Starlight Hills Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starlight Hills Observatory clear sky chart from 2005-11-06 to 2024-10-25.

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	4 5% 2 5% 4 4 5% 4 6% 8% 54%	101178
	Night	3 5% 2 5% 3 3 4 4 6% 8% 58%	97870
Transparency	Day	24% 7% 12% 23% 23% 11%	100923
	Night	23% 7% 13% 25% 24% 9%	97715
Seeing	Day	7% 11% 29% 29% 18% 6%	15505
	Night	6% 6% 31% 39% 16% 2	25481

By Month

Percentage Cloud Cover SW (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	1 4 1 4 3 3 3 4 6% 10% 62%	2538
	11th to 20th	Day	1 3 1 5% 3 4 5% 5% 6% 8% 60%	2640
	21st to end	Day	1 5% 2 6% 4 4 4 3 5% 6% 60%	3146
February	1st to 10th	Day	1 6% 3 5% 5% 3 4 3 5% 7% 58%	1729
	11th to 20th	Day	1 3 2 6% 4 4 4 4 6% 8% 58%	1849
	21st to end	Day	1 5% 2 8% 5% 3 4 3 5% 6% 57%	1570
March	1st to 10th	Day	1 5% 2 6% 4 3 3 4 5% 7% 59%	3130
	11th to 20th	Day	3 11% 3 7% 4 3 4 3 6% 8% 48%	3417
	21st to end	Day	2 6% 3 5% 4 4 4 4 6% 8% 54%	4087
April	1st to 10th	Day	3 6% 2 5% 3 4 4 5% 6% 9% 55%	2280
	11th to 20th	Day	6% 6% 3 6% 4 4 4 5% 6% 8% 48%	2251
	21st to end	Day	6% 8% 2 5% 3 4 4 4 6% 9% 49%	2280
May	1st to 10th	Day	7% 9% 2 5% 4 4 5% 4 6% 8% 46%	3990
	11th to 20th	Day	7% 7% 2 6% 4 5% 5% 5% 7% 9% 44%	4281
	21st to end	Day	4 4 1 5% 4 4 5% 5% 9% 9% 49%	4825
June	1st to 10th	Day	5% 4 2 4 4 4 5% 6% 8% 9% 47%	2660
	11th to 20th	Day	5% 3 1 4 4 4 5% 5% 8% 9% 53%	2660
	21st to end	Day	3 3 2 5% 5% 5% 6% 6% 9% 9% 48%	2660
July	1st to 10th	Day	4 4 2 5% 3 4 5% 5% 7% 9% 52%	4430
	11th to 20th	Day	3 4 1 6% 5% 6% 6% 6% 8% 10% 45%	4430
	21st to end	Day	5% 4 2 5% 5% 5% 5% 5% 7% 8% 50%	4690
August	1st to 10th	Day	9% 5% 2 7% 6% 6% 6% 6% 9% 9% 37%	4014
	11th to 20th	Day	4 4 2 5% 5% 5% 7% 6% 7% 9% 48%	3726
	21st to end	Day	5% 4 2 5% 4 5% 6% 5% 8% 9% 48%	4180
September	1st to 10th	Day	5% 3 2 4 3 4 5% 4 7% 7% 56%	2280
	11th to 20th	Day	6% 3 1 4 3 3 4 4 6% 7% 59%	2242
	21st to end	Day	5% 4 1 4 2 3 3 3 4 6% 65%	2090
October	1st to 10th	Day	5% 4 2 4 2 2 3 3 5% 7% 64%	1948
	11th to 20th	Day	2 3 1 4 2 3 3 3 3 5% 69%	1900
	21st to end	Day	5% 4 1 4 2 2 2 3 4 6% 67%	1958
November	1st to 10th	Day	1 3 1 3 3 2 3 3 6% 7% 68%	1673
	11th to 20th	Day	1 4 1 3 3 2 3 3 4 7% 68%	1710
	21st to end	Day	1 4 2 5% 4 3 3 3 5% 7% 63%	1674
December	1st to 10th	Day	1 3 2 5% 4 3 3 3 5% 8% 62%	1520
	11th to 20th	Day	1 5% 2 5% 4 3 4 4 4 8% 61%	1926
	21st to end	Day	1 5% 2 5% 4 3 4 4 4 7% 61%	2794
January	1st to 10th	Night	1 5% 3 7% 4 3 3 3 6% 8% 58%	4417
	11th to 20th	Night	1 2 1 3 4 4 4 3 5% 7% 65%	4359
	21st to end	Night	1 4 2 5% 4 4 4 3 4 6% 62%	4521
February	1st to 10th	Night	2 5% 2 7% 4 4 3 3 5% 7% 58%	2450
	11th to 20th	Night	1 6% 3 6% 4 3 4 3 6% 7% 55%	2218
	21st to end	Night	1 5% 2 6% 4 2 3 2 5% 4 66%	1884
March	1st to 10th	Night	1 5% 2 5% 3 3 3 3 5% 7% 62%	3734
	11th to 20th	Night	6% 10% 2 4 4 3 3 3 5% 5% 54%	3557
	21st to end	Night	2 6% 2 5% 3 3 4 3 5% 8% 57%	3556
April	1st to 10th	Night	4 5% 1 4 3 3 4 3 5% 8% 60%	1900
	11th to 20th	Night	7% 9% 2 5% 2 4 3 4 5% 6% 53%	1877
	21st to end	Night	7% 7% 2 5% 3 4 3 3 5% 8% 53%	1900
May	1st to 10th	Night	8% 6% 2 4 3 3 4 3 5% 7% 55%	2978
	11th to 20th	Night	7% 8% 2 4 3 4 4 4 6% 9% 49%	2620
	21st to end	Night	7% 5% 1 4 3 4 4 4 5% 7% 56%	2762
June	1st to 10th	Night	5% 4 2 4 2 3 3 4 7% 10% 57%	1520
	11th to 20th	Night	4 3 1 3 3 3 3 3 6% 9% 63%	1520
	21st to end	Night	4 4 1 4 4 3 5% 5% 8% 8% 52%	1520
July	1st to 10th	Night	5% 4 1 5% 4 5% 5% 4 5% 7% 55%	2540
	11th to 20th	Night	3 4 1 4 4 4 5% 5% 9% 11% 50%	2540
	21st to end	Night	4 4 1 4 3 3 5% 4 7% 9% 56%	2870
August	1st to 10th	Night	9% 7% 2 5% 5% 5% 7% 5% 9% 10% 36%	2925
	11th to 20th	Night	4 4 1 6% 4 5% 5% 5% 8% 10% 48%	3113
	21st to end	Night	3 3 1 5% 4 5% 6% 6% 9% 11% 47%	3487
September	1st to 10th	Night	4 4 1 5% 4 4 6% 4 7% 8% 53%	1900
	11th to 20th	Night	6% 4 1 3 2 3 3 3 4 7% 63%	1938
	21st to end	Night	5% 4 1 4 3 3 3 3 4 6% 65%	2090
October	1st to 10th	Night	7% 5% 1 3 3 2 3 3 4 7% 62%	2229
	11th to 20th	Night	3 4 1 3 3 2 3 3 4 6% 70%	2280
	21st to end	Night	4 4 2 4 3 3 3 3 3 6% 66%	2483
November	1st to 10th	Night	1 3 1 3 2 3 3 2 5% 8% 67%	2405
	11th to 20th	Night	1 3 2 3 3 2 3 3 5% 6% 70%	2470
	21st to end	Night	2 4 2 5% 3 3 2 3 6% 6% 64%	2503
December	1st to 10th	Night	1 3 2 6% 4 3 3 2 5% 7% 64%	2660
	11th to 20th	Night	1 4 2 5% 3 3 4 4 6% 8% 59%	3271
	21st to end	Night	2 5% 2 5% 3 3 4 3 5% 7% 60%	4873

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	17% 5% 11% 33% 25% 8%	2539
	11th to 20th	Day	20% 6% 13% 29% 24% 8%	2640
	21st to end	Day	24% 5% 11% 28% 26% 6%	3146
February	1st to 10th	Day	24% 5% 12% 26% 23% 10%	1729
	11th to 20th	Day	21% 7% 8% 26% 29% 8%	1859
	21st to end	Day	25% 5% 7% 22% 24% 17%	1570
March	1st to 10th	Day	20% 6% 10% 19% 32% 14%	3130
	11th to 20th	Day	30% 8% 13% 30% 17% 3	3417
	21st to end	Day	23% 8% 13% 30% 23% 5%	4087
April	1st to 10th	Day	23% 7% 13% 24% 23% 10%	2280
	11th to 20th	Day	30% 7% 13% 23% 18% 10%	2254
	21st to end	Day	30% 7% 14% 25% 20% 4	2280
May	1st to 10th	Day	29% 8% 13% 25% 14% 12%	3990
	11th to 20th	Day	31% 10% 15% 21% 20% 3	4285
	21st to end	Day	21% 12% 16% 22% 20% 10%	4825
June	1st to 10th	Day	26% 10% 16% 22% 17% 10%	2660
	11th to 20th	Day	21% 8% 12% 17% 24% 17%	2660
	21st to end	Day	26% 9% 12% 19% 22% 11%	2660
July	1st to 10th	Day	24% 9% 11% 16% 27% 14%	4361
	11th to 20th	Day	27% 9% 13% 21% 20% 10%	4355
	21st to end	Day	26% 8% 13% 17% 19% 16%	4542
August	1st to 10th	Day	37% 9% 17% 22% 10% 4	4000
	11th to 20th	Day	26% 11% 13% 18% 19% 14%	3762
	21st to end	Day	25% 8% 14% 20% 26% 6%	4179
September	1st to 10th	Day	23% 7% 10% 22% 24% 14%	2280
	11th to 20th	Day	21% 7% 9% 17% 29% 17%	2242
	21st to end	Day	20% 5% 8% 20% 33% 14%	2090
October	1st to 10th	Day	21% 6% 11% 21% 30% 12%	1948
	11th to 20th	Day	17% 4 8% 21% 33% 17%	1900
	21st to end	Day	20% 3 8% 27% 27% 16%	1958
November	1st to 10th	Day	15% 4 10% 24% 28% 19%	1673
	11th to 20th	Day	15% 5% 6% 31% 33% 10%	1710
	21st to end	Day	20% 5% 7% 22% 29% 17%	1674
December	1st to 10th	Day	20% 7% 11% 28% 26% 8%	1520
	11th to 20th	Day	23% 5% 8% 24% 30% 9%	1924
	21st to end	Day	21% 6% 12% 26% 24% 12%	2794
January	1st to 10th	Night	24% 5% 9% 30% 28% 5%	4417
	11th to 20th	Night	15% 7% 13% 29% 26% 10%	4359
	21st to end	Night	22% 7% 12% 32% 22% 5%	4521
February	1st to 10th	Night	24% 5% 9% 28% 24% 9%	2450
	11th to 20th	Night	26% 6% 9% 29% 22% 8%	2218
	21st to end	Night	20% 5% 7% 26% 27% 16%	1884
March	1st to 10th	Night	20% 6% 9% 20% 35% 11%	3734
	11th to 20th	Night	28% 8% 13% 24% 23% 4	3557
	21st to end	Night	22% 8% 14% 27% 25% 4	3556
April	1st to 10th	Night	22% 6% 13% 23% 25% 11%	1900
	11th to 20th	Night	29% 7% 12% 25% 19% 8%	1877
	21st to end	Night	29% 7% 14% 26% 18% 6%	1900
May	1st to 10th	Night	27% 8% 14% 26% 16% 10%	2978
	11th to 20th	Night	29% 11% 17% 25% 10% 8%	2621
	21st to end	Night	23% 10% 17% 23% 20% 7%	2762
June	1st to 10th	Night	22% 7% 22% 24% 15% 10%	1520
	11th to 20th	Night	17% 8% 15% 23% 20% 18%	1520
	21st to end	Night	24% 9% 12% 22% 23% 11%	1520
July	1st to 10th	Night	26% 9% 11% 19% 28% 7%	2500
	11th to 20th	Night	22% 9% 17% 30% 16% 6%	2492
	21st to end	Night	21% 10% 16% 24% 14% 15%	2780
August	1st to 10th	Night	38% 10% 19% 19% 9% 5%	2916
	11th to 20th	Night	26% 11% 19% 20% 19% 5%	3143
	21st to end	Night	23% 11% 19% 26% 17% 4	3487
September	1st to 10th	Night	26% 7% 11% 23% 22% 11%	1900
	11th to 20th	Night	19% 5% 10% 23% 26% 16%	1938
	21st to end	Night	20% 6% 8% 23% 32% 11%	2090
October	1st to 10th	Night	22% 6% 10% 22% 26% 13%	2229
	11th to 20th	Night	16% 4 9% 23% 32% 16%	2280
	21st to end	Night	20% 4 9% 27% 27% 13%	2483
November	1st to 10th	Night	15% 5% 10% 25% 29% 17%	2405
	11th to 20th	Night	15% 4 9% 29% 32% 11%	2470
	21st to end	Night	20% 4 9% 23% 30% 13%	2503
December	1st to 10th	Night	19% 6% 13% 26% 26% 10%	2660
	11th to 20th	Night	20% 6% 10% 26% 31% 7%	3272
	21st to end	Night	23% 5% 13% 23% 25% 11%	4873

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	6% 7% 34% 37% 13% 4	270
	11th to 20th	Day	7% 11% 35% 36% 9% 2	270
	21st to end	Day	3 13% 35% 34% 13% 3	297
February	1st to 10th	Day	4 16% 47% 26% 6% 2	270
	11th to 20th	Day	3 15% 45% 26% 10% 1	270
	21st to end	Day	1 20% 47% 27% 5%	225
March	1st to 10th	Day	3 13% 39% 33% 9% 3	270
	11th to 20th	Day	10% 17% 38% 22% 10% 3	413
	21st to end	Day	11% 22% 39% 20% 6% 2	506
April	1st to 10th	Day	11% 18% 39% 23% 7% 2	460
	11th to 20th	Day	12% 25% 35% 20% 6% 2	452
	21st to end	Day	15% 17% 33% 26% 8% 2	460
May	1st to 10th	Day	14% 17% 34% 25% 8% 2	575
	11th to 20th	Day	13% 11% 28% 30% 15% 4	675
	21st to end	Day	9% 12% 30% 26% 20% 4	734
June	1st to 10th	Day	7% 10% 22% 32% 22% 7%	680
	11th to 20th	Day	6% 10% 27% 33% 18% 5%	680
	21st to end	Day	4 8% 24% 34% 23% 7%	680
July	1st to 10th	Day	6% 5% 18% 31% 30% 10%	671
	11th to 20th	Day	5% 3 14% 34% 33% 11%	668
	21st to end	Day	7% 4 14% 28% 34% 14%	676
August	1st to 10th	Day	10% 2 18% 35% 27% 8%	487
	11th to 20th	Day	5% 6% 22% 33% 22% 12%	477
	21st to end	Day	7% 3 23% 37% 21% 9%	539
September	1st to 10th	Day	8% 4 25% 32% 20% 11%	490
	11th to 20th	Day	6% 8% 29% 27% 22% 8%	452
	21st to end	Day	10% 8% 18% 26% 26% 11%	300
October	1st to 10th	Day	9% 12% 19% 25% 24% 11%	300
	11th to 20th	Day	3 9% 33% 32% 17% 6%	300
	21st to end	Day	6% 12% 33% 29% 17% 3	311
November	1st to 10th	Day	4 12% 35% 28% 15% 6%	270
	11th to 20th	Day	4 7% 39% 32% 15% 3	270
	21st to end	Day	6% 11% 35% 31% 12% 4	270
December	1st to 10th	Day	3 14% 41% 26% 14% 3	270
	11th to 20th	Day	5% 7% 41% 30% 15% 1	270
	21st to end	Day	3 14% 44% 29% 9% 2	297
January	1st to 10th	Night	3 7% 39% 36% 13% 4	950
	11th to 20th	Night	3 7% 42% 36% 9% 2	905
	21st to end	Night	2 5% 37% 43% 11% 1	836
February	1st to 10th	Night	3 6% 51% 33% 6% 1	760
	11th to 20th	Night	3 7% 49% 33% 8% 1	744
	21st to end	Night	3 9% 50% 34% 4	628
March	1st to 10th	Night	3 7% 46% 34% 9% 1	760
	11th to 20th	Night	7% 8% 33% 39% 11% 1	760
	21st to end	Night	5% 10% 43% 35% 7%	680
April	1st to 10th	Night	7% 11% 42% 35% 5%	570
	11th to 20th	Night	14% 10% 34% 34% 7% 1	563
	21st to end	Night	12% 9% 34% 35% 9% 1	570
May	1st to 10th	Night	10% 9% 31% 36% 12% 1	570
	11th to 20th	Night	12% 7% 26% 39% 14% 2	561
	21st to end	Night	11% 6% 30% 35% 16% 2	617
June	1st to 10th	Night	5% 6% 21% 45% 21% 3	570
	11th to 20th	Night	4 4 25% 51% 15% 1	570
	21st to end	Night	5% 3 18% 49% 23% 2	570
July	1st to 10th	Night	6% 3 13% 42% 33% 3	555
	11th to 20th	Night	4 2 6% 46% 37% 5%	552
	21st to end	Night	8% 2 8% 35% 42% 4	624
August	1st to 10th	Night	8% 3 8% 40% 37% 4	567
	11th to 20th	Night	7% 1 9% 49% 30% 4	564
	21st to end	Night	4 2 10% 45% 34% 4	627
September	1st to 10th	Night	6% 3 12% 46% 28% 6%	570
	11th to 20th	Night	8% 3 15% 47% 23% 4	570
	21st to end	Night	7% 3 21% 44% 21% 4	570
October	1st to 10th	Night	10% 4 24% 40% 18% 3	709
	11th to 20th	Night	5% 4 32% 39% 17% 4	760
	21st to end	Night	6% 5% 31% 37% 17% 3	859
November	1st to 10th	Night	3 4 34% 42% 15% 2	925
	11th to 20th	Night	3 6% 36% 42% 10% 2	950
	21st to end	Night	5% 6% 35% 39% 13% 2	950
December	1st to 10th	Night	2 7% 42% 38% 9% 1	950
	11th to 20th	Night	3 7% 39% 38% 12% 1	950
	21st to end	Night	5% 8% 44% 34% 8% 1	1045

Page generated at 2024-10-22 18:20:59. Version ac07

Copyright © 2024 Attilla Danko.