Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Reliable resource to forecast seeing condition

  • Please log in to reply
8 replies to this topic

#1 controlpower29

controlpower29

    Sputnik

  • -----
  • topic starter
  • Posts: 33
  • Joined: 21 Sep 2020
  • Loc: Chicago, IL, USA

Posted 21 September 2020 - 11:29 PM

Today I looked at https://www.meteoblu...orsports/seeing before doing my Jupiter and Saturn imaging.

 

When I looked at the website at about 6pm, it showed this picture.

seeing1.jpg

It looks at about 9pm, the seeing will be around 0.65 which is pretty good for Chicago.

 

However, during the imaging, I felt the image quality was not as good as I expected.

When I went back home and checked the website again at 10:30pm, the forecast became the following.

seeing2.jpg

The seeing condition was actually 1.03 during my imaging 9-10pm.

 

It seems that the www.meteoblue.com is not a reliable resource to forecast seeing. What website is more reliable?

 

BTW, I felt very frustrated that I waited about a month in Chicago, but still cannot get a good seeing below 1.00. Is it possible to have good planet image when the seeing is a little bit above 1.00?

Attached Thumbnails

  • seeing1.jpg
  • seeing2.jpg


#2 Napp

Napp

    Mercury-Atlas

  • *****
  • Posts: 2,562
  • Joined: 26 Jul 2015
  • Loc: Florida, USA

Posted 21 September 2020 - 11:50 PM

I’m not sure there is a reliable site for forecasting seeing - at least not for my area.  Tony Flanders posted about using Environment Canada seeing projection animations to get a better idea of what seeing conditions will be in his area.  I am going to try them.

 

https://weather.gc.c...o/seeing_e.html



#3 Stricnine

Stricnine

    Messenger

  • -----
  • Posts: 408
  • Joined: 24 Sep 2018
  • Loc: DFW Area, TX

Posted 21 September 2020 - 11:58 PM

Today I looked at https://www.meteoblu...orsports/seeing before doing my Jupiter and Saturn imaging.

 

When I looked at the website at about 6pm, it showed this picture.

 

It looks at about 9pm, the seeing will be around 0.65 which is pretty good for Chicago.

 

However, during the imaging, I felt the image quality was not as good as I expected.

When I went back home and checked the website again at 10:30pm, the forecast became the following.

 

The seeing condition was actually 1.03 during my imaging 9-10pm.

 

It seems that the www.meteoblue.com is not a reliable resource to forecast seeing. What website is more reliable?

 

BTW, I felt very frustrated that I waited about a month in Chicago, but still cannot get a good seeing below 1.00. Is it possible to have good planet image when the seeing is a little bit above 1.00?

Every weather forecast I've looked at over the past 10-15 years seem to change, sometimes dramatically, and can't seem to actually predict what they will be even 30-45 minutes from present.  Some, such as what ever service my phone uses, can't even tell you if the sky is currently clear or cloudy at night, LOL.


  • Kokatha man, RedLionNJ, TerryWood and 1 other like this

#4 KpS

KpS

    Mariner 2

  • -----
  • Posts: 254
  • Joined: 07 Nov 2009
  • Loc: Prague, Czechia

Posted 22 September 2020 - 05:44 AM

controlpower29, the numbers you show from the Meteoblue forecast are extremely favorable. Even if it were correct, it should be noted that the prediction always applies to the zenith. As the distance from the zenith increases, seeing worsens. E.g. twenty degrees above the horizon, seeing is about twice as bad as at the zenith. And mostly even worse.



#5 dhammy

dhammy

    Apollo

  • -----
  • Posts: 1,024
  • Joined: 20 Jul 2015
  • Loc: Puerto Rico

Posted 22 September 2020 - 04:06 PM

Honestly, the best way I have found is how much the stars are twinkling in the area of the sky you want to image. I basically use the forecast to give me an idea if it is going to be cloudy or not - then I go out and look at a star near the planet I'm going to image. The more turbulence the atmosphere the more it twinkles - if you don't see the star twinkling then it's typically good seeing. 

 

That method has held up for me. 


Edited by dhammy, 22 September 2020 - 04:06 PM.

  • MikiSJ, TerryWood, The_8_Bit_Zombie and 2 others like this

#6 RedLionNJ

RedLionNJ

    Skylab

  • *****
  • Posts: 4,081
  • Joined: 29 Dec 2009
  • Loc: Red Lion, NJ, USA

Posted 22 September 2020 - 04:22 PM

The seeing numbers from such services as MeteoBlue, Astropheric, CSC, etc. are about as good as the paper they are (not) printed on.  The developers all made well-meaning efforts, but the data and algorithms simply don't exist to forecast seeing from any point on our planet's surface.

 

And even if there was such a prediction with quality, where in the sky would it be referring to? The only almost-meaningful reference CAN be the zenith.

 

CSC, for example (the one I know most intimately) is driven by data up to an altitude of 4,000 feet. It has no concept of anything above that (i.e. most of the atmosphere). The jet stream could be roaring overhead and CSC could (and does!) still predict good or better seeing. In all eventuality, MeteoBlue is very likely no better.

 

There are an incredible number of factors affecting seeing, not just the gross-scale weather forecasts. Target direction and elevation are factors. More local conditions (imaging over nearby highway, or a pool, for example) are factors. The air currents around the scope itself are a factor. The mirror temperature vs the air inside the OTA is a factor. "Seeing" is a beast which is tough to tame. All it needs is any one of those potential factors to be negative and your seeing is terrible. It takes ALL of them to work together in a positive manner for your seeing to be good.


  • Kiwi Paul likes this

#7 MikiSJ

MikiSJ

    Apollo

  • *****
  • Posts: 1,179
  • Joined: 24 Feb 2006
  • Loc: San Jose, CA

Posted 22 September 2020 - 04:47 PM

I read somewhere, about 20 years ago that NOAA could compute an accurate forecast, but it would be about 5 days late.

 

Now, I suspect with a massive exascale era computing at their beck and call, NOAA might be able to get an accurate down to the what is currently happening. This would be as accurate as simply standing outside and wetting a finger to find out where the wind is coming from.

 

The best we can hope for is for a weathercaster to NOT tell his audience that it is a beautiful day in San Francisco when everyone in San Francisco knew that day that it was a blustery rainy day. The weathercaster was immediately fired. 

 

Walk aside, look up and if you see stars and they aren't twinkling a lot - uncover your telescope and enjoy the view.



#8 The_8_Bit_Zombie

The_8_Bit_Zombie

    Mariner 2

  • -----
  • Posts: 282
  • Joined: 29 Apr 2016
  • Loc: Southern California

Posted 22 September 2020 - 07:32 PM

I use the seeing predictions as a rough guide, as they're not really good for much beyond that in my experience. Atmospheric seeing can be very local, and conditions can vary wildly even a few miles apart. It's simply too complex of a variable for websites to predict accurately.

 

I second dhammy's method. Whenever the stars are barely twinkling or slowly twinkling (looking at the bright ones between 30-60 degrees), I tend to have excellent seeing. However I've also had good seeing on nights where the stars were twinkling like mad, so really the only 100% effective solution is to aim at a planet and look. lol.gif


  • Kiwi Paul likes this

#9 controlpower29

controlpower29

    Sputnik

  • -----
  • topic starter
  • Posts: 33
  • Joined: 21 Sep 2020
  • Loc: Chicago, IL, USA

Posted 07 October 2020 - 06:19 PM

Thank you guys. Although I did not get an expected answer, I learned why it is hard to forecast the seeing. I will rely on my real time observation and only take the forecast as a reference.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics