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Mark Slade Remote Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mark Slade Remote Observatory clear sky chart from 2005-11-06 to 2024-01-15.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
38%
23604
21%
74705
12%
23557
49%
23557
25%
46888

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
20%
757
25%
2521
8%
757
39%
757
23%
1503
January11th to 20thNight
26%
740
23%
2404
9%
740
43%
740
19%
1554
January21st to endNight
24%
792
25%
2574
11%
792
42%
792
24%
1568
February1st to 10thNight
25%
720
19%
2340
9%
720
39%
720
21%
1501
February11th to 20thNight
16%
700
21%
2238
5%
699
35%
699
20%
1418
February21st to endNight
20%
592
25%
1767
9%
592
39%
592
21%
1151
March1st to 10thNight
23%
720
26%
1980
9%
720
40%
720
27%
1232
March11th to 20thNight
23%
720
21%
1980
9%
720
34%
720
23%
1313
March21st to endNight
23%
792
20%
2171
8%
792
35%
792
24%
1440
April1st to 10thNight
25%
720
20%
1800
5%
720
36%
720
27%
1205
April11th to 20thNight
34%
711
22%
1775
7%
711
41%
711
33%
1144
April21st to endNight
35%
720
21%
1800
8%
720
41%
720
31%
1197
May1st to 10thNight
35%
583
17%
1663
8%
583
42%
583
24%
1124
May11th to 20thNight
40%
495
16%
1556
8%
495
46%
495
23%
1032
May21st to endNight
53%
388
16%
1551
16%
388
57%
388
20%
954
June1st to 10thNight
58%
360
18%
1440
19%
360
64%
360
25%
822
June11th to 20thNight
55%
360
15%
1440
16%
360
59%
360
21%
874
June21st to endNight
59%
360
18%
1440
19%
360
65%
360
25%
831
July1st to 10thNight
57%
350
16%
1400
18%
350
61%
350
21%
846
July11th to 20thNight
70%
510
16%
1554
14%
510
71%
510
32%
960
July21st to endNight
63%
591
16%
1672
12%
558
67%
558
29%
1079
August1st to 10thNight
66%
537
16%
1600
13%
534
67%
534
25%
1089
August11th to 20thNight
61%
596
16%
1660
11%
596
62%
596
26%
1138
August21st to endNight
61%
792
18%
1980
11%
792
62%
792
29%
1361
September1st to 10thNight
58%
720
22%
1800
13%
720
60%
720
31%
1220
September11th to 20thNight
60%
720
29%
1800
21%
720
63%
720
36%
1161
September21st to endNight
46%
720
19%
2078
15%
720
51%
720
24%
1408
October1st to 10thNight
48%
720
21%
2160
20%
720
54%
720
28%
1374
October11th to 20thNight
42%
720
26%
2160
19%
720
54%
720
28%
1338
October21st to endNight
36%
792
28%
2376
18%
792
50%
792
30%
1435
November1st to 10thNight
39%
740
28%
2253
17%
740
53%
740
31%
1311
November11th to 20thNight
32%
760
25%
2493
14%
760
48%
760
27%
1463
November21st to endNight
37%
760
25%
2660
14%
760
53%
760
27%
1487
December1st to 10thNight
26%
760
21%
2660
9%
760
42%
760
21%
1669
December11th to 20thNight
28%
760
22%
3174
11%
759
44%
759
19%
1893
December21st to endNight
30%
826
15%
4785
12%
817
45%
817
12%
2793

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 ForecastData
Points
Cloud CoverDay
14%5%25%5%35%5%6%8%43%
74676
Night
14%6%25%5%345%5%7%44%
75116
TransparencyDay
39%7%12%23%16%3
74391
Night
38%7%11%22%17%4
74920
SeeingDay
18%11%26%25%15%5%
13897
Night
17%9%29%30%14%1
23621

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
15%7%36%4345%5%6%44%
1640
11th to 20thDay
16%8%345%34447%41%
1662
21st to endDay
15%7%36%436%45%5%43%
1782
February1st to 10thDay
14%9%36%6%445%5%7%38%
1620
11th to 20thDay
18%7%35%434446%43%
1607
21st to endDay
18%7%36%6%35%5%5%7%36%
1487
March1st to 10thDay
13%5%245%2445%6%48%
1980
11th to 20thDay
17%6%24445%5%5%6%41%
1980
21st to endDay
17%6%36%5%35%46%7%38%
2184
April1st to 10thDay
12%5%244345%5%7%48%
2160
11th to 20thDay
14%5%25%42445%7%48%
2134
21st to endDay
17%6%35%435%45%6%41%
2160
May1st to 10thDay
15%6%345%35%5%6%8%40%
2312
11th to 20thDay
18%6%25%435%5%6%7%39%
2336
21st to endDay
15%5%245%35%5%6%9%41%
2725
June1st to 10thDay
11%5%245%35%5%5%10%44%
2520
11th to 20thDay
10%5%35%6%35%5%6%9%41%
2520
21st to endDay
8%3246%36%5%7%10%44%
2520
July1st to 10thDay
10%5%36%5%46%5%7%10%40%
2520
11th to 20thDay
6%3246%46%7%9%11%43%
2349
21st to endDay
9%5%26%6%47%6%8%9%38%
2547
August1st to 10thDay
9%5%36%6%46%7%7%11%36%
2327
11th to 20thDay
12%5%25%7%46%7%7%9%35%
2223
21st to endDay
11%5%25%6%36%5%6%9%42%
2376
September1st to 10thDay
15%4245%36%5%5%7%45%
2160
11th to 20thDay
12%425%4345%6%9%47%
2156
21st to endDay
20%6%25%4345%5%6%39%
1881
October1st to 10thDay
16%5%345%335%47%47%
1800
11th to 20thDay
17%424424345%50%
1800
21st to endDay
14%6%25%423447%49%
1980
November1st to 10thDay
13%4235%34346%53%
1824
11th to 20thDay
15%5%2342446%6%50%
1682
21st to endDay
16%424334445%51%
1520
December1st to 10thDay
16%6%25%4345%6%7%42%
1520
11th to 20thDay
17%6%24434246%49%
1910
21st to endDay
19%6%35%4345%5%8%38%
2772
January1st to 10thNight
16%6%24424346%48%
2521
11th to 20thNight
17%7%25%5%4446%6%41%
2404
21st to endNight
15%7%25%424446%46%
2574
February1st to 10thNight
16%7%25%5%35%5%6%7%41%
2340
11th to 20thNight
19%7%25%423446%43%
2237
21st to endNight
16%7%35%4335%5%6%43%
1767
March1st to 10thNight
14%424434445%51%
1980
11th to 20thNight
19%5%245%2445%6%43%
1980
21st to endNight
15%6%35%5%3445%6%43%
2171
April1st to 10thNight
14%6%345%3445%7%45%
1800
11th to 20thNight
12%5%25%5%3435%8%49%
1775
21st to endNight
18%424425%45%7%45%
1800
May1st to 10thNight
17%6%25%435%45%9%39%
1663
11th to 20thNight
17%6%26%5%35%5%6%8%38%
1556
21st to endNight
13%5%346%35%45%10%41%
1550
June1st to 10thNight
10%5%35%5%345%7%9%45%
1440
11th to 20thNight
12%5%346%45%5%6%8%42%
1440
21st to endNight
9%4245%35%7%8%10%44%
1440
July1st to 10thNight
8%7%25%6%346%7%9%41%
1440
11th to 20thNight
6%4245%46%7%6%11%45%
1607
21st to endNight
7%4246%5%7%8%8%11%38%
1771
August1st to 10thNight
9%416%6%47%6%7%9%39%
1611
11th to 20thNight
11%6%46%6%46%5%7%9%36%
1660
21st to endNight
11%6%36%5%446%6%10%39%
1980
September1st to 10thNight
14%6%25%5%245%5%7%45%
1800
11th to 20thNight
10%6%25%43445%7%50%
1800
21st to endNight
19%7%35%42445%6%41%
2078
October1st to 10thNight
18%6%24433446%46%
2160
11th to 20thNight
16%6%15%424446%48%
2160
21st to endNight
15%42443445%6%49%
2376
November1st to 10thNight
12%5%25%434436%53%
2253
11th to 20thNight
14%6%25%42435%6%49%
2493
21st to endNight
13%4244245%5%7%51%
2660
December1st to 10thNight
16%7%35%5%2445%6%42%
2660
11th to 20thNight
18%6%25%433446%45%
3285
21st to endNight
17%6%35%435%5%5%8%40%
4884

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
40%6%10%22%17%5%
1641
11th to 20thDay
43%5%11%21%17%3
1662
21st to endDay
42%5%8%23%17%4
1782
February1st to 10thDay
44%6%11%24%12%3
1620
11th to 20thDay
43%5%8%22%18%4
1616
21st to endDay
47%6%11%14%17%4
1487
March1st to 10thDay
37%5%10%23%21%4
1980
11th to 20thDay
43%6%9%18%18%7%
1980
21st to endDay
45%6%10%18%16%5%
2184
April1st to 10thDay
35%6%12%21%19%8%
2160
11th to 20thDay
36%6%10%20%22%6%
2134
21st to endDay
42%7%10%23%13%5%
2160
May1st to 10thDay
40%8%14%19%16%2
2312
11th to 20thDay
43%8%13%23%12%2
2340
21st to endDay
39%9%14%26%12%1
2725
June1st to 10thDay
35%9%14%26%15%1
2520
11th to 20thDay
38%9%15%22%15%2
2520
21st to endDay
33%10%15%25%17%1
2520
July1st to 10thDay
38%10%12%21%15%3
2450
11th to 20thDay
30%12%17%25%14%2
2279
21st to endDay
38%10%12%22%17%1
2405
August1st to 10thDay
39%11%15%24%10%
2314
11th to 20thDay
41%11%14%21%12%1
2223
21st to endDay
36%9%15%23%14%3
2376
September1st to 10thDay
38%9%11%19%19%4
2160
11th to 20thDay
33%6%10%27%20%4
2156
21st to endDay
44%7%10%19%17%3
1881
October1st to 10thDay
38%5%10%25%18%3
1800
11th to 20thDay
36%5%9%25%22%3
1800
21st to endDay
35%5%9%24%23%5%
1980
November1st to 10thDay
33%410%24%24%5%
1824
11th to 20thDay
35%5%10%22%21%7%
1682
21st to endDay
35%6%9%24%22%4
1520
December1st to 10thDay
40%7%12%25%12%4
1520
11th to 20thDay
38%47%31%14%6%
1906
21st to endDay
43%8%11%26%11%1
2772
January1st to 10thNight
39%49%22%19%7%
2521
11th to 20thNight
44%5%11%20%17%3
2404
21st to endNight
39%49%24%21%3
2574
February1st to 10thNight
42%6%10%24%15%3
2340
11th to 20thNight
43%48%21%17%7%
2239
21st to endNight
42%5%9%20%18%6%
1767
March1st to 10thNight
35%6%9%25%21%3
1980
11th to 20thNight
42%6%10%20%19%4
1980
21st to endNight
41%6%10%21%16%6%
2171
April1st to 10thNight
38%7%10%18%22%6%
1800
11th to 20thNight
34%6%11%21%21%6%
1775
21st to endNight
38%6%12%26%13%6%
1800
May1st to 10thNight
41%9%11%21%14%4
1663
11th to 20thNight
42%9%14%18%15%2
1557
21st to endNight
39%9%14%24%12%1
1551
June1st to 10thNight
33%9%15%27%14%1
1440
11th to 20thNight
38%9%16%21%14%2
1440
21st to endNight
32%11%17%19%19%3
1440
July1st to 10thNight
37%10%17%18%14%4
1400
11th to 20thNight
31%10%19%24%13%2
1554
21st to endNight
32%13%17%24%13%1
1672
August1st to 10thNight
38%13%15%21%12%1
1600
11th to 20thNight
41%10%15%21%13%1
1660
21st to endNight
39%10%16%21%13%2
1980
September1st to 10thNight
38%8%11%21%16%5%
1800
11th to 20thNight
34%7%10%24%22%3
1800
21st to endNight
44%7%10%20%17%3
2078
October1st to 10thNight
40%5%10%24%18%4
2160
11th to 20thNight
37%6%7%24%21%4
2160
21st to endNight
35%5%9%22%23%5%
2376
November1st to 10thNight
33%5%9%24%23%6%
2253
11th to 20thNight
37%48%21%23%7%
2493
21st to endNight
33%5%10%25%21%5%
2660
December1st to 10thNight
42%5%10%23%15%4
2660
11th to 20thNight
40%5%9%21%20%5%
3288
21st to endNight
40%8%13%23%14%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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
24%22%29%21%4
238
11th to 20thDay
26%28%24%18%4
254
21st to endDay
25%25%35%11%5%
264
February1st to 10thDay
24%28%28%15%5%
240
11th to 20thDay
32%25%32%11%
274
21st to endDay
28%20%30%20%2
346
March1st to 10thDay
20%21%35%19%4
420
11th to 20thDay
23%21%31%19%5%
420
21st to endDay
24%17%33%18%6%1
462
April1st to 10thDay
23%20%29%22%6%1
420
11th to 20thDay
17%18%27%22%13%4
412
21st to endDay
23%13%32%21%10%1
420
May1st to 10thDay
19%16%33%19%10%3
423
11th to 20thDay
21%8%31%25%12%3
447
21st to endDay
20%423%26%22%5%
485
June1st to 10thDay
13%5%25%32%18%7%
450
11th to 20thDay
12%6%27%28%19%8%
450
21st to endDay
8%5%26%36%20%6%
450
July1st to 10thDay
11%317%29%28%11%
445
11th to 20thDay
5%14%39%28%13%
444
21st to endDay
12%419%31%25%10%
488
August1st to 10thDay
11%418%26%30%11%
446
11th to 20thDay
13%315%30%28%11%
439
21st to endDay
12%317%28%23%16%
495
September1st to 10thDay
16%417%27%18%18%
450
11th to 20thDay
13%417%30%24%12%
450
21st to endDay
26%9%22%26%13%4
450
October1st to 10thDay
22%5%22%26%18%8%
450
11th to 20thDay
17%13%24%27%17%2
450
21st to endDay
16%12%34%26%8%3
495
November1st to 10thDay
17%10%30%25%14%3
440
11th to 20thDay
19%10%36%22%12%2
342
21st to endDay
22%12%33%21%11%1
180
December1st to 10thDay
19%21%36%17%6%2
180
11th to 20thDay
21%16%34%21%9%
180
21st to endDay
26%18%28%18%9%1
198
January1st to 10thNight
21%17%39%20%4
760
11th to 20thNight
21%14%33%28%4
740
21st to endNight
18%16%39%25%2
792
February1st to 10thNight
21%12%39%24%3
720
11th to 20thNight
25%18%38%18%1
703
21st to endNight
22%16%38%21%2
592
March1st to 10thNight
19%16%38%25%3
720
11th to 20thNight
21%15%37%21%5%1
720
21st to endNight
17%16%38%23%5%
792
April1st to 10thNight
17%17%38%23%5%
720
11th to 20thNight
14%13%34%29%10%
711
21st to endNight
20%8%33%30%8%
720
May1st to 10thNight
20%9%32%27%12%1
583
11th to 20thNight
19%429%33%15%
495
21st to endNight
15%319%39%23%1
389
June1st to 10thNight
10%321%45%20%1
360
11th to 20thNight
14%319%41%22%1
360
21st to endNight
9%221%47%20%1
360
July1st to 10thNight
11%220%33%31%3
350
11th to 20thNight
7%111%39%36%5%
510
21st to endNight
9%217%39%30%3
591
August1st to 10thNight
11%111%43%31%3
537
11th to 20thNight
13%312%41%29%3
596
21st to endNight
13%313%36%30%6%
792
September1st to 10thNight
16%315%32%29%5%
720
11th to 20thNight
12%317%33%31%3
720
21st to endNight
23%5%19%33%19%1
720
October1st to 10thNight
20%419%31%21%4
720
11th to 20thNight
18%7%29%29%16%1
720
21st to endNight
18%8%33%27%12%1
792
November1st to 10thNight
15%8%33%30%13%1
740
11th to 20thNight
18%11%35%28%9%
760
21st to endNight
15%11%33%30%10%1
760
December1st to 10thNight
20%10%38%23%9%
760
11th to 20thNight
19%9%39%28%5%
760
21st to endNight
21%11%33%31%4
836
Page generated at 2024-01-12 16:17:47. Version ac07

Copyright 2024 Attilla Danko


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