Colbeck Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Colbeck Observatory clear sky chart from 2005-11-06 to 2024-11-04.

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	14% 12% 4 10% 6% 5% 5% 4 6% 7% 29%	102070
	Night	13% 12% 5% 11% 6% 5% 4 4 5% 6% 30%	96854
Transparency	Day	53% 6% 11% 19% 10% 1	105658
	Night	53% 6% 11% 19% 10% 1	101356
Seeing	Day	19% 14% 30% 22% 11% 4	14962
	Night	19% 14% 31% 25% 10% 1	23820

By Month

Percentage Cloud Cover NE (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	13% 18% 11% 17% 7% 4 3 3 4 5% 16%	2433
	11th to 20th	Day	9% 21% 10% 22% 10% 10% 5% 2 2 2 7%	2837
	21st to end	Day	16% 21% 9% 19% 6% 4 4 3 3 4 11%	3124
February	1st to 10th	Day	12% 18% 7% 16% 12% 7% 5% 3 3 3 12%	1710
	11th to 20th	Day	12% 14% 7% 18% 10% 6% 4 3 6% 5% 15%	1663
	21st to end	Day	15% 17% 7% 12% 9% 6% 5% 3 5% 4 18%	1498
March	1st to 10th	Day	16% 16% 4 12% 6% 5% 4 3 4 4 26%	3396
	11th to 20th	Day	9% 14% 10% 13% 6% 6% 5% 4 4 5% 25%	3480
	21st to end	Day	14% 13% 5% 9% 5% 4 5% 4 4 6% 30%	3815
April	1st to 10th	Day	15% 16% 4 10% 5% 5% 5% 3 5% 6% 26%	2208
	11th to 20th	Day	18% 12% 3 6% 4 5% 4 3 5% 6% 34%	2389
	21st to end	Day	20% 12% 5% 7% 4 3 4 3 5% 6% 31%	2470
May	1st to 10th	Day	17% 9% 3 8% 5% 4 4 4 5% 7% 33%	4108
	11th to 20th	Day	17% 9% 3 8% 5% 5% 5% 4 6% 8% 31%	4292
	21st to end	Day	14% 6% 2 6% 4 4 3 3 5% 7% 46%	4837
June	1st to 10th	Day	14% 8% 3 7% 4 5% 5% 5% 7% 7% 35%	2660
	11th to 20th	Day	12% 7% 2 6% 4 4 5% 5% 7% 8% 39%	2827
	21st to end	Day	16% 6% 2 6% 5% 5% 4 4 7% 8% 37%	2850
July	1st to 10th	Day	11% 6% 3 7% 6% 5% 6% 5% 8% 9% 34%	4760
	11th to 20th	Day	10% 6% 2 6% 5% 4 6% 4 7% 8% 41%	4448
	21st to end	Day	10% 6% 2 7% 5% 5% 5% 4 7% 9% 39%	4466
August	1st to 10th	Day	15% 7% 3 7% 5% 5% 6% 5% 6% 8% 34%	4104
	11th to 20th	Day	13% 8% 3 8% 5% 6% 6% 5% 7% 10% 29%	4044
	21st to end	Day	9% 6% 3 7% 5% 5% 5% 5% 7% 8% 40%	4422
September	1st to 10th	Day	14% 7% 3 8% 5% 5% 4 4 6% 8% 37%	2280
	11th to 20th	Day	12% 8% 2 6% 4 5% 4 4 6% 8% 41%	2109
	21st to end	Day	16% 8% 3 7% 5% 5% 5% 4 8% 8% 31%	2086
October	1st to 10th	Day	17% 11% 3 8% 5% 5% 5% 4 5% 6% 31%	1900
	11th to 20th	Day	21% 14% 4 9% 5% 5% 4 4 4 6% 24%	1900
	21st to end	Day	24% 18% 4 8% 5% 4 4 3 5% 6% 18%	2080
November	1st to 10th	Day	14% 17% 4 8% 6% 4 5% 4 4 7% 26%	1636
	11th to 20th	Day	14% 17% 6% 10% 7% 6% 5% 3 6% 7% 21%	1520
	21st to end	Day	16% 20% 7% 13% 6% 4 4 4 5% 5% 15%	1520
December	1st to 10th	Day	13% 25% 10% 17% 6% 4 4 4 4 4 9%	1520
	11th to 20th	Day	16% 21% 7% 16% 6% 4 4 3 4 5% 14%	1906
	21st to end	Day	22% 22% 10% 17% 6% 4 3 2 4 3 7%	2772
January	1st to 10th	Night	14% 17% 9% 20% 7% 5% 4 3 4 5% 10%	4429
	11th to 20th	Night	12% 13% 9% 22% 12% 10% 6% 3 3 3 7%	4120
	21st to end	Night	17% 16% 8% 18% 8% 5% 5% 3 4 4 13%	4532
February	1st to 10th	Night	12% 17% 7% 13% 10% 6% 5% 4 5% 5% 16%	2470
	11th to 20th	Night	12% 12% 7% 16% 8% 6% 5% 4 5% 6% 19%	2403
	21st to end	Night	13% 13% 5% 14% 8% 5% 5% 4 6% 7% 22%	1954
March	1st to 10th	Night	13% 11% 5% 9% 6% 5% 5% 4 6% 6% 30%	3443
	11th to 20th	Night	9% 12% 6% 11% 6% 4 5% 4 5% 6% 32%	3479
	21st to end	Night	14% 9% 4 10% 4 5% 4 4 5% 5% 35%	3817
April	1st to 10th	Night	17% 14% 4 9% 5% 4 4 3 4 6% 29%	1971
	11th to 20th	Night	15% 11% 4 7% 5% 5% 4 3 6% 5% 36%	1757
	21st to end	Night	14% 11% 3 9% 6% 5% 4 4 5% 5% 33%	1710
May	1st to 10th	Night	14% 9% 2 6% 5% 4 4 4 5% 6% 41%	2833
	11th to 20th	Night	15% 9% 3 6% 4 5% 5% 4 5% 6% 39%	2601
	21st to end	Night	9% 6% 2 6% 4 3 4 3 6% 7% 50%	2738
June	1st to 10th	Night	12% 6% 3 7% 5% 4 5% 4 5% 8% 41%	1520
	11th to 20th	Night	9% 6% 2 7% 4 5% 6% 4 7% 9% 41%	1346
	21st to end	Night	13% 6% 2 6% 5% 4 3 4 5% 8% 44%	1330
July	1st to 10th	Night	6% 7% 2 6% 4 4 4 4 6% 7% 51%	2210
	11th to 20th	Night	10% 7% 2 5% 4 3 3 4 5% 6% 52%	2506
	21st to end	Night	6% 7% 2 6% 4 4 5% 4 6% 7% 48%	3087
August	1st to 10th	Night	11% 7% 2 6% 4 4 4 3 5% 6% 47%	2825
	11th to 20th	Night	12% 8% 2 6% 4 4 4 4 5% 7% 45%	2785
	21st to end	Night	11% 6% 3 7% 5% 4 4 3 4 7% 47%	3188
September	1st to 10th	Night	9% 6% 2 8% 3 4 5% 4 5% 7% 47%	1900
	11th to 20th	Night	11% 5% 2 5% 4 4 3 3 6% 6% 51%	2066
	21st to end	Night	15% 9% 2 7% 4 4 4 3 5% 8% 38%	2092
October	1st to 10th	Night	16% 8% 3 7% 5% 5% 4 3 4 6% 37%	2280
	11th to 20th	Night	18% 12% 4 9% 5% 5% 5% 3 4 6% 29%	2280
	21st to end	Night	18% 13% 4 9% 5% 5% 5% 4 6% 6% 23%	2517
November	1st to 10th	Night	15% 13% 3 9% 6% 5% 4 4 5% 7% 29%	2513
	11th to 20th	Night	14% 15% 5% 9% 6% 5% 5% 4 7% 7% 23%	2660
	21st to end	Night	16% 16% 6% 11% 6% 5% 4 4 6% 7% 19%	2660
December	1st to 10th	Night	16% 19% 8% 16% 7% 5% 4 3 4 5% 12%	2660
	11th to 20th	Night	13% 21% 8% 15% 7% 4 5% 3 5% 5% 15%	3288
	21st to end	Night	22% 21% 8% 18% 6% 4 4 3 4 4 7%	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	72% 5% 8% 11% 4	2434
	11th to 20th	Day	85% 3 4 5% 3 1	2837
	21st to end	Day	77% 5% 6% 7% 4 1	3124
February	1st to 10th	Day	76% 4 6% 11% 3 1	1710
	11th to 20th	Day	70% 4 7% 12% 5% 1	1672
	21st to end	Day	68% 5% 8% 12% 6% 1	1498
March	1st to 10th	Day	61% 5% 10% 14% 9% 1	3399
	11th to 20th	Day	62% 4 9% 18% 6% 1	3480
	21st to end	Day	54% 5% 11% 18% 10% 2	3815
April	1st to 10th	Day	60% 4 8% 18% 9% 1	2208
	11th to 20th	Day	51% 6% 9% 20% 14% 1	2389
	21st to end	Day	53% 5% 10% 18% 11% 2	2470
May	1st to 10th	Day	49% 6% 11% 19% 13% 2	4120
	11th to 20th	Day	48% 10% 13% 21% 8% 1	4296
	21st to end	Day	38% 6% 12% 22% 17% 4	4837
June	1st to 10th	Day	45% 7% 11% 22% 14% 1	2660
	11th to 20th	Day	39% 8% 12% 24% 16% 1	2827
	21st to end	Day	42% 7% 13% 24% 13%	2850
July	1st to 10th	Day	44% 8% 13% 20% 15% 1	4686
	11th to 20th	Day	38% 7% 11% 32% 12% 1	4371
	21st to end	Day	39% 8% 12% 22% 18% 1	4324
August	1st to 10th	Day	46% 7% 12% 23% 12% 1	4091
	11th to 20th	Day	48% 8% 13% 22% 8%	4083
	21st to end	Day	39% 7% 12% 30% 11% 1	4422
September	1st to 10th	Day	44% 6% 13% 24% 10% 2	2280
	11th to 20th	Day	39% 6% 12% 28% 14% 1	2109
	21st to end	Day	48% 8% 13% 22% 8% 1	2086
October	1st to 10th	Day	47% 7% 11% 22% 12% 1	3160
	11th to 20th	Day	49% 5% 11% 20% 15%	3140
	21st to end	Day	60% 5% 12% 18% 6%	3406
November	1st to 10th	Day	57% 6% 12% 17% 7% 1	1636
	11th to 20th	Day	63% 6% 11% 12% 7% 1	1520
	21st to end	Day	69% 6% 11% 12% 2	1520
December	1st to 10th	Day	76% 6% 9% 7% 2	1520
	11th to 20th	Day	72% 6% 10% 9% 4	1906
	21st to end	Day	82% 6% 5% 6% 1	2772
January	1st to 10th	Night	75% 6% 9% 8% 2	4429
	11th to 20th	Night	83% 4 5% 4 3 1	4120
	21st to end	Night	74% 5% 9% 9% 3 1	4532
February	1st to 10th	Night	67% 5% 10% 14% 3 1	2470
	11th to 20th	Night	64% 5% 10% 14% 7%	2405
	21st to end	Night	60% 4 13% 14% 8% 1	1954
March	1st to 10th	Night	52% 7% 12% 20% 8% 1	3453
	11th to 20th	Night	50% 6% 12% 20% 10% 2	3480
	21st to end	Night	49% 5% 9% 22% 14% 2	3817
April	1st to 10th	Night	57% 5% 8% 18% 12% 1	1971
	11th to 20th	Night	48% 6% 8% 21% 15% 2	1757
	21st to end	Night	52% 5% 10% 16% 15% 2	1710
May	1st to 10th	Night	43% 7% 10% 20% 15% 5%	2840
	11th to 20th	Night	43% 9% 13% 23% 11% 2	2602
	21st to end	Night	32% 8% 13% 23% 22% 3	2739
June	1st to 10th	Night	40% 5% 12% 24% 17% 2	1520
	11th to 20th	Night	37% 6% 13% 24% 18% 1	1346
	21st to end	Night	38% 7% 11% 28% 15% 1	1330
July	1st to 10th	Night	33% 5% 14% 24% 19% 4	2175
	11th to 20th	Night	33% 5% 11% 34% 16% 1	2461
	21st to end	Night	34% 8% 13% 29% 15% 2	2988
August	1st to 10th	Night	37% 6% 12% 27% 16% 2	2814
	11th to 20th	Night	38% 6% 14% 28% 13% 1	2812
	21st to end	Night	37% 6% 12% 31% 14% 1	3188
September	1st to 10th	Night	35% 8% 13% 29% 14% 2	1900
	11th to 20th	Night	32% 5% 13% 30% 20% 1	2066
	21st to end	Night	45% 6% 13% 25% 11%	2092
October	1st to 10th	Night	39% 5% 9% 25% 21% 1	3800
	11th to 20th	Night	48% 5% 12% 21% 14% 1	3779
	21st to end	Night	48% 6% 15% 23% 8%	4141
November	1st to 10th	Night	53% 6% 12% 19% 9% 1	2513
	11th to 20th	Night	57% 6% 13% 16% 6% 2	2660
	21st to end	Night	63% 6% 14% 13% 3 1	2660
December	1st to 10th	Night	74% 5% 11% 8% 2	2660
	11th to 20th	Night	71% 5% 11% 11% 3	3288
	21st to end	Night	81% 6% 6% 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	22% 23% 34% 17% 4	180
	11th to 20th	Day	21% 26% 36% 13% 4	269
	21st to end	Day	21% 25% 35% 16% 4	297
February	1st to 10th	Day	24% 27% 34% 10% 4	270
	11th to 20th	Day	20% 27% 41% 10% 1	270
	21st to end	Day	30% 29% 30% 10%	225
March	1st to 10th	Day	22% 19% 39% 14% 6%	435
	11th to 20th	Day	21% 18% 38% 16% 6% 1	460
	21st to end	Day	27% 15% 34% 18% 7% 1	506
April	1st to 10th	Day	24% 18% 35% 17% 7%	460
	11th to 20th	Day	30% 17% 24% 16% 9% 3	452
	21st to end	Day	26% 15% 31% 18% 7% 2	460
May	1st to 10th	Day	23% 13% 28% 22% 11% 2	463
	11th to 20th	Day	18% 11% 29% 25% 12% 5%	487
	21st to end	Day	15% 10% 27% 28% 15% 5%	529
June	1st to 10th	Day	15% 13% 29% 28% 13% 2	490
	11th to 20th	Day	14% 9% 31% 30% 13% 3	657
	21st to end	Day	15% 10% 32% 29% 11% 3	680
July	1st to 10th	Day	12% 8% 27% 28% 20% 5%	671
	11th to 20th	Day	15% 7% 25% 30% 17% 7%	520
	21st to end	Day	11% 4 27% 35% 16% 6%	532
August	1st to 10th	Day	14% 7% 23% 25% 22% 9%	486
	11th to 20th	Day	14% 4 23% 27% 19% 13%	479
	21st to end	Day	14% 7% 27% 25% 18% 9%	539
September	1st to 10th	Day	14% 10% 27% 23% 16% 10%	490
	11th to 20th	Day	12% 6% 21% 25% 23% 12%	490
	21st to end	Day	15% 13% 27% 23% 16% 6%	490
October	1st to 10th	Day	22% 16% 25% 20% 13% 5%	490
	11th to 20th	Day	23% 20% 33% 17% 5% 2	490
	21st to end	Day	32% 16% 28% 19% 5%	529
November	1st to 10th	Day	25% 22% 31% 16% 5% 1	248
	11th to 20th	Day	25% 20% 38% 11% 4 2	180
	21st to end	Day	24% 21% 40% 13% 2	180
December	1st to 10th	Day	26% 31% 29% 14% 1	180
	11th to 20th	Day	26% 33% 27% 11% 2 1	180
	21st to end	Day	28% 27% 32% 10% 2 1	198
January	1st to 10th	Night	21% 23% 34% 17% 5% 1	760
	11th to 20th	Night	27% 19% 31% 19% 3 1	760
	21st to end	Night	16% 16% 38% 23% 6%	836
February	1st to 10th	Night	21% 22% 36% 19% 2	760
	11th to 20th	Night	20% 19% 37% 20% 3	743
	21st to end	Night	20% 22% 37% 19% 3	628
March	1st to 10th	Night	16% 17% 41% 20% 5%	760
	11th to 20th	Night	18% 19% 39% 19% 5% 1	760
	21st to end	Night	20% 13% 35% 23% 8% 1	836
April	1st to 10th	Night	23% 15% 37% 21% 4	760
	11th to 20th	Night	21% 15% 32% 21% 9% 1	633
	21st to end	Night	22% 11% 31% 27% 9%	570
May	1st to 10th	Night	18% 9% 28% 32% 11% 2	570
	11th to 20th	Night	17% 7% 32% 31% 12% 1	441
	21st to end	Night	11% 7% 28% 38% 16%	411
June	1st to 10th	Night	14% 7% 33% 34% 12%	380
	11th to 20th	Night	10% 8% 31% 38% 14%	380
	21st to end	Night	13% 8% 29% 34% 16%	380
July	1st to 10th	Night	7% 4 20% 48% 20% 1	370
	11th to 20th	Night	10% 4 28% 35% 22% 1	395
	21st to end	Night	9% 4 24% 41% 20% 2	624
August	1st to 10th	Night	11% 3 20% 37% 27% 2	567
	11th to 20th	Night	9% 3 20% 37% 27% 4	564
	21st to end	Night	14% 5% 25% 28% 26% 2	665
September	1st to 10th	Night	11% 7% 24% 32% 19% 6%	760
	11th to 20th	Night	12% 7% 21% 32% 22% 6%	760
	21st to end	Night	19% 9% 23% 29% 16% 4	760
October	1st to 10th	Night	19% 9% 28% 27% 13% 3	760
	11th to 20th	Night	23% 16% 28% 24% 8% 1	760
	21st to end	Night	24% 17% 33% 22% 4	836
November	1st to 10th	Night	22% 16% 31% 23% 7% 1	755
	11th to 20th	Night	21% 21% 33% 18% 6% 1	760
	21st to end	Night	24% 17% 35% 20% 4	760
December	1st to 10th	Night	26% 21% 33% 17% 3 1	760
	11th to 20th	Night	20% 22% 39% 15% 4	760
	21st to end	Night	28% 20% 33% 17% 2	836

Page generated at 2024-11-01 22:47:31. Version ac07

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