Mark's Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mark's Observing Site clear sky chart from 2005-11-06 to 2024-11-12.

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	8% 5% 2 5% 4 4 4 3 5% 7% 52%	101266
	Night	8% 5% 2 5% 3 3 4 3 5% 7% 55%	98040
Transparency	Day	30% 5% 11% 27% 22% 5%	105000
	Night	28% 4 11% 27% 24% 6%	102423
Seeing	Day	11% 6% 28% 32% 18% 4	15601
	Night	11% 7% 33% 37% 12% 1	25476

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	8% 7% 2 9% 5% 4 4 3 5% 7% 46%	2847
	11th to 20th	Day	7% 8% 3 7% 5% 5% 4 3 6% 7% 44%	2850
	21st to end	Day	10% 11% 3 7% 3 2 3 2 4 5% 49%	3135
February	1st to 10th	Day	8% 9% 3 8% 5% 4 3 3 4 7% 47%	1762
	11th to 20th	Day	6% 6% 3 8% 3 4 4 3 5% 7% 52%	1849
	21st to end	Day	7% 6% 2 5% 3 3 4 4 5% 6% 54%	1570
March	1st to 10th	Day	9% 6% 1 4 3 3 3 3 4 7% 57%	3275
	11th to 20th	Day	8% 5% 1 4 2 3 3 3 5% 7% 59%	3480
	21st to end	Day	10% 7% 2 6% 4 4 4 3 5% 8% 47%	3814
April	1st to 10th	Day	9% 6% 2 4 3 3 3 3 6% 7% 53%	2099
	11th to 20th	Day	11% 7% 2 6% 4 4 4 3 5% 7% 47%	2356
	21st to end	Day	15% 6% 2 5% 4 3 4 4 5% 7% 44%	2470
May	1st to 10th	Day	16% 8% 2 6% 4 4 4 3 5% 6% 42%	4082
	11th to 20th	Day	12% 5% 2 5% 4 3 4 4 5% 6% 50%	4082
	21st to end	Day	11% 5% 3 6% 4 4 5% 4 6% 8% 45%	4477
June	1st to 10th	Day	5% 4 2 5% 3 3 4 4 6% 9% 56%	2470
	11th to 20th	Day	5% 4 1 4 5% 4 4 4 6% 8% 56%	2470
	21st to end	Day	5% 3 1 3 3 3 5% 4 7% 9% 56%	2470
July	1st to 10th	Day	8% 5% 2 5% 4 4 4 4 6% 7% 50%	4120
	11th to 20th	Day	4 3 1 4 4 4 5% 4 7% 10% 54%	4120
	21st to end	Day	5% 3 1 5% 4 4 5% 4 7% 9% 52%	4465
August	1st to 10th	Day	6% 6% 2 5% 4 4 4 3 6% 8% 51%	4104
	11th to 20th	Day	8% 4 1 4 4 3 4 4 7% 8% 53%	4041
	21st to end	Day	3 3 1 4 3 3 4 3 6% 9% 60%	4340
September	1st to 10th	Day	9% 5% 2 3 3 3 4 3 4 7% 57%	2104
	11th to 20th	Day	8% 4 2 5% 3 4 3 4 4 7% 56%	2090
	21st to end	Day	8% 4 2 5% 4 3 3 3 5% 6% 58%	2090
October	1st to 10th	Day	12% 4 1 4 3 2 3 2 4 6% 59%	2066
	11th to 20th	Day	9% 3 1 4 2 2 2 2 3 5% 65%	1900
	21st to end	Day	10% 6% 2 4 3 3 2 2 4 5% 60%	2070
November	1st to 10th	Day	7% 4 2 3 3 3 4 2 5% 6% 61%	1763
	11th to 20th	Day	7% 5% 1 4 4 3 3 2 4 6% 61%	1719
	21st to end	Day	11% 5% 1 4 3 3 2 2 3 4 62%	1710
December	1st to 10th	Day	7% 6% 2 5% 4 3 3 3 6% 7% 54%	1710
	11th to 20th	Day	9% 7% 3 6% 3 3 3 3 4 7% 53%	2161
	21st to end	Day	9% 10% 4 9% 5% 4 4 3 5% 7% 39%	3135
January	1st to 10th	Night	8% 8% 3 10% 4 4 4 3 4 5% 46%	4108
	11th to 20th	Night	5% 5% 2 5% 5% 4 4 3 5% 5% 57%	4120
	21st to end	Night	14% 10% 3 6% 2 3 3 2 3 4 51%	4532
February	1st to 10th	Night	9% 9% 3 6% 4 4 3 3 4 6% 48%	2434
	11th to 20th	Night	9% 7% 3 5% 4 3 3 3 6% 6% 51%	2218
	21st to end	Night	7% 5% 3 5% 4 4 3 3 4 6% 56%	1884
March	1st to 10th	Night	7% 5% 1 4 3 3 4 3 4 6% 61%	3582
	11th to 20th	Night	7% 6% 1 5% 3 3 4 4 5% 7% 55%	3480
	21st to end	Night	10% 8% 2 5% 3 3 3 3 4 6% 52%	3817
April	1st to 10th	Night	10% 4 1 4 4 3 3 4 5% 8% 54%	2076
	11th to 20th	Night	12% 5% 2 5% 3 3 5% 4 5% 7% 50%	1775
	21st to end	Night	14% 6% 2 5% 4 3 4 4 5% 7% 49%	1710
May	1st to 10th	Night	17% 6% 2 4 4 3 3 3 4 6% 49%	2823
	11th to 20th	Night	12% 4 1 4 3 3 4 4 6% 9% 50%	2823
	21st to end	Night	8% 4 1 4 3 3 4 4 6% 9% 55%	3090
June	1st to 10th	Night	6% 3 1 5% 2 3 3 5% 6% 9% 58%	1710
	11th to 20th	Night	5% 3 1 3 4 3 4 5% 8% 8% 55%	1710
	21st to end	Night	4 3 2 3 3 4 4 3 7% 10% 58%	1710
July	1st to 10th	Night	5% 3 2 5% 4 5% 4 3 7% 9% 52%	2850
	11th to 20th	Night	3 3 1 4 3 3 4 4 7% 11% 57%	2850
	21st to end	Night	5% 4 2 4 3 4 5% 4 8% 12% 50%	3098
August	1st to 10th	Night	5% 3 1 5% 4 4 4 3 6% 10% 55%	2836
	11th to 20th	Night	7% 4 2 6% 4 4 5% 4 5% 7% 52%	2798
	21st to end	Night	4 2 1 3 2 2 3 3 6% 9% 63%	3322
September	1st to 10th	Night	7% 3 1 4 4 4 3 3 5% 6% 60%	2076
	11th to 20th	Night	7% 4 2 5% 3 4 3 3 4 6% 59%	2090
	21st to end	Night	6% 3 2 4 3 3 4 3 5% 6% 62%	2090
October	1st to 10th	Night	9% 4 2 4 3 3 3 2 4 6% 59%	2095
	11th to 20th	Night	9% 2 1 2 3 3 2 2 3 5% 68%	2280
	21st to end	Night	10% 4 1 4 3 3 3 3 3 5% 63%	2526
November	1st to 10th	Night	8% 4 1 4 2 2 2 2 4 6% 65%	2535
	11th to 20th	Night	7% 5% 1 3 2 2 3 2 4 6% 64%	2484
	21st to end	Night	11% 6% 2 4 2 2 3 2 4 5% 60%	2470
December	1st to 10th	Night	7% 6% 2 4 3 3 4 3 5% 6% 57%	2470
	11th to 20th	Night	9% 5% 2 5% 3 3 4 3 4 6% 56%	3036
	21st to end	Night	12% 9% 3 6% 3 4 3 3 5% 7% 44%	4532

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	38% 5% 11% 27% 18% 1	2848
	11th to 20th	Day	38% 6% 15% 24% 12% 5%	2850
	21st to end	Day	39% 3 12% 27% 17% 2	3135
February	1st to 10th	Day	39% 4 12% 25% 15% 5%	1762
	11th to 20th	Day	32% 5% 13% 26% 17% 6%	1859
	21st to end	Day	30% 4 10% 25% 25% 7%	1570
March	1st to 10th	Day	27% 4 9% 21% 29% 10%	3275
	11th to 20th	Day	25% 5% 13% 24% 30% 3	3480
	21st to end	Day	35% 5% 14% 33% 11% 2	3814
April	1st to 10th	Day	30% 4 12% 26% 21% 6%	2099
	11th to 20th	Day	37% 5% 10% 26% 17% 5%	2356
	21st to end	Day	38% 6% 11% 29% 15% 2	2470
May	1st to 10th	Day	42% 7% 9% 20% 14% 7%	4120
	11th to 20th	Day	33% 7% 12% 29% 18% 1	4086
	21st to end	Day	35% 8% 12% 24% 17% 4	4489
June	1st to 10th	Day	24% 7% 18% 32% 16% 4	2470
	11th to 20th	Day	25% 6% 13% 29% 21% 6%	2470
	21st to end	Day	23% 6% 13% 26% 25% 7%	2470
July	1st to 10th	Day	32% 5% 11% 23% 23% 5%	4056
	11th to 20th	Day	23% 5% 14% 31% 22% 4	4051
	21st to end	Day	25% 6% 13% 27% 27% 2	4325
August	1st to 10th	Day	31% 6% 12% 25% 23% 3	4090
	11th to 20th	Day	29% 5% 17% 26% 19% 4	4080
	21st to end	Day	21% 4 15% 34% 21% 6%	4339
September	1st to 10th	Day	28% 5% 8% 25% 23% 10%	2104
	11th to 20th	Day	28% 4 9% 27% 26% 5%	2090
	21st to end	Day	27% 5% 9% 26% 25% 8%	2090
October	1st to 10th	Day	18% 3 5% 22% 42% 11%	3430
	11th to 20th	Day	18% 2 9% 30% 31% 10%	3140
	21st to end	Day	24% 2 8% 25% 32% 9%	3386
November	1st to 10th	Day	25% 3 9% 28% 28% 7%	1763
	11th to 20th	Day	26% 3 9% 27% 29% 7%	1719
	21st to end	Day	28% 2 8% 28% 29% 5%	1710
December	1st to 10th	Day	29% 4 12% 31% 22% 3	1710
	11th to 20th	Day	32% 4 8% 31% 22% 3	2159
	21st to end	Day	44% 5% 9% 26% 15% 2	3135
January	1st to 10th	Night	39% 5% 8% 28% 16% 3	4108
	11th to 20th	Night	28% 5% 14% 27% 22% 3	4120
	21st to end	Night	39% 4 10% 25% 20% 2	4532
February	1st to 10th	Night	38% 3 12% 24% 17% 6%	2434
	11th to 20th	Night	33% 4 11% 27% 19% 6%	2218
	21st to end	Night	29% 4 8% 23% 25% 11%	1884
March	1st to 10th	Night	25% 4 7% 25% 30% 9%	3582
	11th to 20th	Night	27% 5% 10% 24% 31% 4	3480
	21st to end	Night	34% 5% 15% 33% 11% 2	3817
April	1st to 10th	Night	29% 4 12% 24% 24% 8%	2076
	11th to 20th	Night	33% 5% 13% 24% 21% 4	1775
	21st to end	Night	35% 6% 12% 23% 21% 4	1710
May	1st to 10th	Night	37% 6% 11% 20% 17% 10%	2850
	11th to 20th	Night	29% 8% 16% 32% 15% 1	2824
	21st to end	Night	25% 7% 17% 28% 19% 3	3099
June	1st to 10th	Night	20% 7% 19% 32% 18% 3	1710
	11th to 20th	Night	23% 6% 15% 31% 20% 4	1710
	21st to end	Night	21% 6% 13% 29% 22% 8%	1710
July	1st to 10th	Night	28% 5% 15% 22% 26% 5%	2805
	11th to 20th	Night	20% 4 12% 31% 27% 5%	2796
	21st to end	Night	26% 6% 14% 30% 22% 2	2999
August	1st to 10th	Night	25% 4 13% 29% 23% 6%	2826
	11th to 20th	Night	31% 6% 14% 25% 20% 4	2825
	21st to end	Night	19% 4 16% 37% 20% 6%	3322
September	1st to 10th	Night	26% 4 10% 24% 25% 11%	2076
	11th to 20th	Night	27% 4 9% 25% 28% 6%	2090
	21st to end	Night	24% 4 10% 23% 31% 9%	2090
October	1st to 10th	Night	18% 3 5% 16% 48% 10%	3498
	11th to 20th	Night	15% 3 8% 26% 33% 15%	3779
	21st to end	Night	20% 2 6% 25% 38% 9%	4150
November	1st to 10th	Night	23% 3 9% 27% 28% 10%	2535
	11th to 20th	Night	23% 3 7% 30% 30% 7%	2484
	21st to end	Night	28% 3 8% 26% 25% 9%	2470
December	1st to 10th	Night	29% 3 12% 28% 22% 5%	2470
	11th to 20th	Night	30% 3 7% 34% 20% 4	3037
	21st to end	Night	40% 5% 10% 28% 13% 4	4532

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	10% 8% 41% 26% 13% 2	270
	11th to 20th	Day	15% 11% 41% 25% 7%	270
	21st to end	Day	10% 9% 43% 31% 6% 1	297
February	1st to 10th	Day	13% 12% 44% 26% 4 1	270
	11th to 20th	Day	12% 9% 46% 23% 8% 1	270
	21st to end	Day	8% 13% 52% 22% 4 1	225
March	1st to 10th	Day	11% 9% 44% 29% 6% 1	270
	11th to 20th	Day	17% 11% 39% 23% 9% 2	270
	21st to end	Day	19% 11% 43% 22% 4 1	297
April	1st to 10th	Day	12% 15% 39% 27% 8%	279
	11th to 20th	Day	14% 13% 39% 30% 3	554
	21st to end	Day	18% 12% 38% 20% 9% 3	650
May	1st to 10th	Day	16% 8% 36% 28% 11% 2	653
	11th to 20th	Day	16% 8% 25% 28% 18% 4	675
	21st to end	Day	15% 6% 29% 29% 17% 4	734
June	1st to 10th	Day	5% 4 22% 36% 24% 9%	680
	11th to 20th	Day	6% 4 28% 40% 19% 4	680
	21st to end	Day	6% 4 28% 42% 18% 2	680
July	1st to 10th	Day	8% 1 12% 40% 30% 9%	671
	11th to 20th	Day	4 2 14% 43% 30% 8%	668
	21st to end	Day	8% 1 12% 35% 33% 11%	739
August	1st to 10th	Day	8% 2 13% 40% 31% 7%	676
	11th to 20th	Day	8% 2 14% 40% 32% 4	665
	21st to end	Day	4 2 13% 40% 33% 8%	634
September	1st to 10th	Day	11% 1 11% 34% 34% 9%	314
	11th to 20th	Day	5% 1 17% 44% 26% 8%	300
	21st to end	Day	14% 3 25% 27% 23% 9%	300
October	1st to 10th	Day	13% 5% 29% 25% 19% 9%	300
	11th to 20th	Day	8% 7% 36% 30% 14% 4	300
	21st to end	Day	19% 9% 31% 25% 13% 3	330
November	1st to 10th	Day	12% 10% 32% 31% 12% 3	300
	11th to 20th	Day	12% 8% 41% 24% 12% 3	273
	21st to end	Day	18% 9% 31% 26% 13% 2	270
December	1st to 10th	Day	7% 9% 35% 33% 13% 3	270
	11th to 20th	Day	12% 11% 38% 30% 9% 1	270
	21st to end	Day	16% 11% 44% 23% 5%	297
January	1st to 10th	Night	9% 9% 38% 36% 7%	950
	11th to 20th	Night	9% 11% 38% 33% 8% 1	950
	21st to end	Night	10% 8% 42% 34% 6%	1045
February	1st to 10th	Night	13% 11% 41% 31% 4 1	914
	11th to 20th	Night	13% 10% 40% 34% 4	744
	21st to end	Night	10% 12% 45% 29% 4	628
March	1st to 10th	Night	9% 12% 41% 33% 4	673
	11th to 20th	Night	15% 8% 37% 31% 8%	570
	21st to end	Night	18% 9% 41% 27% 5% 1	627
April	1st to 10th	Night	13% 11% 42% 27% 7%	570
	11th to 20th	Night	15% 12% 38% 30% 5%	563
	21st to end	Night	16% 9% 37% 30% 7% 1	570
May	1st to 10th	Night	17% 8% 35% 32% 7%	570
	11th to 20th	Night	15% 6% 27% 38% 13% 1	561
	21st to end	Night	13% 6% 28% 36% 15% 2	617
June	1st to 10th	Night	6% 4 26% 42% 21% 2	570
	11th to 20th	Night	5% 3 34% 44% 13%	570
	21st to end	Night	4 2 35% 45% 13%	570
July	1st to 10th	Night	8% 1 15% 50% 25% 2	555
	11th to 20th	Night	5% 1 19% 50% 24% 1	552
	21st to end	Night	8% 1 15% 47% 27% 1	624
August	1st to 10th	Night	5% 1 17% 50% 26% 1	567
	11th to 20th	Night	9% 2 14% 52% 23% 1	564
	21st to end	Night	4 1 17% 46% 30% 3	627
September	1st to 10th	Night	8% 1 22% 48% 20% 2	570
	11th to 20th	Night	8% 2 29% 43% 17% 2	570
	21st to end	Night	8% 4 27% 41% 19% 1	570
October	1st to 10th	Night	11% 4 29% 35% 20% 1	575
	11th to 20th	Night	10% 6% 39% 35% 9% 1	760
	21st to end	Night	13% 7% 35% 34% 11% 1	854
November	1st to 10th	Night	9% 6% 34% 37% 13% 1	975
	11th to 20th	Night	9% 9% 39% 34% 9%	956
	21st to end	Night	14% 8% 30% 38% 10%	950
December	1st to 10th	Night	10% 8% 36% 36% 8%	950
	11th to 20th	Night	14% 9% 40% 34% 4	950
	21st to end	Night	13% 11% 38% 32% 6%	1045

Page generated at 2024-11-08 21:45:41. Version ac07

Copyright © 2024 Attilla Danko.