Carvel Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carvel Observatory clear sky chart from 2005-11-06 to 2025-04-26.

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	10% 9% 3 9% 6% 5% 5% 4 6% 8% 35%	117737
	Night	9% 11% 4 10% 6% 5% 5% 4 6% 7% 32%	119571
Transparency	Day	45% 7% 17% 22% 8% 1	117477
	Night	49% 7% 15% 20% 9% 1	119477
Seeing	Day	13% 7% 24% 31% 18% 6%	16407
	Night	14% 6% 27% 35% 16% 2	25088

By Month

Percentage Cloud Cover NW (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	4 13% 5% 12% 8% 5% 5% 4 6% 9% 29%	3179
	11th to 20th	Day	5% 9% 4 9% 8% 6% 6% 6% 8% 9% 31%	3159
	21st to end	Day	8% 13% 4 8% 5% 5% 5% 4 6% 8% 36%	3842
February	1st to 10th	Day	9% 13% 5% 12% 7% 7% 7% 4 7% 8% 22%	1600
	11th to 20th	Day	6% 12% 5% 13% 7% 6% 7% 4 6% 7% 28%	1670
	21st to end	Day	3 14% 5% 11% 9% 7% 6% 5% 7% 6% 26%	1572
March	1st to 10th	Day	4 11% 4 10% 7% 6% 5% 4 6% 10% 32%	4518
	11th to 20th	Day	6% 12% 4 10% 6% 4 4 4 6% 8% 37%	4901
	21st to end	Day	10% 14% 5% 14% 6% 6% 5% 4 6% 7% 23%	5649
April	1st to 10th	Day	7% 14% 3 9% 6% 5% 5% 5% 6% 9% 31%	2473
	11th to 20th	Day	11% 10% 4 8% 6% 6% 5% 5% 7% 8% 31%	2570
	21st to end	Day	11% 10% 3 8% 6% 6% 5% 4 6% 7% 32%	2541
May	1st to 10th	Day	16% 10% 3 8% 5% 5% 5% 4 5% 8% 30%	4630
	11th to 20th	Day	11% 10% 4 8% 6% 6% 6% 5% 7% 8% 30%	4694
	21st to end	Day	12% 7% 3 9% 6% 6% 6% 5% 7% 9% 28%	5161
June	1st to 10th	Day	17% 7% 3 7% 6% 5% 5% 4 6% 8% 32%	2850
	11th to 20th	Day	18% 9% 3 8% 7% 6% 7% 4 6% 7% 24%	3016
	21st to end	Day	11% 5% 2 6% 4 6% 6% 4 7% 10% 39%	3040
July	1st to 10th	Day	10% 5% 2 5% 3 4 4 4 6% 7% 50%	4979
	11th to 20th	Day	8% 5% 2 5% 5% 4 5% 4 6% 8% 48%	4740
	21st to end	Day	12% 5% 2 5% 4 4 4 4 6% 9% 44%	5138
August	1st to 10th	Day	13% 5% 2 6% 4 5% 5% 5% 6% 8% 41%	4448
	11th to 20th	Day	10% 6% 2 6% 4 4 5% 5% 7% 10% 42%	4190
	21st to end	Day	12% 5% 2 7% 4 5% 6% 4 8% 9% 40%	4521
September	1st to 10th	Day	12% 6% 3 6% 4 4 4 3 6% 8% 43%	2390
	11th to 20th	Day	14% 7% 2 6% 4 4 4 3 5% 9% 41%	2104
	21st to end	Day	9% 7% 3 8% 5% 5% 5% 3 6% 9% 40%	2090
October	1st to 10th	Day	10% 9% 3 8% 5% 4 5% 4 5% 7% 41%	3320
	11th to 20th	Day	11% 12% 4 7% 4 4 5% 5% 6% 8% 34%	2842
	21st to end	Day	7% 12% 4 9% 5% 6% 5% 4 6% 7% 35%	3101
November	1st to 10th	Day	10% 17% 4 10% 6% 5% 5% 4 6% 7% 25%	1574
	11th to 20th	Day	7% 13% 5% 12% 6% 5% 4 4 5% 7% 33%	1405
	21st to end	Day	6% 11% 5% 15% 6% 7% 5% 4 6% 7% 27%	1400
December	1st to 10th	Day	10% 15% 6% 12% 6% 6% 6% 4 6% 7% 22%	2290
	11th to 20th	Day	8% 13% 5% 13% 8% 6% 6% 4 5% 8% 24%	2642
	21st to end	Day	3 8% 3 9% 6% 5% 5% 4 6% 9% 42%	3498
January	1st to 10th	Night	4 12% 5% 15% 9% 7% 5% 4 5% 7% 27%	6766
	11th to 20th	Night	3 9% 4 11% 8% 7% 6% 5% 7% 6% 34%	6739
	21st to end	Night	7% 14% 4 9% 6% 4 4 3 5% 8% 33%	7159
February	1st to 10th	Night	6% 13% 6% 13% 8% 7% 5% 5% 6% 7% 26%	2800
	11th to 20th	Night	6% 12% 5% 11% 8% 6% 6% 6% 6% 6% 28%	2616
	21st to end	Night	5% 13% 4 11% 7% 6% 6% 4 5% 8% 30%	2055
March	1st to 10th	Night	3 9% 5% 12% 8% 6% 5% 4 6% 9% 32%	5376
	11th to 20th	Night	5% 11% 4 10% 7% 6% 6% 5% 8% 8% 29%	5098
	21st to end	Night	11% 15% 6% 14% 6% 6% 5% 4 5% 6% 24%	5324
April	1st to 10th	Night	8% 10% 3 11% 7% 7% 6% 5% 7% 7% 30%	1926
	11th to 20th	Night	9% 12% 4 12% 7% 5% 7% 4 7% 7% 28%	1781
	21st to end	Night	12% 10% 4 8% 5% 4 5% 5% 6% 9% 33%	1754
May	1st to 10th	Night	21% 10% 4 9% 5% 5% 4 4 5% 5% 27%	2330
	11th to 20th	Night	10% 9% 4 10% 7% 6% 6% 5% 6% 8% 29%	2199
	21st to end	Night	13% 10% 3 9% 5% 6% 7% 5% 7% 8% 26%	2414
June	1st to 10th	Night	18% 8% 4 9% 6% 5% 5% 5% 5% 7% 30%	1330
	11th to 20th	Night	16% 9% 3 9% 6% 8% 7% 6% 7% 8% 20%	1159
	21st to end	Night	12% 6% 2 7% 5% 6% 6% 5% 8% 9% 33%	1140
July	1st to 10th	Night	11% 5% 3 6% 4 5% 4 4 5% 7% 46%	1964
	11th to 20th	Night	10% 6% 2 6% 6% 6% 7% 4 7% 11% 36%	2220
	21st to end	Night	15% 5% 2 6% 4 4 5% 4 7% 8% 40%	2414
August	1st to 10th	Night	15% 6% 3 6% 5% 5% 5% 4 6% 7% 38%	2479
	11th to 20th	Night	13% 7% 3 8% 4 4 5% 4 6% 9% 37%	2643
	21st to end	Night	13% 5% 2 6% 4 4 4 3 6% 9% 43%	3146
September	1st to 10th	Night	12% 6% 2 7% 4 4 4 4 6% 8% 44%	1787
	11th to 20th	Night	12% 7% 3 5% 5% 4 4 5% 6% 8% 42%	2076
	21st to end	Night	11% 7% 3 6% 4 4 5% 4 7% 8% 41%	2090
October	1st to 10th	Night	9% 8% 3 8% 6% 5% 5% 5% 6% 8% 38%	3650
	11th to 20th	Night	10% 8% 2 8% 4 5% 5% 5% 7% 8% 37%	4086
	21st to end	Night	7% 10% 4 9% 6% 5% 5% 4 6% 8% 35%	4457
November	1st to 10th	Night	13% 15% 6% 10% 6% 5% 4 3 6% 7% 25%	2704
	11th to 20th	Night	8% 14% 6% 12% 6% 6% 5% 4 6% 7% 27%	2991
	21st to end	Night	7% 13% 5% 11% 7% 7% 5% 4 6% 7% 28%	3000
December	1st to 10th	Night	10% 17% 5% 11% 6% 5% 5% 4 5% 7% 25%	4890
	11th to 20th	Night	9% 16% 6% 12% 7% 6% 6% 4 5% 7% 22%	5550
	21st to end	Night	3 9% 4 10% 6% 5% 5% 4 6% 7% 42%	7458

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	52% 5% 15% 17% 10% 1	3179
	11th to 20th	Day	47% 6% 11% 13% 21% 2	3180
	21st to end	Day	46% 6% 21% 22% 5%	3842
February	1st to 10th	Day	58% 5% 14% 14% 8% 1	1600
	11th to 20th	Day	53% 7% 13% 18% 8%	1678
	21st to end	Day	53% 7% 13% 19% 7% 1	1572
March	1st to 10th	Day	47% 6% 17% 20% 9%	4518
	11th to 20th	Day	44% 6% 14% 24% 11%	4902
	21st to end	Day	57% 7% 9% 18% 8% 1	5649
April	1st to 10th	Day	47% 9% 15% 20% 7% 1	2473
	11th to 20th	Day	48% 7% 14% 22% 9% 1	2570
	21st to end	Day	48% 6% 15% 22% 7% 2	2541
May	1st to 10th	Day	52% 6% 10% 23% 8% 1	4630
	11th to 20th	Day	47% 9% 12% 24% 8%	4698
	21st to end	Day	48% 8% 17% 17% 9%	5162
June	1st to 10th	Day	49% 6% 16% 21% 7% 1	2850
	11th to 20th	Day	56% 8% 15% 15% 6%	3016
	21st to end	Day	38% 9% 23% 24% 6% 1	3040
July	1st to 10th	Day	32% 7% 16% 32% 13% 1	4902
	11th to 20th	Day	32% 7% 19% 30% 12%	4659
	21st to end	Day	36% 6% 23% 22% 13% 1	4976
August	1st to 10th	Day	38% 8% 21% 32% 2	4430
	11th to 20th	Day	35% 9% 22% 28% 7%	4232
	21st to end	Day	38% 8% 26% 23% 4	4520
September	1st to 10th	Day	39% 7% 20% 25% 7% 2	2390
	11th to 20th	Day	40% 6% 19% 28% 7%	2104
	21st to end	Day	39% 6% 17% 26% 9% 2	2090
October	1st to 10th	Day	42% 7% 23% 22% 5%	3320
	11th to 20th	Day	46% 6% 14% 25% 9%	2842
	21st to end	Day	46% 6% 18% 25% 4	3101
November	1st to 10th	Day	57% 6% 15% 15% 6% 1	1574
	11th to 20th	Day	51% 6% 16% 19% 8%	1405
	21st to end	Day	54% 8% 15% 17% 6% 1	1400
December	1st to 10th	Day	60% 7% 16% 11% 5% 1	2290
	11th to 20th	Day	58% 7% 16% 14% 5%	2644
	21st to end	Day	38% 5% 13% 28% 14% 2	3498
January	1st to 10th	Night	57% 5% 13% 16% 9% 1	6766
	11th to 20th	Night	48% 5% 13% 15% 17% 2	6780
	21st to end	Night	49% 4 19% 19% 7%	7159
February	1st to 10th	Night	57% 5% 12% 17% 8% 1	2800
	11th to 20th	Night	53% 7% 13% 15% 11% 1	2618
	21st to end	Night	51% 6% 11% 21% 10% 1	2055
March	1st to 10th	Night	46% 6% 17% 22% 9%	5376
	11th to 20th	Night	48% 7% 16% 19% 10%	5098
	21st to end	Night	59% 7% 9% 18% 7%	5324
April	1st to 10th	Night	51% 8% 12% 20% 10% 1	1926
	11th to 20th	Night	52% 7% 11% 19% 10% 2	1781
	21st to end	Night	45% 7% 13% 22% 11% 1	1754
May	1st to 10th	Night	56% 6% 7% 20% 10% 1	2330
	11th to 20th	Night	48% 9% 12% 22% 9% 1	2199
	21st to end	Night	52% 7% 16% 14% 9% 1	2414
June	1st to 10th	Night	52% 8% 13% 19% 8% 1	1330
	11th to 20th	Night	58% 9% 16% 14% 3	1159
	21st to end	Night	43% 11% 21% 21% 5% 1	1140
July	1st to 10th	Night	36% 8% 15% 25% 16%	1932
	11th to 20th	Night	40% 10% 17% 25% 8%	2178
	21st to end	Night	38% 9% 19% 24% 9% 1	2337
August	1st to 10th	Night	43% 8% 20% 27% 2	2472
	11th to 20th	Night	42% 9% 20% 21% 8% 1	2667
	21st to end	Night	37% 7% 24% 26% 5%	3146
September	1st to 10th	Night	37% 7% 19% 25% 11% 2	1787
	11th to 20th	Night	39% 6% 16% 28% 9% 2	2076
	21st to end	Night	38% 7% 15% 25% 13% 2	2090
October	1st to 10th	Night	42% 7% 21% 25% 6%	3650
	11th to 20th	Night	42% 7% 14% 30% 7%	4086
	21st to end	Night	44% 7% 21% 22% 6%	4457
November	1st to 10th	Night	58% 6% 11% 19% 6%	2704
	11th to 20th	Night	55% 7% 12% 19% 6% 1	2991
	21st to end	Night	54% 6% 16% 18% 5% 1	3000
December	1st to 10th	Night	59% 7% 14% 14% 5% 1	4890
	11th to 20th	Night	60% 7% 16% 13% 5%	5547
	21st to end	Night	40% 5% 14% 25% 14% 2	7458

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	8% 5% 30% 32% 21% 5%	200
	11th to 20th	Day	13% 8% 27% 31% 16% 8%	200
	21st to end	Day	14% 9% 30% 27% 15% 5%	220
February	1st to 10th	Day	14% 7% 30% 34% 12% 3	200
	11th to 20th	Day	11% 4 38% 31% 14% 3	256
	21st to end	Day	8% 7% 35% 31% 13% 6%	336
March	1st to 10th	Day	13% 8% 27% 32% 19% 2	500
	11th to 20th	Day	10% 6% 31% 33% 14% 5%	500
	21st to end	Day	14% 8% 27% 30% 17% 4	550
April	1st to 10th	Day	9% 14% 32% 29% 12% 4	500
	11th to 20th	Day	14% 11% 24% 28% 17% 6%	492
	21st to end	Day	15% 10% 26% 29% 15% 6%	481
May	1st to 10th	Day	15% 9% 23% 33% 17% 3	582
	11th to 20th	Day	11% 6% 22% 37% 17% 5%	675
	21st to end	Day	17% 6% 20% 31% 19% 7%	734
June	1st to 10th	Day	18% 11% 24% 31% 13% 4	680
	11th to 20th	Day	20% 7% 21% 25% 21% 6%	846
	21st to end	Day	13% 4 19% 31% 25% 8%	870
July	1st to 10th	Day	12% 3 18% 36% 22% 9%	816
	11th to 20th	Day	11% 4 20% 31% 25% 9%	668
	21st to end	Day	10% 6% 16% 30% 26% 11%	739
August	1st to 10th	Day	10% 5% 17% 31% 24% 14%	521
	11th to 20th	Day	9% 5% 23% 33% 22% 7%	477
	21st to end	Day	15% 7% 16% 29% 24% 9%	539
September	1st to 10th	Day	16% 7% 25% 27% 16% 8%	490
	11th to 20th	Day	18% 6% 21% 30% 19% 7%	490
	21st to end	Day	11% 11% 29% 29% 14% 6%	490
October	1st to 10th	Day	14% 6% 25% 33% 16% 5%	402
	11th to 20th	Day	15% 8% 29% 27% 15% 6%	300
	21st to end	Day	14% 14% 33% 25% 11% 3	330
November	1st to 10th	Day	18% 4 33% 29% 13% 3	300
	11th to 20th	Day	13% 5% 37% 29% 13% 2	203
	21st to end	Day	8% 8% 30% 39% 11% 6%	200
December	1st to 10th	Day	13% 8% 29% 34% 12% 5%	200
	11th to 20th	Day	10% 11% 31% 30% 16% 3	200
	21st to end	Day	7% 3 23% 37% 24% 6%	220
January	1st to 10th	Night	12% 7% 32% 34% 14% 2	1000
	11th to 20th	Night	11% 9% 31% 35% 12% 2	1000
	21st to end	Night	15% 11% 34% 28% 12% 1	970
February	1st to 10th	Night	10% 9% 26% 35% 18% 3	800
	11th to 20th	Night	11% 6% 32% 36% 15% 1	784
	21st to end	Night	9% 5% 29% 35% 18% 4	660
March	1st to 10th	Night	10% 5% 30% 37% 17% 2	800
	11th to 20th	Night	12% 5% 29% 37% 16% 2	800
	21st to end	Night	15% 5% 25% 38% 15% 3	880
April	1st to 10th	Night	12% 8% 26% 38% 14% 2	726
	11th to 20th	Night	14% 8% 29% 33% 14% 1	593
	21st to end	Night	16% 6% 27% 36% 14% 1	582
May	1st to 10th	Night	17% 5% 23% 39% 14% 2	380
	11th to 20th	Night	13% 4 25% 39% 18% 1	374
	21st to end	Night	20% 6% 20% 37% 15% 2	411
June	1st to 10th	Night	19% 7% 26% 33% 14% 1	380
	11th to 20th	Night	20% 5% 21% 33% 19% 2	380
	21st to end	Night	14% 4 17% 37% 25% 2	380
July	1st to 10th	Night	14% 4 13% 45% 23% 1	370
	11th to 20th	Night	13% 4 17% 42% 21% 2	368
	21st to end	Night	14% 2 18% 37% 27% 3	416
August	1st to 10th	Night	13% 5% 15% 33% 30% 4	378
	11th to 20th	Night	13% 4 16% 35% 29% 3	457
	21st to end	Night	14% 3 20% 39% 23%	627
September	1st to 10th	Night	16% 3 18% 39% 22% 2	647
	11th to 20th	Night	15% 4 19% 41% 19% 1	760
	21st to end	Night	14% 5% 28% 35% 16% 2	760
October	1st to 10th	Night	16% 4 26% 37% 16% 1	760
	11th to 20th	Night	13% 6% 32% 33% 15% 2	760
	21st to end	Night	13% 7% 32% 33% 14% 1	836
November	1st to 10th	Night	21% 7% 28% 32% 11% 2	949
	11th to 20th	Night	13% 8% 35% 30% 12% 2	1000
	21st to end	Night	12% 5% 36% 35% 11% 2	1000
December	1st to 10th	Night	15% 7% 31% 32% 14% 2	1000
	11th to 20th	Night	13% 6% 32% 33% 14% 1	1000
	21st to end	Night	11% 5% 28% 36% 17% 3	1100

Page generated at 2025-04-23 07:25:01. Version ac07

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