Cypress Cottage
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cypress Cottage clear sky chart from 2005-11-06 to 2024-01-13.

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	13% 7% 3 6% 5% 3 5% 5% 5% 8% 41%	74856
	Night	14% 7% 3 5% 5% 3 4 4 5% 7% 43%	74898
Transparency	Day	43% 4 11% 25% 16% 3	74564
	Night	42% 3 10% 24% 18% 3	74711
Seeing	Day	16% 8% 22% 24% 20% 10%	14261
	Night	18% 7% 24% 31% 19% 2	24162

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	18% 8% 4 8% 5% 3 4 5% 4 5% 36%	1517
	11th to 20th	Day	21% 10% 4 8% 6% 4 4 4 4 5% 29%	1456
	21st to end	Day	15% 10% 5% 7% 5% 3 4 4 4 5% 37%	1816
February	1st to 10th	Day	19% 10% 5% 6% 5% 2 4 4 5% 6% 34%	1800
	11th to 20th	Day	19% 9% 4 7% 5% 3 5% 4 5% 6% 33%	1748
	21st to end	Day	18% 10% 4 9% 5% 3 5% 5% 4 5% 33%	1480
March	1st to 10th	Day	16% 9% 3 5% 5% 3 4 4 5% 5% 40%	1800
	11th to 20th	Day	22% 9% 3 6% 6% 4 4 4 4 6% 34%	1867
	21st to end	Day	19% 9% 3 7% 7% 3 5% 4 5% 6% 31%	2339
April	1st to 10th	Day	13% 6% 3 5% 6% 3 5% 4 6% 8% 43%	2160
	11th to 20th	Day	15% 8% 3 6% 6% 3 5% 4 5% 7% 40%	2134
	21st to end	Day	18% 7% 2 5% 4 2 5% 4 5% 7% 41%	2205
May	1st to 10th	Day	16% 6% 3 6% 5% 3 4 4 7% 8% 37%	2340
	11th to 20th	Day	17% 7% 3 6% 5% 3 4 5% 4 8% 38%	2301
	21st to end	Day	9% 4 3 6% 7% 4 7% 6% 8% 8% 38%	2533
June	1st to 10th	Day	10% 5% 2 5% 5% 3 4 4 6% 9% 47%	2520
	11th to 20th	Day	5% 3 2 5% 5% 3 6% 6% 7% 11% 47%	2520
	21st to end	Day	6% 4 2 4 6% 4 6% 6% 6% 12% 45%	2520
July	1st to 10th	Day	9% 6% 3 6% 5% 4 6% 6% 7% 11% 37%	2520
	11th to 20th	Day	6% 4 2 4 5% 4 6% 6% 7% 11% 45%	2520
	21st to end	Day	7% 5% 2 5% 5% 4 6% 7% 7% 11% 40%	2640
August	1st to 10th	Day	6% 5% 2 6% 6% 4 6% 7% 8% 10% 41%	2245
	11th to 20th	Day	9% 7% 3 6% 5% 4 6% 4 7% 10% 41%	2125
	21st to end	Day	8% 5% 2 4 4 3 4 4 6% 9% 49%	2376
September	1st to 10th	Day	11% 5% 2 6% 4 4 5% 4 5% 7% 46%	2160
	11th to 20th	Day	10% 5% 2 4 4 3 5% 5% 5% 9% 47%	1985
	21st to end	Day	11% 4 3 4 5% 3 5% 4 4 6% 52%	1980
October	1st to 10th	Day	10% 4 2 4 4 3 4 3 4 7% 55%	1980
	11th to 20th	Day	13% 5% 3 4 5% 2 4 4 4 6% 50%	1881
	21st to end	Day	19% 7% 3 5% 5% 2 3 3 4 5% 45%	1795
November	1st to 10th	Day	9% 5% 3 5% 4 2 3 4 4 6% 55%	1672
	11th to 20th	Day	17% 6% 3 4 5% 2 4 4 4 6% 45%	1710
	21st to end	Day	18% 8% 2 5% 3 3 4 4 4 6% 43%	1710
December	1st to 10th	Day	20% 11% 3 6% 4 2 4 4 4 6% 36%	1710
	11th to 20th	Day	16% 10% 5% 8% 6% 3 5% 5% 4 6% 33%	2008
	21st to end	Day	20% 13% 5% 7% 6% 3 5% 4 5% 6% 26%	2783
January	1st to 10th	Night	17% 10% 4 7% 5% 3 4 3 3 5% 38%	2648
	11th to 20th	Night	21% 10% 5% 8% 6% 3 4 4 4 5% 31%	2561
	21st to end	Night	18% 10% 4 7% 5% 3 3 4 5% 7% 36%	2534
February	1st to 10th	Night	22% 11% 5% 6% 5% 2 4 4 5% 5% 31%	2160
	11th to 20th	Night	19% 8% 4 7% 5% 2 5% 4 4 5% 38%	2098
	21st to end	Night	21% 10% 3 6% 5% 3 4 4 4 5% 35%	1776
March	1st to 10th	Night	17% 8% 3 6% 5% 3 3 3 4 5% 43%	2160
	11th to 20th	Night	18% 10% 4 6% 6% 3 4 4 4 6% 36%	2093
	21st to end	Night	19% 9% 4 7% 5% 3 4 4 4 7% 35%	2032
April	1st to 10th	Night	12% 6% 3 5% 4 3 4 4 5% 7% 47%	1800
	11th to 20th	Night	16% 6% 2 5% 4 3 4 4 5% 6% 45%	1775
	21st to end	Night	17% 6% 3 6% 5% 3 3 5% 6% 7% 39%	1752
May	1st to 10th	Night	16% 6% 2 5% 5% 2 4 4 5% 7% 41%	1620
	11th to 20th	Night	12% 6% 3 5% 6% 3 4 4 6% 8% 41%	1592
	21st to end	Night	6% 3 2 6% 6% 4 5% 6% 7% 13% 42%	1738
June	1st to 10th	Night	10% 4 2 5% 4 2 5% 4 6% 9% 49%	1440
	11th to 20th	Night	6% 3 1 4 4 3 4 5% 7% 10% 54%	1440
	21st to end	Night	4 2 2 4 5% 3 6% 6% 8% 11% 51%	1440
July	1st to 10th	Night	6% 5% 2 6% 4 3 5% 6% 6% 10% 47%	1440
	11th to 20th	Night	7% 5% 2 5% 4 2 3 4 6% 10% 53%	1440
	21st to end	Night	9% 2 2 4 6% 3 6% 6% 6% 9% 49%	1676
August	1st to 10th	Night	6% 4 2 4 5% 3 4 5% 6% 9% 51%	1690
	11th to 20th	Night	5% 4 2 4 6% 4 4 6% 8% 10% 47%	1776
	21st to end	Night	5% 4 2 4 5% 3 3 4 6% 9% 54%	1980
September	1st to 10th	Night	10% 4 3 4 4 3 4 5% 4 7% 52%	1800
	11th to 20th	Night	9% 4 3 5% 4 3 4 4 5% 8% 51%	1957
	21st to end	Night	12% 4 1 4 3 2 3 3 4 7% 56%	1980
October	1st to 10th	Night	8% 4 2 4 3 3 4 4 4 6% 57%	1980
	11th to 20th	Night	15% 5% 2 5% 4 3 3 4 4 5% 51%	2076
	21st to end	Night	18% 7% 2 5% 4 3 3 3 4 5% 45%	2560
November	1st to 10th	Night	12% 5% 2 4 4 2 3 4 4 6% 55%	2406
	11th to 20th	Night	15% 6% 3 5% 4 2 4 3 4 6% 49%	2470
	21st to end	Night	18% 7% 3 5% 4 2 4 3 4 6% 45%	2470
December	1st to 10th	Night	20% 9% 4 6% 5% 3 4 4 4 6% 36%	2470
	11th to 20th	Night	17% 10% 4 7% 4 3 4 4 5% 6% 36%	3184
	21st to end	Night	19% 14% 4 8% 7% 4 5% 4 4 5% 26%	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	52% 3 8% 24% 11% 2	1518
	11th to 20th	Day	59% 3 9% 20% 9%	1456
	21st to end	Day	50% 2 9% 27% 9% 2	1816
February	1st to 10th	Day	52% 3 8% 24% 11% 1	1800
	11th to 20th	Day	54% 3 7% 22% 11% 3	1758
	21st to end	Day	55% 3 9% 17% 12% 5%	1480
March	1st to 10th	Day	47% 3 7% 23% 18% 2	1800
	11th to 20th	Day	54% 2 10% 21% 10% 2	1867
	21st to end	Day	54% 3 10% 22% 9% 2	2339
April	1st to 10th	Day	40% 3 13% 24% 18% 1	2160
	11th to 20th	Day	45% 3 8% 23% 18% 3	2134
	21st to end	Day	45% 3 10% 28% 12% 2	2205
May	1st to 10th	Day	45% 5% 12% 26% 10% 1	2340
	11th to 20th	Day	47% 5% 12% 21% 14% 1	2305
	21st to end	Day	40% 6% 17% 23% 12% 2	2533
June	1st to 10th	Day	34% 4 12% 27% 21% 2	2520
	11th to 20th	Day	30% 6% 15% 27% 21% 3	2520
	21st to end	Day	32% 6% 15% 24% 17% 5%	2520
July	1st to 10th	Day	41% 5% 13% 24% 13% 4	2451
	11th to 20th	Day	34% 6% 15% 26% 16% 4	2445
	21st to end	Day	36% 6% 16% 28% 12% 2	2493
August	1st to 10th	Day	36% 5% 15% 28% 16%	2232
	11th to 20th	Day	38% 4 13% 28% 15% 2	2125
	21st to end	Day	32% 5% 13% 26% 19% 5%	2376
September	1st to 10th	Day	38% 4 10% 26% 18% 4	2160
	11th to 20th	Day	36% 4 9% 25% 22% 3	1985
	21st to end	Day	35% 3 6% 26% 26% 4	1980
October	1st to 10th	Day	30% 3 8% 26% 27% 5%	1980
	11th to 20th	Day	37% 2 7% 25% 23% 6%	1881
	21st to end	Day	43% 2 7% 26% 19% 4	1795
November	1st to 10th	Day	33% 3 9% 28% 22% 5%	1672
	11th to 20th	Day	41% 2 8% 25% 20% 5%	1710
	21st to end	Day	43% 2 8% 26% 18% 3	1710
December	1st to 10th	Day	51% 2 10% 23% 12% 1	1710
	11th to 20th	Day	55% 2 8% 22% 12% 1	2005
	21st to end	Day	60% 1 10% 19% 9%	2783
January	1st to 10th	Night	52% 2 8% 22% 15% 2	2648
	11th to 20th	Night	58% 2 8% 21% 11% 1	2561
	21st to end	Night	50% 2 10% 24% 13% 2	2534
February	1st to 10th	Night	56% 3 9% 21% 10% 1	2160
	11th to 20th	Night	51% 2 6% 24% 14% 2	2099
	21st to end	Night	53% 3 8% 19% 14% 3	1776
March	1st to 10th	Night	45% 3 7% 20% 20% 5%	2160
	11th to 20th	Night	51% 3 10% 21% 13% 2	2093
	21st to end	Night	51% 3 13% 21% 11% 2	2032
April	1st to 10th	Night	37% 3 10% 27% 20% 3	1800
	11th to 20th	Night	41% 2 9% 20% 21% 6%	1775
	21st to end	Night	46% 2 9% 24% 17% 3	1752
May	1st to 10th	Night	44% 3 11% 26% 14% 2	1620
	11th to 20th	Night	42% 6% 13% 22% 17% 1	1593
	21st to end	Night	32% 7% 18% 25% 15% 3	1739
June	1st to 10th	Night	33% 4 12% 26% 23% 3	1440
	11th to 20th	Night	24% 5% 18% 24% 24% 5%	1440
	21st to end	Night	24% 6% 17% 28% 18% 7%	1440
July	1st to 10th	Night	32% 6% 14% 29% 16% 4	1400
	11th to 20th	Night	28% 5% 16% 28% 18% 5%	1392
	21st to end	Night	32% 5% 14% 30% 17% 2	1583
August	1st to 10th	Night	29% 6% 15% 28% 21% 2	1679
	11th to 20th	Night	30% 6% 14% 29% 18% 2	1776
	21st to end	Night	28% 4 14% 29% 20% 5%	1980
September	1st to 10th	Night	33% 4 9% 27% 23% 5%	1800
	11th to 20th	Night	33% 3 7% 25% 26% 5%	1957
	21st to end	Night	30% 3 8% 26% 27% 7%	1980
October	1st to 10th	Night	29% 3 9% 23% 31% 6%	1980
	11th to 20th	Night	37% 2 7% 23% 25% 7%	2076
	21st to end	Night	44% 2 5% 24% 19% 6%	2560
November	1st to 10th	Night	34% 3 7% 26% 26% 6%	2406
	11th to 20th	Night	38% 2 6% 24% 22% 8%	2470
	21st to end	Night	43% 2 7% 26% 19% 3	2470
December	1st to 10th	Night	52% 2 10% 22% 12% 2	2470
	11th to 20th	Night	51% 2 7% 22% 16% 2	3186
	21st to end	Night	62% 2 8% 17% 9% 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	23% 17% 31% 21% 6% 1	270
	11th to 20th	Day	27% 16% 36% 15% 5% 1	246
	21st to end	Day	20% 17% 45% 13% 6%	264
February	1st to 10th	Day	27% 17% 35% 17% 3 1	240
	11th to 20th	Day	29% 20% 36% 14% 1	240
	21st to end	Day	32% 15% 31% 16% 5% 1	198
March	1st to 10th	Day	22% 20% 38% 15% 5%	240
	11th to 20th	Day	27% 11% 36% 17% 7% 1	307
	21st to end	Day	28% 16% 30% 17% 8% 1	462
April	1st to 10th	Day	18% 15% 28% 27% 10% 1	420
	11th to 20th	Day	22% 11% 28% 24% 14% 2	412
	21st to end	Day	22% 12% 31% 22% 8% 5%	420
May	1st to 10th	Day	20% 11% 27% 28% 10% 4	423
	11th to 20th	Day	18% 7% 21% 29% 18% 8%	447
	21st to end	Day	11% 3 20% 27% 24% 15%	487
June	1st to 10th	Day	10% 3 18% 25% 30% 14%	630
	11th to 20th	Day	5% 4 16% 30% 31% 14%	630
	21st to end	Day	6% 3 18% 33% 25% 15%	630
July	1st to 10th	Day	10% 3 11% 23% 27% 26%	621
	11th to 20th	Day	9% 2 10% 27% 32% 20%	618
	21st to end	Day	9% 2 10% 25% 34% 19%	581
August	1st to 10th	Day	11% 3 9% 25% 33% 19%	446
	11th to 20th	Day	14% 2 11% 28% 31% 13%	439
	21st to end	Day	12% 2 8% 21% 35% 22%	495
September	1st to 10th	Day	11% 3 12% 21% 38% 16%	450
	11th to 20th	Day	11% 2 9% 25% 34% 20%	450
	21st to end	Day	15% 7% 17% 20% 29% 12%	450
October	1st to 10th	Day	11% 4 18% 31% 27% 9%	450
	11th to 20th	Day	15% 10% 28% 30% 12% 5%	351
	21st to end	Day	27% 11% 26% 24% 10% 1	297
November	1st to 10th	Day	11% 7% 36% 27% 14% 5%	270
	11th to 20th	Day	17% 17% 27% 27% 9% 2	270
	21st to end	Day	23% 10% 30% 26% 10% 1	270
December	1st to 10th	Day	22% 16% 31% 20% 9% 2	270
	11th to 20th	Day	23% 15% 29% 24% 7% 1	270
	21st to end	Day	28% 19% 29% 21% 4	297
January	1st to 10th	Night	22% 13% 32% 27% 5%	950
	11th to 20th	Night	27% 13% 33% 22% 5%	915
	21st to end	Night	23% 11% 37% 27% 2	896
February	1st to 10th	Night	27% 11% 32% 27% 3	720
	11th to 20th	Night	24% 14% 36% 24% 2	703
	21st to end	Night	28% 13% 36% 21% 3	592
March	1st to 10th	Night	22% 11% 32% 31% 4	720
	11th to 20th	Night	24% 8% 31% 29% 7%	720
	21st to end	Night	24% 8% 27% 33% 9% 1	646
April	1st to 10th	Night	17% 9% 30% 34% 10%	540
	11th to 20th	Night	19% 7% 29% 31% 13% 1	533
	21st to end	Night	20% 6% 27% 34% 12% 1	540
May	1st to 10th	Night	18% 7% 25% 32% 16% 1	540
	11th to 20th	Night	15% 5% 21% 34% 23% 2	531
	21st to end	Night	7% 2 16% 38% 32% 4	584
June	1st to 10th	Night	13% 2 12% 38% 32% 3	540
	11th to 20th	Night	7% 1 13% 42% 34% 3	540
	21st to end	Night	4 1 13% 40% 37% 4	540
July	1st to 10th	Night	9% 1 9% 27% 44% 10%	525
	11th to 20th	Night	8% 2 7% 29% 48% 6%	522
	21st to end	Night	10% 1 7% 37% 38% 7%	591
August	1st to 10th	Night	8% 1 6% 31% 47% 6%	537
	11th to 20th	Night	7% 1 9% 35% 43% 6%	534
	21st to end	Night	8% 1 5% 30% 50% 7%	594
September	1st to 10th	Night	12% 1 9% 32% 40% 6%	540
	11th to 20th	Night	11% 2 8% 31% 40% 7%	697
	21st to end	Night	13% 3 18% 30% 31% 4	720
October	1st to 10th	Night	11% 3 17% 34% 30% 5%	720
	11th to 20th	Night	18% 6% 25% 33% 18% 2	720
	21st to end	Night	22% 7% 28% 29% 13% 1	792
November	1st to 10th	Night	14% 6% 26% 36% 16% 2	740
	11th to 20th	Night	17% 9% 32% 29% 13%	760
	21st to end	Night	21% 9% 26% 31% 12% 1	760
December	1st to 10th	Night	24% 9% 29% 32% 6%	760
	11th to 20th	Night	24% 8% 31% 29% 7%	855
	21st to end	Night	27% 12% 29% 28% 4	1045

Page generated at 2024-01-10 09:16:07. Version ac07

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