Waterfall Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Waterfall Creek Observatory clear sky chart from 2005-11-06 to 2024-10-25.

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	12% 7% 2 6% 4 4 4 4 5% 7% 43%	101021
	Night	13% 8% 3 6% 4 3 4 3 5% 6% 45%	97833
Transparency	Day	39% 6% 11% 25% 16% 3	100818
	Night	39% 5% 11% 25% 17% 3	97708
Seeing	Day	18% 12% 28% 25% 14% 4	15530
	Night	18% 12% 30% 25% 12% 2	25308

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	12% 14% 4 8% 3 3 3 3 5% 5% 41%	2600
	11th to 20th	Day	13% 10% 3 7% 4 4 3 3 3 6% 43%	2850
	21st to end	Day	22% 9% 3 7% 3 3 3 2 4 5% 39%	3135
February	1st to 10th	Day	15% 11% 3 8% 4 5% 4 3 4 6% 36%	1710
	11th to 20th	Day	15% 9% 2 7% 4 4 4 4 4 7% 40%	1807
	21st to end	Day	15% 11% 2 6% 5% 5% 4 3 6% 6% 38%	1570
March	1st to 10th	Day	19% 13% 3 6% 3 3 3 3 4 4 40%	3294
	11th to 20th	Day	13% 7% 2 5% 3 3 3 2 4 6% 51%	3480
	21st to end	Day	15% 7% 2 7% 5% 4 4 4 6% 6% 39%	3956
April	1st to 10th	Day	11% 7% 2 6% 5% 4 4 3 5% 8% 45%	2280
	11th to 20th	Day	16% 8% 3 6% 5% 4 4 3 6% 5% 40%	2254
	21st to end	Day	19% 8% 3 6% 5% 5% 4 3 5% 6% 37%	2280
May	1st to 10th	Day	14% 8% 3 8% 5% 5% 5% 6% 7% 9% 32%	3765
	11th to 20th	Day	17% 8% 2 6% 4 4 4 3 6% 8% 38%	4287
	21st to end	Day	13% 7% 2 7% 5% 4 5% 3 5% 7% 41%	4824
June	1st to 10th	Day	9% 6% 2 6% 5% 4 6% 5% 6% 8% 42%	2660
	11th to 20th	Day	6% 4 2 5% 4 5% 5% 4 7% 9% 49%	2660
	21st to end	Day	5% 3 2 5% 4 6% 4 5% 8% 9% 48%	2660
July	1st to 10th	Day	12% 4 2 6% 5% 5% 5% 4 7% 8% 41%	4440
	11th to 20th	Day	4 3 1 6% 4 5% 5% 4 7% 11% 50%	4297
	21st to end	Day	8% 6% 2 8% 7% 6% 6% 6% 7% 10% 34%	4465
August	1st to 10th	Day	5% 3 2 4 4 4 4 4 7% 9% 54%	4104
	11th to 20th	Day	12% 5% 2 6% 5% 5% 5% 4 5% 8% 44%	3738
	21st to end	Day	8% 4 2 5% 3 4 5% 4 6% 9% 52%	4180
September	1st to 10th	Day	12% 5% 2 5% 3 4 4 4 5% 7% 50%	2280
	11th to 20th	Day	11% 6% 2 6% 4 3 4 3 6% 7% 48%	2280
	21st to end	Day	10% 6% 2 5% 4 3 4 3 5% 7% 51%	2036
October	1st to 10th	Day	9% 4 2 5% 4 3 3 3 4 6% 57%	1900
	11th to 20th	Day	14% 6% 2 5% 3 2 3 2 3 5% 54%	1900
	21st to end	Day	19% 8% 2 4 3 3 4 2 4 4 47%	2026
November	1st to 10th	Day	11% 6% 2 4 4 3 4 3 4 5% 54%	1736
	11th to 20th	Day	12% 8% 2 5% 4 3 3 2 5% 7% 47%	1710
	21st to end	Day	16% 10% 3 6% 4 3 3 3 4 5% 44%	1636
December	1st to 10th	Day	14% 9% 3 7% 4 4 3 4 5% 7% 40%	1520
	11th to 20th	Day	14% 10% 5% 8% 6% 4 4 3 3 4 39%	1918
	21st to end	Day	14% 18% 4 8% 4 4 4 3 4 5% 31%	2783
January	1st to 10th	Night	14% 10% 5% 9% 5% 4 4 3 5% 5% 38%	4352
	11th to 20th	Night	13% 9% 3 9% 6% 4 5% 4 5% 6% 37%	4120
	21st to end	Night	21% 12% 5% 7% 4 2 3 3 4 5% 34%	4532
February	1st to 10th	Night	17% 10% 3 7% 4 3 3 3 5% 7% 38%	2470
	11th to 20th	Night	15% 7% 4 8% 4 3 3 3 4 7% 44%	2257
	21st to end	Night	16% 9% 3 7% 5% 4 3 3 4 5% 41%	1884
March	1st to 10th	Night	20% 11% 3 5% 3 2 3 2 4 4 42%	3587
	11th to 20th	Night	13% 7% 2 6% 3 3 3 3 4 5% 49%	3480
	21st to end	Night	14% 10% 4 8% 5% 4 4 3 5% 7% 36%	3673
April	1st to 10th	Night	10% 6% 2 5% 4 3 3 3 6% 7% 50%	1900
	11th to 20th	Night	14% 7% 3 6% 5% 4 4 3 4 7% 45%	1875
	21st to end	Night	19% 7% 2 6% 4 4 3 2 5% 6% 41%	1900
May	1st to 10th	Night	18% 7% 2 4 3 3 3 3 5% 7% 43%	3130
	11th to 20th	Night	15% 8% 2 6% 4 4 3 3 5% 8% 43%	2597
	21st to end	Night	13% 8% 3 7% 5% 5% 5% 3 6% 7% 38%	2743
June	1st to 10th	Night	8% 4 2 5% 4 4 5% 4 7% 10% 47%	1520
	11th to 20th	Night	6% 3 2 4 3 2 3 3 6% 11% 57%	1520
	21st to end	Night	3 3 1 4 3 4 4 4 7% 10% 58%	1520
July	1st to 10th	Night	11% 4 2 5% 4 5% 4 4 6% 9% 48%	2530
	11th to 20th	Night	5% 3 1 4 3 3 4 2 5% 8% 62%	2654
	21st to end	Night	9% 6% 2 8% 5% 5% 5% 4 7% 8% 41%	3098
August	1st to 10th	Night	3 3 1 4 3 3 4 4 6% 7% 62%	2836
	11th to 20th	Night	9% 7% 2 5% 4 5% 4 3 6% 8% 48%	3091
	21st to end	Night	5% 4 1 4 3 3 3 4 6% 8% 58%	3476
September	1st to 10th	Night	10% 5% 2 4 4 3 3 3 5% 7% 54%	1900
	11th to 20th	Night	9% 6% 2 5% 3 3 3 4 6% 7% 53%	1900
	21st to end	Night	9% 5% 2 4 3 4 4 3 5% 6% 55%	2120
October	1st to 10th	Night	7% 4 1 4 3 3 3 3 4 6% 63%	2280
	11th to 20th	Night	13% 6% 2 3 4 3 3 2 4 4 55%	2280
	21st to end	Night	19% 6% 2 4 3 3 3 2 3 4 49%	2436
November	1st to 10th	Night	10% 6% 2 4 3 3 3 3 4 6% 57%	2338
	11th to 20th	Night	14% 6% 2 5% 4 3 4 3 4 6% 49%	2470
	21st to end	Night	18% 10% 2 5% 4 3 2 2 4 6% 45%	2541
December	1st to 10th	Night	17% 9% 2 6% 4 3 4 3 5% 7% 39%	2660
	11th to 20th	Night	16% 9% 4 7% 4 4 4 3 3 6% 41%	3279
	21st to end	Night	17% 17% 6% 9% 4 4 4 3 4 5% 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	45% 4 7% 28% 13% 2	2601
	11th to 20th	Day	44% 4 8% 25% 16% 3	2850
	21st to end	Day	50% 3 8% 17% 16% 6%	3135
February	1st to 10th	Day	49% 3 10% 22% 13% 2	1710
	11th to 20th	Day	44% 5% 12% 20% 14% 5%	1817
	21st to end	Day	47% 4 8% 23% 12% 7%	1570
March	1st to 10th	Day	49% 4 6% 20% 12% 9%	3294
	11th to 20th	Day	35% 4 9% 28% 17% 7%	3480
	21st to end	Day	43% 7% 15% 22% 12% 1	3956
April	1st to 10th	Day	37% 4 12% 25% 20% 1	2280
	11th to 20th	Day	45% 4 10% 21% 17% 4	2254
	21st to end	Day	49% 5% 10% 21% 14% 1	2280
May	1st to 10th	Day	45% 10% 12% 21% 12% 1	3800
	11th to 20th	Day	44% 7% 11% 24% 13% 1	4291
	21st to end	Day	42% 6% 9% 23% 19% 1	4837
June	1st to 10th	Day	37% 7% 13% 25% 15% 2	2660
	11th to 20th	Day	29% 6% 13% 29% 19% 3	2660
	21st to end	Day	28% 7% 19% 25% 16% 5%	2660
July	1st to 10th	Day	39% 6% 12% 29% 11% 2	4371
	11th to 20th	Day	28% 7% 13% 35% 16% 2	4222
	21st to end	Day	40% 10% 15% 26% 7% 1	4325
August	1st to 10th	Day	25% 6% 16% 31% 21%	4090
	11th to 20th	Day	39% 6% 13% 24% 17% 2	3774
	21st to end	Day	29% 6% 14% 36% 12% 3	4179
September	1st to 10th	Day	34% 5% 11% 28% 17% 6%	2280
	11th to 20th	Day	35% 5% 8% 26% 25% 2	2280
	21st to end	Day	33% 5% 6% 28% 25% 2	2036
October	1st to 10th	Day	29% 4 10% 24% 29% 4	1900
	11th to 20th	Day	34% 3 6% 25% 25% 6%	1900
	21st to end	Day	42% 3 6% 25% 19% 5%	2026
November	1st to 10th	Day	33% 4 9% 25% 21% 7%	1736
	11th to 20th	Day	38% 3 7% 23% 22% 7%	1710
	21st to end	Day	44% 3 8% 25% 18% 2	1636
December	1st to 10th	Day	44% 4 9% 27% 14% 2	1520
	11th to 20th	Day	49% 4 6% 19% 21% 1	1915
	21st to end	Day	54% 6% 9% 15% 13% 2	2783
January	1st to 10th	Night	47% 5% 8% 23% 14% 2	4352
	11th to 20th	Night	45% 7% 8% 25% 13% 2	4120
	21st to end	Night	53% 4 8% 21% 13% 1	4532
February	1st to 10th	Night	48% 4 10% 22% 15% 2	2470
	11th to 20th	Night	43% 3 12% 22% 17% 3	2258
	21st to end	Night	46% 4 7% 22% 16% 5%	1884
March	1st to 10th	Night	47% 4 7% 23% 15% 5%	3587
	11th to 20th	Night	36% 6% 10% 24% 19% 5%	3480
	21st to end	Night	45% 7% 13% 25% 9%	3673
April	1st to 10th	Night	33% 4 12% 26% 21% 4	1900
	11th to 20th	Night	40% 4 10% 24% 17% 5%	1875
	21st to end	Night	45% 3 9% 25% 16% 2	1900
May	1st to 10th	Night	38% 8% 16% 22% 14% 2	3160
	11th to 20th	Night	39% 7% 13% 24% 15% 1	2598
	21st to end	Night	43% 7% 11% 23% 14% 1	2751
June	1st to 10th	Night	32% 7% 15% 24% 19% 2	1520
	11th to 20th	Night	22% 5% 13% 36% 21% 4	1520
	21st to end	Night	20% 7% 16% 31% 18% 7%	1520
July	1st to 10th	Night	34% 6% 15% 27% 15% 3	2490
	11th to 20th	Night	21% 5% 12% 39% 20% 2	2606
	21st to end	Night	38% 8% 16% 26% 12% 1	2999
August	1st to 10th	Night	20% 6% 18% 33% 22% 1	2826
	11th to 20th	Night	35% 6% 16% 24% 16% 3	3121
	21st to end	Night	24% 5% 15% 38% 15% 3	3476
September	1st to 10th	Night	31% 5% 10% 29% 21% 5%	1900
	11th to 20th	Night	31% 5% 11% 26% 25% 2	1900
	21st to end	Night	30% 5% 9% 26% 27% 3	2120
October	1st to 10th	Night	23% 4 11% 28% 29% 6%	2280
	11th to 20th	Night	33% 3 7% 26% 25% 6%	2280
	21st to end	Night	40% 3 7% 23% 22% 5%	2436
November	1st to 10th	Night	30% 4 11% 27% 22% 6%	2338
	11th to 20th	Night	37% 3 6% 23% 23% 7%	2470
	21st to end	Night	44% 3 6% 25% 21% 2	2541
December	1st to 10th	Night	44% 5% 10% 23% 17% 2	2660
	11th to 20th	Night	46% 3 8% 24% 18% 2	3281
	21st to end	Night	59% 6% 7% 16% 9% 2	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	30% 21% 34% 11% 3	270
	11th to 20th	Day	33% 24% 34% 8% 1	270
	21st to end	Day	25% 30% 33% 12% 1	297
February	1st to 10th	Day	29% 25% 33% 11% 2	270
	11th to 20th	Day	33% 24% 32% 9% 1 1	270
	21st to end	Day	37% 24% 30% 7% 1	225
March	1st to 10th	Day	28% 20% 39% 12% 1	270
	11th to 20th	Day	36% 16% 35% 10% 2	270
	21st to end	Day	34% 19% 35% 10% 2	375
April	1st to 10th	Day	24% 19% 35% 17% 4 1	460
	11th to 20th	Day	27% 21% 29% 17% 5% 1	452
	21st to end	Day	28% 18% 32% 17% 3 1	460
May	1st to 10th	Day	22% 19% 35% 19% 5% 1	463
	11th to 20th	Day	20% 12% 31% 23% 11% 3	659
	21st to end	Day	15% 8% 35% 26% 12% 4	734
June	1st to 10th	Day	11% 6% 25% 30% 23% 5%	680
	11th to 20th	Day	8% 3 25% 39% 21% 4	680
	21st to end	Day	5% 7% 34% 32% 18% 4	680
July	1st to 10th	Day	13% 3 18% 31% 28% 8%	671
	11th to 20th	Day	5% 3 21% 37% 28% 6%	668
	21st to end	Day	9% 2 19% 36% 27% 7%	739
August	1st to 10th	Day	10% 3 17% 40% 24% 7%	676
	11th to 20th	Day	15% 3 20% 30% 25% 7%	488
	21st to end	Day	14% 2 14% 30% 29% 11%	539
September	1st to 10th	Day	13% 4 18% 34% 23% 8%	490
	11th to 20th	Day	11% 3 21% 32% 23% 10%	490
	21st to end	Day	13% 10% 24% 29% 18% 7%	426
October	1st to 10th	Day	12% 11% 30% 33% 11% 3	300
	11th to 20th	Day	23% 12% 38% 21% 5% 1	300
	21st to end	Day	34% 19% 26% 18% 2	311
November	1st to 10th	Day	15% 16% 38% 25% 4 2	270
	11th to 20th	Day	24% 17% 34% 17% 7%	270
	21st to end	Day	29% 17% 33% 16% 5% 1	270
December	1st to 10th	Day	21% 23% 33% 16% 5% 2	270
	11th to 20th	Day	28% 19% 36% 14% 3	270
	21st to end	Day	30% 24% 34% 9% 2 1	297
January	1st to 10th	Night	22% 23% 37% 16% 3	950
	11th to 20th	Night	26% 25% 33% 13% 3	950
	21st to end	Night	22% 22% 39% 16% 2	1045
February	1st to 10th	Night	25% 20% 36% 17% 1	950
	11th to 20th	Night	22% 22% 40% 15% 1	782
	21st to end	Night	26% 22% 35% 14% 2	628
March	1st to 10th	Night	26% 15% 37% 19% 2	679
	11th to 20th	Night	26% 13% 36% 21% 4	570
	21st to end	Night	25% 18% 34% 19% 4	627
April	1st to 10th	Night	17% 19% 39% 22% 3	570
	11th to 20th	Night	20% 16% 34% 24% 6%	563
	21st to end	Night	21% 13% 38% 21% 7%	570
May	1st to 10th	Night	18% 8% 37% 29% 8%	570
	11th to 20th	Night	19% 6% 33% 26% 14% 1	561
	21st to end	Night	13% 5% 29% 33% 16% 3	617
June	1st to 10th	Night	9% 4 21% 35% 29% 3	570
	11th to 20th	Night	6% 2 24% 44% 23% 2	570
	21st to end	Night	4 2 26% 39% 26% 3	570
July	1st to 10th	Night	9% 3 13% 36% 30% 10%	555
	11th to 20th	Night	6% 2 14% 42% 31% 5%	552
	21st to end	Night	8% 2 14% 41% 32% 4	624
August	1st to 10th	Night	7% 1 13% 41% 34% 4	567
	11th to 20th	Night	9% 2 15% 39% 30% 4	564
	21st to end	Night	8% 13% 35% 36% 7%	627
September	1st to 10th	Night	12% 3 15% 36% 29% 5%	570
	11th to 20th	Night	12% 2 14% 37% 30% 5%	570
	21st to end	Night	13% 6% 24% 27% 25% 4	729
October	1st to 10th	Night	9% 4 29% 31% 23% 3	760
	11th to 20th	Night	17% 12% 34% 27% 10% 1	760
	21st to end	Night	26% 12% 34% 22% 6%	812
November	1st to 10th	Night	14% 13% 40% 25% 8% 1	740
	11th to 20th	Night	20% 16% 32% 25% 7% 1	760
	21st to end	Night	23% 17% 35% 20% 5%	831
December	1st to 10th	Night	25% 15% 37% 19% 4	950
	11th to 20th	Night	25% 14% 35% 21% 3	950
	21st to end	Night	28% 20% 33% 18% 2	1045

Page generated at 2024-10-22 19:21:03. Version ac07

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