Hiddenwell Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hiddenwell Observatory clear sky chart from 2005-11-06 to 2024-02-15.

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	15% 12% 5% 9% 7% 3 4 4 5% 6% 29%	78196
	Night	16% 14% 6% 11% 7% 4 4 4 4 5% 25%	80876
Transparency	Day	55% 6% 11% 18% 9% 1	77904
	Night	61% 6% 10% 14% 8% 1	80703
Seeing	Day	20% 11% 29% 24% 12% 4	14100
	Night	21% 11% 28% 27% 11% 1	23549

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	15% 22% 12% 17% 10% 4 4 3 3 3 7%	2286
	11th to 20th	Day	10% 21% 11% 22% 18% 5% 3 2 2 2 5%	2624
	21st to end	Day	17% 22% 12% 16% 10% 4 4 4 3 3 7%	3124
February	1st to 10th	Day	13% 18% 8% 16% 12% 4 4 3 4 3 13%	1710
	11th to 20th	Day	13% 13% 10% 18% 12% 4 6% 5% 4 3 13%	1609
	21st to end	Day	16% 17% 7% 12% 9% 4 5% 3 3 5% 19%	1462
March	1st to 10th	Day	14% 13% 6% 12% 9% 3 4 4 4 6% 26%	1909
	11th to 20th	Day	13% 13% 7% 9% 7% 3 4 5% 5% 5% 29%	1980
	21st to end	Day	18% 11% 5% 6% 7% 3 4 4 4 6% 33%	2178
April	1st to 10th	Day	17% 14% 6% 8% 5% 3 4 4 5% 5% 28%	2065
	11th to 20th	Day	17% 12% 3 6% 5% 3 3 5% 4 6% 36%	2312
	21st to end	Day	20% 9% 4 6% 6% 3 5% 3 5% 7% 33%	2340
May	1st to 10th	Day	18% 8% 4 6% 6% 3 4 4 5% 7% 37%	2340
	11th to 20th	Day	17% 8% 3 6% 5% 3 3 4 4 6% 41%	2358
	21st to end	Day	13% 5% 2 5% 5% 3 5% 4 6% 8% 44%	2725
June	1st to 10th	Day	13% 7% 3 5% 5% 3 4 5% 6% 8% 40%	2632
	11th to 20th	Day	11% 5% 2 5% 6% 3 5% 5% 6% 8% 44%	2700
	21st to end	Day	15% 5% 3 5% 4 3 5% 4 5% 8% 43%	2700
July	1st to 10th	Day	9% 4 2 4 4 2 6% 5% 7% 9% 49%	2700
	11th to 20th	Day	12% 5% 2 4 5% 3 5% 5% 6% 9% 43%	2589
	21st to end	Day	12% 5% 2 5% 5% 3 5% 5% 7% 8% 44%	2547
August	1st to 10th	Day	11% 5% 2 5% 5% 3 5% 6% 6% 10% 42%	2327
	11th to 20th	Day	12% 6% 2 5% 6% 4 6% 5% 6% 8% 41%	2303
	21st to end	Day	13% 7% 2 5% 5% 3 4 5% 6% 8% 41%	2564
September	1st to 10th	Day	13% 7% 2 7% 6% 3 6% 4 6% 8% 39%	2118
	11th to 20th	Day	14% 5% 3 5% 5% 3 4 4 6% 7% 43%	1980
	21st to end	Day	17% 8% 3 6% 6% 3 5% 6% 5% 8% 34%	1980
October	1st to 10th	Day	20% 8% 4 7% 6% 3 4 5% 5% 7% 32%	1836
	11th to 20th	Day	26% 13% 4 8% 7% 3 5% 4 5% 6% 19%	1800
	21st to end	Day	28% 17% 5% 8% 6% 3 4 3 4 4 16%	1908
November	1st to 10th	Day	16% 19% 5% 8% 8% 4 4 4 4 5% 23%	1664
	11th to 20th	Day	16% 18% 6% 12% 7% 3 6% 5% 5% 5% 16%	1520
	21st to end	Day	19% 21% 9% 12% 7% 4 5% 3 4 5% 11%	1520
December	1st to 10th	Day	15% 27% 14% 16% 8% 3 4 3 3 3 5%	1520
	11th to 20th	Day	18% 21% 9% 17% 8% 4 4 3 4 5% 8%	1835
	21st to end	Day	25% 25% 9% 12% 6% 3 3 3 3 4 7%	2431
January	1st to 10th	Night	15% 22% 12% 19% 10% 3 4 3 2 3 6%	4652
	11th to 20th	Night	13% 17% 9% 19% 16% 6% 5% 4 3 3 5%	4340
	21st to end	Night	17% 19% 10% 17% 11% 4 5% 4 3 3 7%	4532
February	1st to 10th	Night	13% 19% 9% 15% 13% 5% 4 4 4 3 12%	2470
	11th to 20th	Night	13% 15% 9% 15% 10% 4 4 4 4 5% 15%	2332
	21st to end	Night	15% 13% 8% 13% 8% 3 5% 4 4 5% 20%	1792
March	1st to 10th	Night	12% 13% 6% 14% 8% 3 4 3 4 5% 27%	2038
	11th to 20th	Night	12% 13% 5% 12% 6% 4 4 4 4 5% 29%	1979
	21st to end	Night	18% 12% 5% 7% 6% 3 5% 3 4 5% 33%	2178
April	1st to 10th	Night	18% 13% 5% 6% 5% 3 4 5% 4 6% 30%	1908
	11th to 20th	Night	18% 9% 4 5% 4 3 5% 4 4 7% 38%	1599
	21st to end	Night	18% 10% 3 7% 6% 3 5% 4 5% 6% 31%	1620
May	1st to 10th	Night	16% 8% 3 7% 5% 3 4 5% 5% 7% 37%	1620
	11th to 20th	Night	16% 6% 3 5% 5% 3 5% 4 5% 7% 41%	1533
	21st to end	Night	9% 5% 2 5% 5% 4 4 5% 6% 8% 46%	1550
June	1st to 10th	Night	13% 7% 3 6% 5% 3 4 4 5% 9% 41%	1324
	11th to 20th	Night	13% 5% 2 6% 5% 2 5% 4 6% 9% 42%	1260
	21st to end	Night	14% 6% 2 5% 5% 3 6% 4 6% 7% 42%	1260
July	1st to 10th	Night	8% 3 2 3 4 3 4 4 4 9% 55%	1260
	11th to 20th	Night	9% 4 2 5% 5% 3 5% 5% 6% 11% 45%	1367
	21st to end	Night	9% 5% 2 5% 4 2 4 6% 6% 8% 48%	1771
August	1st to 10th	Night	10% 4 2 6% 5% 3 4 5% 5% 8% 47%	1611
	11th to 20th	Night	9% 4 2 5% 5% 3 5% 6% 4 9% 48%	1598
	21st to end	Night	12% 6% 3 6% 6% 3 4 4 4 7% 45%	1782
September	1st to 10th	Night	11% 5% 3 5% 5% 3 5% 4 7% 7% 46%	1830
	11th to 20th	Night	12% 5% 2 5% 5% 4 3 4 6% 7% 48%	1980
	21st to end	Night	16% 7% 3 7% 6% 3 5% 5% 5% 6% 38%	1980
October	1st to 10th	Night	19% 8% 3 7% 6% 3 4 4 5% 6% 36%	2124
	11th to 20th	Night	24% 12% 4 9% 6% 4 4 4 5% 7% 22%	2160
	21st to end	Night	25% 15% 4 10% 6% 3 4 4 4 5% 19%	2443
November	1st to 10th	Night	17% 15% 4 8% 6% 4 4 4 5% 6% 26%	2411
	11th to 20th	Night	18% 19% 6% 10% 7% 4 5% 5% 5% 4 17%	2660
	21st to end	Night	20% 21% 9% 11% 7% 3 4 3 3 5% 13%	2660
December	1st to 10th	Night	19% 26% 11% 13% 7% 4 4 3 4 3 7%	2660
	11th to 20th	Night	13% 21% 10% 16% 9% 4 5% 4 4 4 10%	3356
	21st to end	Night	24% 23% 10% 14% 7% 3 3 3 3 3 6%	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	83% 4 7% 4 1	2287
	11th to 20th	Day	90% 3 3 2 2	2624
	21st to end	Day	83% 6% 6% 3 2	3124
February	1st to 10th	Day	77% 5% 7% 10% 1	1710
	11th to 20th	Day	76% 5% 7% 8% 4	1618
	21st to end	Day	69% 5% 8% 12% 5%	1462
March	1st to 10th	Day	60% 5% 11% 14% 8% 1	1912
	11th to 20th	Day	57% 6% 8% 17% 9% 2	1980
	21st to end	Day	53% 5% 12% 19% 11% 2	2178
April	1st to 10th	Day	57% 6% 11% 17% 9%	2065
	11th to 20th	Day	49% 5% 9% 22% 14% 1	2312
	21st to end	Day	50% 6% 11% 19% 11% 2	2340
May	1st to 10th	Day	47% 6% 8% 24% 14% 1	2340
	11th to 20th	Day	44% 5% 9% 25% 14% 2	2362
	21st to end	Day	38% 5% 14% 24% 15% 3	2725
June	1st to 10th	Day	40% 8% 12% 24% 16% 1	2632
	11th to 20th	Day	37% 7% 12% 26% 17% 1	2700
	21st to end	Day	40% 6% 12% 27% 14% 1	2700
July	1st to 10th	Day	30% 7% 15% 25% 20% 3	2626
	11th to 20th	Day	35% 7% 14% 30% 12% 2	2509
	21st to end	Day	37% 7% 13% 26% 15% 2	2405
August	1st to 10th	Day	36% 8% 15% 28% 11% 2	2314
	11th to 20th	Day	40% 7% 15% 25% 12% 1	2303
	21st to end	Day	39% 7% 15% 26% 13% 1	2564
September	1st to 10th	Day	42% 7% 13% 24% 11% 2	2118
	11th to 20th	Day	38% 7% 14% 28% 12%	1980
	21st to end	Day	47% 7% 14% 24% 7% 1	1980
October	1st to 10th	Day	52% 6% 11% 19% 10% 2	1836
	11th to 20th	Day	66% 6% 10% 13% 5% 1	1800
	21st to end	Day	72% 5% 8% 11% 4	1908
November	1st to 10th	Day	63% 5% 9% 15% 7%	1664
	11th to 20th	Day	67% 8% 11% 8% 5% 1	1520
	21st to end	Day	77% 6% 8% 8% 1	1520
December	1st to 10th	Day	86% 4 5% 3 1	1520
	11th to 20th	Day	81% 6% 7% 5% 1	1835
	21st to end	Day	83% 5% 8% 3	2431
January	1st to 10th	Night	84% 5% 6% 4 1	4652
	11th to 20th	Night	85% 6% 5% 3 2	4340
	21st to end	Night	82% 6% 7% 3 2	4532
February	1st to 10th	Night	78% 5% 7% 9% 2	2470
	11th to 20th	Night	72% 5% 10% 10% 3	2334
	21st to end	Night	66% 5% 10% 12% 7%	1792
March	1st to 10th	Night	60% 6% 11% 16% 8% 1	2048
	11th to 20th	Night	58% 5% 8% 17% 10% 2	1980
	21st to end	Night	55% 4 9% 19% 12% 2	2178
April	1st to 10th	Night	55% 6% 10% 18% 11% 1	1908
	11th to 20th	Night	47% 5% 9% 20% 17% 2	1599
	21st to end	Night	53% 5% 10% 16% 14% 2	1620
May	1st to 10th	Night	46% 6% 9% 21% 15% 2	1620
	11th to 20th	Night	43% 5% 8% 22% 18% 4	1534
	21st to end	Night	35% 6% 14% 25% 16% 4	1551
June	1st to 10th	Night	40% 6% 10% 23% 17% 2	1324
	11th to 20th	Night	37% 6% 13% 25% 17% 2	1260
	21st to end	Night	40% 6% 10% 24% 17% 2	1260
July	1st to 10th	Night	27% 6% 11% 27% 25% 3	1225
	11th to 20th	Night	32% 8% 13% 28% 18% 1	1324
	21st to end	Night	33% 7% 16% 26% 16% 2	1672
August	1st to 10th	Night	34% 8% 13% 30% 14% 1	1600
	11th to 20th	Night	32% 8% 15% 28% 15% 2	1598
	21st to end	Night	40% 6% 12% 27% 13% 1	1782
September	1st to 10th	Night	35% 7% 13% 28% 14% 3	1830
	11th to 20th	Night	35% 6% 14% 29% 15% 1	1980
	21st to end	Night	46% 7% 12% 24% 9% 1	1980
October	1st to 10th	Night	49% 7% 10% 20% 14% 1	2124
	11th to 20th	Night	62% 6% 12% 15% 5%	2160
	21st to end	Night	69% 6% 9% 10% 6%	2443
November	1st to 10th	Night	58% 7% 10% 18% 7%	2411
	11th to 20th	Night	68% 7% 9% 11% 4 1	2660
	21st to end	Night	76% 5% 11% 8% 1	2660
December	1st to 10th	Night	83% 5% 6% 4 1	2660
	11th to 20th	Night	78% 6% 10% 5% 1	3356
	21st to end	Night	84% 5% 7% 3	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	19% 20% 37% 17% 7% 1	204
	11th to 20th	Day	21% 19% 38% 14% 7% 1	270
	21st to end	Day	25% 15% 30% 25% 5%	297
February	1st to 10th	Day	21% 25% 35% 15% 4	270
	11th to 20th	Day	23% 20% 41% 14% 2	252
	21st to end	Day	25% 31% 31% 11% 2	198
March	1st to 10th	Day	22% 18% 38% 16% 6% 1	352
	11th to 20th	Day	23% 15% 32% 22% 7% 1	420
	21st to end	Day	28% 11% 32% 22% 6% 1	462
April	1st to 10th	Day	23% 15% 33% 21% 8%	420
	11th to 20th	Day	26% 15% 28% 16% 9% 5%	412
	21st to end	Day	27% 9% 28% 24% 9% 2	420
May	1st to 10th	Day	24% 8% 30% 22% 12% 3	423
	11th to 20th	Day	21% 8% 28% 23% 15% 5%	447
	21st to end	Day	17% 7% 27% 27% 15% 7%	485
June	1st to 10th	Day	14% 8% 31% 29% 15% 2	562
	11th to 20th	Day	14% 10% 28% 30% 15% 4	630
	21st to end	Day	16% 5% 35% 29% 12% 3	630
July	1st to 10th	Day	10% 4 27% 31% 22% 6%	621
	11th to 20th	Day	14% 6% 31% 29% 15% 7%	600
	21st to end	Day	12% 4 27% 32% 18% 7%	488
August	1st to 10th	Day	13% 3 24% 31% 18% 11%	446
	11th to 20th	Day	13% 3 19% 30% 22% 13%	439
	21st to end	Day	16% 5% 22% 31% 19% 7%	495
September	1st to 10th	Day	12% 8% 24% 31% 17% 8%	450
	11th to 20th	Day	12% 6% 21% 28% 22% 11%	450
	21st to end	Day	17% 9% 25% 26% 16% 7%	450
October	1st to 10th	Day	24% 9% 26% 22% 14% 6%	450
	11th to 20th	Day	27% 18% 30% 19% 5% 2	450
	21st to end	Day	35% 15% 30% 15% 5%	423
November	1st to 10th	Day	23% 19% 33% 17% 8% 1	266
	11th to 20th	Day	24% 23% 28% 18% 4 3	180
	21st to end	Day	25% 23% 35% 16% 1	180
December	1st to 10th	Day	29% 18% 36% 14% 2 1	180
	11th to 20th	Day	29% 23% 30% 13% 4 1	180
	21st to end	Day	35% 20% 32% 10% 3	198
January	1st to 10th	Night	24% 18% 32% 18% 6% 1	950
	11th to 20th	Night	25% 17% 32% 20% 5% 1	889
	21st to end	Night	20% 11% 36% 25% 7% 1	836
February	1st to 10th	Night	22% 17% 35% 22% 4	760
	11th to 20th	Night	22% 14% 35% 23% 5% 1	722
	21st to end	Night	23% 19% 33% 22% 4	592
March	1st to 10th	Night	18% 16% 35% 24% 6% 1	720
	11th to 20th	Night	17% 16% 36% 25% 5% 2	720
	21st to end	Night	23% 11% 29% 27% 10% 1	792
April	1st to 10th	Night	24% 11% 33% 25% 7%	720
	11th to 20th	Night	21% 14% 25% 28% 11% 1	535
	21st to end	Night	26% 9% 24% 29% 11% 1	540
May	1st to 10th	Night	20% 5% 29% 33% 12% 1	540
	11th to 20th	Night	20% 5% 24% 37% 13% 1	472
	21st to end	Night	13% 2 27% 39% 18% 1	389
June	1st to 10th	Night	16% 6% 24% 39% 13% 1	360
	11th to 20th	Night	15% 6% 28% 39% 13%	360
	21st to end	Night	16% 3 24% 41% 15% 1	360
July	1st to 10th	Night	9% 3 18% 49% 20% 1	350
	11th to 20th	Night	8% 5% 22% 38% 25% 2	437
	21st to end	Night	12% 2 19% 44% 22% 1	591
August	1st to 10th	Night	11% 4 16% 39% 29% 1	537
	11th to 20th	Night	10% 2 16% 40% 28% 5%	534
	21st to end	Night	13% 3 21% 33% 28% 2	594
September	1st to 10th	Night	12% 4 22% 37% 19% 6%	710
	11th to 20th	Night	14% 4 20% 37% 21% 4	720
	21st to end	Night	17% 8% 22% 31% 18% 4	720
October	1st to 10th	Night	23% 7% 26% 28% 15% 1	720
	11th to 20th	Night	29% 12% 24% 27% 7% 1	720
	21st to end	Night	34% 12% 28% 22% 4 1	792
November	1st to 10th	Night	28% 13% 27% 24% 7% 1	740
	11th to 20th	Night	25% 21% 29% 18% 7%	760
	21st to end	Night	30% 16% 30% 21% 4	760
December	1st to 10th	Night	32% 16% 31% 17% 4	760
	11th to 20th	Night	23% 18% 38% 16% 3 1	802
	21st to end	Night	32% 14% 32% 18% 3	1045

Page generated at 2024-02-12 06:35:31. Version ac07

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