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#1 Lite2



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Posted 11 July 2018 - 11:13 PM

How do you "enumerate" seeing for a given night?

All I can do Is say well it's pretty clear and the stars aren't "twinkling" and call it a good night...





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Posted 11 July 2018 - 11:31 PM

What you've just described captures nearly all of it. The next step up would be a 60mm grab-n-go for a quick check. Seeing can be quite fickle. There are high-end seeing gizmos that typically train on Polaris and report a running metric.  Tom

#3 Stonius


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Posted 11 July 2018 - 11:46 PM

A lot of the guys who throw numbers around with confidence are photographers. Their software allows them to measure the exact resolution the seeing affords them. I find eyeballing to be fairly inexact myself.





#4 DLuders



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Posted 12 July 2018 - 01:40 AM

The website ClearDarkSky.com has a graphic for various sites in Indiana to show the "Seeing" realtime conditions, and a forecast.  For example, here is the data for the Logansport, IN site and the "Seeing" scale of 1-5.  Logansport has a 4/5 "Good Seeing" rating right now --    


Logansport ClearDarkSky.JPG



#5 BQ Octantis

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Posted 12 July 2018 - 02:10 AM

I'm not so fortunate to have a Clear Sky Chart for central Australia. But Meteoblue has excellent seeing forecasts (fairly accurate out to a couple of days). Here's your forecast (assuming you're somewhere close to Bloomington):




The first seeing index is your seeing; the second is more indicative of the jet stream. You're currently at seeing = 5/5, jet stream = 7 m/s, which is ****-near mythical in central Australia! I hope you were out shooting the planets…




P.S. Seeing of 1/5 just doesn't do bad seeing any justice—you know the seeing is really bad when the stars at zenith are twinkling and you can see them moving relative to each other with the naked eye!

#6 Asbytec


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Posted 12 July 2018 - 02:23 AM

Here's my favorite site for predicting seeing. The link is for the Philippines, but the service is in Australia. Browse the site for your location. White is excellent. Lot of white on the current map.


#7 dhaval



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Posted 12 July 2018 - 10:18 AM

The easiest way to do this would be to take an image and use PixInsight (or any other software) to measure FWHM of the stars. That should give you very good indication of what the seeing is like. You can do this after the fact as well - meaning after you've shot through the night. 

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