Sackville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sackville clear sky chart from 2005-11-06 to 2024-02-05.

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	18% 10% 4 7% 6% 3 4 4 5% 7% 32%	78136
	Night	19% 11% 4 7% 6% 3 4 4 5% 6% 32%	80723
Transparency	Day	53% 6% 12% 19% 9% 1	77833
	Night	54% 5% 12% 19% 9% 1	80562
Seeing	Day	26% 20% 32% 16% 5% 1	15851
	Night	26% 17% 31% 20% 5%	23550

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	14% 12% 4 8% 6% 4 5% 5% 5% 4 32%	2207
	11th to 20th	Day	15% 13% 6% 9% 6% 4 4 4 4 5% 33%	2483
	21st to end	Day	13% 10% 5% 10% 8% 3 5% 5% 5% 6% 30%	3124
February	1st to 10th	Day	17% 11% 5% 9% 7% 4 4 4 5% 6% 29%	1656
	11th to 20th	Day	17% 14% 5% 7% 6% 4 4 5% 5% 6% 27%	1573
	21st to end	Day	10% 11% 6% 9% 6% 3 5% 4 5% 8% 32%	1332
March	1st to 10th	Day	16% 16% 5% 9% 7% 3 3 4 4 5% 27%	1970
	11th to 20th	Day	14% 10% 6% 10% 7% 3 4 4 5% 6% 30%	1980
	21st to end	Day	17% 14% 7% 8% 6% 3 3 4 3 5% 29%	2178
April	1st to 10th	Day	21% 13% 5% 7% 7% 3 4 4 5% 6% 26%	2143
	11th to 20th	Day	20% 12% 3 6% 6% 3 4 4 5% 7% 30%	2241
	21st to end	Day	23% 11% 3 6% 5% 3 5% 4 5% 7% 27%	2340
May	1st to 10th	Day	25% 11% 3 7% 6% 3 4 4 5% 6% 26%	2408
	11th to 20th	Day	24% 8% 3 5% 5% 3 4 4 5% 6% 34%	2478
	21st to end	Day	19% 10% 4 7% 5% 3 4 4 5% 8% 31%	2724
June	1st to 10th	Day	27% 9% 3 5% 5% 3 5% 4 6% 7% 26%	2607
	11th to 20th	Day	21% 8% 3 6% 6% 3 5% 5% 6% 6% 31%	2700
	21st to end	Day	26% 8% 3 6% 5% 3 4 3 5% 7% 29%	2700
July	1st to 10th	Day	17% 7% 3 4 6% 3 5% 5% 6% 9% 35%	2700
	11th to 20th	Day	14% 6% 3 7% 4 4 5% 5% 7% 9% 35%	2611
	21st to end	Day	18% 7% 3 6% 6% 3 5% 5% 7% 8% 30%	2691
August	1st to 10th	Day	16% 5% 3 5% 6% 4 5% 6% 6% 8% 37%	2327
	11th to 20th	Day	16% 6% 3 6% 5% 4 5% 6% 7% 9% 32%	2304
	21st to end	Day	13% 7% 3 5% 6% 4 5% 5% 5% 7% 42%	2507
September	1st to 10th	Day	16% 5% 2 4 6% 3 4 5% 5% 7% 42%	2160
	11th to 20th	Day	16% 9% 3 6% 5% 2 4 4 4 7% 39%	2075
	21st to end	Day	19% 6% 2 5% 4 3 4 3 5% 6% 44%	1935
October	1st to 10th	Day	17% 7% 3 6% 5% 2 4 5% 5% 7% 38%	1800
	11th to 20th	Day	19% 8% 3 7% 5% 4 5% 4 5% 6% 35%	1800
	21st to end	Day	18% 10% 4 6% 7% 3 5% 5% 4 6% 31%	1972
November	1st to 10th	Day	20% 11% 3 8% 6% 4 5% 4 4 5% 31%	1495
	11th to 20th	Day	19% 11% 4 8% 4 3 4 4 5% 6% 32%	1520
	21st to end	Day	18% 12% 5% 8% 6% 3 3 5% 5% 5% 30%	1520
December	1st to 10th	Day	23% 12% 5% 5% 5% 3 3 3 4 5% 29%	1520
	11th to 20th	Day	19% 17% 6% 9% 5% 3 3 4 4 4 26%	1906
	21st to end	Day	19% 12% 7% 12% 6% 3 4 4 4 5% 24%	2449
January	1st to 10th	Night	14% 12% 4 7% 5% 3 4 4 5% 6% 36%	4748
	11th to 20th	Night	17% 13% 4 9% 7% 3 4 4 4 5% 29%	4467
	21st to end	Night	14% 11% 4 10% 9% 3 4 4 5% 6% 30%	4532
February	1st to 10th	Night	18% 11% 4 9% 7% 3 5% 4 5% 6% 28%	2399
	11th to 20th	Night	18% 14% 4 8% 6% 3 5% 5% 5% 5% 27%	2273
	21st to end	Night	12% 14% 5% 9% 6% 3 5% 4 5% 5% 32%	1924
March	1st to 10th	Night	16% 14% 5% 8% 6% 3 4 5% 4 5% 29%	1974
	11th to 20th	Night	17% 12% 4 7% 6% 4 4 5% 6% 5% 29%	1979
	21st to end	Night	19% 12% 5% 8% 6% 3 4 4 3 5% 32%	2178
April	1st to 10th	Night	24% 13% 4 8% 6% 3 5% 4 5% 4 25%	1816
	11th to 20th	Night	22% 11% 4 6% 4 2 5% 3 4 5% 33%	1666
	21st to end	Night	23% 12% 4 7% 5% 3 4 4 4 6% 28%	1620
May	1st to 10th	Night	26% 10% 3 5% 5% 3 4 5% 5% 6% 29%	1550
	11th to 20th	Night	23% 9% 4 4 5% 3 4 4 5% 6% 33%	1416
	21st to end	Night	17% 9% 3 7% 6% 3 5% 6% 5% 7% 33%	1550
June	1st to 10th	Night	26% 10% 3 7% 5% 4 4 4 5% 7% 25%	1367
	11th to 20th	Night	23% 6% 4 6% 5% 3 4 4 5% 7% 33%	1260
	21st to end	Night	22% 10% 4 6% 5% 3 5% 5% 5% 8% 27%	1260
July	1st to 10th	Night	16% 8% 3 7% 5% 2 6% 5% 7% 9% 31%	1260
	11th to 20th	Night	14% 8% 4 6% 6% 4 7% 5% 7% 10% 31%	1327
	21st to end	Night	16% 7% 4 6% 6% 4 6% 7% 6% 8% 29%	1623
August	1st to 10th	Night	14% 5% 2 6% 7% 3 7% 5% 7% 7% 36%	1612
	11th to 20th	Night	15% 9% 3 7% 6% 3 5% 5% 8% 8% 31%	1596
	21st to end	Night	13% 6% 3 6% 4 3 4 5% 6% 8% 41%	1849
September	1st to 10th	Night	16% 6% 3 5% 5% 2 4 5% 4 9% 40%	1800
	11th to 20th	Night	16% 7% 3 6% 5% 3 3 4 4 6% 44%	1882
	21st to end	Night	18% 7% 2 5% 4 3 4 4 4 6% 43%	2024
October	1st to 10th	Night	19% 7% 3 5% 6% 3 3 4 5% 7% 39%	2160
	11th to 20th	Night	19% 8% 3 6% 4 3 4 4 4 7% 37%	2160
	21st to end	Night	25% 9% 3 6% 5% 3 4 4 4 5% 32%	2382
November	1st to 10th	Night	22% 10% 3 7% 5% 3 5% 4 4 6% 31%	2583
	11th to 20th	Night	20% 9% 4 7% 6% 4 4 5% 4 6% 30%	2660
	21st to end	Night	21% 10% 5% 7% 5% 3 4 4 4 6% 31%	2660
December	1st to 10th	Night	25% 11% 5% 6% 6% 2 4 4 4 6% 27%	2660
	11th to 20th	Night	24% 16% 5% 7% 4 2 3 3 4 4 27%	3293
	21st to end	Night	24% 13% 6% 10% 4 3 3 3 3 4 27%	5213

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	56% 4 14% 16% 9% 1	2208
	11th to 20th	Day	57% 4 8% 18% 12% 1	2483
	21st to end	Day	55% 5% 13% 14% 13% 1	3124
February	1st to 10th	Day	57% 4 11% 16% 10% 1	1656
	11th to 20th	Day	59% 5% 10% 15% 9% 1	1581
	21st to end	Day	52% 4 11% 20% 11% 2	1332
March	1st to 10th	Day	60% 4 9% 17% 8% 1	1974
	11th to 20th	Day	57% 4 10% 18% 9% 2	1980
	21st to end	Day	60% 4 8% 17% 9% 2	2178
April	1st to 10th	Day	61% 4 7% 15% 9% 3	2143
	11th to 20th	Day	55% 5% 9% 20% 11% 1	2241
	21st to end	Day	57% 4 11% 17% 9% 2	2340
May	1st to 10th	Day	60% 5% 9% 16% 9% 1	2408
	11th to 20th	Day	51% 7% 9% 22% 11% 1	2482
	21st to end	Day	52% 7% 13% 20% 7% 1	2724
June	1st to 10th	Day	58% 6% 11% 19% 5%	2607
	11th to 20th	Day	52% 7% 12% 20% 9% 1	2700
	21st to end	Day	56% 6% 12% 16% 9% 1	2700
July	1st to 10th	Day	44% 8% 16% 22% 10%	2625
	11th to 20th	Day	43% 8% 18% 22% 8% 1	2530
	21st to end	Day	50% 9% 16% 20% 6%	2541
August	1st to 10th	Day	43% 10% 14% 26% 7%	2314
	11th to 20th	Day	47% 9% 16% 22% 6%	2304
	21st to end	Day	40% 7% 16% 25% 11%	2507
September	1st to 10th	Day	41% 6% 16% 25% 13%	2160
	11th to 20th	Day	45% 5% 12% 24% 13% 1	2075
	21st to end	Day	42% 4 10% 28% 14% 1	1935
October	1st to 10th	Day	45% 5% 12% 28% 10% 1	1800
	11th to 20th	Day	51% 5% 13% 24% 7% 1	1800
	21st to end	Day	54% 6% 11% 19% 10%	1972
November	1st to 10th	Day	57% 5% 9% 19% 9%	1495
	11th to 20th	Day	54% 5% 14% 17% 10% 1	1520
	21st to end	Day	57% 5% 13% 17% 8%	1520
December	1st to 10th	Day	59% 5% 14% 17% 6%	1520
	11th to 20th	Day	63% 4 10% 15% 7% 1	1905
	21st to end	Day	64% 5% 14% 11% 6% 1	2449
January	1st to 10th	Night	49% 4 13% 26% 7% 1	4748
	11th to 20th	Night	56% 6% 9% 20% 8% 1	4467
	21st to end	Night	55% 5% 11% 19% 8% 1	4532
February	1st to 10th	Night	57% 4 11% 13% 12% 2	2399
	11th to 20th	Night	59% 5% 10% 14% 11% 1	2276
	21st to end	Night	55% 3 10% 18% 13% 2	1924
March	1st to 10th	Night	58% 4 8% 17% 11% 2	1983
	11th to 20th	Night	56% 5% 9% 17% 10% 2	1980
	21st to end	Night	57% 4 7% 18% 11% 2	2178
April	1st to 10th	Night	62% 5% 8% 12% 10% 4	1816
	11th to 20th	Night	54% 4 9% 20% 12% 1	1666
	21st to end	Night	58% 5% 10% 15% 12% 1	1620
May	1st to 10th	Night	56% 5% 9% 18% 10% 2	1550
	11th to 20th	Night	52% 5% 9% 23% 9% 1	1417
	21st to end	Night	51% 6% 14% 19% 9% 1	1551
June	1st to 10th	Night	58% 6% 11% 17% 8%	1367
	11th to 20th	Night	51% 6% 10% 23% 8% 1	1260
	21st to end	Night	55% 9% 12% 14% 9% 1	1260
July	1st to 10th	Night	47% 8% 15% 22% 7%	1225
	11th to 20th	Night	46% 9% 14% 22% 8%	1285
	21st to end	Night	51% 9% 15% 17% 7%	1534
August	1st to 10th	Night	43% 9% 17% 23% 8%	1600
	11th to 20th	Night	47% 10% 17% 21% 5%	1596
	21st to end	Night	40% 7% 18% 26% 9%	1849
September	1st to 10th	Night	42% 6% 13% 28% 11%	1800
	11th to 20th	Night	42% 5% 12% 26% 14% 1	1882
	21st to end	Night	43% 5% 11% 27% 13% 1	2024
October	1st to 10th	Night	44% 5% 13% 25% 12%	2160
	11th to 20th	Night	47% 6% 12% 27% 8%	2160
	21st to end	Night	56% 5% 10% 18% 11% 1	2382
November	1st to 10th	Night	56% 5% 11% 18% 10% 1	2583
	11th to 20th	Night	54% 6% 13% 16% 10% 1	2660
	21st to end	Night	55% 5% 13% 18% 8%	2660
December	1st to 10th	Night	60% 4 12% 17% 7%	2660
	11th to 20th	Night	62% 4 8% 17% 9%	3295
	21st to end	Night	63% 3 13% 14% 6% 1	5213

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	32% 25% 30% 12% 1	180
	11th to 20th	Day	32% 25% 26% 12% 4	317
	21st to end	Day	20% 21% 39% 14% 4	407
February	1st to 10th	Day	30% 22% 32% 13% 3	352
	11th to 20th	Day	33% 23% 29% 12% 2 1	336
	21st to end	Day	20% 22% 38% 16% 4	280
March	1st to 10th	Day	28% 26% 32% 11% 2 1	420
	11th to 20th	Day	25% 24% 33% 14% 4 1	420
	21st to end	Day	30% 24% 29% 11% 4 1	462
April	1st to 10th	Day	35% 29% 25% 9% 1 1	420
	11th to 20th	Day	33% 26% 26% 11% 4	412
	21st to end	Day	30% 24% 29% 12% 5% 1	420
May	1st to 10th	Day	35% 22% 25% 14% 4 1	491
	11th to 20th	Day	29% 19% 29% 16% 6% 1	624
	21st to end	Day	27% 20% 33% 17% 3	680
June	1st to 10th	Day	34% 17% 30% 15% 4	630
	11th to 20th	Day	26% 18% 33% 19% 5%	630
	21st to end	Day	25% 15% 31% 21% 6% 1	630
July	1st to 10th	Day	24% 15% 37% 18% 5% 1	620
	11th to 20th	Day	17% 11% 40% 23% 8% 1	618
	21st to end	Day	21% 13% 40% 19% 7%	631
August	1st to 10th	Day	14% 14% 40% 26% 6%	446
	11th to 20th	Day	21% 12% 35% 22% 9% 1	439
	21st to end	Day	16% 19% 31% 25% 7% 2	495
September	1st to 10th	Day	16% 16% 42% 17% 8% 1	450
	11th to 20th	Day	22% 18% 32% 19% 6% 2	450
	21st to end	Day	23% 17% 33% 17% 7% 2	427
October	1st to 10th	Day	25% 16% 28% 19% 10% 2	360
	11th to 20th	Day	24% 20% 28% 20% 6% 2	360
	21st to end	Day	28% 22% 29% 15% 6% 1	396
November	1st to 10th	Day	29% 19% 31% 13% 7% 2	365
	11th to 20th	Day	32% 22% 27% 14% 5% 1	370
	21st to end	Day	32% 22% 31% 12% 3	370
December	1st to 10th	Day	34% 19% 30% 13% 3 1	370
	11th to 20th	Day	35% 25% 28% 11% 1	370
	21st to end	Day	29% 24% 33% 13% 2	203
January	1st to 10th	Night	28% 20% 31% 17% 5%	850
	11th to 20th	Night	30% 20% 29% 17% 4	833
	21st to end	Night	22% 21% 33% 19% 5%	836
February	1st to 10th	Night	29% 18% 34% 17% 2	739
	11th to 20th	Night	29% 24% 30% 13% 2 1	703
	21st to end	Night	22% 19% 36% 18% 4 1	592
March	1st to 10th	Night	25% 20% 35% 17% 2	720
	11th to 20th	Night	26% 18% 29% 20% 5% 1	720
	21st to end	Night	27% 18% 31% 18% 6%	792
April	1st to 10th	Night	32% 19% 29% 17% 3	556
	11th to 20th	Night	30% 18% 29% 18% 5% 1	534
	21st to end	Night	31% 16% 30% 18% 5% 1	540
May	1st to 10th	Night	31% 14% 29% 21% 5%	540
	11th to 20th	Night	27% 16% 29% 23% 5%	532
	21st to end	Night	23% 14% 42% 18% 3	583
June	1st to 10th	Night	32% 12% 32% 19% 5%	467
	11th to 20th	Night	25% 11% 33% 27% 4	360
	21st to end	Night	24% 8% 34% 28% 6% 1	360
July	1st to 10th	Night	19% 8% 42% 23% 8%	350
	11th to 20th	Night	17% 10% 39% 29% 5%	415
	21st to end	Night	20% 9% 37% 29% 5%	590
August	1st to 10th	Night	16% 8% 40% 28% 8%	538
	11th to 20th	Night	18% 10% 35% 28% 8% 1	532
	21st to end	Night	16% 10% 32% 31% 10% 1	594
September	1st to 10th	Night	21% 9% 37% 26% 7%	540
	11th to 20th	Night	20% 13% 27% 31% 9% 1	622
	21st to end	Night	22% 12% 31% 26% 8%	720
October	1st to 10th	Night	23% 12% 29% 27% 9% 1	720
	11th to 20th	Night	23% 14% 31% 23% 8% 1	720
	21st to end	Night	30% 21% 29% 16% 4	792
November	1st to 10th	Night	30% 17% 27% 19% 6%	825
	11th to 20th	Night	27% 22% 27% 18% 6% 1	850
	21st to end	Night	28% 22% 30% 16% 4	850
December	1st to 10th	Night	33% 19% 28% 17% 4	850
	11th to 20th	Night	31% 22% 31% 12% 3	850
	21st to end	Night	33% 21% 24% 18% 3 1	935

Page generated at 2024-02-02 06:20:29. Version ac07

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