Hidden Lake Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hidden Lake Observatory clear sky chart from 2005-11-06 to 2024-12-24.

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% 8% 3 7% 5% 4 5% 4 6% 7% 35%	101708
	Night	17% 9% 3 7% 4 4 4 4 5% 6% 37%	98390
Transparency	Day	45% 6% 12% 21% 13% 2	105229
	Night	44% 6% 13% 22% 13% 2	102945
Seeing	Day	25% 19% 29% 18% 7% 2	15054
	Night	24% 18% 29% 22% 7% 1	24154

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	14% 9% 3 6% 4 5% 5% 4 6% 6% 38%	2517
	11th to 20th	Day	16% 11% 5% 10% 6% 4 5% 4 4 6% 30%	2520
	21st to end	Day	21% 14% 7% 8% 4 4 3 3 3 4 27%	2842
February	1st to 10th	Day	16% 10% 3 8% 6% 5% 5% 5% 5% 6% 30%	1736
	11th to 20th	Day	13% 9% 3 7% 7% 6% 5% 4 5% 6% 35%	1848
	21st to end	Day	17% 12% 3 8% 5% 4 4 3 5% 6% 32%	1570
March	1st to 10th	Day	22% 14% 4 8% 5% 3 3 2 3 5% 30%	3116
	11th to 20th	Day	11% 10% 5% 8% 5% 5% 5% 5% 6% 7% 33%	3256
	21st to end	Day	20% 8% 3 7% 5% 5% 4 3 5% 6% 35%	4166
April	1st to 10th	Day	17% 11% 4 6% 4 5% 4 4 4 6% 34%	2280
	11th to 20th	Day	17% 8% 2 7% 5% 4 4 4 4 6% 39%	2254
	21st to end	Day	19% 9% 3 7% 5% 5% 4 3 6% 6% 34%	2382
May	1st to 10th	Day	26% 9% 3 7% 4 4 4 3 4 7% 28%	4106
	11th to 20th	Day	21% 8% 3 8% 5% 4 4 3 5% 7% 32%	4356
	21st to end	Day	14% 5% 2 5% 5% 4 5% 5% 7% 8% 40%	4837
June	1st to 10th	Day	17% 8% 2 5% 5% 6% 6% 5% 6% 9% 32%	2660
	11th to 20th	Day	17% 7% 2 7% 5% 4 4 5% 6% 9% 35%	2660
	21st to end	Day	16% 8% 2 7% 5% 6% 5% 4 6% 9% 33%	2660
July	1st to 10th	Day	11% 7% 3 7% 6% 6% 5% 5% 7% 9% 35%	4440
	11th to 20th	Day	12% 5% 2 6% 5% 5% 5% 5% 7% 10% 37%	4440
	21st to end	Day	16% 9% 3 8% 6% 5% 5% 4 6% 7% 31%	4814
August	1st to 10th	Day	20% 7% 3 8% 5% 5% 5% 5% 6% 8% 29%	4329
	11th to 20th	Day	14% 6% 3 7% 4 5% 5% 5% 7% 9% 35%	3743
	21st to end	Day	12% 5% 2 7% 5% 4 5% 4 7% 8% 40%	4180
September	1st to 10th	Day	12% 6% 2 7% 6% 5% 5% 4 6% 7% 41%	2280
	11th to 20th	Day	14% 6% 2 5% 4 3 4 3 5% 6% 48%	2164
	21st to end	Day	17% 7% 3 5% 3 4 5% 3 6% 7% 39%	2090
October	1st to 10th	Day	22% 8% 3 6% 4 4 4 3 5% 4 37%	2032
	11th to 20th	Day	14% 8% 2 5% 4 4 4 3 6% 7% 42%	1891
	21st to end	Day	22% 9% 2 6% 5% 4 5% 4 5% 6% 33%	1881
November	1st to 10th	Day	12% 9% 3 6% 4 3 4 3 4 6% 46%	1761
	11th to 20th	Day	18% 8% 2 4 4 4 5% 4 5% 7% 40%	1800
	21st to end	Day	18% 10% 3 8% 4 3 4 4 5% 6% 36%	1715
December	1st to 10th	Day	19% 10% 3 8% 6% 5% 4 4 4 6% 31%	1600
	11th to 20th	Day	21% 9% 3 5% 4 4 3 4 5% 6% 36%	1986
	21st to end	Day	20% 12% 5% 9% 5% 4 4 4 4 7% 25%	2796
January	1st to 10th	Night	16% 8% 3 7% 4 4 4 4 6% 6% 39%	4429
	11th to 20th	Night	14% 10% 4 9% 5% 4 4 4 6% 6% 34%	4440
	21st to end	Night	21% 14% 4 7% 4 5% 4 3 4 6% 27%	4811
February	1st to 10th	Night	16% 10% 3 6% 4 5% 5% 5% 5% 7% 34%	2442
	11th to 20th	Night	13% 10% 3 7% 5% 5% 5% 4 7% 7% 34%	2218
	21st to end	Night	18% 9% 3 8% 5% 4 4 3 5% 6% 35%	1884
March	1st to 10th	Night	23% 12% 3 7% 5% 4 4 3 4 5% 31%	3724
	11th to 20th	Night	12% 10% 3 7% 6% 5% 4 4 6% 8% 36%	3671
	21st to end	Night	19% 12% 2 8% 5% 3 3 3 5% 4 35%	3466
April	1st to 10th	Night	16% 10% 3 8% 5% 4 4 4 6% 7% 32%	1900
	11th to 20th	Night	19% 9% 2 6% 4 5% 4 3 4 6% 37%	1875
	21st to end	Night	20% 9% 3 7% 4 3 3 2 5% 6% 38%	1796
May	1st to 10th	Night	25% 10% 3 7% 5% 4 3 3 5% 6% 29%	2834
	11th to 20th	Night	19% 10% 3 8% 6% 5% 5% 3 5% 6% 30%	2564
	21st to end	Night	16% 6% 2 6% 4 4 4 4 5% 8% 40%	2738
June	1st to 10th	Night	17% 8% 2 5% 4 3 4 3 6% 8% 40%	1520
	11th to 20th	Night	16% 7% 3 6% 4 5% 4 5% 7% 8% 36%	1520
	21st to end	Night	15% 7% 2 6% 4 3 5% 4 6% 8% 41%	1520
July	1st to 10th	Night	13% 6% 2 6% 4 5% 5% 4 6% 9% 40%	2520
	11th to 20th	Night	16% 6% 3 6% 4 4 4 4 6% 8% 40%	2520
	21st to end	Night	17% 9% 3 7% 4 4 4 3 5% 6% 38%	2739
August	1st to 10th	Night	23% 7% 3 7% 4 5% 4 4 5% 6% 34%	2570
	11th to 20th	Night	15% 8% 3 6% 4 4 4 3 5% 7% 41%	3080
	21st to end	Night	9% 4 2 6% 4 4 3 3 5% 8% 50%	3476
September	1st to 10th	Night	14% 6% 2 6% 5% 3 4 3 5% 7% 45%	1900
	11th to 20th	Night	13% 6% 2 5% 3 3 3 3 5% 6% 52%	2014
	21st to end	Night	17% 7% 3 5% 3 3 4 3 5% 6% 44%	2090
October	1st to 10th	Night	20% 7% 3 6% 5% 3 4 3 5% 6% 39%	2145
	11th to 20th	Night	14% 8% 2 7% 3 4 4 3 5% 6% 44%	2289
	21st to end	Night	22% 9% 2 5% 4 4 3 4 5% 6% 36%	2717
November	1st to 10th	Night	14% 7% 3 6% 4 4 4 3 5% 5% 47%	2537
	11th to 20th	Night	17% 7% 2 6% 4 4 4 4 6% 5% 40%	2600
	21st to end	Night	14% 8% 3 6% 5% 5% 5% 4 6% 7% 38%	2680
December	1st to 10th	Night	19% 10% 3 7% 5% 4 4 4 6% 7% 31%	2800
	11th to 20th	Night	20% 9% 4 5% 5% 5% 5% 4 5% 6% 33%	3428
	21st to end	Night	21% 11% 5% 8% 5% 4 4 4 5% 6% 27%	4933

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	41% 6% 13% 32% 7% 1	2518
	11th to 20th	Day	53% 6% 12% 21% 7% 1	2520
	21st to end	Day	60% 4 10% 18% 8% 1	2842
February	1st to 10th	Day	51% 5% 14% 18% 10% 1	1736
	11th to 20th	Day	45% 6% 10% 23% 13% 2	1857
	21st to end	Day	51% 5% 12% 18% 12% 2	1570
March	1st to 10th	Day	57% 4 12% 15% 11% 2	3119
	11th to 20th	Day	42% 10% 15% 23% 8% 1	3256
	21st to end	Day	48% 5% 6% 18% 19% 4	4166
April	1st to 10th	Day	49% 6% 10% 20% 12% 3	2280
	11th to 20th	Day	46% 5% 10% 21% 16% 2	2254
	21st to end	Day	48% 6% 9% 19% 14% 4	2382
May	1st to 10th	Day	56% 6% 12% 14% 11% 1	4120
	11th to 20th	Day	50% 6% 15% 20% 8% 1	4360
	21st to end	Day	36% 9% 14% 26% 15% 1	4837
June	1st to 10th	Day	45% 9% 13% 22% 10% 1	2660
	11th to 20th	Day	44% 7% 14% 22% 11% 1	2660
	21st to end	Day	46% 7% 14% 20% 12% 1	2660
July	1st to 10th	Day	43% 8% 13% 21% 14% 1	4370
	11th to 20th	Day	39% 8% 16% 23% 12% 1	4365
	21st to end	Day	49% 7% 14% 15% 13% 1	4661
August	1st to 10th	Day	50% 8% 14% 20% 8%	4315
	11th to 20th	Day	42% 8% 16% 26% 7%	3779
	21st to end	Day	37% 7% 13% 29% 12% 1	4180
September	1st to 10th	Day	41% 7% 11% 24% 15% 1	2280
	11th to 20th	Day	36% 5% 10% 26% 22% 2	2164
	21st to end	Day	43% 5% 11% 22% 16% 2	2090
October	1st to 10th	Day	42% 5% 9% 19% 23% 2	3370
	11th to 20th	Day	34% 5% 10% 24% 23% 5%	3119
	21st to end	Day	36% 4 14% 26% 16% 4	3081
November	1st to 10th	Day	39% 5% 14% 25% 15% 2	1761
	11th to 20th	Day	41% 5% 11% 22% 18% 3	1800
	21st to end	Day	46% 5% 14% 24% 9% 2	1715
December	1st to 10th	Day	51% 6% 14% 18% 11% 1	1600
	11th to 20th	Day	45% 6% 16% 21% 12% 1	1986
	21st to end	Day	55% 7% 12% 15% 11%	2796
January	1st to 10th	Night	42% 4 15% 26% 10% 3	4429
	11th to 20th	Night	47% 5% 14% 21% 10% 2	4440
	21st to end	Night	57% 5% 11% 17% 9% 1	4811
February	1st to 10th	Night	46% 6% 15% 21% 10% 2	2442
	11th to 20th	Night	44% 7% 12% 20% 14% 2	2220
	21st to end	Night	47% 5% 12% 22% 10% 3	1884
March	1st to 10th	Night	54% 6% 11% 19% 10% 1	3734
	11th to 20th	Night	41% 7% 16% 25% 10% 2	3672
	21st to end	Night	47% 6% 7% 15% 20% 4	3466
April	1st to 10th	Night	49% 6% 10% 21% 12% 2	1900
	11th to 20th	Night	48% 6% 9% 20% 17% 1	1875
	21st to end	Night	46% 5% 10% 21% 15% 4	1796
May	1st to 10th	Night	55% 6% 12% 15% 9% 2	2840
	11th to 20th	Night	53% 8% 13% 16% 9% 2	2565
	21st to end	Night	39% 8% 17% 22% 13% 1	2739
June	1st to 10th	Night	42% 7% 13% 26% 12% 1	1520
	11th to 20th	Night	42% 7% 17% 22% 11%	1520
	21st to end	Night	39% 8% 15% 24% 13% 1	1520
July	1st to 10th	Night	40% 7% 17% 21% 15% 1	2480
	11th to 20th	Night	41% 7% 15% 25% 12%	2472
	21st to end	Night	45% 7% 13% 17% 16% 2	2651
August	1st to 10th	Night	49% 8% 14% 20% 8% 1	2560
	11th to 20th	Night	42% 7% 15% 29% 8%	3110
	21st to end	Night	29% 7% 15% 35% 14% 1	3476
September	1st to 10th	Night	39% 6% 12% 26% 16% 1	1900
	11th to 20th	Night	32% 6% 12% 26% 23% 1	2014
	21st to end	Night	40% 5% 11% 25% 18% 2	2090
October	1st to 10th	Night	42% 5% 13% 22% 17% 1	3574
	11th to 20th	Night	31% 4 12% 25% 22% 5%	3800
	21st to end	Night	35% 4 16% 29% 14% 2	4467
November	1st to 10th	Night	38% 5% 13% 22% 20% 3	2537
	11th to 20th	Night	42% 5% 12% 21% 17% 3	2600
	21st to end	Night	42% 6% 16% 26% 9% 1	2680
December	1st to 10th	Night	47% 7% 15% 22% 9%	2800
	11th to 20th	Night	45% 7% 16% 17% 12% 2	3428
	21st to end	Night	53% 6% 11% 20% 10%	4933

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	31% 26% 33% 8% 2	180
	11th to 20th	Day	33% 29% 29% 8% 1 1	180
	21st to end	Day	26% 29% 34% 8% 3 1	220
February	1st to 10th	Day	35% 32% 26% 5% 1	296
	11th to 20th	Day	36% 28% 27% 8% 2	456
	21st to end	Day	33% 26% 27% 12% 2	382
March	1st to 10th	Day	33% 23% 30% 12% 2	460
	11th to 20th	Day	33% 26% 30% 9% 1 1	460
	21st to end	Day	36% 24% 25% 9% 3 2	506
April	1st to 10th	Day	32% 24% 28% 10% 5% 1	460
	11th to 20th	Day	32% 25% 26% 12% 4 2	452
	21st to end	Day	29% 23% 29% 13% 5% 1	460
May	1st to 10th	Day	33% 22% 25% 13% 5% 2	463
	11th to 20th	Day	22% 22% 32% 18% 5% 1	487
	21st to end	Day	21% 14% 32% 20% 10% 3	529
June	1st to 10th	Day	18% 17% 33% 21% 9% 2	490
	11th to 20th	Day	19% 15% 34% 21% 9% 2	490
	21st to end	Day	18% 19% 31% 22% 8% 2	490
July	1st to 10th	Day	13% 11% 36% 25% 12% 2	485
	11th to 20th	Day	14% 8% 35% 30% 11% 2	484
	21st to end	Day	14% 12% 38% 24% 9% 2	532
August	1st to 10th	Day	16% 10% 28% 31% 10% 5%	486
	11th to 20th	Day	16% 10% 31% 25% 12% 6%	479
	21st to end	Day	13% 13% 29% 27% 13% 5%	539
September	1st to 10th	Day	20% 11% 26% 23% 16% 5%	490
	11th to 20th	Day	15% 13% 25% 23% 14% 9%	490
	21st to end	Day	21% 14% 31% 18% 11% 4	490
October	1st to 10th	Day	27% 15% 25% 18% 10% 5%	490
	11th to 20th	Day	22% 21% 27% 23% 5% 2	485
	21st to end	Day	32% 17% 29% 15% 6% 1	429
November	1st to 10th	Day	25% 22% 24% 21% 7% 1	395
	11th to 20th	Day	32% 25% 25% 15% 3 1	400
	21st to end	Day	33% 23% 26% 15% 3 1	315
December	1st to 10th	Day	29% 30% 28% 11% 4	200
	11th to 20th	Day	44% 21% 29% 5% 2	200
	21st to end	Day	28% 28% 31% 10% 1 1	204
January	1st to 10th	Night	24% 28% 31% 15% 2	760
	11th to 20th	Night	31% 22% 30% 15% 2	760
	21st to end	Night	23% 26% 32% 16% 2	836
February	1st to 10th	Night	27% 23% 32% 17% 2	760
	11th to 20th	Night	26% 27% 35% 11% 1	743
	21st to end	Night	32% 25% 27% 14% 2	628
March	1st to 10th	Night	28% 23% 32% 14% 3	760
	11th to 20th	Night	25% 27% 31% 15% 3	760
	21st to end	Night	28% 23% 29% 16% 4 1	836
April	1st to 10th	Night	27% 20% 34% 15% 3	760
	11th to 20th	Night	26% 22% 30% 17% 6%	751
	21st to end	Night	27% 21% 30% 18% 4	656
May	1st to 10th	Night	29% 16% 31% 18% 6%	570
	11th to 20th	Night	22% 16% 35% 24% 4	417
	21st to end	Night	19% 10% 30% 31% 9%	411
June	1st to 10th	Night	20% 11% 33% 27% 9%	380
	11th to 20th	Night	17% 9% 29% 35% 9% 1	380
	21st to end	Night	17% 11% 27% 34% 10% 1	380
July	1st to 10th	Night	15% 5% 28% 35% 16% 1	370
	11th to 20th	Night	16% 4 26% 39% 15% 1	368
	21st to end	Night	11% 9% 27% 40% 13%	416
August	1st to 10th	Night	14% 5% 25% 43% 12% 1	416
	11th to 20th	Night	16% 6% 26% 33% 17% 2	733
	21st to end	Night	15% 8% 24% 34% 17% 2	836
September	1st to 10th	Night	15% 9% 30% 30% 14% 2	760
	11th to 20th	Night	16% 10% 24% 28% 19% 4	760
	21st to end	Night	22% 9% 26% 29% 12% 3	760
October	1st to 10th	Night	25% 11% 26% 25% 11% 2	760
	11th to 20th	Night	21% 18% 28% 25% 7% 1	760
	21st to end	Night	28% 18% 28% 21% 5%	836
November	1st to 10th	Night	19% 21% 30% 22% 7% 1	780
	11th to 20th	Night	27% 21% 27% 18% 6% 1	800
	21st to end	Night	25% 21% 29% 21% 4 1	800
December	1st to 10th	Night	28% 25% 29% 15% 3	800
	11th to 20th	Night	31% 22% 29% 16% 3	800
	21st to end	Night	30% 26% 30% 12% 2	851

Page generated at 2024-12-21 04:13:53. Version ac07

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