FoxStar Observatory
Clear Sky Chart
History

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

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% 7% 3 6% 4 4 4 3 5% 7% 45%	101135
	Night	12% 7% 3 6% 4 4 4 3 5% 6% 48%	98100
Transparency	Day	38% 3 12% 27% 17% 2	104786
	Night	37% 3 11% 27% 19% 3	102589
Seeing	Day	15% 10% 28% 28% 16% 4	15688
	Night	14% 9% 32% 32% 12% 1	25512

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% 9% 4 9% 4 4 4 3 5% 6% 37%	2847
	11th to 20th	Day	12% 11% 4 9% 6% 7% 6% 3 2 4 37%	2850
	21st to end	Day	16% 16% 5% 9% 3 3 3 2 4 4 34%	3135
February	1st to 10th	Day	15% 12% 4 8% 5% 3 3 3 5% 6% 36%	1710
	11th to 20th	Day	13% 11% 3 7% 4 4 4 3 4 6% 41%	1664
	21st to end	Day	12% 9% 3 7% 4 3 4 3 5% 6% 43%	1612
March	1st to 10th	Day	14% 12% 2 6% 4 3 3 2 4 5% 46%	3436
	11th to 20th	Day	12% 7% 2 4 3 3 3 3 4 6% 52%	3480
	21st to end	Day	17% 12% 4 6% 4 4 4 3 5% 6% 35%	3814
April	1st to 10th	Day	14% 7% 3 6% 4 4 4 3 4 7% 44%	2218
	11th to 20th	Day	15% 9% 2 7% 5% 4 4 4 5% 6% 40%	2254
	21st to end	Day	20% 6% 3 8% 5% 4 5% 4 4 6% 35%	2377
May	1st to 10th	Day	15% 8% 2 7% 5% 4 4 4 5% 7% 39%	4082
	11th to 20th	Day	17% 7% 3 6% 5% 4 4 3 5% 7% 39%	4082
	21st to end	Day	13% 6% 2 6% 4 4 4 4 5% 7% 45%	4692
June	1st to 10th	Day	7% 5% 2 4 4 4 4 5% 7% 11% 48%	2660
	11th to 20th	Day	7% 5% 2 6% 5% 3 5% 4 6% 9% 48%	2660
	21st to end	Day	7% 3 2 4 4 4 5% 4 7% 8% 52%	2660
July	1st to 10th	Day	12% 7% 2 6% 4 4 5% 3 6% 8% 42%	4226
	11th to 20th	Day	5% 3 2 4 3 4 4 4 7% 9% 54%	4120
	21st to end	Day	6% 4 2 6% 4 6% 6% 6% 8% 10% 43%	4465
August	1st to 10th	Day	5% 3 2 5% 3 4 4 3 6% 9% 54%	4104
	11th to 20th	Day	11% 5% 2 5% 4 4 4 3 6% 8% 48%	4041
	21st to end	Day	5% 4 2 5% 3 3 4 4 6% 9% 55%	4223
September	1st to 10th	Day	12% 4 2 5% 3 3 3 3 6% 7% 54%	2280
	11th to 20th	Day	9% 5% 1 5% 3 4 4 4 5% 7% 52%	2148
	21st to end	Day	9% 5% 2 5% 4 3 4 4 5% 6% 55%	2054
October	1st to 10th	Day	11% 5% 2 5% 3 3 4 2 5% 6% 54%	1900
	11th to 20th	Day	13% 6% 1 5% 3 3 2 2 4 6% 55%	1900
	21st to end	Day	16% 7% 2 6% 3 3 4 2 4 6% 46%	2090
November	1st to 10th	Day	10% 6% 2 6% 3 3 3 3 4 7% 52%	1948
	11th to 20th	Day	14% 6% 2 5% 3 3 4 3 4 6% 50%	1621
	21st to end	Day	15% 9% 3 6% 4 3 3 3 3 4 47%	1520
December	1st to 10th	Day	11% 8% 2 6% 6% 3 3 3 4 7% 45%	1520
	11th to 20th	Day	12% 10% 4 8% 6% 3 4 2 6% 5% 40%	1918
	21st to end	Day	16% 14% 7% 13% 5% 4 4 3 4 4 27%	2824
January	1st to 10th	Night	9% 10% 3 15% 5% 4 4 2 4 4 39%	4108
	11th to 20th	Night	12% 10% 4 8% 5% 7% 6% 4 4 5% 36%	4120
	21st to end	Night	17% 12% 5% 10% 4 3 3 2 4 5% 34%	4532
February	1st to 10th	Night	12% 11% 3 7% 5% 5% 4 3 5% 6% 38%	2470
	11th to 20th	Night	12% 9% 3 8% 5% 4 4 3 5% 6% 43%	2403
	21st to end	Night	14% 7% 3 8% 4 4 3 3 3 5% 46%	1855
March	1st to 10th	Night	14% 10% 3 6% 3 3 3 3 4 5% 47%	3419
	11th to 20th	Night	12% 7% 2 4 3 2 3 3 4 7% 54%	3480
	21st to end	Night	16% 9% 5% 8% 5% 4 4 3 5% 6% 35%	3817
April	1st to 10th	Night	11% 7% 2 5% 3 4 4 3 5% 6% 50%	1962
	11th to 20th	Night	14% 7% 3 6% 3 3 3 3 5% 7% 47%	1875
	21st to end	Night	18% 7% 2 5% 3 4 3 3 5% 7% 42%	1800
May	1st to 10th	Night	16% 6% 2 6% 5% 4 5% 4 5% 6% 42%	2823
	11th to 20th	Night	16% 6% 2 5% 4 3 4 4 6% 7% 43%	2823
	21st to end	Night	12% 4 1 4 4 3 4 3 5% 6% 53%	2873
June	1st to 10th	Night	7% 3 1 4 3 4 4 4 6% 11% 53%	1520
	11th to 20th	Night	6% 3 2 5% 5% 4 4 4 7% 11% 50%	1520
	21st to end	Night	5% 2 1 4 3 3 4 3 7% 9% 59%	1520
July	1st to 10th	Night	12% 6% 2 5% 4 4 4 3 4 9% 47%	2738
	11th to 20th	Night	4 2 1 4 3 3 4 4 6% 9% 62%	2850
	21st to end	Night	5% 4 2 5% 4 4 5% 5% 7% 11% 48%	3098
August	1st to 10th	Night	3 1 1 3 3 3 4 4 6% 11% 62%	2836
	11th to 20th	Night	12% 7% 2 4 3 3 4 3 4 6% 51%	2798
	21st to end	Night	4 3 2 5% 4 3 3 3 5% 7% 60%	3432
September	1st to 10th	Night	11% 4 2 4 4 2 4 3 4 5% 57%	1900
	11th to 20th	Night	10% 4 1 4 2 3 4 4 5% 8% 55%	2028
	21st to end	Night	7% 4 2 5% 4 3 4 3 4 6% 57%	2106
October	1st to 10th	Night	10% 4 2 4 3 4 3 3 4 5% 59%	2280
	11th to 20th	Night	13% 4 2 4 3 3 2 2 4 5% 57%	2280
	21st to end	Night	16% 6% 2 5% 3 3 3 2 4 4 52%	2508
November	1st to 10th	Night	10% 5% 2 4 3 3 3 3 4 5% 60%	2335
	11th to 20th	Night	11% 6% 2 5% 4 3 3 3 5% 6% 53%	2554
	21st to end	Night	14% 8% 2 5% 3 3 3 3 4 5% 50%	2660
December	1st to 10th	Night	12% 8% 3 5% 4 4 4 3 5% 6% 46%	2660
	11th to 20th	Night	12% 8% 3 6% 3 4 4 3 5% 6% 45%	3279
	21st to end	Night	18% 16% 5% 11% 4 3 3 2 3 4 29%	4838

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	50% 2 10% 25% 12% 1	2848
	11th to 20th	Day	54% 1 11% 22% 10%	2850
	21st to end	Day	56% 1 10% 18% 14% 1	3135
February	1st to 10th	Day	50% 3 12% 22% 11% 2	1710
	11th to 20th	Day	45% 3 12% 22% 15% 2	1673
	21st to end	Day	42% 2 11% 24% 18% 3	1612
March	1st to 10th	Day	43% 2 8% 24% 21% 2	3436
	11th to 20th	Day	35% 2 12% 29% 19% 3	3480
	21st to end	Day	53% 1 17% 23% 6% 1	3814
April	1st to 10th	Day	41% 3 12% 25% 16% 2	2218
	11th to 20th	Day	45% 3 12% 24% 15% 1	2254
	21st to end	Day	51% 3 10% 25% 10% 1	2377
May	1st to 10th	Day	47% 2 11% 24% 13% 1	4120
	11th to 20th	Day	47% 3 13% 23% 14%	4086
	21st to end	Day	40% 3 10% 33% 13% 2	4705
June	1st to 10th	Day	30% 4 18% 32% 14% 2	2660
	11th to 20th	Day	33% 3 15% 31% 17% 1	2660
	21st to end	Day	28% 4 17% 31% 15% 4	2660
July	1st to 10th	Day	40% 4 14% 23% 16% 3	4162
	11th to 20th	Day	26% 5% 14% 36% 18% 2	4051
	21st to end	Day	29% 9% 17% 31% 12% 1	4325
August	1st to 10th	Day	26% 5% 16% 30% 22% 1	4090
	11th to 20th	Day	35% 5% 16% 28% 16% 1	4080
	21st to end	Day	25% 5% 15% 35% 15% 5%	4222
September	1st to 10th	Day	30% 3 12% 27% 21% 7%	2280
	11th to 20th	Day	31% 4 12% 26% 25% 2	2148
	21st to end	Day	31% 3 8% 31% 23% 3	2054
October	1st to 10th	Day	19% 1 7% 23% 40% 9%	3160
	11th to 20th	Day	21% 1 4 25% 40% 9%	3140
	21st to end	Day	34% 3 10% 24% 26% 3	3428
November	1st to 10th	Day	34% 2 13% 27% 19% 5%	1948
	11th to 20th	Day	38% 2 10% 26% 22% 3	1621
	21st to end	Day	43% 1 9% 27% 19% 1	1520
December	1st to 10th	Day	41% 2 13% 29% 14% 1	1520
	11th to 20th	Day	46% 2 13% 27% 10% 2	1915
	21st to end	Day	63% 2 10% 16% 8% 1	2824
January	1st to 10th	Night	50% 2 12% 23% 12% 1	4108
	11th to 20th	Night	53% 2 11% 21% 12% 1	4120
	21st to end	Night	55% 1 12% 19% 11% 1	4532
February	1st to 10th	Night	47% 3 10% 23% 14% 3	2470
	11th to 20th	Night	43% 2 11% 22% 18% 3	2404
	21st to end	Night	42% 2 8% 23% 19% 5%	1855
March	1st to 10th	Night	42% 1 9% 24% 21% 3	3419
	11th to 20th	Night	32% 2 8% 29% 25% 5%	3480
	21st to end	Night	52% 2 16% 23% 7% 1	3817
April	1st to 10th	Night	36% 3 10% 26% 21% 4	1962
	11th to 20th	Night	39% 2 8% 30% 17% 4	1875
	21st to end	Night	43% 3 10% 27% 16% 1	1800
May	1st to 10th	Night	45% 2 15% 21% 16% 1	2850
	11th to 20th	Night	42% 3 13% 29% 13% 1	2824
	21st to end	Night	34% 3 11% 29% 22% 1	2881
June	1st to 10th	Night	25% 4 17% 34% 17% 3	1520
	11th to 20th	Night	28% 4 13% 33% 20% 2	1520
	21st to end	Night	21% 4 15% 35% 21% 4	1520
July	1st to 10th	Night	36% 4 13% 25% 19% 4	2693
	11th to 20th	Night	19% 5% 14% 39% 21% 2	2796
	21st to end	Night	26% 7% 21% 32% 13% 1	2999
August	1st to 10th	Night	16% 4 23% 29% 24% 4	2826
	11th to 20th	Night	35% 3 10% 30% 21% 1	2825
	21st to end	Night	23% 5% 12% 38% 17% 4	3432
September	1st to 10th	Night	30% 3 10% 27% 23% 8%	1900
	11th to 20th	Night	28% 4 10% 29% 25% 5%	2028
	21st to end	Night	29% 3 7% 28% 29% 4	2106
October	1st to 10th	Night	18% 2 6% 21% 45% 8%	3800
	11th to 20th	Night	22% 2 5% 26% 31% 14%	3779
	21st to end	Night	34% 3 7% 30% 25% 2	4120
November	1st to 10th	Night	29% 2 13% 28% 23% 5%	2335
	11th to 20th	Night	33% 2 8% 28% 24% 5%	2554
	21st to end	Night	39% 2 9% 29% 18% 3	2660
December	1st to 10th	Night	40% 3 13% 28% 16% 1	2660
	11th to 20th	Night	41% 2 10% 30% 15% 1	3281
	21st to end	Night	62% 2 7% 18% 9% 2	4838

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	21% 18% 36% 20% 5%	270
	11th to 20th	Day	31% 16% 38% 14% 1	270
	21st to end	Day	15% 15% 48% 18% 4	297
February	1st to 10th	Day	27% 16% 38% 18% 2	270
	11th to 20th	Day	20% 20% 39% 16% 5%	270
	21st to end	Day	18% 27% 38% 12% 4 1	225
March	1st to 10th	Day	19% 16% 46% 16% 3	270
	11th to 20th	Day	30% 10% 36% 19% 4	270
	21st to end	Day	33% 18% 32% 13% 4	297
April	1st to 10th	Day	21% 17% 38% 17% 7% 1	398
	11th to 20th	Day	19% 17% 35% 21% 7% 1	452
	21st to end	Day	23% 15% 34% 17% 9% 1	557
May	1st to 10th	Day	20% 12% 37% 22% 7% 1	653
	11th to 20th	Day	20% 9% 30% 27% 12% 3	675
	21st to end	Day	16% 7% 29% 29% 15% 4	734
June	1st to 10th	Day	6% 5% 21% 35% 26% 7%	680
	11th to 20th	Day	9% 3 27% 39% 20% 3	680
	21st to end	Day	9% 6% 32% 34% 17% 2	680
July	1st to 10th	Day	13% 3 14% 28% 29% 13%	671
	11th to 20th	Day	4 2 22% 37% 26% 9%	668
	21st to end	Day	8% 3 15% 35% 31% 8%	739
August	1st to 10th	Day	6% 3 17% 40% 28% 6%	676
	11th to 20th	Day	8% 5% 18% 36% 28% 6%	665
	21st to end	Day	8% 1 15% 34% 31% 11%	569
September	1st to 10th	Day	13% 3 13% 37% 28% 7%	490
	11th to 20th	Day	6% 4 19% 40% 25% 5%	358
	21st to end	Day	13% 5% 29% 31% 16% 7%	300
October	1st to 10th	Day	13% 7% 29% 27% 18% 6%	300
	11th to 20th	Day	12% 19% 37% 24% 8%	300
	21st to end	Day	22% 18% 32% 22% 5% 1	330
November	1st to 10th	Day	16% 11% 39% 23% 7% 4	297
	11th to 20th	Day	17% 18% 32% 23% 9% 1	270
	21st to end	Day	23% 13% 34% 24% 6%	270
December	1st to 10th	Day	12% 17% 41% 21% 6% 4	270
	11th to 20th	Day	23% 14% 37% 20% 5% 1	270
	21st to end	Day	20% 25% 38% 16%	297
January	1st to 10th	Night	14% 13% 39% 27% 7%	950
	11th to 20th	Night	17% 15% 38% 23% 6% 1	950
	21st to end	Night	15% 13% 42% 27% 3	1045
February	1st to 10th	Night	18% 13% 44% 22% 4	950
	11th to 20th	Night	18% 13% 38% 27% 4	929
	21st to end	Night	19% 14% 44% 19% 4	599
March	1st to 10th	Night	16% 12% 42% 24% 5%	570
	11th to 20th	Night	20% 12% 34% 28% 6%	570
	21st to end	Night	27% 10% 37% 23% 3	627
April	1st to 10th	Night	15% 11% 41% 26% 6%	570
	11th to 20th	Night	20% 13% 32% 28% 7%	563
	21st to end	Night	21% 9% 35% 27% 7%	570
May	1st to 10th	Night	18% 9% 34% 32% 7% 1	570
	11th to 20th	Night	16% 6% 28% 35% 14% 1	561
	21st to end	Night	12% 5% 29% 36% 16% 3	617
June	1st to 10th	Night	7% 4 19% 44% 23% 3	570
	11th to 20th	Night	6% 3 25% 46% 19% 2	570
	21st to end	Night	5% 2 31% 47% 15% 1	570
July	1st to 10th	Night	9% 3 12% 39% 33% 4	555
	11th to 20th	Night	4 2 15% 44% 32% 3	552
	21st to end	Night	6% 2 14% 43% 33% 2	624
August	1st to 10th	Night	4 2 13% 47% 34% 1	567
	11th to 20th	Night	8% 3 13% 43% 29% 4	564
	21st to end	Night	5% 1 13% 43% 35% 2	627
September	1st to 10th	Night	11% 2 17% 42% 24% 4	570
	11th to 20th	Night	11% 2 21% 38% 25% 4	570
	21st to end	Night	8% 4 24% 41% 20% 4	586
October	1st to 10th	Night	11% 4 27% 36% 19% 2	760
	11th to 20th	Night	15% 8% 38% 31% 8%	760
	21st to end	Night	20% 10% 34% 26% 9%	836
November	1st to 10th	Night	12% 9% 36% 32% 10% 1	779
	11th to 20th	Night	13% 13% 38% 27% 9%	916
	21st to end	Night	20% 9% 38% 28% 5%	950
December	1st to 10th	Night	17% 11% 38% 27% 6% 1	950
	11th to 20th	Night	19% 10% 39% 27% 5%	950
	21st to end	Night	21% 15% 37% 23% 4	1045

Page generated at 2024-11-07 05:55:46. Version ac07

Copyright © 2024 Attilla Danko.