Antique Photons Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Antique Photons Observatory clear sky chart from 2005-11-06 to 2024-11-03.

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	12% 6% 2 5% 4 4 4 3 5% 7% 47%	101239
	Night	11% 6% 2 5% 3 3 3 3 5% 6% 52%	97848
Transparency	Day	36% 5% 12% 26% 18% 4	101052
	Night	32% 5% 11% 26% 21% 5%	97706
Seeing	Day	14% 11% 28% 27% 16% 4	15463
	Night	14% 11% 32% 31% 12% 1	25278

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	12% 11% 4 6% 3 3 4 2 5% 5% 44%	2847
	11th to 20th	Day	9% 7% 2 6% 4 3 4 4 4 6% 51%	2850
	21st to end	Day	21% 12% 2 5% 3 2 2 2 3 5% 44%	3135
February	1st to 10th	Day	16% 11% 3 6% 4 3 3 3 5% 6% 42%	1710
	11th to 20th	Day	15% 7% 2 6% 4 4 3 2 4 6% 46%	1762
	21st to end	Day	16% 7% 2 6% 5% 5% 3 3 4 5% 44%	1631
March	1st to 10th	Day	15% 8% 2 4 3 3 3 2 4 5% 52%	3436
	11th to 20th	Day	13% 5% 2 5% 3 3 3 3 5% 8% 50%	3480
	21st to end	Day	16% 9% 3 8% 5% 4 4 4 5% 6% 35%	3814
April	1st to 10th	Day	13% 6% 3 6% 4 4 4 4 6% 6% 45%	2123
	11th to 20th	Day	15% 6% 2 6% 4 4 4 3 6% 6% 44%	2254
	21st to end	Day	20% 8% 3 6% 4 3 3 3 4 6% 40%	2401
May	1st to 10th	Day	23% 8% 2 7% 4 3 3 2 4 5% 38%	4082
	11th to 20th	Day	11% 7% 2 7% 5% 4 5% 4 6% 7% 42%	4082
	21st to end	Day	16% 7% 2 7% 5% 5% 5% 4 7% 7% 35%	4477
June	1st to 10th	Day	7% 4 2 6% 5% 5% 5% 4 6% 9% 48%	2470
	11th to 20th	Day	8% 4 2 5% 5% 5% 5% 4 6% 7% 50%	2470
	21st to end	Day	5% 3 1 4 4 4 4 4 6% 9% 56%	2470
July	1st to 10th	Day	8% 5% 2 6% 4 5% 5% 5% 8% 9% 44%	4120
	11th to 20th	Day	5% 4 2 5% 3 4 4 4 6% 9% 54%	4120
	21st to end	Day	5% 4 2 5% 4 5% 5% 4 8% 11% 48%	4465
August	1st to 10th	Day	5% 3 1 4 3 3 4 4 6% 10% 57%	4104
	11th to 20th	Day	7% 4 2 5% 4 5% 5% 4 7% 9% 48%	4041
	21st to end	Day	4 3 1 5% 4 4 5% 3 6% 8% 57%	4258
September	1st to 10th	Day	10% 5% 2 4 4 4 3 3 4 6% 54%	2183
	11th to 20th	Day	11% 4 2 5% 4 4 5% 4 6% 8% 47%	2090
	21st to end	Day	8% 3 2 4 4 3 4 3 5% 7% 55%	2090
October	1st to 10th	Day	10% 4 2 4 3 3 3 4 5% 6% 57%	1942
	11th to 20th	Day	12% 5% 1 4 2 1 3 3 3 5% 62%	1900
	21st to end	Day	18% 5% 2 4 2 2 3 2 3 5% 53%	2090
November	1st to 10th	Day	11% 3 1 4 3 3 3 3 4 6% 58%	1878
	11th to 20th	Day	13% 5% 1 4 2 3 3 3 3 5% 57%	1748
	21st to end	Day	16% 8% 2 4 3 2 3 2 4 6% 51%	1710
December	1st to 10th	Day	14% 8% 2 6% 4 3 3 3 5% 5% 48%	1710
	11th to 20th	Day	14% 8% 3 8% 3 4 3 3 4 6% 44%	2161
	21st to end	Day	18% 14% 6% 8% 4 4 4 2 4 5% 31%	3135
January	1st to 10th	Night	11% 9% 4 7% 4 3 3 3 5% 5% 47%	4108
	11th to 20th	Night	9% 5% 2 5% 4 4 5% 4 5% 5% 50%	4120
	21st to end	Night	21% 8% 3 5% 2 2 2 2 4 5% 45%	4532
February	1st to 10th	Night	15% 9% 3 7% 4 3 2 3 4 6% 45%	2470
	11th to 20th	Night	14% 7% 3 6% 3 3 3 2 4 6% 50%	2319
	21st to end	Night	16% 7% 2 5% 3 3 4 3 4 3 50%	1822
March	1st to 10th	Night	15% 8% 2 4 3 3 3 3 4 5% 48%	3419
	11th to 20th	Night	11% 5% 2 5% 3 3 3 2 4 6% 56%	3480
	21st to end	Night	15% 6% 2 6% 4 3 3 3 6% 6% 46%	3817
April	1st to 10th	Night	12% 6% 2 4 3 3 3 3 5% 6% 53%	2056
	11th to 20th	Night	14% 5% 2 6% 3 3 3 3 5% 6% 50%	1875
	21st to end	Night	16% 7% 3 7% 3 3 3 2 4 5% 47%	1776
May	1st to 10th	Night	16% 7% 2 6% 4 3 4 3 4 7% 43%	2823
	11th to 20th	Night	15% 6% 3 6% 4 3 4 3 4 7% 45%	2823
	21st to end	Night	12% 5% 2 5% 4 4 4 3 7% 9% 44%	3090
June	1st to 10th	Night	6% 4 2 5% 3 3 4 4 6% 8% 54%	1710
	11th to 20th	Night	4 3 1 4 3 4 4 5% 6% 11% 56%	1710
	21st to end	Night	4 3 1 3 3 4 3 3 5% 8% 65%	1710
July	1st to 10th	Night	8% 5% 2 5% 4 3 3 4 5% 9% 52%	2850
	11th to 20th	Night	3 2 1 4 3 3 4 3 6% 9% 62%	2850
	21st to end	Night	6% 4 1 4 4 3 3 3 5% 10% 57%	3098
August	1st to 10th	Night	2 2 1 3 3 3 4 3 6% 9% 64%	2836
	11th to 20th	Night	5% 4 1 5% 4 5% 5% 5% 6% 8% 52%	2798
	21st to end	Night	3 3 1 3 3 3 4 2 6% 8% 64%	3398
September	1st to 10th	Night	7% 4 2 5% 4 3 3 3 4 7% 59%	1992
	11th to 20th	Night	9% 5% 2 4 3 4 3 3 5% 7% 53%	2090
	21st to end	Night	8% 3 1 4 4 3 4 3 4 6% 59%	2090
October	1st to 10th	Night	7% 3 1 4 3 3 3 3 4 6% 64%	2218
	11th to 20th	Night	12% 4 1 3 3 3 3 2 3 5% 60%	2280
	21st to end	Night	14% 6% 2 4 3 3 3 3 4 5% 55%	2508
November	1st to 10th	Night	11% 4 1 3 2 2 2 3 4 4 63%	2245
	11th to 20th	Night	10% 4 3 5% 3 2 3 2 4 5% 59%	2427
	21st to end	Night	15% 6% 2 3 3 2 3 3 4 5% 54%	2470
December	1st to 10th	Night	12% 6% 2 5% 4 3 4 3 4 7% 50%	2470
	11th to 20th	Night	13% 8% 2 7% 3 3 4 3 3 5% 48%	3036
	21st to end	Night	18% 9% 4 7% 4 4 3 3 4 4 40%	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	43% 3 8% 25% 19% 2	2848
	11th to 20th	Day	33% 4 16% 29% 14% 4	2850
	21st to end	Day	46% 2 9% 21% 20% 2	3135
February	1st to 10th	Day	45% 5% 10% 23% 14% 4	1710
	11th to 20th	Day	41% 4 9% 26% 17% 3	1771
	21st to end	Day	42% 3 7% 23% 17% 8%	1631
March	1st to 10th	Day	35% 4 7% 22% 22% 10%	3436
	11th to 20th	Day	33% 5% 14% 26% 19% 3	3480
	21st to end	Day	48% 6% 10% 25% 9% 1	3814
April	1st to 10th	Day	37% 6% 11% 22% 18% 6%	2123
	11th to 20th	Day	40% 5% 12% 22% 16% 5%	2254
	21st to end	Day	46% 5% 9% 22% 16% 1	2401
May	1st to 10th	Day	48% 5% 9% 21% 15% 3	4120
	11th to 20th	Day	39% 7% 14% 24% 16% 1	4086
	21st to end	Day	44% 9% 14% 19% 12% 3	4489
June	1st to 10th	Day	32% 8% 16% 26% 16% 2	2470
	11th to 20th	Day	32% 7% 13% 29% 17% 2	2470
	21st to end	Day	25% 6% 15% 30% 20% 5%	2470
July	1st to 10th	Day	34% 7% 17% 26% 14% 3	4056
	11th to 20th	Day	26% 5% 11% 35% 20% 3	4051
	21st to end	Day	27% 6% 19% 33% 15%	4325
August	1st to 10th	Day	23% 5% 14% 28% 25% 5%	4090
	11th to 20th	Day	31% 6% 20% 25% 16% 2	4080
	21st to end	Day	25% 6% 12% 40% 14% 3	4257
September	1st to 10th	Day	31% 5% 10% 23% 22% 10%	2183
	11th to 20th	Day	33% 7% 13% 21% 21% 5%	2090
	21st to end	Day	29% 5% 9% 23% 28% 6%	2090
October	1st to 10th	Day	28% 5% 12% 22% 28% 7%	1942
	11th to 20th	Day	26% 3 7% 23% 32% 9%	1900
	21st to end	Day	35% 3 8% 26% 20% 8%	2090
November	1st to 10th	Day	28% 4 8% 27% 25% 7%	1878
	11th to 20th	Day	31% 3 9% 27% 24% 7%	1748
	21st to end	Day	35% 3 8% 25% 24% 5%	1710
December	1st to 10th	Day	38% 4 10% 27% 19% 2	1710
	11th to 20th	Day	42% 3 8% 23% 22% 3	2159
	21st to end	Day	55% 4 10% 20% 10% 2	3135
January	1st to 10th	Night	38% 5% 9% 26% 19% 3	4108
	11th to 20th	Night	32% 6% 16% 20% 23% 2	4120
	21st to end	Night	43% 3 11% 20% 20% 3	4532
February	1st to 10th	Night	42% 3 11% 22% 17% 5%	2470
	11th to 20th	Night	38% 3 8% 27% 19% 5%	2320
	21st to end	Night	38% 4 7% 20% 22% 9%	1822
March	1st to 10th	Night	38% 4 8% 21% 17% 11%	3419
	11th to 20th	Night	30% 4 11% 31% 20% 5%	3480
	21st to end	Night	38% 5% 12% 30% 13% 2	3817
April	1st to 10th	Night	32% 5% 9% 23% 22% 9%	2056
	11th to 20th	Night	35% 5% 11% 23% 19% 8%	1875
	21st to end	Night	40% 4 10% 24% 20% 3	1776
May	1st to 10th	Night	41% 6% 11% 20% 18% 4	2850
	11th to 20th	Night	39% 6% 13% 25% 16% 2	2824
	21st to end	Night	32% 9% 17% 24% 16% 1	3099
June	1st to 10th	Night	25% 9% 15% 29% 19% 3	1710
	11th to 20th	Night	21% 7% 15% 32% 21% 3	1710
	21st to end	Night	19% 5% 14% 32% 25% 7%	1710
July	1st to 10th	Night	29% 6% 17% 27% 17% 5%	2805
	11th to 20th	Night	18% 4 11% 38% 26% 3	2796
	21st to end	Night	23% 4 16% 38% 18% 1	2999
August	1st to 10th	Night	16% 5% 14% 31% 27% 6%	2826
	11th to 20th	Night	29% 6% 17% 26% 19% 3	2825
	21st to end	Night	19% 5% 11% 40% 21% 5%	3398
September	1st to 10th	Night	26% 5% 9% 26% 24% 10%	1992
	11th to 20th	Night	30% 6% 10% 22% 24% 7%	2090
	21st to end	Night	26% 4 9% 25% 30% 6%	2090
October	1st to 10th	Night	23% 4 11% 22% 29% 11%	2218
	11th to 20th	Night	27% 4 6% 20% 31% 11%	2280
	21st to end	Night	32% 4 8% 23% 25% 9%	2508
November	1st to 10th	Night	26% 3 8% 25% 30% 8%	2245
	11th to 20th	Night	29% 4 7% 26% 26% 9%	2427
	21st to end	Night	34% 3 8% 22% 28% 6%	2470
December	1st to 10th	Night	35% 5% 11% 26% 19% 4	2470
	11th to 20th	Night	39% 4 8% 21% 24% 4	3037
	21st to end	Night	46% 4 10% 22% 15% 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	25% 17% 33% 21% 4	270
	11th to 20th	Day	26% 24% 36% 12% 2	270
	21st to end	Day	22% 21% 35% 16% 5%	297
February	1st to 10th	Day	26% 19% 38% 13% 4	270
	11th to 20th	Day	23% 23% 39% 14% 1	270
	21st to end	Day	28% 29% 33% 8% 1	225
March	1st to 10th	Day	24% 23% 32% 18% 3	270
	11th to 20th	Day	24% 24% 32% 17% 3	270
	21st to end	Day	26% 27% 30% 13% 4	297
April	1st to 10th	Day	19% 26% 35% 16% 4	303
	11th to 20th	Day	21% 23% 35% 15% 5%	452
	21st to end	Day	24% 18% 34% 16% 7% 1	581
May	1st to 10th	Day	18% 15% 38% 22% 6%	653
	11th to 20th	Day	18% 14% 31% 25% 10% 2	675
	21st to end	Day	16% 11% 33% 20% 14% 5%	734
June	1st to 10th	Day	7% 5% 25% 35% 23% 5%	680
	11th to 20th	Day	8% 4 29% 37% 18% 4	680
	21st to end	Day	4 4 28% 40% 20% 4	680
July	1st to 10th	Day	8% 2 15% 38% 28% 9%	671
	11th to 20th	Day	4 1 17% 41% 29% 6%	668
	21st to end	Day	8% 1 13% 35% 32% 12%	739
August	1st to 10th	Day	6% 3 17% 42% 28% 5%	676
	11th to 20th	Day	9% 2 18% 35% 30% 5%	665
	21st to end	Day	7% 2 12% 34% 35% 9%	591
September	1st to 10th	Day	10% 2 15% 31% 33% 9%	393
	11th to 20th	Day	6% 2 23% 37% 28% 4	300
	21st to end	Day	12% 6% 22% 35% 19% 6%	300
October	1st to 10th	Day	10% 8% 33% 28% 17% 5%	300
	11th to 20th	Day	9% 17% 38% 28% 7%	300
	21st to end	Day	24% 17% 32% 19% 7% 1	330
November	1st to 10th	Day	14% 15% 38% 22% 10% 1	276
	11th to 20th	Day	17% 16% 39% 20% 7% 3	270
	21st to end	Day	26% 16% 36% 19% 3	270
December	1st to 10th	Day	18% 21% 34% 19% 7% 2	270
	11th to 20th	Day	24% 17% 40% 14% 6%	270
	21st to end	Day	20% 25% 40% 13% 2	297
January	1st to 10th	Night	16% 17% 37% 25% 5%	950
	11th to 20th	Night	18% 18% 38% 23% 4	950
	21st to end	Night	15% 18% 37% 27% 4	1045
February	1st to 10th	Night	21% 17% 38% 21% 3	950
	11th to 20th	Night	21% 18% 36% 23% 2	845
	21st to end	Night	20% 20% 36% 22% 2	566
March	1st to 10th	Night	18% 15% 37% 27% 4	570
	11th to 20th	Night	19% 16% 37% 25% 3	570
	21st to end	Night	20% 15% 40% 21% 4	627
April	1st to 10th	Night	16% 16% 42% 21% 5%	570
	11th to 20th	Night	18% 13% 39% 25% 6%	563
	21st to end	Night	19% 12% 42% 20% 6%	570
May	1st to 10th	Night	14% 11% 40% 29% 6%	570
	11th to 20th	Night	13% 9% 31% 33% 12% 1	561
	21st to end	Night	13% 7% 31% 29% 19% 1	617
June	1st to 10th	Night	7% 3 21% 42% 26% 1	570
	11th to 20th	Night	3 3 31% 44% 18% 1	570
	21st to end	Night	3 2 27% 47% 19% 2	570
July	1st to 10th	Night	6% 1 16% 47% 27% 3	555
	11th to 20th	Night	2 1 17% 45% 32% 3	552
	21st to end	Night	6% 15% 43% 33% 3	624
August	1st to 10th	Night	3 2 17% 46% 30% 2	567
	11th to 20th	Night	7% 2 14% 48% 26% 3	564
	21st to end	Night	4 1 14% 40% 37% 4	627
September	1st to 10th	Night	11% 1 16% 44% 28% 1	570
	11th to 20th	Night	10% 2 19% 42% 23% 4	570
	21st to end	Night	10% 3 23% 38% 24% 3	570
October	1st to 10th	Night	8% 3 29% 36% 21% 3	698
	11th to 20th	Night	14% 9% 38% 29% 9%	760
	21st to end	Night	17% 13% 32% 28% 10% 1	836
November	1st to 10th	Night	13% 11% 40% 26% 11% 1	749
	11th to 20th	Night	13% 16% 36% 28% 7%	907
	21st to end	Night	19% 15% 35% 24% 7%	950
December	1st to 10th	Night	16% 16% 34% 28% 5%	950
	11th to 20th	Night	21% 14% 36% 25% 4	950
	21st to end	Night	18% 19% 35% 25% 3	1045

Page generated at 2024-10-31 02:39:24. Version ac07

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