Tucker Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tucker Creek Observatory clear sky chart from 2005-11-06 to 2025-01-22.

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% 44%	104885
	Night	13% 7% 2 6% 4 4 4 3 5% 7% 45%	104576
Transparency	Day	38% 5% 11% 25% 18% 3	108519
	Night	37% 5% 11% 24% 19% 4	109083
Seeing	Day	16% 11% 28% 25% 15% 5%	15775
	Night	17% 11% 29% 27% 14% 2	25691

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	13% 11% 4 8% 5% 4 3 3 4 6% 39%	2607
	11th to 20th	Day	14% 9% 3 6% 4 3 4 3 5% 5% 46%	2878
	21st to end	Day	23% 10% 3 7% 3 3 4 3 3 4 36%	3144
February	1st to 10th	Day	16% 12% 3 7% 5% 3 3 3 4 5% 38%	1740
	11th to 20th	Day	15% 9% 3 7% 5% 3 3 3 6% 6% 40%	1848
	21st to end	Day	14% 11% 3 7% 4 3 4 4 6% 6% 37%	1570
March	1st to 10th	Day	19% 12% 3 6% 3 4 4 3 3 4 39%	3147
	11th to 20th	Day	13% 7% 2 5% 4 3 3 3 4 5% 51%	3480
	21st to end	Day	14% 9% 3 6% 4 4 5% 3 5% 6% 40%	4034
April	1st to 10th	Day	11% 8% 3 5% 4 4 4 4 6% 7% 46%	2280
	11th to 20th	Day	15% 9% 2 7% 4 4 4 3 4 7% 41%	2254
	21st to end	Day	17% 8% 3 6% 5% 4 5% 3 5% 6% 38%	2280
May	1st to 10th	Day	13% 7% 2 8% 6% 5% 5% 5% 7% 8% 34%	3819
	11th to 20th	Day	18% 8% 2 6% 4 4 4 3 5% 8% 37%	4227
	21st to end	Day	11% 7% 2 7% 5% 5% 5% 4 5% 7% 42%	4824
June	1st to 10th	Day	10% 5% 2 6% 5% 4 4 4 7% 9% 45%	2660
	11th to 20th	Day	5% 5% 2 5% 5% 5% 5% 4 7% 8% 49%	2660
	21st to end	Day	4 4 2 5% 5% 5% 6% 4 8% 11% 47%	2660
July	1st to 10th	Day	10% 5% 2 6% 5% 6% 5% 4 7% 9% 42%	4440
	11th to 20th	Day	4 3 1 5% 5% 4 5% 5% 7% 11% 49%	4440
	21st to end	Day	8% 7% 3 8% 6% 6% 7% 5% 7% 8% 34%	4507
August	1st to 10th	Day	4 3 2 5% 3 4 5% 5% 6% 10% 53%	3990
	11th to 20th	Day	11% 6% 2 5% 4 4 5% 3 6% 8% 46%	3729
	21st to end	Day	6% 5% 1 5% 4 4 4 4 6% 8% 54%	4180
September	1st to 10th	Day	10% 5% 2 5% 4 3 4 4 5% 8% 49%	2280
	11th to 20th	Day	9% 6% 3 6% 4 4 4 4 5% 9% 46%	2240
	21st to end	Day	11% 5% 2 4 3 3 4 3 6% 7% 52%	2090
October	1st to 10th	Day	8% 4 2 4 3 3 3 3 5% 6% 58%	1926
	11th to 20th	Day	13% 5% 2 5% 3 3 3 3 4 6% 53%	1900
	21st to end	Day	17% 8% 2 5% 3 3 3 3 4 5% 48%	2084
November	1st to 10th	Day	11% 6% 2 5% 2 3 3 3 4 5% 55%	1762
	11th to 20th	Day	12% 8% 3 6% 4 3 3 3 5% 8% 47%	1800
	21st to end	Day	17% 10% 2 6% 4 3 3 3 4 5% 43%	1800
December	1st to 10th	Day	10% 10% 2 6% 4 3 3 3 4 6% 51%	2615
	11th to 20th	Day	14% 10% 3 7% 4 3 3 3 5% 5% 42%	3008
	21st to end	Day	22% 17% 4 8% 4 4 4 3 3 4 28%	3982
January	1st to 10th	Night	15% 9% 3 8% 4 3 4 4 5% 7% 38%	4568
	11th to 20th	Night	14% 9% 3 8% 6% 5% 5% 3 5% 5% 37%	4310
	21st to end	Night	24% 11% 3 6% 4 4 3 3 4 4 34%	4546
February	1st to 10th	Night	17% 12% 4 8% 4 3 3 3 4 6% 36%	2437
	11th to 20th	Night	14% 8% 4 7% 4 4 4 2 4 5% 43%	2218
	21st to end	Night	17% 8% 4 7% 4 3 4 4 5% 5% 40%	1884
March	1st to 10th	Night	21% 11% 2 6% 4 3 3 2 4 4 40%	3733
	11th to 20th	Night	13% 6% 2 5% 3 4 4 4 5% 6% 49%	3480
	21st to end	Night	14% 7% 2 8% 5% 4 5% 4 6% 7% 39%	3596
April	1st to 10th	Night	10% 6% 2 5% 4 4 4 4 5% 8% 49%	1900
	11th to 20th	Night	13% 7% 2 7% 4 5% 4 3 5% 6% 44%	1875
	21st to end	Night	20% 7% 3 5% 4 4 3 3 5% 6% 40%	1900
May	1st to 10th	Night	18% 7% 2 5% 4 3 4 3 5% 7% 40%	3071
	11th to 20th	Night	15% 7% 2 7% 3 4 4 3 5% 7% 43%	2669
	21st to end	Night	11% 7% 2 7% 5% 5% 5% 4 6% 8% 41%	2743
June	1st to 10th	Night	9% 5% 2 6% 5% 4 4 5% 6% 10% 45%	1520
	11th to 20th	Night	5% 3 1 3 2 3 4 4 6% 10% 57%	1520
	21st to end	Night	4 3 1 3 3 4 5% 5% 7% 10% 55%	1520
July	1st to 10th	Night	10% 4 2 5% 3 4 4 4 6% 9% 50%	2530
	11th to 20th	Night	5% 3 2 5% 3 3 4 3 6% 8% 57%	2530
	21st to end	Night	8% 8% 3 7% 5% 4 4 4 7% 9% 41%	3053
August	1st to 10th	Night	4 3 1 4 3 3 4 4 6% 9% 60%	2943
	11th to 20th	Night	8% 6% 2 6% 3 4 4 3 4 9% 50%	3100
	21st to end	Night	4 3 1 5% 3 3 4 3 6% 9% 59%	3476
September	1st to 10th	Night	10% 6% 2 5% 4 3 3 3 4 6% 54%	1900
	11th to 20th	Night	8% 6% 2 4 3 4 5% 4 5% 6% 52%	1919
	21st to end	Night	10% 5% 2 4 3 4 4 4 5% 7% 53%	2090
October	1st to 10th	Night	6% 4 1 5% 2 3 3 3 5% 5% 63%	2251
	11th to 20th	Night	12% 5% 2 4 3 3 3 2 4 5% 56%	2280
	21st to end	Night	18% 7% 2 5% 3 3 4 2 4 5% 48%	2513
November	1st to 10th	Night	11% 6% 2 4 3 2 2 2 5% 6% 57%	2536
	11th to 20th	Night	13% 6% 2 5% 4 3 3 3 4 6% 51%	2600
	21st to end	Night	17% 9% 3 5% 3 3 2 2 4 5% 47%	2600
December	1st to 10th	Night	14% 9% 2 6% 4 4 3 3 4 5% 47%	4570
	11th to 20th	Night	15% 9% 3 6% 4 4 4 3 4 6% 44%	5199
	21st to end	Night	23% 13% 4 8% 4 3 4 3 4 5% 29%	6996

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 11% 27% 11% 2	2608
	11th to 20th	Day	41% 3 9% 25% 17% 4	2878
	21st to end	Day	51% 4 9% 17% 14% 4	3144
February	1st to 10th	Day	48% 4 10% 23% 14% 2	1740
	11th to 20th	Day	44% 5% 11% 21% 14% 5%	1858
	21st to end	Day	46% 5% 10% 21% 13% 6%	1570
March	1st to 10th	Day	50% 4 6% 20% 12% 8%	3147
	11th to 20th	Day	36% 5% 8% 28% 17% 6%	3480
	21st to end	Day	43% 6% 16% 21% 14% 1	4034
April	1st to 10th	Day	37% 5% 10% 26% 20% 2	2280
	11th to 20th	Day	43% 5% 10% 22% 16% 5%	2254
	21st to end	Day	45% 6% 11% 22% 15% 1	2280
May	1st to 10th	Day	43% 10% 14% 21% 12% 1	3854
	11th to 20th	Day	44% 7% 12% 24% 12% 1	4231
	21st to end	Day	40% 7% 10% 21% 20% 1	4837
June	1st to 10th	Day	34% 7% 16% 25% 17% 2	2660
	11th to 20th	Day	29% 7% 12% 27% 22% 3	2660
	21st to end	Day	28% 8% 18% 24% 17% 5%	2660
July	1st to 10th	Day	37% 6% 13% 26% 15% 3	4371
	11th to 20th	Day	27% 5% 14% 35% 17% 2	4365
	21st to end	Day	44% 6% 14% 26% 8% 1	4365
August	1st to 10th	Day	24% 6% 14% 33% 22% 1	3976
	11th to 20th	Day	36% 5% 13% 26% 17% 3	3765
	21st to end	Day	27% 4 14% 36% 16% 3	4179
September	1st to 10th	Day	32% 6% 13% 26% 19% 5%	2280
	11th to 20th	Day	34% 6% 9% 24% 25% 2	2240
	21st to end	Day	31% 5% 8% 28% 26% 3	2090
October	1st to 10th	Day	16% 3 6% 20% 44% 11%	3199
	11th to 20th	Day	23% 3 6% 22% 38% 9%	3140
	21st to end	Day	30% 3 5% 28% 28% 5%	3410
November	1st to 10th	Day	32% 4 11% 26% 20% 7%	1762
	11th to 20th	Day	37% 4 7% 23% 21% 7%	1800
	21st to end	Day	44% 3 8% 24% 19% 2	1800
December	1st to 10th	Day	36% 3 7% 37% 16% 1	2615
	11th to 20th	Day	44% 4 8% 25% 17% 2	3005
	21st to end	Day	61% 4 10% 14% 9% 2	3982
January	1st to 10th	Night	43% 5% 10% 27% 13% 1	4568
	11th to 20th	Night	43% 7% 9% 24% 14% 2	4310
	21st to end	Night	51% 5% 10% 21% 11% 1	4546
February	1st to 10th	Night	49% 5% 8% 21% 14% 2	2437
	11th to 20th	Night	43% 4 10% 21% 18% 3	2219
	21st to end	Night	45% 5% 8% 21% 17% 5%	1884
March	1st to 10th	Night	48% 4 7% 20% 15% 6%	3733
	11th to 20th	Night	35% 7% 11% 23% 19% 5%	3480
	21st to end	Night	41% 8% 13% 28% 9% 1	3596
April	1st to 10th	Night	33% 6% 12% 26% 20% 3	1900
	11th to 20th	Night	39% 6% 11% 21% 19% 4	1875
	21st to end	Night	45% 4 9% 24% 15% 3	1900
May	1st to 10th	Night	40% 9% 17% 22% 11% 1	3101
	11th to 20th	Night	40% 8% 14% 20% 17% 1	2670
	21st to end	Night	38% 8% 12% 22% 17% 1	2751
June	1st to 10th	Night	34% 7% 13% 24% 20% 3	1520
	11th to 20th	Night	22% 7% 13% 30% 24% 5%	1520
	21st to end	Night	21% 8% 17% 29% 18% 8%	1520
July	1st to 10th	Night	32% 5% 14% 29% 16% 4	2490
	11th to 20th	Night	25% 5% 12% 36% 19% 3	2482
	21st to end	Night	37% 5% 19% 25% 12% 1	2956
August	1st to 10th	Night	20% 5% 20% 32% 22% 1	2933
	11th to 20th	Night	33% 5% 16% 25% 17% 4	3130
	21st to end	Night	22% 4 12% 40% 18% 3	3476
September	1st to 10th	Night	31% 7% 8% 29% 20% 6%	1900
	11th to 20th	Night	31% 6% 10% 26% 24% 3	1919
	21st to end	Night	30% 6% 9% 23% 28% 5%	2090
October	1st to 10th	Night	14% 3 6% 17% 45% 15%	3758
	11th to 20th	Night	23% 2 6% 19% 39% 11%	3779
	21st to end	Night	31% 2 7% 25% 28% 7%	4137
November	1st to 10th	Night	30% 4 10% 26% 24% 6%	2536
	11th to 20th	Night	35% 3 8% 23% 24% 7%	2600
	21st to end	Night	40% 3 8% 26% 21% 2	2600
December	1st to 10th	Night	40% 3 8% 29% 18% 1	4570
	11th to 20th	Night	42% 3 11% 21% 20% 2	5201
	21st to end	Night	56% 4 11% 18% 9% 1	6996

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	28% 21% 34% 15% 2 1	300
	11th to 20th	Day	26% 25% 37% 11% 1	300
	21st to end	Day	21% 26% 36% 14% 2	300
February	1st to 10th	Day	26% 20% 41% 12% 1	270
	11th to 20th	Day	27% 29% 31% 10% 1 1	270
	21st to end	Day	33% 23% 34% 8% 2	225
March	1st to 10th	Day	22% 19% 43% 14% 1	270
	11th to 20th	Day	29% 20% 36% 12% 2	270
	21st to end	Day	27% 21% 34% 15% 3	427
April	1st to 10th	Day	19% 23% 34% 18% 5% 1	460
	11th to 20th	Day	24% 19% 28% 19% 8% 1	452
	21st to end	Day	22% 15% 38% 17% 8% 1	460
May	1st to 10th	Day	19% 17% 33% 22% 7% 1	463
	11th to 20th	Day	19% 11% 29% 23% 13% 4	568
	21st to end	Day	10% 7% 35% 28% 15% 5%	734
June	1st to 10th	Day	12% 5% 24% 25% 26% 8%	680
	11th to 20th	Day	6% 3 24% 39% 22% 6%	680
	21st to end	Day	5% 4 32% 34% 18% 7%	680
July	1st to 10th	Day	10% 3 17% 30% 25% 14%	671
	11th to 20th	Day	6% 2 19% 37% 26% 9%	668
	21st to end	Day	8% 4 19% 35% 27% 8%	739
August	1st to 10th	Day	9% 2 16% 38% 26% 9%	614
	11th to 20th	Day	14% 4 20% 29% 27% 7%	479
	21st to end	Day	9% 2 14% 31% 31% 12%	539
September	1st to 10th	Day	10% 3 18% 34% 26% 9%	490
	11th to 20th	Day	10% 4 15% 31% 29% 11%	490
	21st to end	Day	15% 9% 21% 29% 18% 8%	490
October	1st to 10th	Day	12% 7% 26% 39% 11% 5%	326
	11th to 20th	Day	20% 12% 35% 24% 7% 1	300
	21st to end	Day	29% 14% 37% 16% 3	330
November	1st to 10th	Day	18% 13% 38% 22% 8% 2	300
	11th to 20th	Day	20% 20% 33% 19% 7% 1	300
	21st to end	Day	28% 17% 34% 15% 6%	300
December	1st to 10th	Day	20% 20% 36% 16% 6% 2	300
	11th to 20th	Day	30% 16% 35% 16% 3	300
	21st to end	Day	29% 20% 38% 10% 3	330
January	1st to 10th	Night	21% 21% 34% 19% 3	1000
	11th to 20th	Night	25% 24% 33% 15% 3	1000
	21st to end	Night	21% 18% 40% 20% 1	1051
February	1st to 10th	Night	24% 20% 35% 18% 2	917
	11th to 20th	Night	20% 23% 37% 18% 2	743
	21st to end	Night	24% 21% 36% 18% 1	628
March	1st to 10th	Night	23% 18% 37% 19% 3	760
	11th to 20th	Night	22% 13% 38% 23% 4	570
	21st to end	Night	23% 15% 33% 24% 5%	627
April	1st to 10th	Night	13% 19% 39% 26% 4	570
	11th to 20th	Night	19% 14% 28% 26% 12% 1	563
	21st to end	Night	23% 11% 36% 22% 8%	570
May	1st to 10th	Night	16% 10% 36% 27% 10% 1	570
	11th to 20th	Night	18% 6% 31% 28% 15% 2	561
	21st to end	Night	11% 3 26% 37% 19% 4	617
June	1st to 10th	Night	11% 4 19% 36% 28% 2	570
	11th to 20th	Night	6% 2 21% 47% 24% 1	570
	21st to end	Night	5% 3 23% 39% 28% 1	570
July	1st to 10th	Night	7% 2 13% 35% 36% 8%	555
	11th to 20th	Night	7% 2 13% 40% 32% 6%	552
	21st to end	Night	8% 2 14% 39% 33% 4	624
August	1st to 10th	Night	6% 1 14% 38% 35% 5%	567
	11th to 20th	Night	9% 2 13% 37% 35% 4	564
	21st to end	Night	7% 2 12% 34% 38% 7%	627
September	1st to 10th	Night	11% 3 16% 30% 34% 6%	570
	11th to 20th	Night	11% 2 15% 32% 35% 6%	589
	21st to end	Night	12% 6% 21% 30% 26% 5%	760
October	1st to 10th	Night	8% 6% 26% 33% 23% 4	760
	11th to 20th	Night	16% 10% 33% 26% 15% 1	760
	21st to end	Night	22% 13% 31% 26% 7%	836
November	1st to 10th	Night	14% 10% 38% 28% 10% 1	780
	11th to 20th	Night	19% 13% 32% 27% 8%	800
	21st to end	Night	24% 13% 32% 23% 7%	800
December	1st to 10th	Night	22% 16% 36% 22% 5% 1	990
	11th to 20th	Night	23% 13% 37% 23% 4	1000
	21st to end	Night	26% 16% 37% 18% 3	1100

Page generated at 2025-01-19 02:06:44. Version ac07

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