Fulton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fulton 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	12% 8% 3 6% 4 4 4 4 5% 7% 43%	101148
	Night	12% 9% 3 6% 4 4 4 3 5% 6% 44%	97727
Transparency	Day	39% 7% 13% 24% 15% 2	100947
	Night	40% 6% 12% 24% 16% 3	97599
Seeing	Day	16% 12% 28% 27% 14% 3	15628
	Night	16% 11% 31% 28% 12% 1	25421

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% 13% 4 10% 5% 5% 4 4 5% 7% 32%	2573
	11th to 20th	Day	13% 12% 4 8% 5% 7% 5% 3 4 5% 35%	2850
	21st to end	Day	18% 15% 7% 9% 4 3 3 3 4 5% 30%	3135
February	1st to 10th	Day	16% 12% 4 8% 5% 4 4 3 4 6% 34%	1710
	11th to 20th	Day	14% 10% 3 6% 5% 5% 3 4 4 6% 40%	1735
	21st to end	Day	15% 11% 4 7% 4 4 3 4 4 5% 39%	1570
March	1st to 10th	Day	17% 10% 3 5% 3 3 3 2 3 5% 43%	3360
	11th to 20th	Day	12% 7% 3 6% 3 3 3 3 5% 6% 49%	3480
	21st to end	Day	16% 12% 3 8% 5% 5% 4 4 5% 7% 31%	3899
April	1st to 10th	Day	12% 9% 2 6% 5% 3 5% 3 5% 7% 44%	2280
	11th to 20th	Day	17% 9% 2 6% 4 3 4 3 5% 6% 42%	2254
	21st to end	Day	21% 7% 3 7% 4 4 4 3 5% 8% 34%	2280
May	1st to 10th	Day	14% 8% 3 7% 5% 5% 5% 4 7% 9% 34%	3945
	11th to 20th	Day	16% 9% 3 7% 4 4 4 3 5% 7% 37%	4303
	21st to end	Day	11% 6% 3 6% 5% 4 5% 4 6% 7% 45%	4824
June	1st to 10th	Day	8% 4 2 5% 4 5% 5% 5% 7% 10% 46%	2660
	11th to 20th	Day	8% 5% 2 5% 4 4 5% 4 6% 9% 48%	2660
	21st to end	Day	6% 4 2 4 5% 5% 5% 4 7% 10% 48%	2660
July	1st to 10th	Day	13% 6% 2 6% 4 4 5% 4 6% 9% 39%	4440
	11th to 20th	Day	5% 4 2 6% 4 4 5% 4 7% 10% 50%	4324
	21st to end	Day	8% 5% 2 5% 4 5% 6% 5% 9% 11% 41%	4465
August	1st to 10th	Day	5% 3 1 4 4 4 5% 5% 8% 10% 50%	4104
	11th to 20th	Day	13% 5% 2 5% 4 4 5% 4 6% 7% 45%	3864
	21st to end	Day	5% 4 2 5% 4 4 4 4 6% 9% 53%	4180
September	1st to 10th	Day	11% 5% 2 5% 4 3 4 3 5% 7% 51%	2280
	11th to 20th	Day	10% 5% 2 5% 4 4 4 3 5% 8% 52%	2280
	21st to end	Day	8% 5% 2 5% 4 4 4 4 5% 7% 52%	2007
October	1st to 10th	Day	11% 5% 2 5% 4 4 4 3 4 5% 55%	1900
	11th to 20th	Day	15% 7% 2 4 3 2 3 3 4 5% 53%	1900
	21st to end	Day	18% 9% 3 5% 3 3 3 2 3 5% 47%	2026
November	1st to 10th	Day	11% 7% 2 4 3 2 3 3 4 6% 54%	1746
	11th to 20th	Day	14% 8% 2 5% 3 3 2 3 5% 6% 47%	1710
	21st to end	Day	16% 10% 2 6% 3 4 3 2 4 5% 43%	1523
December	1st to 10th	Day	12% 12% 4 6% 4 4 3 3 5% 7% 41%	1520
	11th to 20th	Day	13% 10% 4 7% 4 3 4 3 5% 5% 41%	1918
	21st to end	Day	19% 17% 4 11% 4 4 5% 3 4 5% 23%	2783
January	1st to 10th	Night	11% 11% 8% 11% 5% 4 3 3 4 4 35%	4364
	11th to 20th	Night	12% 12% 5% 11% 5% 5% 6% 5% 4 5% 30%	4120
	21st to end	Night	20% 16% 6% 8% 4 3 3 2 4 4 30%	4532
February	1st to 10th	Night	15% 11% 3 9% 6% 4 4 4 5% 5% 34%	2470
	11th to 20th	Night	14% 9% 4 7% 5% 4 3 4 4 6% 40%	2330
	21st to end	Night	16% 11% 3 7% 4 3 3 2 5% 4 42%	1884
March	1st to 10th	Night	19% 12% 2 4 3 3 2 3 3 4 44%	3523
	11th to 20th	Night	14% 7% 2 4 3 3 3 3 4 5% 51%	3480
	21st to end	Night	17% 14% 4 9% 5% 4 4 3 4 5% 31%	3732
April	1st to 10th	Night	11% 8% 3 6% 4 3 3 3 5% 6% 47%	1900
	11th to 20th	Night	13% 9% 3 5% 4 3 4 3 4 7% 45%	1875
	21st to end	Night	18% 7% 3 5% 4 3 4 4 5% 7% 40%	1900
May	1st to 10th	Night	16% 9% 2 5% 4 4 3 3 6% 9% 39%	2954
	11th to 20th	Night	13% 9% 3 6% 4 4 4 4 5% 8% 42%	2584
	21st to end	Night	10% 5% 2 5% 3 4 4 4 6% 8% 47%	2743
June	1st to 10th	Night	8% 4 1 4 3 4 4 4 6% 8% 52%	1520
	11th to 20th	Night	5% 5% 2 6% 4 3 4 4 6% 11% 49%	1520
	21st to end	Night	4 3 1 4 3 4 4 4 7% 10% 56%	1520
July	1st to 10th	Night	11% 6% 2 6% 4 4 4 3 5% 10% 44%	2530
	11th to 20th	Night	4 3 1 3 3 3 4 4 6% 11% 59%	2642
	21st to end	Night	5% 5% 2 6% 4 5% 5% 5% 7% 10% 46%	3098
August	1st to 10th	Night	4 3 1 3 3 3 3 4 6% 9% 61%	2836
	11th to 20th	Night	11% 6% 2 5% 4 3 4 3 5% 7% 51%	2969
	21st to end	Night	5% 3 1 4 3 3 4 3 6% 9% 59%	3476
September	1st to 10th	Night	11% 4 2 3 3 2 3 3 3 8% 57%	1900
	11th to 20th	Night	8% 5% 2 5% 4 3 4 3 7% 7% 52%	1900
	21st to end	Night	7% 5% 2 5% 4 4 4 3 5% 7% 55%	2151
October	1st to 10th	Night	8% 4 2 4 3 3 3 3 5% 5% 60%	2280
	11th to 20th	Night	14% 6% 2 5% 3 3 3 2 4 5% 53%	2280
	21st to end	Night	17% 9% 2 5% 3 3 3 2 4 5% 48%	2436
November	1st to 10th	Night	10% 5% 2 5% 3 3 3 2 4 5% 56%	2330
	11th to 20th	Night	12% 7% 3 7% 4 3 3 3 4 6% 49%	2470
	21st to end	Night	16% 9% 2 6% 4 3 3 3 4 5% 44%	2655
December	1st to 10th	Night	13% 12% 4 6% 4 5% 4 3 6% 6% 39%	2660
	11th to 20th	Night	14% 12% 4 7% 3 4 3 3 5% 5% 40%	3279
	21st to end	Night	19% 19% 7% 9% 5% 4 3 3 3 4 24%	4884

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% 7% 10% 22% 10% 1	2574
	11th to 20th	Day	51% 6% 12% 20% 11%	2850
	21st to end	Day	57% 5% 10% 15% 12% 1	3135
February	1st to 10th	Day	52% 5% 11% 21% 11% 1	1710
	11th to 20th	Day	45% 6% 12% 20% 14% 3	1744
	21st to end	Day	47% 5% 9% 22% 13% 4	1570
March	1st to 10th	Day	44% 4 8% 22% 17% 4	3360
	11th to 20th	Day	35% 6% 13% 26% 17% 5%	3480
	21st to end	Day	50% 9% 16% 18% 7%	3899
April	1st to 10th	Day	40% 6% 11% 25% 16% 1	2280
	11th to 20th	Day	43% 5% 10% 24% 15% 3	2254
	21st to end	Day	48% 6% 13% 19% 13% 1	2280
May	1st to 10th	Day	43% 10% 15% 20% 11% 1	3980
	11th to 20th	Day	45% 8% 11% 23% 12% 1	4307
	21st to end	Day	36% 9% 11% 24% 19% 1	4837
June	1st to 10th	Day	30% 10% 16% 28% 15% 2	2660
	11th to 20th	Day	30% 9% 14% 25% 18% 4	2660
	21st to end	Day	28% 10% 17% 25% 16% 4	2660
July	1st to 10th	Day	40% 7% 13% 23% 14% 2	4371
	11th to 20th	Day	28% 8% 14% 31% 17% 2	4249
	21st to end	Day	32% 11% 20% 25% 11% 1	4325
August	1st to 10th	Day	25% 8% 18% 35% 14% 1	4090
	11th to 20th	Day	37% 7% 13% 25% 16% 1	3903
	21st to end	Day	26% 8% 16% 33% 13% 3	4179
September	1st to 10th	Day	32% 6% 11% 24% 21% 5%	2280
	11th to 20th	Day	31% 6% 10% 27% 22% 3	2280
	21st to end	Day	30% 7% 11% 26% 23% 3	2007
October	1st to 10th	Day	32% 5% 10% 23% 26% 5%	1900
	11th to 20th	Day	34% 4 8% 25% 23% 5%	1900
	21st to end	Day	42% 4 9% 23% 18% 3	2026
November	1st to 10th	Day	31% 5% 13% 24% 22% 5%	1746
	11th to 20th	Day	38% 5% 9% 23% 21% 4	1710
	21st to end	Day	44% 5% 10% 27% 14% 1	1523
December	1st to 10th	Day	43% 5% 13% 27% 12% 1	1520
	11th to 20th	Day	44% 6% 12% 24% 12% 2	1915
	21st to end	Day	61% 7% 9% 14% 8% 1	2783
January	1st to 10th	Night	52% 5% 11% 22% 10% 1	4364
	11th to 20th	Night	55% 6% 10% 19% 9% 1	4120
	21st to end	Night	59% 4 10% 19% 7% 1	4532
February	1st to 10th	Night	52% 6% 10% 18% 13% 2	2470
	11th to 20th	Night	44% 5% 11% 21% 16% 3	2331
	21st to end	Night	46% 4 10% 21% 16% 4	1884
March	1st to 10th	Night	44% 5% 9% 22% 17% 3	3523
	11th to 20th	Night	35% 6% 9% 23% 23% 4	3480
	21st to end	Night	54% 8% 11% 22% 5%	3732
April	1st to 10th	Night	37% 6% 11% 25% 18% 4	1900
	11th to 20th	Night	39% 6% 9% 24% 17% 5%	1875
	21st to end	Night	43% 6% 10% 22% 17% 1	1900
May	1st to 10th	Night	39% 10% 18% 18% 14% 1	2984
	11th to 20th	Night	39% 10% 13% 26% 11% 1	2585
	21st to end	Night	31% 11% 16% 20% 21% 2	2751
June	1st to 10th	Night	27% 9% 16% 28% 18% 3	1520
	11th to 20th	Night	27% 8% 11% 27% 23% 3	1520
	21st to end	Night	22% 8% 18% 27% 19% 7%	1520
July	1st to 10th	Night	36% 7% 11% 29% 15% 2	2490
	11th to 20th	Night	18% 7% 15% 38% 20% 2	2594
	21st to end	Night	30% 9% 20% 27% 13% 1	2999
August	1st to 10th	Night	19% 7% 19% 34% 19% 1	2826
	11th to 20th	Night	33% 6% 13% 27% 18% 3	2996
	21st to end	Night	21% 7% 20% 33% 16% 4	3476
September	1st to 10th	Night	27% 6% 13% 24% 24% 7%	1900
	11th to 20th	Night	29% 7% 11% 24% 24% 5%	1900
	21st to end	Night	29% 5% 9% 26% 27% 4	2151
October	1st to 10th	Night	26% 5% 10% 25% 29% 5%	2280
	11th to 20th	Night	34% 4 7% 27% 21% 6%	2280
	21st to end	Night	40% 4 9% 20% 22% 4	2436
November	1st to 10th	Night	30% 5% 13% 27% 19% 6%	2330
	11th to 20th	Night	37% 4 8% 25% 22% 4	2470
	21st to end	Night	43% 4 11% 24% 16% 2	2655
December	1st to 10th	Night	46% 6% 11% 23% 13% 1	2660
	11th to 20th	Night	46% 4 10% 25% 14% 1	3281
	21st to end	Night	65% 5% 9% 13% 7% 1	4884

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	26% 19% 37% 16% 3	270
	11th to 20th	Day	34% 20% 34% 11% 1	270
	21st to end	Day	21% 24% 39% 13% 3	297
February	1st to 10th	Day	28% 21% 34% 15% 2	270
	11th to 20th	Day	24% 26% 34% 14% 2	270
	21st to end	Day	31% 23% 34% 12% 1	225
March	1st to 10th	Day	20% 24% 45% 11% 1	270
	11th to 20th	Day	28% 19% 36% 15% 2	270
	21st to end	Day	34% 22% 30% 12% 2	344
April	1st to 10th	Day	21% 16% 38% 19% 6% 1	460
	11th to 20th	Day	27% 17% 32% 18% 6%	452
	21st to end	Day	27% 14% 35% 19% 4 1	460
May	1st to 10th	Day	19% 14% 37% 23% 6% 1	565
	11th to 20th	Day	18% 14% 27% 27% 12% 2	675
	21st to end	Day	14% 11% 32% 26% 13% 5%	734
June	1st to 10th	Day	9% 5% 26% 37% 18% 6%	680
	11th to 20th	Day	8% 4 28% 41% 16% 3	680
	21st to end	Day	7% 9% 32% 35% 14% 3	680
July	1st to 10th	Day	12% 4 17% 30% 29% 8%	671
	11th to 20th	Day	7% 5% 22% 36% 26% 4	668
	21st to end	Day	9% 4 19% 35% 28% 5%	739
August	1st to 10th	Day	8% 3 19% 43% 22% 4	676
	11th to 20th	Day	11% 3 22% 34% 23% 6%	566
	21st to end	Day	9% 2 17% 32% 31% 9%	539
September	1st to 10th	Day	11% 5% 17% 32% 28% 7%	490
	11th to 20th	Day	8% 3 20% 35% 25% 9%	490
	21st to end	Day	11% 11% 26% 30% 19% 4	359
October	1st to 10th	Day	14% 8% 35% 26% 15% 3	300
	11th to 20th	Day	20% 20% 28% 24% 7%	300
	21st to end	Day	31% 20% 28% 19% 2	311
November	1st to 10th	Day	15% 13% 36% 23% 9% 3	270
	11th to 20th	Day	21% 19% 31% 23% 6% 1	270
	21st to end	Day	27% 16% 29% 25% 3	270
December	1st to 10th	Day	18% 20% 37% 16% 7% 2	270
	11th to 20th	Day	22% 19% 37% 18% 3 1	270
	21st to end	Day	25% 28% 33% 14%	297
January	1st to 10th	Night	17% 18% 40% 19% 5%	950
	11th to 20th	Night	21% 19% 36% 19% 4	950
	21st to end	Night	18% 18% 39% 22% 2	1045
February	1st to 10th	Night	21% 17% 39% 20% 3	950
	11th to 20th	Night	20% 18% 38% 22% 2	856
	21st to end	Night	24% 20% 37% 17% 2	628
March	1st to 10th	Night	22% 15% 41% 20% 3	640
	11th to 20th	Night	22% 15% 35% 25% 4	570
	21st to end	Night	27% 16% 36% 19% 3	627
April	1st to 10th	Night	15% 18% 39% 23% 4	570
	11th to 20th	Night	18% 16% 34% 25% 7%	563
	21st to end	Night	21% 10% 39% 24% 6%	570
May	1st to 10th	Night	17% 8% 34% 33% 8% 1	570
	11th to 20th	Night	17% 7% 27% 35% 13% 1	561
	21st to end	Night	13% 6% 29% 32% 18% 2	617
June	1st to 10th	Night	8% 4 21% 40% 24% 2	570
	11th to 20th	Night	6% 3 26% 43% 21% 1	570
	21st to end	Night	4 3 29% 45% 16% 2	570
July	1st to 10th	Night	11% 3 14% 36% 31% 5%	555
	11th to 20th	Night	5% 2 19% 40% 33% 2	552
	21st to end	Night	7% 2 16% 41% 32% 2	624
August	1st to 10th	Night	6% 4 13% 44% 32% 2	567
	11th to 20th	Night	8% 1 15% 40% 32% 3	564
	21st to end	Night	7% 1 15% 39% 34% 3	627
September	1st to 10th	Night	12% 3 18% 37% 25% 5%	570
	11th to 20th	Night	10% 3 16% 39% 27% 5%	570
	21st to end	Night	10% 6% 24% 34% 21% 4	693
October	1st to 10th	Night	10% 7% 28% 31% 21% 4	760
	11th to 20th	Night	17% 12% 35% 27% 9%	760
	21st to end	Night	21% 15% 32% 24% 7%	812
November	1st to 10th	Night	13% 11% 37% 29% 9%	740
	11th to 20th	Night	16% 16% 36% 25% 7%	760
	21st to end	Night	22% 13% 35% 24% 6%	945
December	1st to 10th	Night	21% 15% 36% 23% 5% 1	950
	11th to 20th	Night	24% 12% 34% 26% 3	950
	21st to end	Night	25% 18% 34% 21% 2	1045

Page generated at 2024-10-22 19:21:00. Version ac07

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