Longway Planetarium
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Longway Planetarium clear sky chart from 2005-11-06 to 2024-11-08.

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% 10% 3 8% 5% 5% 5% 4 6% 7% 33%	100998
	Night	15% 11% 4 8% 5% 4 4 3 5% 6% 34%	98086
Transparency	Day	49% 4 11% 22% 13% 1	104597
	Night	50% 3 11% 22% 12% 1	102627
Seeing	Day	20% 12% 29% 22% 13% 5%	15500
	Night	20% 10% 29% 29% 11% 1	25245

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	15% 19% 6% 12% 5% 5% 4 3 4 5% 21%	2527
	11th to 20th	Day	15% 20% 7% 16% 10% 9% 3 2 4 4 9%	2530
	21st to end	Day	25% 21% 6% 12% 6% 5% 3 2 4 4 12%	2973
February	1st to 10th	Day	13% 15% 6% 13% 8% 4 5% 4 5% 7% 20%	1710
	11th to 20th	Day	12% 15% 6% 13% 8% 5% 4 3 4 6% 23%	1796
	21st to end	Day	14% 17% 5% 11% 7% 4 5% 3 5% 5% 24%	1570
March	1st to 10th	Day	17% 15% 4 9% 5% 4 3 3 5% 6% 29%	3172
	11th to 20th	Day	12% 14% 5% 10% 7% 4 4 4 5% 6% 29%	3480
	21st to end	Day	17% 14% 4 10% 6% 4 4 3 4 5% 28%	3815
April	1st to 10th	Day	17% 14% 3 7% 5% 4 5% 3 5% 6% 30%	2233
	11th to 20th	Day	18% 10% 2 7% 4 4 4 4 5% 7% 35%	2403
	21st to end	Day	17% 9% 3 8% 5% 5% 5% 3 5% 6% 34%	2470
May	1st to 10th	Day	18% 9% 3 7% 3 4 5% 3 6% 7% 36%	4082
	11th to 20th	Day	17% 8% 2 6% 4 5% 4 5% 6% 8% 36%	4081
	21st to end	Day	10% 6% 3 6% 5% 4 4 3 5% 8% 46%	4567
June	1st to 10th	Day	11% 7% 2 6% 5% 5% 5% 4 6% 8% 41%	2745
	11th to 20th	Day	11% 7% 2 7% 5% 5% 4 4 6% 8% 41%	2850
	21st to end	Day	11% 7% 2 6% 4 6% 6% 5% 7% 9% 38%	2714
July	1st to 10th	Day	11% 6% 3 7% 4 5% 6% 5% 7% 9% 37%	4440
	11th to 20th	Day	8% 4 2 5% 4 4 4 4 7% 10% 49%	4440
	21st to end	Day	8% 5% 2 6% 5% 6% 5% 4 7% 10% 41%	4629
August	1st to 10th	Day	12% 5% 2 6% 5% 5% 5% 4 7% 8% 40%	4104
	11th to 20th	Day	12% 6% 2 6% 5% 5% 5% 4 7% 8% 39%	4044
	21st to end	Day	9% 5% 2 7% 5% 6% 5% 5% 6% 9% 41%	4473
September	1st to 10th	Day	10% 6% 3 6% 6% 6% 5% 5% 6% 7% 40%	2166
	11th to 20th	Day	11% 5% 3 5% 3 4 4 4 5% 8% 48%	2090
	21st to end	Day	15% 8% 3 5% 5% 5% 5% 4 6% 8% 36%	2090
October	1st to 10th	Day	13% 7% 2 7% 5% 5% 4 3 5% 7% 40%	2046
	11th to 20th	Day	19% 10% 3 7% 5% 4 4 4 5% 6% 31%	1900
	21st to end	Day	22% 11% 2 7% 5% 5% 5% 4 5% 7% 28%	1906
November	1st to 10th	Day	11% 11% 4 9% 6% 4 4 4 5% 7% 35%	1735
	11th to 20th	Day	13% 13% 5% 9% 6% 5% 5% 3 5% 7% 28%	1710
	21st to end	Day	18% 14% 5% 9% 5% 5% 4 3 5% 6% 25%	1600
December	1st to 10th	Day	13% 18% 7% 14% 6% 5% 4 3 5% 5% 20%	1520
	11th to 20th	Day	15% 20% 4 9% 6% 4 5% 4 7% 6% 22%	1687
	21st to end	Day	24% 24% 6% 13% 5% 4 3 3 4 4 12%	2700
January	1st to 10th	Night	16% 17% 8% 12% 5% 5% 4 3 4 5% 22%	4428
	11th to 20th	Night	15% 18% 8% 15% 7% 9% 4 3 4 4 13%	4440
	21st to end	Night	22% 18% 8% 11% 5% 4 4 3 4 5% 16%	4685
February	1st to 10th	Night	15% 16% 4 12% 7% 6% 5% 4 4 5% 22%	2470
	11th to 20th	Night	14% 14% 5% 11% 6% 6% 4 4 6% 5% 26%	2267
	21st to end	Night	17% 12% 5% 10% 6% 4 4 4 5% 5% 27%	1884
March	1st to 10th	Night	14% 14% 5% 8% 4 3 3 2 4 6% 37%	3680
	11th to 20th	Night	10% 10% 3 7% 5% 4 4 4 6% 8% 40%	3480
	21st to end	Night	16% 11% 5% 9% 5% 4 4 3 4 6% 34%	3817
April	1st to 10th	Night	18% 12% 3 7% 4 4 3 4 5% 7% 34%	1962
	11th to 20th	Night	18% 8% 3 7% 5% 4 4 4 5% 6% 37%	1725
	21st to end	Night	18% 8% 2 7% 4 4 4 4 6% 7% 36%	1710
May	1st to 10th	Night	14% 9% 3 8% 4 4 4 3 6% 9% 37%	2813
	11th to 20th	Night	16% 7% 3 6% 5% 4 3 3 4 6% 43%	2812
	21st to end	Night	12% 6% 2 5% 4 4 4 4 4 7% 48%	2986
June	1st to 10th	Night	12% 5% 1 7% 4 4 4 3 5% 9% 46%	1425
	11th to 20th	Night	10% 5% 2 5% 4 4 5% 4 6% 8% 45%	1330
	21st to end	Night	9% 6% 2 6% 4 3 4 3 5% 9% 47%	1455
July	1st to 10th	Night	8% 5% 2 6% 4 5% 5% 4 7% 11% 44%	2530
	11th to 20th	Night	10% 4 1 4 4 3 4 3 5% 8% 53%	2530
	21st to end	Night	6% 4 2 6% 5% 5% 5% 5% 7% 9% 47%	2926
August	1st to 10th	Night	11% 5% 2 5% 4 5% 4 4 6% 7% 48%	2825
	11th to 20th	Night	11% 5% 2 6% 4 5% 5% 4 5% 7% 47%	2785
	21st to end	Night	8% 6% 2 6% 4 4 4 4 6% 7% 48%	3180
September	1st to 10th	Night	11% 6% 2 4 4 4 4 4 7% 6% 47%	1995
	11th to 20th	Night	11% 4 1 5% 3 3 4 3 5% 7% 53%	2090
	21st to end	Night	16% 6% 2 6% 4 4 4 4 6% 7% 41%	2090
October	1st to 10th	Night	15% 6% 2 7% 4 3 4 3 5% 6% 44%	2133
	11th to 20th	Night	21% 10% 3 7% 4 4 5% 3 5% 5% 33%	2280
	21st to end	Night	22% 10% 3 8% 6% 4 4 3 5% 6% 31%	2688
November	1st to 10th	Night	14% 10% 2 7% 4 4 4 3 6% 6% 40%	2504
	11th to 20th	Night	15% 13% 4 8% 5% 4 6% 4 5% 7% 29%	2470
	21st to end	Night	20% 14% 4 7% 5% 4 5% 3 5% 6% 27%	2576
December	1st to 10th	Night	17% 18% 7% 10% 6% 5% 5% 4 4 6% 19%	2660
	11th to 20th	Night	15% 15% 6% 12% 6% 5% 5% 3 5% 5% 24%	3507
	21st to end	Night	24% 24% 6% 11% 4 4 3 2 4 4 13%	4948

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	68% 2 12% 13% 4	2528
	11th to 20th	Day	80% 3 9% 6% 2	2530
	21st to end	Day	78% 2 9% 7% 4 1	2973
February	1st to 10th	Day	63% 5% 10% 15% 7%	1710
	11th to 20th	Day	64% 3 8% 16% 9% 1	1806
	21st to end	Day	62% 3 11% 15% 7% 1	1570
March	1st to 10th	Day	57% 2 11% 22% 7% 1	3172
	11th to 20th	Day	56% 2 11% 20% 9% 1	3480
	21st to end	Day	59% 2 11% 16% 10% 2	3815
April	1st to 10th	Day	55% 3 10% 21% 11%	2233
	11th to 20th	Day	50% 3 11% 21% 14% 2	2403
	21st to end	Day	51% 4 11% 19% 14% 1	2470
May	1st to 10th	Day	48% 3 9% 23% 14% 2	4120
	11th to 20th	Day	47% 2 13% 27% 10% 1	4085
	21st to end	Day	39% 3 11% 20% 24% 4	4580
June	1st to 10th	Day	40% 5% 11% 27% 16% 2	2745
	11th to 20th	Day	40% 4 11% 26% 17% 2	2850
	21st to end	Day	40% 5% 12% 25% 15% 1	2714
July	1st to 10th	Day	42% 5% 13% 21% 16% 2	4371
	11th to 20th	Day	29% 5% 13% 35% 17% 1	4365
	21st to end	Day	37% 6% 14% 19% 22% 2	4482
August	1st to 10th	Day	39% 5% 13% 24% 17% 1	4091
	11th to 20th	Day	40% 6% 11% 30% 13% 1	4083
	21st to end	Day	38% 6% 13% 29% 14% 1	4472
September	1st to 10th	Day	41% 6% 12% 27% 12% 2	2166
	11th to 20th	Day	35% 3 12% 33% 15% 2	2090
	21st to end	Day	46% 4 12% 25% 13%	2090
October	1st to 10th	Day	33% 3 10% 34% 18% 2	3397
	11th to 20th	Day	41% 3 11% 28% 16%	3140
	21st to end	Day	49% 4 13% 24% 10% 1	3118
November	1st to 10th	Day	48% 5% 11% 24% 11% 1	1735
	11th to 20th	Day	56% 3 13% 19% 9%	1710
	21st to end	Day	60% 3 14% 16% 6% 1	1600
December	1st to 10th	Day	67% 3 12% 15% 3	1520
	11th to 20th	Day	63% 3 14% 16% 4	1683
	21st to end	Day	78% 2 9% 7% 3	2700
January	1st to 10th	Night	67% 3 10% 14% 6% 1	4428
	11th to 20th	Night	76% 2 7% 11% 4	4440
	21st to end	Night	73% 2 9% 13% 3	4685
February	1st to 10th	Night	65% 4 8% 16% 7% 1	2470
	11th to 20th	Night	59% 4 8% 19% 9% 1	2268
	21st to end	Night	59% 3 11% 18% 9% 1	1884
March	1st to 10th	Night	51% 2 12% 27% 7% 1	3680
	11th to 20th	Night	43% 3 14% 21% 17% 1	3480
	21st to end	Night	53% 2 10% 23% 10% 1	3817
April	1st to 10th	Night	50% 3 9% 22% 14% 2	1962
	11th to 20th	Night	48% 3 10% 19% 17% 2	1725
	21st to end	Night	47% 4 9% 21% 16% 3	1710
May	1st to 10th	Night	46% 3 11% 23% 14% 4	2840
	11th to 20th	Night	43% 2 8% 30% 13% 3	2813
	21st to end	Night	37% 3 10% 23% 20% 6%	2994
June	1st to 10th	Night	36% 4 10% 28% 20% 2	1425
	11th to 20th	Night	37% 4 13% 24% 21% 2	1330
	21st to end	Night	35% 4 13% 29% 18% 2	1455
July	1st to 10th	Night	34% 5% 12% 27% 16% 6%	2490
	11th to 20th	Night	29% 4 13% 32% 21% 1	2482
	21st to end	Night	32% 7% 18% 20% 21% 2	2833
August	1st to 10th	Night	35% 5% 13% 30% 16% 1	2814
	11th to 20th	Night	36% 5% 12% 33% 12% 2	2812
	21st to end	Night	34% 6% 12% 32% 15% 1	3180
September	1st to 10th	Night	35% 6% 11% 29% 17% 2	1995
	11th to 20th	Night	31% 3 12% 32% 20% 2	2090
	21st to end	Night	42% 4 11% 29% 14% 1	2090
October	1st to 10th	Night	27% 3 10% 33% 25% 1	3562
	11th to 20th	Night	46% 3 10% 24% 16% 1	3779
	21st to end	Night	44% 3 11% 31% 12% 1	4426
November	1st to 10th	Night	44% 4 11% 26% 14% 1	2504
	11th to 20th	Night	55% 4 13% 20% 8% 1	2470
	21st to end	Night	58% 3 15% 18% 6%	2576
December	1st to 10th	Night	68% 3 10% 14% 5%	2660
	11th to 20th	Night	64% 3 12% 14% 6% 1	3510
	21st to end	Night	76% 3 11% 7% 3	4948

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	25% 15% 38% 15% 6% 1	270
	11th to 20th	Day	23% 18% 41% 14% 3 1	270
	21st to end	Day	30% 15% 31% 18% 5% 1	297
February	1st to 10th	Day	27% 20% 36% 14% 2 1	270
	11th to 20th	Day	24% 20% 37% 18% 1	270
	21st to end	Day	30% 26% 35% 7% 3	225
March	1st to 10th	Day	27% 20% 36% 12% 3 1	296
	11th to 20th	Day	24% 13% 34% 20% 8%	460
	21st to end	Day	29% 14% 31% 19% 7% 1	506
April	1st to 10th	Day	24% 15% 34% 19% 8% 1	460
	11th to 20th	Day	30% 17% 29% 13% 5% 5%	452
	21st to end	Day	26% 13% 27% 22% 11% 2	460
May	1st to 10th	Day	24% 14% 29% 20% 10% 2	463
	11th to 20th	Day	22% 9% 29% 23% 12% 6%	487
	21st to end	Day	16% 7% 24% 27% 19% 7%	581
June	1st to 10th	Day	12% 12% 28% 28% 15% 4	680
	11th to 20th	Day	16% 9% 30% 25% 15% 5%	680
	21st to end	Day	14% 10% 28% 29% 16% 4	680
July	1st to 10th	Day	10% 7% 24% 27% 23% 10%	671
	11th to 20th	Day	12% 7% 28% 26% 18% 8%	668
	21st to end	Day	11% 5% 24% 31% 21% 8%	630
August	1st to 10th	Day	11% 5% 22% 24% 23% 15%	486
	11th to 20th	Day	14% 4 20% 28% 24% 10%	479
	21st to end	Day	14% 4 22% 26% 22% 11%	539
September	1st to 10th	Day	13% 9% 23% 25% 21% 10%	490
	11th to 20th	Day	12% 5% 20% 22% 28% 13%	490
	21st to end	Day	20% 11% 21% 23% 18% 8%	490
October	1st to 10th	Day	18% 11% 29% 20% 18% 5%	490
	11th to 20th	Day	23% 17% 27% 24% 8% 1	490
	21st to end	Day	32% 15% 34% 14% 5%	355
November	1st to 10th	Day	19% 19% 37% 17% 6% 2	291
	11th to 20th	Day	23% 20% 33% 16% 6% 1	270
	21st to end	Day	29% 17% 36% 14% 3	218
December	1st to 10th	Day	26% 21% 31% 16% 6% 1	180
	11th to 20th	Day	28% 24% 35% 8% 3 1	180
	21st to end	Day	32% 22% 32% 13% 1	276
January	1st to 10th	Night	23% 15% 33% 22% 5% 1	950
	11th to 20th	Night	27% 15% 30% 23% 4 1	950
	21st to end	Night	22% 12% 34% 27% 6%	924
February	1st to 10th	Night	25% 12% 37% 24% 3	760
	11th to 20th	Night	22% 15% 34% 23% 6%	743
	21st to end	Night	26% 16% 33% 22% 2	628
March	1st to 10th	Night	22% 14% 33% 24% 7%	760
	11th to 20th	Night	19% 14% 34% 27% 6% 1	760
	21st to end	Night	24% 11% 30% 26% 7% 1	836
April	1st to 10th	Night	24% 12% 35% 23% 5%	632
	11th to 20th	Night	23% 10% 36% 22% 8% 1	563
	21st to end	Night	21% 10% 32% 31% 6%	570
May	1st to 10th	Night	20% 6% 32% 32% 8% 1	570
	11th to 20th	Night	22% 4 31% 32% 10%	561
	21st to end	Night	14% 4 27% 38% 16% 2	617
June	1st to 10th	Night	15% 5% 24% 43% 12%	475
	11th to 20th	Night	13% 4 29% 43% 11%	380
	21st to end	Night	11% 5% 24% 43% 16% 1	505
July	1st to 10th	Night	9% 2 18% 42% 27% 2	555
	11th to 20th	Night	11% 4 22% 40% 20% 2	552
	21st to end	Night	8% 2 19% 47% 22% 1	624
August	1st to 10th	Night	9% 3 17% 42% 28% 2	567
	11th to 20th	Night	9% 4 16% 38% 28% 4	564
	21st to end	Night	13% 3 19% 36% 26% 3	627
September	1st to 10th	Night	12% 5% 20% 35% 23% 4	665
	11th to 20th	Night	14% 4 18% 33% 27% 4	760
	21st to end	Night	17% 6% 21% 31% 19% 5%	760
October	1st to 10th	Night	20% 7% 24% 32% 17% 1	760
	11th to 20th	Night	27% 11% 25% 27% 8% 1	760
	21st to end	Night	27% 10% 33% 25% 5%	836
November	1st to 10th	Night	21% 13% 29% 26% 9% 1	771
	11th to 20th	Night	22% 17% 32% 22% 6% 1	760
	21st to end	Night	27% 12% 36% 20% 5%	760
December	1st to 10th	Night	26% 14% 34% 19% 5% 1	760
	11th to 20th	Night	23% 15% 36% 21% 4	935
	21st to end	Night	33% 13% 35% 18% 1	1045

Page generated at 2024-11-05 08:15:48. Version ac07

Copyright © 2024 Attilla Danko.