Lanphier Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lanphier Observatory clear sky chart from 2005-11-06 to 2024-11-01.

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	12% 8% 3 7% 5% 4 4 4 6% 8% 39%	101257
	Night	13% 9% 3 7% 4 4 4 3 5% 7% 41%	97757
Transparency	Day	42% 6% 12% 23% 14% 2	101045
	Night	43% 5% 11% 24% 15% 2	97640
Seeing	Day	15% 10% 27% 26% 16% 5%	15696
	Night	17% 9% 30% 30% 13% 1	25503

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% 12% 6% 15% 6% 5% 5% 3 5% 5% 26%	2527
	11th to 20th	Day	13% 10% 5% 12% 8% 9% 8% 5% 6% 5% 21%	2571
	21st to end	Day	19% 19% 9% 9% 4 3 3 2 3 5% 23%	3135
February	1st to 10th	Day	14% 13% 5% 9% 6% 5% 3 3 4 6% 30%	1710
	11th to 20th	Day	13% 10% 4 8% 6% 5% 5% 3 6% 7% 33%	1831
	21st to end	Day	16% 12% 4 9% 5% 4 3 3 4 6% 33%	1570
March	1st to 10th	Day	18% 14% 4 7% 4 4 3 3 3 5% 37%	3120
	11th to 20th	Day	9% 9% 3 6% 4 4 3 3 6% 7% 46%	3443
	21st to end	Day	17% 11% 4 9% 5% 5% 5% 4 5% 7% 29%	4065
April	1st to 10th	Day	13% 8% 3 7% 5% 5% 4 4 6% 7% 37%	2280
	11th to 20th	Day	15% 9% 3 7% 4 4 5% 4 5% 6% 39%	2254
	21st to end	Day	19% 7% 2 6% 6% 5% 5% 3 5% 7% 35%	2280
May	1st to 10th	Day	13% 9% 3 7% 5% 5% 5% 4 7% 10% 31%	3988
	11th to 20th	Day	16% 8% 3 7% 5% 4 4 4 5% 7% 37%	4381
	21st to end	Day	9% 6% 2 6% 5% 4 5% 4 6% 8% 45%	4824
June	1st to 10th	Day	8% 4 2 5% 4 4 5% 5% 6% 9% 47%	2660
	11th to 20th	Day	9% 4 2 5% 4 4 4 4 6% 7% 50%	2660
	21st to end	Day	6% 6% 2 7% 6% 5% 5% 5% 7% 8% 43%	2660
July	1st to 10th	Day	13% 6% 2 6% 5% 4 5% 5% 7% 9% 40%	4440
	11th to 20th	Day	5% 5% 2 6% 4 4 5% 5% 7% 11% 46%	4440
	21st to end	Day	9% 5% 2 6% 5% 5% 6% 4 8% 11% 39%	4762
August	1st to 10th	Day	6% 5% 2 5% 4 4 5% 4 7% 10% 49%	4086
	11th to 20th	Day	10% 6% 2 6% 4 5% 5% 4 7% 9% 42%	3729
	21st to end	Day	5% 5% 2 5% 4 4 6% 4 7% 10% 48%	4180
September	1st to 10th	Day	12% 5% 2 5% 4 4 4 3 5% 7% 50%	2280
	11th to 20th	Day	8% 6% 2 6% 3 4 4 3 5% 6% 51%	2233
	21st to end	Day	8% 6% 2 6% 3 3 4 4 6% 7% 50%	2090
October	1st to 10th	Day	11% 4 2 5% 4 3 4 3 5% 7% 53%	1929
	11th to 20th	Day	15% 7% 2 6% 4 4 3 3 4 6% 47%	1900
	21st to end	Day	18% 9% 3 7% 4 4 2 3 5% 6% 41%	2006
November	1st to 10th	Day	10% 7% 2 5% 4 4 4 3 4 7% 51%	1672
	11th to 20th	Day	15% 10% 3 7% 3 3 3 3 5% 6% 42%	1710
	21st to end	Day	16% 11% 4 7% 4 4 4 4 3 5% 38%	1620
December	1st to 10th	Day	14% 11% 5% 7% 5% 4 4 4 5% 6% 34%	1520
	11th to 20th	Day	14% 11% 4 8% 5% 3 4 4 5% 8% 33%	1918
	21st to end	Day	21% 17% 6% 14% 4 4 4 3 3 5% 19%	2783
January	1st to 10th	Night	13% 13% 6% 10% 5% 5% 4 3 5% 5% 32%	4428
	11th to 20th	Night	13% 17% 6% 10% 5% 5% 7% 4 4 4 24%	4394
	21st to end	Night	23% 16% 7% 11% 4 3 3 2 4 6% 22%	4532
February	1st to 10th	Night	16% 12% 5% 9% 5% 5% 4 3 5% 6% 32%	2470
	11th to 20th	Night	13% 9% 3 9% 6% 3 4 3 5% 6% 39%	2233
	21st to end	Night	15% 10% 3 8% 4 5% 4 3 4 5% 38%	1884
March	1st to 10th	Night	20% 13% 3 5% 3 3 3 2 3 5% 39%	3733
	11th to 20th	Night	12% 6% 2 5% 4 3 3 3 5% 6% 51%	3544
	21st to end	Night	19% 10% 4 8% 5% 4 4 3 4 6% 32%	3564
April	1st to 10th	Night	12% 8% 3 6% 4 5% 4 4 5% 7% 42%	1900
	11th to 20th	Night	14% 6% 3 5% 4 4 4 3 5% 7% 44%	1875
	21st to end	Night	20% 8% 3 6% 4 4 4 5% 3 5% 39%	1900
May	1st to 10th	Night	16% 9% 3 7% 4 4 5% 4 6% 8% 35%	2894
	11th to 20th	Night	16% 7% 2 6% 4 4 4 3 6% 8% 41%	2520
	21st to end	Night	9% 6% 2 6% 4 4 5% 4 6% 9% 45%	2743
June	1st to 10th	Night	8% 6% 2 5% 3 3 4 4 6% 9% 51%	1520
	11th to 20th	Night	7% 5% 2 5% 4 4 4 4 6% 8% 51%	1520
	21st to end	Night	7% 4 2 6% 4 5% 4 4 7% 9% 49%	1520
July	1st to 10th	Night	12% 5% 2 6% 4 4 5% 4 6% 9% 42%	2530
	11th to 20th	Night	4 3 1 4 3 4 4 4 7% 9% 57%	2530
	21st to end	Night	7% 5% 2 6% 4 5% 5% 4 8% 10% 44%	2798
August	1st to 10th	Night	6% 4 2 4 3 2 4 4 6% 10% 55%	2853
	11th to 20th	Night	7% 4 2 5% 4 4 5% 3 5% 8% 52%	3100
	21st to end	Night	5% 3 1 5% 3 4 4 4 7% 10% 53%	3476
September	1st to 10th	Night	10% 4 2 5% 3 3 3 3 5% 7% 55%	1900
	11th to 20th	Night	7% 5% 2 6% 3 3 3 3 5% 8% 54%	1928
	21st to end	Night	9% 5% 2 5% 4 4 4 3 5% 7% 53%	2090
October	1st to 10th	Night	9% 4 1 5% 4 3 4 3 5% 6% 55%	2247
	11th to 20th	Night	14% 6% 2 4 3 3 3 3 5% 7% 51%	2280
	21st to end	Night	18% 8% 2 6% 4 3 4 3 5% 5% 43%	2590
November	1st to 10th	Night	10% 6% 2 5% 4 3 3 3 5% 6% 55%	2413
	11th to 20th	Night	12% 7% 3 6% 4 3 3 3 4 6% 48%	2470
	21st to end	Night	17% 10% 3 6% 4 3 4 3 4 6% 41%	2555
December	1st to 10th	Night	16% 12% 3 7% 6% 4 4 3 5% 7% 33%	2660
	11th to 20th	Night	15% 9% 4 9% 4 4 4 3 4 5% 40%	3279
	21st to end	Night	21% 19% 6% 11% 6% 5% 4 3 4 4 19%	4884

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	59% 5% 8% 19% 8%	2528
	11th to 20th	Day	64% 4 13% 14% 5%	2571
	21st to end	Day	65% 4 10% 14% 7%	3135
February	1st to 10th	Day	56% 5% 11% 18% 9% 1	1710
	11th to 20th	Day	50% 5% 11% 21% 12% 1	1841
	21st to end	Day	53% 3 10% 21% 10% 2	1570
March	1st to 10th	Day	51% 4 9% 19% 15% 2	3120
	11th to 20th	Day	37% 5% 14% 25% 18% 1	3443
	21st to end	Day	54% 7% 15% 19% 4	4065
April	1st to 10th	Day	45% 6% 12% 23% 14% 1	2280
	11th to 20th	Day	45% 5% 9% 24% 14% 2	2254
	21st to end	Day	48% 6% 12% 20% 13% 2	2280
May	1st to 10th	Day	45% 8% 15% 22% 9%	4024
	11th to 20th	Day	45% 7% 11% 27% 9%	4385
	21st to end	Day	35% 8% 10% 22% 24% 2	4837
June	1st to 10th	Day	31% 9% 13% 27% 17% 3	2660
	11th to 20th	Day	32% 7% 11% 25% 23% 3	2660
	21st to end	Day	35% 9% 13% 22% 17% 3	2660
July	1st to 10th	Day	39% 8% 12% 26% 13% 2	4371
	11th to 20th	Day	30% 8% 15% 27% 19% 1	4365
	21st to end	Day	35% 10% 19% 23% 13% 1	4612
August	1st to 10th	Day	28% 8% 18% 34% 11% 1	4072
	11th to 20th	Day	37% 7% 13% 28% 14% 1	3765
	21st to end	Day	28% 8% 16% 29% 15% 4	4179
September	1st to 10th	Day	34% 6% 10% 24% 20% 6%	2280
	11th to 20th	Day	33% 5% 9% 25% 23% 5%	2233
	21st to end	Day	32% 6% 9% 28% 22% 2	2090
October	1st to 10th	Day	32% 5% 11% 23% 26% 3	1929
	11th to 20th	Day	40% 4 8% 23% 22% 2	1900
	21st to end	Day	46% 4 9% 24% 15% 3	2006
November	1st to 10th	Day	35% 4 14% 25% 18% 4	1672
	11th to 20th	Day	42% 4 11% 25% 16% 3	1710
	21st to end	Day	49% 5% 10% 24% 11%	1620
December	1st to 10th	Day	50% 6% 13% 20% 10%	1520
	11th to 20th	Day	48% 6% 10% 26% 8% 2	1915
	21st to end	Day	68% 4 10% 12% 6% 1	2783
January	1st to 10th	Night	54% 5% 12% 21% 9%	4428
	11th to 20th	Night	64% 3 9% 16% 7%	4394
	21st to end	Night	65% 4 8% 16% 6% 1	4532
February	1st to 10th	Night	53% 4 11% 18% 11% 2	2470
	11th to 20th	Night	47% 3 11% 23% 15% 2	2234
	21st to end	Night	48% 4 11% 22% 13% 3	1884
March	1st to 10th	Night	48% 4 8% 25% 13% 1	3733
	11th to 20th	Night	35% 5% 9% 27% 20% 4	3544
	21st to end	Night	52% 6% 11% 23% 7% 1	3564
April	1st to 10th	Night	40% 6% 12% 24% 15% 4	1900
	11th to 20th	Night	39% 4 11% 25% 18% 3	1875
	21st to end	Night	47% 5% 10% 20% 16% 3	1900
May	1st to 10th	Night	45% 8% 15% 21% 10% 1	2922
	11th to 20th	Night	41% 7% 14% 27% 11% 1	2521
	21st to end	Night	33% 8% 13% 20% 22% 4	2751
June	1st to 10th	Night	27% 8% 14% 28% 18% 5%	1520
	11th to 20th	Night	30% 7% 11% 23% 24% 5%	1520
	21st to end	Night	31% 7% 15% 24% 19% 5%	1520
July	1st to 10th	Night	39% 6% 11% 29% 13% 2	2490
	11th to 20th	Night	20% 7% 14% 35% 22% 2	2482
	21st to end	Night	31% 9% 19% 22% 17% 2	2709
August	1st to 10th	Night	23% 7% 18% 33% 17% 1	2843
	11th to 20th	Night	29% 7% 13% 32% 19% 1	3130
	21st to end	Night	24% 7% 17% 32% 15% 4	3476
September	1st to 10th	Night	29% 5% 10% 25% 22% 8%	1900
	11th to 20th	Night	29% 5% 8% 25% 27% 5%	1928
	21st to end	Night	32% 5% 9% 25% 25% 5%	2090
October	1st to 10th	Night	30% 5% 10% 24% 27% 5%	2247
	11th to 20th	Night	34% 5% 8% 26% 23% 4	2280
	21st to end	Night	44% 4 9% 21% 20% 3	2590
November	1st to 10th	Night	32% 5% 11% 26% 20% 5%	2413
	11th to 20th	Night	37% 4 10% 27% 20% 2	2470
	21st to end	Night	46% 3 10% 24% 16% 1	2555
December	1st to 10th	Night	51% 4 12% 22% 10% 1	2660
	11th to 20th	Night	48% 4 11% 24% 11% 1	3281
	21st to end	Night	69% 5% 7% 12% 6% 1	4884

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% 19% 33% 17% 7%	270
	11th to 20th	Day	28% 17% 37% 16% 2	270
	21st to end	Day	20% 17% 37% 22% 5%	297
February	1st to 10th	Day	27% 16% 38% 15% 4	270
	11th to 20th	Day	24% 17% 33% 21% 4	270
	21st to end	Day	24% 15% 47% 14% 1	225
March	1st to 10th	Day	23% 19% 40% 16% 3	270
	11th to 20th	Day	27% 16% 36% 17% 4	270
	21st to end	Day	30% 16% 31% 18% 5%	445
April	1st to 10th	Day	20% 17% 33% 25% 5% 1	460
	11th to 20th	Day	20% 17% 32% 20% 10% 1	452
	21st to end	Day	22% 14% 35% 20% 7% 1	460
May	1st to 10th	Day	17% 13% 34% 25% 8% 2	463
	11th to 20th	Day	18% 11% 27% 27% 14% 3	657
	21st to end	Day	12% 8% 33% 26% 14% 7%	734
June	1st to 10th	Day	9% 7% 23% 31% 24% 7%	680
	11th to 20th	Day	10% 5% 22% 36% 21% 5%	680
	21st to end	Day	8% 6% 31% 33% 18% 4	680
July	1st to 10th	Day	11% 3 15% 30% 27% 14%	671
	11th to 20th	Day	6% 4 21% 34% 25% 10%	668
	21st to end	Day	10% 2 18% 32% 31% 8%	739
August	1st to 10th	Day	8% 3 16% 38% 26% 9%	671
	11th to 20th	Day	8% 5% 19% 28% 26% 14%	479
	21st to end	Day	7% 2 16% 31% 33% 10%	539
September	1st to 10th	Day	13% 4 18% 28% 28% 9%	490
	11th to 20th	Day	9% 2 14% 32% 30% 12%	490
	21st to end	Day	10% 11% 22% 26% 22% 9%	490
October	1st to 10th	Day	12% 9% 26% 32% 16% 5%	329
	11th to 20th	Day	16% 18% 32% 24% 8% 1	300
	21st to end	Day	30% 13% 33% 18% 5%	330
November	1st to 10th	Day	11% 15% 36% 21% 11% 5%	270
	11th to 20th	Day	24% 16% 31% 18% 9% 2	270
	21st to end	Day	23% 13% 38% 20% 6%	270
December	1st to 10th	Day	15% 23% 35% 17% 6% 4	270
	11th to 20th	Day	20% 18% 38% 20% 4	270
	21st to end	Day	26% 20% 37% 14% 2	297
January	1st to 10th	Night	18% 14% 40% 23% 5%	950
	11th to 20th	Night	21% 16% 37% 21% 5%	950
	21st to end	Night	22% 14% 35% 27% 3	1045
February	1st to 10th	Night	23% 14% 36% 24% 3	950
	11th to 20th	Night	20% 14% 36% 27% 2	758
	21st to end	Night	22% 16% 36% 22% 3	628
March	1st to 10th	Night	22% 15% 37% 23% 4	760
	11th to 20th	Night	20% 11% 34% 29% 6%	608
	21st to end	Night	28% 10% 33% 23% 6%	627
April	1st to 10th	Night	18% 15% 37% 26% 4	570
	11th to 20th	Night	16% 13% 34% 27% 9%	563
	21st to end	Night	22% 9% 37% 25% 6% 1	570
May	1st to 10th	Night	19% 6% 38% 28% 8% 1	570
	11th to 20th	Night	18% 4 27% 37% 12% 1	561
	21st to end	Night	11% 5% 27% 33% 21% 3	617
June	1st to 10th	Night	9% 4 21% 46% 20%	570
	11th to 20th	Night	10% 3 23% 43% 19% 2	570
	21st to end	Night	8% 2 28% 41% 19% 1	570
July	1st to 10th	Night	11% 2 11% 36% 35% 5%	555
	11th to 20th	Night	5% 2 19% 40% 32% 3	552
	21st to end	Night	7% 14% 45% 31% 2	624
August	1st to 10th	Night	8% 2 12% 44% 30% 4	567
	11th to 20th	Night	8% 1 14% 39% 33% 6%	564
	21st to end	Night	5% 1 13% 39% 39% 2	627
September	1st to 10th	Night	12% 3 16% 37% 28% 4	570
	11th to 20th	Night	9% 1 17% 38% 31% 4	598
	21st to end	Night	10% 8% 23% 32% 23% 4	760
October	1st to 10th	Night	11% 4 30% 31% 22% 2	760
	11th to 20th	Night	16% 11% 31% 29% 12% 1	760
	21st to end	Night	22% 12% 34% 24% 7%	836
November	1st to 10th	Night	12% 10% 41% 27% 9%	743
	11th to 20th	Night	17% 14% 37% 26% 6% 1	760
	21st to end	Night	22% 14% 34% 25% 5%	845
December	1st to 10th	Night	21% 12% 38% 23% 5% 1	950
	11th to 20th	Night	23% 10% 35% 26% 6%	950
	21st to end	Night	25% 17% 32% 22% 3	1045

Page generated at 2024-10-29 10:20:48. Version ac07

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