Biolab Boat Ramp
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Biolab Boat Ramp clear sky chart from 2005-11-06 to 2024-11-25.

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	7% 5% 2 7% 5% 5% 6% 5% 8% 10% 38%	101058
	Night	8% 6% 2 7% 5% 5% 5% 5% 7% 10% 41%	98370
Transparency	Day	19% 50% 12% 12% 6% 1	104771
	Night	21% 49% 11% 11% 6% 2	102796
Seeing	Day	8% 5% 19% 27% 24% 17%	15802
	Night	9% 4 17% 31% 30% 9%	25886

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% 8% 2 7% 5% 5% 5% 4 6% 6% 42%	2836
	11th to 20th	Day	17% 9% 3 7% 5% 4 4 4 6% 7% 32%	2840
	21st to end	Day	12% 6% 3 7% 5% 5% 5% 4 7% 7% 40%	3124
February	1st to 10th	Day	11% 6% 3 5% 5% 5% 4 5% 6% 8% 43%	1870
	11th to 20th	Day	7% 4 2 6% 5% 5% 4 4 6% 7% 51%	1865
	21st to end	Day	9% 6% 2 4 4 3 5% 3 6% 8% 48%	1727
March	1st to 10th	Day	6% 6% 3 9% 6% 6% 6% 5% 7% 10% 35%	3435
	11th to 20th	Day	5% 4 1 5% 4 3 4 3 7% 11% 53%	3480
	21st to end	Day	10% 5% 2 5% 4 3 4 5% 7% 9% 45%	3815
April	1st to 10th	Day	6% 4 2 5% 4 5% 5% 5% 7% 8% 49%	2090
	11th to 20th	Day	8% 4 2 7% 5% 5% 6% 5% 7% 10% 42%	2168
	21st to end	Day	5% 3 2 5% 5% 4 5% 5% 7% 10% 49%	2280
May	1st to 10th	Day	3 2 1 3 3 3 4 4 6% 11% 59%	3829
	11th to 20th	Day	8% 5% 3 8% 5% 6% 6% 6% 8% 10% 37%	4081
	21st to end	Day	4 4 2 5% 4 4 5% 4 8% 10% 51%	4476
June	1st to 10th	Day	11% 7% 3 7% 7% 7% 7% 5% 9% 9% 28%	2470
	11th to 20th	Day	5% 6% 2 8% 6% 7% 8% 7% 10% 11% 30%	2470
	21st to end	Day	7% 7% 3 7% 7% 6% 7% 6% 9% 11% 30%	2470
July	1st to 10th	Day	5% 5% 2 7% 5% 6% 7% 6% 9% 13% 34%	4120
	11th to 20th	Day	5% 4 2 6% 5% 6% 7% 6% 11% 14% 34%	4120
	21st to end	Day	4 5% 2 6% 6% 6% 8% 7% 10% 16% 30%	4466
August	1st to 10th	Day	5% 5% 3 8% 6% 7% 7% 7% 9% 14% 30%	4104
	11th to 20th	Day	4 4 2 7% 5% 6% 7% 6% 11% 13% 35%	3835
	21st to end	Day	6% 5% 3 8% 6% 6% 8% 6% 10% 15% 29%	3961
September	1st to 10th	Day	7% 6% 3 9% 7% 8% 8% 7% 9% 11% 25%	2090
	11th to 20th	Day	8% 7% 3 8% 7% 7% 7% 6% 9% 12% 26%	2090
	21st to end	Day	10% 6% 3 9% 7% 6% 8% 5% 8% 9% 29%	2090
October	1st to 10th	Day	12% 7% 3 8% 7% 6% 6% 4 7% 9% 32%	2005
	11th to 20th	Day	6% 6% 2 6% 6% 6% 5% 4 8% 9% 43%	1900
	21st to end	Day	9% 3 2 6% 4 4 5% 4 7% 9% 46%	2090
November	1st to 10th	Day	7% 5% 3 8% 6% 5% 6% 5% 7% 9% 39%	1957
	11th to 20th	Day	9% 6% 2 7% 6% 5% 5% 5% 6% 8% 41%	2000
	21st to end	Day	9% 6% 2 7% 5% 5% 5% 5% 7% 9% 40%	1917
December	1st to 10th	Day	7% 5% 3 7% 4 5% 5% 4 6% 8% 46%	1710
	11th to 20th	Day	11% 7% 3 7% 5% 5% 5% 3 6% 8% 40%	2153
	21st to end	Day	11% 7% 3 9% 6% 6% 6% 5% 7% 8% 32%	3124
January	1st to 10th	Night	11% 8% 3 7% 4 5% 5% 4 6% 7% 40%	4109
	11th to 20th	Night	16% 10% 3 8% 5% 5% 4 4 6% 8% 30%	4120
	21st to end	Night	10% 7% 3 7% 5% 5% 5% 5% 6% 8% 40%	4532
February	1st to 10th	Night	10% 7% 2 6% 4 4 4 4 6% 8% 44%	2306
	11th to 20th	Night	11% 3 2 6% 5% 3 4 4 6% 7% 50%	2199
	21st to end	Night	7% 3 1 5% 4 4 5% 4 5% 8% 54%	1727
March	1st to 10th	Night	11% 8% 3 8% 5% 5% 5% 3 6% 6% 40%	3418
	11th to 20th	Night	5% 3 1 3 3 4 4 4 8% 13% 52%	3480
	21st to end	Night	7% 6% 2 7% 4 5% 4 4 6% 8% 46%	3817
April	1st to 10th	Night	5% 4 1 5% 3 4 4 4 7% 9% 54%	2090
	11th to 20th	Night	5% 6% 2 6% 4 4 5% 4 6% 8% 48%	1957
	21st to end	Night	6% 4 2 5% 4 4 4 4 6% 8% 54%	1900
May	1st to 10th	Night	3 2 1 3 2 3 4 4 5% 10% 63%	3080
	11th to 20th	Night	7% 5% 2 7% 4 4 5% 5% 8% 11% 42%	2812
	21st to end	Night	4 4 2 6% 4 3 4 4 7% 9% 53%	3079
June	1st to 10th	Night	9% 7% 3 7% 6% 5% 6% 5% 8% 11% 32%	1710
	11th to 20th	Night	4 6% 3 7% 7% 8% 6% 5% 10% 12% 32%	1710
	21st to end	Night	7% 5% 3 8% 5% 5% 7% 5% 8% 12% 34%	1710
July	1st to 10th	Night	5% 5% 2 6% 5% 5% 6% 5% 8% 13% 39%	2840
	11th to 20th	Night	4 5% 2 6% 5% 5% 7% 6% 9% 16% 35%	2840
	21st to end	Night	4 6% 2 8% 6% 6% 7% 6% 9% 14% 32%	3087
August	1st to 10th	Night	4 5% 3 8% 6% 6% 7% 6% 7% 13% 36%	2825
	11th to 20th	Night	3 4 2 7% 5% 6% 7% 5% 9% 12% 39%	2962
	21st to end	Night	7% 6% 2 7% 5% 6% 7% 5% 10% 13% 32%	3689
September	1st to 10th	Night	7% 6% 4 7% 7% 7% 8% 7% 8% 11% 28%	2090
	11th to 20th	Night	8% 8% 4 10% 8% 6% 6% 5% 9% 11% 25%	2090
	21st to end	Night	10% 7% 3 8% 5% 6% 6% 5% 9% 9% 31%	2090
October	1st to 10th	Night	10% 7% 3 9% 6% 4 6% 5% 7% 8% 34%	2174
	11th to 20th	Night	6% 6% 2 6% 5% 5% 5% 4 6% 8% 47%	2280
	21st to end	Night	8% 5% 2 6% 5% 4 4 4 6% 9% 46%	2508
November	1st to 10th	Night	8% 6% 3 7% 6% 5% 5% 4 7% 8% 41%	2341
	11th to 20th	Night	8% 7% 2 7% 6% 5% 5% 4 7% 9% 41%	2400
	21st to end	Night	9% 6% 3 7% 5% 6% 7% 5% 6% 8% 38%	2354
December	1st to 10th	Night	7% 4 2 5% 5% 5% 6% 4 7% 9% 46%	2470
	11th to 20th	Night	12% 9% 3 6% 5% 4 5% 3 6% 7% 41%	3042
	21st to end	Night	12% 9% 3 8% 6% 6% 5% 4 6% 7% 34%	4532

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	30% 38% 5% 9% 15% 3	2837
	11th to 20th	Day	39% 38% 4 9% 8% 2	2840
	21st to end	Day	27% 41% 5% 11% 11% 5%	3124
February	1st to 10th	Day	12% 66% 6% 7% 6% 2	1870
	11th to 20th	Day	9% 64% 4 10% 11% 3	1875
	21st to end	Day	13% 66% 4 6% 8% 3	1727
March	1st to 10th	Day	31% 44% 12% 9% 3 1	3435
	11th to 20th	Day	15% 40% 10% 21% 14% 1	3480
	21st to end	Day	23% 41% 6% 19% 7% 4	3815
April	1st to 10th	Day	10% 66% 6% 10% 6% 2	2090
	11th to 20th	Day	10% 67% 4 8% 8% 2	2168
	21st to end	Day	8% 66% 5% 10% 9% 2	2280
May	1st to 10th	Day	8% 45% 12% 23% 9% 3	3864
	11th to 20th	Day	26% 43% 11% 15% 5% 1	4085
	21st to end	Day	9% 42% 9% 29% 10% 1	4489
June	1st to 10th	Day	14% 68% 11% 7% 1	2470
	11th to 20th	Day	15% 70% 8% 8%	2470
	21st to end	Day	10% 69% 13% 6% 2	2470
July	1st to 10th	Day	17% 43% 25% 12% 3	4055
	11th to 20th	Day	18% 45% 32% 5%	4051
	21st to end	Day	21% 47% 25% 7%	4324
August	1st to 10th	Day	25% 44% 22% 7% 1	4091
	11th to 20th	Day	17% 46% 19% 12% 6%	3874
	21st to end	Day	20% 45% 23% 11% 1	3961
September	1st to 10th	Day	19% 68% 7% 3 3	2090
	11th to 20th	Day	17% 63% 11% 7% 1	2090
	21st to end	Day	15% 63% 9% 8% 4 1	2090
October	1st to 10th	Day	38% 42% 11% 6% 2	3330
	11th to 20th	Day	16% 41% 6% 16% 18% 3	3140
	21st to end	Day	12% 39% 6% 19% 22% 3	3428
November	1st to 10th	Day	16% 59% 8% 9% 6% 1	1957
	11th to 20th	Day	20% 58% 4 9% 6% 3	2000
	21st to end	Day	17% 59% 4 10% 6% 3	1917
December	1st to 10th	Day	14% 60% 7% 12% 5% 1	1710
	11th to 20th	Day	22% 48% 5% 8% 12% 6%	2150
	21st to end	Day	34% 39% 7% 11% 5% 3	3124
January	1st to 10th	Night	31% 37% 6% 11% 11% 2	4109
	11th to 20th	Night	39% 37% 6% 11% 5% 1	4120
	21st to end	Night	26% 40% 8% 11% 10% 5%	4532
February	1st to 10th	Night	12% 66% 6% 9% 5% 2	2306
	11th to 20th	Night	10% 64% 4 8% 11% 2	2200
	21st to end	Night	10% 66% 6% 8% 8% 3	1727
March	1st to 10th	Night	36% 42% 10% 8% 4 1	3418
	11th to 20th	Night	13% 41% 18% 18% 9% 1	3480
	21st to end	Night	25% 42% 5% 12% 12% 3	3817
April	1st to 10th	Night	10% 66% 7% 10% 5% 3	2090
	11th to 20th	Night	11% 67% 5% 11% 5% 2	1957
	21st to end	Night	9% 66% 5% 11% 8% 2	1900
May	1st to 10th	Night	8% 43% 15% 23% 7% 3	3110
	11th to 20th	Night	21% 41% 15% 17% 5%	2813
	21st to end	Night	10% 41% 10% 29% 10%	3087
June	1st to 10th	Night	15% 67% 12% 7% 1	1710
	11th to 20th	Night	14% 70% 9% 7%	1710
	21st to end	Night	14% 67% 11% 7% 2	1710
July	1st to 10th	Night	17% 44% 25% 14% 1	2795
	11th to 20th	Night	18% 45% 33% 4	2786
	21st to end	Night	27% 44% 22% 6%	2988
August	1st to 10th	Night	25% 42% 26% 6% 1	2814
	11th to 20th	Night	19% 44% 19% 13% 4	2989
	21st to end	Night	21% 44% 25% 8% 1	3689
September	1st to 10th	Night	18% 65% 8% 5% 3	2090
	11th to 20th	Night	17% 64% 11% 8% 1	2090
	21st to end	Night	16% 63% 7% 9% 4 1	2090
October	1st to 10th	Night	43% 41% 8% 6% 2	3629
	11th to 20th	Night	19% 40% 5% 16% 16% 3	3779
	21st to end	Night	17% 39% 6% 15% 20% 2	4120
November	1st to 10th	Night	18% 58% 7% 10% 6% 2	2341
	11th to 20th	Night	19% 59% 5% 7% 7% 3	2400
	21st to end	Night	18% 59% 5% 10% 5% 3	2354
December	1st to 10th	Night	13% 61% 7% 14% 4	2470
	11th to 20th	Night	21% 49% 4 10% 10% 6%	3044
	21st to end	Night	34% 40% 8% 12% 5% 1	4532

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	16% 7% 42% 25% 9% 2	270
	11th to 20th	Day	6% 11% 40% 23% 16% 4	270
	21st to end	Day	15% 13% 43% 23% 6%	297
February	1st to 10th	Day	12% 12% 35% 24% 15% 1	270
	11th to 20th	Day	9% 7% 36% 33% 12% 3	287
	21st to end	Day	8% 6% 30% 34% 20% 3	382
March	1st to 10th	Day	3 10% 40% 33% 13% 2	460
	11th to 20th	Day	8% 7% 31% 31% 19% 3	460
	21st to end	Day	7% 7% 29% 34% 20% 4	506
April	1st to 10th	Day	8% 8% 33% 33% 14% 3	460
	11th to 20th	Day	9% 8% 28% 29% 22% 5%	452
	21st to end	Day	5% 4 24% 35% 22% 8%	460
May	1st to 10th	Day	5% 4 21% 35% 25% 9%	463
	11th to 20th	Day	9% 4 14% 33% 25% 15%	487
	21st to end	Day	7% 2 10% 29% 29% 22%	529
June	1st to 10th	Day	13% 3 10% 25% 29% 20%	490
	11th to 20th	Day	5% 2 9% 22% 32% 30%	490
	21st to end	Day	8% 2 4 14% 35% 36%	490
July	1st to 10th	Day	6% 1 6% 10% 31% 45%	485
	11th to 20th	Day	5% 1 2 12% 34% 45%	484
	21st to end	Day	7% 1 3 17% 31% 41%	532
August	1st to 10th	Day	7% 2 5% 15% 35% 36%	486
	11th to 20th	Day	3 1 5% 11% 31% 50%	479
	21st to end	Day	10% 1 6% 19% 31% 34%	539
September	1st to 10th	Day	9% 2 6% 17% 33% 34%	490
	11th to 20th	Day	10% 3 8% 23% 30% 26%	490
	21st to end	Day	11% 1 8% 26% 30% 23%	490
October	1st to 10th	Day	18% 3 17% 34% 20% 8%	490
	11th to 20th	Day	6% 5% 19% 35% 27% 8%	490
	21st to end	Day	6% 4 20% 38% 24% 6%	539
November	1st to 10th	Day	8% 6% 22% 35% 23% 5%	495
	11th to 20th	Day	12% 6% 24% 34% 20% 3	500
	21st to end	Day	11% 5% 27% 35% 20% 2	453
December	1st to 10th	Day	6% 7% 33% 37% 13% 4	270
	11th to 20th	Day	9% 10% 31% 32% 16% 1	270
	21st to end	Day	7% 7% 30% 36% 16% 3	297
January	1st to 10th	Night	12% 9% 26% 37% 15% 1	760
	11th to 20th	Night	10% 8% 26% 37% 17% 2	760
	21st to end	Night	14% 8% 33% 35% 9%	836
February	1st to 10th	Night	13% 7% 27% 37% 16% 1	760
	11th to 20th	Night	12% 7% 27% 39% 13% 1	743
	21st to end	Night	8% 5% 31% 43% 14%	628
March	1st to 10th	Night	5% 6% 32% 40% 16% 1	760
	11th to 20th	Night	8% 6% 23% 42% 19% 2	760
	21st to end	Night	8% 5% 28% 37% 22% 1	836
April	1st to 10th	Night	6% 5% 28% 41% 19% 2	760
	11th to 20th	Night	8% 5% 26% 37% 23% 2	751
	21st to end	Night	6% 3 21% 44% 24% 3	760
May	1st to 10th	Night	6% 3 15% 47% 27% 2	736
	11th to 20th	Night	8% 2 14% 32% 37% 7%	561
	21st to end	Night	8% 1 5% 26% 47% 12%	617
June	1st to 10th	Night	12% 1 7% 28% 43% 10%	570
	11th to 20th	Night	6% 2 6% 21% 44% 22%	570
	21st to end	Night	8% 2 5% 17% 44% 25%	570
July	1st to 10th	Night	7% 1 3 12% 48% 28%	555
	11th to 20th	Night	6% 2 2 9% 51% 31%	552
	21st to end	Night	6% 1 1 12% 50% 31%	624
August	1st to 10th	Night	5% 2 2 10% 50% 29%	567
	11th to 20th	Night	4 1 3 12% 49% 32%	663
	21st to end	Night	12% 1 4 16% 41% 25%	836
September	1st to 10th	Night	9% 2 6% 14% 46% 24%	760
	11th to 20th	Night	9% 3 5% 20% 46% 17%	760
	21st to end	Night	11% 2 6% 21% 43% 16%	760
October	1st to 10th	Night	13% 3 12% 33% 32% 8%	760
	11th to 20th	Night	8% 3 13% 32% 35% 8%	760
	21st to end	Night	11% 2 16% 34% 32% 5%	836
November	1st to 10th	Night	10% 4 19% 34% 29% 4	780
	11th to 20th	Night	10% 4 22% 38% 24% 2	800
	21st to end	Night	10% 3 26% 39% 20% 2	779
December	1st to 10th	Night	7% 4 25% 34% 27% 3	760
	11th to 20th	Night	12% 8% 21% 34% 22% 4	760
	21st to end	Night	12% 5% 24% 36% 21% 2	836

Page generated at 2024-11-22 08:02:25. Version ac07

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