Worthy Garden Club Hopservatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Worthy Garden Club Hopservatory clear sky chart from 2005-11-06 to 2024-12-06.

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	4 6% 2 6% 4 4 4 4 6% 7% 53%	105658
	Night	4 7% 2 6% 4 4 4 4 6% 7% 50%	102744
Transparency	Day	30% 8% 12% 21% 19% 11%	105401
	Night	32% 9% 14% 22% 16% 7%	102590
Seeing	Day	9% 16% 27% 27% 17% 5%	14746
	Night	7% 12% 24% 36% 19% 2	23836

By Month

Percentage Cloud Cover SW (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	7% 12% 4 9% 7% 6% 7% 5% 8% 9% 28%	2539
	11th to 20th	Day	9% 11% 4 9% 6% 7% 7% 5% 8% 7% 26%	2540
	21st to end	Day	8% 11% 4 8% 6% 6% 6% 4 7% 9% 32%	3015
February	1st to 10th	Day	4 10% 3 8% 6% 7% 5% 5% 7% 9% 36%	1710
	11th to 20th	Day	5% 10% 4 7% 5% 5% 5% 4 7% 9% 40%	1674
	21st to end	Day	2 11% 5% 9% 5% 6% 6% 6% 7% 8% 32%	1570
March	1st to 10th	Day	3 7% 3 7% 5% 6% 6% 6% 9% 11% 37%	3169
	11th to 20th	Day	2 7% 2 6% 4 4 4 3 6% 7% 54%	3490
	21st to end	Day	3 9% 3 9% 8% 7% 8% 5% 7% 9% 31%	3999
April	1st to 10th	Day	6% 12% 4 10% 6% 5% 5% 4 6% 8% 34%	2280
	11th to 20th	Day	6% 10% 3 8% 6% 5% 5% 4 5% 8% 39%	2249
	21st to end	Day	6% 8% 2 7% 5% 4 4 3 6% 8% 46%	2332
May	1st to 10th	Day	8% 8% 3 7% 4 4 4 3 5% 7% 47%	4414
	11th to 20th	Day	5% 4 2 4 3 3 3 3 4 5% 63%	4377
	21st to end	Day	8% 6% 2 5% 4 4 5% 4 6% 7% 49%	4813
June	1st to 10th	Day	9% 7% 2 6% 5% 5% 5% 4 6% 7% 44%	2660
	11th to 20th	Day	7% 5% 2 5% 4 3 4 4 5% 7% 55%	2660
	21st to end	Day	3 3 2 3 3 3 3 3 5% 5% 66%	2660
July	1st to 10th	Day	1 1 1 2 1 2 2 3 3 85%	4420
	11th to 20th	Day	2 1 1 2 2 1 2 2 3 4 80%	4420
	21st to end	Day	1 1 2 2 2 2 2 3 4 82%	4790
August	1st to 10th	Day	3 3 1 2 2 2 4 3 5% 6% 68%	4192
	11th to 20th	Day	2 2 1 3 3 3 3 3 4 6% 71%	3995
	21st to end	Day	3 3 1 3 2 2 3 2 3 4 74%	4180
September	1st to 10th	Day	2 2 1 2 2 2 3 2 4 6% 75%	2280
	11th to 20th	Day	3 4 2 5% 4 4 4 4 5% 7% 60%	2280
	21st to end	Day	6% 5% 2 5% 3 3 3 2 5% 6% 61%	2034
October	1st to 10th	Day	4 4 1 4 3 3 3 3 3 5% 67%	3180
	11th to 20th	Day	3 4 2 5% 4 4 5% 5% 6% 9% 52%	3161
	21st to end	Day	7% 8% 2 7% 5% 5% 5% 4 6% 7% 44%	3300
November	1st to 10th	Day	5% 9% 2 8% 5% 6% 6% 4 7% 7% 40%	1764
	11th to 20th	Day	4 7% 2 8% 7% 6% 6% 6% 9% 9% 35%	1629
	21st to end	Day	4 8% 4 6% 5% 4 5% 7% 8% 9% 39%	1600
December	1st to 10th	Day	4 8% 4 6% 5% 4 3 5% 8% 8% 45%	1560
	11th to 20th	Day	4 10% 4 9% 6% 6% 5% 6% 8% 9% 33%	1928
	21st to end	Day	4 11% 4 11% 7% 6% 5% 5% 7% 9% 31%	2794
January	1st to 10th	Night	4 10% 3 9% 7% 8% 8% 6% 8% 9% 27%	4406
	11th to 20th	Night	6% 10% 4 11% 7% 6% 6% 6% 7% 9% 28%	4420
	21st to end	Night	8% 14% 5% 10% 5% 5% 5% 4 6% 7% 30%	4645
February	1st to 10th	Night	4 11% 4 9% 6% 4 5% 5% 7% 8% 38%	2470
	11th to 20th	Night	4 10% 3 9% 5% 4 5% 5% 7% 9% 40%	2393
	21st to end	Night	4 10% 4 9% 6% 6% 6% 4 6% 9% 37%	1884
March	1st to 10th	Night	3 8% 2 5% 5% 6% 7% 7% 9% 11% 37%	3692
	11th to 20th	Night	2 5% 2 5% 4 4 4 4 6% 7% 58%	3490
	21st to end	Night	5% 11% 4 9% 6% 5% 6% 6% 8% 10% 30%	3653
April	1st to 10th	Night	7% 11% 3 7% 5% 5% 5% 4 6% 7% 39%	1900
	11th to 20th	Night	6% 10% 3 6% 5% 5% 5% 5% 8% 7% 41%	1879
	21st to end	Night	6% 8% 3 5% 4 4 5% 4 8% 9% 43%	1846
May	1st to 10th	Night	9% 9% 2 6% 4 4 3 3 5% 7% 48%	2545
	11th to 20th	Night	4 4 1 4 3 3 4 3 4 5% 64%	2516
	21st to end	Night	7% 6% 2 4 4 3 4 4 5% 6% 54%	2762
June	1st to 10th	Night	10% 6% 3 5% 5% 3 4 4 4 7% 48%	1520
	11th to 20th	Night	6% 5% 2 4 3 2 3 3 5% 7% 60%	1520
	21st to end	Night	3 3 1 2 3 2 3 3 3 6% 70%	1520
July	1st to 10th	Night	1 1 1 1 1 2 2 2 3 86%	2540
	11th to 20th	Night	2 1 2 2 1 2 2 2 3 82%	2540
	21st to end	Night	1 1 2 1 2 2 2 3 3 84%	2761
August	1st to 10th	Night	2 2 1 4 3 3 2 2 4 5% 72%	2742
	11th to 20th	Night	1 2 1 2 2 2 2 3 4 5% 75%	2842
	21st to end	Night	2 2 1 3 2 2 2 2 3 4 78%	3498
September	1st to 10th	Night	2 1 1 2 1 2 2 2 3 4 80%	1900
	11th to 20th	Night	3 3 1 5% 3 3 4 2 6% 6% 64%	1900
	21st to end	Night	6% 4 1 4 3 2 2 3 5% 6% 64%	2141
October	1st to 10th	Night	4 4 1 4 2 2 3 2 3 4 71%	3800
	11th to 20th	Night	4 4 2 5% 4 4 4 4 5% 8% 55%	3777
	21st to end	Night	4 6% 2 8% 6% 5% 5% 5% 6% 8% 45%	4263
November	1st to 10th	Night	6% 9% 3 7% 6% 4 5% 5% 7% 7% 40%	2535
	11th to 20th	Night	6% 7% 3 8% 6% 5% 5% 5% 8% 9% 38%	2770
	21st to end	Night	4 8% 3 6% 4 4 5% 5% 7% 8% 45%	2800
December	1st to 10th	Night	5% 9% 3 7% 5% 4 5% 4 7% 8% 44%	2736
	11th to 20th	Night	4 9% 4 10% 7% 6% 6% 5% 8% 9% 32%	3276
	21st to end	Night	4 10% 3 8% 6% 6% 6% 5% 6% 7% 37%	4862

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	45% 16% 20% 15% 5%	2539
	11th to 20th	Day	53% 13% 13% 13% 4 3	2540
	21st to end	Day	45% 13% 18% 17% 6% 2	3015
February	1st to 10th	Day	43% 12% 16% 19% 8% 1	1710
	11th to 20th	Day	40% 12% 17% 19% 10% 2	1683
	21st to end	Day	45% 14% 16% 15% 9% 1	1570
March	1st to 10th	Day	36% 10% 17% 22% 13% 1	3169
	11th to 20th	Day	28% 10% 15% 31% 16%	3490
	21st to end	Day	43% 14% 18% 18% 6%	3999
April	1st to 10th	Day	47% 10% 15% 17% 9% 2	2280
	11th to 20th	Day	44% 8% 15% 18% 12% 3	2252
	21st to end	Day	36% 9% 17% 23% 13% 2	2332
May	1st to 10th	Day	34% 8% 13% 26% 19% 1	4414
	11th to 20th	Day	23% 5% 9% 27% 33% 4	4380
	21st to end	Day	32% 9% 19% 28% 12%	4814
June	1st to 10th	Day	39% 7% 13% 28% 12% 1	2660
	11th to 20th	Day	28% 7% 12% 31% 19% 3	2660
	21st to end	Day	19% 5% 10% 29% 26% 10%	2660
July	1st to 10th	Day	8% 3 5% 12% 19% 53%	4351
	11th to 20th	Day	10% 2 4 7% 22% 54%	4345
	21st to end	Day	9% 1 4 16% 39% 31%	4639
August	1st to 10th	Day	17% 4 5% 15% 35% 24%	4176
	11th to 20th	Day	15% 3 5% 27% 34% 15%	4034
	21st to end	Day	17% 2 6% 26% 27% 21%	4179
September	1st to 10th	Day	12% 3 6% 24% 34% 21%	2280
	11th to 20th	Day	24% 6% 10% 24% 24% 12%	2280
	21st to end	Day	24% 6% 11% 25% 22% 11%	2034
October	1st to 10th	Day	23% 4 10% 20% 26% 17%	3180
	11th to 20th	Day	29% 5% 16% 26% 21% 3	3161
	21st to end	Day	39% 7% 8% 25% 19% 2	3300
November	1st to 10th	Day	40% 9% 15% 21% 13% 1	1764
	11th to 20th	Day	41% 14% 20% 15% 9% 1	1629
	21st to end	Day	39% 12% 15% 17% 15% 1	1600
December	1st to 10th	Day	35% 12% 18% 21% 12% 1	1560
	11th to 20th	Day	44% 13% 19% 16% 8% 1	1928
	21st to end	Day	47% 12% 17% 19% 4 1	2794
January	1st to 10th	Night	47% 17% 20% 11% 5%	4406
	11th to 20th	Night	49% 12% 18% 13% 5% 3	4420
	21st to end	Night	52% 10% 15% 14% 7% 2	4645
February	1st to 10th	Night	42% 14% 19% 15% 9% 1	2470
	11th to 20th	Night	39% 12% 19% 19% 8% 2	2395
	21st to end	Night	43% 15% 17% 17% 8% 1	1884
March	1st to 10th	Night	34% 13% 16% 26% 11% 1	3692
	11th to 20th	Night	25% 10% 18% 32% 15%	3490
	21st to end	Night	43% 16% 20% 16% 5%	3653
April	1st to 10th	Night	43% 11% 20% 17% 8% 1	1900
	11th to 20th	Night	40% 10% 17% 20% 11% 2	1879
	21st to end	Night	37% 12% 16% 23% 10% 1	1846
May	1st to 10th	Night	33% 12% 16% 27% 12%	2545
	11th to 20th	Night	20% 8% 13% 35% 21% 2	2516
	21st to end	Night	28% 12% 29% 26% 5%	2762
June	1st to 10th	Night	37% 9% 13% 30% 11% 1	1520
	11th to 20th	Night	25% 7% 15% 35% 15% 3	1520
	21st to end	Night	17% 5% 13% 32% 26% 7%	1520
July	1st to 10th	Night	6% 2 6% 15% 24% 47%	2500
	11th to 20th	Night	11% 2 4 14% 22% 47%	2492
	21st to end	Night	8% 2 4 18% 41% 28%	2674
August	1st to 10th	Night	16% 3 5% 18% 40% 18%	2734
	11th to 20th	Night	13% 3 6% 37% 32% 9%	2869
	21st to end	Night	13% 2 8% 30% 30% 16%	3498
September	1st to 10th	Night	10% 3 7% 27% 36% 18%	1900
	11th to 20th	Night	21% 7% 11% 24% 26% 11%	1900
	21st to end	Night	23% 6% 10% 24% 25% 12%	2141
October	1st to 10th	Night	20% 4 8% 23% 32% 13%	3800
	11th to 20th	Night	28% 5% 21% 25% 18% 4	3777
	21st to end	Night	36% 7% 11% 29% 15% 2	4263
November	1st to 10th	Night	42% 10% 15% 16% 13% 3	2535
	11th to 20th	Night	41% 13% 17% 19% 9% 1	2770
	21st to end	Night	35% 12% 16% 18% 17% 2	2800
December	1st to 10th	Night	37% 13% 17% 20% 11% 2	2736
	11th to 20th	Night	44% 15% 16% 16% 9%	3276
	21st to end	Night	43% 14% 16% 20% 7% 1	4862

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	16% 24% 32% 19% 8% 2	180
	11th to 20th	Day	19% 13% 30% 24% 11% 2	180
	21st to end	Day	10% 23% 26% 27% 12% 2	328
February	1st to 10th	Day	14% 23% 27% 27% 8% 1	370
	11th to 20th	Day	12% 28% 31% 19% 8% 1	369
	21st to end	Day	12% 26% 29% 24% 9% 1	382
March	1st to 10th	Day	11% 25% 32% 27% 5%	460
	11th to 20th	Day	10% 24% 27% 27% 12% 1	460
	21st to end	Day	12% 28% 29% 24% 7%	506
April	1st to 10th	Day	13% 23% 30% 21% 11% 3	460
	11th to 20th	Day	14% 24% 29% 21% 7% 4	452
	21st to end	Day	9% 24% 30% 22% 12% 3	460
May	1st to 10th	Day	10% 20% 27% 26% 13% 3	463
	11th to 20th	Day	16% 15% 28% 19% 16% 5%	488
	21st to end	Day	12% 13% 25% 27% 18% 5%	529
June	1st to 10th	Day	9% 15% 27% 25% 19% 6%	490
	11th to 20th	Day	8% 18% 31% 25% 16% 3	490
	21st to end	Day	4 8% 27% 32% 23% 8%	490
July	1st to 10th	Day	2 6% 27% 37% 21% 6%	486
	11th to 20th	Day	1 5% 33% 30% 23% 8%	484
	21st to end	Day	1 5% 28% 35% 21% 9%	531
August	1st to 10th	Day	2 5% 25% 35% 23% 11%	487
	11th to 20th	Day	2 5% 22% 32% 26% 13%	477
	21st to end	Day	4 9% 22% 32% 24% 10%	539
September	1st to 10th	Day	3 5% 22% 34% 28% 8%	490
	11th to 20th	Day	4 10% 22% 33% 24% 6%	490
	21st to end	Day	7% 13% 21% 33% 22% 3	490
October	1st to 10th	Day	9% 15% 23% 28% 22% 4	490
	11th to 20th	Day	9% 17% 22% 25% 23% 4	490
	21st to end	Day	11% 18% 30% 21% 16% 5%	453
November	1st to 10th	Day	11% 17% 29% 29% 13% 2	300
	11th to 20th	Day	9% 27% 25% 22% 14% 3	214
	21st to end	Day	13% 23% 21% 29% 13% 2	200
December	1st to 10th	Day	10% 18% 23% 25% 15% 8%	190
	11th to 20th	Day	12% 25% 34% 23% 6% 1	180
	21st to end	Day	14% 20% 30% 25% 9% 2	198
January	1st to 10th	Night	9% 20% 31% 26% 12% 2	760
	11th to 20th	Night	8% 20% 29% 25% 17% 2	760
	21st to end	Night	11% 15% 25% 33% 14% 2	836
February	1st to 10th	Night	7% 18% 31% 32% 11% 1	760
	11th to 20th	Night	8% 14% 32% 33% 12% 1	744
	21st to end	Night	8% 18% 31% 34% 8%	628
March	1st to 10th	Night	9% 20% 27% 32% 10% 2	760
	11th to 20th	Night	6% 16% 28% 35% 15% 1	760
	21st to end	Night	7% 18% 32% 30% 12% 1	836
April	1st to 10th	Night	11% 14% 28% 31% 14% 1	760
	11th to 20th	Night	9% 13% 31% 29% 15% 3	751
	21st to end	Night	9% 11% 28% 35% 15% 1	706
May	1st to 10th	Night	9% 8% 24% 38% 19% 1	385
	11th to 20th	Night	8% 7% 19% 43% 22% 1	374
	21st to end	Night	10% 7% 21% 36% 24% 2	411
June	1st to 10th	Night	9% 7% 21% 42% 19% 1	380
	11th to 20th	Night	7% 6% 22% 44% 21% 1	380
	21st to end	Night	4 1 14% 59% 22%	380
July	1st to 10th	Night	2 1 9% 60% 27% 1	370
	11th to 20th	Night	2 12% 64% 21% 1	368
	21st to end	Night	1 10% 58% 30% 1	416
August	1st to 10th	Night	2 1 6% 52% 36% 3	500
	11th to 20th	Night	1 1 8% 43% 41% 6%	581
	21st to end	Night	2 2 17% 46% 30% 2	836
September	1st to 10th	Night	2 2 15% 47% 31% 3	760
	11th to 20th	Night	4 3 14% 42% 31% 5%	760
	21st to end	Night	8% 5% 18% 38% 26% 5%	760
October	1st to 10th	Night	8% 5% 22% 38% 24% 3	760
	11th to 20th	Night	7% 10% 21% 35% 24% 4	760
	21st to end	Night	8% 13% 25% 33% 15% 6%	836
November	1st to 10th	Night	9% 14% 30% 33% 13% 2	780
	11th to 20th	Night	10% 21% 27% 26% 14% 2	800
	21st to end	Night	7% 17% 25% 33% 15% 3	800
December	1st to 10th	Night	9% 13% 25% 32% 18% 2	782
	11th to 20th	Night	8% 19% 30% 30% 13% 1	760
	21st to end	Night	8% 24% 32% 25% 10%	836

Page generated at 2024-12-03 03:45:09. Version ac07

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