Rawson Quarry
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rawson Quarry clear sky chart from 2005-11-06 to 2025-01-22.

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	26% 13% 3 5% 3 3 3 3 4 5% 33%	109235
	Night	29% 13% 3 5% 3 3 3 2 3 4 33%	108819
Transparency	Day	52% 6% 10% 16% 12% 4	108978
	Night	55% 5% 10% 15% 11% 4	108665
Seeing	Day	33% 9% 23% 23% 10% 2	14750
	Night	36% 6% 15% 25% 16% 2	23829

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	41% 28% 3 5% 3 2 2 2 2 3 9%	2619
	11th to 20th	Day	39% 16% 3 6% 3 3 2 2 3 3 19%	2620
	21st to end	Day	48% 15% 3 5% 3 2 3 2 3 3 13%	3003
February	1st to 10th	Day	38% 16% 3 6% 4 3 2 3 4 5% 16%	1710
	11th to 20th	Day	36% 21% 4 6% 4 3 2 2 2 3 18%	1665
	21st to end	Day	35% 24% 3 5% 3 2 3 2 3 3 18%	1503
March	1st to 10th	Day	26% 25% 5% 8% 4 3 4 2 3 5% 16%	3248
	11th to 20th	Day	27% 16% 3 5% 2 2 2 2 2 3 36%	3490
	21st to end	Day	34% 22% 4 7% 4 4 3 2 3 3 13%	3938
April	1st to 10th	Day	35% 19% 4 7% 4 3 3 3 4 4 15%	2280
	11th to 20th	Day	32% 17% 4 6% 4 3 3 3 4 4 22%	2249
	21st to end	Day	30% 17% 3 7% 4 4 3 4 4 5% 20%	2445
May	1st to 10th	Day	25% 16% 3 6% 3 3 3 2 4 5% 29%	4408
	11th to 20th	Day	17% 14% 3 5% 4 3 5% 4 5% 6% 33%	4377
	21st to end	Day	33% 14% 3 6% 4 4 4 3 4 4 21%	4813
June	1st to 10th	Day	30% 9% 2 6% 5% 4 4 4 4 5% 26%	2660
	11th to 20th	Day	29% 12% 3 7% 5% 4 4 4 5% 6% 22%	2660
	21st to end	Day	14% 8% 3 5% 4 4 4 3 5% 6% 45%	2660
July	1st to 10th	Day	7% 5% 2 3 2 2 2 2 3 5% 65%	4420
	11th to 20th	Day	6% 4 1 2 2 2 3 2 3 4 71%	4420
	21st to end	Day	9% 6% 1 3 2 2 2 2 4 6% 63%	4790
August	1st to 10th	Day	6% 5% 1 4 2 3 3 2 4 5% 63%	4194
	11th to 20th	Day	8% 8% 3 7% 4 3 4 4 5% 6% 48%	4026
	21st to end	Day	15% 7% 2 5% 3 3 3 3 4 6% 49%	4279
September	1st to 10th	Day	12% 5% 1 4 2 2 3 2 4 5% 58%	2280
	11th to 20th	Day	18% 8% 3 6% 4 4 4 2 4 7% 41%	2280
	21st to end	Day	21% 8% 3 5% 3 3 3 2 4 5% 43%	2008
October	1st to 10th	Day	21% 7% 1 4 2 2 3 3 4 5% 46%	3180
	11th to 20th	Day	27% 9% 3 7% 3 3 4 3 5% 6% 30%	3161
	21st to end	Day	39% 11% 2 6% 3 2 3 3 4 4 23%	3327
November	1st to 10th	Day	41% 14% 3 6% 3 4 3 2 4 5% 15%	1670
	11th to 20th	Day	45% 11% 2 5% 3 3 3 3 4 4 18%	1600
	21st to end	Day	36% 16% 2 6% 3 2 3 3 3 4 22%	1600
December	1st to 10th	Day	27% 12% 2 5% 3 2 3 3 3 4 36%	2620
	11th to 20th	Day	44% 18% 3 7% 4 2 2 2 3 4 12%	3028
	21st to end	Day	43% 19% 3 7% 3 3 3 2 3 3 11%	4004
January	1st to 10th	Night	42% 22% 2 5% 3 3 3 2 2 3 11%	4546
	11th to 20th	Night	38% 19% 3 5% 3 2 2 2 3 4 18%	4560
	21st to end	Night	47% 14% 3 5% 3 2 3 2 3 4 14%	4680
February	1st to 10th	Night	36% 18% 3 6% 4 3 3 3 4 4 18%	2470
	11th to 20th	Night	35% 17% 3 5% 3 3 3 2 3 3 23%	2402
	21st to end	Night	32% 23% 3 5% 2 3 3 2 4 5% 18%	1951
March	1st to 10th	Night	25% 24% 4 7% 4 3 3 3 4 5% 18%	3622
	11th to 20th	Night	26% 14% 2 4 2 2 2 2 3 4 39%	3490
	21st to end	Night	38% 22% 3 6% 4 3 3 2 3 3 13%	3715
April	1st to 10th	Night	32% 20% 3 6% 4 3 3 2 2 4 21%	1900
	11th to 20th	Night	27% 16% 3 6% 3 3 3 2 4 6% 27%	1879
	21st to end	Night	31% 13% 2 6% 4 4 4 3 3 6% 24%	1732
May	1st to 10th	Night	29% 15% 2 6% 2 2 2 2 3 3 35%	2550
	11th to 20th	Night	15% 9% 3 5% 3 4 3 3 3 4 47%	2516
	21st to end	Night	23% 12% 2 6% 3 4 4 4 5% 6% 30%	2762
June	1st to 10th	Night	27% 8% 3 6% 3 3 3 3 4 6% 34%	1520
	11th to 20th	Night	23% 11% 3 7% 4 3 3 3 4 5% 36%	1520
	21st to end	Night	13% 7% 1 4 3 3 3 3 4 5% 56%	1520
July	1st to 10th	Night	5% 2 1 2 2 2 1 1 2 3 78%	2540
	11th to 20th	Night	5% 3 1 3 2 2 1 2 2 3 76%	2540
	21st to end	Night	6% 2 1 2 1 2 2 1 3 4 76%	2761
August	1st to 10th	Night	4 3 2 3 2 2 2 1 3 5% 74%	2739
	11th to 20th	Night	8% 5% 2 4 4 4 4 3 4 6% 56%	2812
	21st to end	Night	15% 5% 1 3 2 2 2 2 4 5% 60%	3395
September	1st to 10th	Night	10% 4 1 3 2 2 3 3 3 5% 63%	1900
	11th to 20th	Night	19% 7% 2 5% 4 3 3 3 3 5% 47%	1900
	21st to end	Night	18% 8% 2 4 3 4 3 2 4 5% 48%	2170
October	1st to 10th	Night	18% 5% 2 4 3 3 3 2 4 7% 50%	3800
	11th to 20th	Night	25% 8% 3 5% 3 4 4 3 6% 6% 33%	3777
	21st to end	Night	39% 12% 2 5% 3 3 3 2 4 4 23%	4237
November	1st to 10th	Night	41% 13% 3 5% 3 3 2 3 3 4 19%	2625
	11th to 20th	Night	46% 12% 2 5% 3 2 3 2 3 5% 19%	2800
	21st to end	Night	35% 14% 2 5% 3 3 2 3 3 5% 25%	2800
December	1st to 10th	Night	26% 11% 3 5% 3 3 3 2 4 6% 36%	4560
	11th to 20th	Night	43% 18% 4 7% 3 3 2 2 3 4 12%	5176
	21st to end	Night	43% 20% 4 6% 3 3 2 2 2 2 12%	6952

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	82% 4 5% 6% 3 1	2619
	11th to 20th	Day	71% 4 7% 10% 5% 3	2620
	21st to end	Day	77% 3 5% 8% 5% 1	3003
February	1st to 10th	Day	71% 5% 9% 9% 6%	1710
	11th to 20th	Day	73% 4 6% 11% 4 2	1674
	21st to end	Day	71% 5% 8% 7% 7% 2	1503
March	1st to 10th	Day	68% 5% 10% 12% 4	3248
	11th to 20th	Day	55% 4 6% 25% 9%	3490
	21st to end	Day	74% 7% 9% 7% 3	3938
April	1st to 10th	Day	72% 5% 11% 9% 3	2280
	11th to 20th	Day	67% 5% 8% 10% 8% 2	2252
	21st to end	Day	65% 7% 9% 11% 6% 2	2445
May	1st to 10th	Day	56% 6% 11% 15% 12%	4408
	11th to 20th	Day	45% 8% 19% 19% 8% 1	4380
	21st to end	Day	63% 11% 14% 11% 1	4814
June	1st to 10th	Day	57% 8% 13% 16% 6%	2660
	11th to 20th	Day	60% 8% 15% 12% 5%	2660
	21st to end	Day	37% 8% 15% 26% 10% 4	2660
July	1st to 10th	Day	22% 5% 9% 17% 21% 28%	4351
	11th to 20th	Day	17% 4 6% 18% 37% 18%	4345
	21st to end	Day	22% 5% 10% 26% 32% 5%	4639
August	1st to 10th	Day	23% 5% 9% 25% 26% 12%	4178
	11th to 20th	Day	32% 7% 16% 29% 11% 5%	4065
	21st to end	Day	34% 6% 10% 23% 15% 12%	4278
September	1st to 10th	Day	28% 5% 11% 24% 19% 13%	2280
	11th to 20th	Day	44% 6% 11% 16% 14% 9%	2280
	21st to end	Day	42% 6% 13% 18% 14% 6%	2008
October	1st to 10th	Day	40% 4 6% 22% 25% 3	3180
	11th to 20th	Day	51% 6% 13% 15% 12% 2	3161
	21st to end	Day	62% 4 8% 16% 9% 1	3327
November	1st to 10th	Day	71% 5% 7% 12% 4 1	1670
	11th to 20th	Day	69% 6% 9% 9% 6% 2	1600
	21st to end	Day	67% 5% 6% 8% 13% 2	1600
December	1st to 10th	Day	52% 4 7% 13% 20% 3	2620
	11th to 20th	Day	77% 4 9% 7% 2	3028
	21st to end	Day	79% 4 7% 8% 2	4004
January	1st to 10th	Night	79% 3 6% 7% 4 1	4546
	11th to 20th	Night	70% 5% 6% 12% 4 2	4560
	21st to end	Night	75% 4 6% 9% 6% 1	4680
February	1st to 10th	Night	70% 6% 8% 9% 6% 1	2470
	11th to 20th	Night	66% 6% 8% 11% 6% 2	2404
	21st to end	Night	69% 4 8% 10% 7% 1	1951
March	1st to 10th	Night	67% 6% 10% 13% 3	3622
	11th to 20th	Night	50% 5% 10% 21% 12% 1	3490
	21st to end	Night	76% 6% 8% 8% 2	3715
April	1st to 10th	Night	69% 6% 11% 10% 5%	1900
	11th to 20th	Night	59% 8% 10% 12% 8% 3	1879
	21st to end	Night	62% 6% 12% 13% 5% 3	1732
May	1st to 10th	Night	55% 6% 9% 20% 9% 1	2550
	11th to 20th	Night	37% 9% 21% 25% 7% 2	2516
	21st to end	Night	54% 13% 20% 10% 3	2762
June	1st to 10th	Night	51% 8% 14% 20% 7%	1520
	11th to 20th	Night	52% 7% 17% 19% 5%	1520
	21st to end	Night	32% 6% 18% 30% 10% 5%	1520
July	1st to 10th	Night	14% 4 8% 23% 24% 26%	2500
	11th to 20th	Night	16% 3 8% 21% 35% 18%	2492
	21st to end	Night	12% 4 13% 29% 37% 6%	2674
August	1st to 10th	Night	15% 4 9% 33% 30% 8%	2731
	11th to 20th	Night	27% 10% 21% 27% 10% 6%	2839
	21st to end	Night	28% 6% 14% 26% 14% 12%	3395
September	1st to 10th	Night	23% 6% 13% 28% 19% 12%	1900
	11th to 20th	Night	40% 6% 12% 20% 11% 11%	1900
	21st to end	Night	38% 7% 13% 18% 15% 8%	2170
October	1st to 10th	Night	34% 5% 9% 25% 24% 3	3800
	11th to 20th	Night	49% 6% 13% 16% 14% 2	3777
	21st to end	Night	64% 4 7% 14% 9% 2	4237
November	1st to 10th	Night	68% 5% 6% 13% 7% 1	2625
	11th to 20th	Night	70% 5% 7% 8% 8% 2	2800
	21st to end	Night	62% 5% 7% 10% 13% 2	2800
December	1st to 10th	Night	49% 4 8% 14% 23% 1	4560
	11th to 20th	Night	77% 4 7% 7% 4	5176
	21st to end	Night	79% 4 8% 6% 2	6952

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	58% 12% 18% 10% 4	200
	11th to 20th	Day	48% 13% 24% 10% 6% 1	200
	21st to end	Day	54% 7% 15% 17% 7%	323
February	1st to 10th	Day	50% 9% 21% 15% 4 1	370
	11th to 20th	Day	51% 10% 21% 14% 4	365
	21st to end	Day	50% 9% 25% 13% 3	350
March	1st to 10th	Day	47% 10% 25% 13% 5%	460
	11th to 20th	Day	40% 12% 26% 15% 6% 2	460
	21st to end	Day	48% 11% 17% 19% 5% 1	506
April	1st to 10th	Day	47% 7% 24% 13% 6% 2	460
	11th to 20th	Day	41% 13% 24% 15% 6% 2	452
	21st to end	Day	40% 9% 25% 20% 5% 1	460
May	1st to 10th	Day	29% 13% 27% 22% 7% 2	463
	11th to 20th	Day	36% 11% 20% 21% 8% 4	488
	21st to end	Day	37% 7% 19% 23% 10% 4	529
June	1st to 10th	Day	32% 8% 19% 24% 14% 3	490
	11th to 20th	Day	30% 11% 29% 20% 8% 2	490
	21st to end	Day	12% 10% 31% 28% 15% 3	490
July	1st to 10th	Day	17% 8% 24% 35% 12% 3	486
	11th to 20th	Day	9% 8% 28% 35% 16% 4	484
	21st to end	Day	9% 6% 23% 38% 18% 6%	531
August	1st to 10th	Day	11% 5% 21% 37% 18% 7%	487
	11th to 20th	Day	8% 4 24% 38% 20% 6%	477
	21st to end	Day	15% 10% 25% 33% 14% 4	539
September	1st to 10th	Day	14% 5% 30% 33% 14% 3	490
	11th to 20th	Day	22% 8% 21% 31% 17% 1	490
	21st to end	Day	22% 8% 28% 29% 10% 2	490
October	1st to 10th	Day	28% 7% 24% 28% 11% 2	490
	11th to 20th	Day	33% 7% 23% 23% 11% 3	490
	21st to end	Day	42% 11% 22% 17% 6% 2	467
November	1st to 10th	Day	54% 8% 19% 12% 6% 1	253
	11th to 20th	Day	51% 12% 21% 11% 6% 1	200
	21st to end	Day	46% 10% 22% 20% 3	200
December	1st to 10th	Day	45% 9% 21% 20% 6% 1	200
	11th to 20th	Day	61% 10% 19% 9% 2	200
	21st to end	Day	55% 9% 20% 13% 3	220
January	1st to 10th	Night	53% 10% 20% 14% 3 1	800
	11th to 20th	Night	48% 8% 21% 18% 6%	800
	21st to end	Night	45% 9% 20% 18% 7% 1	840
February	1st to 10th	Night	46% 7% 19% 20% 6% 1	760
	11th to 20th	Night	48% 7% 15% 22% 7% 1	744
	21st to end	Night	49% 9% 15% 20% 7%	628
March	1st to 10th	Night	44% 8% 14% 23% 11% 1	760
	11th to 20th	Night	42% 8% 18% 21% 11% 1	760
	21st to end	Night	50% 6% 10% 23% 9% 2	836
April	1st to 10th	Night	44% 6% 12% 23% 13% 1	760
	11th to 20th	Night	37% 7% 19% 21% 14% 3	751
	21st to end	Night	40% 6% 13% 27% 14% 1	592
May	1st to 10th	Night	29% 4 18% 26% 20% 2	390
	11th to 20th	Night	25% 4 12% 28% 28% 3	374
	21st to end	Night	26% 5% 11% 30% 25% 3	411
June	1st to 10th	Night	31% 4 11% 28% 24% 3	380
	11th to 20th	Night	27% 6% 14% 33% 20% 1	380
	21st to end	Night	14% 4 15% 34% 31% 1	380
July	1st to 10th	Night	9% 2 8% 38% 41% 3	370
	11th to 20th	Night	8% 1 9% 43% 35% 3	368
	21st to end	Night	4 2 9% 40% 41% 4	416
August	1st to 10th	Night	7% 1 5% 32% 47% 7%	497
	11th to 20th	Night	9% 1 6% 32% 43% 9%	564
	21st to end	Night	12% 3 11% 40% 30% 4	772
September	1st to 10th	Night	13% 3 15% 36% 29% 4	760
	11th to 20th	Night	20% 3 11% 32% 30% 5%	760
	21st to end	Night	21% 4 15% 33% 24% 2	760
October	1st to 10th	Night	25% 4 16% 31% 19% 3	760
	11th to 20th	Night	32% 5% 14% 29% 17% 3	760
	21st to end	Night	41% 6% 19% 24% 9% 2	836
November	1st to 10th	Night	47% 5% 17% 22% 8%	780
	11th to 20th	Night	53% 7% 18% 18% 4 1	800
	21st to end	Night	43% 8% 23% 22% 4	800
December	1st to 10th	Night	41% 9% 24% 18% 7% 1	800
	11th to 20th	Night	54% 8% 18% 18% 3	800
	21st to end	Night	57% 9% 16% 14% 3	880

Page generated at 2025-01-19 00:06:48. Version ac07

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