KK6FAH_Section

Have you ever wondered why during certain periods of the month the EME conditions appear to be "extremely good" or even outstanding, while during a subsequent period of the month the conditions appear to be "extremely poor" for many days? Is going from "extremely good" to "extremely poor" throughout a month a consistent pattern in the world of EME, or these "swings" in the quality of the conditions could become much "less extreme" at some point in time? In other words, could we see conditions that are let's say "consistently fair" throughout the entire the month, but never see the extremes "good" and "bad"? How dynamic is this whole thing really?

Just like it is the case for most phenonena in astronomy, the key factors affecting the quality of the EME conditions follow complex and dynamic cycles and one may not fully appreciate the implications of these unless an analysis covering a long period in time is performed (i.e. many years). That is precisely the purpose of this section

Before elaborating further on this subject, it is important to emphasize that each QTH and Station setup is unique, hence, the analysis described in this page cannot be generalized to all locations and EME stations. However, the key concepts can be utilized so the reader can perform the same type of analysis based on its own situation. Additionally, I purposely did not include the degradation factor (DGR) in the current analysis in order for the reader to better understand the logic behind the key concepts as opposed to blindly rely on a factor which is generic at best.

3) Moon Declination: generally speaking, for most EME practitioners who live in an urban area, higher the Moon declination the better. Why? Simple, at low elevations, city and man-made noise can be prohibitively high so having the moon located at high elevations will help reducing the noise level very significantly.

When we plot the 3 main factors mentioned above, the combination of these enables predicting the quality of the EME conditions that will be in effect during any period of the month with pretty accuracy. Obviously, we are looking at a qualitative analysis of the EME conditions here, not a quantitative one.

From July 3 until July 11, the Moon distance gradually increases until it reaches a Maximum on July 7, and then the distance decreases again. To the contrary, during the same period, the Moon declination decreases until it reaches a minimum on July 8, and then it starts increasing again. IN this case, the Moon declination is almost perfectly "out-of-phase" with Moon distance. Finally, mainly due to the combined presence of the Milky Way Center and the Moon, the Sky Noise also increases rapidly from July 3 and beyond until it reaches a maximum on July 7 and then decreases again the following days. In this particular case, the Sky Noise increase is "in-phase" with the Moon distance increase and "out-of-phase" with the delination.

What does this all mean? Well, let's use qualitative attributes to describe the impact of these 3 factors on the quality of the EME conditions for the July 3-11 period considered, i.e. Negative (-) or a Positive (+) impact. The table below summarizes the results, see column July 3-11 (2017).

One can see that the aggregate impact of the 3 factors is ALL Negative (-) for the July 3-11 period so the quality of the EME conditions is expected to be Very Bad. In other words, the combination of the Moon distance being very large, the Sky Noise being high (due to Milky Way Center presence alongside the Moon), and the Moon declination being low will yield very bad conditions.

On the other hand, if we look at the July 17-25 period of the same month, the situation is exactly opposite, that is, the Moon distance will be low, the Sky Noise will be low (Milky Way Center NOT present alongside the Moon), and the declination will be high. These are all Positive (+) attributes for the EME conditions. The results? Excellent conditions are expected!

PS: Obviously, conditions will be very bad on July7th due to the Milky Way being perfectly aligned with the Moon and quite degraded on July 23 due to Sun alignment. But as these are more 1-2 day extreme phenomena, they are not discussed in this analysis which focuses on the broader monthly trends.

The analysis above is interesting where for the period considered (July 2017), we will see "Extreme" changes from one portion of the month to the other. In other words, the conditions for the first half of the month are expected to be Very Bad, but they will quickly improve to become Excellent or even outstanding for the last portion of the month. Obviously, between these two extreme scenarios, there is a short transition period that yields more Average conditions. This very pattern is also fairly representative of the conditions that are in effect as I am writing this webpage (i.e. August 2016). Simple right?

If we move 5 years forward in time, that is July 2022, the situation will be quite different. We can see on the Moon graph to the right that the declination and the Moon distance will be almost perfectly "in-phase", and the Sky Noise almost perfectly "out-of-phase" versus the Moon distance and the declination. What will be the resulting EME conditions under such scenario?

If we follow the same logic and analysis, we end up with the table below:

Dimensions	July 8-16 (2017)	July 22-30 (2017)
Moon Distance	Positive (+)	Negative (-)
Sky Noise	Negative (-)	Positive (+)
Moon Declination	Negative (-)	Positive (+)
EME Conditions	Bad-to-Fair	Fair/Average

Interestingly, in this particular case, the conditions throughout the month will never be extremely bad or extremely good, but just about Bad-to-Fair/Average throughout the entire month, quite a different situation compared to July 2017, where for a big portion of the month, the conditions were "Excellent"!

PS: Obviously, conditions will be very bad on July12th due to the Milky Way being perfectly aligned with the Moon and quite degraded on July 28-29 due to Sun alignment. But as these are more 1-2 day phenomena, they are not discussed in this analysis which focuses on the broader monthly trends.

WHAT TO EXPECT IN 2016-2017 and Beyond...

2016 and 2017 are quite similar, that is, we see the extreme scenarios where the conditions tend to be "Very Bad" for a sizable portion of the month, and then they rapidly shift towards being "Excellent" for the second portion of the cycle. As explained above, that is due to the fact that the 3 main factors are either ALL aligned to have a positive impact, or a negative one.

In the summer of 2022, the conditions will never be "Excellent", but more average throughout the entire month. Quite a different situation compared to 2017. Obviously, there is going to be a gradual transition between 2017 and 2022 with a mix picture.

Bottom line, enjoy 2016 and 2017 as much as possible as these periods of "Excellent" conditions will soon go away!

Dimensions	July 3-11 (2017)	July 17-25 (2017)
Moon Distance	Negative (-)	Positive (+)
Sky Noise	Negative (-)	Positive (+)
Moon Declination	Negative (-)	Positive (+)
EME Conditions	Very Bad	Excellent