Hidden Bend Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hidden Bend Observatory clear sky chart from 2005-11-06 to 2024-11-01.

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% 8% 3 7% 5% 5% 5% 4 6% 7% 38%	101088
	Night	14% 8% 3 7% 5% 4 5% 4 6% 7% 39%	97789
Transparency	Day	44% 6% 11% 24% 13% 2	100896
	Night	44% 6% 12% 24% 13% 2	97651
Seeing	Day	22% 14% 25% 22% 13% 4	14865
	Night	19% 13% 24% 30% 12% 1	24504

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	15% 13% 4 8% 5% 4 3 3 4 5% 36%	2776
	11th to 20th	Day	10% 16% 6% 11% 8% 5% 4 4 4 4 28%	2840
	21st to end	Day	16% 12% 4 8% 6% 5% 5% 4 5% 6% 31%	3124
February	1st to 10th	Day	14% 13% 3 8% 5% 4 4 3 5% 6% 34%	1710
	11th to 20th	Day	14% 10% 3 9% 5% 6% 4 4 6% 6% 34%	1663
	21st to end	Day	15% 10% 3 9% 5% 4 4 3 4 6% 36%	1594
March	1st to 10th	Day	19% 11% 3 7% 5% 4 4 3 5% 6% 33%	3435
	11th to 20th	Day	13% 7% 3 5% 3 3 4 3 6% 7% 46%	3480
	21st to end	Day	16% 10% 3 7% 5% 4 4 3 5% 6% 37%	3815
April	1st to 10th	Day	11% 11% 3 8% 5% 4 4 5% 5% 8% 36%	2239
	11th to 20th	Day	13% 7% 2 7% 5% 4 4 4 4 7% 43%	2254
	21st to end	Day	18% 7% 3 6% 5% 4 5% 3 6% 6% 38%	2375
May	1st to 10th	Day	23% 7% 3 8% 6% 5% 4 4 6% 6% 29%	4082
	11th to 20th	Day	22% 8% 2 6% 4 4 4 4 6% 7% 32%	4081
	21st to end	Day	11% 4 2 6% 5% 5% 5% 4 7% 10% 41%	4814
June	1st to 10th	Day	11% 5% 3 6% 5% 5% 4 5% 6% 10% 39%	2660
	11th to 20th	Day	10% 6% 2 6% 5% 6% 6% 6% 7% 9% 38%	2660
	21st to end	Day	9% 5% 2 6% 5% 4 6% 4 7% 10% 42%	2660
July	1st to 10th	Day	5% 4 2 7% 5% 6% 6% 5% 7% 10% 44%	4377
	11th to 20th	Day	6% 5% 2 7% 5% 5% 6% 5% 7% 10% 41%	4120
	21st to end	Day	11% 7% 3 8% 6% 5% 5% 5% 6% 8% 37%	4466
August	1st to 10th	Day	14% 6% 3 6% 5% 5% 6% 4 7% 9% 33%	4104
	11th to 20th	Day	8% 5% 2 6% 5% 5% 7% 5% 7% 8% 41%	4028
	21st to end	Day	8% 4 2 5% 4 5% 5% 4 6% 8% 48%	4180
September	1st to 10th	Day	15% 4 2 6% 3 4 5% 4 5% 7% 45%	2280
	11th to 20th	Day	12% 5% 2 5% 4 4 5% 3 6% 7% 46%	2185
	21st to end	Day	18% 8% 3 6% 4 5% 3 3 5% 6% 38%	2035
October	1st to 10th	Day	17% 6% 2 5% 4 3 3 3 5% 6% 46%	1900
	11th to 20th	Day	15% 5% 2 6% 6% 4 4 4 5% 5% 44%	1900
	21st to end	Day	14% 7% 2 6% 4 4 4 3 5% 7% 45%	2090
November	1st to 10th	Day	10% 6% 3 5% 3 4 4 3 5% 5% 52%	1857
	11th to 20th	Day	13% 10% 3 6% 5% 4 4 3 5% 6% 41%	1582
	21st to end	Day	15% 9% 1 5% 6% 4 4 4 5% 7% 39%	1520
December	1st to 10th	Day	16% 10% 4 8% 5% 5% 5% 4 6% 6% 30%	1520
	11th to 20th	Day	14% 13% 5% 7% 4 4 4 3 5% 5% 35%	1910
	21st to end	Day	16% 10% 3 8% 7% 5% 5% 4 6% 6% 29%	2772
January	1st to 10th	Night	10% 15% 4 9% 5% 6% 5% 4 6% 6% 30%	4164
	11th to 20th	Night	15% 10% 4 11% 4 4 4 3 5% 5% 36%	4120
	21st to end	Night	18% 12% 4 9% 5% 4 5% 3 4 5% 32%	4532
February	1st to 10th	Night	13% 9% 3 8% 5% 5% 4 4 6% 6% 37%	2470
	11th to 20th	Night	14% 10% 4 8% 6% 5% 5% 4 5% 6% 34%	2403
	21st to end	Night	14% 11% 5% 8% 6% 4 3 4 5% 6% 33%	1856
March	1st to 10th	Night	20% 9% 2 6% 4 4 5% 3 5% 6% 36%	3418
	11th to 20th	Night	11% 13% 3 6% 4 3 3 2 4 6% 43%	3480
	21st to end	Night	15% 8% 2 6% 4 3 4 2 5% 5% 46%	3817
April	1st to 10th	Night	15% 11% 3 7% 4 4 5% 3 5% 5% 38%	1939
	11th to 20th	Night	13% 7% 2 6% 4 4 5% 3 7% 8% 41%	1875
	21st to end	Night	16% 7% 2 6% 4 5% 3 4 5% 7% 42%	1819
May	1st to 10th	Night	25% 7% 3 7% 4 4 4 4 6% 7% 29%	2813
	11th to 20th	Night	22% 8% 2 7% 4 4 3 3 5% 6% 35%	2812
	21st to end	Night	11% 5% 2 5% 5% 5% 5% 5% 7% 9% 42%	2741
June	1st to 10th	Night	10% 5% 1 5% 4 4 5% 4 6% 8% 47%	1520
	11th to 20th	Night	10% 5% 2 6% 6% 5% 5% 4 6% 9% 43%	1520
	21st to end	Night	8% 4 2 5% 6% 4 4 5% 7% 10% 45%	1520
July	1st to 10th	Night	6% 4 2 6% 5% 5% 6% 4 7% 10% 44%	2577
	11th to 20th	Night	5% 5% 2 7% 6% 5% 7% 5% 6% 10% 42%	2840
	21st to end	Night	9% 7% 3 8% 5% 5% 6% 5% 7% 9% 37%	3087
August	1st to 10th	Night	14% 5% 3 6% 4 5% 5% 5% 7% 9% 37%	2825
	11th to 20th	Night	10% 5% 2 6% 4 5% 5% 4 6% 8% 44%	2785
	21st to end	Night	9% 5% 2 6% 4 5% 4 4 6% 8% 48%	3444
September	1st to 10th	Night	13% 5% 2 6% 4 4 5% 3 6% 6% 47%	1900
	11th to 20th	Night	12% 6% 2 4 3 4 3 3 6% 7% 51%	1990
	21st to end	Night	19% 6% 2 6% 3 4 5% 4 5% 7% 41%	2144
October	1st to 10th	Night	17% 5% 2 6% 3 4 4 3 5% 6% 46%	2280
	11th to 20th	Night	14% 5% 2 6% 3 3 4 3 6% 7% 49%	2280
	21st to end	Night	16% 6% 2 6% 4 4 4 3 4 5% 47%	2508
November	1st to 10th	Night	9% 9% 3 6% 3 4 4 3 5% 6% 48%	2228
	11th to 20th	Night	13% 9% 3 7% 4 5% 4 3 5% 6% 42%	2593
	21st to end	Night	12% 8% 3 7% 6% 5% 5% 4 6% 6% 38%	2660
December	1st to 10th	Night	15% 10% 4 8% 7% 4 5% 4 5% 6% 33%	2660
	11th to 20th	Night	15% 9% 4 7% 5% 5% 4 4 5% 6% 35%	3285
	21st to end	Night	16% 10% 3 8% 6% 6% 6% 5% 7% 7% 27%	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	51% 5% 9% 25% 10% 2	2777
	11th to 20th	Day	60% 4 8% 16% 10% 2	2840
	21st to end	Day	54% 4 10% 21% 9% 1	3124
February	1st to 10th	Day	51% 5% 12% 21% 10% 1	1710
	11th to 20th	Day	50% 5% 11% 20% 12% 2	1672
	21st to end	Day	49% 4 11% 20% 13% 2	1594
March	1st to 10th	Day	53% 4 10% 23% 10% 1	3435
	11th to 20th	Day	38% 4 7% 32% 18% 2	3480
	21st to end	Day	48% 5% 10% 23% 12% 2	3815
April	1st to 10th	Day	47% 5% 12% 19% 15% 3	2239
	11th to 20th	Day	42% 4 11% 21% 17% 5%	2254
	21st to end	Day	47% 5% 10% 23% 13% 2	2375
May	1st to 10th	Day	54% 6% 9% 21% 9% 1	4120
	11th to 20th	Day	51% 6% 8% 25% 8% 1	4085
	21st to end	Day	37% 8% 13% 25% 14% 2	4828
June	1st to 10th	Day	39% 8% 12% 24% 15% 1	2660
	11th to 20th	Day	40% 10% 13% 23% 13% 1	2660
	21st to end	Day	36% 8% 15% 26% 13% 2	2660
July	1st to 10th	Day	34% 10% 15% 27% 11% 4	4308
	11th to 20th	Day	34% 9% 16% 28% 12% 1	4051
	21st to end	Day	44% 7% 10% 22% 16% 1	4324
August	1st to 10th	Day	44% 10% 15% 24% 8%	4091
	11th to 20th	Day	36% 8% 12% 29% 14%	4067
	21st to end	Day	31% 9% 15% 28% 15% 1	4180
September	1st to 10th	Day	38% 6% 13% 20% 20% 4	2280
	11th to 20th	Day	36% 6% 9% 28% 18% 3	2185
	21st to end	Day	46% 6% 10% 21% 16% 1	2035
October	1st to 10th	Day	39% 4 11% 26% 16% 3	1900
	11th to 20th	Day	42% 5% 10% 24% 17% 2	1900
	21st to end	Day	39% 5% 10% 26% 18% 2	2090
November	1st to 10th	Day	34% 4 11% 26% 21% 4	1857
	11th to 20th	Day	43% 5% 11% 18% 19% 3	1582
	21st to end	Day	45% 4 12% 25% 13% 1	1520
December	1st to 10th	Day	53% 5% 12% 21% 8% 1	1520
	11th to 20th	Day	51% 3 11% 25% 8% 2	1906
	21st to end	Day	54% 5% 13% 17% 10% 1	2772
January	1st to 10th	Night	54% 5% 9% 20% 11% 1	4164
	11th to 20th	Night	51% 5% 10% 22% 10% 2	4120
	21st to end	Night	55% 5% 9% 23% 7% 1	4532
February	1st to 10th	Night	46% 5% 13% 24% 11% 1	2470
	11th to 20th	Night	51% 6% 10% 19% 13% 1	2405
	21st to end	Night	52% 5% 10% 20% 10% 4	1856
March	1st to 10th	Night	49% 4 8% 29% 8% 1	3418
	11th to 20th	Night	43% 5% 8% 32% 11% 1	3480
	21st to end	Night	41% 5% 9% 26% 17% 3	3817
April	1st to 10th	Night	47% 6% 10% 19% 15% 3	1939
	11th to 20th	Night	40% 7% 11% 22% 15% 5%	1875
	21st to end	Night	41% 7% 10% 25% 14% 3	1819
May	1st to 10th	Night	53% 7% 10% 19% 9% 2	2840
	11th to 20th	Night	52% 5% 9% 24% 9% 1	2813
	21st to end	Night	36% 9% 16% 26% 9% 4	2748
June	1st to 10th	Night	35% 8% 12% 28% 16% 2	1520
	11th to 20th	Night	38% 8% 13% 27% 13% 1	1520
	21st to end	Night	33% 8% 16% 26% 16% 2	1520
July	1st to 10th	Night	33% 9% 21% 21% 12% 5%	2536
	11th to 20th	Night	34% 11% 16% 25% 13% 1	2786
	21st to end	Night	39% 10% 14% 21% 14% 1	2988
August	1st to 10th	Night	40% 10% 17% 24% 8%	2814
	11th to 20th	Night	36% 7% 13% 25% 18% 1	2812
	21st to end	Night	34% 7% 14% 32% 13% 1	3444
September	1st to 10th	Night	37% 7% 13% 20% 19% 4	1900
	11th to 20th	Night	33% 5% 10% 30% 20% 2	1990
	21st to end	Night	43% 7% 11% 22% 17% 1	2144
October	1st to 10th	Night	38% 6% 11% 26% 17% 2	2280
	11th to 20th	Night	34% 6% 10% 28% 20% 2	2280
	21st to end	Night	39% 4 9% 26% 19% 2	2508
November	1st to 10th	Night	37% 5% 12% 23% 19% 4	2228
	11th to 20th	Night	43% 4 8% 25% 16% 4	2593
	21st to end	Night	46% 4 12% 22% 14% 2	2660
December	1st to 10th	Night	52% 6% 11% 22% 9% 1	2660
	11th to 20th	Night	49% 6% 10% 22% 13% 1	3288
	21st to end	Night	54% 7% 14% 16% 9%	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	36% 26% 20% 13% 4 1	254
	11th to 20th	Day	38% 22% 28% 10% 3	270
	21st to end	Day	34% 21% 30% 11% 4	297
February	1st to 10th	Day	33% 23% 28% 13% 3	270
	11th to 20th	Day	46% 19% 28% 7%	270
	21st to end	Day	35% 24% 23% 16% 1	336
March	1st to 10th	Day	30% 22% 23% 21% 3	460
	11th to 20th	Day	34% 21% 25% 14% 5%	460
	21st to end	Day	27% 20% 31% 16% 6% 1	506
April	1st to 10th	Day	27% 25% 21% 20% 6% 1	460
	11th to 20th	Day	22% 19% 28% 18% 9% 3	452
	21st to end	Day	29% 18% 26% 18% 7% 2	460
May	1st to 10th	Day	26% 18% 27% 19% 8% 3	463
	11th to 20th	Day	25% 16% 27% 19% 11% 2	487
	21st to end	Day	16% 9% 28% 22% 19% 6%	529
June	1st to 10th	Day	17% 11% 29% 23% 16% 4	490
	11th to 20th	Day	14% 12% 29% 23% 15% 7%	490
	21st to end	Day	11% 13% 28% 28% 16% 4	490
July	1st to 10th	Day	10% 6% 24% 27% 24% 9%	485
	11th to 20th	Day	7% 6% 25% 30% 23% 8%	484
	21st to end	Day	15% 5% 23% 30% 22% 6%	532
August	1st to 10th	Day	12% 9% 21% 28% 21% 9%	486
	11th to 20th	Day	12% 5% 24% 26% 22% 11%	479
	21st to end	Day	10% 7% 21% 29% 24% 10%	539
September	1st to 10th	Day	17% 7% 21% 24% 22% 9%	490
	11th to 20th	Day	13% 6% 21% 26% 23% 11%	490
	21st to end	Day	27% 10% 21% 23% 15% 3	490
October	1st to 10th	Day	20% 9% 21% 27% 19% 4	490
	11th to 20th	Day	19% 16% 24% 24% 14% 3	490
	21st to end	Day	20% 16% 28% 23% 10% 3	539
November	1st to 10th	Day	17% 13% 25% 27% 15% 2	455
	11th to 20th	Day	24% 15% 34% 18% 8% 1	234
	21st to end	Day	27% 17% 30% 21% 4 1	180
December	1st to 10th	Day	31% 19% 29% 13% 6% 1	180
	11th to 20th	Day	36% 18% 23% 21% 3	180
	21st to end	Day	26% 19% 26% 23% 5% 1	198
January	1st to 10th	Night	24% 22% 32% 19% 3	760
	11th to 20th	Night	25% 20% 30% 24% 2	760
	21st to end	Night	24% 21% 33% 20% 2	836
February	1st to 10th	Night	23% 19% 28% 28% 2	760
	11th to 20th	Night	27% 26% 29% 16% 1	743
	21st to end	Night	29% 21% 32% 17% 2	628
March	1st to 10th	Night	24% 17% 33% 23% 3	760
	11th to 20th	Night	28% 20% 25% 21% 5% 1	760
	21st to end	Night	23% 17% 33% 21% 5% 1	836
April	1st to 10th	Night	25% 19% 29% 22% 5%	760
	11th to 20th	Night	19% 17% 29% 27% 8%	751
	21st to end	Night	22% 13% 26% 31% 9%	679
May	1st to 10th	Night	21% 11% 22% 32% 14% 1	570
	11th to 20th	Night	19% 8% 24% 35% 13% 1	561
	21st to end	Night	11% 4 23% 38% 21% 2	421
June	1st to 10th	Night	9% 4 27% 39% 19% 1	380
	11th to 20th	Night	13% 6% 17% 40% 22% 2	380
	21st to end	Night	7% 4 24% 47% 17% 1	380
July	1st to 10th	Night	9% 3 13% 46% 25% 5%	400
	11th to 20th	Night	7% 3 12% 40% 36% 3	552
	21st to end	Night	9% 3 18% 37% 31% 2	624
August	1st to 10th	Night	10% 2 12% 46% 28% 3	567
	11th to 20th	Night	10% 3 10% 46% 29% 3	564
	21st to end	Night	11% 3 14% 39% 30% 3	817
September	1st to 10th	Night	15% 4 15% 38% 24% 5%	760
	11th to 20th	Night	15% 5% 12% 33% 31% 3	760
	21st to end	Night	20% 7% 18% 33% 20% 2	760
October	1st to 10th	Night	18% 8% 20% 31% 20% 3	760
	11th to 20th	Night	17% 13% 25% 32% 13% 1	760
	21st to end	Night	20% 12% 26% 31% 11% 1	836
November	1st to 10th	Night	15% 12% 24% 35% 12% 1	743
	11th to 20th	Night	22% 17% 25% 28% 9% 1	760
	21st to end	Night	20% 18% 26% 31% 5%	760
December	1st to 10th	Night	26% 16% 28% 25% 4	760
	11th to 20th	Night	19% 20% 30% 28% 3	760
	21st to end	Night	23% 16% 29% 30% 2	836

Page generated at 2024-10-29 11:20:49. Version ac07

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