StarHub Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the StarHub Observatory clear sky chart from 2005-11-06 to 2024-12-02.

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% 6% 2 7% 5% 5% 5% 4 6% 8% 41%	100849
	Night	13% 6% 2 6% 4 4 4 4 5% 7% 43%	98695
Transparency	Day	40% 7% 11% 20% 17% 5%	104492
	Night	39% 6% 11% 20% 18% 6%	103190
Seeing	Day	16% 9% 24% 25% 18% 8%	15516
	Night	15% 7% 25% 34% 17% 2	25545

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 3 3 2 3 6% 51%	2836
	11th to 20th	Day	12% 5% 2 6% 4 3 4 3 3 5% 52%	2840
	21st to end	Day	15% 8% 3 8% 4 4 5% 3 4 5% 42%	3124
February	1st to 10th	Day	15% 7% 3 6% 4 4 3 3 5% 6% 44%	1710
	11th to 20th	Day	19% 6% 2 6% 4 3 3 2 4 5% 46%	1769
	21st to end	Day	16% 7% 2 6% 5% 4 4 3 5% 6% 41%	1621
March	1st to 10th	Day	23% 9% 2 5% 4 3 4 3 5% 6% 35%	3435
	11th to 20th	Day	10% 6% 2 5% 3 4 3 3 5% 6% 54%	3480
	21st to end	Day	18% 6% 3 5% 4 3 3 3 4 5% 46%	3815
April	1st to 10th	Day	11% 5% 2 4 4 5% 3 3 5% 6% 52%	2272
	11th to 20th	Day	9% 5% 2 5% 4 4 4 3 6% 8% 51%	2254
	21st to end	Day	10% 5% 2 6% 4 4 4 4 5% 7% 49%	2280
May	1st to 10th	Day	9% 5% 3 7% 6% 6% 6% 5% 7% 10% 36%	3811
	11th to 20th	Day	17% 7% 3 8% 5% 5% 5% 4 7% 8% 33%	4081
	21st to end	Day	7% 4 2 5% 5% 5% 6% 5% 7% 10% 43%	4476
June	1st to 10th	Day	10% 6% 2 7% 6% 6% 5% 4 8% 9% 36%	2641
	11th to 20th	Day	9% 5% 2 6% 5% 5% 5% 5% 8% 9% 42%	2660
	21st to end	Day	8% 6% 2 6% 6% 6% 6% 5% 8% 11% 36%	2530
July	1st to 10th	Day	7% 5% 2 8% 6% 6% 6% 5% 9% 13% 33%	4120
	11th to 20th	Day	10% 7% 3 10% 7% 6% 7% 6% 8% 10% 26%	4120
	21st to end	Day	10% 8% 3 9% 7% 7% 7% 6% 8% 10% 25%	4466
August	1st to 10th	Day	20% 11% 4 10% 6% 5% 5% 5% 7% 8% 19%	4104
	11th to 20th	Day	10% 7% 3 8% 6% 5% 6% 5% 6% 10% 35%	3745
	21st to end	Day	7% 4 2 7% 5% 5% 6% 4 8% 10% 42%	4180
September	1st to 10th	Day	11% 5% 3 6% 6% 5% 5% 5% 7% 8% 38%	2280
	11th to 20th	Day	14% 8% 3 7% 5% 5% 5% 4 5% 8% 38%	2277
	21st to end	Day	17% 8% 4 9% 4 4 4 3 6% 7% 35%	1982
October	1st to 10th	Day	16% 5% 3 6% 4 4 4 3 4 7% 46%	1900
	11th to 20th	Day	13% 6% 1 5% 3 3 4 3 4 5% 53%	1900
	21st to end	Day	11% 4 2 6% 3 4 4 3 4 5% 54%	2090
November	1st to 10th	Day	13% 6% 2 6% 3 3 3 3 4 6% 50%	1957
	11th to 20th	Day	16% 5% 1 5% 4 3 4 2 5% 5% 50%	1920
	21st to end	Day	12% 6% 2 6% 3 2 2 2 6% 6% 52%	1725
December	1st to 10th	Day	16% 7% 2 6% 5% 5% 5% 3 5% 6% 40%	1528
	11th to 20th	Day	17% 6% 2 5% 3 2 3 2 3 5% 53%	1910
	21st to end	Day	14% 7% 3 7% 4 4 3 3 5% 7% 43%	3010
January	1st to 10th	Night	14% 8% 3 5% 4 4 4 3 5% 6% 45%	4109
	11th to 20th	Night	14% 6% 3 8% 5% 4 4 3 5% 6% 42%	4120
	21st to end	Night	16% 8% 2 6% 4 3 4 3 4 6% 44%	4532
February	1st to 10th	Night	17% 7% 2 5% 3 3 4 3 5% 6% 44%	2470
	11th to 20th	Night	19% 8% 3 5% 3 3 4 3 4 5% 42%	2294
	21st to end	Night	16% 6% 3 5% 4 4 4 3 5% 6% 44%	1829
March	1st to 10th	Night	24% 10% 3 7% 5% 4 4 3 4 5% 32%	3418
	11th to 20th	Night	13% 6% 2 5% 4 3 3 3 5% 7% 50%	3480
	21st to end	Night	16% 5% 1 4 3 3 4 3 5% 6% 49%	3817
April	1st to 10th	Night	11% 5% 2 6% 4 4 4 3 6% 7% 48%	1906
	11th to 20th	Night	9% 6% 2 6% 3 4 4 3 6% 7% 49%	1875
	21st to end	Night	11% 4 2 5% 4 3 4 4 5% 8% 52%	1900
May	1st to 10th	Night	8% 6% 3 8% 5% 5% 5% 4 6% 8% 40%	3112
	11th to 20th	Night	18% 6% 3 8% 5% 4 5% 3 5% 7% 36%	2812
	21st to end	Night	7% 4 2 5% 4 4 5% 4 8% 10% 46%	3079
June	1st to 10th	Night	9% 5% 2 6% 5% 6% 5% 5% 8% 10% 39%	1530
	11th to 20th	Night	8% 6% 3 7% 5% 4 5% 4 7% 11% 39%	1520
	21st to end	Night	8% 5% 3 7% 5% 5% 6% 6% 8% 10% 37%	1640
July	1st to 10th	Night	7% 5% 3 7% 5% 5% 5% 5% 7% 13% 36%	2840
	11th to 20th	Night	10% 7% 3 7% 6% 5% 6% 6% 8% 12% 30%	2840
	21st to end	Night	13% 9% 3 9% 6% 5% 6% 4 7% 9% 28%	3087
August	1st to 10th	Night	17% 10% 4 9% 5% 5% 6% 4 6% 9% 25%	2825
	11th to 20th	Night	9% 7% 3 9% 6% 5% 7% 5% 6% 10% 33%	3037
	21st to end	Night	7% 4 2 6% 5% 5% 6% 5% 8% 9% 43%	3476
September	1st to 10th	Night	11% 5% 2 5% 4 5% 5% 4 6% 10% 43%	1900
	11th to 20th	Night	14% 6% 2 7% 5% 4 5% 4 6% 8% 40%	1900
	21st to end	Night	17% 7% 3 7% 6% 5% 5% 3 5% 7% 35%	2194
October	1st to 10th	Night	13% 7% 2 5% 3 3 3 4 5% 6% 49%	2280
	11th to 20th	Night	13% 5% 2 4 3 4 3 2 4 6% 54%	2280
	21st to end	Night	11% 4 2 5% 3 3 4 3 4 5% 56%	2508
November	1st to 10th	Night	13% 6% 2 5% 3 3 3 2 4 6% 52%	2341
	11th to 20th	Night	15% 7% 2 5% 3 3 3 3 4 5% 49%	2475
	21st to end	Night	13% 5% 2 5% 3 3 3 3 4 7% 51%	2670
December	1st to 10th	Night	16% 8% 2 7% 4 4 3 3 5% 7% 42%	2686
	11th to 20th	Night	17% 6% 2 5% 3 3 3 3 3 5% 48%	3285
	21st to end	Night	14% 7% 2 6% 3 3 3 3 5% 6% 47%	4628

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	36% 3 7% 24% 24% 5%	2837
	11th to 20th	Day	36% 4 5% 17% 29% 9%	2840
	21st to end	Day	45% 5% 7% 15% 19% 10%	3124
February	1st to 10th	Day	42% 4 10% 20% 19% 5%	1710
	11th to 20th	Day	42% 3 7% 17% 24% 6%	1778
	21st to end	Day	44% 5% 9% 18% 17% 7%	1621
March	1st to 10th	Day	49% 5% 10% 15% 14% 7%	3435
	11th to 20th	Day	31% 5% 8% 17% 25% 14%	3480
	21st to end	Day	41% 4 6% 23% 19% 6%	3815
April	1st to 10th	Day	33% 5% 8% 22% 24% 8%	2272
	11th to 20th	Day	31% 5% 11% 23% 22% 8%	2254
	21st to end	Day	34% 7% 11% 23% 20% 4	2280
May	1st to 10th	Day	40% 10% 19% 19% 11% 2	3846
	11th to 20th	Day	48% 8% 11% 21% 12% 1	4085
	21st to end	Day	32% 10% 15% 25% 16% 2	4489
June	1st to 10th	Day	42% 9% 15% 19% 14% 1	2641
	11th to 20th	Day	36% 9% 16% 22% 14% 2	2660
	21st to end	Day	40% 11% 16% 20% 11% 2	2530
July	1st to 10th	Day	39% 10% 20% 20% 10% 1	4055
	11th to 20th	Day	51% 10% 21% 13% 4 1	4051
	21st to end	Day	50% 10% 15% 16% 9%	4324
August	1st to 10th	Day	60% 8% 17% 10% 4	4091
	11th to 20th	Day	43% 8% 13% 24% 11% 1	3781
	21st to end	Day	35% 7% 15% 28% 14% 1	4180
September	1st to 10th	Day	41% 11% 13% 16% 15% 4	2280
	11th to 20th	Day	45% 5% 11% 17% 18% 4	2277
	21st to end	Day	49% 6% 9% 18% 15% 3	1982
October	1st to 10th	Day	36% 5% 7% 24% 22% 6%	3160
	11th to 20th	Day	22% 3 5% 20% 23% 26%	3140
	21st to end	Day	27% 3 4 25% 29% 12%	3428
November	1st to 10th	Day	36% 3 7% 19% 26% 7%	1957
	11th to 20th	Day	37% 4 7% 20% 25% 7%	1920
	21st to end	Day	33% 4 7% 25% 25% 6%	1725
December	1st to 10th	Day	44% 5% 10% 21% 14% 5%	1528
	11th to 20th	Day	36% 3 6% 25% 21% 9%	1906
	21st to end	Day	42% 4 9% 21% 22% 2	3010
January	1st to 10th	Night	39% 4 8% 20% 25% 5%	4109
	11th to 20th	Night	43% 5% 6% 17% 23% 6%	4120
	21st to end	Night	42% 5% 7% 17% 21% 8%	4532
February	1st to 10th	Night	42% 4 8% 20% 20% 7%	2470
	11th to 20th	Night	44% 4 9% 16% 19% 7%	2296
	21st to end	Night	41% 5% 9% 18% 20% 8%	1829
March	1st to 10th	Night	55% 5% 7% 14% 14% 5%	3418
	11th to 20th	Night	34% 6% 8% 11% 24% 16%	3480
	21st to end	Night	35% 6% 9% 24% 19% 6%	3817
April	1st to 10th	Night	35% 6% 12% 17% 23% 8%	1906
	11th to 20th	Night	33% 7% 11% 22% 20% 7%	1875
	21st to end	Night	30% 6% 14% 28% 17% 4	1900
May	1st to 10th	Night	38% 10% 18% 22% 10% 2	3142
	11th to 20th	Night	47% 8% 10% 20% 15% 1	2813
	21st to end	Night	29% 10% 19% 25% 15% 1	3087
June	1st to 10th	Night	37% 11% 18% 21% 12% 2	1530
	11th to 20th	Night	36% 10% 17% 25% 12% 1	1520
	21st to end	Night	38% 11% 18% 22% 11% 1	1640
July	1st to 10th	Night	37% 12% 23% 19% 8% 1	2795
	11th to 20th	Night	44% 11% 26% 14% 4 1	2786
	21st to end	Night	51% 11% 14% 16% 8% 1	2988
August	1st to 10th	Night	55% 8% 22% 13% 3	2814
	11th to 20th	Night	45% 8% 19% 20% 7% 1	3066
	21st to end	Night	34% 8% 14% 31% 11% 2	3476
September	1st to 10th	Night	36% 10% 18% 17% 16% 4	1900
	11th to 20th	Night	41% 9% 12% 19% 16% 3	1900
	21st to end	Night	48% 6% 10% 19% 14% 2	2194
October	1st to 10th	Night	39% 5% 6% 20% 25% 5%	3800
	11th to 20th	Night	22% 3 6% 17% 24% 28%	3779
	21st to end	Night	24% 3 6% 28% 27% 12%	4120
November	1st to 10th	Night	35% 4 6% 21% 26% 7%	2341
	11th to 20th	Night	38% 4 8% 15% 26% 9%	2475
	21st to end	Night	34% 4 8% 23% 26% 7%	2670
December	1st to 10th	Night	43% 5% 12% 17% 18% 5%	2686
	11th to 20th	Night	39% 4 8% 19% 24% 7%	3288
	21st to end	Night	38% 4 8% 23% 24% 3	4628

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% 24% 40% 11% 6%	270
	11th to 20th	Day	17% 24% 32% 24% 3	270
	21st to end	Day	24% 18% 35% 18% 5%	297
February	1st to 10th	Day	19% 19% 39% 19% 3 1	270
	11th to 20th	Day	30% 15% 35% 17% 3	377
	21st to end	Day	21% 14% 37% 22% 6%	382
March	1st to 10th	Day	19% 16% 34% 23% 8% 1	460
	11th to 20th	Day	21% 19% 36% 17% 7% 1	460
	21st to end	Day	18% 16% 31% 24% 9% 2	506
April	1st to 10th	Day	18% 18% 29% 22% 9% 3	460
	11th to 20th	Day	13% 12% 30% 27% 13% 5%	452
	21st to end	Day	14% 10% 29% 26% 18% 3	460
May	1st to 10th	Day	15% 12% 32% 20% 15% 5%	463
	11th to 20th	Day	16% 7% 19% 32% 19% 8%	487
	21st to end	Day	14% 4 18% 29% 23% 12%	529
June	1st to 10th	Day	13% 2 19% 32% 26% 9%	490
	11th to 20th	Day	11% 4 15% 29% 23% 18%	490
	21st to end	Day	9% 2 16% 30% 26% 17%	490
July	1st to 10th	Day	10% 2 9% 29% 32% 19%	485
	11th to 20th	Day	10% 3 10% 27% 36% 15%	484
	21st to end	Day	8% 2 13% 31% 35% 11%	532
August	1st to 10th	Day	17% 3 12% 24% 27% 17%	486
	11th to 20th	Day	13% 2 15% 22% 29% 20%	479
	21st to end	Day	12% 3 10% 28% 29% 19%	539
September	1st to 10th	Day	12% 3 16% 26% 23% 19%	490
	11th to 20th	Day	18% 4 12% 28% 26% 13%	490
	21st to end	Day	20% 4 21% 24% 22% 9%	490
October	1st to 10th	Day	17% 5% 22% 23% 22% 11%	490
	11th to 20th	Day	12% 9% 23% 32% 18% 6%	490
	21st to end	Day	12% 8% 24% 31% 20% 5%	539
November	1st to 10th	Day	18% 8% 27% 29% 14% 4	495
	11th to 20th	Day	18% 10% 31% 30% 9% 2	460
	21st to end	Day	15% 13% 27% 26% 16% 2	325
December	1st to 10th	Day	20% 11% 39% 19% 10% 1	182
	11th to 20th	Day	17% 16% 33% 21% 11% 3	180
	21st to end	Day	17% 17% 36% 18% 10% 3	267
January	1st to 10th	Night	19% 15% 30% 29% 6%	760
	11th to 20th	Night	17% 13% 31% 31% 7%	760
	21st to end	Night	20% 10% 38% 28% 4	836
February	1st to 10th	Night	19% 12% 33% 30% 5%	760
	11th to 20th	Night	23% 16% 37% 23% 2	743
	21st to end	Night	18% 14% 35% 29% 4	628
March	1st to 10th	Night	15% 11% 37% 30% 6%	760
	11th to 20th	Night	17% 13% 38% 25% 7% 1	760
	21st to end	Night	17% 11% 36% 30% 6%	836
April	1st to 10th	Night	14% 14% 37% 31% 5%	760
	11th to 20th	Night	12% 10% 36% 31% 11%	751
	21st to end	Night	14% 6% 34% 37% 9% 1	760
May	1st to 10th	Night	12% 9% 31% 38% 10%	755
	11th to 20th	Night	15% 5% 22% 41% 16%	561
	21st to end	Night	11% 2 13% 40% 32% 2	617
June	1st to 10th	Night	9% 2 20% 49% 20% 1	390
	11th to 20th	Night	8% 4 12% 47% 26% 3	380
	21st to end	Night	8% 2 15% 41% 32% 2	500
July	1st to 10th	Night	10% 2 9% 40% 35% 5%	555
	11th to 20th	Night	7% 2 8% 36% 41% 6%	552
	21st to end	Night	9% 1 11% 46% 31% 2	624
August	1st to 10th	Night	15% 1 8% 36% 36% 4	567
	11th to 20th	Night	13% 2 10% 35% 35% 5%	714
	21st to end	Night	13% 1 10% 33% 37% 6%	836
September	1st to 10th	Night	13% 1 13% 31% 36% 6%	760
	11th to 20th	Night	17% 1 14% 34% 30% 3	760
	21st to end	Night	22% 3 16% 34% 24% 2	760
October	1st to 10th	Night	17% 3 17% 31% 28% 4	760
	11th to 20th	Night	15% 6% 25% 33% 19% 2	760
	21st to end	Night	13% 5% 24% 36% 18% 3	836
November	1st to 10th	Night	15% 5% 23% 37% 17% 3	780
	11th to 20th	Night	19% 8% 26% 33% 12% 2	800
	21st to end	Night	16% 8% 28% 33% 13% 2	800
December	1st to 10th	Night	20% 8% 29% 36% 7%	768
	11th to 20th	Night	18% 8% 29% 35% 9%	760
	21st to end	Night	17% 12% 29% 33% 9%	836

Page generated at 2024-11-29 10:43:08. Version ac07

Copyright © 2024 Attilla Danko.