Assessment of Nightly Seeing

There are seeing monitors out there, basically based on scintillation assessment rather than wavefront assessment (which also exist but I suspect just not at the right price). I'd still think that Mk.I eyeball is a good proxy of the former but not of the latter. If is twinkling too much it is usually the case that there no reason to bother with high resolution. In over 20 years in this hobby I rarely found the assessment wrong. The reciprocal is also true, if it ain't twinkling then it is the case to rush out for a shot. Given the weather in the UK is mostly crappy anyway you get what you get and be happy that you gonna get something at all!

Dave, that is exactly the type of thing that I was looking for, thanks!  I was hoping to spend less than $1000 for such a capability, but from a quick search it looks like most of these types of monitors are well above that.  In any case, you have given me something to think about.  It is nice to know that this capability is out there.

Hey Gary. I've been thinking about this one.
Seeing monitor

It's not cheap but looks cool.

That's an interesting question Gary.  My system out at DSW runs at an EFL of almost 4 m so it's pretty sensitive to seeing conditions.  Just by watching the guide star and the tracking signal, I've gotten pretty good at judging how good my FWHM numbers will turn out.  I also find it interesting to see how my numbers correlate with the numbers reported by the observatory seeing monitor.  Unfortunately, agreement is hit and miss.  Sometimes the observatory monitor reports superb conditions, which out there is typically a bit over one arc-second and I can watch my guide star bouncing all over the place.  Other times, the agreement is closer.  I haven't kept records but my impression is that it's right only about half the time–and it almost always reports better than actual conditions.  To be fair, I believe that sometime earlier this year, they installed a newer seeing monitor that may be performing a bit better.  Regardless, I've almost completely given up on relying on the numbers from the monitor.  The monitor will tell you when things get better or worse, but in my experience, the numbers themselves are typically meaningless.  I wish you luck in finding a monitor and I hope that you experience with it is better than mine; but, don't get your hopes too high.

John

@Tim Hutchison   That does look cool!  My neighbors would probably call the police out on me.  But as cool as it looks, it is a lot of money to pay for a cool looking object.

@John Hayes John, I really appreciate your wise counsel.  As I look more into the cost and practicality aspects of a dedicated seeing setup, it is starting to make my current "setup and see" process seem not so bad, especially if I can't have 90% or so confidence in the results.

Not much to aid Gary but i have some experience with bad seeing, to say the least. First off it's obvious that having a part of your gear somewhat permanently in place would make it faster to set up enough to determine go or no go for the night.  My current set up is a pier with the mount and telescope in place 24-7-365.  I can see while doing a PA in 30 seconds what the night is probably going to be like, all other things like clouds being equal. Also I think for many of us as mentioned above, guiding is our canary in the coal mine.  If my guiding star image is not very good and my graph numbers are weird, I am assured to be disappointed in my images.  I find Astrospheric app to be very accurate for overall prediction with only occasional misses + or- in hourly timing.  Astrospheric is North America only I believe.

Scott

24-7-365.jpg

I've found more success by taking a larger sampling of sources on seeing predictions, as they can definitely vary. In fact, I check 5 different seeing reports (plus 3 additional ones for clouds) to judge the night ahead of time. Occasionally, one or more of them can be very far off, which is why I use so many. However, usually the mean judgment between them all does very, very well. Here they are:

Meteoblue- This doesn't always give results that reflect how my imaging will be, however it contains one of the most important metrics anyways, which is the jet stream speed. Higher speeds (into the red), and it will definitely be worse. Lower speeds, better seeing. Being near mountains, the jet stream is almost always fast, and the seeing almost always terrible.

ClearDarkSky- One of the best, bookmark your location and I say its seeing estimates are good 80% of the time.

Apps:

"Clear Outside"- Great for weather, not heavily-weighted for my seeing predictions though.

"Astrospheric"- Pretty good seeing estimates as well. Discussed above.

"Astro Panel"- Okay predictions for seeing.

Viewing the cleardarksky and astrospheric predictions, coupled with the jet stream information, I can usually know what to expect. I'll say though, it's not an easy science; some of my best seeing was during mediocre forecasts. If you're feeling it, try anyways!

I also think looking at the stars does an excellent job of predicting how well the guider would do from seeing. Every single night I do multiple seeing assessments by rating the sky between 1 and 5 mentally, by looking at it, and I think I could reliably predict my RMS error values on PHD2 just by looking at the stars (only look in the area you're imaging; it can vary widely throughout the sky!).

Also, always image as high in the sky as is possible. Always.

John Hayes:
That's an interesting question Gary.  My system out at DSW runs at an EFL of almost 4 m so it's pretty sensitive to seeing conditions.  Just by watching the guide star and the tracking signal, I've gotten pretty good at judging how good my FWHM numbers will turn out.  I also find it interesting to see how my numbers correlate with the numbers reported by the observatory seeing monitor.  Unfortunately, agreement is hit and miss.  Sometimes the observatory monitor reports superb conditions, which out there is typically a bit over one arc-second and I can watch my guide star bouncing all over the place.  Other times, the agreement is closer.  I haven't kept records but my impression is that it's right only about half the time--and it almost always reports better than actual conditions.  To be fair, I believe that sometime earlier this year, they installed a newer seeing monitor that may be performing a bit better.  Regardless, I've almost completely given up on relying on the numbers from the monitor.  The monitor will tell you when things get better or worse, but in my experience, the numbers themselves are typically meaningless.  I wish you luck in finding a monitor and I hope that you experience with it is better than mine; but, don't get your hopes too high.

John

John,

Does DSW also have a transparency meter?  We have a both the SBIG pole star seeing monitor and the Alcor Zenith seeing monitor at SRO.  But I found the transparency meter to be more correlated with getting good data.

I do find the seeing monitors to be a good indicator of my FWHMs numbers but If the seeing is good, and the transparency dips below the norm, I get soft stars.

Kevin

Kevin Morefield:

John Hayes:
That's an interesting question Gary.  My system out at DSW runs at an EFL of almost 4 m so it's pretty sensitive to seeing conditions.  Just by watching the guide star and the tracking signal, I've gotten pretty good at judging how good my FWHM numbers will turn out.  I also find it interesting to see how my numbers correlate with the numbers reported by the observatory seeing monitor.  Unfortunately, agreement is hit and miss.  Sometimes the observatory monitor reports superb conditions, which out there is typically a bit over one arc-second and I can watch my guide star bouncing all over the place.  Other times, the agreement is closer.  I haven't kept records but my impression is that it's right only about half the time--and it almost always reports better than actual conditions.  To be fair, I believe that sometime earlier this year, they installed a newer seeing monitor that may be performing a bit better.  Regardless, I've almost completely given up on relying on the numbers from the monitor.  The monitor will tell you when things get better or worse, but in my experience, the numbers themselves are typically meaningless.  I wish you luck in finding a monitor and I hope that you experience with it is better than mine; but, don't get your hopes too high.

John

John,

Does DSW also have a transparency meter?  We have a both the SBIG pole star seeing monitor and the Alcor Zenith seeing monitor at SRO.  But I found the transparency meter to be more correlated with getting good data.

I do find the seeing monitors to be a good indicator of my FWHMs numbers but If the seeing is good, and the transparency dips below the norm, I get soft stars.

Kevin

Hi Kevin,
DSW does not have a transparency monitor.  I’ve given up asking, but for a long time, I’ve been advocating for a much better sky cameras so that I can assess both transparency and cloud locations.  The northern NM sky is rarely totally clear, calm, and transparent.  (In the winter, it’s definitely better than central Oregon, but central Oregon totally wins in the summer...except for the shorter nights!)  I’ve considered attaching a wide field, astro-camera/finder-scope to my scope so that I can use it to have my own wide field view of the region of the sky that I’m pointed at.  I may experiment with that idea on the 20” scope—although it’s destined for a location that generally has much better sky conditions.

It’s interesting that you see soft stars when the sky  transparently dips.  I don’t have hard numbers but I often notice that it’s not uncommon to have very little turbulence when the sky is a bit hazy.  The haze often generates gradients, which overwhelms the advantage of tight stars that I usually get under those conditions.

John