Gooseberry Island
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gooseberry Island clear sky chart from 2005-11-06 to 2026-03-18.

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	17% 9% 3 6% 4 4 4 3 5% 7% 40%	130616
	Night	18% 9% 3 6% 4 4 4 3 5% 6% 39%	130848
Transparency	Day	45% 5% 12% 21% 15% 2	134177
	Night	46% 4 11% 21% 16% 3	135374
Seeing	Day	20% 11% 29% 27% 11% 2	16866
	Night	22% 12% 29% 26% 10% 1	25878

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	11% 9% 3 6% 4 3 3 3 5% 7% 46%	4661
	11th to 20th	Day	16% 8% 3 5% 3 3 3 2 4 4 47%	4650
	21st to end	Day	15% 9% 3 6% 3 3 3 2 4 5% 46%	5142
February	1st to 10th	Day	18% 8% 2 6% 4 4 5% 4 5% 7% 36%	2032
	11th to 20th	Day	15% 8% 3 5% 4 4 4 3 6% 6% 42%	2048
	21st to end	Day	19% 9% 3 6% 3 3 3 4 5% 6% 39%	1730
March	1st to 10th	Day	21% 10% 2 5% 4 3 3 3 4 5% 40%	4576
	11th to 20th	Day	14% 10% 3 5% 3 3 4 3 5% 7% 44%	4885
	21st to end	Day	25% 9% 2 7% 4 4 4 3 4 5% 34%	5712
April	1st to 10th	Day	19% 9% 2 5% 3 4 3 3 5% 7% 39%	2400
	11th to 20th	Day	19% 8% 2 4 4 4 4 4 5% 7% 41%	2384
	21st to end	Day	20% 6% 2 6% 4 4 4 4 6% 6% 38%	2600
May	1st to 10th	Day	27% 12% 4 8% 4 3 3 3 5% 7% 25%	5886
	11th to 20th	Day	21% 10% 3 7% 4 4 4 3 4 6% 34%	5861
	21st to end	Day	20% 10% 4 7% 4 4 4 3 5% 7% 32%	6872
June	1st to 10th	Day	19% 8% 2 6% 4 5% 5% 4 6% 9% 33%	2800
	11th to 20th	Day	17% 6% 2 5% 4 4 4 5% 6% 8% 38%	2800
	21st to end	Day	14% 8% 3 5% 4 5% 4 4 6% 9% 38%	2800
July	1st to 10th	Day	19% 11% 3 8% 4 4 4 3 5% 8% 31%	6360
	11th to 20th	Day	13% 11% 4 7% 5% 4 5% 4 6% 10% 32%	6360
	21st to end	Day	15% 7% 3 6% 4 3 4 4 5% 7% 43%	6846
August	1st to 10th	Day	17% 8% 3 7% 5% 5% 5% 4 5% 7% 35%	4235
	11th to 20th	Day	12% 7% 2 7% 4 4 4 4 6% 8% 42%	4111
	21st to end	Day	7% 4 1 5% 3 4 5% 4 7% 10% 49%	4312
September	1st to 10th	Day	14% 7% 2 5% 4 3 4 3 5% 6% 46%	2375
	11th to 20th	Day	12% 6% 1 4 3 3 3 3 4 7% 52%	2200
	21st to end	Day	20% 7% 2 6% 4 3 4 4 5% 5% 40%	2200
October	1st to 10th	Day	20% 6% 2 5% 3 3 3 3 4 4 45%	2200
	11th to 20th	Day	16% 6% 2 5% 3 3 3 3 4 6% 48%	1987
	21st to end	Day	17% 5% 2 7% 3 4 3 3 5% 7% 44%	1980
November	1st to 10th	Day	16% 6% 2 6% 3 4 3 2 4 5% 47%	1851
	11th to 20th	Day	16% 6% 2 5% 4 3 4 3 5% 6% 46%	1890
	21st to end	Day	18% 7% 2 6% 4 4 4 3 4 6% 42%	1890
December	1st to 10th	Day	15% 8% 2 6% 4 3 3 3 4 6% 46%	2866
	11th to 20th	Day	18% 8% 3 5% 3 3 2 2 4 4 48%	3066
	21st to end	Day	20% 12% 3 7% 4 3 3 2 4 5% 37%	4048
January	1st to 10th	Night	15% 6% 2 5% 3 3 3 3 4 5% 50%	8234
	11th to 20th	Night	17% 10% 3 7% 4 4 4 3 4 5% 40%	8235
	21st to end	Night	15% 10% 3 7% 5% 4 4 3 5% 5% 37%	9024
February	1st to 10th	Night	16% 9% 3 7% 5% 4 3 3 4 7% 39%	2585
	11th to 20th	Night	19% 8% 2 5% 4 3 3 3 5% 7% 39%	2458
	21st to end	Night	18% 9% 2 7% 5% 4 4 3 5% 5% 38%	2076
March	1st to 10th	Night	23% 9% 2 5% 3 4 4 3 5% 6% 38%	5484
	11th to 20th	Night	17% 10% 3 7% 4 4 4 3 4 5% 38%	5228
	21st to end	Night	23% 9% 3 7% 4 4 4 3 4 5% 33%	5204
April	1st to 10th	Night	19% 10% 3 7% 4 3 4 3 4 6% 37%	2000
	11th to 20th	Night	19% 8% 3 7% 4 4 4 4 4 6% 38%	1963
	21st to end	Night	21% 7% 4 7% 5% 4 3 3 4 4 39%	1800
May	1st to 10th	Night	27% 13% 4 7% 4 4 3 3 5% 6% 24%	4054
	11th to 20th	Night	22% 13% 4 7% 4 3 4 3 5% 6% 28%	4033
	21st to end	Night	22% 10% 5% 8% 4 4 4 4 5% 7% 26%	4044
June	1st to 10th	Night	19% 11% 3 6% 2 4 5% 3 6% 8% 33%	1600
	11th to 20th	Night	20% 7% 3 5% 4 3 3 3 5% 7% 39%	1600
	21st to end	Night	18% 10% 2 6% 3 3 4 4 6% 9% 35%	1600
July	1st to 10th	Night	23% 14% 3 5% 4 4 4 3 5% 7% 29%	3600
	11th to 20th	Night	16% 13% 4 7% 4 4 5% 3 6% 9% 29%	3600
	21st to end	Night	16% 8% 3 6% 5% 4 4 4 6% 7% 39%	3960
August	1st to 10th	Night	20% 9% 3 7% 5% 4 4 4 6% 7% 30%	2915
	11th to 20th	Night	8% 7% 3 7% 5% 6% 6% 5% 8% 8% 39%	2932
	21st to end	Night	8% 4 2 5% 3 4 4 3 5% 9% 53%	3586
September	1st to 10th	Night	14% 6% 3 5% 4 4 4 4 7% 7% 42%	2025
	11th to 20th	Night	14% 7% 2 4 3 3 4 3 4 6% 50%	2200
	21st to end	Night	21% 7% 2 5% 4 4 4 3 5% 6% 39%	2200
October	1st to 10th	Night	20% 7% 2 6% 4 3 4 3 4 6% 41%	2200
	11th to 20th	Night	15% 5% 2 6% 3 4 4 3 5% 7% 47%	2407
	21st to end	Night	19% 7% 2 6% 4 3 4 3 5% 7% 40%	2860
November	1st to 10th	Night	16% 6% 2 6% 4 3 4 3 5% 6% 46%	2667
	11th to 20th	Night	16% 8% 2 6% 4 4 3 3 4 5% 45%	2730
	21st to end	Night	16% 6% 2 6% 4 3 3 4 6% 7% 43%	2730
December	1st to 10th	Night	18% 7% 2 5% 4 4 4 3 3 4 47%	4516
	11th to 20th	Night	22% 9% 3 5% 3 3 3 2 4 4 41%	5348
	21st to end	Night	19% 10% 3 6% 3 3 3 3 4 5% 41%	7150

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	39% 3 10% 24% 21% 2	4662
	11th to 20th	Day	42% 4 9% 20% 17% 8%	4680
	21st to end	Day	42% 3 10% 24% 20% 2	5142
February	1st to 10th	Day	47% 6% 13% 18% 15% 2	2032
	11th to 20th	Day	43% 4 12% 23% 15% 3	2057
	21st to end	Day	47% 4 11% 20% 15% 3	1730
March	1st to 10th	Day	49% 3 11% 13% 13% 11%	4579
	11th to 20th	Day	40% 5% 17% 26% 11% 2	4885
	21st to end	Day	54% 4 7% 14% 16% 5%	5712
April	1st to 10th	Day	45% 5% 11% 19% 17% 3	2400
	11th to 20th	Day	43% 6% 11% 20% 18% 3	2384
	21st to end	Day	45% 5% 10% 20% 17% 4	2600
May	1st to 10th	Day	60% 7% 13% 12% 6% 1	5897
	11th to 20th	Day	53% 5% 14% 16% 11% 1	5865
	21st to end	Day	50% 7% 10% 20% 13% 1	6872
June	1st to 10th	Day	47% 7% 12% 21% 13% 1	2800
	11th to 20th	Day	43% 6% 14% 23% 13% 1	2800
	21st to end	Day	41% 8% 14% 23% 13% 1	2800
July	1st to 10th	Day	52% 6% 11% 18% 11% 2	6290
	11th to 20th	Day	48% 5% 16% 21% 9% 1	6285
	21st to end	Day	41% 5% 12% 27% 14% 1	6649
August	1st to 10th	Day	49% 5% 17% 20% 8%	4222
	11th to 20th	Day	41% 5% 17% 28% 8% 1	4150
	21st to end	Day	30% 6% 15% 29% 19% 1	4312
September	1st to 10th	Day	38% 6% 10% 25% 20% 1	2375
	11th to 20th	Day	33% 6% 12% 24% 23% 3	2200
	21st to end	Day	46% 5% 8% 20% 19% 2	2200
October	1st to 10th	Day	38% 4 11% 26% 17% 4	3590
	11th to 20th	Day	32% 4 9% 27% 25% 4	3216
	21st to end	Day	31% 4 15% 30% 19% 2	3180
November	1st to 10th	Day	42% 4 13% 20% 19% 2	1851
	11th to 20th	Day	39% 5% 12% 21% 19% 3	1890
	21st to end	Day	44% 5% 11% 26% 13% 2	1890
December	1st to 10th	Day	41% 4 13% 27% 14% 1	2866
	11th to 20th	Day	42% 3 13% 17% 19% 6%	3066
	21st to end	Day	51% 4 8% 20% 13% 4	4048
January	1st to 10th	Night	38% 3 9% 30% 18% 2	8234
	11th to 20th	Night	48% 3 9% 19% 15% 5%	8280
	21st to end	Night	49% 4 8% 19% 17% 4	9024
February	1st to 10th	Night	47% 6% 11% 21% 13% 1	2585
	11th to 20th	Night	46% 4 9% 21% 16% 3	2460
	21st to end	Night	47% 4 9% 23% 14% 3	2076
March	1st to 10th	Night	50% 3 9% 17% 14% 7%	5494
	11th to 20th	Night	48% 5% 14% 18% 11% 3	5229
	21st to end	Night	55% 3 6% 10% 21% 5%	5204
April	1st to 10th	Night	49% 3 8% 20% 16% 3	2000
	11th to 20th	Night	47% 4 10% 18% 18% 3	1963
	21st to end	Night	49% 5% 8% 18% 15% 4	1800
May	1st to 10th	Night	61% 6% 13% 11% 8% 1	4060
	11th to 20th	Night	57% 5% 13% 15% 8% 3	4034
	21st to end	Night	56% 7% 11% 16% 9%	4045
June	1st to 10th	Night	50% 6% 11% 19% 14% 1	1600
	11th to 20th	Night	46% 5% 11% 24% 14% 1	1600
	21st to end	Night	47% 6% 13% 20% 13% 1	1600
July	1st to 10th	Night	56% 4 9% 17% 13%	3560
	11th to 20th	Night	52% 5% 16% 19% 8%	3552
	21st to end	Night	45% 4 13% 24% 13% 1	3843
August	1st to 10th	Night	53% 7% 13% 17% 9% 1	2903
	11th to 20th	Night	41% 6% 16% 28% 8%	2959
	21st to end	Night	30% 5% 16% 28% 21% 1	3586
September	1st to 10th	Night	39% 7% 11% 24% 18% 1	2025
	11th to 20th	Night	37% 5% 10% 24% 22% 2	2200
	21st to end	Night	47% 6% 8% 20% 18% 3	2200
October	1st to 10th	Night	41% 4 10% 26% 16% 3	3590
	11th to 20th	Night	27% 4 9% 24% 32% 4	3917
	21st to end	Night	34% 4 12% 27% 22% 2	4610
November	1st to 10th	Night	41% 6% 11% 22% 18% 3	2667
	11th to 20th	Night	42% 5% 10% 21% 18% 4	2730
	21st to end	Night	41% 5% 13% 26% 13% 2	2730
December	1st to 10th	Night	43% 4 11% 25% 16% 1	4516
	11th to 20th	Night	48% 3 12% 16% 19% 2	5348
	21st to end	Night	48% 4 10% 20% 17% 2	7150

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% 20% 33% 20% 5%	220
	11th to 20th	Day	19% 23% 37% 17% 4	220
	21st to end	Day	19% 19% 40% 17% 4 1	247
February	1st to 10th	Day	22% 20% 34% 20% 4	504
	11th to 20th	Day	23% 21% 38% 16% 1	536
	21st to end	Day	22% 17% 37% 20% 4	446
March	1st to 10th	Day	24% 17% 34% 21% 5%	540
	11th to 20th	Day	18% 20% 35% 22% 4 1	528
	21st to end	Day	23% 16% 36% 18% 6% 1	550
April	1st to 10th	Day	26% 15% 31% 22% 6%	500
	11th to 20th	Day	24% 12% 37% 23% 3	492
	21st to end	Day	23% 9% 34% 24% 9% 1	500
May	1st to 10th	Day	29% 12% 30% 23% 5%	503
	11th to 20th	Day	21% 8% 36% 25% 9% 1	527
	21st to end	Day	21% 5% 27% 31% 13% 2	573
June	1st to 10th	Day	20% 5% 27% 31% 15% 1	530
	11th to 20th	Day	19% 5% 28% 36% 11% 1	530
	21st to end	Day	18% 4 27% 34% 15% 2	530
July	1st to 10th	Day	19% 4 20% 36% 20% 2	525
	11th to 20th	Day	13% 3 20% 37% 24% 3	524
	21st to end	Day	14% 6% 23% 42% 13% 2	576
August	1st to 10th	Day	13% 4 22% 40% 19% 2	526
	11th to 20th	Day	16% 6% 17% 37% 20% 4	519
	21st to end	Day	12% 4 23% 36% 20% 5%	583
September	1st to 10th	Day	18% 4 22% 32% 18% 6%	530
	11th to 20th	Day	17% 5% 21% 32% 19% 7%	530
	21st to end	Day	23% 5% 27% 27% 15% 4	530
October	1st to 10th	Day	22% 10% 22% 25% 16% 5%	530
	11th to 20th	Day	19% 10% 28% 27% 14% 2	467
	21st to end	Day	22% 15% 27% 25% 10% 2	462
November	1st to 10th	Day	16% 15% 32% 24% 12% 2	425
	11th to 20th	Day	20% 17% 36% 21% 6%	430
	21st to end	Day	21% 19% 30% 20% 8% 1	430
December	1st to 10th	Day	21% 14% 35% 23% 6%	341
	11th to 20th	Day	25% 22% 34% 15% 4	220
	21st to end	Day	25% 17% 34% 15% 7% 2	242
January	1st to 10th	Night	20% 20% 38% 19% 3	840
	11th to 20th	Night	28% 21% 33% 16% 3	840
	21st to end	Night	21% 22% 36% 18% 3	924
February	1st to 10th	Night	21% 19% 36% 22% 3	840
	11th to 20th	Night	24% 20% 38% 16% 2	823
	21st to end	Night	23% 17% 36% 20% 3	692
March	1st to 10th	Night	22% 18% 33% 23% 4	840
	11th to 20th	Night	20% 14% 37% 23% 4 1	829
	21st to end	Night	24% 11% 35% 22% 6% 1	880
April	1st to 10th	Night	24% 11% 35% 26% 4	800
	11th to 20th	Night	23% 9% 37% 25% 6%	779
	21st to end	Night	23% 8% 33% 29% 7% 1	600
May	1st to 10th	Night	28% 6% 29% 27% 9% 1	600
	11th to 20th	Night	24% 9% 33% 27% 7% 1	592
	21st to end	Night	26% 3 18% 37% 15% 1	486
June	1st to 10th	Night	24% 5% 21% 35% 15% 1	400
	11th to 20th	Night	22% 4 20% 41% 13% 1	400
	21st to end	Night	25% 2 16% 42% 16%	400
July	1st to 10th	Night	21% 3 18% 38% 19% 1	390
	11th to 20th	Night	16% 2 16% 40% 23% 2	388
	21st to end	Night	17% 3 17% 42% 20% 1	447
August	1st to 10th	Night	14% 2 20% 43% 21% 1	598
	11th to 20th	Night	13% 3 17% 44% 22% 2	626
	21st to end	Night	16% 2 16% 38% 23% 5%	880
September	1st to 10th	Night	15% 3 23% 35% 21% 2	800
	11th to 20th	Night	18% 4 22% 29% 24% 4	800
	21st to end	Night	25% 5% 21% 31% 16% 2	800
October	1st to 10th	Night	24% 9% 24% 24% 16% 4	800
	11th to 20th	Night	19% 11% 29% 26% 12% 2	800
	21st to end	Night	23% 13% 31% 22% 9% 1	880
November	1st to 10th	Night	19% 11% 32% 26% 10% 2	820
	11th to 20th	Night	19% 21% 32% 20% 7%	840
	21st to end	Night	19% 22% 31% 21% 7% 1	840
December	1st to 10th	Night	25% 20% 31% 18% 5%	840
	11th to 20th	Night	24% 23% 32% 17% 3	840
	21st to end	Night	25% 20% 34% 17% 4	924

Page generated at 2026-03-15 02:23:56. Version ac07

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