Starlight Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starlight Ridge Observatory clear sky chart from 2005-11-06 to 2024-12-09.

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	9% 6% 2 6% 4 4 4 3 5% 7% 50%	105399
	Night	9% 7% 2 6% 4 4 4 3 5% 7% 49%	103053
Transparency	Day	34% 6% 13% 26% 17% 4	105147
	Night	34% 6% 13% 26% 18% 3	102897
Seeing	Day	12% 10% 33% 30% 13% 2	15980
	Night	12% 10% 38% 33% 8%	25951

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	5% 12% 5% 10% 6% 4 4 3 4 5% 42%	2538
	11th to 20th	Day	5% 10% 3 9% 5% 6% 8% 5% 6% 6% 37%	2540
	21st to end	Day	5% 7% 3 10% 5% 4 4 3 5% 6% 49%	2856
February	1st to 10th	Day	9% 11% 3 8% 6% 4 5% 4 5% 7% 39%	1733
	11th to 20th	Day	6% 9% 3 9% 4 4 3 3 5% 6% 46%	1849
	21st to end	Day	8% 9% 3 7% 4 4 4 3 4 5% 49%	1570
March	1st to 10th	Day	7% 9% 2 6% 3 3 4 3 4 6% 53%	3130
	11th to 20th	Day	7% 9% 3 4 3 3 3 3 5% 6% 54%	3444
	21st to end	Day	18% 11% 3 7% 4 4 3 3 5% 6% 35%	3835
April	1st to 10th	Day	14% 7% 3 5% 4 4 4 3 6% 7% 44%	2280
	11th to 20th	Day	16% 9% 3 6% 5% 3 4 3 4 6% 41%	2341
	21st to end	Day	16% 7% 2 5% 4 4 4 3 6% 7% 42%	2470
May	1st to 10th	Day	13% 7% 3 7% 5% 4 5% 3 6% 7% 40%	4120
	11th to 20th	Day	10% 6% 2 5% 4 4 4 3 6% 7% 48%	4082
	21st to end	Day	16% 6% 2 6% 4 3 4 3 5% 7% 45%	4716
June	1st to 10th	Day	10% 4 2 5% 3 4 4 4 6% 8% 51%	2660
	11th to 20th	Day	11% 4 2 5% 3 4 4 3 6% 8% 50%	2660
	21st to end	Day	5% 4 1 5% 4 5% 3 4 7% 8% 55%	2660
July	1st to 10th	Day	9% 4 2 6% 4 4 4 4 6% 8% 48%	4430
	11th to 20th	Day	5% 3 1 5% 4 4 4 4 6% 8% 55%	4430
	21st to end	Day	3 3 1 3 3 4 5% 4 7% 10% 56%	4742
August	1st to 10th	Day	6% 5% 2 5% 4 5% 5% 5% 6% 9% 49%	4103
	11th to 20th	Day	12% 6% 3 6% 3 4 4 4 5% 7% 45%	4041
	21st to end	Day	6% 3 2 4 3 3 4 3 5% 8% 60%	4318
September	1st to 10th	Day	9% 4 2 4 3 2 3 3 4 7% 60%	2233
	11th to 20th	Day	6% 3 2 5% 3 3 4 3 5% 7% 61%	2090
	21st to end	Day	10% 4 1 4 3 2 3 3 4 6% 59%	2090
October	1st to 10th	Day	8% 4 1 2 2 1 2 2 3 4 72%	3480
	11th to 20th	Day	8% 5% 1 4 3 2 3 3 4 8% 60%	3073
	21st to end	Day	8% 6% 3 5% 4 5% 4 4 6% 6% 48%	3091
November	1st to 10th	Day	7% 6% 2 6% 3 4 3 4 5% 7% 52%	1763
	11th to 20th	Day	5% 8% 2 7% 4 3 3 3 4 5% 55%	1800
	21st to end	Day	6% 10% 3 5% 4 3 4 3 5% 8% 49%	1800
December	1st to 10th	Day	6% 9% 3 7% 5% 4 4 2 7% 6% 47%	1711
	11th to 20th	Day	5% 7% 3 7% 4 4 4 3 6% 8% 48%	1926
	21st to end	Day	14% 14% 4 10% 4 3 3 3 5% 5% 37%	2794
January	1st to 10th	Night	5% 11% 4 11% 8% 4 3 3 5% 7% 38%	4417
	11th to 20th	Night	4 10% 4 9% 5% 5% 8% 5% 6% 6% 39%	4430
	21st to end	Night	4 7% 4 10% 6% 4 4 4 6% 7% 46%	4809
February	1st to 10th	Night	10% 10% 4 7% 5% 5% 4 4 5% 6% 40%	2465
	11th to 20th	Night	6% 9% 3 8% 5% 4 5% 4 6% 7% 44%	2218
	21st to end	Night	7% 7% 2 6% 4 4 5% 3 6% 6% 49%	1884
March	1st to 10th	Night	8% 11% 2 6% 4 4 4 3 4 5% 49%	3734
	11th to 20th	Night	9% 6% 2 5% 4 4 3 4 5% 8% 52%	3517
	21st to end	Night	17% 9% 3 9% 4 5% 4 4 5% 8% 32%	3792
April	1st to 10th	Night	13% 7% 3 6% 4 4 4 3 5% 8% 43%	1900
	11th to 20th	Night	14% 7% 2 6% 4 3 4 4 5% 7% 44%	1785
	21st to end	Night	15% 7% 3 6% 5% 3 4 4 6% 7% 42%	1710
May	1st to 10th	Night	16% 6% 2 4 4 4 3 4 5% 6% 46%	2850
	11th to 20th	Night	9% 5% 2 4 4 3 4 4 6% 8% 52%	2823
	21st to end	Night	14% 5% 2 6% 4 3 4 4 6% 8% 44%	2867
June	1st to 10th	Night	9% 4 1 4 2 3 4 3 5% 10% 54%	1520
	11th to 20th	Night	12% 4 3 4 4 3 4 3 5% 7% 50%	1520
	21st to end	Night	4 3 1 4 4 5% 5% 4 8% 9% 53%	1520
July	1st to 10th	Night	8% 4 1 4 3 3 3 4 6% 9% 56%	2540
	11th to 20th	Night	5% 4 2 5% 4 4 5% 4 6% 7% 54%	2540
	21st to end	Night	3 3 1 5% 4 5% 4 4 5% 8% 58%	2817
August	1st to 10th	Night	5% 4 1 6% 5% 5% 5% 5% 8% 9% 46%	2836
	11th to 20th	Night	10% 5% 2 5% 4 5% 5% 3 6% 8% 47%	2798
	21st to end	Night	5% 4 2 5% 3 3 3 3 5% 8% 59%	3346
September	1st to 10th	Night	9% 3 1 4 3 3 3 3 5% 5% 60%	1947
	11th to 20th	Night	7% 3 1 3 3 2 3 2 5% 7% 63%	2090
	21st to end	Night	10% 4 1 3 3 2 3 2 4 6% 62%	2090
October	1st to 10th	Night	9% 4 1 2 2 2 2 2 3 4 70%	3480
	11th to 20th	Night	10% 4 1 3 2 2 2 2 4 7% 63%	3813
	21st to end	Night	8% 6% 2 6% 4 4 3 3 5% 8% 51%	4467
November	1st to 10th	Night	8% 6% 2 5% 3 4 3 3 6% 7% 54%	2535
	11th to 20th	Night	6% 7% 2 6% 4 3 4 3 5% 7% 53%	2600
	21st to end	Night	6% 8% 3 6% 4 3 4 4 5% 7% 51%	2600
December	1st to 10th	Night	6% 7% 3 7% 5% 4 3 4 5% 6% 51%	2649
	11th to 20th	Night	5% 8% 3 6% 4 3 3 3 5% 8% 51%	3271
	21st to end	Night	17% 12% 2 10% 3 3 3 3 4 5% 37%	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	45% 4 10% 27% 14%	2539
	11th to 20th	Day	46% 7% 16% 18% 10% 2	2540
	21st to end	Day	37% 5% 19% 22% 15% 2	2856
February	1st to 10th	Day	45% 5% 15% 20% 13% 2	1733
	11th to 20th	Day	40% 5% 13% 24% 13% 5%	1859
	21st to end	Day	39% 4 13% 24% 15% 5%	1570
March	1st to 10th	Day	32% 4 8% 27% 25% 4	3130
	11th to 20th	Day	31% 5% 12% 30% 21% 2	3444
	21st to end	Day	50% 6% 17% 20% 5% 1	3835
April	1st to 10th	Day	38% 5% 15% 26% 14% 2	2280
	11th to 20th	Day	44% 5% 12% 22% 15% 2	2344
	21st to end	Day	40% 5% 14% 27% 13%	2470
May	1st to 10th	Day	41% 8% 12% 21% 17% 2	4120
	11th to 20th	Day	35% 7% 12% 29% 16% 2	4086
	21st to end	Day	39% 6% 12% 29% 12% 2	4716
June	1st to 10th	Day	29% 8% 18% 30% 13% 2	2660
	11th to 20th	Day	32% 6% 15% 27% 17% 3	2660
	21st to end	Day	25% 7% 14% 32% 19% 3	2660
July	1st to 10th	Day	32% 6% 14% 27% 18% 2	4361
	11th to 20th	Day	26% 6% 12% 32% 19% 5%	4355
	21st to end	Day	20% 9% 14% 26% 23% 8%	4593
August	1st to 10th	Day	31% 7% 15% 24% 18% 5%	4090
	11th to 20th	Day	38% 7% 12% 27% 15% 1	4080
	21st to end	Day	23% 6% 19% 24% 22% 6%	4317
September	1st to 10th	Day	25% 4 12% 27% 23% 8%	2233
	11th to 20th	Day	24% 5% 12% 32% 23% 4	2090
	21st to end	Day	27% 3 9% 31% 27% 3	2090
October	1st to 10th	Day	19% 2 7% 20% 38% 13%	3480
	11th to 20th	Day	25% 3 17% 32% 20% 4	3073
	21st to end	Day	35% 4 9% 32% 15% 5%	3091
November	1st to 10th	Day	31% 5% 13% 27% 20% 4	1763
	11th to 20th	Day	33% 3 11% 28% 19% 7%	1800
	21st to end	Day	34% 4 14% 27% 17% 4	1800
December	1st to 10th	Day	38% 4 13% 28% 16% 2	1711
	11th to 20th	Day	33% 5% 17% 30% 15% 1	1924
	21st to end	Day	50% 5% 8% 27% 9% 1	2794
January	1st to 10th	Night	47% 4 11% 25% 13% 1	4417
	11th to 20th	Night	43% 6% 14% 25% 11% 1	4430
	21st to end	Night	37% 7% 17% 24% 14% 1	4809
February	1st to 10th	Night	44% 5% 15% 22% 12% 2	2465
	11th to 20th	Night	39% 6% 12% 25% 14% 4	2218
	21st to end	Night	36% 4 13% 27% 15% 6%	1884
March	1st to 10th	Night	36% 5% 10% 22% 25% 2	3734
	11th to 20th	Night	30% 5% 11% 31% 20% 1	3517
	21st to end	Night	49% 8% 14% 21% 7% 1	3792
April	1st to 10th	Night	38% 6% 15% 22% 16% 3	1900
	11th to 20th	Night	40% 6% 11% 25% 17% 2	1785
	21st to end	Night	39% 8% 13% 25% 14% 1	1710
May	1st to 10th	Night	36% 7% 13% 24% 17% 3	2850
	11th to 20th	Night	29% 8% 13% 32% 14% 3	2824
	21st to end	Night	36% 9% 18% 23% 13% 1	2868
June	1st to 10th	Night	26% 7% 18% 30% 16% 2	1520
	11th to 20th	Night	33% 7% 13% 26% 16% 4	1520
	21st to end	Night	24% 9% 16% 31% 17% 3	1520
July	1st to 10th	Night	25% 6% 21% 29% 16% 3	2500
	11th to 20th	Night	27% 6% 13% 31% 18% 5%	2492
	21st to end	Night	23% 7% 15% 25% 25% 5%	2729
August	1st to 10th	Night	30% 8% 19% 26% 12% 5%	2826
	11th to 20th	Night	35% 6% 15% 28% 14% 2	2825
	21st to end	Night	24% 7% 15% 23% 23% 8%	3346
September	1st to 10th	Night	26% 5% 11% 26% 26% 7%	1947
	11th to 20th	Night	21% 4 14% 32% 25% 4	2090
	21st to end	Night	25% 5% 7% 30% 29% 4	2090
October	1st to 10th	Night	20% 3 6% 17% 48% 5%	3480
	11th to 20th	Night	23% 3 12% 30% 25% 7%	3813
	21st to end	Night	32% 4 14% 26% 22% 3	4467
November	1st to 10th	Night	30% 5% 13% 26% 21% 6%	2535
	11th to 20th	Night	30% 4 12% 26% 22% 6%	2600
	21st to end	Night	32% 4 12% 29% 20% 3	2600
December	1st to 10th	Night	33% 5% 16% 28% 16% 3	2649
	11th to 20th	Night	32% 4 13% 36% 14% 1	3272
	21st to end	Night	50% 4 9% 25% 10% 1	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	10% 15% 33% 26% 14% 3	270
	11th to 20th	Day	11% 18% 36% 23% 10% 1	270
	21st to end	Day	16% 11% 38% 21% 9% 5%	297
February	1st to 10th	Day	12% 13% 46% 24% 4	270
	11th to 20th	Day	13% 13% 43% 21% 9% 1	270
	21st to end	Day	16% 15% 45% 20% 4	225
March	1st to 10th	Day	13% 12% 35% 28% 9% 2	270
	11th to 20th	Day	13% 11% 36% 29% 10% 1	270
	21st to end	Day	22% 14% 31% 21% 10% 2	306
April	1st to 10th	Day	18% 17% 41% 20% 3 1	460
	11th to 20th	Day	23% 17% 33% 22% 4	542
	21st to end	Day	19% 15% 31% 26% 7% 2	650
May	1st to 10th	Day	17% 12% 32% 29% 8% 1	653
	11th to 20th	Day	20% 11% 28% 26% 13% 2	675
	21st to end	Day	17% 9% 31% 30% 11% 1	734
June	1st to 10th	Day	8% 8% 30% 32% 16% 6%	680
	11th to 20th	Day	11% 8% 35% 30% 14% 2	680
	21st to end	Day	7% 7% 30% 36% 17% 3	680
July	1st to 10th	Day	7% 3 27% 38% 20% 5%	671
	11th to 20th	Day	6% 4 29% 41% 18% 2	668
	21st to end	Day	5% 3 26% 45% 18% 3	739
August	1st to 10th	Day	7% 3 23% 43% 20% 4	676
	11th to 20th	Day	10% 4 28% 38% 18% 3	665
	21st to end	Day	5% 3 30% 37% 22% 3	625
September	1st to 10th	Day	6% 4 29% 40% 17% 4	443
	11th to 20th	Day	7% 5% 32% 29% 23% 4	300
	21st to end	Day	15% 11% 28% 28% 15% 2	300
October	1st to 10th	Day	18% 8% 23% 30% 17% 5%	300
	11th to 20th	Day	12% 16% 41% 23% 6% 2	300
	21st to end	Day	15% 16% 32% 25% 9% 2	330
November	1st to 10th	Day	16% 9% 37% 26% 8% 4	300
	11th to 20th	Day	15% 12% 44% 20% 9%	300
	21st to end	Day	14% 14% 39% 22% 10% 1	300
December	1st to 10th	Day	10% 15% 44% 22% 8% 2	294
	11th to 20th	Day	11% 13% 42% 23% 9% 1	270
	21st to end	Day	18% 17% 39% 19% 7% 1	297
January	1st to 10th	Night	10% 14% 43% 26% 6%	950
	11th to 20th	Night	9% 18% 41% 27% 5%	950
	21st to end	Night	10% 12% 43% 27% 8%	1045
February	1st to 10th	Night	15% 12% 41% 26% 5%	945
	11th to 20th	Night	9% 13% 46% 26% 5%	744
	21st to end	Night	11% 10% 43% 29% 5% 1	628
March	1st to 10th	Night	11% 12% 40% 33% 4	760
	11th to 20th	Night	15% 9% 41% 28% 6% 1	594
	21st to end	Night	18% 10% 38% 26% 8%	627
April	1st to 10th	Night	16% 13% 42% 27% 2	570
	11th to 20th	Night	18% 12% 41% 26% 4	563
	21st to end	Night	18% 10% 34% 30% 8% 1	570
May	1st to 10th	Night	15% 9% 36% 31% 8%	570
	11th to 20th	Night	19% 9% 31% 30% 10% 1	561
	21st to end	Night	16% 9% 36% 34% 6%	617
June	1st to 10th	Night	9% 5% 31% 39% 14% 2	570
	11th to 20th	Night	12% 5% 37% 38% 8%	570
	21st to end	Night	6% 4 31% 48% 11%	570
July	1st to 10th	Night	7% 3 30% 44% 16%	555
	11th to 20th	Night	5% 3 31% 49% 12%	552
	21st to end	Night	5% 4 29% 51% 12%	624
August	1st to 10th	Night	6% 2 26% 50% 15% 1	567
	11th to 20th	Night	9% 3 30% 45% 14%	564
	21st to end	Night	7% 4 32% 41% 15% 1	627
September	1st to 10th	Night	10% 5% 31% 43% 11%	570
	11th to 20th	Night	8% 5% 33% 41% 12% 1	570
	21st to end	Night	11% 9% 35% 32% 11% 1	570
October	1st to 10th	Night	18% 8% 31% 31% 12%	570
	11th to 20th	Night	13% 10% 37% 31% 8% 1	770
	21st to end	Night	14% 13% 35% 29% 8%	1045
November	1st to 10th	Night	11% 9% 41% 31% 7% 1	975
	11th to 20th	Night	10% 14% 40% 29% 7%	1000
	21st to end	Night	10% 10% 42% 30% 7%	1000
December	1st to 10th	Night	9% 14% 45% 26% 6%	993
	11th to 20th	Night	11% 10% 42% 31% 6%	950
	21st to end	Night	17% 13% 36% 27% 6%	1045

Page generated at 2024-12-06 02:54:48. Version ac07

Copyright © 2024 Attilla Danko.