Crystal Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crystal Creek Observatory clear sky chart from 2005-11-06 to 2024-12-09.

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 6% 7% 43%	101119
	Night	13% 7% 2 5% 4 4 4 3 5% 7% 47%	98682
Transparency	Day	38% 6% 11% 23% 19% 4	104851
	Night	35% 5% 10% 23% 21% 6%	103090
Seeing	Day	17% 10% 24% 25% 18% 7%	15361
	Night	17% 10% 24% 28% 18% 3	25138

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	14% 14% 3 7% 4 4 3 3 4 4 41%	2527
	11th to 20th	Day	19% 9% 2 8% 4 3 4 2 3 4 41%	2824
	21st to end	Day	22% 10% 2 4 2 3 3 2 4 5% 41%	3225
February	1st to 10th	Day	20% 9% 3 6% 4 3 3 2 4 5% 39%	1900
	11th to 20th	Day	20% 10% 3 5% 4 4 3 3 4 4 39%	1848
	21st to end	Day	22% 9% 3 7% 4 3 4 2 4 7% 36%	1570
March	1st to 10th	Day	20% 11% 3 8% 5% 4 4 3 4 4 32%	3120
	11th to 20th	Day	12% 7% 3 6% 5% 3 4 3 5% 6% 44%	3349
	21st to end	Day	13% 7% 3 7% 5% 5% 4 3 5% 6% 41%	4148
April	1st to 10th	Day	14% 7% 3 5% 4 5% 3 4 6% 5% 45%	2280
	11th to 20th	Day	17% 6% 2 6% 4 3 3 3 4 6% 44%	2254
	21st to end	Day	12% 7% 2 7% 4 5% 4 3 6% 8% 43%	2280
May	1st to 10th	Day	14% 6% 2 6% 5% 4 4 4 6% 9% 39%	3824
	11th to 20th	Day	15% 6% 2 7% 4 4 5% 4 6% 9% 37%	4081
	21st to end	Day	12% 6% 2 7% 5% 6% 5% 5% 7% 9% 36%	4497
June	1st to 10th	Day	9% 6% 2 7% 5% 5% 5% 4 7% 9% 40%	2660
	11th to 20th	Day	4 4 2 5% 4 5% 5% 5% 7% 10% 48%	2660
	21st to end	Day	5% 4 2 5% 5% 5% 6% 5% 7% 9% 45%	2660
July	1st to 10th	Day	6% 5% 2 7% 6% 5% 7% 6% 8% 11% 37%	4440
	11th to 20th	Day	9% 5% 2 6% 5% 6% 6% 6% 9% 12% 34%	4440
	21st to end	Day	15% 9% 3 8% 6% 5% 6% 4 7% 8% 29%	4328
August	1st to 10th	Day	3 3 2 4 4 4 5% 4 7% 8% 58%	3785
	11th to 20th	Day	7% 4 2 6% 4 5% 5% 5% 6% 9% 46%	3729
	21st to end	Day	6% 4 2 5% 5% 4 5% 3 6% 8% 52%	4180
September	1st to 10th	Day	9% 5% 2 6% 5% 5% 5% 4 7% 7% 45%	2280
	11th to 20th	Day	13% 5% 2 5% 4 4 4 4 6% 8% 44%	2167
	21st to end	Day	12% 5% 2 5% 4 4 4 3 5% 7% 51%	2090
October	1st to 10th	Day	8% 5% 1 4 4 4 3 3 4 5% 58%	2071
	11th to 20th	Day	10% 4 1 5% 3 3 3 4 4 5% 58%	1900
	21st to end	Day	17% 5% 2 4 3 3 3 3 4 3 52%	2062
November	1st to 10th	Day	13% 5% 2 4 3 3 3 2 4 5% 55%	1762
	11th to 20th	Day	12% 6% 3 5% 3 2 3 3 5% 7% 52%	1800
	21st to end	Day	18% 8% 2 4 3 4 3 4 5% 6% 44%	1800
December	1st to 10th	Day	19% 8% 3 7% 5% 4 3 3 4 5% 40%	1782
	11th to 20th	Day	16% 8% 3 6% 4 4 3 4 4 5% 43%	2013
	21st to end	Day	13% 12% 4 8% 4 4 4 3 6% 6% 35%	2783
January	1st to 10th	Night	19% 10% 3 6% 4 3 4 2 4 5% 41%	4428
	11th to 20th	Night	18% 8% 3 8% 3 3 3 3 3 4 44%	4143
	21st to end	Night	25% 10% 2 4 3 2 2 2 3 4 43%	4436
February	1st to 10th	Night	19% 10% 3 7% 4 3 3 2 3 5% 38%	2280
	11th to 20th	Night	19% 9% 3 6% 4 4 3 2 4 4 42%	2218
	21st to end	Night	20% 8% 3 6% 5% 3 4 4 4 5% 39%	1884
March	1st to 10th	Night	20% 10% 3 7% 3 3 4 2 4 5% 39%	3733
	11th to 20th	Night	14% 7% 1 4 3 3 3 3 5% 6% 48%	3626
	21st to end	Night	15% 7% 2 7% 5% 4 4 4 5% 6% 42%	3481
April	1st to 10th	Night	13% 6% 2 6% 4 4 3 3 6% 7% 46%	1900
	11th to 20th	Night	14% 6% 2 6% 3 3 3 3 4 7% 49%	1875
	21st to end	Night	11% 6% 2 5% 4 4 4 4 6% 6% 47%	1900
May	1st to 10th	Night	17% 7% 3 6% 4 3 3 3 5% 7% 41%	3070
	11th to 20th	Night	13% 7% 2 6% 4 4 4 3 5% 7% 45%	2812
	21st to end	Night	9% 5% 2 6% 5% 5% 5% 4 8% 10% 42%	3054
June	1st to 10th	Night	9% 6% 2 5% 4 5% 4 5% 7% 11% 43%	1520
	11th to 20th	Night	3 3 1 3 4 4 4 5% 7% 10% 57%	1520
	21st to end	Night	3 4 2 3 4 4 4 4 6% 10% 56%	1520
July	1st to 10th	Night	5% 4 2 7% 5% 5% 5% 5% 7% 13% 43%	2530
	11th to 20th	Night	5% 4 2 5% 3 4 4 5% 7% 14% 49%	2530
	21st to end	Night	11% 8% 4 8% 5% 5% 5% 4 6% 8% 37%	3225
August	1st to 10th	Night	2 2 1 3 3 3 3 3 6% 7% 67%	3144
	11th to 20th	Night	4 3 1 4 4 4 4 4 8% 12% 54%	3100
	21st to end	Night	4 3 1 4 3 4 4 4 8% 9% 55%	3476
September	1st to 10th	Night	7% 5% 3 6% 4 4 4 4 6% 6% 52%	1900
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 5% 7% 50%	1992
	21st to end	Night	9% 5% 2 4 3 3 3 3 5% 7% 57%	2090
October	1st to 10th	Night	9% 3 1 4 3 2 3 3 4 6% 62%	2104
	11th to 20th	Night	10% 6% 2 4 3 3 4 2 4 5% 57%	2280
	21st to end	Night	16% 7% 2 4 3 3 3 3 3 5% 53%	2534
November	1st to 10th	Night	12% 5% 2 5% 4 3 3 3 5% 5% 54%	2536
	11th to 20th	Night	11% 5% 2 4 3 3 4 3 5% 7% 52%	2600
	21st to end	Night	16% 7% 2 4 3 4 4 3 4 5% 50%	2600
December	1st to 10th	Night	19% 8% 2 6% 4 3 3 3 5% 6% 42%	2581
	11th to 20th	Night	16% 7% 3 6% 3 3 3 2 4 5% 48%	3176
	21st to end	Night	15% 9% 3 7% 5% 5% 5% 4 6% 7% 34%	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	47% 4 5% 20% 21% 3	2528
	11th to 20th	Day	46% 5% 6% 20% 20% 1	2824
	21st to end	Day	46% 3 9% 20% 21% 2	3225
February	1st to 10th	Day	49% 3 6% 21% 18% 3	1900
	11th to 20th	Day	49% 4 5% 19% 17% 5%	1858
	21st to end	Day	50% 3 9% 14% 16% 7%	1570
March	1st to 10th	Day	55% 4 7% 12% 14% 9%	3120
	11th to 20th	Day	40% 5% 9% 23% 17% 6%	3349
	21st to end	Day	43% 6% 9% 22% 20% 1	4148
April	1st to 10th	Day	39% 6% 8% 23% 20% 4	2280
	11th to 20th	Day	41% 4 9% 19% 21% 6%	2254
	21st to end	Day	38% 6% 10% 25% 19% 2	2280
May	1st to 10th	Day	39% 8% 10% 24% 16% 1	3859
	11th to 20th	Day	40% 8% 16% 21% 13% 1	4085
	21st to end	Day	40% 8% 13% 25% 13% 1	4510
June	1st to 10th	Day	37% 9% 13% 22% 18% 2	2660
	11th to 20th	Day	28% 8% 16% 27% 18% 3	2660
	21st to end	Day	30% 9% 15% 23% 18% 4	2660
July	1st to 10th	Day	36% 8% 19% 27% 8% 2	4371
	11th to 20th	Day	38% 8% 16% 30% 6% 2	4365
	21st to end	Day	52% 8% 11% 23% 7%	4190
August	1st to 10th	Day	22% 7% 17% 30% 22% 2	3773
	11th to 20th	Day	32% 7% 16% 26% 17% 2	3765
	21st to end	Day	29% 5% 11% 25% 26% 3	4179
September	1st to 10th	Day	35% 8% 11% 24% 16% 5%	2280
	11th to 20th	Day	38% 6% 11% 18% 22% 5%	2167
	21st to end	Day	32% 5% 10% 24% 22% 7%	2090
October	1st to 10th	Day	18% 3 6% 15% 38% 20%	3448
	11th to 20th	Day	19% 3 5% 21% 37% 16%	3140
	21st to end	Day	26% 3 4 26% 32% 8%	3376
November	1st to 10th	Day	32% 4 7% 22% 27% 7%	1762
	11th to 20th	Day	34% 3 9% 19% 26% 9%	1800
	21st to end	Day	41% 3 8% 20% 24% 4	1800
December	1st to 10th	Day	49% 4 5% 20% 17% 4	1782
	11th to 20th	Day	45% 4 6% 21% 21% 3	2010
	21st to end	Day	47% 6% 11% 21% 14% 2	2783
January	1st to 10th	Night	47% 4 6% 19% 22% 3	4428
	11th to 20th	Night	45% 5% 5% 21% 19% 5%	4143
	21st to end	Night	47% 3 6% 22% 19% 3	4436
February	1st to 10th	Night	49% 4 8% 17% 19% 3	2280
	11th to 20th	Night	47% 3 7% 19% 18% 6%	2219
	21st to end	Night	47% 4 8% 16% 18% 6%	1884
March	1st to 10th	Night	48% 4 9% 13% 16% 9%	3733
	11th to 20th	Night	36% 6% 9% 22% 19% 9%	3626
	21st to end	Night	43% 6% 9% 18% 23% 2	3481
April	1st to 10th	Night	37% 5% 10% 23% 20% 5%	1900
	11th to 20th	Night	36% 4 8% 20% 23% 8%	1875
	21st to end	Night	36% 6% 10% 26% 20% 3	1900
May	1st to 10th	Night	42% 8% 10% 22% 16% 2	3100
	11th to 20th	Night	38% 7% 15% 25% 13% 1	2813
	21st to end	Night	34% 10% 14% 27% 14% 2	3062
June	1st to 10th	Night	33% 9% 14% 22% 20% 2	1520
	11th to 20th	Night	20% 8% 15% 30% 23% 3	1520
	21st to end	Night	23% 7% 16% 29% 20% 5%	1520
July	1st to 10th	Night	31% 9% 22% 28% 9% 2	2490
	11th to 20th	Night	25% 7% 19% 37% 9% 3	2482
	21st to end	Night	44% 8% 14% 22% 10% 1	3123
August	1st to 10th	Night	15% 6% 12% 40% 25% 2	3132
	11th to 20th	Night	23% 7% 23% 27% 19% 2	3130
	21st to end	Night	23% 6% 15% 24% 27% 5%	3476
September	1st to 10th	Night	31% 7% 10% 25% 21% 7%	1900
	11th to 20th	Night	33% 7% 12% 18% 27% 4	1992
	21st to end	Night	27% 5% 9% 27% 24% 8%	2090
October	1st to 10th	Night	17% 3 6% 16% 37% 21%	3507
	11th to 20th	Night	19% 3 4 15% 36% 23%	3779
	21st to end	Night	25% 3 6% 28% 24% 14%	4170
November	1st to 10th	Night	32% 4 5% 24% 27% 8%	2536
	11th to 20th	Night	31% 5% 7% 21% 26% 10%	2600
	21st to end	Night	38% 4 7% 21% 24% 6%	2600
December	1st to 10th	Night	44% 4 8% 21% 19% 4	2581
	11th to 20th	Night	39% 3 7% 22% 24% 4	3178
	21st to end	Night	45% 7% 11% 20% 13% 4	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	26% 24% 35% 11% 3	270
	11th to 20th	Day	33% 20% 34% 9% 3 1	270
	21st to end	Day	26% 26% 33% 12% 3	297
February	1st to 10th	Day	30% 21% 33% 12% 4 1	270
	11th to 20th	Day	40% 22% 29% 7% 2 1	270
	21st to end	Day	36% 28% 28% 6% 2	225
March	1st to 10th	Day	30% 21% 32% 12% 4	270
	11th to 20th	Day	30% 20% 35% 13% 1	270
	21st to end	Day	28% 18% 35% 13% 6%	489
April	1st to 10th	Day	26% 16% 29% 22% 7%	460
	11th to 20th	Day	25% 15% 32% 19% 7% 2	452
	21st to end	Day	21% 16% 30% 22% 10% 2	460
May	1st to 10th	Day	19% 16% 30% 22% 10% 3	463
	11th to 20th	Day	16% 7% 29% 27% 15% 5%	487
	21st to end	Day	11% 6% 27% 30% 18% 9%	537
June	1st to 10th	Day	11% 5% 21% 30% 23% 10%	680
	11th to 20th	Day	6% 3 18% 34% 27% 12%	680
	21st to end	Day	6% 4 21% 35% 23% 10%	680
July	1st to 10th	Day	8% 2 14% 30% 32% 13%	671
	11th to 20th	Day	9% 2 13% 28% 33% 16%	668
	21st to end	Day	7% 3 13% 32% 30% 15%	656
August	1st to 10th	Day	6% 3 14% 29% 35% 14%	486
	11th to 20th	Day	12% 3 13% 32% 30% 10%	479
	21st to end	Day	12% 2 9% 26% 33% 17%	539
September	1st to 10th	Day	9% 2 14% 34% 30% 10%	490
	11th to 20th	Day	13% 2 13% 28% 30% 14%	490
	21st to end	Day	16% 5% 15% 32% 22% 10%	490
October	1st to 10th	Day	8% 6% 22% 32% 26% 7%	471
	11th to 20th	Day	10% 13% 40% 27% 9% 2	300
	21st to end	Day	25% 12% 32% 22% 8% 2	330
November	1st to 10th	Day	21% 11% 28% 28% 10% 2	300
	11th to 20th	Day	13% 20% 36% 25% 4 1	300
	21st to end	Day	26% 16% 27% 18% 12% 2	300
December	1st to 10th	Day	31% 17% 30% 17% 4 1	294
	11th to 20th	Day	27% 20% 27% 19% 6% 1	270
	21st to end	Day	29% 17% 37% 14% 2	297
January	1st to 10th	Night	25% 19% 31% 21% 4	950
	11th to 20th	Night	26% 21% 30% 19% 5%	950
	21st to end	Night	24% 16% 36% 22% 2	988
February	1st to 10th	Night	28% 15% 33% 21% 4	760
	11th to 20th	Night	28% 17% 31% 22% 2	743
	21st to end	Night	28% 19% 32% 18% 2	628
March	1st to 10th	Night	22% 16% 30% 28% 4	760
	11th to 20th	Night	24% 13% 35% 23% 4 1	664
	21st to end	Night	20% 15% 30% 25% 10%	627
April	1st to 10th	Night	17% 14% 35% 25% 9%	570
	11th to 20th	Night	20% 9% 34% 26% 9% 1	563
	21st to end	Night	15% 11% 36% 27% 11% 1	570
May	1st to 10th	Night	15% 9% 28% 32% 14% 2	570
	11th to 20th	Night	13% 6% 28% 33% 17% 4	561
	21st to end	Night	7% 4 22% 37% 25% 6%	617
June	1st to 10th	Night	11% 2 15% 34% 30% 6%	570
	11th to 20th	Night	4 2 17% 35% 38% 5%	570
	21st to end	Night	5% 1 13% 38% 35% 8%	570
July	1st to 10th	Night	5% 2 11% 30% 41% 11%	555
	11th to 20th	Night	6% 2 11% 26% 41% 14%	552
	21st to end	Night	6% 1 10% 29% 43% 12%	624
August	1st to 10th	Night	5% 1 7% 29% 48% 10%	567
	11th to 20th	Night	7% 2 9% 38% 38% 7%	564
	21st to end	Night	8% 2 9% 29% 42% 11%	627
September	1st to 10th	Night	8% 2 11% 35% 39% 5%	570
	11th to 20th	Night	11% 3 14% 31% 34% 7%	662
	21st to end	Night	12% 4 15% 32% 32% 4	760
October	1st to 10th	Night	9% 4 19% 32% 32% 4	760
	11th to 20th	Night	14% 9% 25% 33% 18% 2	760
	21st to end	Night	19% 9% 24% 31% 15% 1	836
November	1st to 10th	Night	14% 8% 26% 33% 17% 2	780
	11th to 20th	Night	16% 9% 33% 31% 10% 1	800
	21st to end	Night	23% 10% 28% 27% 11% 1	800
December	1st to 10th	Night	24% 13% 30% 27% 6%	795
	11th to 20th	Night	22% 16% 27% 29% 7%	850
	21st to end	Night	27% 15% 30% 24% 4	1045

Page generated at 2024-12-06 02:54:52. Version ac07

Copyright © 2024 Attilla Danko.