Lawshe Memorial Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lawshe Memorial Observatory clear sky chart from 2005-11-06 to 2024-11-05.

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% 11% 4 9% 5% 4 4 3 5% 6% 33%	101253
	Night	15% 13% 5% 11% 6% 4 4 3 4 5% 29%	97892
Transparency	Day	51% 6% 11% 21% 11% 1	104763
	Night	57% 6% 11% 17% 9% 1	102470
Seeing	Day	20% 15% 29% 23% 10% 3	15643
	Night	22% 13% 28% 27% 10% 1	25210

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	12% 23% 13% 23% 7% 5% 4 2 2 3 6%	2527
	11th to 20th	Day	13% 18% 8% 18% 17% 7% 4 3 3 3 6%	2530
	21st to end	Day	16% 24% 10% 14% 8% 5% 5% 3 4 3 9%	2783
February	1st to 10th	Day	8% 18% 7% 14% 13% 7% 5% 3 4 5% 15%	1636
	11th to 20th	Day	12% 15% 7% 15% 8% 6% 5% 3 4 5% 21%	1805
	21st to end	Day	12% 16% 6% 13% 6% 6% 4 4 5% 6% 23%	1570
March	1st to 10th	Day	13% 13% 4 8% 6% 4 4 3 6% 6% 35%	3118
	11th to 20th	Day	8% 14% 6% 13% 6% 5% 4 4 4 6% 30%	3416
	21st to end	Day	15% 12% 7% 14% 6% 5% 4 3 4 6% 24%	3908
April	1st to 10th	Day	19% 15% 4 7% 5% 4 5% 3 4 7% 28%	2280
	11th to 20th	Day	21% 11% 4 6% 4 3 4 3 5% 5% 34%	2380
	21st to end	Day	15% 12% 4 8% 5% 4 4 4 5% 6% 33%	2470
May	1st to 10th	Day	16% 8% 2 6% 4 3 4 3 5% 6% 42%	4108
	11th to 20th	Day	11% 7% 2 6% 5% 4 4 3 5% 6% 47%	4221
	21st to end	Day	13% 7% 2 5% 4 4 4 3 6% 8% 44%	4895
June	1st to 10th	Day	14% 6% 2 6% 4 4 4 4 6% 7% 42%	2850
	11th to 20th	Day	13% 5% 2 6% 4 5% 5% 4 6% 8% 41%	2850
	21st to end	Day	17% 6% 3 5% 4 3 4 4 5% 7% 41%	2850
July	1st to 10th	Day	19% 7% 2 5% 4 3 3 3 5% 8% 41%	4481
	11th to 20th	Day	11% 5% 1 4 3 3 4 4 6% 8% 51%	4440
	21st to end	Day	10% 5% 2 5% 4 3 4 3 6% 9% 49%	4814
August	1st to 10th	Day	8% 6% 3 6% 5% 5% 5% 5% 7% 8% 42%	4234
	11th to 20th	Day	13% 6% 2 6% 3 4 4 3 5% 7% 47%	4044
	21st to end	Day	15% 6% 2 6% 4 4 4 3 4 7% 45%	4415
September	1st to 10th	Day	16% 6% 2 5% 4 3 4 3 5% 9% 43%	2237
	11th to 20th	Day	14% 6% 1 6% 4 3 4 3 5% 8% 45%	2090
	21st to end	Day	18% 6% 2 7% 4 4 4 3 6% 9% 36%	2090
October	1st to 10th	Day	19% 10% 2 7% 4 4 3 3 4 7% 34%	2077
	11th to 20th	Day	24% 18% 5% 8% 5% 4 4 3 4 5% 20%	1805
	21st to end	Day	24% 18% 3 9% 6% 5% 5% 3 5% 5% 17%	1881
November	1st to 10th	Day	19% 20% 4 7% 4 4 4 3 5% 6% 23%	1708
	11th to 20th	Day	13% 25% 7% 13% 6% 6% 3 3 5% 5% 15%	1710
	21st to end	Day	19% 24% 10% 13% 6% 4 3 3 3 4 11%	1498
December	1st to 10th	Day	13% 27% 12% 16% 6% 3 3 3 3 3 10%	1330
	11th to 20th	Day	16% 23% 8% 17% 9% 5% 3 3 3 3 9%	1671
	21st to end	Day	21% 24% 8% 17% 7% 5% 3 1 3 3 8%	2531
January	1st to 10th	Night	14% 21% 8% 23% 7% 4 3 2 3 4 11%	4428
	11th to 20th	Night	12% 16% 8% 21% 15% 7% 4 3 2 4 9%	4440
	21st to end	Night	15% 22% 9% 17% 8% 6% 4 3 4 4 8%	4884
February	1st to 10th	Night	10% 18% 7% 16% 10% 7% 4 3 4 4 16%	2542
	11th to 20th	Night	11% 14% 7% 13% 9% 6% 5% 3 4 5% 22%	2259
	21st to end	Night	15% 17% 5% 11% 7% 5% 4 3 5% 6% 22%	1884
March	1st to 10th	Night	16% 11% 3 6% 4 3 3 3 3 6% 42%	3722
	11th to 20th	Night	9% 14% 5% 9% 6% 4 4 3 5% 6% 35%	3543
	21st to end	Night	15% 11% 6% 10% 5% 4 4 4 5% 6% 29%	3740
April	1st to 10th	Night	20% 11% 3 8% 5% 5% 4 4 6% 6% 28%	1900
	11th to 20th	Night	19% 10% 4 6% 4 4 5% 3 5% 5% 34%	1748
	21st to end	Night	16% 11% 3 8% 5% 3 5% 4 5% 6% 35%	1710
May	1st to 10th	Night	16% 8% 3 7% 5% 5% 5% 3 5% 4 39%	2833
	11th to 20th	Night	12% 8% 3 8% 5% 4 4 4 6% 6% 41%	2674
	21st to end	Night	18% 7% 2 5% 4 4 3 3 5% 7% 41%	2690
June	1st to 10th	Night	15% 6% 3 6% 5% 5% 4 4 5% 7% 39%	1330
	11th to 20th	Night	11% 6% 3 6% 5% 4 5% 4 7% 9% 41%	1330
	21st to end	Night	14% 6% 2 6% 5% 3 4 4 5% 6% 44%	1330
July	1st to 10th	Night	15% 7% 3 6% 4 4 4 3 6% 8% 41%	2484
	11th to 20th	Night	9% 5% 2 6% 3 4 4 3 6% 6% 51%	2530
	21st to end	Night	9% 5% 2 5% 4 4 4 4 6% 8% 49%	2750
August	1st to 10th	Night	13% 6% 3 7% 4 4 5% 4 5% 7% 42%	2697
	11th to 20th	Night	14% 5% 2 5% 3 3 3 3 4 7% 49%	2785
	21st to end	Night	12% 5% 2 5% 4 4 4 4 4 6% 50%	3238
September	1st to 10th	Night	13% 6% 2 6% 4 3 4 4 5% 6% 47%	1924
	11th to 20th	Night	14% 6% 2 6% 5% 4 3 3 5% 7% 45%	2090
	21st to end	Night	19% 8% 2 5% 4 5% 4 3 5% 7% 39%	2090
October	1st to 10th	Night	18% 9% 3 7% 4 3 4 3 4 6% 38%	2102
	11th to 20th	Night	23% 15% 3 9% 4 4 4 3 4 6% 24%	2373
	21st to end	Night	26% 16% 3 8% 5% 4 4 3 4 5% 21%	2717
November	1st to 10th	Night	18% 17% 4 9% 5% 4 3 3 4 6% 26%	2470
	11th to 20th	Night	16% 23% 6% 12% 7% 5% 4 3 5% 4 16%	2470
	21st to end	Night	18% 23% 9% 14% 5% 3 4 3 4 4 13%	2678
December	1st to 10th	Night	13% 26% 10% 19% 7% 4 3 2 2 3 10%	2850
	11th to 20th	Night	15% 21% 8% 20% 7% 4 4 2 3 4 12%	3526
	21st to end	Night	22% 22% 8% 14% 6% 5% 3 3 4 4 8%	5131

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	86% 5% 4 4 1	2528
	11th to 20th	Day	86% 4 4 4 1	2530
	21st to end	Day	79% 8% 7% 4 2	2783
February	1st to 10th	Day	72% 6% 9% 10% 3	1636
	11th to 20th	Day	67% 7% 9% 10% 7%	1815
	21st to end	Day	62% 7% 9% 17% 5%	1570
March	1st to 10th	Day	49% 6% 13% 20% 10% 1	3120
	11th to 20th	Day	55% 5% 13% 19% 6% 2	3416
	21st to end	Day	61% 7% 9% 13% 8% 1	3908
April	1st to 10th	Day	57% 6% 9% 18% 10% 1	2280
	11th to 20th	Day	51% 5% 10% 19% 13% 1	2380
	21st to end	Day	51% 6% 11% 15% 15% 3	2470
May	1st to 10th	Day	41% 6% 11% 22% 19% 2	4120
	11th to 20th	Day	37% 6% 10% 29% 16% 2	4225
	21st to end	Day	36% 7% 13% 21% 20% 2	4895
June	1st to 10th	Day	39% 7% 11% 27% 14% 2	2850
	11th to 20th	Day	39% 8% 12% 23% 17% 1	2850
	21st to end	Day	41% 7% 13% 24% 13% 2	2850
July	1st to 10th	Day	43% 5% 15% 23% 12% 1	4412
	11th to 20th	Day	30% 6% 13% 37% 13% 1	4365
	21st to end	Day	33% 6% 12% 32% 17% 1	4662
August	1st to 10th	Day	38% 7% 13% 30% 13%	4219
	11th to 20th	Day	38% 6% 12% 32% 11% 1	4083
	21st to end	Day	41% 6% 14% 30% 9% 1	4414
September	1st to 10th	Day	40% 6% 12% 25% 15% 1	2237
	11th to 20th	Day	38% 8% 14% 29% 12% 1	2090
	21st to end	Day	45% 7% 14% 25% 10%	2090
October	1st to 10th	Day	38% 4 10% 32% 16%	3454
	11th to 20th	Day	57% 5% 9% 20% 9%	2982
	21st to end	Day	65% 6% 12% 15% 3	3081
November	1st to 10th	Day	62% 6% 10% 17% 5%	1708
	11th to 20th	Day	73% 6% 9% 8% 4	1710
	21st to end	Day	78% 5% 9% 6% 1	1498
December	1st to 10th	Day	82% 5% 6% 5% 2	1330
	11th to 20th	Day	80% 8% 6% 5% 1	1671
	21st to end	Day	83% 6% 6% 2 3	2531
January	1st to 10th	Night	78% 6% 8% 7% 1	4428
	11th to 20th	Night	81% 7% 6% 5% 1	4440
	21st to end	Night	80% 6% 7% 4 2	4884
February	1st to 10th	Night	73% 6% 7% 10% 4 1	2542
	11th to 20th	Night	66% 6% 10% 15% 3	2260
	21st to end	Night	63% 7% 11% 13% 6%	1884
March	1st to 10th	Night	46% 5% 16% 23% 10%	3733
	11th to 20th	Night	50% 6% 12% 23% 8% 1	3544
	21st to end	Night	54% 8% 11% 18% 8% 1	3740
April	1st to 10th	Night	55% 6% 10% 17% 11% 1	1900
	11th to 20th	Night	51% 4 9% 22% 12% 2	1748
	21st to end	Night	50% 6% 9% 18% 15% 3	1710
May	1st to 10th	Night	45% 7% 11% 20% 15% 2	2840
	11th to 20th	Night	42% 6% 9% 26% 15% 1	2675
	21st to end	Night	42% 8% 13% 19% 15% 4	2691
June	1st to 10th	Night	42% 6% 12% 25% 15% 1	1330
	11th to 20th	Night	38% 7% 12% 25% 14% 3	1330
	21st to end	Night	39% 7% 12% 25% 15% 2	1330
July	1st to 10th	Night	41% 5% 15% 23% 14% 3	2444
	11th to 20th	Night	32% 5% 13% 30% 17% 1	2482
	21st to end	Night	34% 6% 14% 25% 20% 1	2662
August	1st to 10th	Night	41% 6% 14% 26% 12% 1	2688
	11th to 20th	Night	34% 6% 15% 31% 13% 1	2812
	21st to end	Night	35% 6% 14% 29% 15% 1	3238
September	1st to 10th	Night	37% 7% 13% 25% 16% 1	1924
	11th to 20th	Night	38% 7% 16% 27% 11% 1	2090
	21st to end	Night	44% 8% 15% 23% 9%	2090
October	1st to 10th	Night	42% 6% 10% 30% 12% 1	3505
	11th to 20th	Night	51% 6% 11% 19% 12%	3935
	21st to end	Night	60% 6% 13% 17% 4	4467
November	1st to 10th	Night	60% 6% 11% 17% 5% 1	2470
	11th to 20th	Night	70% 5% 10% 9% 5%	2470
	21st to end	Night	75% 6% 11% 6% 1	2678
December	1st to 10th	Night	81% 5% 7% 6% 1	2850
	11th to 20th	Night	79% 6% 9% 4 2	3525
	21st to end	Night	80% 9% 6% 3 1	5131

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	24% 18% 37% 17% 4	270
	11th to 20th	Day	24% 19% 38% 15% 3 1	270
	21st to end	Day	28% 14% 34% 19% 5%	297
February	1st to 10th	Day	20% 31% 32% 10% 6%	270
	11th to 20th	Day	19% 31% 33% 14% 2	270
	21st to end	Day	27% 28% 37% 6% 2	225
March	1st to 10th	Day	21% 27% 34% 14% 4	270
	11th to 20th	Day	21% 19% 32% 21% 6% 1	422
	21st to end	Day	27% 17% 28% 21% 6% 1	506
April	1st to 10th	Day	26% 21% 30% 16% 6% 1	460
	11th to 20th	Day	31% 19% 24% 15% 9% 1	452
	21st to end	Day	22% 16% 32% 20% 9% 2	460
May	1st to 10th	Day	25% 19% 26% 18% 10% 2	463
	11th to 20th	Day	16% 14% 36% 23% 7% 4	562
	21st to end	Day	16% 12% 28% 28% 14% 2	734
June	1st to 10th	Day	16% 14% 31% 28% 9% 2	680
	11th to 20th	Day	16% 11% 32% 29% 10% 3	680
	21st to end	Day	19% 9% 29% 30% 11% 2	680
July	1st to 10th	Day	11% 9% 30% 31% 16% 4	671
	11th to 20th	Day	13% 9% 28% 31% 14% 5%	668
	21st to end	Day	12% 6% 29% 33% 15% 4	739
August	1st to 10th	Day	10% 8% 23% 33% 21% 5%	565
	11th to 20th	Day	14% 6% 21% 31% 19% 8%	479
	21st to end	Day	21% 9% 23% 26% 18% 4	539
September	1st to 10th	Day	19% 10% 26% 23% 17% 5%	490
	11th to 20th	Day	13% 11% 21% 29% 19% 7%	490
	21st to end	Day	20% 10% 23% 28% 16% 3	490
October	1st to 10th	Day	24% 17% 25% 20% 13% 1	490
	11th to 20th	Day	32% 19% 27% 19% 2 1	395
	21st to end	Day	32% 19% 33% 12% 3 1	330
November	1st to 10th	Day	35% 16% 31% 13% 5%	282
	11th to 20th	Day	25% 24% 31% 16% 4	270
	21st to end	Day	28% 31% 28% 11% 2	187
December	1st to 10th	Day	32% 23% 29% 10% 5% 1	180
	11th to 20th	Day	25% 28% 34% 9% 2 1	180
	21st to end	Day	33% 28% 28% 7% 3 1	227
January	1st to 10th	Night	21% 19% 32% 21% 5% 1	950
	11th to 20th	Night	24% 18% 31% 21% 6%	950
	21st to end	Night	21% 15% 33% 26% 5% 1	1045
February	1st to 10th	Night	18% 19% 34% 24% 5%	832
	11th to 20th	Night	20% 19% 30% 24% 6%	743
	21st to end	Night	24% 16% 33% 23% 4	628
March	1st to 10th	Night	18% 13% 33% 26% 8% 1	760
	11th to 20th	Night	19% 14% 36% 23% 7% 1	760
	21st to end	Night	21% 11% 27% 31% 8% 1	797
April	1st to 10th	Night	26% 11% 31% 26% 5% 1	570
	11th to 20th	Night	25% 11% 28% 27% 8% 1	563
	21st to end	Night	21% 10% 30% 29% 9% 1	570
May	1st to 10th	Night	15% 9% 29% 37% 9% 1	570
	11th to 20th	Night	17% 7% 32% 34% 9% 1	561
	21st to end	Night	15% 7% 22% 37% 17% 1	583
June	1st to 10th	Night	17% 7% 26% 37% 12% 1	380
	11th to 20th	Night	11% 5% 24% 42% 17%	380
	21st to end	Night	15% 5% 26% 37% 16% 1	380
July	1st to 10th	Night	12% 3 19% 46% 17% 2	522
	11th to 20th	Night	10% 6% 20% 35% 25% 3	552
	21st to end	Night	9% 4 23% 38% 23% 2	624
August	1st to 10th	Night	13% 3 20% 38% 24% 1	567
	11th to 20th	Night	13% 5% 14% 37% 28% 3	564
	21st to end	Night	19% 4 20% 36% 19% 2	627
September	1st to 10th	Night	15% 6% 22% 33% 20% 3	594
	11th to 20th	Night	18% 6% 21% 32% 20% 3	760
	21st to end	Night	22% 6% 22% 32% 14% 4	760
October	1st to 10th	Night	23% 12% 24% 28% 12% 1	760
	11th to 20th	Night	32% 13% 27% 22% 6% 1	760
	21st to end	Night	37% 14% 25% 19% 5% 1	836
November	1st to 10th	Night	29% 16% 28% 21% 6% 1	760
	11th to 20th	Night	29% 19% 30% 18% 5%	760
	21st to end	Night	31% 19% 32% 16% 3	797
December	1st to 10th	Night	26% 22% 32% 16% 4	950
	11th to 20th	Night	24% 24% 33% 15% 3 1	950
	21st to end	Night	31% 16% 32% 18% 3	1045

Page generated at 2024-11-03 02:11:14. Version ac07

Copyright © 2024 Attilla Danko.