Star City Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Star City Observing Site clear sky chart from 2005-11-06 to 2024-11-05.

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	15% 9% 3 7% 5% 4 5% 4 6% 7% 36%	101156
	Night	15% 9% 3 7% 5% 4 4 3 5% 7% 38%	97846
Transparency	Day	45% 5% 11% 23% 14% 2	104898
	Night	44% 5% 10% 22% 16% 3	102243
Seeing	Day	21% 12% 24% 22% 15% 7%	14940
	Night	20% 10% 22% 29% 17% 2	24990

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	15% 18% 8% 10% 4 4 4 3 5% 6% 23%	2836
	11th to 20th	Day	18% 16% 8% 12% 7% 4 3 2 3 3 23%	2840
	21st to end	Day	22% 19% 4 8% 4 4 4 3 4 5% 25%	3124
February	1st to 10th	Day	18% 14% 4 9% 4 4 4 3 5% 6% 30%	1744
	11th to 20th	Day	23% 10% 4 9% 4 4 4 3 4 5% 30%	1848
	21st to end	Day	24% 11% 3 8% 4 4 3 4 4 5% 30%	1570
March	1st to 10th	Day	22% 14% 3 7% 4 4 4 3 5% 5% 29%	3307
	11th to 20th	Day	14% 7% 3 7% 4 4 4 3 5% 6% 44%	3480
	21st to end	Day	17% 8% 3 5% 4 4 4 4 6% 7% 37%	3815
April	1st to 10th	Day	14% 9% 3 7% 5% 4 4 4 5% 7% 37%	2090
	11th to 20th	Day	15% 7% 3 7% 4 4 3 3 5% 6% 42%	2361
	21st to end	Day	17% 8% 2 7% 4 4 5% 3 5% 7% 38%	2470
May	1st to 10th	Day	16% 10% 3 10% 6% 5% 5% 4 6% 6% 28%	4082
	11th to 20th	Day	16% 9% 3 8% 5% 5% 5% 4 5% 6% 32%	4081
	21st to end	Day	10% 5% 2 6% 5% 5% 6% 6% 9% 10% 35%	4476
June	1st to 10th	Day	11% 6% 2 6% 6% 4 6% 4 7% 9% 39%	2470
	11th to 20th	Day	8% 5% 2 7% 5% 6% 6% 5% 7% 9% 40%	2470
	21st to end	Day	9% 7% 2 5% 5% 5% 5% 5% 8% 9% 40%	2470
July	1st to 10th	Day	8% 5% 2 7% 5% 5% 6% 5% 7% 10% 41%	4120
	11th to 20th	Day	9% 6% 2 6% 5% 4 5% 5% 8% 10% 41%	4120
	21st to end	Day	17% 10% 4 9% 7% 6% 5% 4 6% 8% 24%	4466
August	1st to 10th	Day	9% 6% 2 7% 5% 4 6% 5% 8% 10% 36%	4104
	11th to 20th	Day	10% 6% 2 7% 5% 5% 5% 4 8% 10% 39%	4044
	21st to end	Day	6% 3 1 4 4 4 5% 4 6% 9% 54%	4325
September	1st to 10th	Day	13% 5% 1 5% 4 4 4 4 6% 8% 45%	2090
	11th to 20th	Day	13% 5% 2 6% 4 4 4 4 5% 8% 44%	2090
	21st to end	Day	19% 6% 2 6% 4 4 3 2 4 5% 44%	2090
October	1st to 10th	Day	13% 5% 2 4 4 4 4 3 5% 7% 49%	2049
	11th to 20th	Day	15% 6% 2 6% 3 4 3 2 5% 6% 50%	1900
	21st to end	Day	20% 7% 3 5% 3 3 3 3 4 7% 43%	2090
November	1st to 10th	Day	12% 6% 2 5% 2 3 3 4 5% 5% 52%	1727
	11th to 20th	Day	13% 9% 3 7% 5% 3 4 4 4 5% 42%	1710
	21st to end	Day	16% 10% 3 7% 3 4 4 3 4 6% 40%	1710
December	1st to 10th	Day	25% 12% 4 7% 4 4 4 3 5% 6% 26%	1710
	11th to 20th	Day	19% 14% 4 8% 4 3 4 3 4 6% 32%	2153
	21st to end	Day	17% 16% 4 9% 6% 5% 6% 4 6% 6% 22%	3124
January	1st to 10th	Night	17% 19% 6% 11% 5% 4 4 3 4 4 23%	4109
	11th to 20th	Night	21% 14% 4 10% 5% 3 4 3 4 4 30%	4120
	21st to end	Night	23% 13% 4 9% 5% 4 3 3 3 4 28%	4532
February	1st to 10th	Night	18% 11% 5% 8% 5% 5% 4 3 5% 6% 31%	2432
	11th to 20th	Night	23% 12% 4 7% 4 3 4 3 4 5% 30%	2218
	21st to end	Night	23% 13% 4 7% 4 4 4 3 5% 4 28%	1884
March	1st to 10th	Night	22% 12% 3 7% 5% 5% 4 3 4 6% 31%	3546
	11th to 20th	Night	14% 8% 3 5% 4 4 4 4 5% 6% 44%	3480
	21st to end	Night	13% 7% 2 6% 5% 5% 5% 4 6% 7% 40%	3817
April	1st to 10th	Night	13% 9% 2 7% 6% 4 4 4 5% 7% 41%	2090
	11th to 20th	Night	15% 8% 2 6% 3 3 4 3 6% 8% 42%	1784
	21st to end	Night	15% 8% 3 5% 5% 5% 4 3 5% 7% 40%	1710
May	1st to 10th	Night	18% 9% 3 8% 6% 6% 5% 3 6% 7% 29%	2813
	11th to 20th	Night	17% 7% 3 7% 4 4 4 4 5% 8% 37%	2812
	21st to end	Night	9% 6% 3 7% 5% 4 5% 4 6% 9% 42%	3079
June	1st to 10th	Night	9% 5% 2 5% 4 4 6% 5% 7% 10% 42%	1710
	11th to 20th	Night	6% 5% 2 6% 4 5% 5% 5% 8% 10% 43%	1710
	21st to end	Night	9% 5% 2 6% 4 5% 5% 5% 6% 10% 42%	1710
July	1st to 10th	Night	8% 4 2 7% 6% 5% 5% 5% 8% 11% 40%	2840
	11th to 20th	Night	8% 6% 2 5% 4 4 5% 4 7% 9% 47%	2840
	21st to end	Night	13% 10% 3 9% 5% 4 6% 5% 6% 9% 31%	3087
August	1st to 10th	Night	9% 6% 2 7% 5% 5% 5% 4 8% 10% 38%	2825
	11th to 20th	Night	10% 6% 3 6% 5% 4 5% 4 6% 9% 41%	2785
	21st to end	Night	5% 3 1 4 3 3 4 4 6% 8% 59%	3295
September	1st to 10th	Night	11% 4 2 6% 4 4 4 3 7% 8% 46%	2090
	11th to 20th	Night	12% 5% 2 7% 5% 3 4 3 4 6% 49%	2090
	21st to end	Night	12% 6% 2 6% 4 3 4 4 5% 7% 47%	2090
October	1st to 10th	Night	12% 5% 2 5% 4 3 3 3 5% 6% 53%	2129
	11th to 20th	Night	16% 6% 2 6% 3 3 3 2 4 5% 49%	2280
	21st to end	Night	18% 7% 2 5% 4 3 3 3 5% 6% 44%	2508
November	1st to 10th	Night	13% 6% 2 5% 4 3 4 2 4 6% 51%	2447
	11th to 20th	Night	15% 8% 2 7% 3 4 4 3 5% 6% 43%	2470
	21st to end	Night	15% 10% 2 5% 4 4 3 4 5% 6% 42%	2470
December	1st to 10th	Night	21% 15% 4 8% 4 3 3 3 5% 5% 28%	2470
	11th to 20th	Night	18% 13% 5% 7% 5% 4 4 3 5% 5% 31%	3042
	21st to end	Night	18% 16% 4 9% 6% 5% 5% 3 6% 7% 22%	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	62% 4 8% 17% 9% 1	2837
	11th to 20th	Day	68% 2 7% 16% 6% 1	2840
	21st to end	Day	62% 3 6% 22% 6% 1	3124
February	1st to 10th	Day	57% 3 8% 20% 11% 1	1744
	11th to 20th	Day	57% 3 7% 19% 12% 2	1858
	21st to end	Day	57% 4 8% 16% 12% 3	1570
March	1st to 10th	Day	57% 4 8% 17% 12% 2	3307
	11th to 20th	Day	42% 3 9% 24% 19% 2	3480
	21st to end	Day	45% 4 10% 27% 12% 2	3815
April	1st to 10th	Day	45% 5% 10% 23% 15% 3	2090
	11th to 20th	Day	42% 4 9% 22% 19% 5%	2361
	21st to end	Day	47% 5% 10% 24% 11% 3	2470
May	1st to 10th	Day	54% 6% 10% 19% 9% 1	4120
	11th to 20th	Day	50% 7% 10% 22% 10% 1	4085
	21st to end	Day	37% 9% 15% 21% 15% 2	4489
June	1st to 10th	Day	40% 7% 13% 24% 15% 1	2470
	11th to 20th	Day	39% 8% 13% 20% 18% 2	2470
	21st to end	Day	37% 8% 14% 21% 16% 3	2470
July	1st to 10th	Day	37% 8% 19% 22% 13% 1	4055
	11th to 20th	Day	36% 6% 13% 33% 10% 2	4051
	21st to end	Day	58% 7% 9% 16% 9% 1	4324
August	1st to 10th	Day	39% 8% 15% 26% 10%	4091
	11th to 20th	Day	39% 7% 12% 30% 12% 1	4083
	21st to end	Day	26% 6% 14% 34% 19% 2	4325
September	1st to 10th	Day	37% 6% 11% 23% 18% 6%	2090
	11th to 20th	Day	38% 5% 10% 27% 17% 2	2090
	21st to end	Day	43% 4 10% 22% 20% 2	2090
October	1st to 10th	Day	29% 4 8% 22% 34% 3	3400
	11th to 20th	Day	26% 2 10% 28% 29% 3	3140
	21st to end	Day	30% 2 9% 32% 20% 7%	3428
November	1st to 10th	Day	33% 4 9% 25% 26% 3	1727
	11th to 20th	Day	44% 3 7% 23% 19% 4	1710
	21st to end	Day	46% 3 9% 22% 18% 2	1710
December	1st to 10th	Day	59% 4 10% 19% 7% 1	1710
	11th to 20th	Day	54% 3 9% 17% 15% 1	2150
	21st to end	Day	60% 5% 10% 20% 5%	3124
January	1st to 10th	Night	64% 4 8% 15% 8% 1	4109
	11th to 20th	Night	57% 4 6% 19% 12% 2	4120
	21st to end	Night	59% 3 8% 20% 9% 1	4532
February	1st to 10th	Night	55% 3 10% 20% 11% 1	2432
	11th to 20th	Night	57% 3 8% 18% 12% 2	2219
	21st to end	Night	58% 4 9% 15% 11% 3	1884
March	1st to 10th	Night	55% 4 7% 18% 14% 2	3546
	11th to 20th	Night	40% 4 9% 30% 15% 3	3480
	21st to end	Night	41% 5% 11% 24% 17% 1	3817
April	1st to 10th	Night	43% 5% 10% 22% 17% 3	2090
	11th to 20th	Night	40% 5% 10% 22% 17% 7%	1784
	21st to end	Night	44% 6% 11% 24% 13% 2	1710
May	1st to 10th	Night	52% 8% 11% 19% 8% 2	2840
	11th to 20th	Night	45% 6% 14% 25% 9% 1	2813
	21st to end	Night	36% 9% 14% 22% 17% 3	3087
June	1st to 10th	Night	34% 8% 17% 22% 17% 3	1710
	11th to 20th	Night	32% 9% 17% 21% 19% 3	1710
	21st to end	Night	34% 8% 15% 23% 15% 5%	1710
July	1st to 10th	Night	36% 9% 17% 24% 13% 2	2795
	11th to 20th	Night	32% 7% 15% 32% 13% 2	2786
	21st to end	Night	49% 7% 12% 19% 12% 1	2988
August	1st to 10th	Night	38% 9% 14% 25% 12% 1	2814
	11th to 20th	Night	39% 6% 12% 28% 14% 1	2812
	21st to end	Night	22% 7% 13% 33% 23% 3	3295
September	1st to 10th	Night	35% 7% 12% 22% 16% 8%	2090
	11th to 20th	Night	37% 6% 10% 22% 22% 3	2090
	21st to end	Night	36% 6% 10% 24% 22% 2	2090
October	1st to 10th	Night	28% 4 7% 23% 33% 4	3558
	11th to 20th	Night	29% 3 6% 26% 27% 9%	3779
	21st to end	Night	29% 3 7% 26% 27% 8%	4120
November	1st to 10th	Night	36% 4 8% 22% 24% 6%	2447
	11th to 20th	Night	42% 4 8% 20% 20% 6%	2470
	21st to end	Night	43% 4 8% 27% 16% 2	2470
December	1st to 10th	Night	58% 4 8% 19% 9% 2	2470
	11th to 20th	Night	55% 3 7% 22% 11% 1	3044
	21st to end	Night	60% 5% 9% 17% 9%	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	28% 23% 31% 14% 3 1	270
	11th to 20th	Day	39% 23% 25% 12% 1	270
	21st to end	Day	30% 26% 28% 13% 2 1	297
February	1st to 10th	Day	28% 20% 34% 13% 5%	270
	11th to 20th	Day	44% 22% 26% 6% 1 1	270
	21st to end	Day	38% 20% 31% 11%	225
March	1st to 10th	Day	32% 18% 30% 14% 6%	379
	11th to 20th	Day	27% 22% 29% 17% 4 1	460
	21st to end	Day	29% 19% 29% 17% 6%	506
April	1st to 10th	Day	29% 18% 25% 18% 10% 1	460
	11th to 20th	Day	21% 21% 28% 17% 11% 3	452
	21st to end	Day	25% 14% 32% 20% 8% 2	460
May	1st to 10th	Day	22% 17% 29% 18% 10% 4	463
	11th to 20th	Day	17% 11% 28% 26% 13% 5%	487
	21st to end	Day	14% 6% 26% 23% 21% 9%	529
June	1st to 10th	Day	13% 7% 23% 28% 20% 8%	490
	11th to 20th	Day	11% 7% 19% 30% 22% 11%	490
	21st to end	Day	13% 5% 26% 26% 19% 12%	490
July	1st to 10th	Day	15% 4 18% 24% 20% 20%	485
	11th to 20th	Day	8% 5% 20% 29% 23% 15%	484
	21st to end	Day	15% 6% 17% 28% 23% 12%	532
August	1st to 10th	Day	15% 4 18% 24% 27% 12%	486
	11th to 20th	Day	13% 6% 14% 29% 25% 11%	479
	21st to end	Day	12% 3 13% 26% 32% 16%	539
September	1st to 10th	Day	14% 3 15% 23% 32% 13%	490
	11th to 20th	Day	15% 3 13% 28% 26% 14%	490
	21st to end	Day	22% 9% 19% 27% 17% 7%	490
October	1st to 10th	Day	14% 8% 22% 26% 22% 8%	490
	11th to 20th	Day	17% 11% 25% 26% 16% 5%	490
	21st to end	Day	25% 13% 22% 26% 13% 2	539
November	1st to 10th	Day	18% 12% 30% 26% 11% 3	301
	11th to 20th	Day	25% 15% 28% 19% 12% 1	270
	21st to end	Day	24% 17% 28% 21% 9% 1	270
December	1st to 10th	Day	32% 19% 26% 17% 5% 1	270
	11th to 20th	Day	28% 18% 29% 19% 4 3	270
	21st to end	Day	30% 18% 34% 12% 5% 1	297
January	1st to 10th	Night	28% 18% 28% 21% 5%	760
	11th to 20th	Night	32% 16% 27% 21% 4	760
	21st to end	Night	25% 17% 31% 24% 2	836
February	1st to 10th	Night	26% 14% 30% 28% 2	760
	11th to 20th	Night	33% 17% 29% 19% 2	743
	21st to end	Night	33% 17% 30% 18% 2	628
March	1st to 10th	Night	28% 15% 26% 27% 5%	760
	11th to 20th	Night	26% 15% 29% 22% 7%	760
	21st to end	Night	20% 15% 30% 27% 8%	836
April	1st to 10th	Night	20% 16% 27% 28% 8%	760
	11th to 20th	Night	21% 12% 24% 29% 13% 1	589
	21st to end	Night	18% 10% 33% 31% 8% 1	570
May	1st to 10th	Night	20% 8% 26% 31% 12% 2	570
	11th to 20th	Night	16% 7% 23% 33% 19% 2	561
	21st to end	Night	10% 4 17% 34% 29% 6%	617
June	1st to 10th	Night	11% 3 18% 37% 27% 4	570
	11th to 20th	Night	8% 3 15% 39% 30% 6%	570
	21st to end	Night	10% 2 18% 36% 29% 4	570
July	1st to 10th	Night	13% 2 11% 32% 35% 7%	555
	11th to 20th	Night	8% 2 10% 34% 40% 5%	552
	21st to end	Night	11% 4 9% 34% 34% 8%	624
August	1st to 10th	Night	10% 3 9% 33% 40% 5%	567
	11th to 20th	Night	13% 2 9% 32% 37% 8%	564
	21st to end	Night	10% 1 7% 31% 42% 8%	636
September	1st to 10th	Night	12% 3 11% 30% 38% 6%	760
	11th to 20th	Night	14% 2 14% 27% 38% 4	760
	21st to end	Night	15% 5% 19% 29% 29% 3	760
October	1st to 10th	Night	14% 4 17% 31% 30% 4	760
	11th to 20th	Night	19% 8% 20% 32% 18% 2	760
	21st to end	Night	22% 9% 23% 32% 14% 1	836
November	1st to 10th	Night	16% 8% 22% 34% 18% 2	760
	11th to 20th	Night	19% 13% 25% 30% 11% 1	760
	21st to end	Night	21% 11% 21% 35% 11% 1	760
December	1st to 10th	Night	30% 15% 24% 26% 5%	760
	11th to 20th	Night	25% 12% 28% 28% 6% 1	760
	21st to end	Night	31% 14% 22% 29% 5%	836

Page generated at 2024-11-03 02:11:22. Version ac07

Copyright © 2024 Attilla Danko.