Clearing off Thompson Road
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Clearing off Thompson Road clear sky chart from 2005-11-06 to 2024-12-02.

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	16% 12% 4 8% 5% 4 4 3 5% 7% 31%	102308
	Night	16% 13% 5% 9% 5% 4 4 3 5% 6% 30%	97298
Transparency	Day	54% 3 11% 22% 10% 1	105904
	Night	55% 3 11% 20% 10% 1	101792
Seeing	Day	25% 13% 31% 20% 9% 3	14865
	Night	24% 12% 29% 25% 10% 1	23748

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% 23% 9% 16% 5% 3 2 1 3 3 19%	2517
	11th to 20th	Day	11% 19% 9% 16% 8% 7% 6% 3 4 4 13%	2598
	21st to end	Day	18% 22% 8% 14% 5% 4 3 2 3 3 17%	3124
February	1st to 10th	Day	12% 20% 7% 17% 9% 5% 3 2 3 3 18%	1710
	11th to 20th	Day	13% 16% 8% 13% 7% 4 4 3 3 5% 23%	1663
	21st to end	Day	16% 19% 6% 12% 7% 4 4 2 4 4 20%	1437
March	1st to 10th	Day	18% 17% 5% 10% 5% 4 3 3 5% 5% 26%	3422
	11th to 20th	Day	10% 19% 7% 11% 6% 4 5% 4 5% 6% 24%	3480
	21st to end	Day	14% 11% 4 8% 6% 4 4 3 4 5% 39%	3815
April	1st to 10th	Day	21% 14% 4 8% 4 4 4 3 4 6% 28%	2271
	11th to 20th	Day	23% 12% 2 5% 4 4 3 3 4 5% 35%	2327
	21st to end	Day	21% 13% 3 7% 4 4 4 2 5% 5% 32%	2470
May	1st to 10th	Day	19% 8% 3 7% 5% 5% 5% 4 5% 7% 32%	4222
	11th to 20th	Day	15% 10% 3 6% 5% 4 4 4 6% 9% 34%	4398
	21st to end	Day	16% 7% 2 6% 5% 4 4 3 5% 7% 40%	4837
June	1st to 10th	Day	21% 8% 3 7% 5% 4 5% 3 5% 8% 32%	2660
	11th to 20th	Day	15% 7% 2 6% 5% 5% 5% 4 7% 8% 36%	2765
	21st to end	Day	18% 8% 3 7% 5% 4 4 4 6% 7% 34%	2850
July	1st to 10th	Day	13% 7% 2 7% 5% 5% 6% 5% 7% 10% 34%	4706
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 6% 7% 42%	4440
	21st to end	Day	10% 6% 2 6% 4 4 4 4 6% 8% 45%	4673
August	1st to 10th	Day	15% 8% 3 7% 5% 5% 5% 4 6% 8% 33%	4104
	11th to 20th	Day	16% 8% 3 7% 4 4 5% 4 7% 8% 34%	4044
	21st to end	Day	9% 5% 2 5% 5% 5% 5% 4 8% 9% 42%	4352
September	1st to 10th	Day	17% 6% 2 7% 5% 5% 4 4 5% 9% 37%	2280
	11th to 20th	Day	14% 6% 2 6% 5% 4 4 4 5% 8% 43%	2206
	21st to end	Day	18% 10% 2 7% 4 5% 4 3 4 6% 36%	2028
October	1st to 10th	Day	21% 9% 3 8% 5% 3 4 3 5% 7% 32%	1900
	11th to 20th	Day	25% 12% 3 8% 5% 6% 5% 4 4 6% 23%	1900
	21st to end	Day	29% 13% 4 8% 5% 4 4 3 4 5% 21%	2090
November	1st to 10th	Day	19% 13% 5% 7% 4 3 4 3 6% 6% 28%	1613
	11th to 20th	Day	17% 17% 6% 10% 6% 4 4 4 5% 5% 23%	1600
	21st to end	Day	20% 23% 6% 9% 6% 5% 3 4 4 5% 15%	1600
December	1st to 10th	Day	18% 27% 6% 11% 4 4 2 3 4 5% 16%	1528
	11th to 20th	Day	18% 21% 8% 13% 4 4 3 2 3 3 20%	1906
	21st to end	Day	24% 24% 6% 12% 5% 4 3 2 3 4 13%	2772
January	1st to 10th	Night	17% 21% 10% 16% 6% 4 3 2 3 4 14%	4429
	11th to 20th	Night	13% 17% 7% 20% 8% 6% 5% 3 4 4 14%	4344
	21st to end	Night	18% 18% 8% 14% 6% 7% 4 3 4 3 16%	4532
February	1st to 10th	Night	13% 18% 7% 14% 9% 6% 4 4 5% 5% 18%	2470
	11th to 20th	Night	12% 17% 8% 12% 6% 5% 4 4 4 4 25%	2403
	21st to end	Night	15% 17% 5% 11% 8% 4 5% 3 4 4 23%	2017
March	1st to 10th	Night	16% 14% 5% 10% 5% 4 3 3 5% 6% 29%	3413
	11th to 20th	Night	11% 18% 7% 9% 6% 4 4 3 5% 5% 27%	3479
	21st to end	Night	14% 9% 5% 7% 5% 5% 4 4 6% 6% 35%	3817
April	1st to 10th	Night	21% 14% 5% 6% 4 5% 4 3 4 5% 29%	1908
	11th to 20th	Night	19% 10% 2 7% 4 4 4 3 6% 6% 35%	1818
	21st to end	Night	20% 9% 3 8% 5% 5% 4 4 5% 6% 30%	1710
May	1st to 10th	Night	18% 7% 2 7% 5% 4 5% 2 5% 7% 37%	2719
	11th to 20th	Night	15% 9% 2 6% 3 4 4 4 6% 8% 38%	2495
	21st to end	Night	12% 7% 3 5% 4 4 5% 4 5% 9% 43%	2738
June	1st to 10th	Night	16% 9% 2 6% 6% 5% 5% 4 5% 7% 35%	1520
	11th to 20th	Night	14% 7% 2 6% 4 4 4 3 5% 9% 42%	1407
	21st to end	Night	16% 7% 2 8% 4 5% 4 4 6% 8% 37%	1330
July	1st to 10th	Night	9% 6% 3 9% 5% 5% 5% 4 5% 7% 41%	2258
	11th to 20th	Night	16% 5% 2 5% 4 4 3 3 5% 6% 45%	2520
	21st to end	Night	10% 6% 2 6% 4 3 4 3 6% 7% 50%	2863
August	1st to 10th	Night	12% 5% 2 5% 4 4 4 4 6% 7% 47%	2825
	11th to 20th	Night	15% 7% 3 6% 4 4 4 3 5% 7% 42%	2785
	21st to end	Night	14% 5% 2 5% 3 4 4 4 5% 7% 48%	3270
September	1st to 10th	Night	12% 6% 2 7% 4 4 4 4 6% 7% 44%	1900
	11th to 20th	Night	14% 5% 2 5% 4 4 3 3 5% 6% 50%	1971
	21st to end	Night	19% 6% 3 7% 4 3 4 3 4 6% 41%	2152
October	1st to 10th	Night	19% 8% 3 7% 4 4 5% 3 5% 6% 37%	2280
	11th to 20th	Night	23% 12% 3 9% 4 4 4 3 5% 6% 27%	2280
	21st to end	Night	24% 15% 4 8% 5% 4 4 3 4 5% 24%	2508
November	1st to 10th	Night	20% 13% 4 8% 4 3 4 3 4 6% 32%	2679
	11th to 20th	Night	17% 16% 4 8% 5% 4 4 3 6% 6% 26%	2800
	21st to end	Night	22% 18% 5% 10% 6% 5% 4 4 4 4 18%	2800
December	1st to 10th	Night	20% 23% 7% 11% 5% 5% 4 4 4 4 14%	2686
	11th to 20th	Night	18% 22% 7% 13% 6% 3 3 3 4 4 18%	3288
	21st to end	Night	25% 22% 7% 12% 5% 4 3 2 3 4 12%	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	73% 1 9% 10% 7%	2518
	11th to 20th	Day	76% 2 6% 9% 6% 1	2598
	21st to end	Day	75% 2 6% 10% 7% 1	3124
February	1st to 10th	Day	72% 2 7% 14% 4 1	1710
	11th to 20th	Day	64% 3 8% 14% 9% 2	1672
	21st to end	Day	69% 2 7% 14% 8% 1	1437
March	1st to 10th	Day	61% 2 13% 12% 11% 1	3425
	11th to 20th	Day	62% 3 10% 16% 8% 1	3480
	21st to end	Day	48% 3 8% 23% 15% 3	3815
April	1st to 10th	Day	58% 2 8% 19% 10% 2	2271
	11th to 20th	Day	54% 2 7% 22% 14% 1	2327
	21st to end	Day	56% 2 7% 20% 11% 3	2470
May	1st to 10th	Day	52% 3 8% 24% 12% 1	4234
	11th to 20th	Day	49% 2 11% 27% 10% 1	4402
	21st to end	Day	44% 3 13% 21% 16% 3	4837
June	1st to 10th	Day	52% 3 9% 22% 13%	2660
	11th to 20th	Day	45% 5% 11% 24% 14% 2	2765
	21st to end	Day	49% 4 13% 23% 11% 1	2850
July	1st to 10th	Day	43% 6% 15% 24% 11% 1	4633
	11th to 20th	Day	39% 5% 15% 32% 10%	4365
	21st to end	Day	37% 5% 11% 33% 15%	4524
August	1st to 10th	Day	48% 4 13% 25% 9% 1	4091
	11th to 20th	Day	46% 4 15% 27% 8%	4083
	21st to end	Day	36% 5% 12% 37% 10% 1	4352
September	1st to 10th	Day	45% 4 12% 27% 11% 1	2280
	11th to 20th	Day	39% 4 14% 29% 13% 1	2206
	21st to end	Day	51% 4 11% 24% 10%	2028
October	1st to 10th	Day	48% 4 12% 26% 10% 1	3160
	11th to 20th	Day	54% 4 11% 21% 9% 1	3140
	21st to end	Day	61% 4 12% 17% 5%	3428
November	1st to 10th	Day	56% 3 14% 21% 6%	1613
	11th to 20th	Day	63% 3 11% 15% 7% 1	1600
	21st to end	Day	72% 3 10% 10% 4 1	1600
December	1st to 10th	Day	73% 3 7% 13% 4 1	1528
	11th to 20th	Day	71% 3 6% 11% 8% 1	1906
	21st to end	Day	77% 1 7% 11% 4	2772
January	1st to 10th	Night	77% 2 7% 10% 4	4429
	11th to 20th	Night	76% 1 8% 10% 4 1	4344
	21st to end	Night	74% 2 8% 9% 6% 1	4532
February	1st to 10th	Night	69% 4 8% 14% 5% 1	2470
	11th to 20th	Night	63% 3 8% 17% 8%	2405
	21st to end	Night	65% 2 8% 18% 7% 1	2017
March	1st to 10th	Night	58% 2 10% 17% 11% 1	3423
	11th to 20th	Night	59% 2 13% 17% 7% 1	3480
	21st to end	Night	49% 2 8% 25% 15% 2	3817
April	1st to 10th	Night	58% 2 7% 19% 11% 2	1908
	11th to 20th	Night	50% 2 8% 24% 15% 1	1818
	21st to end	Night	53% 4 8% 17% 16% 2	1710
May	1st to 10th	Night	47% 3 11% 23% 15% 1	2726
	11th to 20th	Night	45% 2 12% 26% 12% 1	2496
	21st to end	Night	39% 3 12% 27% 18% 2	2739
June	1st to 10th	Night	47% 4 11% 22% 14% 2	1520
	11th to 20th	Night	40% 3 12% 27% 18% 1	1407
	21st to end	Night	45% 4 14% 24% 12% 1	1330
July	1st to 10th	Night	40% 6% 13% 24% 15% 2	2222
	11th to 20th	Night	39% 4 10% 34% 12%	2472
	21st to end	Night	33% 5% 11% 35% 15% 1	2772
August	1st to 10th	Night	36% 4 16% 26% 16% 1	2814
	11th to 20th	Night	41% 5% 17% 25% 11% 1	2812
	21st to end	Night	35% 4 12% 36% 12% 1	3270
September	1st to 10th	Night	39% 4 15% 28% 13% 1	1900
	11th to 20th	Night	35% 3 14% 33% 14%	1971
	21st to end	Night	45% 3 12% 28% 11%	2152
October	1st to 10th	Night	39% 4 10% 29% 19%	3800
	11th to 20th	Night	49% 4 14% 24% 9%	3779
	21st to end	Night	56% 4 15% 18% 7%	4120
November	1st to 10th	Night	54% 3 12% 23% 8%	2679
	11th to 20th	Night	58% 4 12% 17% 8% 1	2800
	21st to end	Night	69% 3 10% 13% 4	2800
December	1st to 10th	Night	74% 3 8% 11% 4	2686
	11th to 20th	Night	71% 3 8% 12% 6%	3288
	21st to end	Night	79% 2 6% 10% 3	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	27% 22% 30% 14% 5% 1	180
	11th to 20th	Day	30% 16% 36% 12% 4 1	204
	21st to end	Day	29% 15% 35% 14% 6%	297
February	1st to 10th	Day	31% 24% 33% 9% 3	270
	11th to 20th	Day	29% 23% 39% 9% 1	270
	21st to end	Day	39% 23% 31% 7%	249
March	1st to 10th	Day	27% 18% 38% 15% 2	460
	11th to 20th	Day	24% 20% 35% 16% 4 1	460
	21st to end	Day	33% 15% 31% 15% 5% 1	506
April	1st to 10th	Day	30% 18% 30% 15% 7% 1	460
	11th to 20th	Day	37% 16% 23% 13% 8% 3	452
	21st to end	Day	33% 15% 32% 13% 5% 2	460
May	1st to 10th	Day	29% 12% 30% 20% 6% 3	463
	11th to 20th	Day	22% 14% 31% 18% 12% 3	487
	21st to end	Day	22% 13% 31% 22% 10% 3	529
June	1st to 10th	Day	24% 11% 32% 26% 6% 1	490
	11th to 20th	Day	18% 11% 33% 24% 11% 3	595
	21st to end	Day	22% 11% 34% 22% 9% 2	680
July	1st to 10th	Day	14% 7% 35% 30% 10% 3	644
	11th to 20th	Day	17% 9% 27% 28% 13% 5%	484
	21st to end	Day	14% 9% 29% 32% 11% 4	532
August	1st to 10th	Day	18% 5% 26% 31% 14% 6%	486
	11th to 20th	Day	16% 6% 25% 29% 17% 8%	479
	21st to end	Day	16% 7% 31% 25% 15% 6%	539
September	1st to 10th	Day	18% 10% 30% 22% 14% 7%	490
	11th to 20th	Day	15% 7% 25% 22% 21% 9%	490
	21st to end	Day	23% 10% 27% 26% 12% 4	490
October	1st to 10th	Day	28% 13% 25% 17% 13% 3	490
	11th to 20th	Day	30% 16% 33% 15% 5% 1	490
	21st to end	Day	38% 15% 28% 15% 4	539
November	1st to 10th	Day	37% 15% 31% 13% 5%	240
	11th to 20th	Day	31% 20% 35% 9% 5% 1	200
	21st to end	Day	34% 21% 36% 8% 2	200
December	1st to 10th	Day	34% 19% 29% 16% 2	182
	11th to 20th	Day	39% 21% 24% 13% 2 1	180
	21st to end	Day	39% 22% 26% 10% 3 1	198
January	1st to 10th	Night	30% 17% 30% 18% 4	760
	11th to 20th	Night	30% 14% 32% 18% 6% 1	760
	21st to end	Night	23% 11% 36% 22% 8% 1	836
February	1st to 10th	Night	24% 20% 33% 20% 3	760
	11th to 20th	Night	22% 19% 36% 18% 5%	743
	21st to end	Night	28% 19% 29% 19% 4	628
March	1st to 10th	Night	23% 19% 35% 19% 4	760
	11th to 20th	Night	23% 15% 35% 21% 5% 1	760
	21st to end	Night	23% 12% 32% 25% 8%	836
April	1st to 10th	Night	29% 14% 33% 20% 5%	760
	11th to 20th	Night	27% 13% 31% 20% 9% 1	694
	21st to end	Night	25% 11% 29% 26% 8% 1	570
May	1st to 10th	Night	24% 6% 27% 30% 11% 2	508
	11th to 20th	Night	21% 8% 31% 29% 10% 1	374
	21st to end	Night	13% 8% 32% 33% 14%	411
June	1st to 10th	Night	19% 5% 29% 36% 9% 1	380
	11th to 20th	Night	17% 8% 24% 37% 13%	380
	21st to end	Night	21% 5% 20% 40% 14%	380
July	1st to 10th	Night	9% 5% 24% 41% 19% 1	370
	11th to 20th	Night	15% 5% 24% 36% 20% 1	368
	21st to end	Night	12% 3 23% 41% 20%	491
August	1st to 10th	Night	13% 3 20% 35% 27% 2	567
	11th to 20th	Night	13% 4 15% 39% 26% 3	564
	21st to end	Night	17% 4 24% 31% 21% 2	708
September	1st to 10th	Night	15% 8% 26% 30% 19% 2	760
	11th to 20th	Night	17% 4 23% 29% 22% 4	760
	21st to end	Night	23% 8% 19% 30% 18% 3	760
October	1st to 10th	Night	23% 8% 28% 26% 14% 1	760
	11th to 20th	Night	31% 11% 26% 22% 8% 1	760
	21st to end	Night	33% 14% 28% 20% 5%	836
November	1st to 10th	Night	29% 12% 28% 23% 8%	780
	11th to 20th	Night	28% 17% 31% 17% 7% 1	800
	21st to end	Night	33% 13% 29% 20% 5%	800
December	1st to 10th	Night	35% 17% 29% 16% 4	768
	11th to 20th	Night	29% 17% 34% 16% 3 1	760
	21st to end	Night	35% 15% 28% 20% 2	836

Page generated at 2024-11-29 10:43:05. Version ac07

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