Berry Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Berry Lake clear sky chart from 2005-11-06 to 2024-11-30.

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	12% 11% 4 10% 6% 5% 5% 4 5% 7% 31%	101226
	Night	13% 12% 5% 10% 6% 5% 5% 4 5% 6% 31%	98411
Transparency	Day	50% 6% 11% 20% 12% 1	104770
	Night	52% 7% 11% 19% 10% 1	102994
Seeing	Day	18% 14% 30% 23% 11% 4	15833
	Night	18% 10% 31% 29% 11% 1	25867

By Month

Percentage Cloud Cover SE (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	11% 19% 12% 19% 7% 8% 5% 3 3 3 9%	2527
	11th to 20th	Day	13% 16% 6% 21% 12% 11% 7% 3 3 3 5%	2530
	21st to end	Day	18% 20% 11% 15% 7% 5% 5% 3 4 4 8%	2783
February	1st to 10th	Day	9% 17% 6% 12% 14% 7% 6% 5% 4 5% 16%	1662
	11th to 20th	Day	10% 14% 6% 16% 13% 7% 4 3 5% 5% 16%	1848
	21st to end	Day	9% 18% 5% 14% 9% 5% 5% 4 4 6% 20%	1570
March	1st to 10th	Day	11% 13% 7% 9% 6% 5% 5% 4 5% 5% 29%	3120
	11th to 20th	Day	9% 8% 6% 17% 7% 5% 4 4 6% 6% 28%	3402
	21st to end	Day	16% 12% 5% 14% 7% 6% 5% 3 4 4 24%	3937
April	1st to 10th	Day	15% 16% 5% 9% 5% 5% 3 3 5% 6% 28%	2280
	11th to 20th	Day	18% 13% 4 7% 5% 4 3 3 4 6% 33%	2344
	21st to end	Day	15% 11% 4 9% 5% 5% 5% 4 5% 7% 31%	2470
May	1st to 10th	Day	14% 9% 3 7% 5% 4 5% 4 5% 8% 37%	4082
	11th to 20th	Day	11% 7% 2 6% 5% 5% 5% 4 5% 7% 43%	4167
	21st to end	Day	10% 7% 3 5% 4 4 5% 4 6% 8% 43%	4824
June	1st to 10th	Day	11% 6% 3 7% 6% 4 4 4 6% 7% 42%	2660
	11th to 20th	Day	12% 7% 2 7% 4 5% 4 4 6% 9% 40%	2660
	21st to end	Day	12% 7% 3 7% 6% 4 5% 5% 6% 7% 39%	2660
July	1st to 10th	Day	13% 7% 3 8% 5% 5% 5% 4 7% 8% 35%	4440
	11th to 20th	Day	6% 5% 2 6% 5% 5% 6% 4 7% 10% 45%	4440
	21st to end	Day	7% 6% 2 7% 6% 5% 6% 4 6% 9% 43%	4813
August	1st to 10th	Day	10% 5% 3 7% 5% 5% 6% 5% 8% 9% 37%	4201
	11th to 20th	Day	12% 6% 2 6% 4 5% 5% 4 5% 7% 44%	4044
	21st to end	Day	10% 6% 2 7% 5% 5% 5% 4 7% 7% 41%	4321
September	1st to 10th	Day	11% 6% 2 6% 5% 6% 5% 5% 6% 7% 41%	2247
	11th to 20th	Day	12% 5% 3 6% 4 4 4 4 5% 8% 46%	2090
	21st to end	Day	13% 8% 3 7% 6% 5% 5% 3 5% 8% 37%	2090
October	1st to 10th	Day	16% 9% 3 7% 4 4 4 3 4 6% 40%	2090
	11th to 20th	Day	19% 14% 5% 9% 5% 5% 5% 3 5% 5% 23%	1817
	21st to end	Day	19% 13% 4 11% 7% 5% 6% 4 5% 5% 20%	1881
November	1st to 10th	Day	13% 15% 4 8% 5% 5% 5% 4 5% 7% 30%	1762
	11th to 20th	Day	13% 17% 8% 12% 8% 5% 5% 4 5% 6% 19%	1800
	21st to end	Day	16% 20% 8% 15% 6% 4 4 3 3 5% 16%	1792
December	1st to 10th	Day	13% 19% 10% 18% 7% 5% 4 4 4 5% 12%	1336
	11th to 20th	Day	13% 17% 7% 16% 8% 8% 5% 4 5% 5% 13%	1753
	21st to end	Day	19% 24% 9% 17% 7% 4 4 2 3 3 8%	2783
January	1st to 10th	Night	14% 18% 10% 18% 6% 5% 4 3 4 4 15%	4428
	11th to 20th	Night	10% 16% 6% 20% 11% 11% 7% 3 4 4 8%	4440
	21st to end	Night	15% 20% 9% 18% 7% 5% 5% 4 4 4 9%	4884
February	1st to 10th	Night	9% 13% 6% 15% 11% 8% 7% 5% 5% 5% 17%	2514
	11th to 20th	Night	11% 12% 5% 14% 9% 6% 6% 5% 6% 6% 20%	2218
	21st to end	Night	13% 13% 4 11% 9% 6% 6% 4 5% 6% 24%	1884
March	1st to 10th	Night	14% 9% 4 9% 4 4 4 3 5% 6% 37%	3733
	11th to 20th	Night	8% 9% 5% 9% 5% 5% 5% 4 6% 7% 37%	3557
	21st to end	Night	13% 12% 6% 11% 6% 5% 4 4 4 6% 28%	3722
April	1st to 10th	Night	13% 12% 6% 8% 6% 4 5% 4 6% 7% 31%	1900
	11th to 20th	Night	19% 9% 3 7% 4 4 4 3 5% 6% 36%	1784
	21st to end	Night	15% 9% 3 8% 5% 4 3 3 5% 6% 38%	1710
May	1st to 10th	Night	13% 8% 2 6% 5% 5% 4 4 6% 6% 40%	2813
	11th to 20th	Night	13% 7% 2 6% 4 4 5% 4 6% 8% 41%	2728
	21st to end	Night	15% 6% 3 5% 4 3 4 3 6% 7% 44%	2743
June	1st to 10th	Night	13% 6% 3 6% 4 3 4 4 7% 8% 43%	1520
	11th to 20th	Night	9% 6% 2 6% 5% 4 5% 4 7% 10% 43%	1520
	21st to end	Night	9% 7% 2 7% 4 4 4 4 5% 8% 46%	1520
July	1st to 10th	Night	9% 8% 3 7% 4 5% 5% 4 7% 8% 40%	2530
	11th to 20th	Night	5% 4 2 4 3 4 5% 4 6% 8% 55%	2530
	21st to end	Night	6% 5% 2 6% 4 4 5% 4 6% 8% 50%	2750
August	1st to 10th	Night	10% 5% 2 5% 5% 4 5% 5% 7% 8% 44%	2728
	11th to 20th	Night	11% 6% 2 5% 3 4 4 3 5% 7% 52%	2785
	21st to end	Night	8% 6% 2 6% 4 4 5% 4 6% 7% 48%	3333
September	1st to 10th	Night	10% 5% 2 5% 4 3 4 3 5% 7% 52%	1914
	11th to 20th	Night	11% 5% 2 5% 3 3 4 4 6% 7% 51%	2090
	21st to end	Night	13% 8% 3 8% 4 3 4 3 6% 8% 40%	2090
October	1st to 10th	Night	16% 7% 3 6% 4 3 3 3 4 6% 44%	2090
	11th to 20th	Night	15% 12% 3 8% 5% 5% 4 4 5% 7% 31%	2359
	21st to end	Night	20% 14% 4 8% 5% 4 4 4 5% 6% 27%	2717
November	1st to 10th	Night	10% 13% 4 9% 6% 4 5% 3 5% 7% 32%	2536
	11th to 20th	Night	13% 14% 6% 13% 7% 6% 6% 4 5% 6% 20%	2600
	21st to end	Night	14% 18% 6% 12% 6% 5% 5% 3 4 6% 20%	2599
December	1st to 10th	Night	13% 18% 7% 15% 9% 6% 5% 4 4 5% 14%	2835
	11th to 20th	Night	12% 17% 6% 19% 8% 6% 6% 4 5% 5% 13%	3423
	21st to end	Night	21% 25% 7% 15% 5% 5% 4 2 3 3 10%	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	77% 9% 6% 5% 2	2528
	11th to 20th	Day	86% 5% 4 4 1	2530
	21st to end	Day	79% 7% 8% 4 2	2783
February	1st to 10th	Day	71% 6% 7% 13% 3	1662
	11th to 20th	Day	69% 5% 9% 12% 5%	1858
	21st to end	Day	65% 6% 10% 14% 5% 1	1570
March	1st to 10th	Day	55% 6% 11% 19% 9% 1	3120
	11th to 20th	Day	54% 6% 13% 17% 8% 1	3402
	21st to end	Day	61% 6% 9% 16% 7% 1	3937
April	1st to 10th	Day	57% 4 10% 17% 11%	2280
	11th to 20th	Day	52% 5% 9% 18% 15% 2	2344
	21st to end	Day	51% 7% 12% 14% 14% 2	2470
May	1st to 10th	Day	44% 6% 11% 20% 18% 2	4120
	11th to 20th	Day	38% 8% 12% 25% 16% 1	4171
	21st to end	Day	37% 7% 12% 21% 20% 2	4837
June	1st to 10th	Day	39% 7% 11% 25% 16% 2	2660
	11th to 20th	Day	39% 6% 12% 22% 19% 1	2660
	21st to end	Day	42% 7% 13% 24% 14% 1	2660
July	1st to 10th	Day	45% 6% 12% 22% 14% 2	4371
	11th to 20th	Day	31% 7% 13% 30% 17% 2	4365
	21st to end	Day	36% 8% 12% 24% 19% 2	4662
August	1st to 10th	Day	39% 8% 12% 27% 14% 1	4186
	11th to 20th	Day	38% 7% 12% 27% 16% 1	4083
	21st to end	Day	40% 8% 12% 26% 14% 1	4320
September	1st to 10th	Day	41% 7% 12% 24% 15% 1	2247
	11th to 20th	Day	36% 7% 13% 28% 15% 1	2090
	21st to end	Day	44% 6% 13% 26% 11%	2090
October	1st to 10th	Day	31% 5% 8% 34% 20% 2	3480
	11th to 20th	Day	51% 5% 9% 20% 14%	2981
	21st to end	Day	60% 6% 12% 17% 5%	3081
November	1st to 10th	Day	52% 8% 10% 20% 9%	1762
	11th to 20th	Day	65% 7% 11% 12% 5%	1800
	21st to end	Day	72% 4 11% 9% 3	1792
December	1st to 10th	Day	76% 6% 7% 9% 2	1336
	11th to 20th	Day	73% 8% 10% 8% 2	1749
	21st to end	Day	83% 4 6% 5% 3	2783
January	1st to 10th	Night	73% 6% 9% 10% 2	4428
	11th to 20th	Night	81% 5% 6% 6% 2	4440
	21st to end	Night	78% 7% 8% 5% 2	4884
February	1st to 10th	Night	67% 7% 7% 13% 5% 1	2514
	11th to 20th	Night	62% 8% 9% 14% 5%	2219
	21st to end	Night	61% 6% 12% 14% 6% 1	1884
March	1st to 10th	Night	47% 7% 15% 23% 9% 1	3733
	11th to 20th	Night	43% 8% 14% 23% 11% 1	3557
	21st to end	Night	55% 7% 11% 19% 7% 1	3722
April	1st to 10th	Night	51% 8% 8% 19% 14% 1	1900
	11th to 20th	Night	48% 6% 8% 21% 15% 2	1784
	21st to end	Night	46% 6% 11% 20% 15% 2	1710
May	1st to 10th	Night	42% 7% 13% 18% 17% 3	2840
	11th to 20th	Night	39% 7% 10% 29% 13% 1	2729
	21st to end	Night	39% 7% 12% 21% 17% 5%	2751
June	1st to 10th	Night	37% 7% 11% 25% 17% 1	1520
	11th to 20th	Night	36% 7% 13% 23% 20% 1	1520
	21st to end	Night	36% 7% 12% 27% 16% 2	1520
July	1st to 10th	Night	39% 7% 12% 25% 12% 5%	2490
	11th to 20th	Night	24% 6% 15% 35% 19% 1	2482
	21st to end	Night	31% 7% 16% 25% 20% 1	2662
August	1st to 10th	Night	33% 8% 16% 28% 14% 1	2719
	11th to 20th	Night	32% 5% 15% 31% 16%	2812
	21st to end	Night	33% 8% 13% 26% 19% 1	3333
September	1st to 10th	Night	30% 7% 13% 29% 19% 2	1914
	11th to 20th	Night	31% 7% 14% 34% 14% 1	2090
	21st to end	Night	42% 6% 13% 28% 10% 1	2090
October	1st to 10th	Night	32% 4 11% 36% 16% 1	3480
	11th to 20th	Night	44% 6% 10% 25% 15% 1	3921
	21st to end	Night	49% 5% 12% 26% 8%	4467
November	1st to 10th	Night	51% 7% 12% 20% 10% 1	2536
	11th to 20th	Night	62% 8% 12% 12% 6% 1	2600
	21st to end	Night	66% 6% 13% 11% 2 1	2599
December	1st to 10th	Night	72% 7% 8% 10% 3	2835
	11th to 20th	Night	73% 8% 10% 7% 3	3425
	21st to end	Night	80% 5% 8% 4 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	21% 19% 33% 20% 7%	270
	11th to 20th	Day	27% 16% 36% 17% 3	270
	21st to end	Day	25% 15% 36% 18% 6%	297
February	1st to 10th	Day	19% 26% 34% 14% 5% 1	270
	11th to 20th	Day	22% 25% 37% 14% 2	270
	21st to end	Day	22% 34% 35% 8% 1	225
March	1st to 10th	Day	21% 28% 37% 12% 2	270
	11th to 20th	Day	24% 15% 30% 20% 9% 1	408
	21st to end	Day	27% 16% 28% 21% 7% 1	506
April	1st to 10th	Day	24% 17% 38% 17% 4 1	460
	11th to 20th	Day	30% 16% 30% 14% 7% 4	452
	21st to end	Day	24% 14% 28% 24% 8% 2	460
May	1st to 10th	Day	23% 19% 29% 18% 8% 3	463
	11th to 20th	Day	18% 11% 31% 25% 11% 4	534
	21st to end	Day	14% 11% 30% 29% 13% 3	734
June	1st to 10th	Day	11% 14% 35% 25% 12% 3	680
	11th to 20th	Day	16% 12% 32% 26% 11% 3	680
	21st to end	Day	14% 10% 33% 28% 11% 3	680
July	1st to 10th	Day	8% 7% 28% 31% 20% 6%	671
	11th to 20th	Day	10% 8% 26% 32% 17% 7%	668
	21st to end	Day	9% 7% 30% 30% 17% 7%	739
August	1st to 10th	Day	10% 6% 24% 27% 23% 10%	545
	11th to 20th	Day	11% 5% 20% 30% 19% 14%	479
	21st to end	Day	13% 8% 22% 32% 18% 7%	539
September	1st to 10th	Day	15% 9% 24% 27% 17% 9%	490
	11th to 20th	Day	10% 8% 22% 28% 21% 11%	490
	21st to end	Day	20% 10% 21% 27% 17% 6%	490
October	1st to 10th	Day	21% 13% 28% 21% 16% 2	490
	11th to 20th	Day	27% 16% 31% 22% 3 1	390
	21st to end	Day	27% 21% 34% 14% 3 1	330
November	1st to 10th	Day	25% 17% 37% 13% 8%	300
	11th to 20th	Day	25% 23% 36% 13% 3	300
	21st to end	Day	25% 22% 34% 14% 3 1	299
December	1st to 10th	Day	30% 18% 34% 12% 4 2	183
	11th to 20th	Day	26% 22% 37% 13% 2	204
	21st to end	Day	27% 24% 35% 13% 1 1	297
January	1st to 10th	Night	20% 14% 36% 22% 7% 1	950
	11th to 20th	Night	22% 15% 34% 22% 7% 1	950
	21st to end	Night	18% 9% 39% 27% 6%	1045
February	1st to 10th	Night	16% 14% 39% 26% 4	817
	11th to 20th	Night	18% 15% 37% 25% 6%	743
	21st to end	Night	21% 16% 38% 20% 4	628
March	1st to 10th	Night	17% 13% 35% 24% 10% 1	760
	11th to 20th	Night	17% 12% 37% 26% 7%	760
	21st to end	Night	20% 10% 34% 28% 6% 1	779
April	1st to 10th	Night	19% 12% 38% 26% 5% 1	570
	11th to 20th	Night	24% 12% 32% 24% 7%	563
	21st to end	Night	19% 11% 31% 30% 8% 1	570
May	1st to 10th	Night	16% 9% 35% 31% 9%	570
	11th to 20th	Night	18% 7% 31% 33% 11% 1	561
	21st to end	Night	14% 5% 30% 35% 15% 1	617
June	1st to 10th	Night	14% 6% 32% 34% 12% 1	570
	11th to 20th	Night	11% 6% 30% 35% 16% 1	570
	21st to end	Night	12% 6% 25% 39% 16% 1	570
July	1st to 10th	Night	7% 2 22% 44% 23% 2	555
	11th to 20th	Night	7% 4 23% 40% 23% 4	552
	21st to end	Night	10% 2 22% 41% 24% 1	624
August	1st to 10th	Night	8% 2 22% 46% 20% 2	567
	11th to 20th	Night	8% 4 17% 38% 28% 5%	564
	21st to end	Night	10% 5% 22% 36% 26% 1	627
September	1st to 10th	Night	12% 3 22% 37% 21% 4	584
	11th to 20th	Night	12% 5% 22% 35% 24% 3	760
	21st to end	Night	17% 8% 24% 32% 15% 4	760
October	1st to 10th	Night	20% 8% 27% 31% 14% 1	760
	11th to 20th	Night	22% 12% 29% 27% 8% 1	760
	21st to end	Night	28% 12% 28% 25% 7%	836
November	1st to 10th	Night	18% 14% 33% 27% 7% 1	780
	11th to 20th	Night	22% 16% 33% 23% 5%	800
	21st to end	Night	23% 15% 35% 24% 3	800
December	1st to 10th	Night	22% 15% 35% 24% 4	950
	11th to 20th	Night	20% 16% 40% 19% 5% 1	950
	21st to end	Night	28% 15% 33% 23% 2	1045

Page generated at 2024-11-27 17:30:55. Version ac07

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