Hawkesbury
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hawkesbury clear sky chart from 2005-11-06 to 2026-07-01.

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	17% 11% 4 8% 5% 5% 5% 4 5% 7% 31%	138113
	Night	17% 12% 4 9% 5% 4 4 3 5% 6% 30%	134186
Transparency	Day	34% 37% 8% 14% 6% 1	141545
	Night	36% 36% 8% 12% 7% 1	138843
Seeing	Day	25% 18% 30% 18% 7% 2	16551
	Night	24% 14% 30% 24% 8% 1	25578

By Month

Percentage Cloud Cover NE (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% 19% 6% 13% 7% 5% 4 3 4 4 19%	4661
	11th to 20th	Day	13% 20% 7% 14% 6% 4 4 3 4 5% 19%	4650
	21st to end	Day	9% 17% 7% 14% 8% 6% 6% 4 4 4 21%	5124
February	1st to 10th	Day	13% 16% 5% 12% 7% 4 4 3 4 6% 26%	1890
	11th to 20th	Day	12% 17% 5% 11% 7% 4 4 3 6% 6% 25%	1906
	21st to end	Day	18% 16% 5% 10% 7% 4 5% 3 5% 4 23%	1730
March	1st to 10th	Day	19% 14% 5% 11% 6% 4 4 3 4 5% 24%	4576
	11th to 20th	Day	12% 14% 4 10% 5% 5% 5% 3 6% 6% 29%	4920
	21st to end	Day	20% 10% 3 8% 5% 5% 4 3 4 5% 33%	6008
April	1st to 10th	Day	21% 13% 4 7% 4 4 4 3 4 5% 32%	2520
	11th to 20th	Day	22% 11% 3 6% 5% 4 4 3 4 5% 34%	2494
	21st to end	Day	23% 10% 3 7% 5% 3 4 4 5% 6% 31%	2666
May	1st to 10th	Day	24% 9% 3 8% 5% 5% 5% 4 6% 7% 23%	8237
	11th to 20th	Day	19% 9% 3 8% 5% 4 4 4 5% 7% 32%	8221
	21st to end	Day	21% 10% 3 6% 4 4 4 4 5% 7% 33%	9060
June	1st to 10th	Day	22% 8% 3 7% 5% 5% 4 4 5% 8% 30%	2940
	11th to 20th	Day	16% 7% 2 6% 5% 5% 5% 5% 6% 8% 35%	2940
	21st to end	Day	21% 6% 3 7% 5% 5% 5% 4 6% 7% 30%	2940
July	1st to 10th	Day	14% 6% 3 8% 7% 6% 5% 5% 6% 9% 31%	6360
	11th to 20th	Day	13% 6% 2 7% 5% 5% 5% 4 6% 8% 39%	6360
	21st to end	Day	10% 5% 2 5% 4 4 4 3 6% 9% 47%	6926
August	1st to 10th	Day	15% 6% 3 7% 5% 5% 6% 5% 6% 8% 34%	4563
	11th to 20th	Day	16% 7% 3 6% 4 4 5% 4 7% 8% 38%	4100
	21st to end	Day	16% 6% 2 6% 4 5% 5% 4 6% 8% 38%	4312
September	1st to 10th	Day	15% 5% 2 5% 4 4 5% 4 6% 8% 42%	2400
	11th to 20th	Day	14% 5% 2 5% 3 3 4 3 5% 7% 50%	2351
	21st to end	Day	20% 6% 3 5% 3 3 4 3 6% 7% 42%	2200
October	1st to 10th	Day	21% 7% 2 6% 4 4 3 3 5% 6% 37%	2010
	11th to 20th	Day	22% 10% 3 8% 5% 5% 4 3 5% 6% 29%	1995
	21st to end	Day	24% 11% 4 8% 5% 4 4 3 5% 6% 27%	1980
November	1st to 10th	Day	18% 11% 4 8% 5% 4 5% 4 5% 7% 31%	1851
	11th to 20th	Day	19% 12% 5% 9% 5% 6% 4 4 5% 6% 26%	1748
	21st to end	Day	23% 16% 4 8% 6% 4 5% 3 4 5% 22%	1680
December	1st to 10th	Day	21% 22% 5% 9% 4 4 5% 4 5% 6% 15%	2680
	11th to 20th	Day	19% 18% 6% 10% 4 4 4 3 4 4 25%	3066
	21st to end	Day	22% 17% 5% 9% 4 4 4 3 4 4 22%	4048
January	1st to 10th	Night	15% 20% 7% 14% 5% 4 3 3 4 4 20%	8234
	11th to 20th	Night	12% 20% 8% 18% 7% 4 4 3 4 4 16%	8235
	21st to end	Night	10% 16% 6% 12% 7% 6% 5% 3 4 6% 23%	9039
February	1st to 10th	Night	14% 15% 5% 11% 6% 5% 5% 4 5% 6% 25%	2730
	11th to 20th	Night	14% 12% 5% 12% 8% 5% 4 3 5% 5% 28%	2600
	21st to end	Night	15% 15% 5% 10% 6% 4 4 4 4 5% 29%	2076
March	1st to 10th	Night	22% 14% 4 9% 5% 4 3 3 4 4 28%	5484
	11th to 20th	Night	13% 15% 4 7% 4 5% 5% 4 6% 8% 30%	5244
	21st to end	Night	18% 12% 4 8% 6% 5% 5% 3 4 5% 32%	5152
April	1st to 10th	Night	22% 10% 4 6% 5% 4 4 3 4 6% 31%	2100
	11th to 20th	Night	20% 9% 2 8% 5% 4 4 3 4 6% 34%	2075
	21st to end	Night	22% 9% 3 6% 4 3 4 3 4 5% 36%	1973
May	1st to 10th	Night	20% 9% 4 8% 6% 5% 6% 4 6% 8% 25%	4660
	11th to 20th	Night	21% 7% 2 7% 4 4 5% 4 5% 7% 34%	4639
	21st to end	Night	20% 11% 3 7% 5% 4 4 3 5% 7% 31%	5114
June	1st to 10th	Night	19% 7% 3 7% 4 4 5% 5% 6% 8% 32%	1680
	11th to 20th	Night	16% 7% 3 7% 4 3 4 4 5% 7% 39%	1680
	21st to end	Night	19% 7% 2 6% 5% 4 4 5% 5% 7% 35%	1680
July	1st to 10th	Night	15% 7% 3 8% 5% 5% 5% 5% 7% 9% 32%	3600
	11th to 20th	Night	14% 7% 3 7% 4 4 4 4 5% 8% 42%	3600
	21st to end	Night	11% 5% 2 5% 4 4 4 4 6% 7% 48%	3926
August	1st to 10th	Night	15% 7% 2 7% 4 4 5% 5% 6% 7% 39%	2586
	11th to 20th	Night	17% 6% 2 5% 4 4 4 3 6% 6% 42%	2900
	21st to end	Night	16% 5% 2 6% 5% 4 5% 3 5% 7% 41%	3586
September	1st to 10th	Night	12% 5% 2 6% 4 5% 4 3 5% 8% 45%	2000
	11th to 20th	Night	15% 5% 2 4 3 3 3 3 5% 7% 50%	2048
	21st to end	Night	18% 6% 2 5% 4 4 4 4 5% 5% 44%	2200
October	1st to 10th	Night	19% 6% 2 6% 4 5% 4 3 5% 6% 40%	2389
	11th to 20th	Night	21% 9% 2 8% 5% 4 4 3 4 6% 34%	2404
	21st to end	Night	24% 9% 4 8% 6% 5% 3 3 5% 5% 30%	2860
November	1st to 10th	Night	21% 10% 3 7% 5% 4 4 3 5% 6% 31%	2667
	11th to 20th	Night	18% 11% 4 9% 6% 4 4 3 4 5% 31%	2867
	21st to end	Night	21% 15% 4 10% 5% 4 5% 3 4 5% 24%	2940
December	1st to 10th	Night	18% 18% 6% 11% 7% 5% 5% 4 5% 5% 18%	4720
	11th to 20th	Night	24% 16% 4 10% 5% 4 3 2 3 4 25%	5348
	21st to end	Night	25% 18% 4 9% 4 3 3 2 4 4 24%	7150

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	52% 25% 8% 12% 3	4662
	11th to 20th	Day	54% 23% 6% 9% 7% 1	4680
	21st to end	Day	53% 26% 7% 6% 8% 1	5124
February	1st to 10th	Day	25% 59% 3 8% 3 1	1890
	11th to 20th	Day	24% 59% 3 8% 5%	1915
	21st to end	Day	26% 60% 4 4 5% 1	1730
March	1st to 10th	Day	46% 30% 5% 7% 9% 3	4579
	11th to 20th	Day	38% 32% 11% 10% 8% 1	4920
	21st to end	Day	39% 30% 4 11% 14% 1	6008
April	1st to 10th	Day	23% 59% 4 7% 6% 1	2520
	11th to 20th	Day	23% 59% 3 9% 6% 1	2494
	21st to end	Day	23% 59% 4 8% 6%	2666
May	1st to 10th	Day	46% 26% 7% 14% 6%	8249
	11th to 20th	Day	40% 27% 12% 16% 6%	8225
	21st to end	Day	40% 26% 9% 17% 8%	9061
June	1st to 10th	Day	21% 59% 3 10% 6% 1	2940
	11th to 20th	Day	20% 60% 4 9% 6% 1	2940
	21st to end	Day	20% 59% 5% 10% 5% 1	2940
July	1st to 10th	Day	37% 29% 10% 19% 5%	6290
	11th to 20th	Day	30% 28% 10% 24% 8%	6285
	21st to end	Day	23% 27% 12% 30% 8%	6728
August	1st to 10th	Day	30% 38% 11% 15% 6%	4549
	11th to 20th	Day	29% 38% 9% 20% 3	4141
	21st to end	Day	26% 39% 12% 15% 8%	4312
September	1st to 10th	Day	16% 58% 6% 13% 6%	2400
	11th to 20th	Day	13% 58% 6% 16% 6% 1	2351
	21st to end	Day	14% 58% 7% 13% 8% 1	2200
October	1st to 10th	Day	29% 37% 9% 20% 6%	3270
	11th to 20th	Day	25% 39% 12% 19% 4 1	3223
	21st to end	Day	28% 38% 15% 15% 5%	3180
November	1st to 10th	Day	29% 54% 6% 7% 3 1	1851
	11th to 20th	Day	25% 56% 5% 9% 5%	1748
	21st to end	Day	31% 56% 6% 4 3	1680
December	1st to 10th	Day	45% 37% 6% 10% 1	2680
	11th to 20th	Day	46% 31% 7% 10% 6%	3066
	21st to end	Day	47% 28% 7% 12% 6%	4048
January	1st to 10th	Night	54% 23% 9% 10% 4 1	8234
	11th to 20th	Night	57% 24% 8% 7% 4	8280
	21st to end	Night	50% 24% 7% 9% 10%	9039
February	1st to 10th	Night	25% 59% 5% 8% 3	2730
	11th to 20th	Night	24% 58% 4 9% 5%	2602
	21st to end	Night	23% 59% 4 7% 7%	2076
March	1st to 10th	Night	43% 29% 6% 8% 10% 3	5494
	11th to 20th	Night	35% 32% 11% 11% 7% 3	5245
	21st to end	Night	41% 30% 5% 15% 8% 1	5152
April	1st to 10th	Night	24% 59% 3 8% 6%	2100
	11th to 20th	Night	23% 60% 3 8% 6%	2075
	21st to end	Night	21% 59% 4 8% 7% 1	1973
May	1st to 10th	Night	44% 28% 10% 13% 5%	4666
	11th to 20th	Night	40% 28% 9% 17% 7%	4640
	21st to end	Night	42% 26% 7% 14% 11%	5115
June	1st to 10th	Night	20% 60% 3 9% 8% 1	1680
	11th to 20th	Night	18% 60% 4 10% 8% 1	1680
	21st to end	Night	20% 58% 5% 10% 6% 1	1680
July	1st to 10th	Night	37% 29% 14% 14% 6%	3560
	11th to 20th	Night	30% 28% 13% 24% 5%	3552
	21st to end	Night	25% 27% 11% 25% 11%	3809
August	1st to 10th	Night	28% 39% 9% 19% 5%	2576
	11th to 20th	Night	29% 38% 12% 17% 4	2925
	21st to end	Night	28% 38% 11% 14% 8% 1	3586
September	1st to 10th	Night	14% 59% 6% 13% 8%	2000
	11th to 20th	Night	13% 58% 7% 16% 5% 1	2048
	21st to end	Night	15% 57% 6% 13% 8%	2200
October	1st to 10th	Night	25% 37% 12% 18% 7% 1	3909
	11th to 20th	Night	24% 37% 10% 20% 8%	3915
	21st to end	Night	29% 36% 14% 12% 8%	4610
November	1st to 10th	Night	28% 54% 7% 8% 3	2667
	11th to 20th	Night	25% 55% 5% 10% 4	2867
	21st to end	Night	29% 56% 5% 7% 3	2940
December	1st to 10th	Night	44% 36% 9% 9% 2	4720
	11th to 20th	Night	47% 31% 4 9% 9%	5348
	21st to end	Night	48% 27% 4 10% 11%	7150

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	25% 26% 31% 15% 3	220
	11th to 20th	Day	34% 20% 34% 8% 5%	220
	21st to end	Day	22% 21% 36% 16% 5%	242
February	1st to 10th	Day	32% 27% 32% 8% 1	330
	11th to 20th	Day	24% 29% 38% 8%	393
	21st to end	Day	30% 23% 32% 13% 2	446
March	1st to 10th	Day	28% 24% 31% 15% 2	540
	11th to 20th	Day	31% 22% 29% 13% 4 1	540
	21st to end	Day	32% 22% 26% 14% 5% 1	594
April	1st to 10th	Day	34% 21% 27% 14% 4 1	540
	11th to 20th	Day	36% 19% 23% 15% 6% 1	532
	21st to end	Day	34% 20% 31% 10% 5% 1	540
May	1st to 10th	Day	28% 20% 32% 14% 5% 1	543
	11th to 20th	Day	22% 21% 30% 20% 6% 1	567
	21st to end	Day	25% 19% 30% 19% 6% 1	617
June	1st to 10th	Day	23% 16% 34% 19% 8% 1	570
	11th to 20th	Day	18% 18% 34% 21% 9% 1	570
	21st to end	Day	24% 16% 32% 19% 7% 2	570
July	1st to 10th	Day	14% 13% 34% 25% 11% 2	525
	11th to 20th	Day	17% 12% 35% 25% 10% 1	524
	21st to end	Day	16% 10% 35% 27% 10% 1	576
August	1st to 10th	Day	16% 8% 28% 35% 10% 3	526
	11th to 20th	Day	16% 8% 26% 29% 15% 5%	519
	21st to end	Day	17% 13% 28% 22% 14% 5%	583
September	1st to 10th	Day	19% 10% 32% 23% 13% 4	530
	11th to 20th	Day	12% 11% 25% 23% 21% 8%	530
	21st to end	Day	21% 14% 26% 23% 13% 4	530
October	1st to 10th	Day	24% 17% 23% 22% 12% 2	530
	11th to 20th	Day	26% 21% 28% 17% 7% 1	527
	21st to end	Day	33% 15% 31% 17% 4	462
November	1st to 10th	Day	32% 16% 26% 21% 4	425
	11th to 20th	Day	27% 22% 32% 14% 4	288
	21st to end	Day	35% 21% 29% 13% 2	220
December	1st to 10th	Day	34% 14% 32% 15% 4	220
	11th to 20th	Day	30% 26% 33% 10% 2	220
	21st to end	Day	33% 17% 33% 12% 4 1	242
January	1st to 10th	Night	28% 15% 36% 18% 3	840
	11th to 20th	Night	29% 20% 29% 17% 5%	840
	21st to end	Night	19% 17% 35% 22% 5% 1	924
February	1st to 10th	Night	21% 20% 33% 22% 4	840
	11th to 20th	Night	23% 19% 37% 16% 4	823
	21st to end	Night	24% 18% 33% 22% 3	692
March	1st to 10th	Night	26% 17% 34% 19% 4	840
	11th to 20th	Night	26% 20% 32% 18% 4	840
	21st to end	Night	25% 16% 30% 22% 5%	924
April	1st to 10th	Night	31% 14% 30% 22% 4	840
	11th to 20th	Night	26% 16% 32% 20% 6%	831
	21st to end	Night	29% 14% 31% 19% 7%	713
May	1st to 10th	Night	23% 14% 31% 24% 5% 2	420
	11th to 20th	Night	21% 12% 31% 27% 8%	414
	21st to end	Night	19% 11% 36% 24% 9%	455
June	1st to 10th	Night	21% 8% 30% 31% 9%	420
	11th to 20th	Night	20% 9% 28% 31% 10% 1	420
	21st to end	Night	21% 6% 28% 32% 12%	420
July	1st to 10th	Night	11% 9% 26% 37% 15% 1	390
	11th to 20th	Night	13% 6% 24% 40% 16% 1	388
	21st to end	Night	14% 5% 27% 39% 15% 1	438
August	1st to 10th	Night	14% 4 19% 44% 18% 1	398
	11th to 20th	Night	14% 3 23% 34% 25% 2	604
	21st to end	Night	16% 7% 23% 35% 17% 2	880
September	1st to 10th	Night	15% 6% 29% 34% 15% 1	800
	11th to 20th	Night	17% 8% 19% 32% 23% 2	800
	21st to end	Night	20% 10% 24% 29% 15% 2	800
October	1st to 10th	Night	22% 10% 28% 28% 12%	800
	11th to 20th	Night	26% 13% 29% 25% 7% 1	800
	21st to end	Night	28% 14% 29% 24% 4	880
November	1st to 10th	Night	27% 15% 27% 24% 6% 1	820
	11th to 20th	Night	25% 17% 32% 17% 8%	840
	21st to end	Night	31% 17% 29% 18% 5%	840
December	1st to 10th	Night	29% 18% 31% 19% 4	840
	11th to 20th	Night	29% 21% 28% 16% 4 1	840
	21st to end	Night	35% 17% 29% 15% 4	924

Page generated at 2026-06-28 02:10:42. Version ac07

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