Robeson Planetarium and Science Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Robeson Planetarium and Science Center clear sky chart from 2005-11-06 to 2025-01-07.

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 6% 5% 4 5% 4 6% 8% 42%	105197
	Night	13% 6% 2 6% 4 4 4 4 6% 7% 43%	103794
Transparency	Day	39% 7% 11% 19% 18% 6%	108845
	Night	38% 7% 11% 18% 19% 7%	108285
Seeing	Day	15% 10% 24% 25% 18% 8%	15797
	Night	15% 8% 25% 32% 17% 2	25933

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% 5% 2 5% 4 3 3 2 4 7% 49%	2890
	11th to 20th	Day	12% 5% 2 5% 3 3 4 3 4 6% 53%	2840
	21st to end	Day	16% 8% 2 6% 4 3 4 3 4 5% 43%	3124
February	1st to 10th	Day	16% 7% 3 6% 4 4 4 3 5% 6% 42%	1710
	11th to 20th	Day	20% 5% 3 5% 3 3 4 3 4 6% 44%	1713
	21st to end	Day	18% 8% 2 6% 4 4 3 4 4 6% 41%	1727
March	1st to 10th	Day	21% 9% 3 7% 4 3 4 3 4 6% 36%	3435
	11th to 20th	Day	10% 4 1 5% 3 3 3 3 5% 7% 54%	3480
	21st to end	Day	18% 7% 3 6% 4 3 3 3 4 5% 44%	3815
April	1st to 10th	Day	10% 4 2 4 4 4 4 4 6% 7% 52%	2186
	11th to 20th	Day	10% 5% 2 5% 3 4 4 4 6% 7% 50%	2254
	21st to end	Day	10% 5% 2 5% 4 4 4 3 6% 7% 50%	2280
May	1st to 10th	Day	9% 6% 3 8% 5% 5% 5% 4 6% 10% 37%	3988
	11th to 20th	Day	15% 8% 3 7% 5% 5% 4 4 6% 7% 36%	4081
	21st to end	Day	7% 4 2 6% 4 5% 5% 4 7% 10% 46%	4476
June	1st to 10th	Day	11% 7% 3 6% 6% 5% 6% 5% 7% 9% 37%	2470
	11th to 20th	Day	9% 4 2 6% 6% 5% 7% 5% 8% 9% 41%	2470
	21st to end	Day	7% 5% 2 7% 6% 6% 7% 6% 8% 11% 34%	2470
July	1st to 10th	Day	8% 6% 2 7% 7% 7% 7% 6% 9% 11% 30%	4120
	11th to 20th	Day	9% 7% 3 9% 7% 7% 7% 6% 8% 11% 27%	4120
	21st to end	Day	9% 8% 3 9% 7% 6% 7% 7% 9% 11% 25%	4466
August	1st to 10th	Day	21% 10% 3 8% 7% 7% 6% 5% 7% 8% 19%	4104
	11th to 20th	Day	10% 6% 3 7% 5% 6% 6% 5% 7% 11% 32%	3889
	21st to end	Day	7% 4 2 6% 5% 5% 5% 4 7% 10% 45%	4180
September	1st to 10th	Day	9% 5% 2 7% 5% 6% 6% 4 6% 8% 41%	2280
	11th to 20th	Day	13% 8% 3 6% 4 5% 5% 4 5% 6% 41%	2119
	21st to end	Day	15% 7% 3 6% 5% 5% 4 3 6% 8% 38%	2062
October	1st to 10th	Day	13% 7% 3 6% 3 4 3 3 4 7% 47%	1900
	11th to 20th	Day	10% 5% 2 4 3 3 3 2 5% 6% 56%	1900
	21st to end	Day	10% 6% 2 4 3 3 3 3 4 6% 57%	2090
November	1st to 10th	Day	12% 6% 2 5% 3 4 4 3 5% 5% 54%	1957
	11th to 20th	Day	14% 6% 2 5% 3 2 3 2 5% 7% 51%	2000
	21st to end	Day	12% 6% 2 6% 3 3 3 3 4 6% 51%	1832
December	1st to 10th	Day	11% 5% 2 6% 4 4 4 3 4 5% 52%	2930
	11th to 20th	Day	15% 7% 2 6% 4 3 3 2 5% 6% 47%	3373
	21st to end	Day	15% 7% 3 6% 4 3 4 3 5% 6% 45%	4466
January	1st to 10th	Night	15% 6% 2 5% 3 3 4 3 4 6% 48%	4188
	11th to 20th	Night	12% 6% 3 7% 5% 4 4 4 5% 6% 43%	4120
	21st to end	Night	15% 8% 3 6% 4 3 4 3 5% 5% 44%	4532
February	1st to 10th	Night	17% 7% 3 5% 4 3 4 3 5% 5% 45%	2470
	11th to 20th	Night	18% 7% 2 7% 4 4 3 3 4 6% 43%	2347
	21st to end	Night	15% 5% 3 6% 4 4 4 4 6% 5% 44%	1727
March	1st to 10th	Night	25% 9% 3 7% 4 4 3 3 4 5% 33%	3418
	11th to 20th	Night	12% 5% 2 6% 3 3 5% 3 5% 7% 48%	3480
	21st to end	Night	16% 4 2 5% 3 4 4 4 6% 6% 47%	3817
April	1st to 10th	Night	12% 4 2 4 4 3 4 4 5% 7% 51%	1992
	11th to 20th	Night	10% 5% 2 6% 4 4 4 3 5% 6% 51%	1875
	21st to end	Night	9% 4 2 5% 4 4 4 3 7% 8% 50%	1900
May	1st to 10th	Night	7% 6% 3 7% 5% 4 5% 4 7% 10% 43%	2922
	11th to 20th	Night	13% 8% 3 8% 5% 4 5% 3 6% 7% 38%	2812
	21st to end	Night	6% 5% 2 5% 4 5% 5% 5% 8% 10% 45%	3079
June	1st to 10th	Night	10% 7% 2 8% 5% 5% 4 5% 7% 12% 35%	1710
	11th to 20th	Night	10% 5% 3 5% 5% 6% 6% 4 6% 9% 41%	1710
	21st to end	Night	8% 6% 2 6% 6% 6% 6% 6% 8% 12% 36%	1710
July	1st to 10th	Night	10% 8% 3 9% 5% 6% 7% 5% 8% 10% 29%	2840
	11th to 20th	Night	13% 7% 3 8% 5% 5% 6% 5% 8% 11% 30%	2840
	21st to end	Night	13% 9% 3 9% 7% 6% 6% 5% 7% 8% 25%	3087
August	1st to 10th	Night	20% 8% 3 9% 5% 5% 5% 4 6% 9% 25%	2825
	11th to 20th	Night	9% 7% 3 8% 6% 5% 5% 6% 7% 10% 34%	2907
	21st to end	Night	7% 5% 2 5% 4 4 5% 4 8% 10% 46%	3476
September	1st to 10th	Night	9% 5% 2 6% 5% 5% 5% 4 7% 10% 42%	1900
	11th to 20th	Night	13% 6% 2 7% 5% 5% 5% 4 5% 6% 41%	2057
	21st to end	Night	16% 7% 3 6% 4 5% 4 3 6% 6% 40%	2117
October	1st to 10th	Night	14% 6% 3 5% 3 3 3 2 5% 7% 49%	2280
	11th to 20th	Night	11% 5% 1 5% 3 3 3 3 4 5% 57%	2280
	21st to end	Night	10% 4 2 5% 3 3 3 3 4 5% 57%	2508
November	1st to 10th	Night	12% 6% 2 5% 3 3 3 3 4 5% 54%	2341
	11th to 20th	Night	15% 7% 2 4 3 3 3 3 5% 6% 49%	2400
	21st to end	Night	13% 5% 1 5% 3 4 4 3 5% 7% 50%	2565
December	1st to 10th	Night	12% 6% 2 4 3 3 3 3 4 6% 53%	4250
	11th to 20th	Night	15% 7% 3 7% 4 5% 4 3 4 5% 43%	4822
	21st to end	Night	14% 6% 3 6% 4 4 4 3 5% 6% 46%	6490

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	36% 4 7% 23% 24% 6%	2891
	11th to 20th	Day	34% 4 5% 20% 27% 10%	2840
	21st to end	Day	43% 5% 6% 15% 22% 9%	3124
February	1st to 10th	Day	43% 4 10% 19% 19% 5%	1710
	11th to 20th	Day	42% 4 6% 17% 23% 7%	1722
	21st to end	Day	44% 5% 9% 17% 17% 8%	1727
March	1st to 10th	Day	50% 5% 7% 15% 15% 8%	3435
	11th to 20th	Day	29% 5% 9% 16% 28% 12%	3480
	21st to end	Day	43% 5% 6% 20% 20% 6%	3815
April	1st to 10th	Day	30% 6% 10% 21% 26% 7%	2186
	11th to 20th	Day	32% 7% 10% 20% 22% 9%	2254
	21st to end	Day	33% 7% 11% 23% 22% 5%	2280
May	1st to 10th	Day	40% 10% 16% 20% 12% 2	4024
	11th to 20th	Day	46% 8% 10% 20% 16% 1	4085
	21st to end	Day	30% 9% 16% 21% 21% 3	4489
June	1st to 10th	Day	40% 9% 15% 21% 13% 1	2470
	11th to 20th	Day	36% 10% 17% 22% 13% 3	2470
	21st to end	Day	38% 12% 16% 19% 12% 2	2470
July	1st to 10th	Day	43% 11% 18% 20% 7% 2	4055
	11th to 20th	Day	46% 14% 22% 14% 4 1	4051
	21st to end	Day	47% 14% 15% 15% 8% 1	4324
August	1st to 10th	Day	60% 9% 15% 10% 5%	4091
	11th to 20th	Day	43% 11% 13% 21% 12%	3928
	21st to end	Day	34% 7% 15% 30% 13% 1	4180
September	1st to 10th	Day	39% 9% 15% 17% 15% 5%	2280
	11th to 20th	Day	43% 8% 11% 14% 20% 5%	2119
	21st to end	Day	44% 7% 10% 18% 17% 4	2062
October	1st to 10th	Day	36% 4 7% 20% 26% 7%	3160
	11th to 20th	Day	20% 2 6% 18% 26% 27%	3140
	21st to end	Day	26% 3 5% 22% 27% 17%	3428
November	1st to 10th	Day	33% 5% 7% 19% 28% 9%	1957
	11th to 20th	Day	34% 5% 7% 18% 26% 9%	2000
	21st to end	Day	35% 4 8% 21% 24% 9%	1832
December	1st to 10th	Day	36% 4 7% 16% 24% 13%	2930
	11th to 20th	Day	39% 4 12% 20% 20% 6%	3370
	21st to end	Day	40% 4 10% 21% 22% 2	4466
January	1st to 10th	Night	36% 5% 8% 19% 26% 6%	4188
	11th to 20th	Night	40% 6% 8% 16% 23% 6%	4120
	21st to end	Night	41% 6% 6% 14% 25% 8%	4532
February	1st to 10th	Night	41% 4 8% 17% 22% 7%	2470
	11th to 20th	Night	44% 4 7% 15% 22% 8%	2349
	21st to end	Night	39% 5% 9% 17% 20% 9%	1727
March	1st to 10th	Night	54% 6% 8% 12% 14% 6%	3418
	11th to 20th	Night	34% 5% 9% 12% 24% 16%	3480
	21st to end	Night	36% 6% 9% 22% 20% 6%	3817
April	1st to 10th	Night	33% 6% 11% 18% 24% 9%	1992
	11th to 20th	Night	32% 6% 11% 21% 20% 10%	1875
	21st to end	Night	31% 7% 12% 23% 21% 5%	1900
May	1st to 10th	Night	35% 10% 18% 22% 13% 3	2951
	11th to 20th	Night	43% 8% 12% 21% 15% 1	2813
	21st to end	Night	30% 10% 18% 23% 17% 2	3087
June	1st to 10th	Night	39% 11% 16% 23% 10% 1	1710
	11th to 20th	Night	38% 9% 16% 24% 11% 1	1710
	21st to end	Night	39% 11% 18% 20% 10% 2	1710
July	1st to 10th	Night	47% 13% 17% 16% 5% 1	2795
	11th to 20th	Night	45% 13% 26% 11% 4 1	2786
	21st to end	Night	54% 10% 13% 16% 7%	2988
August	1st to 10th	Night	55% 9% 20% 12% 3	2814
	11th to 20th	Night	41% 11% 20% 20% 6% 1	2934
	21st to end	Night	31% 8% 13% 33% 13% 1	3476
September	1st to 10th	Night	36% 11% 15% 17% 15% 5%	1900
	11th to 20th	Night	42% 8% 12% 16% 17% 4	2057
	21st to end	Night	45% 8% 11% 18% 14% 4	2117
October	1st to 10th	Night	37% 4 8% 21% 24% 6%	3800
	11th to 20th	Night	21% 3 5% 15% 26% 30%	3779
	21st to end	Night	26% 4 6% 23% 25% 17%	4120
November	1st to 10th	Night	33% 5% 7% 17% 26% 12%	2341
	11th to 20th	Night	36% 4 8% 14% 27% 11%	2400
	21st to end	Night	34% 4 8% 20% 25% 8%	2565
December	1st to 10th	Night	33% 4 7% 14% 30% 12%	4250
	11th to 20th	Night	44% 4 10% 15% 18% 8%	4824
	21st to end	Night	39% 4 9% 22% 23% 2	6490

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	20% 24% 36% 16% 2	288
	11th to 20th	Day	17% 23% 36% 19% 4	270
	21st to end	Day	21% 26% 35% 15% 4	297
February	1st to 10th	Day	19% 22% 37% 19% 3	270
	11th to 20th	Day	33% 18% 35% 11% 3	292
	21st to end	Day	21% 21% 35% 18% 4 1	382
March	1st to 10th	Day	18% 19% 32% 23% 8% 1	460
	11th to 20th	Day	18% 22% 33% 20% 7% 1	460
	21st to end	Day	20% 17% 34% 21% 7% 1	506
April	1st to 10th	Day	18% 18% 32% 21% 9% 2	460
	11th to 20th	Day	11% 17% 30% 23% 14% 6%	452
	21st to end	Day	12% 12% 28% 25% 18% 4	460
May	1st to 10th	Day	10% 16% 30% 24% 15% 5%	463
	11th to 20th	Day	13% 7% 19% 30% 22% 9%	487
	21st to end	Day	14% 4 19% 26% 23% 14%	529
June	1st to 10th	Day	13% 3 18% 32% 25% 9%	490
	11th to 20th	Day	11% 4 15% 28% 24% 17%	490
	21st to end	Day	9% 2 15% 29% 29% 16%	490
July	1st to 10th	Day	9% 2 11% 22% 36% 19%	485
	11th to 20th	Day	10% 2 9% 25% 38% 16%	484
	21st to end	Day	5% 3 12% 29% 38% 13%	532
August	1st to 10th	Day	15% 4 12% 24% 27% 17%	486
	11th to 20th	Day	13% 2 10% 25% 28% 23%	479
	21st to end	Day	12% 2 12% 25% 29% 20%	539
September	1st to 10th	Day	10% 2 15% 28% 26% 20%	490
	11th to 20th	Day	16% 4 15% 26% 28% 12%	490
	21st to end	Day	19% 3 20% 31% 19% 9%	490
October	1st to 10th	Day	15% 9% 20% 28% 17% 11%	490
	11th to 20th	Day	12% 10% 22% 32% 18% 6%	490
	21st to end	Day	12% 9% 26% 28% 21% 5%	539
November	1st to 10th	Day	16% 9% 26% 29% 16% 3	495
	11th to 20th	Day	17% 13% 34% 25% 8% 3	500
	21st to end	Day	14% 15% 29% 26% 14% 2	332
December	1st to 10th	Day	20% 16% 42% 15% 8%	300
	11th to 20th	Day	19% 16% 34% 21% 8% 2	300
	21st to end	Day	21% 18% 37% 15% 8% 2	330
January	1st to 10th	Night	18% 15% 33% 26% 7%	785
	11th to 20th	Night	17% 13% 31% 33% 7%	760
	21st to end	Night	19% 14% 35% 29% 3	836
February	1st to 10th	Night	20% 13% 35% 28% 5%	760
	11th to 20th	Night	22% 16% 37% 23% 2	743
	21st to end	Night	18% 14% 38% 27% 3	628
March	1st to 10th	Night	18% 12% 36% 29% 5% 1	760
	11th to 20th	Night	16% 13% 38% 25% 7% 1	760
	21st to end	Night	16% 14% 34% 28% 8%	836
April	1st to 10th	Night	14% 17% 34% 28% 7%	760
	11th to 20th	Night	12% 13% 33% 31% 11% 1	751
	21st to end	Night	12% 9% 35% 37% 8% 1	760
May	1st to 10th	Night	8% 9% 33% 36% 14%	642
	11th to 20th	Night	13% 4 28% 38% 16% 1	561
	21st to end	Night	10% 3 15% 40% 28% 4	617
June	1st to 10th	Night	11% 2 17% 46% 21% 2	570
	11th to 20th	Night	11% 4 16% 34% 29% 6%	570
	21st to end	Night	9% 2 18% 38% 30% 4	570
July	1st to 10th	Night	10% 1 11% 38% 36% 4	555
	11th to 20th	Night	9% 1 9% 36% 39% 5%	552
	21st to end	Night	7% 1 10% 43% 35% 4	624
August	1st to 10th	Night	14% 1 10% 33% 38% 4	567
	11th to 20th	Night	12% 2 11% 33% 35% 6%	634
	21st to end	Night	12% 2 12% 33% 35% 6%	836
September	1st to 10th	Night	11% 2 13% 35% 35% 4	760
	11th to 20th	Night	16% 2 14% 33% 30% 5%	760
	21st to end	Night	20% 5% 16% 34% 22% 3	760
October	1st to 10th	Night	17% 4 18% 29% 27% 4	760
	11th to 20th	Night	13% 6% 27% 31% 21% 2	760
	21st to end	Night	12% 7% 25% 33% 20% 3	836
November	1st to 10th	Night	14% 8% 24% 35% 17% 3	780
	11th to 20th	Night	19% 9% 29% 30% 13% 1	800
	21st to end	Night	15% 9% 29% 29% 16% 1	800
December	1st to 10th	Night	18% 13% 29% 32% 8% 1	800
	11th to 20th	Night	18% 10% 28% 33% 11% 1	800
	21st to end	Night	20% 13% 26% 32% 9%	880

Page generated at 2025-01-04 03:24:01. Version ac07

Copyright © 2025 Attilla Danko.