Silver Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Silver Creek Observatory clear sky chart from 2005-11-06 to 2026-10-14.

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% 6% 2 6% 4 5% 5% 4 6% 8% 41%	149178
	Night	13% 6% 2 6% 4 4 4 4 6% 7% 43%	142558
Transparency	Day	38% 7% 13% 21% 17% 5%	152850
	Night	38% 7% 12% 20% 18% 6%	146958
Seeing	Day	17% 9% 21% 25% 18% 9%	17763
	Night	16% 7% 21% 32% 20% 4	27780

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% 6% 2 5% 3 2 3 2 4 5% 54%	5258
	11th to 20th	Day	9% 6% 1 4 3 3 3 3 3 4 62%	5280
	21st to end	Day	18% 7% 2 6% 3 4 3 3 4 6% 44%	5780
February	1st to 10th	Day	14% 7% 2 6% 4 4 3 4 7% 8% 43%	1911
	11th to 20th	Day	19% 7% 2 5% 3 2 4 4 5% 6% 43%	2048
	21st to end	Day	17% 7% 2 5% 4 4 4 3 5% 5% 43%	1730
March	1st to 10th	Day	18% 6% 2 6% 4 3 4 3 5% 5% 43%	5040
	11th to 20th	Day	10% 5% 2 6% 4 3 3 3 4 7% 54%	5090
	21st to end	Day	15% 6% 2 5% 4 4 3 3 4 6% 46%	5586
April	1st to 10th	Day	11% 4 2 5% 3 4 5% 4 6% 8% 48%	2310
	11th to 20th	Day	14% 4 2 4 4 3 4 4 5% 7% 48%	2493
	21st to end	Day	13% 5% 2 5% 4 4 5% 3 5% 7% 46%	2730
May	1st to 10th	Day	10% 7% 3 8% 4 5% 6% 4 7% 9% 37%	7616
	11th to 20th	Day	15% 7% 2 7% 4 5% 5% 4 6% 8% 38%	7626
	21st to end	Day	15% 7% 3 7% 5% 5% 6% 4 7% 9% 33%	8391
June	1st to 10th	Day	10% 6% 3 6% 5% 5% 7% 5% 7% 10% 36%	2730
	11th to 20th	Day	7% 4 2 6% 6% 5% 7% 6% 9% 11% 37%	2730
	21st to end	Day	6% 5% 2 6% 5% 6% 6% 7% 8% 11% 39%	2730
July	1st to 10th	Day	5% 4 2 7% 6% 6% 7% 6% 8% 12% 38%	7680
	11th to 20th	Day	9% 6% 2 9% 7% 7% 7% 6% 9% 11% 29%	7680
	21st to end	Day	11% 7% 3 9% 6% 7% 8% 6% 8% 11% 25%	8340
August	1st to 10th	Day	14% 9% 3 8% 6% 7% 7% 6% 9% 11% 19%	6014
	11th to 20th	Day	7% 4 2 6% 5% 6% 6% 5% 9% 13% 38%	5951
	21st to end	Day	6% 4 2 6% 4 5% 5% 4 7% 10% 47%	6201
September	1st to 10th	Day	10% 5% 2 6% 5% 5% 5% 4 6% 8% 44%	2310
	11th to 20th	Day	15% 7% 2 6% 4 5% 4 4 6% 7% 40%	2310
	21st to end	Day	19% 5% 2 6% 3 5% 4 3 5% 8% 39%	2310
October	1st to 10th	Day	15% 5% 2 5% 3 3 2 3 4 6% 53%	2223
	11th to 20th	Day	12% 4 2 4 3 3 2 2 4 5% 59%	2030
	21st to end	Day	15% 4 2 4 3 3 2 2 4 4 57%	2200
November	1st to 10th	Day	12% 6% 1 4 2 3 3 2 5% 5% 56%	2022
	11th to 20th	Day	12% 5% 1 4 3 3 3 3 4 7% 54%	1890
	21st to end	Day	14% 4 1 4 3 3 4 3 5% 7% 52%	1890
December	1st to 10th	Day	12% 7% 2 4 3 4 4 3 5% 4 51%	3020
	11th to 20th	Day	16% 6% 2 5% 3 3 4 4 5% 7% 45%	3463
	21st to end	Day	19% 6% 2 4 3 3 3 2 4 7% 45%	4565
January	1st to 10th	Night	13% 6% 2 4 3 2 3 2 4 6% 55%	7635
	11th to 20th	Night	10% 6% 2 5% 3 3 3 2 4 5% 58%	7680
	21st to end	Night	16% 6% 2 5% 3 3 4 4 5% 6% 46%	8401
February	1st to 10th	Night	13% 6% 2 5% 4 4 4 4 6% 7% 45%	2704
	11th to 20th	Night	18% 7% 2 5% 3 4 4 3 5% 5% 44%	2458
	21st to end	Night	15% 7% 2 6% 4 5% 4 4 5% 7% 41%	2076
March	1st to 10th	Night	17% 7% 2 6% 4 3 4 3 5% 6% 42%	5032
	11th to 20th	Night	8% 4 2 4 3 3 4 3 5% 8% 55%	5090
	21st to end	Night	14% 4 2 6% 4 4 5% 4 5% 7% 45%	5588
April	1st to 10th	Night	10% 6% 2 5% 3 4 5% 4 5% 7% 48%	2310
	11th to 20th	Night	12% 5% 2 5% 4 4 3 3 6% 8% 49%	2092
	21st to end	Night	12% 6% 2 6% 4 3 4 3 5% 6% 49%	1890
May	1st to 10th	Night	12% 6% 3 6% 5% 5% 5% 4 7% 10% 37%	5237
	11th to 20th	Night	15% 7% 3 7% 5% 4 4 3 6% 8% 37%	5234
	21st to end	Night	18% 8% 3 8% 5% 4 4 3 5% 9% 33%	5761
June	1st to 10th	Night	8% 6% 2 7% 4 6% 6% 6% 9% 10% 36%	1890
	11th to 20th	Night	9% 6% 3 7% 6% 5% 5% 5% 6% 9% 40%	1890
	21st to end	Night	6% 4 2 7% 5% 5% 6% 6% 8% 11% 40%	1890
July	1st to 10th	Night	5% 6% 3 8% 6% 6% 7% 6% 9% 11% 33%	5278
	11th to 20th	Night	11% 6% 3 8% 6% 7% 7% 5% 9% 10% 28%	5277
	21st to end	Night	11% 9% 4 10% 6% 6% 6% 5% 7% 10% 25%	5736
August	1st to 10th	Night	15% 10% 3 10% 6% 6% 6% 6% 8% 9% 21%	4135
	11th to 20th	Night	8% 6% 3 8% 6% 5% 6% 5% 8% 11% 34%	4095
	21st to end	Night	7% 6% 3 8% 5% 5% 5% 5% 7% 9% 41%	4859
September	1st to 10th	Night	10% 6% 2 6% 5% 5% 5% 4 6% 7% 44%	2310
	11th to 20th	Night	16% 7% 2 7% 5% 5% 5% 4 5% 7% 37%	2310
	21st to end	Night	19% 7% 2 6% 4 4 4 2 5% 6% 40%	2310
October	1st to 10th	Night	16% 4 2 5% 4 3 4 3 5% 5% 48%	2395
	11th to 20th	Night	13% 5% 2 5% 3 3 4 3 4 5% 53%	2437
	21st to end	Night	14% 4 2 4 3 3 3 3 4 4 57%	2640
November	1st to 10th	Night	13% 5% 2 6% 3 3 4 3 3 4 54%	2493
	11th to 20th	Night	13% 5% 2 4 3 3 3 3 4 7% 54%	2730
	21st to end	Night	13% 5% 2 5% 2 3 4 3 6% 6% 51%	2730
December	1st to 10th	Night	13% 7% 2 5% 3 3 3 3 5% 5% 51%	4380
	11th to 20th	Night	17% 9% 2 7% 3 4 4 3 4 5% 42%	4952
	21st to end	Night	19% 5% 2 5% 3 3 4 3 4 6% 46%	6633

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	34% 3 9% 20% 29% 5%	5259
	11th to 20th	Day	26% 3 5% 14% 37% 15%	5280
	21st to end	Day	42% 4 5% 20% 22% 8%	5780
February	1st to 10th	Day	38% 5% 11% 22% 19% 5%	1911
	11th to 20th	Day	41% 5% 9% 20% 19% 6%	2058
	21st to end	Day	43% 5% 9% 16% 19% 8%	1730
March	1st to 10th	Day	41% 4 7% 16% 19% 12%	5040
	11th to 20th	Day	31% 4 7% 17% 23% 19%	5090
	21st to end	Day	38% 4 8% 25% 19% 5%	5586
April	1st to 10th	Day	32% 5% 12% 23% 22% 5%	2310
	11th to 20th	Day	34% 5% 10% 22% 22% 7%	2493
	21st to end	Day	36% 6% 12% 26% 16% 3	2730
May	1st to 10th	Day	42% 7% 14% 22% 13% 1	7651
	11th to 20th	Day	43% 7% 13% 22% 12% 2	7630
	21st to end	Day	46% 8% 14% 17% 13% 2	8405
June	1st to 10th	Day	40% 10% 17% 22% 10% 1	2730
	11th to 20th	Day	35% 11% 19% 21% 13% 2	2730
	21st to end	Day	35% 12% 17% 20% 15% 1	2730
July	1st to 10th	Day	35% 11% 21% 23% 9% 1	7615
	11th to 20th	Day	44% 11% 22% 16% 5% 1	7611
	21st to end	Day	49% 10% 16% 17% 8% 1	8156
August	1st to 10th	Day	52% 12% 19% 13% 3	6001
	11th to 20th	Day	33% 10% 27% 21% 8% 1	5990
	21st to end	Day	31% 7% 15% 34% 11% 1	6201
September	1st to 10th	Day	37% 8% 14% 22% 16% 3	2310
	11th to 20th	Day	42% 7% 11% 20% 16% 3	2310
	21st to end	Day	44% 7% 10% 18% 16% 5%	2310
October	1st to 10th	Day	28% 5% 7% 20% 31% 9%	3548
	11th to 20th	Day	21% 3 5% 21% 27% 23%	3270
	21st to end	Day	27% 3 7% 25% 23% 15%	3538
November	1st to 10th	Day	30% 3 9% 21% 28% 7%	2022
	11th to 20th	Day	30% 4 8% 24% 26% 8%	1890
	21st to end	Day	32% 4 9% 24% 26% 5%	1890
December	1st to 10th	Day	35% 4 7% 19% 28% 8%	3020
	11th to 20th	Day	37% 6% 10% 18% 22% 7%	3460
	21st to end	Day	38% 5% 10% 28% 16% 3	4565
January	1st to 10th	Night	31% 5% 10% 22% 25% 6%	7636
	11th to 20th	Night	29% 3 5% 17% 35% 10%	7680
	21st to end	Night	38% 5% 6% 20% 21% 9%	8401
February	1st to 10th	Night	37% 5% 11% 22% 20% 5%	2704
	11th to 20th	Night	43% 3 8% 19% 21% 6%	2459
	21st to end	Night	41% 6% 10% 17% 21% 6%	2076
March	1st to 10th	Night	38% 7% 8% 15% 24% 8%	5032
	11th to 20th	Night	27% 5% 7% 19% 25% 18%	5090
	21st to end	Night	38% 5% 8% 26% 17% 6%	5588
April	1st to 10th	Night	33% 6% 13% 21% 22% 5%	2310
	11th to 20th	Night	32% 6% 9% 24% 22% 7%	2092
	21st to end	Night	35% 5% 13% 24% 18% 3	1890
May	1st to 10th	Night	41% 7% 15% 24% 12% 2	5264
	11th to 20th	Night	44% 8% 13% 24% 11% 1	5235
	21st to end	Night	47% 8% 12% 21% 11% 1	5771
June	1st to 10th	Night	38% 12% 17% 20% 11% 1	1890
	11th to 20th	Night	38% 10% 20% 23% 9% 1	1890
	21st to end	Night	33% 12% 18% 20% 14% 3	1890
July	1st to 10th	Night	38% 13% 21% 21% 6% 1	5235
	11th to 20th	Night	46% 13% 24% 13% 3 1	5226
	21st to end	Night	51% 10% 17% 14% 7% 1	5606
August	1st to 10th	Night	54% 14% 17% 12% 3	4124
	11th to 20th	Night	38% 11% 26% 18% 7%	4122
	21st to end	Night	37% 9% 15% 29% 8% 1	4859
September	1st to 10th	Night	38% 9% 14% 21% 15% 3	2310
	11th to 20th	Night	45% 9% 12% 18% 15% 1	2310
	21st to end	Night	45% 6% 11% 16% 18% 3	2310
October	1st to 10th	Night	35% 6% 8% 18% 26% 8%	3850
	11th to 20th	Night	22% 4 6% 23% 27% 18%	3936
	21st to end	Night	28% 3 6% 23% 27% 13%	4252
November	1st to 10th	Night	34% 4 8% 20% 25% 9%	2493
	11th to 20th	Night	32% 3 8% 21% 26% 10%	2730
	21st to end	Night	32% 5% 8% 24% 26% 6%	2730
December	1st to 10th	Night	34% 4 8% 21% 26% 6%	4380
	11th to 20th	Night	45% 4 7% 17% 20% 7%	4954
	21st to end	Night	38% 5% 14% 24% 18% 2	6633

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% 17% 33% 21% 3	330
	11th to 20th	Day	24% 22% 33% 18% 3	330
	21st to end	Day	21% 21% 36% 18% 3	363
February	1st to 10th	Day	19% 17% 38% 19% 6%	330
	11th to 20th	Day	35% 21% 28% 13% 2	330
	21st to end	Day	30% 22% 34% 10% 4	273
March	1st to 10th	Day	20% 17% 28% 25% 8% 1	535
	11th to 20th	Day	23% 18% 30% 25% 4 1	540
	21st to end	Day	22% 15% 34% 22% 7%	594
April	1st to 10th	Day	20% 14% 30% 21% 12% 2	540
	11th to 20th	Day	17% 15% 28% 24% 14% 3	532
	21st to end	Day	15% 10% 27% 26% 15% 6%	540
May	1st to 10th	Day	14% 15% 27% 27% 13% 5%	543
	11th to 20th	Day	19% 8% 18% 28% 19% 8%	567
	21st to end	Day	19% 6% 17% 26% 21% 12%	617
June	1st to 10th	Day	10% 6% 15% 34% 23% 11%	570
	11th to 20th	Day	8% 4 18% 28% 24% 17%	570
	21st to end	Day	8% 2 14% 34% 27% 15%	570
July	1st to 10th	Day	7% 3 10% 23% 32% 25%	565
	11th to 20th	Day	8% 3 9% 26% 29% 25%	564
	21st to end	Day	9% 3 10% 27% 28% 23%	620
August	1st to 10th	Day	18% 4 14% 23% 22% 19%	566
	11th to 20th	Day	12% 4 11% 24% 31% 19%	559
	21st to end	Day	11% 3 10% 22% 30% 24%	627
September	1st to 10th	Day	12% 3 10% 26% 31% 19%	570
	11th to 20th	Day	18% 4 12% 20% 29% 17%	570
	21st to end	Day	23% 4 17% 24% 24% 8%	570
October	1st to 10th	Day	19% 3 13% 29% 26% 10%	570
	11th to 20th	Day	14% 9% 19% 32% 20% 6%	542
	21st to end	Day	18% 8% 20% 32% 18% 4	583
November	1st to 10th	Day	21% 6% 22% 31% 15% 5%	500
	11th to 20th	Day	16% 15% 35% 24% 8% 2	330
	21st to end	Day	15% 14% 33% 26% 10% 2	330
December	1st to 10th	Day	25% 16% 32% 21% 5%	330
	11th to 20th	Day	20% 14% 29% 27% 9% 1	330
	21st to end	Day	25% 13% 33% 21% 7% 2	363
January	1st to 10th	Night	19% 12% 31% 31% 6%	840
	11th to 20th	Night	18% 11% 34% 32% 5%	840
	21st to end	Night	16% 11% 37% 33% 4	924
February	1st to 10th	Night	16% 9% 34% 37% 4	840
	11th to 20th	Night	23% 13% 35% 27% 2	823
	21st to end	Night	18% 15% 33% 29% 4	692
March	1st to 10th	Night	17% 9% 31% 38% 5%	840
	11th to 20th	Night	17% 12% 31% 32% 8% 1	840
	21st to end	Night	18% 9% 35% 31% 8%	924
April	1st to 10th	Night	15% 10% 31% 33% 10%	840
	11th to 20th	Night	15% 12% 26% 33% 13% 1	801
	21st to end	Night	15% 5% 22% 40% 17%	630
May	1st to 10th	Night	14% 5% 24% 39% 17%	630
	11th to 20th	Night	16% 5% 17% 35% 24% 2	621
	21st to end	Night	17% 3 11% 31% 32% 6%	683
June	1st to 10th	Night	10% 3 12% 35% 36% 5%	630
	11th to 20th	Night	11% 3 10% 32% 35% 9%	630
	21st to end	Night	7% 1 6% 34% 44% 8%	630
July	1st to 10th	Night	10% 3 6% 22% 50% 9%	615
	11th to 20th	Night	12% 1 4 22% 47% 14%	612
	21st to end	Night	8% 2 4 27% 45% 12%	690
August	1st to 10th	Night	18% 3 4 25% 42% 8%	627
	11th to 20th	Night	13% 3 5% 27% 41% 12%	624
	21st to end	Night	11% 3 9% 24% 43% 11%	797
September	1st to 10th	Night	12% 2 8% 27% 40% 10%	840
	11th to 20th	Night	19% 3 7% 24% 40% 7%	840
	21st to end	Night	22% 3 12% 31% 28% 3	840
October	1st to 10th	Night	18% 4 13% 29% 29% 7%	840
	11th to 20th	Night	17% 5% 21% 35% 20% 2	813
	21st to end	Night	16% 6% 19% 39% 17% 3	880
November	1st to 10th	Night	15% 6% 19% 40% 17% 3	820
	11th to 20th	Night	15% 7% 25% 40% 12% 1	840
	21st to end	Night	15% 8% 25% 36% 15% 1	840
December	1st to 10th	Night	21% 9% 26% 36% 8%	840
	11th to 20th	Night	18% 7% 29% 36% 8% 1	840
	21st to end	Night	24% 10% 24% 35% 7%	924

Page generated at 2026-10-11 05:06:29. Version ac07

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