Geraldton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Geraldton clear sky chart from 2005-11-06 to 2024-01-13.

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	16% 11% 4 8% 7% 4 5% 5% 5% 7% 28%	74558
	Night	14% 12% 5% 9% 7% 4 6% 5% 5% 6% 26%	75181
Transparency	Day	55% 6% 11% 18% 8% 1	74254
	Night	58% 6% 11% 17% 7% 1	75019
Seeing	Day	22% 15% 33% 20% 8% 2	14561
	Night	20% 12% 33% 25% 9% 1	24113

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	10% 14% 8% 11% 12% 7% 8% 5% 9% 5% 12%	1397
	11th to 20th	Day	11% 13% 6% 13% 9% 4 6% 8% 9% 6% 16%	1456
	21st to end	Day	11% 13% 4 11% 9% 6% 9% 9% 7% 8% 12%	1584
February	1st to 10th	Day	6% 12% 5% 9% 9% 6% 10% 8% 6% 8% 21%	1440
	11th to 20th	Day	6% 12% 6% 11% 11% 4 7% 6% 7% 7% 23%	1605
	21st to end	Day	5% 13% 6% 13% 9% 5% 7% 6% 5% 7% 26%	1480
March	1st to 10th	Day	11% 11% 5% 9% 8% 4 6% 6% 5% 6% 29%	1798
	11th to 20th	Day	11% 14% 5% 8% 9% 4 4 5% 4 7% 29%	1858
	21st to end	Day	13% 12% 5% 8% 6% 4 5% 5% 4 5% 33%	2353
April	1st to 10th	Day	14% 13% 6% 8% 7% 4 5% 4 5% 6% 29%	2160
	11th to 20th	Day	18% 14% 5% 7% 5% 3 3 4 5% 5% 30%	2240
	21st to end	Day	15% 12% 5% 6% 5% 3 4 3 5% 6% 35%	2340
May	1st to 10th	Day	20% 11% 4 8% 6% 3 4 5% 4 6% 27%	2515
	11th to 20th	Day	21% 8% 3 6% 6% 3 4 5% 5% 7% 32%	2479
	21st to end	Day	21% 7% 2 5% 6% 3 5% 5% 5% 8% 33%	2918
June	1st to 10th	Day	22% 8% 3 6% 6% 3 5% 5% 5% 5% 31%	2700
	11th to 20th	Day	14% 8% 3 6% 6% 3 4 5% 6% 7% 37%	2700
	21st to end	Day	18% 6% 3 6% 5% 4 4 4 5% 8% 36%	2700
July	1st to 10th	Day	16% 4 2 6% 5% 3 5% 5% 7% 9% 38%	2700
	11th to 20th	Day	14% 6% 3 6% 5% 3 5% 5% 6% 8% 39%	2580
	21st to end	Day	16% 5% 3 5% 6% 4 6% 5% 8% 8% 36%	2743
August	1st to 10th	Day	14% 7% 3 6% 7% 4 7% 6% 7% 8% 32%	2507
	11th to 20th	Day	16% 5% 2 6% 5% 4 5% 5% 6% 8% 39%	2410
	21st to end	Day	16% 8% 3 7% 6% 4 5% 5% 5% 7% 34%	2494
September	1st to 10th	Day	18% 6% 2 6% 6% 3 5% 5% 4 7% 38%	2160
	11th to 20th	Day	25% 10% 3 4 4 3 5% 4 5% 7% 30%	2039
	21st to end	Day	21% 12% 3 7% 6% 2 4 4 4 7% 29%	1980
October	1st to 10th	Day	20% 16% 3 6% 6% 2 4 5% 4 6% 27%	1908
	11th to 20th	Day	23% 19% 5% 8% 6% 3 4 4 6% 6% 17%	1639
	21st to end	Day	21% 22% 7% 8% 6% 4 5% 4 4 5% 14%	1782
November	1st to 10th	Day	17% 16% 8% 13% 7% 4 4 5% 4 5% 17%	1672
	11th to 20th	Day	16% 20% 7% 13% 11% 4 5% 3 4 3 12%	1459
	21st to end	Day	18% 19% 8% 16% 9% 5% 5% 3 4 4 11%	1330
December	1st to 10th	Day	10% 14% 8% 14% 14% 6% 6% 6% 5% 4 12%	1330
	11th to 20th	Day	10% 14% 6% 11% 12% 7% 7% 7% 6% 6% 14%	1671
	21st to end	Day	18% 21% 7% 12% 10% 6% 6% 4 4 3 10%	2431
January	1st to 10th	Night	11% 14% 5% 12% 9% 6% 9% 9% 7% 6% 13%	2767
	11th to 20th	Night	10% 16% 7% 11% 10% 5% 8% 8% 7% 5% 14%	2549
	21st to end	Night	9% 13% 6% 12% 10% 5% 10% 9% 7% 5% 14%	2772
February	1st to 10th	Night	7% 11% 5% 9% 8% 5% 8% 9% 8% 7% 23%	2520
	11th to 20th	Night	8% 12% 5% 9% 9% 7% 8% 6% 6% 7% 23%	2239
	21st to end	Night	7% 12% 6% 11% 9% 4 7% 7% 7% 6% 25%	1776
March	1st to 10th	Night	7% 9% 4 9% 9% 5% 8% 5% 6% 7% 30%	2149
	11th to 20th	Night	11% 12% 5% 9% 9% 4 5% 4 4 6% 32%	2101
	21st to end	Night	12% 11% 5% 8% 7% 4 4 4 3 6% 37%	2018
April	1st to 10th	Night	14% 12% 5% 8% 7% 4 5% 4 6% 6% 29%	1800
	11th to 20th	Night	18% 12% 4 7% 6% 3 5% 5% 5% 7% 29%	1669
	21st to end	Night	17% 10% 4 5% 5% 2 4 5% 6% 6% 37%	1620
May	1st to 10th	Night	21% 12% 3 7% 5% 3 5% 4 4 7% 31%	1442
	11th to 20th	Night	18% 7% 3 7% 5% 4 4 4 5% 6% 36%	1416
	21st to end	Night	20% 7% 2 5% 4 2 4 4 5% 7% 39%	1357
June	1st to 10th	Night	17% 6% 3 5% 5% 3 5% 5% 6% 8% 37%	1260
	11th to 20th	Night	16% 5% 3 5% 4 3 6% 6% 6% 7% 39%	1260
	21st to end	Night	16% 7% 3 5% 5% 3 4 5% 6% 6% 39%	1260
July	1st to 10th	Night	12% 5% 2 3 4 3 5% 4 6% 9% 46%	1260
	11th to 20th	Night	12% 6% 2 6% 5% 3 5% 5% 7% 8% 41%	1376
	21st to end	Night	13% 6% 2 5% 4 3 6% 4 6% 8% 44%	1575
August	1st to 10th	Night	11% 6% 3 7% 5% 3 4 6% 5% 9% 41%	1432
	11th to 20th	Night	12% 5% 2 6% 4 3 4 4 5% 8% 46%	1491
	21st to end	Night	13% 6% 3 5% 6% 3 5% 5% 6% 8% 42%	1858
September	1st to 10th	Night	15% 6% 2 5% 6% 3 4 4 5% 6% 44%	1800
	11th to 20th	Night	20% 8% 3 5% 5% 2 4 4 5% 6% 39%	1903
	21st to end	Night	25% 9% 3 5% 5% 2 4 4 6% 6% 32%	1980
October	1st to 10th	Night	20% 15% 3 5% 6% 3 4 3 4 6% 31%	2049
	11th to 20th	Night	21% 19% 5% 8% 6% 3 4 3 5% 6% 20%	2320
	21st to end	Night	20% 17% 6% 10% 6% 4 5% 5% 5% 5% 17%	2574
November	1st to 10th	Night	18% 17% 8% 10% 8% 3 4 4 4 5% 18%	2406
	11th to 20th	Night	17% 16% 7% 13% 9% 4 6% 4 4 5% 14%	2720
	21st to end	Night	16% 17% 6% 14% 11% 5% 5% 4 4 4 13%	2850
December	1st to 10th	Night	9% 17% 7% 16% 12% 6% 7% 5% 4 5% 12%	2850
	11th to 20th	Night	12% 16% 6% 11% 8% 5% 7% 8% 5% 5% 17%	3526
	21st to end	Night	19% 21% 6% 11% 11% 4 5% 4 4 4 12%	5236

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	71% 4 9% 11% 5%	1398
	11th to 20th	Day	64% 6% 9% 16% 5%	1456
	21st to end	Day	66% 6% 8% 11% 8%	1584
February	1st to 10th	Day	59% 6% 10% 17% 6% 2	1440
	11th to 20th	Day	58% 5% 10% 20% 7%	1614
	21st to end	Day	58% 4 9% 16% 11% 2	1480
March	1st to 10th	Day	56% 5% 10% 15% 13% 1	1800
	11th to 20th	Day	56% 5% 10% 16% 11% 2	1858
	21st to end	Day	53% 5% 8% 20% 12% 1	2353
April	1st to 10th	Day	56% 5% 8% 19% 10% 1	2160
	11th to 20th	Day	56% 5% 8% 20% 10% 1	2240
	21st to end	Day	51% 5% 10% 16% 16% 2	2340
May	1st to 10th	Day	57% 6% 9% 19% 8% 2	2515
	11th to 20th	Day	51% 7% 11% 21% 11% 1	2483
	21st to end	Day	49% 7% 12% 18% 13% 1	2918
June	1st to 10th	Day	53% 6% 10% 18% 12% 1	2700
	11th to 20th	Day	45% 6% 10% 24% 14% 1	2700
	21st to end	Day	46% 7% 13% 25% 9%	2700
July	1st to 10th	Day	40% 8% 13% 29% 10% 1	2626
	11th to 20th	Day	41% 8% 15% 27% 10%	2501
	21st to end	Day	43% 9% 13% 25% 8% 1	2591
August	1st to 10th	Day	45% 11% 17% 20% 7% 1	2492
	11th to 20th	Day	42% 8% 15% 26% 9%	2410
	21st to end	Day	48% 9% 13% 23% 7%	2494
September	1st to 10th	Day	46% 7% 13% 24% 10%	2160
	11th to 20th	Day	53% 8% 17% 17% 5%	2039
	21st to end	Day	56% 5% 13% 19% 7%	1980
October	1st to 10th	Day	58% 7% 14% 18% 4	1908
	11th to 20th	Day	67% 7% 11% 14% 1	1639
	21st to end	Day	72% 6% 10% 10% 1	1782
November	1st to 10th	Day	69% 6% 11% 11% 2	1672
	11th to 20th	Day	78% 5% 8% 7% 3	1459
	21st to end	Day	78% 5% 8% 6% 3	1330
December	1st to 10th	Day	74% 6% 9% 8% 3	1330
	11th to 20th	Day	69% 6% 8% 14% 4	1671
	21st to end	Day	80% 4 5% 8% 3	2431
January	1st to 10th	Night	68% 6% 9% 14% 4	2767
	11th to 20th	Night	68% 5% 9% 13% 4	2549
	21st to end	Night	67% 5% 7% 13% 7%	2772
February	1st to 10th	Night	56% 6% 11% 18% 9% 1	2520
	11th to 20th	Night	59% 5% 10% 18% 8%	2240
	21st to end	Night	57% 5% 12% 16% 9% 1	1776
March	1st to 10th	Night	52% 6% 9% 19% 12% 1	2160
	11th to 20th	Night	53% 5% 10% 21% 9% 2	2102
	21st to end	Night	51% 5% 8% 18% 15% 3	2018
April	1st to 10th	Night	56% 6% 8% 17% 11% 2	1800
	11th to 20th	Night	53% 5% 10% 19% 11% 2	1669
	21st to end	Night	47% 6% 11% 19% 14% 3	1620
May	1st to 10th	Night	54% 5% 9% 22% 9% 1	1442
	11th to 20th	Night	48% 6% 9% 21% 15% 1	1417
	21st to end	Night	45% 8% 13% 20% 13% 2	1358
June	1st to 10th	Night	44% 8% 11% 26% 11%	1260
	11th to 20th	Night	41% 7% 12% 24% 15% 1	1260
	21st to end	Night	44% 8% 14% 24% 10% 1	1260
July	1st to 10th	Night	32% 8% 17% 27% 15% 1	1225
	11th to 20th	Night	38% 9% 14% 29% 10% 1	1332
	21st to end	Night	37% 9% 17% 26% 10% 1	1487
August	1st to 10th	Night	38% 9% 19% 26% 7% 1	1423
	11th to 20th	Night	36% 8% 16% 28% 12%	1491
	21st to end	Night	39% 9% 17% 26% 8%	1858
September	1st to 10th	Night	40% 8% 14% 28% 9% 1	1800
	11th to 20th	Night	47% 6% 20% 22% 5%	1903
	21st to end	Night	52% 7% 14% 19% 7%	1980
October	1st to 10th	Night	55% 6% 15% 17% 6%	2049
	11th to 20th	Night	65% 7% 11% 15% 2	2320
	21st to end	Night	68% 7% 11% 11% 3	2574
November	1st to 10th	Night	69% 7% 10% 11% 3	2406
	11th to 20th	Night	72% 6% 9% 11% 3	2720
	21st to end	Night	75% 6% 9% 7% 3	2850
December	1st to 10th	Night	76% 5% 7% 9% 4	2850
	11th to 20th	Night	66% 6% 8% 14% 6%	3525
	21st to end	Night	77% 4 6% 10% 3	5236

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	19% 15% 40% 19% 7%	213
	11th to 20th	Day	13% 14% 32% 26% 12% 2	246
	21st to end	Day	16% 17% 38% 20% 8% 2	264
February	1st to 10th	Day	16% 18% 43% 20% 3 1	240
	11th to 20th	Day	11% 25% 45% 13% 3 3	240
	21st to end	Day	15% 25% 46% 12% 2	198
March	1st to 10th	Day	18% 17% 37% 22% 6%	240
	11th to 20th	Day	22% 17% 39% 15% 5% 2	298
	21st to end	Day	19% 16% 38% 17% 6% 3	462
April	1st to 10th	Day	23% 17% 32% 22% 5% 1	420
	11th to 20th	Day	29% 18% 23% 20% 9% 1	412
	21st to end	Day	22% 16% 32% 20% 7% 3	420
May	1st to 10th	Day	26% 16% 32% 18% 6% 2	598
	11th to 20th	Day	25% 14% 33% 17% 9% 2	625
	21st to end	Day	26% 17% 32% 19% 6% 1	679
June	1st to 10th	Day	26% 12% 34% 20% 7% 2	630
	11th to 20th	Day	19% 15% 35% 21% 8% 2	630
	21st to end	Day	19% 13% 34% 21% 9% 3	630
July	1st to 10th	Day	16% 13% 35% 23% 11% 3	621
	11th to 20th	Day	13% 15% 31% 26% 12% 3	618
	21st to end	Day	14% 10% 33% 26% 13% 4	684
August	1st to 10th	Day	16% 13% 33% 25% 10% 3	626
	11th to 20th	Day	16% 12% 27% 27% 12% 6%	546
	21st to end	Day	22% 13% 30% 21% 12% 3	495
September	1st to 10th	Day	22% 13% 30% 21% 10% 4	450
	11th to 20th	Day	30% 13% 27% 16% 12% 2	450
	21st to end	Day	30% 12% 24% 23% 10% 1	450
October	1st to 10th	Day	29% 15% 31% 16% 8% 2	378
	11th to 20th	Day	31% 19% 33% 13% 5%	270
	21st to end	Day	32% 19% 35% 10% 3 1	297
November	1st to 10th	Day	27% 18% 33% 17% 4	270
	11th to 20th	Day	26% 19% 35% 15% 4 2	223
	21st to end	Day	27% 22% 33% 16% 2 1	180
December	1st to 10th	Day	20% 18% 31% 19% 7% 5%	180
	11th to 20th	Day	25% 12% 38% 18% 6% 1	180
	21st to end	Day	20% 19% 32% 20% 6% 4	198
January	1st to 10th	Night	19% 15% 39% 21% 6%	950
	11th to 20th	Night	18% 14% 33% 27% 6% 1	911
	21st to end	Night	16% 13% 36% 26% 8% 1	990
February	1st to 10th	Night	13% 13% 39% 27% 7% 1	900
	11th to 20th	Night	15% 14% 37% 23% 10% 2	796
	21st to end	Night	12% 13% 40% 25% 9% 1	592
March	1st to 10th	Night	12% 15% 35% 28% 10% 1	720
	11th to 20th	Night	18% 16% 35% 22% 7% 1	720
	21st to end	Night	19% 13% 32% 24% 10% 2	632
April	1st to 10th	Night	23% 11% 33% 24% 7% 2	540
	11th to 20th	Night	23% 12% 29% 27% 8% 1	533
	21st to end	Night	19% 10% 33% 27% 9% 1	540
May	1st to 10th	Night	27% 9% 29% 27% 8%	540
	11th to 20th	Night	23% 10% 30% 29% 6% 1	531
	21st to end	Night	24% 10% 33% 30% 3	389
June	1st to 10th	Night	19% 7% 36% 28% 11%	360
	11th to 20th	Night	19% 10% 31% 32% 7% 1	360
	21st to end	Night	18% 9% 33% 29% 10% 1	360
July	1st to 10th	Night	13% 10% 33% 32% 11%	350
	11th to 20th	Night	14% 8% 35% 32% 10% 1	462
	21st to end	Night	16% 6% 29% 32% 15% 1	591
August	1st to 10th	Night	13% 7% 29% 38% 11% 1	537
	11th to 20th	Night	13% 7% 29% 30% 20% 1	534
	21st to end	Night	15% 8% 38% 26% 13% 1	594
September	1st to 10th	Night	18% 8% 29% 31% 12% 1	540
	11th to 20th	Night	25% 8% 35% 25% 7%	643
	21st to end	Night	31% 11% 23% 23% 11% 1	720
October	1st to 10th	Night	28% 15% 26% 22% 7% 1	720
	11th to 20th	Night	31% 12% 29% 22% 6% 1	720
	21st to end	Night	27% 12% 30% 21% 10% 1	792
November	1st to 10th	Night	26% 16% 30% 21% 6% 1	740
	11th to 20th	Night	27% 16% 31% 19% 5% 1	911
	21st to end	Night	27% 15% 32% 20% 5%	950
December	1st to 10th	Night	18% 18% 34% 19% 10% 1	950
	11th to 20th	Night	20% 14% 34% 23% 8% 2	950
	21st to end	Night	25% 13% 31% 20% 10% 2	1045

Page generated at 2024-01-10 01:25:00. Version ac07

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