Observe the Heavens Astronomy Camp
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observe the Heavens Astronomy Camp clear sky chart from 2005-11-06 to 2024-11-25.

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	8% 8% 3 7% 5% 5% 5% 4 6% 7% 43%	105331
	Night	10% 10% 3 7% 5% 4 5% 4 6% 7% 40%	102724
Transparency	Day	39% 6% 11% 22% 16% 7%	105099
	Night	43% 6% 11% 21% 14% 5%	102602
Seeing	Day	14% 9% 23% 29% 19% 6%	14785
	Night	16% 4 13% 39% 25% 4	23895

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	14% 21% 8% 12% 7% 6% 5% 3 5% 5% 14%	2539
	11th to 20th	Day	19% 12% 4 9% 6% 7% 7% 4 4 6% 22%	2516
	21st to end	Day	25% 23% 6% 14% 6% 4 3 2 3 4 10%	2794
February	1st to 10th	Day	12% 15% 4 10% 7% 7% 5% 4 5% 8% 23%	1542
	11th to 20th	Day	11% 14% 3 8% 6% 4 5% 5% 7% 8% 29%	1731
	21st to end	Day	12% 13% 4 9% 5% 6% 5% 5% 6% 7% 28%	1570
March	1st to 10th	Day	9% 12% 3 7% 5% 6% 6% 5% 7% 9% 30%	3138
	11th to 20th	Day	7% 9% 2 5% 3 4 4 3 5% 8% 49%	3256
	21st to end	Day	11% 12% 4 10% 7% 6% 6% 5% 7% 7% 26%	4165
April	1st to 10th	Day	10% 11% 3 9% 6% 6% 6% 6% 8% 8% 26%	2280
	11th to 20th	Day	8% 8% 2 9% 7% 6% 5% 5% 7% 7% 35%	2294
	21st to end	Day	8% 7% 3 9% 6% 6% 6% 4 7% 9% 34%	2482
May	1st to 10th	Day	6% 8% 3 7% 5% 4 5% 4 7% 10% 42%	4420
	11th to 20th	Day	5% 6% 3 7% 5% 5% 5% 5% 7% 10% 41%	4377
	21st to end	Day	7% 8% 4 10% 6% 7% 7% 6% 8% 9% 29%	4813
June	1st to 10th	Day	13% 7% 3 7% 6% 5% 5% 4 6% 7% 38%	2827
	11th to 20th	Day	9% 7% 3 8% 7% 6% 6% 5% 7% 7% 36%	2850
	21st to end	Day	5% 4 2 5% 4 4 4 5% 6% 8% 53%	2844
July	1st to 10th	Day	2 2 1 3 3 3 3 3 4 6% 72%	4420
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 4 77%	4420
	21st to end	Day	2 2 1 2 2 2 3 3 5% 5% 73%	4790
August	1st to 10th	Day	3 2 1 4 3 3 4 3 5% 7% 67%	4401
	11th to 20th	Day	2 2 1 3 3 4 3 3 5% 8% 65%	4223
	21st to end	Day	2 3 2 4 4 4 5% 3 5% 6% 61%	4214
September	1st to 10th	Day	3 3 1 3 3 3 4 3 5% 6% 66%	2280
	11th to 20th	Day	5% 5% 2 5% 5% 5% 6% 5% 6% 7% 50%	2206
	21st to end	Day	7% 4 2 6% 4 5% 5% 3 7% 7% 52%	2090
October	1st to 10th	Day	5% 4 2 6% 3 4 3 4 5% 7% 56%	3281
	11th to 20th	Day	6% 5% 2 7% 5% 5% 6% 5% 8% 9% 43%	3010
	21st to end	Day	11% 8% 3 6% 5% 5% 6% 5% 6% 6% 39%	3101
November	1st to 10th	Day	16% 13% 4 9% 6% 5% 5% 4 6% 7% 27%	1764
	11th to 20th	Day	15% 14% 4 10% 7% 5% 5% 3 3 5% 27%	1633
	21st to end	Day	14% 20% 5% 10% 7% 5% 5% 4 5% 5% 20%	1450
December	1st to 10th	Day	12% 16% 6% 11% 7% 6% 6% 4 6% 5% 21%	1330
	11th to 20th	Day	20% 24% 6% 12% 5% 6% 5% 3 5% 4 10%	1682
	21st to end	Day	13% 21% 7% 13% 10% 6% 5% 3 5% 5% 13%	2598
January	1st to 10th	Night	18% 20% 7% 13% 7% 5% 4 3 4 4 15%	4406
	11th to 20th	Night	17% 14% 4 11% 6% 5% 5% 4 6% 10% 18%	4382
	21st to end	Night	24% 25% 7% 11% 6% 4 3 2 3 3 11%	4862
February	1st to 10th	Night	11% 17% 4 9% 6% 4 5% 4 6% 7% 25%	2637
	11th to 20th	Night	9% 13% 4 10% 5% 6% 4 5% 7% 6% 31%	2335
	21st to end	Night	8% 10% 4 8% 6% 5% 5% 5% 8% 8% 34%	1884
March	1st to 10th	Night	6% 9% 3 7% 6% 5% 6% 5% 7% 10% 36%	3736
	11th to 20th	Night	8% 8% 3 6% 4 4 4 3 5% 6% 52%	3707
	21st to end	Night	10% 10% 3 9% 7% 6% 7% 5% 8% 9% 26%	3488
April	1st to 10th	Night	8% 8% 3 9% 6% 5% 6% 4 7% 8% 36%	1900
	11th to 20th	Night	7% 8% 3 9% 8% 5% 5% 3 5% 7% 40%	1837
	21st to end	Night	5% 7% 4 7% 6% 5% 6% 4 7% 8% 41%	1696
May	1st to 10th	Night	7% 7% 2 8% 6% 5% 6% 4 7% 8% 41%	2540
	11th to 20th	Night	5% 4 2 5% 4 4 5% 5% 7% 9% 51%	2516
	21st to end	Night	8% 7% 3 7% 5% 5% 5% 4 7% 11% 38%	2762
June	1st to 10th	Night	8% 7% 2 6% 5% 5% 5% 5% 7% 9% 43%	1349
	11th to 20th	Night	6% 6% 2 6% 5% 6% 6% 5% 7% 10% 42%	1330
	21st to end	Night	3 4 1 5% 4 4 5% 3 5% 8% 58%	1331
July	1st to 10th	Night	1 1 1 3 2 3 3 3 4 6% 73%	2540
	11th to 20th	Night	1 1 1 2 2 2 2 2 3 4 81%	2540
	21st to end	Night	1 1 1 2 2 2 2 2 4 5% 80%	2762
August	1st to 10th	Night	3 3 1 3 2 2 2 2 4 7% 71%	2529
	11th to 20th	Night	1 3 1 4 3 3 3 4 6% 8% 64%	2607
	21st to end	Night	2 3 1 4 4 3 5% 4 5% 7% 63%	3461
September	1st to 10th	Night	2 1 1 3 2 3 4 3 5% 9% 66%	1900
	11th to 20th	Night	6% 4 2 5% 3 4 5% 4 7% 7% 53%	1973
	21st to end	Night	7% 4 2 5% 4 4 3 3 7% 8% 54%	2090
October	1st to 10th	Night	5% 3 1 4 3 3 4 3 6% 8% 60%	3697
	11th to 20th	Night	7% 5% 2 6% 4 4 5% 4 7% 8% 48%	3922
	21st to end	Night	12% 7% 2 6% 4 5% 5% 4 6% 7% 42%	4457
November	1st to 10th	Night	17% 9% 4 8% 5% 4 5% 5% 7% 8% 28%	2535
	11th to 20th	Night	16% 13% 4 7% 6% 6% 6% 4 6% 5% 27%	2765
	21st to end	Night	16% 15% 6% 11% 6% 5% 5% 3 5% 5% 24%	2802
December	1st to 10th	Night	13% 16% 5% 11% 7% 5% 4 4 6% 6% 23%	2850
	11th to 20th	Night	19% 22% 8% 13% 7% 4 4 3 4 4 12%	3510
	21st to end	Night	17% 22% 6% 12% 7% 6% 5% 4 5% 4 12%	5086

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% 8% 8% 8% 4	2539
	11th to 20th	Day	62% 7% 12% 13% 2 4	2540
	21st to end	Day	77% 8% 6% 7% 3	2794
February	1st to 10th	Day	58% 8% 15% 12% 6% 1	1542
	11th to 20th	Day	51% 8% 15% 17% 8%	1740
	21st to end	Day	53% 8% 12% 16% 9% 1	1570
March	1st to 10th	Day	47% 8% 14% 19% 12% 1	3138
	11th to 20th	Day	34% 6% 21% 31% 8%	3256
	21st to end	Day	51% 12% 16% 14% 7%	4165
April	1st to 10th	Day	51% 7% 14% 19% 7% 1	2280
	11th to 20th	Day	44% 7% 14% 21% 12% 3	2294
	21st to end	Day	44% 7% 12% 23% 10% 3	2482
May	1st to 10th	Day	35% 5% 9% 32% 18% 2	4420
	11th to 20th	Day	30% 9% 12% 29% 17% 2	4380
	21st to end	Day	44% 12% 14% 22% 8% 1	4814
June	1st to 10th	Day	44% 5% 10% 21% 16% 5%	2827
	11th to 20th	Day	44% 6% 9% 22% 14% 4	2850
	21st to end	Day	28% 5% 11% 28% 23% 6%	2844
July	1st to 10th	Day	14% 3 5% 18% 28% 32%	4351
	11th to 20th	Day	12% 2 4 13% 25% 44%	4345
	21st to end	Day	13% 2 3 22% 33% 25%	4639
August	1st to 10th	Day	17% 3 4 25% 36% 14%	4384
	11th to 20th	Day	18% 2 8% 42% 25% 4	4265
	21st to end	Day	24% 3 11% 32% 25% 5%	4213
September	1st to 10th	Day	19% 4 9% 32% 27% 9%	2280
	11th to 20th	Day	31% 5% 13% 25% 22% 5%	2206
	21st to end	Day	31% 5% 17% 30% 12% 4	2090
October	1st to 10th	Day	28% 4 15% 36% 16% 1	3281
	11th to 20th	Day	37% 5% 18% 24% 16%	3010
	21st to end	Day	44% 5% 17% 21% 12% 1	3101
November	1st to 10th	Day	57% 8% 13% 16% 6% 1	1764
	11th to 20th	Day	59% 7% 13% 14% 5% 2	1633
	21st to end	Day	65% 8% 11% 12% 4	1450
December	1st to 10th	Day	64% 7% 11% 12% 5%	1330
	11th to 20th	Day	75% 8% 8% 6% 3	1684
	21st to end	Day	69% 13% 8% 7% 4	2598
January	1st to 10th	Night	71% 7% 8% 10% 3	4406
	11th to 20th	Night	61% 6% 12% 16% 4 2	4420
	21st to end	Night	76% 8% 7% 6% 2	4862
February	1st to 10th	Night	57% 8% 14% 13% 6% 2	2637
	11th to 20th	Night	51% 8% 14% 18% 9%	2337
	21st to end	Night	45% 8% 15% 19% 12% 1	1884
March	1st to 10th	Night	39% 7% 16% 26% 11% 1	3736
	11th to 20th	Night	34% 4 20% 31% 11%	3708
	21st to end	Night	49% 11% 14% 19% 6%	3488
April	1st to 10th	Night	43% 6% 15% 25% 10% 1	1900
	11th to 20th	Night	44% 5% 10% 23% 16% 2	1837
	21st to end	Night	38% 5% 12% 25% 17% 3	1696
May	1st to 10th	Night	37% 7% 8% 27% 19% 2	2540
	11th to 20th	Night	24% 8% 10% 34% 20% 3	2516
	21st to end	Night	36% 12% 13% 26% 12%	2762
June	1st to 10th	Night	36% 7% 9% 25% 18% 6%	1349
	11th to 20th	Night	35% 6% 12% 23% 18% 6%	1330
	21st to end	Night	24% 5% 9% 27% 27% 8%	1331
July	1st to 10th	Night	12% 4 4 16% 32% 32%	2500
	11th to 20th	Night	9% 2 4 13% 20% 51%	2492
	21st to end	Night	9% 2 3 19% 35% 33%	2674
August	1st to 10th	Night	16% 2 4 25% 31% 21%	2521
	11th to 20th	Night	18% 2 6% 38% 31% 5%	2631
	21st to end	Night	22% 2 10% 31% 27% 8%	3461
September	1st to 10th	Night	16% 3 7% 30% 30% 13%	1900
	11th to 20th	Night	28% 6% 11% 25% 23% 7%	1973
	21st to end	Night	28% 3 15% 33% 15% 6%	2090
October	1st to 10th	Night	24% 3 12% 41% 18% 1	3697
	11th to 20th	Night	34% 4 16% 27% 18% 1	3922
	21st to end	Night	41% 5% 16% 27% 11% 2	4457
November	1st to 10th	Night	53% 8% 17% 15% 6% 1	2535
	11th to 20th	Night	56% 9% 14% 13% 6% 2	2765
	21st to end	Night	61% 7% 13% 12% 6%	2802
December	1st to 10th	Night	61% 8% 11% 17% 3	2850
	11th to 20th	Night	74% 8% 8% 7% 3	3507
	21st to end	Night	70% 10% 7% 8% 5%	5086

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	30% 6% 17% 29% 14% 4	180
	11th to 20th	Day	30% 2 19% 26% 19% 4	180
	21st to end	Day	29% 6% 16% 31% 15% 4	198
February	1st to 10th	Day	19% 7% 25% 36% 12% 1	202
	11th to 20th	Day	20% 9% 22% 31% 15% 3	396
	21st to end	Day	18% 9% 25% 29% 15% 3	382
March	1st to 10th	Day	17% 15% 26% 25% 12% 5%	460
	11th to 20th	Day	19% 10% 18% 27% 20% 6%	460
	21st to end	Day	19% 12% 24% 29% 11% 5%	506
April	1st to 10th	Day	19% 12% 27% 25% 12% 4	460
	11th to 20th	Day	14% 19% 28% 21% 13% 5%	452
	21st to end	Day	13% 15% 25% 26% 16% 5%	460
May	1st to 10th	Day	11% 11% 28% 27% 17% 5%	463
	11th to 20th	Day	15% 8% 24% 26% 20% 7%	488
	21st to end	Day	13% 9% 22% 26% 20% 9%	529
June	1st to 10th	Day	16% 10% 19% 28% 22% 6%	657
	11th to 20th	Day	13% 11% 25% 29% 19% 4	680
	21st to end	Day	6% 7% 19% 33% 27% 9%	674
July	1st to 10th	Day	5% 6% 26% 37% 21% 5%	486
	11th to 20th	Day	5% 9% 24% 35% 20% 8%	484
	21st to end	Day	3 7% 24% 34% 22% 11%	531
August	1st to 10th	Day	7% 5% 17% 35% 25% 11%	487
	11th to 20th	Day	4 4 19% 30% 28% 14%	477
	21st to end	Day	7% 7% 26% 25% 23% 12%	539
September	1st to 10th	Day	7% 5% 25% 27% 25% 11%	490
	11th to 20th	Day	8% 9% 20% 32% 23% 8%	490
	21st to end	Day	10% 11% 26% 27% 18% 8%	490
October	1st to 10th	Day	11% 10% 22% 30% 21% 6%	490
	11th to 20th	Day	15% 7% 19% 34% 19% 7%	403
	21st to end	Day	20% 8% 23% 31% 14% 3	330
November	1st to 10th	Day	23% 6% 22% 30% 19% 1	300
	11th to 20th	Day	25% 10% 17% 26% 18% 4	215
	21st to end	Day	24% 7% 15% 32% 18% 4	188
December	1st to 10th	Day	24% 5% 21% 22% 21% 7%	180
	11th to 20th	Day	24% 7% 24% 29% 12% 3	180
	21st to end	Day	26% 7% 15% 37% 12% 3	198
January	1st to 10th	Night	31% 5% 18% 28% 16% 2	760
	11th to 20th	Night	28% 4 13% 36% 16% 3	760
	21st to end	Night	25% 4 11% 40% 19% 3	836
February	1st to 10th	Night	22% 4 17% 41% 14% 2	760
	11th to 20th	Night	17% 5% 19% 37% 20% 2	744
	21st to end	Night	15% 4 17% 40% 19% 4	628
March	1st to 10th	Night	16% 4 15% 39% 23% 3	760
	11th to 20th	Night	18% 4 18% 33% 25% 2	760
	21st to end	Night	14% 4 19% 41% 18% 4	836
April	1st to 10th	Night	13% 5% 13% 40% 25% 4	760
	11th to 20th	Night	11% 5% 18% 43% 21% 3	709
	21st to end	Night	9% 5% 19% 42% 23% 3	556
May	1st to 10th	Night	8% 6% 14% 41% 27% 5%	380
	11th to 20th	Night	10% 3 9% 36% 37% 6%	374
	21st to end	Night	12% 4 9% 36% 33% 7%	411
June	1st to 10th	Night	11% 2 11% 44% 29% 3	380
	11th to 20th	Night	8% 3 14% 45% 27% 3	380
	21st to end	Night	5% 2 9% 42% 38% 3	380
July	1st to 10th	Night	2 2 8% 37% 45% 5%	370
	11th to 20th	Night	2 1 9% 50% 36% 2	368
	21st to end	Night	1 3 7% 39% 44% 6%	416
August	1st to 10th	Night	4 1 5% 33% 48% 10%	378
	11th to 20th	Night	2 2 7% 33% 45% 10%	434
	21st to end	Night	4 3 9% 39% 40% 5%	812
September	1st to 10th	Night	3 1 11% 41% 36% 7%	760
	11th to 20th	Night	7% 3 9% 34% 38% 9%	760
	21st to end	Night	10% 4 11% 40% 31% 5%	760
October	1st to 10th	Night	13% 2 11% 40% 31% 4	760
	11th to 20th	Night	13% 5% 13% 38% 27% 4	760
	21st to end	Night	19% 3 15% 42% 19% 3	836
November	1st to 10th	Night	23% 4 12% 45% 16% 1	780
	11th to 20th	Night	24% 5% 18% 33% 17% 3	800
	21st to end	Night	25% 4 14% 34% 20% 3	858
December	1st to 10th	Night	22% 5% 14% 39% 17% 3	950
	11th to 20th	Night	28% 6% 13% 37% 15% 2	950
	21st to end	Night	29% 5% 13% 40% 12% 1	969

Page generated at 2024-11-22 05:02:30. Version ac07

Copyright © 2024 Attilla Danko.