Flanders Pond Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Flanders Pond Observatory clear sky chart from 2005-11-06 to 2024-11-11.

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	20% 8% 2 6% 4 4 4 3 5% 7% 37%	101334
	Night	20% 9% 3 6% 4 4 4 3 5% 6% 36%	97868
Transparency	Day	46% 6% 13% 21% 12% 2	104871
	Night	47% 6% 12% 21% 12% 1	102421
Seeing	Day	24% 18% 32% 19% 6% 1	15957
	Night	24% 16% 31% 22% 7% 1	24165

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	18% 9% 2 7% 4 5% 4 3 4 5% 39%	2466
	11th to 20th	Day	18% 8% 2 5% 3 3 3 3 4 5% 45%	2520
	21st to end	Day	16% 10% 3 7% 4 4 4 3 6% 7% 36%	2904
February	1st to 10th	Day	18% 11% 3 6% 5% 4 4 4 5% 7% 33%	1710
	11th to 20th	Day	15% 9% 2 8% 6% 4 5% 3 5% 6% 37%	1734
	21st to end	Day	14% 11% 3 8% 6% 4 4 4 5% 7% 36%	1570
March	1st to 10th	Day	26% 13% 3 8% 3 3 3 2 4 5% 31%	3193
	11th to 20th	Day	19% 10% 3 6% 5% 5% 4 3 6% 7% 33%	3480
	21st to end	Day	28% 10% 3 6% 4 3 4 3 4 5% 29%	3816
April	1st to 10th	Day	21% 12% 3 6% 4 4 3 3 5% 6% 33%	2222
	11th to 20th	Day	21% 10% 2 5% 4 3 3 3 4 7% 38%	2442
	21st to end	Day	22% 9% 2 6% 4 4 4 3 4 6% 37%	2470
May	1st to 10th	Day	20% 10% 2 7% 5% 4 4 4 5% 7% 31%	4106
	11th to 20th	Day	19% 8% 3 6% 4 4 5% 3 6% 7% 36%	4081
	21st to end	Day	19% 7% 2 6% 4 4 4 4 6% 8% 35%	4948
June	1st to 10th	Day	24% 8% 2 6% 5% 4 3 4 5% 7% 31%	2850
	11th to 20th	Day	20% 7% 2 6% 4 4 4 3 5% 7% 38%	2850
	21st to end	Day	26% 8% 3 6% 4 4 4 4 6% 6% 29%	2850
July	1st to 10th	Day	18% 7% 2 7% 5% 4 5% 4 5% 8% 35%	4673
	11th to 20th	Day	18% 6% 2 5% 3 3 4 3 6% 9% 40%	4440
	21st to end	Day	22% 7% 2 5% 3 4 4 4 5% 7% 36%	4666
August	1st to 10th	Day	21% 8% 2 7% 5% 4 4 4 5% 7% 35%	4105
	11th to 20th	Day	19% 8% 2 7% 5% 4 4 4 6% 8% 35%	4045
	21st to end	Day	10% 5% 2 5% 4 3 4 4 6% 9% 49%	4532
September	1st to 10th	Day	13% 4 1 5% 4 3 4 4 4 8% 49%	2190
	11th to 20th	Day	15% 5% 2 5% 3 3 3 2 4 6% 52%	2090
	21st to end	Day	19% 6% 2 5% 4 3 4 3 4 7% 42%	2090
October	1st to 10th	Day	18% 7% 2 6% 4 4 5% 3 5% 7% 40%	2010
	11th to 20th	Day	20% 7% 2 5% 3 4 3 3 4 7% 41%	1900
	21st to end	Day	23% 8% 2 5% 3 4 3 3 4 6% 39%	1905
November	1st to 10th	Day	20% 6% 2 6% 3 4 4 3 6% 5% 41%	1761
	11th to 20th	Day	21% 6% 2 5% 3 3 4 3 5% 7% 41%	1628
	21st to end	Day	20% 10% 3 6% 4 3 4 2 4 5% 40%	1520
December	1st to 10th	Day	24% 8% 2 6% 4 5% 4 3 5% 5% 33%	1468
	11th to 20th	Day	25% 11% 3 6% 3 3 4 3 4 6% 33%	1668
	21st to end	Day	25% 9% 3 6% 3 2 3 3 4 5% 35%	2431
January	1st to 10th	Night	14% 10% 3 7% 5% 4 4 3 5% 5% 41%	4479
	11th to 20th	Night	14% 10% 3 9% 5% 4 4 3 5% 5% 37%	4440
	21st to end	Night	17% 11% 4 8% 5% 4 4 3 5% 6% 34%	4751
February	1st to 10th	Night	18% 10% 3 6% 5% 4 4 4 6% 6% 34%	2470
	11th to 20th	Night	15% 10% 3 7% 5% 4 5% 3 4 6% 38%	2329
	21st to end	Night	16% 11% 2 7% 4 4 4 3 5% 6% 38%	1884
March	1st to 10th	Night	28% 12% 3 6% 4 3 2 2 4 4 31%	3647
	11th to 20th	Night	15% 11% 3 8% 6% 5% 6% 5% 6% 7% 27%	3479
	21st to end	Night	29% 9% 2 6% 4 4 5% 4 5% 5% 27%	3816
April	1st to 10th	Night	24% 10% 2 6% 3 4 4 3 5% 6% 34%	1954
	11th to 20th	Night	22% 9% 2 7% 4 4 3 3 5% 7% 34%	1688
	21st to end	Night	25% 8% 2 6% 5% 4 3 3 5% 7% 33%	1710
May	1st to 10th	Night	23% 9% 3 6% 4 3 3 2 5% 9% 34%	2834
	11th to 20th	Night	19% 8% 3 8% 4 5% 5% 4 7% 8% 30%	2813
	21st to end	Night	16% 11% 3 8% 5% 4 4 4 6% 6% 34%	2659
June	1st to 10th	Night	26% 10% 3 5% 4 3 4 4 6% 6% 27%	1330
	11th to 20th	Night	21% 8% 2 7% 4 4 4 3 6% 7% 35%	1330
	21st to end	Night	28% 10% 3 5% 4 5% 5% 4 3 4 29%	1330
July	1st to 10th	Night	19% 8% 4 7% 5% 4 6% 5% 7% 8% 27%	2289
	11th to 20th	Night	21% 7% 2 6% 4 4 4 5% 5% 8% 34%	2520
	21st to end	Night	19% 7% 2 6% 4 4 5% 4 6% 8% 34%	2855
August	1st to 10th	Night	24% 10% 3 7% 5% 4 5% 4 5% 6% 28%	2825
	11th to 20th	Night	20% 10% 2 7% 4 4 5% 4 6% 8% 30%	2782
	21st to end	Night	11% 6% 2 7% 4 4 4 3 6% 8% 45%	3124
September	1st to 10th	Night	15% 5% 1 5% 4 2 4 4 5% 7% 48%	1985
	11th to 20th	Night	16% 6% 2 4 3 3 3 3 4 6% 49%	2090
	21st to end	Night	19% 6% 2 5% 4 3 4 3 5% 7% 44%	2090
October	1st to 10th	Night	21% 5% 2 5% 4 4 4 3 5% 6% 41%	2169
	11th to 20th	Night	19% 7% 2 6% 3 4 3 3 4 6% 43%	2280
	21st to end	Night	23% 9% 2 5% 3 3 4 2 4 7% 38%	2688
November	1st to 10th	Night	18% 7% 2 5% 3 4 4 4 5% 6% 43%	2537
	11th to 20th	Night	19% 7% 2 6% 4 4 4 4 5% 5% 40%	2557
	21st to end	Night	18% 8% 2 5% 4 4 4 4 6% 7% 39%	2660
December	1st to 10th	Night	25% 11% 2 6% 4 4 3 3 5% 5% 32%	2707
	11th to 20th	Night	25% 8% 2 5% 3 4 3 3 5% 5% 37%	3531
	21st to end	Night	25% 10% 3 5% 4 3 3 2 4 5% 37%	5236

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	48% 4 15% 24% 8% 1	2467
	11th to 20th	Day	43% 4 12% 25% 12% 2	2520
	21st to end	Day	48% 5% 15% 19% 13% 1	2904
February	1st to 10th	Day	52% 5% 13% 17% 11% 3	1710
	11th to 20th	Day	49% 4 11% 20% 13% 1	1742
	21st to end	Day	48% 6% 10% 22% 10% 5%	1570
March	1st to 10th	Day	57% 4 8% 15% 12% 3	3197
	11th to 20th	Day	49% 7% 13% 17% 11% 2	3480
	21st to end	Day	59% 3 5% 14% 15% 4	3816
April	1st to 10th	Day	53% 4 10% 16% 13% 3	2222
	11th to 20th	Day	47% 5% 10% 22% 14% 2	2442
	21st to end	Day	48% 5% 9% 18% 16% 4	2470
May	1st to 10th	Day	51% 8% 13% 18% 9% 1	4120
	11th to 20th	Day	46% 7% 15% 22% 9% 1	4085
	21st to end	Day	44% 9% 14% 19% 14% 1	4948
June	1st to 10th	Day	53% 6% 14% 18% 9% 1	2850
	11th to 20th	Day	46% 6% 11% 21% 15% 2	2850
	21st to end	Day	54% 7% 11% 15% 10% 2	2850
July	1st to 10th	Day	46% 7% 12% 23% 11% 1	4600
	11th to 20th	Day	41% 6% 17% 24% 11%	4365
	21st to end	Day	46% 7% 13% 21% 12% 1	4517
August	1st to 10th	Day	50% 5% 15% 23% 7%	4092
	11th to 20th	Day	46% 7% 18% 20% 8%	4084
	21st to end	Day	31% 7% 15% 27% 20% 1	4532
September	1st to 10th	Day	33% 6% 14% 26% 18% 2	2190
	11th to 20th	Day	34% 5% 11% 27% 19% 3	2090
	21st to end	Day	42% 5% 8% 27% 16% 1	2090
October	1st to 10th	Day	48% 8% 10% 22% 11% 1	3335
	11th to 20th	Day	32% 4 9% 35% 19%	3140
	21st to end	Day	34% 4 18% 24% 17% 3	3117
November	1st to 10th	Day	44% 6% 13% 23% 13% 1	1761
	11th to 20th	Day	42% 6% 11% 22% 17% 3	1628
	21st to end	Day	48% 4 14% 23% 9% 1	1520
December	1st to 10th	Day	53% 6% 11% 19% 11% 1	1468
	11th to 20th	Day	55% 3 11% 20% 10% 1	1668
	21st to end	Day	51% 6% 13% 18% 10% 3	2431
January	1st to 10th	Night	45% 4 13% 27% 8% 1	4479
	11th to 20th	Night	48% 6% 12% 21% 11% 2	4440
	21st to end	Night	51% 5% 11% 22% 10% 1	4751
February	1st to 10th	Night	50% 5% 13% 19% 11% 2	2470
	11th to 20th	Night	48% 5% 11% 19% 15% 3	2332
	21st to end	Night	47% 4 10% 21% 14% 4	1884
March	1st to 10th	Night	58% 3 8% 15% 12% 3	3656
	11th to 20th	Night	52% 9% 13% 14% 10% 1	3480
	21st to end	Night	59% 4 5% 17% 13% 2	3816
April	1st to 10th	Night	51% 5% 8% 16% 16% 3	1954
	11th to 20th	Night	50% 4 10% 20% 14% 2	1688
	21st to end	Night	53% 4 10% 16% 14% 3	1710
May	1st to 10th	Night	47% 6% 17% 21% 8% 1	2840
	11th to 20th	Night	49% 8% 18% 18% 7% 1	2814
	21st to end	Night	48% 8% 15% 20% 9% 1	2660
June	1st to 10th	Night	55% 7% 10% 20% 7% 1	1330
	11th to 20th	Night	47% 7% 12% 21% 11% 2	1330
	21st to end	Night	58% 6% 7% 18% 9% 2	1330
July	1st to 10th	Night	51% 8% 12% 19% 10%	2252
	11th to 20th	Night	47% 7% 14% 23% 9%	2472
	21st to end	Night	45% 8% 13% 21% 12% 1	2764
August	1st to 10th	Night	55% 7% 12% 19% 7%	2813
	11th to 20th	Night	49% 8% 15% 20% 8%	2809
	21st to end	Night	35% 8% 12% 25% 19% 1	3124
September	1st to 10th	Night	36% 6% 13% 28% 17% 1	1985
	11th to 20th	Night	36% 6% 12% 25% 19% 2	2090
	21st to end	Night	39% 5% 10% 29% 16% 1	2090
October	1st to 10th	Night	41% 6% 14% 24% 13% 1	3624
	11th to 20th	Night	33% 4 10% 29% 23% 1	3779
	21st to end	Night	38% 4 11% 29% 15% 3	4426
November	1st to 10th	Night	42% 6% 13% 24% 14% 1	2537
	11th to 20th	Night	45% 5% 10% 22% 16% 2	2557
	21st to end	Night	44% 7% 15% 20% 13% 2	2660
December	1st to 10th	Night	55% 4 10% 20% 11%	2707
	11th to 20th	Night	49% 4 11% 21% 14% 1	3532
	21st to end	Night	50% 5% 14% 18% 11% 2	5236

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	26% 27% 31% 13% 4	180
	11th to 20th	Day	29% 23% 37% 8% 3 1	180
	21st to end	Day	18% 26% 32% 21% 4	278
February	1st to 10th	Day	27% 22% 32% 16% 3	370
	11th to 20th	Day	26% 32% 31% 9% 2	399
	21st to end	Day	23% 26% 33% 16% 2	382
March	1st to 10th	Day	28% 27% 29% 13% 2	460
	11th to 20th	Day	24% 27% 29% 15% 3	460
	21st to end	Day	31% 23% 27% 13% 4 1	506
April	1st to 10th	Day	33% 24% 29% 10% 3 2	460
	11th to 20th	Day	29% 22% 33% 11% 4 1	452
	21st to end	Day	27% 20% 33% 15% 4 1	460
May	1st to 10th	Day	28% 23% 31% 13% 5%	463
	11th to 20th	Day	21% 19% 35% 19% 5% 1	487
	21st to end	Day	25% 17% 32% 17% 8%	669
June	1st to 10th	Day	25% 15% 30% 22% 7% 1	680
	11th to 20th	Day	24% 12% 30% 23% 9% 1	680
	21st to end	Day	30% 11% 28% 22% 7% 1	680
July	1st to 10th	Day	24% 9% 34% 21% 10% 1	624
	11th to 20th	Day	20% 6% 39% 25% 9% 1	484
	21st to end	Day	19% 10% 38% 25% 7% 1	532
August	1st to 10th	Day	14% 11% 36% 29% 9% 1	486
	11th to 20th	Day	22% 10% 29% 28% 10% 2	479
	21st to end	Day	16% 10% 34% 27% 10% 2	539
September	1st to 10th	Day	18% 10% 35% 27% 9% 1	490
	11th to 20th	Day	21% 10% 31% 23% 11% 4	490
	21st to end	Day	19% 15% 32% 23% 8% 4	490
October	1st to 10th	Day	18% 18% 29% 21% 12% 2	447
	11th to 20th	Day	20% 19% 31% 20% 8% 1	390
	21st to end	Day	28% 16% 32% 18% 4 1	429
November	1st to 10th	Day	25% 18% 29% 20% 6% 2	395
	11th to 20th	Day	25% 23% 30% 17% 4	370
	21st to end	Day	25% 25% 29% 17% 4	370
December	1st to 10th	Day	28% 21% 33% 14% 3	318
	11th to 20th	Day	36% 28% 25% 9% 2	180
	21st to end	Day	31% 33% 21% 10% 5%	198
January	1st to 10th	Night	23% 23% 34% 16% 3	772
	11th to 20th	Night	27% 21% 33% 16% 3	760
	21st to end	Night	19% 26% 33% 19% 3	836
February	1st to 10th	Night	24% 24% 32% 17% 3	760
	11th to 20th	Night	21% 29% 33% 14% 2 1	743
	21st to end	Night	23% 22% 33% 19% 3	628
March	1st to 10th	Night	25% 21% 35% 18% 1	760
	11th to 20th	Night	24% 20% 31% 20% 5%	760
	21st to end	Night	24% 20% 31% 18% 6% 1	836
April	1st to 10th	Night	30% 16% 33% 18% 3	755
	11th to 20th	Night	27% 14% 34% 21% 4	564
	21st to end	Night	29% 14% 33% 18% 6%	570
May	1st to 10th	Night	27% 10% 32% 24% 6% 1	570
	11th to 20th	Night	25% 11% 34% 25% 5%	562
	21st to end	Night	24% 9% 34% 25% 8% 1	506
June	1st to 10th	Night	28% 9% 26% 28% 7% 1	380
	11th to 20th	Night	24% 6% 30% 31% 9%	380
	21st to end	Night	34% 4 23% 33% 7%	380
July	1st to 10th	Night	20% 6% 30% 35% 9%	370
	11th to 20th	Night	23% 4 25% 37% 11% 1	368
	21st to end	Night	24% 3 27% 35% 11% 1	482
August	1st to 10th	Night	20% 5% 28% 35% 11%	568
	11th to 20th	Night	21% 5% 26% 37% 11%	562
	21st to end	Night	18% 5% 29% 32% 16% 1	627
September	1st to 10th	Night	16% 6% 33% 31% 13% 1	724
	11th to 20th	Night	19% 7% 29% 27% 14% 3	760
	21st to end	Night	20% 9% 30% 28% 11% 2	760
October	1st to 10th	Night	23% 9% 29% 26% 13% 1	760
	11th to 20th	Night	23% 13% 30% 23% 11% 1	760
	21st to end	Night	28% 18% 28% 22% 4	836
November	1st to 10th	Night	23% 15% 32% 23% 7% 1	780
	11th to 20th	Night	23% 22% 28% 19% 8%	801
	21st to end	Night	24% 23% 29% 18% 6%	850
December	1st to 10th	Night	31% 17% 34% 15% 4	850
	11th to 20th	Night	27% 26% 29% 16% 2	850
	21st to end	Night	28% 25% 27% 17% 2	935

Page generated at 2024-11-08 06:44:46. Version ac07

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