% 11% 32% 24% 8%	836
November	1st to 10th	Night	15% 10% 38% 27% 10% 1	749
	11th to 20th	Night	19% 14% 35% 26% 6%	760
	21st to end	Night	22% 12% 34% 26% 7%	798
December	1st to 10th	Night	23% 12% 35% 24% 5%	950
	11th to 20th	Night	24% 10% 33% 26% 7%	950
	21st to end	Night	28% 13% 33% 23% 3	1045

Page generated at 2024-10-31 02:39:23. Version ac07

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