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

Effects of Good/Bad Seeing and Meteoblue Failure

astrophotography cassegrain ccd Celestron dso imaging LP SCT
  • Please log in to reply
22 replies to this topic

#1 BenKolt

BenKolt

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1709
  • Joined: 13 Mar 2013

Posted 19 March 2019 - 09:11 PM

Greetings!

 

I thought my fellow forum dwellers might appreciate what has been happening to me these past several nights.  I've had a string of rare clear nights (unfortunately just before this here upcoming Full Worm Super Moon), and wanted to acquire frames of the following, rarely imaged galaxy beauty.  Meteoblue informed me that I could expect exceptional sub-arcsecond seeing conditions such as what the website says I am to expect this very night:

 

Meteoblue.jpg

 

The clouds parted for me shortly after midnight the morning of Sunday, March 17th, and I anticipated the rest of that night would be turbulent, so I took my time getting everything polar aligned, guiding calibrated, camera oriented, autofocus set for LRGB filters, etc.  I then decided to stay up even later and take my flats, again assuming that night would be a bit of a loss anyway in anticipation of the clear nights and exceptional seeing to come.  When finished, I went ahead and started taking frames until dawn and went to bed.  In the morning, I was pleased to see 29 very nice L frames of 180s, the stacking of which is shown below.  This was from my C11 + 0.7x reducer + QSI 683 camera.  I confidently awaited several more nights of exceptional seeing.

 

But for the next two nights the seeing was absolutely crummy, and that's my anticipation for tonight as well!  Meteoblue has failed me!  It has let me down.  I am downcast.  I am dejected.  I am low.  Next to the unexpected nice image is the result of 29 L frames at 180s from the past two nights (my absolute "best" of the bunch).  Horrible.  Click on the image to see it expanded so you can better compare the resolution of the L (the good night) and R (the bad nights).

 

M51_L_087-01-02-03_1x1_0180s_20190317_-25C.v001E_Mosaic-1.jpg

 

Processing consisted of calibration, stacking, cropping, linear gradient removal, auto stretching, all in PI.  To give you some statistics (prior to stretching), the standard deviation of the L image comes out to be 202 ADU = 94.5 e-, the R 434 ADU = 203 e-.  A measure of the largest 5 stars in each image comes out to an average size of L 2", R 3.6", almost a factor of two difference!

 

After the fact, I checked in with the Clear Sky Chart website, and this is what it has for tonight:

 

ClearSkyChart.jpg

 

That pale blue color under "Seeing" denotes "Poor 2/5" conditions.  This is certainly much more consistent with what I am actually experiencing.

 

In hindsight, of course, I wish I had known that this would happen.  I would have skipped the flats that first night, imaged only the L filter as long as possible the rest of the night and then taken the 2x2 binned color frames during the crummy seeing.  You can rest assured that I will be much more careful with these predictions in the future and will plan accordingly.

 

I hope to have a nice processed final version of this mystery galaxy soon, likely not using any of the L data from the following nights.  This is going to be a case where I'll have much more color data than luminance data.

 

Perhaps my unfortunate experience can be a cautionary tale to others to not rely on just one forecast model and plan ahead better.

 

Take care, and may you have not only clear but still skies as well!

 

Best Regards,

Ben

 

 

 

 


  • rockstarbill, bobzeq25 and ks__observer like this

#2 bobzeq25

bobzeq25

    Hubble

  • *****
  • Posts: 15200
  • Joined: 27 Oct 2014

Posted 19 March 2019 - 09:42 PM

I find meteoblue's "seeing index(s)" more reliable than the number.  I use that site, ClearDarkSkies, and Astrospheric.  When they all agree it's pretty reliable.


  • roofkid and Redbetter like this

#3 BenKolt

BenKolt

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1709
  • Joined: 13 Mar 2013

Posted 19 March 2019 - 10:26 PM

I find meteoblue's "seeing index(s)" more reliable than the number.  I use that site, ClearDarkSkies, and Astrospheric.  When they all agree it's pretty reliable.

I am aware of Astropheric but have not gotten into using it yet.  I'll take a closer look now.

 

I am happy to report that so far tonight my actual seeing conditions, as best observed through my guiding performance, is much better than the last couple of nights.  If seeing continues to look better, I'm going to stop acquiring color frames and devote my time just to luminance to make up for the lost time of Nights 2 and 3.  Perhaps the L data from tonight (Night 4) can be combined with that from Night 1.  However, the night is still young, and things may change yet, so you can be sure I'll be monitoring it closely!



#4 Ron359

Ron359

    Apollo

  • *****
  • Posts: 1085
  • Joined: 21 Apr 2008
  • Loc: -105 +39

Posted 19 March 2019 - 10:44 PM

"Meteoblue has failed me!  It has let me down.  I am downcast.  I am dejected.  I am low."

 

Ask for your money back...and consult a therapist or priest.    



#5 Redbetter

Redbetter

    Fly Me to the Moon

  • *****
  • Posts: 7157
  • Joined: 16 Feb 2016
  • Loc: Central Valley, CA

Posted 19 March 2019 - 11:25 PM

If the previous Meteoblue seeing forecast was anything like the one you displayed above, then you simply misread it.  It shows very poor seeing under index 2 and mediocre under index 1.  I don't know why one would expect anything other than crummy seeing with that sort of forecast.  Sounds like Meteoblue nailed it, but you didn't have a feel for how to interpret what was presented.  The arc second rating is not one to put much stock in by itself anyway, and I usually find Clear Sky Chart even less reliable in this regard. 

 

When looking at several different types of seeing index (as Meteoblue displays...3 of them, or possibly even 4 if one considers jet stream speed independently) one should assume the seeing will be no better than the worst of them.  Seeing indices on average overpredict the frequency of good seeing by an order of magnitude from what I have experienced locally. 



#6 BenKolt

BenKolt

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1709
  • Joined: 13 Mar 2013

Posted 19 March 2019 - 11:54 PM

If the previous Meteoblue seeing forecast was anything like the one you displayed above, then you simply misread it.  It shows very poor seeing under index 2 and mediocre under index 1.  I don't know why one would expect anything other than crummy seeing with that sort of forecast.  Sounds like Meteoblue nailed it, but you didn't have a feel for how to interpret what was presented.  The arc second rating is not one to put much stock in by itself anyway, and I usually find Clear Sky Chart even less reliable in this regard. 

 

When looking at several different types of seeing index (as Meteoblue displays...3 of them, or possibly even 4 if one considers jet stream speed independently) one should assume the seeing will be no better than the worst of them.  Seeing indices on average overpredict the frequency of good seeing by an order of magnitude from what I have experienced locally. 

Thanks for your input.

 

If one only made a cursory glance of just the seeing conditions in the arc sec. column (as I unfortunately did), one would indeed expect great seeing.  That's obviously my mistake and misinterpretation as you have pointed out.  You may now consider me to be more enlightened.  (And, by the way, that explains how somebody could have expected good seeing conditions, so now you do know.)

 

I will note, however, that Meteoblue is showing quite a bit of variability in its forecast for tonight.  Here's the latest prediction:

 

Meteoblue2.jpg

 

Compare this to the earlier one.  So far my guiding is improved over the last couple of nights, and now according to Meteoblue I ought to expect things to get even better with all columns including Index 2 after midnight.  It is possible this kind of variability was present when I was planning for my imaging this week.  For tonight at least, at any given moment I wouldn't say that Meteoblue "nails it".  But now I'm really hoping it's correct, of course, since things are looking better in its forecast!  And Clear Sky Chart has also updated for the seeing to improve after midnight, so maybe my luck has indeed changed.

 

Ben



#7 BenKolt

BenKolt

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1709
  • Joined: 13 Mar 2013

Posted 19 March 2019 - 11:58 PM

"Meteoblue has failed me!  It has let me down.  I am downcast.  I am dejected.  I am low."

 

Ask for your money back...and consult a therapist or priest.    

Actually, I'd rather be compensated with clear skies and good seeing conditions during the next New Moon, thank you!



#8 jhayes_tucson

jhayes_tucson

    Fly Me to the Moon

  • *****
  • Posts: 6710
  • Joined: 26 Aug 2012
  • Loc: Bend, OR

Posted 20 March 2019 - 12:27 AM

I don't care what site I've tired.  I've learned to take all of the seeing predictions with a grain of salt.  I've seen predictions for 5/5 conditions turn out to actually be 3"-4" and predictions for 2/5 conditions turn into 1.3" - 1.5" images.  It's exciting when you get a prediction for excellent conditions but you won't know what you actually get until you try it.  Worse, you can lose a lot of good imaging time if you believe this stuff and set up late or not at all when the conditions turn out to be much better than predicted.  I'm' sure that the accuracy is somewhat location dependent.  It seemed like the predictions in central Oregon were a slight bit better than in northern New Mexico.  Sometimes they get it right but I don't think that anyone's batting average is very good--no matter where you are.  Now, I just look for clear skies, high transparency, reasonable humidity, and low wind in the predictions--and even those can sometimes turn out to be screwy.

 

John


  • bobzeq25, roofkid and moab360 like this

#9 Jon Rista

Jon Rista

    ISS

  • *****
  • Posts: 22740
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 20 March 2019 - 12:46 AM

Thanks for your input.

 

If one only made a cursory glance of just the seeing conditions in the arc sec. column (as I unfortunately did), one would indeed expect great seeing.  That's obviously my mistake and misinterpretation as you have pointed out.  You may now consider me to be more enlightened.  (And, by the way, that explains how somebody could have expected good seeing conditions, so now you do know.)

 

I will note, however, that Meteoblue is showing quite a bit of variability in its forecast for tonight.  Here's the latest prediction:

 

attachicon.gif Meteoblue2.jpg

 

Compare this to the earlier one.  So far my guiding is improved over the last couple of nights, and now according to Meteoblue I ought to expect things to get even better with all columns including Index 2 after midnight.  It is possible this kind of variability was present when I was planning for my imaging this week.  For tonight at least, at any given moment I wouldn't say that Meteoblue "nails it".  But now I'm really hoping it's correct, of course, since things are looking better in its forecast!  And Clear Sky Chart has also updated for the seeing to improve after midnight, so maybe my luck has indeed changed.

 

Ben

The seeing indexes from your original post indicated pretty bad seeing. The orange color is bad. Not the worst possible, but bad. It seems MetoBlue predicted your seeing fairly well that night.

 

The arc sec column is only a measure of jetstream scintillation, and is not the only factor in seeing. There are other turbulence layers in the troposphere as well as ground layer effects that can have a large impact on seeing as well. Assuming you have no ground layer effects (which are easy enough to judge just by looking at nearby city lights...if THEY scintillate like the stars, then your ground layer sucks! tongue2.gif), then you only need to worry about atmospheric turbulence. When the two seeing indexes are both 5, and you have no bad layers, then you should mostly be affected by jetstream scintillation, and then and only then would the arc sec reading really be more of a mostly direct measure of seeing.


Edited by Jon Rista, 20 March 2019 - 12:47 AM.

  • BenKolt and bobzeq25 like this

#10 BenKolt

BenKolt

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1709
  • Joined: 13 Mar 2013

Posted 20 March 2019 - 12:53 AM

I don't care what site I've tired.  I've learned to take all of the seeing predictions with a grain of salt.  I've seen predictions for 5/5 conditions turn out to actually be 3"-4" and predictions for 2/5 conditions turn into 1.3" - 1.5" images.  It's exciting when you get a prediction for excellent conditions but you won't know what you actually get until you try it.  Worse, you can lose a lot of good imaging time if you believe this stuff and set up late or not at all when the conditions turn out to be much better than predicted.  I'm' sure that the accuracy is somewhat location dependent.  It seemed like the predictions in central Oregon were a slight bit better than in northern New Mexico.  Sometimes they get it right but I don't think that anyone's batting average is very good--no matter where you are.  Now, I just look for clear skies, high transparency, reasonable humidity, and low wind in the predictions--and even those can sometimes turn out to be screwy.

 

John

Yes, I'm sure the accuracy of the predictions is very much location dependent as well as seasonally dependent.  I've found that my area of Puget Sound tends to be more steady and predictable during the brief dry and clear weeks of summer.  But this time of year can vary wildly.

 

In actuality I try to image just about any clear night possible, particularly this time of year, since they can be so few and far between.  I'm just kicking myself for not doing enough due diligence to gather multiple forecasts as well as to assume I was going to have great nights ahead.  I would have planned things differently and taken more advantage of that one good night.  (I'm still holding out for later tonight, however.)

 

You are absolutely correct that in the end the most important thing to do is to measure or observe it yourself in real time and make decisions accordingly

 

Ben



#11 BenKolt

BenKolt

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1709
  • Joined: 13 Mar 2013

Posted 20 March 2019 - 12:57 AM

The seeing indexes from your original post indicated pretty bad seeing. The orange color is bad. Not the worst possible, but bad. It seems MetoBlue predicted your seeing fairly well that night.

 

The arc sec column is only a measure of jetstream scintillation, and is not the only factor in seeing. There are other turbulence layers in the troposphere as well as ground layer effects that can have a large impact on seeing as well. Assuming you have no ground layer effects (which are easy enough to judge just by looking at nearby city lights...if THEY scintillate like the stars, then your ground layer sucks! tongue2.gif), then you only need to worry about atmospheric turbulence. When the two seeing indexes are both 5, and you have no bad layers, then you should mostly be affected by jetstream scintillation, and then and only then would the arc sec reading really be more of a mostly direct measure of seeing.

Jon:

 

Both of my posts from Meteoblue are for tonight, taken less than two hours apart.  The conditions are changing as are the predictor models.  I don't recall now what was predicted for the past two nights at the time I looked, but if they underwent this kind of variability, then it might be an indication of the volatility of my conditions, particularly for this time of year.

 

Thank you for your explanation of those data columns!  That's very helpful.

 

Ben



#12 GA-HAMAL

GA-HAMAL

    Messenger

  • -----
  • Posts: 422
  • Joined: 18 Aug 2014
  • Loc: Poland

Posted 20 March 2019 - 04:24 AM

I am never disappointed with the Meteoblue website.
Whenever he announces 0.9, I have 5.9
Whenever he announces 4.0, I have 0.8

Whenever he announces 1.9, I have 1.9

 

biggrin.png

It should be remembered that local conditions affect the forecasts, they must be recognized and taken into account smile.png


Edited by GA-HAMAL, 20 March 2019 - 05:32 AM.

  • jhayes_tucson, BenKolt and ks__observer like this

#13 BenKolt

BenKolt

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1709
  • Joined: 13 Mar 2013

Posted 20 March 2019 - 11:41 AM

Thank you again for everybody's helpful comments.

 

Well, in the end the seeing turned out to again be poor last night as I had expected earlier in the evening.  Later on, several of the websites switched their predictions to say that conditions would improve, however that prediction had changed back to being lousy again by the time I went to bed.

 

Understand that I'm really not upset at Meteoblue and the other forecasting sites - that was just me trying to add some humor.  It is my observation that weather forecasting in general has improved quite a bit over the years.  Prediction of seeing conditions is very complicated, and, as many have posted here, very much dependent upon local conditions.  It's actually a wonder they do as well as they do.

 

I'm kicking myself for (1) not gathering all the available information and taking just a little bit more time to understand it and (2) not optimizing my time more wisely regarding which filters to use which nights, to bin or not to bin, etc.  When the next string of clear nights come my way I will plan it out more carefully.  Frankly, with the moon nearly full it was a bad time anyway for wide band imaging, but I was inaugurating some new equipment and certainly couldn't say when I'll get to image next.

 

In the end I really only have one half of a night's worth of good luminance data and three nights of lousy data.  I am hopeful, however, that my binned color data will be more useful from all the nights.  My luminance image will definitely be weighted heavily by Night 1's data, but maybe I can still benefit from stacking the best frames from the other nights to bring down SNR some more.  I will definitely need to experiment with how best to combine the frames.

 

Best Regards,

Ben



#14 Jon Rista

Jon Rista

    ISS

  • *****
  • Posts: 22740
  • Joined: 10 Jan 2014
  • Loc: Colorado

Posted 20 March 2019 - 11:48 AM

Jon:

 

Both of my posts from Meteoblue are for tonight, taken less than two hours apart.  The conditions are changing as are the predictor models.  I don't recall now what was predicted for the past two nights at the time I looked, but if they underwent this kind of variability, then it might be an indication of the volatility of my conditions, particularly for this time of year.

 

Thank you for your explanation of those data columns!  That's very helpful.

 

Ben

The jetstream seems to get whipped around a lot these days. I also use Astrospheric. It is a weather site dedicated to serving astrophotographers, built by an astrophotographer. It is really good, and you should give it a try.

 

I use his jetstream overlay on the map a lot. I find that the jetstream is very unpredictable, and little eddies and such can spin off and plow over my skies in just a matter of hours. So seeing can go from good to horrible to good in 3-4 hours. 

 

The big factor that MeteoBlue does not account for at all is the ground level stuff. I have resorted to always checking the city lights out my upstairs windows each night. City lights can flicker just like stars do when ground level conditions are bad. Some nights, city lights 10-15 miles or more away are rock solid steady, other nights the whole city boils. Also, consider your direct local environment. Homes around you, if there are any, can exhaust energy on a dime, then suddenly stop on a dime. Furnaces, for example, usually have a direct exhaust pipe to the roof, and when the furnace is running that can create a lot of local turbulence over said house. If you are imaging over that house...well....that is another source of seeing. And that source can start, and stop, and start, and stop, on and on throughout the night... MeteoBlue couldn't hope to predict that. 


  • ginjaninjaa likes this

#15 Jeff2011

Jeff2011

    Gemini

  • *****
  • Posts: 3486
  • Joined: 01 Jan 2013
  • Loc: Sugar Land, TX

Posted 20 March 2019 - 12:51 PM

That is something else that is not taken into account when getting into this hobby.  That is becoming an amateur meteorologist as well.


  • moab360 likes this

#16 moab360

moab360

    Vendor / Developer - Astrospheric

  • -----
  • Vendors
  • Posts: 191
  • Joined: 20 Feb 2016
  • Loc: Seattle

Posted 20 March 2019 - 02:17 PM

I don't care what site I've tired.  I've learned to take all of the seeing predictions with a grain of salt.  I've seen predictions for 5/5 conditions turn out to actually be 3"-4" and predictions for 2/5 conditions turn into 1.3" - 1.5" images.  It's exciting when you get a prediction for excellent conditions but you won't know what you actually get until you try it.  Worse, you can lose a lot of good imaging time if you believe this stuff and set up late or not at all when the conditions turn out to be much better than predicted.  I'm' sure that the accuracy is somewhat location dependent.  It seemed like the predictions in central Oregon were a slight bit better than in northern New Mexico.  Sometimes they get it right but I don't think that anyone's batting average is very good--no matter where you are.  Now, I just look for clear skies, high transparency, reasonable humidity, and low wind in the predictions--and even those can sometimes turn out to be screwy.

 

John

 

As the creator of Astrospheric and someone deeply involved with working on seeing models, I think it's worth echoing John's point above (emphisis is mine).

 

The general physics behind the seeing modes has been well known since the 50's - wind shear and large temperature gradients in the atmosphere above will generally lead to bad seeing.  These models are validated with high precision near professional observatories where weather balloons are released  to measure these variables at high resolution. The problems come when we apply these model to numerically forecasted data - 1) we loose a lot of resolutions and 2) any innacuracy in the forecast compound.  The end result from these models applied to forecast data should be viewed as a  high level measurement of atmospheric stability.  Furthermore, most seeing effect occur within the first 100 meters of atmosphere above you at resolutions (currently) imposible to forecast, making where you setup nearly as important as the atmosphere stability higher above.

 

This isn't to say  seeing forecasts based on weather data are bad, some are quite good, but understanding their limits can be helpful!


  • Ron359, BenKolt, 44maurer and 2 others like this

#17 BenKolt

BenKolt

    Surveyor 1

  • -----
  • topic starter
  • Posts: 1709
  • Joined: 13 Mar 2013

Posted 20 March 2019 - 02:57 PM

As the creator of Astrospheric and someone deeply involved with working on seeing models, I think it's worth echoing John's point above (emphisis is mine).

 

The general physics behind the seeing modes has been well known since the 50's - wind shear and large temperature gradients in the atmosphere above will generally lead to bad seeing.  These models are validated with high precision near professional observatories where weather balloons are released  to measure these variables at high resolution. The problems come when we apply these model to numerically forecasted data - 1) we loose a lot of resolutions and 2) any innacuracy in the forecast compound.  The end result from these models applied to forecast data should be viewed as a  high level measurement of atmospheric stability.  Furthermore, most seeing effect occur within the first 100 meters of atmosphere above you at resolutions (currently) imposible to forecast, making where you setup nearly as important as the atmosphere stability higher above.

 

This isn't to say  seeing forecasts based on weather data are bad, some are quite good, but understanding their limits can be helpful!

Dan:

 

Thank you for chiming in here, and thank you even more for your Astrospheric website.  I've only recently started looking at it, and much more so over the past several days.  Thanks for your insight on this.  (And I do understand, for example, that the models don't currently include my neighbor's chimney!)

 

Best Regards,

Ben


  • moab360 likes this

#18 44maurer

44maurer

    Mariner 2

  • *****
  • Posts: 248
  • Joined: 12 Jun 2016
  • Loc: Los Angeles, CA

Posted 20 March 2019 - 04:28 PM

As the creator of Astrospheric and someone deeply involved with working on seeing models, I think it's worth echoing John's point above (emphisis is mine).
 
The general physics behind the seeing modes has been well known since the 50's - wind shear and large temperature gradients in the atmosphere above will generally lead to bad seeing.  These models are validated with high precision near professional observatories where weather balloons are released  to measure these variables at high resolution. The problems come when we apply these model to numerically forecasted data - 1) we loose a lot of resolutions and 2) any innacuracy in the forecast compound.  The end result from these models applied to forecast data should be viewed as a  high level measurement of atmospheric stability.  Furthermore, most seeing effect occur within the first 100 meters of atmosphere above you at resolutions (currently) imposible to forecast, making where you setup nearly as important as the atmosphere stability higher above.
 
This isn't to say  seeing forecasts based on weather data are bad, some are quite good, but understanding their limits can be helpful!
[/quote]


thank you 

bow.gif bow.gif bow.gif
[/quote]


Edited by 44maurer, 20 March 2019 - 04:30 PM.

  • moab360 likes this

#19 james7ca

james7ca

    Fly Me to the Moon

  • *****
  • Posts: 6591
  • Joined: 21 May 2011
  • Loc: San Diego, CA

Posted 22 March 2019 - 01:27 AM

IMO, seeing conditions are FAR too local to be predicted with very much reliability. For example, you know that hill or stand or tall trees that may be just down the block and a little upwind from your observing location? Those can affect you seeing conditions (usually in a bad way). Similarly for buildings, large areas of pavement or concrete or any other man-made structure.

 

I've also noted that none of the seeing prediction sites seem to take into account the Santa Ana wind conditions that we often have here in southern California. Generally speaking with a Santa Ana condition (even a very weak one) the seeing conditions will vary from poor to absolutely atrocious, no matter where the jet steam is or what the prediction sites say.

 

You really need to understand your local conditions, so in my case if the humidity is fairly low (no dew), the skies are clear, and the winds are out of the northeast or east then you can almost bet that the seeing conditions will be poor (because you are probably under a Santa Ana condition). Unfortunately, since I live near to the coast in southern California most of the really clear nights that we have here are under Santa Ana conditions. Otherwise (and being near to the ocean), the night sky will probably be completely overcast from the ocean's marine layer, which can result in great seeing if you are in the mountains and thus above the low clouds (think mount Wilson or Palomar).


Edited by james7ca, 22 March 2019 - 01:55 AM.


#20 scopenitout

scopenitout

    Surveyor 1

  • -----
  • Posts: 1651
  • Joined: 24 Aug 2013
  • Loc: Mt. Belzoni

Posted 22 March 2019 - 11:41 AM

And don't forget those of us who image in a neighborhood of houses with heat plumes billowing from each and every one. Even a great seeing prediction can be seriously degraded by that.

#21 rgsalinger

rgsalinger

    Skylab

  • *****
  • Moderators
  • Posts: 4342
  • Joined: 19 Feb 2007
  • Loc: Carlsbad Ca

Posted 22 March 2019 - 12:33 PM

If you use the same site over and over again you may find that certain things are true. I've been imaging at my club's dark sky site now for nine years. The most important thing that I've found is that the wind predictions on the clear sky chart, noaa, weather underground and meteoblue are all consistently too high. The second thing that I've found is that the wind direction determines if the wind will die down or not. North winds just keep blowing through the night. East winds will always die down.

 

I ignore the seeing charts because they are just not accurate. That's why I'm in love with automation. If the sky is clear, then I shoot. I use CCDInspector to see what I got the next morning or in the middle of the night if I happen to wake up. That's also why I bought a cot to sleep on and bring out a good book when imaging at the observatory. 

 

Rgrds-Ross



#22 Jeff2011

Jeff2011

    Gemini

  • *****
  • Posts: 3486
  • Joined: 01 Jan 2013
  • Loc: Sugar Land, TX

Posted 22 March 2019 - 12:44 PM

That's also why I bought a cot to sleep on and bring out a good book when imaging at the observatory. 

 

Rgrds-Ross

 I have done the cot thing before when I imaged at the Houston club's dark site. Instead of a book though, I bring my Dob with me to do some visual observing while my imaging rig collects photons.



#23 Adlanphere

Adlanphere

    Lift Off

  • -----
  • Posts: 23
  • Joined: 15 Jul 2017
  • Loc: Lafayette, CA

Posted 22 March 2019 - 12:52 PM

My seeing was so unexpectedly bad last night that I packed it in early ... and a completely unforecasted rain storm blew through a couple hours later.  So, basically, take it all with a grain of salt. 




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





Also tagged with one or more of these keywords: astrophotography, cassegrain, ccd, Celestron, dso, imaging, LP, SCT



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics