Hemlock Crossings Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hemlock Crossings Park clear sky chart from 2005-11-06 to 2025-06-10.

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	13% 11% 4 9% 5% 4 4 3 5% 7% 35%	119271
	Night	15% 13% 5% 11% 5% 4 4 3 4 5% 30%	119133
Transparency	Day	48% 6% 12% 21% 12% 1	122842
	Night	55% 6% 10% 18% 11% 1	123703
Seeing	Day	17% 9% 25% 28% 16% 5%	16598
	Night	20% 9% 26% 29% 14% 2	26538

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	12% 22% 12% 23% 7% 4 3 2 2 3 10%	3617
	11th to 20th	Day	10% 16% 7% 24% 16% 10% 4 2 3 2 5%	3620
	21st to end	Day	15% 18% 8% 22% 7% 4 6% 2 2 3 12%	3982
February	1st to 10th	Day	12% 17% 6% 17% 11% 6% 5% 3 4 4 17%	1831
	11th to 20th	Day	13% 14% 6% 15% 10% 5% 4 3 4 5% 20%	1948
	21st to end	Day	15% 15% 5% 11% 7% 6% 4 4 5% 6% 22%	1650
March	1st to 10th	Day	13% 10% 4 12% 5% 5% 4 4 5% 6% 32%	4480
	11th to 20th	Day	11% 8% 5% 8% 5% 4 4 4 5% 8% 37%	4790
	21st to end	Day	19% 14% 7% 8% 5% 3 3 3 4 5% 27%	5751
April	1st to 10th	Day	19% 12% 3 7% 5% 4 4 4 5% 6% 32%	2400
	11th to 20th	Day	16% 10% 3 7% 4 4 4 4 5% 7% 38%	2408
	21st to end	Day	16% 9% 3 7% 5% 4 4 4 5% 8% 36%	2600
May	1st to 10th	Day	17% 7% 2 6% 4 4 4 3 5% 8% 40%	5862
	11th to 20th	Day	13% 7% 2 6% 4 4 4 3 6% 9% 43%	5949
	21st to end	Day	14% 6% 2 5% 3 3 3 3 6% 8% 47%	6935
June	1st to 10th	Day	10% 5% 2 5% 4 5% 4 3 6% 9% 48%	2787
	11th to 20th	Day	10% 5% 2 5% 4 4 4 3 5% 9% 51%	2660
	21st to end	Day	10% 6% 2 6% 3 4 4 4 6% 8% 46%	2660
July	1st to 10th	Day	12% 7% 3 7% 4 4 5% 4 6% 8% 41%	4440
	11th to 20th	Day	6% 4 2 4 3 4 5% 4 6% 9% 54%	4440
	21st to end	Day	7% 5% 2 5% 4 4 5% 4 6% 9% 49%	4813
August	1st to 10th	Day	11% 5% 2 5% 3 4 4 4 6% 10% 45%	4199
	11th to 20th	Day	11% 5% 2 5% 3 3 4 4 6% 7% 51%	4029
	21st to end	Day	8% 5% 2 6% 4 4 4 3 6% 8% 49%	4180
September	1st to 10th	Day	10% 6% 2 5% 5% 4 3 3 5% 8% 47%	2271
	11th to 20th	Day	11% 5% 2 5% 3 4 4 4 6% 8% 49%	2090
	21st to end	Day	12% 7% 3 7% 5% 5% 4 3 5% 8% 42%	2090
October	1st to 10th	Day	16% 7% 2 6% 5% 4 4 2 4 6% 44%	2090
	11th to 20th	Day	22% 11% 3 7% 5% 5% 5% 4 6% 6% 25%	1841
	21st to end	Day	23% 12% 4 9% 6% 5% 4 3 5% 6% 23%	1881
November	1st to 10th	Day	15% 13% 3 8% 5% 4 4 3 5% 6% 34%	1762
	11th to 20th	Day	17% 20% 6% 12% 5% 5% 4 3 5% 4 20%	1800
	21st to end	Day	22% 20% 6% 10% 5% 3 4 3 3 5% 20%	1800
December	1st to 10th	Day	11% 27% 13% 14% 5% 3 3 2 3 5% 13%	2625
	11th to 20th	Day	17% 25% 12% 14% 8% 4 3 3 3 3 9%	3008
	21st to end	Day	23% 24% 7% 13% 6% 4 3 3 4 4 11%	3982
January	1st to 10th	Night	11% 22% 12% 24% 6% 4 3 2 3 3 11%	6348
	11th to 20th	Night	12% 20% 12% 23% 11% 8% 3 2 2 2 6%	6360
	21st to end	Night	16% 20% 9% 17% 7% 7% 5% 2 3 3 12%	6996
February	1st to 10th	Night	12% 20% 6% 16% 10% 5% 3 3 3 4 18%	2562
	11th to 20th	Night	14% 17% 7% 15% 8% 5% 4 3 3 4 21%	2338
	21st to end	Night	17% 16% 4 12% 6% 5% 4 4 4 6% 23%	1980
March	1st to 10th	Night	15% 9% 3 9% 5% 5% 4 3 5% 6% 35%	5373
	11th to 20th	Night	10% 8% 3 8% 5% 4 4 3 5% 8% 42%	5169
	21st to end	Night	18% 11% 5% 10% 5% 4 3 3 4 5% 30%	5220
April	1st to 10th	Night	16% 10% 3 7% 5% 4 5% 4 6% 6% 35%	2000
	11th to 20th	Night	20% 10% 2 6% 4 4 4 4 5% 6% 36%	1941
	21st to end	Night	17% 7% 4 6% 4 4 5% 4 6% 7% 37%	1800
May	1st to 10th	Night	16% 9% 3 8% 6% 4 5% 4 5% 6% 34%	4033
	11th to 20th	Night	15% 7% 3 7% 4 3 4 4 5% 7% 41%	3945
	21st to end	Night	17% 7% 3 6% 4 4 4 3 4 6% 42%	3942
June	1st to 10th	Night	10% 6% 2 5% 5% 4 5% 5% 6% 8% 44%	1597
	11th to 20th	Night	9% 7% 2 7% 4 4 4 4 5% 9% 44%	1520
	21st to end	Night	9% 6% 2 6% 5% 4 5% 4 7% 9% 43%	1520
July	1st to 10th	Night	9% 6% 2 7% 5% 5% 5% 4 6% 8% 41%	2530
	11th to 20th	Night	6% 4 1 4 4 4 3 4 5% 7% 56%	2530
	21st to end	Night	7% 5% 2 7% 4 4 4 4 6% 8% 49%	2750
August	1st to 10th	Night	9% 5% 3 6% 4 3 4 3 6% 9% 49%	2732
	11th to 20th	Night	11% 4 2 5% 4 3 4 4 5% 8% 50%	2785
	21st to end	Night	8% 6% 2 7% 4 4 4 4 5% 8% 46%	3474
September	1st to 10th	Night	10% 5% 2 6% 4 4 4 3 5% 6% 50%	1900
	11th to 20th	Night	11% 4 2 5% 3 3 3 3 5% 6% 54%	2080
	21st to end	Night	12% 8% 2 7% 5% 5% 4 3 5% 7% 43%	2090
October	1st to 10th	Night	18% 6% 2 5% 4 3 3 3 4 7% 45%	2090
	11th to 20th	Night	23% 12% 3 7% 4 4 3 2 4 6% 34%	2333
	21st to end	Night	26% 11% 3 7% 3 3 3 3 4 5% 31%	2717
November	1st to 10th	Night	17% 13% 3 6% 5% 4 4 2 4 6% 35%	2536
	11th to 20th	Night	19% 19% 6% 10% 5% 4 3 3 5% 5% 21%	2600
	21st to end	Night	18% 22% 7% 11% 4 3 4 3 3 5% 21%	2600
December	1st to 10th	Night	13% 27% 9% 16% 6% 4 3 3 4 4 13%	4547
	11th to 20th	Night	17% 27% 9% 16% 6% 3 3 2 3 3 10%	5199
	21st to end	Night	24% 23% 6% 11% 4 4 4 3 4 5% 12%	6996

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	80% 7% 5% 7% 1	3618
	11th to 20th	Day	86% 5% 5% 3 1	3620
	21st to end	Day	79% 5% 8% 7% 2	3982
February	1st to 10th	Day	71% 6% 7% 12% 3	1831
	11th to 20th	Day	67% 5% 10% 12% 5% 1	1958
	21st to end	Day	61% 7% 13% 13% 5%	1650
March	1st to 10th	Day	51% 5% 15% 19% 9% 1	4480
	11th to 20th	Day	44% 5% 18% 22% 10% 1	4790
	21st to end	Day	59% 4 11% 16% 10% 1	5753
April	1st to 10th	Day	53% 6% 11% 19% 11% 1	2400
	11th to 20th	Day	46% 6% 10% 22% 14% 2	2408
	21st to end	Day	45% 6% 13% 20% 14% 2	2600
May	1st to 10th	Day	41% 6% 12% 22% 16% 2	5897
	11th to 20th	Day	38% 8% 14% 22% 15% 2	5953
	21st to end	Day	35% 6% 11% 28% 18% 1	6949
June	1st to 10th	Day	33% 6% 12% 28% 18% 2	2787
	11th to 20th	Day	31% 8% 14% 24% 21% 1	2660
	21st to end	Day	34% 7% 15% 24% 18% 2	2660
July	1st to 10th	Day	41% 6% 13% 24% 14% 3	4371
	11th to 20th	Day	25% 6% 15% 33% 19% 2	4365
	21st to end	Day	31% 6% 17% 22% 21% 2	4662
August	1st to 10th	Day	35% 6% 13% 31% 14% 1	4184
	11th to 20th	Day	31% 7% 13% 31% 16% 1	4068
	21st to end	Day	33% 5% 15% 27% 18% 2	4179
September	1st to 10th	Day	34% 7% 15% 27% 14% 2	2271
	11th to 20th	Day	32% 7% 13% 30% 16% 2	2090
	21st to end	Day	41% 6% 12% 24% 16%	2090
October	1st to 10th	Day	29% 5% 8% 39% 18% 1	3480
	11th to 20th	Day	43% 7% 13% 23% 14%	3031
	21st to end	Day	52% 5% 14% 21% 8% 1	3081
November	1st to 10th	Day	51% 7% 12% 19% 10% 1	1762
	11th to 20th	Day	67% 6% 9% 13% 5% 1	1800
	21st to end	Day	69% 5% 12% 11% 4	1800
December	1st to 10th	Day	76% 7% 9% 7% 2	2625
	11th to 20th	Day	81% 5% 8% 5% 1	3005
	21st to end	Day	77% 6% 5% 9% 3	3982
January	1st to 10th	Night	79% 5% 6% 7% 2	6348
	11th to 20th	Night	88% 4 4 3 1	6360
	21st to end	Night	79% 5% 9% 6% 2	6996
February	1st to 10th	Night	71% 5% 9% 10% 5%	2562
	11th to 20th	Night	68% 6% 7% 14% 6%	2339
	21st to end	Night	63% 6% 12% 13% 6% 1	1980
March	1st to 10th	Night	48% 6% 13% 23% 8% 1	5373
	11th to 20th	Night	39% 6% 14% 27% 11% 2	5169
	21st to end	Night	55% 5% 9% 18% 12% 1	5220
April	1st to 10th	Night	48% 7% 11% 19% 14% 1	2000
	11th to 20th	Night	49% 5% 8% 18% 18% 3	1941
	21st to end	Night	44% 7% 11% 19% 15% 4	1800
May	1st to 10th	Night	50% 6% 11% 16% 15% 3	4060
	11th to 20th	Night	41% 7% 11% 21% 15% 4	3946
	21st to end	Night	43% 6% 7% 21% 19% 3	3950
June	1st to 10th	Night	36% 7% 10% 27% 17% 3	1597
	11th to 20th	Night	36% 6% 11% 25% 20% 2	1520
	21st to end	Night	35% 8% 14% 24% 16% 3	1520
July	1st to 10th	Night	40% 6% 11% 24% 12% 7%	2490
	11th to 20th	Night	27% 6% 13% 27% 25% 2	2482
	21st to end	Night	34% 6% 12% 20% 26% 3	2662
August	1st to 10th	Night	33% 6% 13% 29% 19% 1	2723
	11th to 20th	Night	32% 7% 9% 32% 18% 1	2812
	21st to end	Night	36% 6% 10% 25% 21% 2	3474
September	1st to 10th	Night	34% 6% 13% 26% 18% 3	1900
	11th to 20th	Night	30% 6% 11% 32% 20% 2	2080
	21st to end	Night	42% 7% 11% 25% 13% 1	2090
October	1st to 10th	Night	31% 4 8% 34% 21% 2	3480
	11th to 20th	Night	42% 5% 12% 24% 17%	3882
	21st to end	Night	46% 5% 10% 26% 14%	4467
November	1st to 10th	Night	51% 7% 9% 20% 11% 1	2536
	11th to 20th	Night	65% 6% 10% 13% 6% 1	2600
	21st to end	Night	66% 6% 12% 13% 2	2600
December	1st to 10th	Night	75% 7% 10% 6% 2	4547
	11th to 20th	Night	80% 5% 8% 5% 2	5201
	21st to end	Night	74% 6% 9% 9% 3	6996

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	21% 12% 35% 24% 5% 2	300
	11th to 20th	Day	22% 18% 31% 22% 6% 1	300
	21st to end	Day	27% 13% 29% 25% 5% 1	330
February	1st to 10th	Day	19% 17% 37% 19% 7% 2	300
	11th to 20th	Day	20% 18% 34% 20% 7% 1	300
	21st to end	Day	24% 12% 40% 18% 5%	249
March	1st to 10th	Day	19% 15% 38% 20% 7%	300
	11th to 20th	Day	19% 14% 30% 26% 11% 1	414
	21st to end	Day	27% 11% 26% 27% 8% 1	550
April	1st to 10th	Day	24% 10% 30% 27% 8%	500
	11th to 20th	Day	21% 15% 29% 24% 8% 3	492
	21st to end	Day	22% 8% 29% 26% 12% 2	500
May	1st to 10th	Day	20% 9% 28% 29% 11% 2	503
	11th to 20th	Day	17% 6% 22% 31% 19% 4	563
	21st to end	Day	14% 5% 23% 30% 22% 6%	789
June	1st to 10th	Day	11% 4 26% 35% 20% 4	726
	11th to 20th	Day	12% 5% 21% 37% 20% 5%	680
	21st to end	Day	12% 6% 23% 38% 17% 4	680
July	1st to 10th	Day	7% 3 20% 33% 27% 11%	671
	11th to 20th	Day	8% 3 21% 36% 24% 8%	668
	21st to end	Day	9% 1 18% 42% 23% 7%	739
August	1st to 10th	Day	11% 4 14% 30% 30% 12%	543
	11th to 20th	Day	11% 5% 14% 30% 29% 12%	479
	21st to end	Day	10% 4 15% 31% 29% 11%	539
September	1st to 10th	Day	14% 5% 15% 32% 25% 9%	490
	11th to 20th	Day	8% 4 14% 28% 29% 17%	490
	21st to end	Day	15% 7% 22% 22% 23% 10%	490
October	1st to 10th	Day	18% 7% 25% 25% 18% 7%	490
	11th to 20th	Day	25% 16% 24% 28% 7% 1	363
	21st to end	Day	32% 10% 31% 20% 5% 2	330
November	1st to 10th	Day	23% 17% 25% 24% 9% 2	300
	11th to 20th	Day	26% 20% 32% 19% 4	300
	21st to end	Day	28% 14% 38% 16% 4	300
December	1st to 10th	Day	25% 22% 27% 19% 6% 1	300
	11th to 20th	Day	22% 23% 30% 20% 5% 1	300
	21st to end	Day	28% 18% 32% 16% 3 2	330
January	1st to 10th	Night	23% 16% 31% 23% 7%	1000
	11th to 20th	Night	25% 14% 31% 23% 6% 1	1000
	21st to end	Night	23% 11% 33% 27% 6%	1100
February	1st to 10th	Night	21% 11% 35% 26% 5% 1	862
	11th to 20th	Night	23% 11% 33% 26% 7%	783
	21st to end	Night	24% 13% 36% 23% 4	660
March	1st to 10th	Night	20% 10% 30% 31% 8% 1	800
	11th to 20th	Night	16% 9% 32% 32% 9% 1	800
	21st to end	Night	22% 8% 28% 30% 12% 1	775
April	1st to 10th	Night	18% 8% 32% 32% 8% 1	600
	11th to 20th	Night	25% 10% 24% 32% 10% 1	593
	21st to end	Night	19% 6% 29% 35% 11% 2	600
May	1st to 10th	Night	18% 5% 25% 37% 13% 2	600
	11th to 20th	Night	20% 3 22% 32% 21% 1	591
	21st to end	Night	16% 3 18% 35% 24% 4	650
June	1st to 10th	Night	12% 2 21% 41% 22% 2	599
	11th to 20th	Night	11% 4 22% 37% 24% 2	570
	21st to end	Night	11% 4 17% 39% 28% 2	570
July	1st to 10th	Night	9% 2 13% 35% 36% 6%	555
	11th to 20th	Night	7% 2 14% 39% 32% 5%	552
	21st to end	Night	9% 1 13% 39% 34% 3	624
August	1st to 10th	Night	8% 2 12% 40% 32% 6%	567
	11th to 20th	Night	11% 3 11% 37% 31% 7%	564
	21st to end	Night	11% 2 14% 37% 32% 4	627
September	1st to 10th	Night	12% 3 15% 37% 28% 5%	570
	11th to 20th	Night	12% 3 13% 34% 31% 7%	750
	21st to end	Night	15% 6% 23% 26% 24% 6%	760
October	1st to 10th	Night	22% 4 21% 31% 20% 3	760
	11th to 20th	Night	29% 10% 23% 25% 11% 1	760
	21st to end	Night	31% 10% 30% 22% 7% 1	836
November	1st to 10th	Night	24% 10% 29% 26% 11% 1	780
	11th to 20th	Night	28% 16% 31% 20% 5%	800
	21st to end	Night	28% 14% 30% 24% 5%	800
December	1st to 10th	Night	28% 15% 32% 19% 6%	980
	11th to 20th	Night	28% 14% 34% 20% 5%	1000
	21st to end	Night	32% 11% 35% 19% 2	1100

Page generated at 2025-06-07 10:28:19. Version ac07

Copyright © 2025 Attilla Danko.