J.S.M. Blue Lake Township Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the J.S.M. Blue Lake Township Observatory clear sky chart from 2005-11-06 to 2024-11-12.

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% 4 4 5% 6% 31%	101248
	Night	13% 13% 5% 11% 6% 5% 4 3 4 6% 29%	98041
Transparency	Day	51% 7% 11% 19% 11% 1	104758
	Night	54% 8% 11% 17% 9% 1	102619
Seeing	Day	19% 15% 30% 22% 10% 4	15672
	Night	18% 12% 31% 28% 9% 1	25326

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	11% 22% 11% 25% 7% 5% 4 2 3 2 8%	2527
	11th to 20th	Day	12% 19% 7% 18% 13% 13% 5% 3 3 2 5%	2530
	21st to end	Day	16% 22% 11% 17% 7% 4 5% 3 3 4 9%	2783
February	1st to 10th	Day	9% 18% 8% 15% 15% 8% 5% 2 4 5% 11%	1657
	11th to 20th	Day	10% 17% 6% 17% 11% 6% 4 4 4 4 17%	1816
	21st to end	Day	11% 18% 8% 15% 9% 5% 3 3 4 5% 18%	1570
March	1st to 10th	Day	11% 14% 4 11% 6% 4 4 4 5% 5% 31%	3118
	11th to 20th	Day	9% 12% 7% 18% 6% 5% 5% 3 5% 6% 25%	3432
	21st to end	Day	16% 14% 6% 17% 6% 5% 4 3 4 4 21%	3902
April	1st to 10th	Day	17% 15% 5% 10% 5% 4 4 4 4 5% 27%	2280
	11th to 20th	Day	19% 15% 4 7% 4 3 3 3 4 6% 32%	2374
	21st to end	Day	15% 13% 4 9% 4 4 4 4 6% 7% 30%	2470
May	1st to 10th	Day	15% 9% 3 7% 4 4 4 3 5% 7% 39%	4108
	11th to 20th	Day	11% 8% 2 5% 4 4 4 4 5% 7% 45%	4167
	21st to end	Day	13% 6% 2 5% 5% 4 4 4 5% 8% 43%	4837
June	1st to 10th	Day	14% 7% 2 6% 5% 5% 4 4 6% 8% 40%	2817
	11th to 20th	Day	13% 6% 2 6% 4 5% 5% 4 7% 8% 38%	2850
	21st to end	Day	15% 7% 2 7% 4 4 4 4 7% 8% 38%	2806
July	1st to 10th	Day	17% 7% 3 6% 4 3 4 4 6% 8% 36%	4440
	11th to 20th	Day	9% 6% 1 5% 4 5% 5% 4 7% 8% 46%	4440
	21st to end	Day	9% 6% 2 6% 4 4 5% 5% 7% 9% 44%	4814
August	1st to 10th	Day	9% 6% 3 7% 5% 6% 6% 5% 8% 9% 37%	4199
	11th to 20th	Day	14% 7% 2 5% 4 4 4 4 5% 6% 44%	4044
	21st to end	Day	14% 7% 2 7% 5% 4 4 3 5% 6% 42%	4404
September	1st to 10th	Day	14% 6% 3 6% 4 4 4 3 6% 8% 41%	2233
	11th to 20th	Day	13% 6% 2 6% 4 3 4 3 6% 8% 45%	2090
	21st to end	Day	16% 8% 3 7% 4 4 5% 3 6% 8% 36%	2090
October	1st to 10th	Day	18% 11% 4 8% 4 4 4 3 5% 6% 35%	2081
	11th to 20th	Day	23% 17% 4 9% 5% 4 4 4 4 5% 21%	1815
	21st to end	Day	21% 18% 5% 10% 6% 5% 5% 3 5% 6% 16%	1881
November	1st to 10th	Day	16% 18% 5% 7% 5% 4 4 3 5% 6% 25%	1762
	11th to 20th	Day	13% 22% 8% 13% 6% 4 6% 3 5% 5% 16%	1719
	21st to end	Day	16% 23% 10% 14% 6% 3 4 3 3 5% 15%	1568
December	1st to 10th	Day	13% 21% 11% 18% 8% 6% 4 2 4 3 10%	1330
	11th to 20th	Day	14% 23% 8% 18% 9% 4 4 3 4 4 11%	1671
	21st to end	Day	19% 22% 10% 22% 7% 4 3 2 2 3 7%	2623
January	1st to 10th	Night	13% 19% 11% 22% 6% 6% 4 2 2 3 13%	4428
	11th to 20th	Night	11% 16% 7% 19% 13% 12% 6% 3 3 3 8%	4440
	21st to end	Night	14% 20% 10% 20% 9% 6% 4 3 3 3 8%	4884
February	1st to 10th	Night	9% 17% 7% 14% 13% 9% 6% 3 4 4 14%	2523
	11th to 20th	Night	11% 15% 7% 18% 8% 6% 5% 3 4 5% 18%	2247
	21st to end	Night	13% 16% 6% 14% 9% 4 4 3 4 5% 22%	1884
March	1st to 10th	Night	13% 10% 4 8% 4 4 3 3 4 7% 39%	3722
	11th to 20th	Night	8% 14% 6% 11% 5% 5% 4 4 5% 6% 34%	3527
	21st to end	Night	13% 14% 6% 12% 6% 3 4 3 5% 5% 28%	3759
April	1st to 10th	Night	18% 13% 4 9% 5% 4 5% 4 5% 5% 28%	1900
	11th to 20th	Night	20% 12% 4 6% 4 4 4 4 4 6% 33%	1754
	21st to end	Night	16% 11% 4 8% 5% 3 3 4 6% 6% 35%	1710
May	1st to 10th	Night	15% 8% 3 7% 5% 4 4 4 5% 7% 40%	2833
	11th to 20th	Night	12% 9% 3 7% 5% 4 4 5% 5% 7% 41%	2726
	21st to end	Night	17% 7% 3 5% 3 4 4 3 6% 7% 42%	2750
June	1st to 10th	Night	12% 7% 3 6% 5% 4 4 4 5% 7% 42%	1359
	11th to 20th	Night	8% 5% 2 7% 5% 4 6% 4 7% 8% 44%	1330
	21st to end	Night	11% 9% 2 5% 4 3 4 4 5% 7% 44%	1367
July	1st to 10th	Night	12% 7% 2 8% 4 4 5% 4 6% 8% 41%	2530
	11th to 20th	Night	8% 4 2 5% 4 3 5% 4 6% 7% 52%	2530
	21st to end	Night	8% 6% 3 6% 4 3 4 4 6% 7% 50%	2750
August	1st to 10th	Night	11% 7% 2 6% 4 5% 5% 3 6% 8% 42%	2732
	11th to 20th	Night	15% 6% 2 5% 3 3 3 3 4 6% 50%	2785
	21st to end	Night	10% 7% 2 6% 4 4 5% 4 6% 7% 46%	3249
September	1st to 10th	Night	11% 6% 2 6% 3 3 3 3 5% 7% 50%	1928
	11th to 20th	Night	14% 5% 2 5% 4 3 4 3 4 8% 49%	2090
	21st to end	Night	17% 8% 2 7% 4 4 4 4 6% 6% 38%	2090
October	1st to 10th	Night	17% 8% 3 7% 3 3 4 3 6% 5% 40%	2098
	11th to 20th	Night	20% 14% 4 8% 5% 4 4 4 4 6% 27%	2361
	21st to end	Night	23% 15% 3 9% 5% 5% 5% 4 4 5% 23%	2717
November	1st to 10th	Night	13% 18% 5% 9% 5% 5% 4 3 4 7% 27%	2536
	11th to 20th	Night	14% 19% 7% 13% 6% 5% 5% 3 4 5% 19%	2484
	21st to end	Night	16% 20% 9% 13% 5% 5% 4 4 4 5% 15%	2602
December	1st to 10th	Night	12% 22% 9% 20% 7% 5% 4 3 3 4 10%	2850
	11th to 20th	Night	12% 20% 8% 20% 9% 5% 4 3 5% 4 11%	3526
	21st to end	Night	20% 24% 9% 17% 6% 4 3 3 3 3 8%	5040

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% 8% 5% 5% 2	2528
	11th to 20th	Day	84% 6% 6% 3 1	2530
	21st to end	Day	79% 8% 7% 4 2	2783
February	1st to 10th	Day	75% 6% 8% 9% 2	1657
	11th to 20th	Day	69% 7% 9% 10% 5% 1	1826
	21st to end	Day	66% 6% 10% 14% 3 1	1570
March	1st to 10th	Day	53% 6% 13% 18% 9% 1	3120
	11th to 20th	Day	56% 8% 12% 17% 5% 2	3432
	21st to end	Day	62% 8% 9% 13% 7% 1	3902
April	1st to 10th	Day	58% 6% 10% 16% 9% 1	2280
	11th to 20th	Day	53% 5% 10% 19% 12% 1	2374
	21st to end	Day	51% 8% 12% 13% 14% 3	2470
May	1st to 10th	Day	42% 8% 12% 19% 18% 2	4120
	11th to 20th	Day	35% 8% 13% 26% 16% 2	4171
	21st to end	Day	36% 8% 12% 21% 20% 2	4837
June	1st to 10th	Day	39% 8% 12% 25% 14% 2	2817
	11th to 20th	Day	39% 9% 13% 21% 17% 1	2850
	21st to end	Day	42% 7% 14% 23% 13% 1	2806
July	1st to 10th	Day	44% 7% 14% 20% 14% 1	4371
	11th to 20th	Day	31% 8% 14% 33% 13% 1	4365
	21st to end	Day	33% 8% 14% 27% 17% 1	4662
August	1st to 10th	Day	38% 10% 14% 25% 12% 1	4184
	11th to 20th	Day	39% 8% 11% 29% 13% 1	4083
	21st to end	Day	41% 7% 13% 28% 9% 1	4403
September	1st to 10th	Day	40% 7% 12% 24% 15% 1	2233
	11th to 20th	Day	35% 8% 16% 27% 13% 1	2090
	21st to end	Day	45% 7% 15% 23% 10%	2090
October	1st to 10th	Day	36% 5% 8% 34% 17%	3458
	11th to 20th	Day	54% 7% 8% 19% 12%	2992
	21st to end	Day	64% 7% 11% 15% 3	3081
November	1st to 10th	Day	58% 7% 11% 17% 7%	1762
	11th to 20th	Day	68% 9% 11% 8% 4	1719
	21st to end	Day	73% 6% 11% 9% 2	1568
December	1st to 10th	Day	79% 7% 6% 7% 1 1	1330
	11th to 20th	Day	77% 7% 8% 6% 1	1671
	21st to end	Day	83% 6% 5% 3 2	2623
January	1st to 10th	Night	75% 7% 8% 8% 2	4428
	11th to 20th	Night	79% 9% 6% 5% 2	4440
	21st to end	Night	79% 10% 6% 4 1	4884
February	1st to 10th	Night	72% 7% 7% 9% 4 1	2523
	11th to 20th	Night	65% 7% 10% 13% 4	2248
	21st to end	Night	64% 6% 11% 14% 5%	1884
March	1st to 10th	Night	45% 6% 17% 22% 10% 1	3733
	11th to 20th	Night	48% 9% 12% 22% 8% 1	3528
	21st to end	Night	56% 8% 10% 18% 8% 1	3759
April	1st to 10th	Night	54% 8% 10% 17% 10% 1	1900
	11th to 20th	Night	51% 6% 9% 19% 13% 2	1754
	21st to end	Night	48% 7% 11% 18% 14% 3	1710
May	1st to 10th	Night	41% 8% 12% 19% 16% 3	2840
	11th to 20th	Night	39% 9% 10% 25% 17% 1	2727
	21st to end	Night	39% 8% 14% 19% 15% 5%	2751
June	1st to 10th	Night	39% 8% 12% 23% 17% 1	1359
	11th to 20th	Night	34% 8% 14% 26% 15% 2	1330
	21st to end	Night	37% 9% 12% 25% 15% 2	1367
July	1st to 10th	Night	39% 7% 14% 24% 14% 3	2490
	11th to 20th	Night	28% 8% 14% 32% 17% 1	2482
	21st to end	Night	32% 9% 15% 26% 18%	2662
August	1st to 10th	Night	37% 8% 16% 26% 12% 1	2723
	11th to 20th	Night	34% 6% 16% 30% 13%	2812
	21st to end	Night	35% 8% 15% 25% 16% 1	3249
September	1st to 10th	Night	33% 8% 13% 27% 17% 1	1928
	11th to 20th	Night	34% 7% 16% 29% 13% 1	2090
	21st to end	Night	45% 7% 15% 22% 9%	2090
October	1st to 10th	Night	36% 7% 12% 30% 14%	3501
	11th to 20th	Night	45% 7% 11% 22% 14%	3923
	21st to end	Night	55% 7% 13% 20% 4	4467
November	1st to 10th	Night	55% 8% 13% 17% 7% 1	2536
	11th to 20th	Night	64% 8% 12% 10% 5% 1	2484
	21st to end	Night	70% 8% 12% 8% 1	2602
December	1st to 10th	Night	76% 9% 7% 7% 2	2850
	11th to 20th	Night	74% 9% 9% 6% 2	3525
	21st to end	Night	78% 10% 6% 3 2	5040

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	20% 20% 39% 16% 6%	270
	11th to 20th	Day	24% 21% 35% 17% 2	270
	21st to end	Day	22% 15% 38% 19% 5%	297
February	1st to 10th	Day	18% 29% 38% 10% 4 1	270
	11th to 20th	Day	21% 29% 34% 14% 2	270
	21st to end	Day	25% 28% 38% 8% 1	225
March	1st to 10th	Day	21% 27% 36% 14% 2	270
	11th to 20th	Day	22% 15% 38% 17% 7%	425
	21st to end	Day	25% 16% 31% 21% 7% 1	506
April	1st to 10th	Day	25% 18% 34% 17% 6% 1	460
	11th to 20th	Day	31% 18% 28% 12% 9% 2	452
	21st to end	Day	24% 15% 31% 19% 10% 2	460
May	1st to 10th	Day	22% 20% 29% 17% 9% 3	463
	11th to 20th	Day	18% 12% 30% 28% 9% 4	534
	21st to end	Day	14% 13% 29% 29% 11% 4	734
June	1st to 10th	Day	15% 14% 33% 24% 10% 3	680
	11th to 20th	Day	16% 13% 31% 26% 10% 3	680
	21st to end	Day	19% 9% 29% 29% 11% 2	680
July	1st to 10th	Day	10% 9% 28% 32% 15% 7%	671
	11th to 20th	Day	12% 9% 28% 28% 16% 6%	668
	21st to end	Day	10% 6% 31% 31% 17% 5%	739
August	1st to 10th	Day	9% 7% 26% 28% 20% 10%	543
	11th to 20th	Day	15% 6% 19% 30% 18% 12%	479
	21st to end	Day	18% 9% 22% 29% 15% 6%	539
September	1st to 10th	Day	18% 8% 26% 24% 16% 8%	490
	11th to 20th	Day	12% 9% 21% 30% 19% 9%	490
	21st to end	Day	19% 11% 23% 27% 14% 5%	490
October	1st to 10th	Day	23% 17% 26% 21% 12% 2	490
	11th to 20th	Day	30% 16% 34% 17% 2	405
	21st to end	Day	32% 23% 30% 11% 4 1	330
November	1st to 10th	Day	26% 20% 33% 16% 4 1	300
	11th to 20th	Day	20% 26% 35% 16% 2	273
	21st to end	Day	21% 28% 35% 14% 2	207
December	1st to 10th	Day	27% 17% 38% 11% 4 2	180
	11th to 20th	Day	27% 20% 40% 12% 1 1	180
	21st to end	Day	26% 28% 35% 10% 1 1	252
January	1st to 10th	Night	18% 17% 36% 21% 6% 1	950
	11th to 20th	Night	21% 17% 35% 21% 6%	950
	21st to end	Night	16% 13% 38% 27% 5% 1	1045
February	1st to 10th	Night	15% 18% 38% 24% 4	813
	11th to 20th	Night	18% 21% 33% 23% 5%	743
	21st to end	Night	22% 17% 36% 23% 3	628
March	1st to 10th	Night	15% 14% 39% 24% 8% 1	760
	11th to 20th	Night	17% 16% 37% 24% 5%	760
	21st to end	Night	19% 12% 31% 30% 7% 1	803
April	1st to 10th	Night	22% 13% 35% 24% 5% 1	570
	11th to 20th	Night	24% 12% 32% 25% 7%	563
	21st to end	Night	18% 12% 32% 30% 8% 1	570
May	1st to 10th	Night	16% 10% 33% 32% 8%	570
	11th to 20th	Night	17% 10% 30% 33% 9% 1	561
	21st to end	Night	14% 7% 27% 37% 14% 1	617
June	1st to 10th	Night	14% 7% 31% 38% 8% 1	409
	11th to 20th	Night	8% 6% 29% 45% 11%	380
	21st to end	Night	13% 7% 28% 38% 13% 1	417
July	1st to 10th	Night	9% 3 21% 46% 20% 1	555
	11th to 20th	Night	9% 4 24% 37% 25% 2	552
	21st to end	Night	10% 4 24% 37% 23% 1	624
August	1st to 10th	Night	11% 4 18% 43% 23% 1	567
	11th to 20th	Night	11% 5% 17% 36% 27% 3	564
	21st to end	Night	14% 6% 21% 39% 20% 1	627
September	1st to 10th	Night	15% 3 24% 34% 20% 4	598
	11th to 20th	Night	16% 6% 20% 34% 20% 4	760
	21st to end	Night	19% 9% 23% 32% 15% 3	760
October	1st to 10th	Night	21% 9% 27% 31% 11% 1	760
	11th to 20th	Night	28% 13% 29% 24% 6%	760
	21st to end	Night	31% 14% 29% 21% 5% 1	836
November	1st to 10th	Night	23% 14% 32% 25% 6% 1	780
	11th to 20th	Night	22% 17% 38% 20% 4	765
	21st to end	Night	24% 14% 38% 21% 3	764
December	1st to 10th	Night	20% 17% 39% 20% 3	950
	11th to 20th	Night	20% 18% 40% 18% 3 1	950
	21st to end	Night	25% 17% 38% 18% 2	1045

Page generated at 2024-11-08 22:45:36. Version ac07

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