Camp McGregor Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Camp McGregor Observatory clear sky chart from 2005-11-06 to 2024-01-14.

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% 9% 4 7% 6% 4 5% 5% 5% 7% 33%	74892
	Night	14% 10% 4 7% 6% 3 5% 5% 5% 7% 34%	74888
Transparency	Day	49% 7% 12% 19% 11% 1	74600
	Night	49% 7% 12% 19% 12% 1	74701
Seeing	Day	17% 12% 29% 23% 14% 6%	14531
	Night	18% 10% 30% 28% 12% 1	24491

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% 13% 6% 11% 9% 5% 5% 5% 6% 5% 18%	1517
	11th to 20th	Day	15% 15% 9% 13% 10% 4 5% 4 5% 5% 15%	1464
	21st to end	Day	14% 18% 9% 11% 9% 5% 5% 4 3 4 18%	1684
February	1st to 10th	Day	13% 14% 7% 11% 11% 4 5% 5% 5% 6% 19%	1634
	11th to 20th	Day	15% 10% 5% 12% 9% 5% 6% 5% 5% 5% 23%	1748
	21st to end	Day	17% 14% 8% 11% 6% 3 4 4 5% 6% 23%	1480
March	1st to 10th	Day	13% 11% 5% 8% 8% 4 4 7% 6% 7% 26%	1800
	11th to 20th	Day	14% 11% 4 8% 6% 3 4 4 4 8% 34%	1976
	21st to end	Day	18% 13% 6% 8% 6% 3 4 4 5% 6% 28%	2178
April	1st to 10th	Day	16% 12% 5% 8% 6% 3 5% 4 5% 6% 30%	2155
	11th to 20th	Day	16% 9% 4 7% 6% 3 5% 5% 5% 6% 35%	2227
	21st to end	Day	16% 10% 4 7% 6% 3 5% 4 5% 8% 33%	2340
May	1st to 10th	Day	17% 8% 3 6% 6% 3 6% 6% 5% 7% 33%	2340
	11th to 20th	Day	19% 8% 4 6% 7% 3 4 4 5% 7% 34%	2301
	21st to end	Day	12% 5% 2 6% 5% 3 6% 6% 7% 9% 39%	2583
June	1st to 10th	Day	10% 6% 3 5% 5% 4 6% 5% 7% 9% 41%	2520
	11th to 20th	Day	11% 6% 2 3 6% 3 6% 5% 7% 9% 42%	2520
	21st to end	Day	9% 6% 3 6% 6% 3 6% 6% 8% 10% 38%	2520
July	1st to 10th	Day	7% 4 2 5% 5% 4 6% 6% 7% 9% 45%	2520
	11th to 20th	Day	9% 4 3 6% 5% 4 5% 6% 6% 10% 44%	2520
	21st to end	Day	6% 5% 3 5% 6% 4 6% 7% 7% 10% 41%	2649
August	1st to 10th	Day	7% 4 2 6% 6% 3 6% 7% 7% 10% 41%	2327
	11th to 20th	Day	10% 5% 3 5% 7% 4 6% 7% 7% 8% 38%	2303
	21st to end	Day	10% 6% 3 5% 5% 3 5% 5% 6% 9% 44%	2471
September	1st to 10th	Day	12% 6% 3 5% 5% 4 6% 6% 5% 8% 40%	2075
	11th to 20th	Day	10% 4 2 6% 4 3 5% 6% 7% 10% 44%	1980
	21st to end	Day	12% 7% 3 5% 5% 3 5% 6% 6% 8% 40%	1980
October	1st to 10th	Day	12% 7% 3 5% 6% 3 4 5% 5% 7% 42%	1980
	11th to 20th	Day	16% 10% 3 6% 7% 4 5% 5% 5% 7% 32%	1800
	21st to end	Day	20% 11% 4 7% 6% 4 4 4 6% 7% 28%	1782
November	1st to 10th	Day	11% 8% 3 7% 5% 3 5% 5% 6% 6% 41%	1672
	11th to 20th	Day	14% 14% 4 8% 7% 3 5% 4 5% 6% 29%	1710
	21st to end	Day	19% 13% 6% 8% 6% 4 5% 4 4 6% 26%	1710
December	1st to 10th	Day	13% 15% 9% 11% 6% 4 5% 4 4 6% 22%	1710
	11th to 20th	Day	13% 15% 6% 12% 8% 4 5% 5% 6% 6% 19%	1933
	21st to end	Day	19% 20% 9% 13% 8% 4 4 4 3 5% 11%	2783
January	1st to 10th	Night	16% 13% 6% 10% 7% 5% 5% 4 5% 7% 22%	2648
	11th to 20th	Night	16% 15% 7% 11% 8% 4 5% 4 5% 5% 19%	2575
	21st to end	Night	13% 14% 8% 13% 9% 5% 5% 6% 5% 6% 18%	2669
February	1st to 10th	Night	16% 15% 6% 11% 8% 4 5% 5% 5% 5% 21%	2322
	11th to 20th	Night	13% 12% 5% 10% 8% 4 5% 4 5% 6% 27%	2098
	21st to end	Night	20% 9% 5% 10% 6% 3 5% 4 3 7% 28%	1776
March	1st to 10th	Night	15% 10% 4 7% 7% 3 4 4 5% 6% 34%	2160
	11th to 20th	Night	13% 10% 3 5% 4 3 6% 5% 6% 8% 38%	1981
	21st to end	Night	20% 9% 4 7% 6% 3 4 4 4 6% 33%	2178
April	1st to 10th	Night	14% 9% 4 6% 6% 3 5% 5% 5% 7% 36%	1821
	11th to 20th	Night	18% 8% 3 6% 5% 3 4 5% 5% 6% 37%	1681
	21st to end	Night	16% 9% 3 6% 6% 3 4 4 5% 7% 36%	1620
May	1st to 10th	Night	16% 10% 3 6% 8% 3 4 5% 6% 7% 31%	1620
	11th to 20th	Night	20% 7% 2 5% 5% 3 4 5% 5% 7% 38%	1592
	21st to end	Night	10% 6% 2 5% 4 3 5% 5% 5% 8% 45%	1689
June	1st to 10th	Night	10% 3 2 4 6% 2 5% 5% 6% 10% 47%	1440
	11th to 20th	Night	10% 5% 3 6% 6% 4 4 4 6% 9% 43%	1440
	21st to end	Night	8% 5% 2 5% 4 3 4 6% 6% 10% 47%	1440
July	1st to 10th	Night	7% 3 2 5% 4 4 4 5% 6% 8% 53%	1440
	11th to 20th	Night	9% 4 2 4 4 3 4 4 6% 8% 53%	1440
	21st to end	Night	5% 3 2 4 4 4 5% 6% 6% 10% 49%	1668
August	1st to 10th	Night	7% 5% 2 4 4 3 4 6% 6% 9% 51%	1611
	11th to 20th	Night	7% 4 2 5% 4 4 5% 5% 6% 9% 49%	1598
	21st to end	Night	9% 5% 2 4 4 3 5% 5% 5% 7% 51%	1881
September	1st to 10th	Night	9% 7% 3 5% 4 3 5% 5% 5% 6% 49%	1867
	11th to 20th	Night	10% 5% 2 3 4 3 4 4 5% 7% 53%	1980
	21st to end	Night	12% 6% 2 6% 5% 3 4 4 5% 7% 44%	1980
October	1st to 10th	Night	12% 8% 2 5% 5% 3 4 4 5% 6% 46%	1980
	11th to 20th	Night	17% 9% 4 7% 6% 2 4 3 4 6% 36%	2160
	21st to end	Night	21% 10% 3 7% 5% 3 4 4 5% 6% 32%	2573
November	1st to 10th	Night	12% 11% 4 5% 5% 3 5% 4 4 6% 41%	2406
	11th to 20th	Night	15% 10% 4 7% 6% 4 6% 6% 6% 7% 30%	2470
	21st to end	Night	17% 13% 5% 8% 5% 3 4 5% 5% 6% 28%	2470
December	1st to 10th	Night	16% 14% 7% 11% 7% 4 5% 6% 5% 6% 20%	2470
	11th to 20th	Night	15% 13% 6% 12% 7% 5% 5% 5% 6% 6% 22%	3260
	21st to end	Night	25% 21% 6% 10% 7% 3 4 4 4 5% 12%	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	66% 7% 12% 12% 3	1518
	11th to 20th	Day	72% 7% 11% 7% 4	1464
	21st to end	Day	71% 5% 8% 11% 5% 1	1684
February	1st to 10th	Day	65% 7% 9% 11% 6% 1	1634
	11th to 20th	Day	62% 6% 9% 15% 8% 1	1758
	21st to end	Day	61% 7% 12% 14% 5% 2	1480
March	1st to 10th	Day	55% 8% 11% 18% 7% 1	1800
	11th to 20th	Day	50% 6% 11% 19% 12% 2	1976
	21st to end	Day	57% 6% 10% 18% 8% 1	2178
April	1st to 10th	Day	54% 6% 9% 20% 10%	2155
	11th to 20th	Day	48% 7% 11% 19% 12% 2	2227
	21st to end	Day	49% 7% 14% 16% 13% 2	2340
May	1st to 10th	Day	50% 8% 11% 19% 10% 1	2340
	11th to 20th	Day	50% 7% 10% 19% 14% 1	2305
	21st to end	Day	40% 9% 14% 24% 12% 2	2583
June	1st to 10th	Day	37% 8% 13% 25% 14% 2	2520
	11th to 20th	Day	36% 8% 14% 22% 17% 2	2520
	21st to end	Day	39% 9% 13% 21% 15% 2	2520
July	1st to 10th	Day	32% 9% 14% 23% 18% 4	2451
	11th to 20th	Day	35% 8% 12% 26% 17% 2	2445
	21st to end	Day	34% 10% 14% 23% 17% 2	2502
August	1st to 10th	Day	34% 10% 15% 25% 13% 1	2314
	11th to 20th	Day	40% 9% 14% 23% 13% 1	2303
	21st to end	Day	35% 7% 13% 25% 17% 3	2471
September	1st to 10th	Day	41% 8% 15% 19% 15% 2	2075
	11th to 20th	Day	33% 8% 12% 31% 16% 1	1980
	21st to end	Day	40% 8% 14% 21% 17%	1980
October	1st to 10th	Day	41% 6% 12% 25% 14% 2	1980
	11th to 20th	Day	51% 6% 12% 20% 11% 1	1800
	21st to end	Day	55% 6% 12% 18% 8% 1	1782
November	1st to 10th	Day	43% 7% 11% 24% 14% 1	1672
	11th to 20th	Day	56% 6% 11% 18% 8% 1	1710
	21st to end	Day	59% 5% 14% 15% 6% 1	1710
December	1st to 10th	Day	63% 8% 11% 13% 5%	1710
	11th to 20th	Day	62% 9% 14% 13% 3	1930
	21st to end	Day	76% 6% 8% 6% 3	2783
January	1st to 10th	Night	62% 7% 10% 15% 6% 1	2648
	11th to 20th	Night	67% 5% 13% 10% 5%	2575
	21st to end	Night	65% 7% 12% 10% 5% 1	2669
February	1st to 10th	Night	65% 7% 10% 12% 5% 1	2322
	11th to 20th	Night	58% 6% 10% 18% 8% 1	2099
	21st to end	Night	58% 4 13% 15% 8% 2	1776
March	1st to 10th	Night	50% 6% 12% 22% 10% 1	2160
	11th to 20th	Night	43% 8% 12% 19% 15% 2	1981
	21st to end	Night	52% 5% 9% 21% 11% 2	2178
April	1st to 10th	Night	46% 7% 11% 22% 14% 1	1821
	11th to 20th	Night	46% 6% 11% 18% 17% 2	1681
	21st to end	Night	47% 5% 12% 20% 13% 3	1620
May	1st to 10th	Night	50% 7% 11% 19% 10% 2	1620
	11th to 20th	Night	44% 8% 10% 18% 18% 2	1593
	21st to end	Night	36% 7% 16% 24% 14% 3	1690
June	1st to 10th	Night	33% 6% 14% 27% 18% 2	1440
	11th to 20th	Night	36% 8% 13% 24% 16% 2	1440
	21st to end	Night	31% 9% 15% 26% 17% 2	1440
July	1st to 10th	Night	29% 7% 14% 25% 21% 4	1400
	11th to 20th	Night	29% 7% 13% 28% 20% 3	1392
	21st to end	Night	26% 10% 16% 25% 21% 3	1575
August	1st to 10th	Night	28% 8% 16% 31% 15% 2	1600
	11th to 20th	Night	31% 9% 15% 27% 16% 3	1598
	21st to end	Night	31% 7% 11% 26% 21% 3	1881
September	1st to 10th	Night	34% 8% 11% 26% 18% 3	1867
	11th to 20th	Night	30% 7% 11% 30% 21% 2	1980
	21st to end	Night	37% 7% 13% 27% 16% 1	1980
October	1st to 10th	Night	39% 6% 12% 23% 19% 1	1980
	11th to 20th	Night	49% 6% 11% 20% 13% 1	2160
	21st to end	Night	52% 5% 11% 21% 9% 1	2573
November	1st to 10th	Night	44% 6% 11% 23% 15% 1	2406
	11th to 20th	Night	52% 7% 14% 18% 8% 1	2470
	21st to end	Night	56% 6% 13% 18% 7%	2470
December	1st to 10th	Night	64% 8% 10% 12% 6%	2470
	11th to 20th	Night	61% 8% 12% 13% 5%	3262
	21st to end	Night	74% 7% 10% 7% 2	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	20% 18% 38% 19% 4 1	270
	11th to 20th	Day	23% 16% 43% 14% 3 1	249
	21st to end	Day	26% 18% 34% 18% 4	264
February	1st to 10th	Day	27% 20% 36% 15% 1	240
	11th to 20th	Day	28% 20% 38% 13% 2	240
	21st to end	Day	28% 27% 32% 12% 1	198
March	1st to 10th	Day	21% 23% 41% 12% 3	240
	11th to 20th	Day	23% 13% 35% 22% 7% 1	416
	21st to end	Day	26% 17% 33% 16% 5% 2	462
April	1st to 10th	Day	21% 14% 36% 20% 9%	420
	11th to 20th	Day	23% 19% 31% 16% 7% 4	412
	21st to end	Day	22% 15% 33% 17% 10% 2	420
May	1st to 10th	Day	24% 13% 30% 20% 10% 2	423
	11th to 20th	Day	21% 10% 29% 21% 11% 7%	447
	21st to end	Day	14% 8% 23% 26% 20% 8%	537
June	1st to 10th	Day	12% 6% 30% 31% 16% 5%	630
	11th to 20th	Day	14% 7% 28% 28% 18% 6%	630
	21st to end	Day	10% 9% 30% 30% 16% 5%	630
July	1st to 10th	Day	7% 5% 19% 31% 25% 12%	621
	11th to 20th	Day	11% 6% 25% 27% 21% 11%	618
	21st to end	Day	8% 3 27% 30% 23% 9%	590
August	1st to 10th	Day	9% 3 17% 30% 21% 19%	446
	11th to 20th	Day	13% 4 20% 25% 28% 10%	439
	21st to end	Day	10% 4 21% 30% 24% 12%	495
September	1st to 10th	Day	15% 6% 22% 24% 22% 11%	450
	11th to 20th	Day	10% 4 21% 24% 28% 13%	450
	21st to end	Day	15% 11% 22% 26% 17% 8%	450
October	1st to 10th	Day	13% 8% 31% 23% 18% 6%	450
	11th to 20th	Day	20% 17% 30% 25% 7% 1	450
	21st to end	Day	31% 18% 33% 14% 4 1	297
November	1st to 10th	Day	14% 18% 34% 24% 8% 2	270
	11th to 20th	Day	20% 26% 29% 20% 5% 1	270
	21st to end	Day	28% 19% 36% 15% 3	270
December	1st to 10th	Day	22% 28% 31% 12% 7% 1	270
	11th to 20th	Day	23% 24% 34% 16% 4	270
	21st to end	Day	24% 26% 33% 17% 1	297
January	1st to 10th	Night	21% 17% 38% 19% 5%	950
	11th to 20th	Night	23% 16% 36% 20% 4 1	920
	21st to end	Night	18% 13% 38% 25% 5%	887
February	1st to 10th	Night	25% 14% 39% 20% 3	720
	11th to 20th	Night	21% 15% 37% 23% 3	703
	21st to end	Night	26% 15% 38% 19% 3	592
March	1st to 10th	Night	20% 13% 35% 25% 6%	720
	11th to 20th	Night	17% 14% 38% 24% 6% 1	720
	21st to end	Night	24% 12% 31% 25% 8%	792
April	1st to 10th	Night	17% 15% 36% 27% 4 1	561
	11th to 20th	Night	20% 11% 36% 23% 9% 1	533
	21st to end	Night	19% 9% 35% 27% 9% 1	540
May	1st to 10th	Night	20% 10% 30% 32% 7% 2	540
	11th to 20th	Night	23% 5% 30% 27% 14% 1	531
	21st to end	Night	12% 3 27% 37% 19% 3	584
June	1st to 10th	Night	11% 2 27% 44% 16%	540
	11th to 20th	Night	12% 4 24% 42% 18% 1	540
	21st to end	Night	9% 3 22% 42% 21% 3	540
July	1st to 10th	Night	7% 2 17% 41% 27% 5%	525
	11th to 20th	Night	10% 2 18% 43% 24% 3	522
	21st to end	Night	6% 1 20% 43% 29% 1	591
August	1st to 10th	Night	8% 2 14% 45% 28% 3	537
	11th to 20th	Night	8% 1 16% 41% 29% 5%	534
	21st to end	Night	11% 2 16% 37% 30% 5%	594
September	1st to 10th	Night	12% 3 20% 36% 25% 5%	607
	11th to 20th	Night	12% 4 17% 33% 31% 4	720
	21st to end	Night	14% 7% 24% 30% 21% 5%	720
October	1st to 10th	Night	15% 7% 26% 31% 19% 2	720
	11th to 20th	Night	20% 15% 31% 25% 8% 1	720
	21st to end	Night	25% 15% 33% 22% 6%	792
November	1st to 10th	Night	18% 13% 30% 27% 11% 1	740
	11th to 20th	Night	20% 17% 35% 22% 6% 1	760
	21st to end	Night	24% 12% 36% 24% 4	760
December	1st to 10th	Night	23% 16% 37% 19% 5%	760
	11th to 20th	Night	23% 15% 39% 20% 3	931
	21st to end	Night	30% 15% 35% 19% 2	1045

Page generated at 2024-01-11 13:32:01. Version ac07

Copyright 2024 Attilla Danko