East Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the East Point clear sky chart from 2005-11-06 to 2024-12-06.

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% 12% 4 10% 5% 5% 4 4 5% 6% 27%	102103
	Night	20% 13% 5% 12% 5% 4 4 3 4 5% 24%	97692
Transparency	Day	56% 7% 13% 17% 6%	105618
	Night	61% 7% 12% 15% 6%	102273
Seeing	Day	23% 9% 23% 28% 14% 2	17713
	Night	25% 10% 26% 27% 11% 1	25034

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% 15% 10% 28% 5% 5% 3 3 3 3 10%	2526
	11th to 20th	Day	13% 14% 7% 22% 7% 5% 5% 3 5% 5% 12%	2530
	21st to end	Day	13% 12% 9% 25% 7% 6% 5% 3 4 4 12%	2937
February	1st to 10th	Day	19% 14% 5% 14% 8% 7% 5% 3 4 4 16%	1710
	11th to 20th	Day	16% 16% 5% 12% 9% 6% 5% 4 5% 5% 18%	1663
	21st to end	Day	9% 12% 4 11% 10% 7% 5% 3 5% 7% 27%	1503
March	1st to 10th	Day	19% 13% 4 8% 5% 6% 3 3 4 5% 29%	3207
	11th to 20th	Day	12% 15% 6% 13% 8% 6% 5% 4 5% 6% 21%	3480
	21st to end	Day	21% 16% 7% 10% 5% 4 4 3 4 6% 19%	3960
April	1st to 10th	Day	18% 12% 4 8% 6% 4 4 4 5% 5% 30%	2280
	11th to 20th	Day	19% 11% 3 7% 5% 4 4 2 5% 7% 33%	2254
	21st to end	Day	19% 12% 4 7% 4 3 4 3 5% 6% 32%	2484
May	1st to 10th	Day	24% 14% 3 7% 4 4 3 3 4 5% 28%	4425
	11th to 20th	Day	17% 8% 2 7% 4 3 3 3 5% 7% 40%	4398
	21st to end	Day	18% 8% 3 8% 6% 5% 6% 4 6% 8% 29%	4836
June	1st to 10th	Day	23% 12% 3 8% 5% 4 5% 4 6% 6% 24%	2660
	11th to 20th	Day	18% 8% 3 7% 5% 4 5% 3 5% 7% 36%	2660
	21st to end	Day	23% 10% 3 7% 5% 4 4 3 6% 7% 29%	2844
July	1st to 10th	Day	18% 9% 3 8% 4 5% 5% 4 6% 8% 30%	4445
	11th to 20th	Day	14% 7% 2 8% 5% 5% 5% 4 7% 8% 35%	4440
	21st to end	Day	11% 8% 3 8% 5% 4 5% 4 6% 8% 38%	4815
August	1st to 10th	Day	17% 9% 4 10% 5% 6% 5% 4 6% 8% 28%	4304
	11th to 20th	Day	14% 7% 3 7% 4 4 4 4 6% 8% 37%	4045
	21st to end	Day	13% 7% 3 7% 5% 4 5% 4 5% 6% 41%	4254
September	1st to 10th	Day	17% 7% 2 6% 4 4 4 4 5% 8% 39%	2280
	11th to 20th	Day	18% 9% 3 7% 4 4 5% 3 5% 7% 35%	2280
	21st to end	Day	18% 9% 3 5% 4 4 4 3 5% 8% 35%	2001
October	1st to 10th	Day	20% 9% 2 7% 5% 5% 4 4 5% 8% 31%	1900
	11th to 20th	Day	21% 13% 3 8% 5% 5% 5% 4 6% 7% 23%	1900
	21st to end	Day	23% 17% 4 8% 5% 5% 3 3 5% 6% 20%	1971
November	1st to 10th	Day	21% 21% 4 10% 6% 4 5% 3 4 4 19%	1662
	11th to 20th	Day	23% 23% 6% 10% 6% 4 4 4 4 4 13%	1600
	21st to end	Day	20% 24% 8% 11% 5% 4 4 3 4 5% 11%	1600
December	1st to 10th	Day	24% 23% 10% 13% 6% 4 3 2 2 4 9%	1560
	11th to 20th	Day	25% 24% 10% 15% 7% 3 4 2 3 3 4	1906
	21st to end	Day	20% 22% 10% 16% 4 4 3 3 3 3 12%	2783
January	1st to 10th	Night	14% 16% 12% 26% 5% 4 3 2 3 3 11%	4429
	11th to 20th	Night	18% 13% 7% 26% 7% 5% 4 3 4 4 11%	4440
	21st to end	Night	15% 14% 7% 26% 7% 4 4 3 3 4 13%	4724
February	1st to 10th	Night	20% 13% 4 13% 8% 6% 4 4 4 4 20%	2470
	11th to 20th	Night	17% 14% 4 14% 9% 6% 4 3 5% 5% 19%	2403
	21st to end	Night	13% 14% 5% 12% 7% 5% 4 3 5% 6% 27%	1951
March	1st to 10th	Night	20% 12% 4 9% 7% 5% 4 3 4 5% 27%	3630
	11th to 20th	Night	19% 16% 5% 12% 7% 4 4 3 4 5% 20%	3479
	21st to end	Night	23% 15% 5% 12% 6% 5% 5% 4 4 3 19%	3671
April	1st to 10th	Night	21% 12% 4 8% 5% 4 4 4 5% 5% 27%	1900
	11th to 20th	Night	19% 11% 4 8% 5% 4 4 3 5% 5% 33%	1876
	21st to end	Night	24% 11% 3 8% 5% 3 3 2 3 5% 33%	1691
May	1st to 10th	Night	27% 16% 4 7% 4 4 3 3 4 5% 22%	2525
	11th to 20th	Night	15% 8% 4 7% 4 5% 5% 3 5% 7% 38%	2506
	21st to end	Night	18% 10% 3 7% 6% 5% 4 5% 6% 8% 27%	2749
June	1st to 10th	Night	28% 9% 3 8% 4 5% 5% 4 4 6% 24%	1520
	11th to 20th	Night	21% 6% 2 6% 4 3 4 4 5% 6% 38%	1520
	21st to end	Night	23% 9% 4 8% 5% 5% 5% 4 5% 6% 27%	1341
July	1st to 10th	Night	17% 10% 4 8% 7% 6% 6% 5% 7% 5% 25%	2466
	11th to 20th	Night	15% 7% 3 7% 5% 5% 5% 4 8% 9% 32%	2530
	21st to end	Night	14% 8% 2 6% 4 4 5% 3 5% 8% 41%	2750
August	1st to 10th	Night	17% 9% 3 8% 5% 4 5% 5% 7% 9% 28%	2629
	11th to 20th	Night	13% 8% 2 9% 5% 5% 5% 4 6% 7% 35%	2782
	21st to end	Night	12% 6% 2 6% 4 4 4 4 6% 8% 42%	3402
September	1st to 10th	Night	18% 7% 2 6% 4 4 5% 4 5% 7% 40%	1900
	11th to 20th	Night	20% 8% 3 6% 4 4 4 3 5% 5% 39%	1900
	21st to end	Night	20% 9% 2 7% 4 5% 4 3 4 6% 35%	2174
October	1st to 10th	Night	21% 8% 2 7% 5% 4 4 3 5% 6% 34%	2280
	11th to 20th	Night	23% 12% 3 8% 5% 5% 4 3 5% 7% 27%	2280
	21st to end	Night	28% 16% 4 8% 4 4 4 3 3 5% 21%	2627
November	1st to 10th	Night	21% 19% 4 10% 5% 4 4 3 4 5% 22%	2633
	11th to 20th	Night	26% 22% 5% 8% 5% 4 4 3 4 5% 13%	2800
	21st to end	Night	25% 23% 8% 10% 5% 5% 4 3 4 4 11%	2800
December	1st to 10th	Night	25% 21% 8% 13% 6% 4 4 2 4 4 9%	2737
	11th to 20th	Night	27% 20% 9% 16% 5% 3 3 2 2 2 9%	3293
	21st to end	Night	28% 19% 7% 16% 5% 3 2 2 3 3 13%	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	80% 8% 7% 4 2	2527
	11th to 20th	Day	70% 6% 13% 8% 3	2530
	21st to end	Day	72% 7% 10% 7% 4 1	2937
February	1st to 10th	Day	70% 5% 10% 11% 3	1710
	11th to 20th	Day	66% 6% 10% 13% 4 1	1671
	21st to end	Day	56% 6% 13% 15% 9% 2	1503
March	1st to 10th	Day	59% 4 10% 19% 8%	3211
	11th to 20th	Day	61% 8% 13% 13% 5% 1	3480
	21st to end	Day	67% 5% 10% 12% 5% 1	3960
April	1st to 10th	Day	55% 6% 11% 18% 9% 2	2280
	11th to 20th	Day	52% 5% 10% 21% 11% 1	2254
	21st to end	Day	52% 6% 12% 16% 10% 3	2484
May	1st to 10th	Day	57% 7% 14% 14% 7% 1	4440
	11th to 20th	Day	44% 8% 15% 25% 8%	4402
	21st to end	Day	49% 11% 14% 19% 7%	4836
June	1st to 10th	Day	59% 6% 13% 17% 5%	2660
	11th to 20th	Day	48% 6% 13% 24% 8% 1	2660
	21st to end	Day	54% 8% 12% 16% 9% 1	2844
July	1st to 10th	Day	49% 10% 15% 17% 10%	4375
	11th to 20th	Day	44% 10% 17% 22% 6%	4364
	21st to end	Day	42% 9% 20% 23% 6%	4662
August	1st to 10th	Day	53% 8% 15% 20% 4	4290
	11th to 20th	Day	43% 8% 15% 26% 7%	4084
	21st to end	Day	41% 7% 13% 28% 10%	4254
September	1st to 10th	Day	41% 8% 16% 26% 9%	2280
	11th to 20th	Day	49% 7% 13% 22% 9%	2280
	21st to end	Day	46% 8% 13% 23% 10%	2001
October	1st to 10th	Day	52% 7% 13% 20% 7%	3160
	11th to 20th	Day	55% 7% 12% 21% 5%	3140
	21st to end	Day	55% 8% 15% 19% 3	3229
November	1st to 10th	Day	68% 7% 10% 12% 3	1662
	11th to 20th	Day	75% 6% 10% 8% 2	1600
	21st to end	Day	77% 6% 11% 6% 1	1600
December	1st to 10th	Day	81% 6% 7% 5% 1	1560
	11th to 20th	Day	87% 5% 4 2 1	1905
	21st to end	Day	78% 6% 10% 4 2	2783
January	1st to 10th	Night	79% 7% 8% 5% 1	4429
	11th to 20th	Night	76% 5% 10% 6% 2	4440
	21st to end	Night	76% 5% 8% 8% 3	4724
February	1st to 10th	Night	67% 5% 10% 11% 6% 1	2470
	11th to 20th	Night	67% 6% 10% 13% 4 1	2406
	21st to end	Night	57% 6% 10% 16% 9% 1	1951
March	1st to 10th	Night	58% 4 9% 19% 9%	3639
	11th to 20th	Night	66% 6% 10% 12% 5% 1	3480
	21st to end	Night	68% 6% 7% 12% 6% 1	3671
April	1st to 10th	Night	58% 5% 11% 14% 10% 1	1900
	11th to 20th	Night	53% 5% 9% 20% 11% 2	1876
	21st to end	Night	55% 5% 9% 17% 11% 2	1691
May	1st to 10th	Night	64% 6% 9% 14% 6% 1	2530
	11th to 20th	Night	45% 8% 17% 21% 9% 1	2507
	21st to end	Night	51% 11% 16% 16% 6%	2750
June	1st to 10th	Night	60% 7% 11% 17% 5%	1520
	11th to 20th	Night	45% 7% 13% 20% 14%	1520
	21st to end	Night	57% 8% 13% 14% 8%	1341
July	1st to 10th	Night	55% 9% 14% 15% 6% 1	2427
	11th to 20th	Night	46% 9% 18% 19% 8%	2482
	21st to end	Night	40% 9% 18% 22% 11%	2663
August	1st to 10th	Night	51% 9% 18% 19% 3	2618
	11th to 20th	Night	45% 9% 18% 23% 5%	2809
	21st to end	Night	36% 9% 17% 29% 8%	3401
September	1st to 10th	Night	42% 8% 12% 27% 9%	1900
	11th to 20th	Night	46% 6% 12% 26% 10%	1900
	21st to end	Night	49% 6% 12% 25% 8%	2174
October	1st to 10th	Night	52% 7% 13% 20% 8%	3800
	11th to 20th	Night	53% 7% 13% 22% 5%	3779
	21st to end	Night	57% 6% 13% 18% 6%	4326
November	1st to 10th	Night	63% 8% 12% 12% 4	2633
	11th to 20th	Night	73% 6% 10% 8% 3	2800
	21st to end	Night	77% 7% 10% 4 1	2800
December	1st to 10th	Night	79% 6% 8% 5% 1	2737
	11th to 20th	Night	83% 4 6% 5% 1	3295
	21st to end	Night	78% 4 9% 7% 1	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	22% 21% 36% 15% 5%	370
	11th to 20th	Day	26% 16% 31% 22% 5% 1	370
	21st to end	Day	17% 14% 37% 26% 5%	407
February	1st to 10th	Day	29% 13% 31% 19% 6% 2	370
	11th to 20th	Day	24% 15% 31% 25% 4 1	366
	21st to end	Day	14% 12% 33% 33% 8% 1	307
March	1st to 10th	Day	20% 10% 32% 27% 9% 1	397
	11th to 20th	Day	15% 12% 31% 29% 11% 1	460
	21st to end	Day	25% 10% 28% 27% 9% 1	506
April	1st to 10th	Day	24% 11% 33% 23% 9%	460
	11th to 20th	Day	24% 7% 32% 26% 9% 2	452
	21st to end	Day	22% 9% 21% 30% 16% 2	482
May	1st to 10th	Day	33% 4 21% 27% 10% 4	653
	11th to 20th	Day	22% 4 17% 35% 18% 4	674
	21st to end	Day	21% 5% 24% 36% 13% 1	735
June	1st to 10th	Day	29% 7% 16% 31% 15% 3	680
	11th to 20th	Day	19% 4 18% 37% 19% 2	680
	21st to end	Day	26% 6% 12% 32% 21% 3	680
July	1st to 10th	Day	20% 2 15% 41% 20% 2	670
	11th to 20th	Day	16% 4 14% 38% 24% 3	668
	21st to end	Day	20% 4 15% 35% 25% 2	740
August	1st to 10th	Day	15% 3 13% 38% 28% 3	607
	11th to 20th	Day	19% 5% 12% 33% 24% 7%	479
	21st to end	Day	17% 4 17% 29% 27% 5%	539
September	1st to 10th	Day	15% 6% 23% 36% 17% 3	490
	11th to 20th	Day	23% 8% 20% 31% 16% 3	490
	21st to end	Day	20% 7% 26% 27% 15% 4	415
October	1st to 10th	Day	22% 7% 24% 30% 14% 4	390
	11th to 20th	Day	24% 10% 28% 23% 13% 2	390
	21st to end	Day	28% 13% 30% 21% 7% 1	429
November	1st to 10th	Day	29% 16% 29% 19% 6% 1	395
	11th to 20th	Day	33% 19% 27% 16% 5% 1	400
	21st to end	Day	35% 17% 29% 17% 3	400
December	1st to 10th	Day	34% 13% 34% 15% 4	385
	11th to 20th	Day	32% 21% 29% 16% 2	370
	21st to end	Day	25% 22% 32% 15% 6% 1	407
January	1st to 10th	Night	28% 17% 32% 19% 5%	850
	11th to 20th	Night	27% 13% 34% 20% 5%	850
	21st to end	Night	21% 17% 33% 22% 7%	890
February	1st to 10th	Night	27% 13% 30% 23% 7%	760
	11th to 20th	Night	24% 12% 38% 22% 5%	743
	21st to end	Night	18% 10% 32% 28% 10% 1	628
March	1st to 10th	Night	22% 9% 34% 29% 6%	760
	11th to 20th	Night	22% 10% 28% 28% 12% 1	760
	21st to end	Night	27% 9% 28% 25% 9% 1	755
April	1st to 10th	Night	24% 12% 25% 31% 8%	570
	11th to 20th	Night	23% 7% 28% 29% 12% 1	564
	21st to end	Night	27% 5% 25% 29% 10% 3	570
May	1st to 10th	Night	31% 4 22% 26% 13% 5%	570
	11th to 20th	Night	22% 5% 18% 31% 19% 5%	562
	21st to end	Night	22% 4 24% 38% 11% 1	616
June	1st to 10th	Night	30% 7% 18% 34% 10% 1	570
	11th to 20th	Night	23% 3 18% 39% 16% 1	570
	21st to end	Night	28% 3 15% 39% 14% 2	391
July	1st to 10th	Night	17% 3 15% 39% 22% 3	518
	11th to 20th	Night	18% 1 13% 44% 21% 2	552
	21st to end	Night	20% 3 13% 41% 20% 2	623
August	1st to 10th	Night	18% 2 15% 41% 23% 1	568
	11th to 20th	Night	19% 2 15% 38% 21% 5%	562
	21st to end	Night	14% 5% 18% 33% 27% 2	627
September	1st to 10th	Night	20% 4 22% 34% 18% 2	570
	11th to 20th	Night	22% 6% 21% 31% 18% 1	570
	21st to end	Night	21% 8% 26% 32% 11% 2	703
October	1st to 10th	Night	25% 5% 29% 28% 12% 1	760
	11th to 20th	Night	27% 9% 26% 25% 11% 2	760
	21st to end	Night	34% 14% 27% 19% 5%	899
November	1st to 10th	Night	30% 17% 27% 21% 4 1	880
	11th to 20th	Night	33% 17% 27% 16% 6% 1	900
	21st to end	Night	35% 17% 27% 17% 3	900
December	1st to 10th	Night	31% 17% 31% 15% 6%	878
	11th to 20th	Night	30% 22% 29% 15% 4	850
	21st to end	Night	31% 17% 30% 16% 4 1	935

Page generated at 2024-12-03 07:45:09. Version ac07

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