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Transparency and Planetary Observing

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#1 DAG792


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Posted 23 September 2021 - 02:24 AM

Hello everyone,

                         So as most of you might know, Jupiter is covered with low-contrast details that are easily washed out in even moderately bad seeing. But in the past previous nights, I've come to the realization that transparency too plays a part in observing these details.

Few nights ago, I had hazy weather with very excellent (sub-arcsecond seeing). The airy disk and the first ring was easily visible in both my 6 inch and 10 inch scopes. If I had to guess, I would say it was around Pickering 8.Transparency was horrible though, with NELM hovering around 3.5(average where I live is 4.5-5). Even looking naked-eye, one could easily see that the planets appeared a lot dimmer.

Jupiter showed a lot of detail that night, and appeared very sharp; in fact at that time I thought I had near-perfect conditions for planetary observing.


Two or three nights later however, I had the luck of witnessing a truly excellent night for astronomy, with both excellent seeing(same as the previous mentioned night) and excellent transparency(NELM approaching 5.5). These sort of conditions are quite rare where I live, as this was the first time I experienced them.

However, on this night I could see more detail on Jupiter than ever before. Especially the small scale details like turbulence in the bands seemed to pop out more than before. Seeing the 'string of pearls' was easy in the 6 incher as compared to before, and  could pick out a lot of detail in the polar regions with the 10 inch scope. The colors also appeared more vivid.

Now I don't know whether this was me not judging the seeing well enough, and actually the seeing was better on the latter night; or it was the fact that transparency plays a role in planetary observing, which is why I wanted to hear your thoughts on this


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#2 PKDfan


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Posted 23 September 2021 - 03:40 AM

Hi DAG792! I am at 53.5°N and have observed nearly ever clear night for the last 5 months. Jupiter rises no higber than 24 degrees here (last spring) and if Stellarium is to be trusted its at 21.7° now.

I use a 4" apo.

Every observation has been unique, with varying amounts of transparency and the seeing only mediocre to sometimes good.

The views have been all over the map, sometimes decent amounts of colour is seen in the main belts other times only barely there colour much subdued.

Once with great transparency I was treated to intense vibrancy.

Detail beyond the tropical belts is almost always missing and the view is quite hohum. I stick with it because there are moments of goodness, sometimes.

In 70 plus hours I've maybe a hour of good views and incredible views maybe a couple handfuls of seconds.

All that time invested was absolutely worthwhile as they previewed the great times ahead in the next couple of years.

My scope is very very good but if I was new at this I may be disappointed with the initial views of Jupiter but with more time it does becomes clear.
Some may not give it a proper chance but I knew otherwise and in those brief fleeting seconds, a Hubblesque view emerged, pleasing me to no end!

The quality does show, eventually!

New members note this well!!!

The variabity of views is tedious to deal with and I long for it to be much higher in the sky.

Transparency is the great multiplyer, it adds vibrancy to the image and low contrast detail becomes much easier to detect.

Patience, patience, patience is certainly the requirement for me up here in Edmonton.

Clear skies & Good seeing

Edited by PKDfan, 23 September 2021 - 03:46 AM.

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#3 sanbai



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Posted 23 September 2021 - 04:40 PM

Here in Baton Rouge is quite usual to have good seeing and bad transparency. My experience is similar. Transparency is not a limiting factor for magnification but it lowers the contrast, indeed.

There's still some situations were low transparency could be a plus. Mars at opposition has a very high area-brightness. The high contrast against the dark sky makes observing difficult. Low transparency acts like a neutral density filter and makes observing more comfortable.

In any case, I prefer good seeing and good transparency. Tonight e have such a (rare) night and I'm ready for a planetary session in my backyard :)

#4 ButterFly



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Posted 23 September 2021 - 07:31 PM

No doubt about it.  When the Moon is out as well, the smoke/fog/haze/clouds are bright too, robbing even more contrast.  But don't let that stop your trying!  When those get real bad, it's worth my driving up the mountain where the seeing is often poor, but there's less junk.  The air calms down sometimes, but the junk doesn't just blow away for a few seconds.

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