Mount Sterling
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Sterling clear sky chart from 2005-11-06 to 2024-11-25.

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	13% 9% 3 7% 5% 4 4 4 5% 7% 38%	101746
	Night	13% 9% 4 8% 5% 4 4 3 5% 6% 38%	97824
Transparency	Day	44% 6% 13% 24% 12% 1	105303
	Night	44% 6% 12% 23% 14% 1	102407
Seeing	Day	17% 12% 30% 25% 13% 4	15996
	Night	17% 10% 31% 30% 11% 1	25864

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	9% 15% 10% 16% 6% 5% 3 3 4 4 26%	2527
	11th to 20th	Day	9% 12% 5% 14% 8% 5% 5% 9% 7% 6% 20%	2530
	21st to end	Day	16% 20% 8% 11% 5% 4 3 3 4 5% 22%	3044
February	1st to 10th	Day	10% 12% 5% 9% 5% 5% 4 4 6% 7% 31%	1710
	11th to 20th	Day	12% 11% 4 8% 5% 4 5% 4 5% 7% 35%	1702
	21st to end	Day	12% 11% 3 10% 6% 5% 4 3 5% 7% 33%	1570
March	1st to 10th	Day	15% 9% 3 5% 4 3 3 3 4 6% 47%	3166
	11th to 20th	Day	10% 7% 3 9% 4 4 4 4 6% 8% 43%	3480
	21st to end	Day	23% 13% 4 9% 4 3 4 3 4 5% 26%	4004
April	1st to 10th	Day	19% 12% 4 8% 4 4 4 3 5% 6% 32%	2280
	11th to 20th	Day	18% 12% 4 7% 5% 4 4 3 4 5% 33%	2254
	21st to end	Day	21% 9% 3 7% 4 4 4 4 5% 7% 32%	2285
May	1st to 10th	Day	17% 8% 2 6% 5% 5% 5% 4 5% 7% 36%	4387
	11th to 20th	Day	14% 8% 3 6% 4 4 4 4 5% 8% 41%	4399
	21st to end	Day	17% 7% 3 6% 4 5% 4 4 6% 7% 38%	4824
June	1st to 10th	Day	12% 5% 2 7% 4 4 4 3 5% 9% 45%	2660
	11th to 20th	Day	13% 5% 2 6% 5% 4 4 4 6% 8% 42%	2660
	21st to end	Day	13% 6% 2 6% 5% 4 4 4 7% 8% 39%	2660
July	1st to 10th	Day	10% 6% 3 7% 5% 5% 6% 5% 7% 9% 37%	4440
	11th to 20th	Day	5% 3 1 5% 4 5% 5% 4 7% 9% 50%	4440
	21st to end	Day	8% 6% 2 7% 5% 5% 6% 5% 7% 9% 41%	4813
August	1st to 10th	Day	9% 6% 2 7% 5% 5% 6% 5% 7% 8% 40%	4186
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 6% 7% 45%	3955
	21st to end	Day	9% 6% 2 6% 4 4 5% 4 6% 8% 46%	4180
September	1st to 10th	Day	14% 5% 2 5% 4 4 4 3 6% 6% 46%	2280
	11th to 20th	Day	13% 6% 2 6% 3 4 4 3 5% 7% 46%	2280
	21st to end	Day	13% 7% 2 6% 4 3 4 3 5% 7% 45%	2029
October	1st to 10th	Day	14% 6% 2 6% 4 4 4 3 6% 5% 47%	1900
	11th to 20th	Day	18% 9% 3 6% 4 3 5% 4 4 6% 38%	1900
	21st to end	Day	17% 10% 3 7% 4 3 3 2 4 7% 39%	1986
November	1st to 10th	Day	13% 9% 3 8% 4 4 4 3 4 7% 42%	1762
	11th to 20th	Day	15% 13% 4 10% 5% 4 4 3 5% 6% 32%	1680
	21st to end	Day	13% 12% 5% 7% 5% 3 3 3 4 6% 39%	1552
December	1st to 10th	Day	14% 13% 5% 10% 7% 4 4 4 5% 6% 29%	1520
	11th to 20th	Day	14% 12% 6% 9% 6% 5% 4 3 5% 7% 28%	1918
	21st to end	Day	20% 20% 8% 11% 5% 4 4 3 3 4 18%	2783
January	1st to 10th	Night	9% 14% 8% 14% 6% 5% 4 3 4 5% 28%	4428
	11th to 20th	Night	11% 13% 6% 14% 6% 4 4 5% 9% 5% 21%	4440
	21st to end	Night	14% 18% 8% 11% 5% 5% 4 3 4 5% 23%	4619
February	1st to 10th	Night	8% 14% 5% 11% 5% 5% 5% 4 4 5% 32%	2470
	11th to 20th	Night	10% 10% 3 8% 6% 5% 4 3 5% 6% 40%	2365
	21st to end	Night	15% 11% 3 9% 5% 5% 5% 3 5% 5% 36%	1884
March	1st to 10th	Night	15% 9% 4 7% 3 4 3 3 5% 6% 41%	3715
	11th to 20th	Night	10% 7% 2 7% 5% 4 4 3 5% 8% 44%	3480
	21st to end	Night	26% 12% 4 9% 4 3 3 2 3 5% 28%	3626
April	1st to 10th	Night	16% 11% 3 7% 5% 4 4 3 4 5% 38%	1900
	11th to 20th	Night	19% 8% 2 6% 4 4 4 3 4 7% 38%	1875
	21st to end	Night	20% 7% 3 7% 4 4 4 4 6% 6% 36%	1893
May	1st to 10th	Night	18% 8% 3 8% 4 3 4 3 6% 7% 38%	2516
	11th to 20th	Night	13% 6% 2 6% 4 4 4 4 5% 6% 46%	2506
	21st to end	Night	12% 7% 3 5% 4 3 5% 4 5% 7% 46%	2743
June	1st to 10th	Night	10% 5% 2 6% 5% 4 4 4 6% 8% 45%	1520
	11th to 20th	Night	10% 6% 2 5% 4 3 4 4 6% 8% 47%	1520
	21st to end	Night	9% 7% 3 5% 4 3 4 4 5% 8% 49%	1520
July	1st to 10th	Night	13% 7% 2 6% 4 3 3 4 5% 9% 44%	2530
	11th to 20th	Night	4 3 1 4 4 4 5% 4 7% 10% 55%	2530
	21st to end	Night	6% 4 2 6% 5% 5% 4 4 7% 9% 49%	2750
August	1st to 10th	Night	10% 4 2 5% 5% 4 4 4 5% 7% 49%	2737
	11th to 20th	Night	10% 6% 2 5% 4 3 4 3 5% 7% 51%	2881
	21st to end	Night	10% 5% 2 5% 3 3 5% 4 6% 7% 49%	3476
September	1st to 10th	Night	10% 5% 2 5% 3 3 3 3 5% 7% 53%	1900
	11th to 20th	Night	12% 5% 2 4 3 4 4 2 5% 7% 52%	1900
	21st to end	Night	11% 5% 2 5% 4 4 3 3 5% 7% 52%	2128
October	1st to 10th	Night	12% 7% 1 4 4 3 3 3 5% 5% 52%	2280
	11th to 20th	Night	15% 7% 2 6% 4 4 4 4 5% 7% 42%	2280
	21st to end	Night	16% 10% 3 6% 4 4 4 4 6% 6% 37%	2612
November	1st to 10th	Night	14% 8% 3 6% 4 4 4 3 5% 5% 44%	2536
	11th to 20th	Night	14% 12% 5% 9% 6% 4 4 3 5% 6% 32%	2718
	21st to end	Night	16% 11% 4 8% 5% 4 3 3 4 5% 37%	2723
December	1st to 10th	Night	12% 13% 4 11% 6% 5% 5% 3 5% 7% 29%	2660
	11th to 20th	Night	13% 14% 4 12% 6% 5% 4 4 5% 6% 28%	3279
	21st to end	Night	21% 17% 5% 12% 6% 5% 4 3 4 4 19%	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	63% 5% 14% 13% 5%	2528
	11th to 20th	Day	58% 8% 12% 16% 6%	2530
	21st to end	Day	65% 5% 12% 13% 4	3044
February	1st to 10th	Day	51% 6% 14% 18% 10% 1	1710
	11th to 20th	Day	48% 6% 12% 24% 9% 2	1711
	21st to end	Day	50% 8% 11% 18% 11% 2	1570
March	1st to 10th	Day	40% 6% 12% 25% 15% 3	3166
	11th to 20th	Day	37% 7% 13% 31% 10% 1	3480
	21st to end	Day	58% 8% 12% 14% 7% 1	4004
April	1st to 10th	Day	53% 6% 11% 19% 10% 1	2280
	11th to 20th	Day	52% 6% 9% 20% 10% 2	2254
	21st to end	Day	49% 9% 11% 18% 11% 1	2285
May	1st to 10th	Day	43% 9% 11% 22% 14% 1	4428
	11th to 20th	Day	39% 8% 12% 30% 10% 1	4403
	21st to end	Day	42% 9% 11% 22% 14% 2	4837
June	1st to 10th	Day	34% 8% 14% 26% 15% 2	2660
	11th to 20th	Day	38% 8% 14% 22% 17% 1	2660
	21st to end	Day	41% 8% 13% 24% 13% 2	2660
July	1st to 10th	Day	43% 5% 17% 26% 7% 1	4371
	11th to 20th	Day	30% 5% 15% 31% 18% 1	4365
	21st to end	Day	38% 7% 14% 21% 18% 1	4662
August	1st to 10th	Day	40% 6% 14% 27% 12% 1	4171
	11th to 20th	Day	37% 5% 12% 32% 13% 1	3994
	21st to end	Day	35% 5% 14% 31% 14% 1	4179
September	1st to 10th	Day	36% 8% 13% 24% 17% 1	2280
	11th to 20th	Day	36% 7% 13% 30% 14% 1	2280
	21st to end	Day	38% 6% 11% 29% 14% 1	2029
October	1st to 10th	Day	24% 4 7% 42% 22% 1	3160
	11th to 20th	Day	38% 4 10% 27% 20% 2	3140
	21st to end	Day	43% 3 11% 29% 12% 1	3250
November	1st to 10th	Day	42% 5% 14% 23% 13% 2	1762
	11th to 20th	Day	53% 6% 11% 20% 9% 1	1680
	21st to end	Day	47% 6% 17% 22% 7%	1552
December	1st to 10th	Day	56% 7% 12% 16% 8% 1	1520
	11th to 20th	Day	53% 8% 17% 14% 8% 1	1915
	21st to end	Day	70% 6% 9% 12% 4	2783
January	1st to 10th	Night	57% 6% 12% 18% 6%	4428
	11th to 20th	Night	59% 6% 11% 15% 8%	4440
	21st to end	Night	64% 6% 9% 15% 5% 1	4619
February	1st to 10th	Night	53% 5% 12% 18% 11% 1	2470
	11th to 20th	Night	46% 6% 12% 22% 12% 1	2366
	21st to end	Night	49% 6% 11% 21% 11% 2	1884
March	1st to 10th	Night	42% 6% 12% 25% 12% 3	3715
	11th to 20th	Night	36% 7% 11% 28% 16% 2	3480
	21st to end	Night	60% 5% 8% 18% 8% 1	3626
April	1st to 10th	Night	47% 7% 10% 21% 14% 1	1900
	11th to 20th	Night	46% 6% 10% 20% 16% 3	1875
	21st to end	Night	47% 6% 12% 20% 13% 3	1893
May	1st to 10th	Night	42% 9% 11% 18% 19%	2540
	11th to 20th	Night	36% 9% 11% 24% 18% 3	2507
	21st to end	Night	34% 10% 13% 24% 19% 1	2751
June	1st to 10th	Night	34% 8% 13% 26% 18% 2	1520
	11th to 20th	Night	34% 8% 13% 22% 21% 2	1520
	21st to end	Night	33% 7% 15% 25% 17% 4	1520
July	1st to 10th	Night	39% 4 18% 26% 11% 2	2490
	11th to 20th	Night	24% 5% 17% 36% 16% 1	2482
	21st to end	Night	31% 6% 19% 21% 21% 2	2662
August	1st to 10th	Night	34% 5% 13% 28% 18% 1	2728
	11th to 20th	Night	34% 5% 12% 33% 15% 1	2908
	21st to end	Night	34% 5% 14% 26% 18% 3	3476
September	1st to 10th	Night	31% 7% 10% 26% 25% 1	1900
	11th to 20th	Night	32% 5% 12% 32% 17% 1	1900
	21st to end	Night	31% 6% 10% 30% 21% 1	2128
October	1st to 10th	Night	26% 3 6% 35% 28% 2	3800
	11th to 20th	Night	30% 4 11% 26% 28% 1	3779
	21st to end	Night	46% 4 9% 26% 14% 1	4298
November	1st to 10th	Night	41% 6% 13% 22% 16% 2	2536
	11th to 20th	Night	52% 6% 13% 18% 10% 1	2718
	21st to end	Night	51% 4 14% 23% 8% 1	2723
December	1st to 10th	Night	55% 6% 13% 19% 7% 1	2660
	11th to 20th	Night	56% 7% 13% 17% 6%	3281
	21st to end	Night	68% 6% 9% 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	19% 16% 35% 20% 8% 3	270
	11th to 20th	Day	21% 16% 43% 15% 5%	270
	21st to end	Day	22% 19% 33% 22% 4	297
February	1st to 10th	Day	16% 20% 43% 15% 6% 1	270
	11th to 20th	Day	19% 27% 32% 16% 6% 1	270
	21st to end	Day	20% 20% 45% 12% 2	225
March	1st to 10th	Day	19% 21% 41% 14% 5%	270
	11th to 20th	Day	21% 20% 34% 16% 6% 2	270
	21st to end	Day	27% 18% 29% 18% 7% 1	410
April	1st to 10th	Day	29% 15% 33% 19% 4	460
	11th to 20th	Day	27% 18% 26% 18% 9% 1	452
	21st to end	Day	23% 16% 30% 20% 9% 2	465
May	1st to 10th	Day	20% 15% 32% 23% 7% 2	653
	11th to 20th	Day	21% 15% 26% 25% 12% 2	675
	21st to end	Day	19% 10% 28% 25% 14% 5%	734
June	1st to 10th	Day	10% 8% 29% 31% 18% 4	680
	11th to 20th	Day	17% 7% 34% 24% 16% 3	680
	21st to end	Day	15% 9% 31% 28% 13% 4	680
July	1st to 10th	Day	9% 3 22% 30% 24% 11%	671
	11th to 20th	Day	9% 6% 28% 32% 19% 6%	668
	21st to end	Day	7% 4 27% 36% 19% 6%	739
August	1st to 10th	Day	8% 3 24% 34% 23% 8%	676
	11th to 20th	Day	16% 5% 19% 27% 23% 10%	618
	21st to end	Day	12% 6% 22% 32% 20% 7%	539
September	1st to 10th	Day	16% 8% 23% 30% 18% 5%	490
	11th to 20th	Day	13% 7% 21% 36% 19% 5%	490
	21st to end	Day	17% 13% 29% 23% 17% 1	425
October	1st to 10th	Day	17% 10% 33% 27% 12% 1	300
	11th to 20th	Day	29% 14% 33% 18% 6%	300
	21st to end	Day	26% 17% 33% 18% 6% 1	330
November	1st to 10th	Day	18% 14% 39% 20% 6% 2	300
	11th to 20th	Day	18% 23% 37% 15% 6% 1	300
	21st to end	Day	23% 13% 39% 20% 5%	282
December	1st to 10th	Day	16% 17% 40% 19% 7% 1	270
	11th to 20th	Day	20% 16% 37% 20% 6%	270
	21st to end	Day	29% 16% 38% 15% 2	297
January	1st to 10th	Night	14% 15% 35% 27% 7% 1	950
	11th to 20th	Night	19% 14% 35% 26% 5% 1	950
	21st to end	Night	20% 12% 35% 27% 5% 1	1045
February	1st to 10th	Night	16% 15% 35% 28% 6% 1	950
	11th to 20th	Night	17% 14% 39% 24% 6%	891
	21st to end	Night	21% 15% 36% 24% 4	628
March	1st to 10th	Night	21% 13% 36% 23% 6%	755
	11th to 20th	Night	19% 12% 34% 27% 8% 1	570
	21st to end	Night	25% 11% 29% 28% 6% 1	627
April	1st to 10th	Night	20% 14% 36% 25% 4	570
	11th to 20th	Night	23% 13% 30% 28% 6%	563
	21st to end	Night	23% 7% 32% 29% 8% 1	570
May	1st to 10th	Night	20% 9% 32% 32% 6% 1	570
	11th to 20th	Night	18% 9% 28% 34% 9% 1	561
	21st to end	Night	16% 5% 28% 36% 14% 1	617
June	1st to 10th	Night	12% 5% 29% 40% 13% 1	570
	11th to 20th	Night	13% 4 31% 39% 13%	570
	21st to end	Night	13% 4 27% 41% 15% 1	570
July	1st to 10th	Night	8% 1 19% 39% 29% 3	555
	11th to 20th	Night	8% 2 20% 44% 23% 2	552
	21st to end	Night	7% 2 15% 49% 24% 2	624
August	1st to 10th	Night	7% 2 16% 47% 26% 1	567
	11th to 20th	Night	10% 3 17% 40% 24% 6%	564
	21st to end	Night	12% 3 17% 43% 23% 2	627
September	1st to 10th	Night	12% 4 21% 38% 20% 5%	570
	11th to 20th	Night	14% 4 21% 34% 24% 3	570
	21st to end	Night	12% 10% 26% 34% 17% 1	736
October	1st to 10th	Night	16% 7% 28% 30% 17% 2	760
	11th to 20th	Night	19% 12% 32% 28% 9%	760
	21st to end	Night	22% 13% 30% 28% 7% 1	836
November	1st to 10th	Night	19% 11% 36% 25% 9%	780
	11th to 20th	Night	19% 16% 38% 22% 6%	918
	21st to end	Night	21% 15% 34% 24% 7%	973
December	1st to 10th	Night	18% 13% 40% 23% 5% 1	950
	11th to 20th	Night	21% 13% 36% 24% 6%	950
	21st to end	Night	26% 15% 34% 21% 3	1045

Page generated at 2024-11-22 07:02:29. Version ac07

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