49 replies to this topic

[LDW47]

The question was whether there was a quick way to judge seeing; I hope the original poster does not get bored by the technical and philosophical discussions that grew out of the answers ...  :-)

 

Clear sky ...

Not uncommon, happens every time and the OP leaves the scene, lol.

[Redbetter]

I have always been curious what other locals rate their skies at. What do you consider poor or average seeing for the Central Valley?

 

Whether it's my actual seeing ratings that are off, or if I do have better/poorer skies from what others believe makes no difference to me as long as I'm satisfied with the end results. IMO, I'm much more affected by poor transparency.

 

 

My backyard seeing conditions haven't changed much over the last 25 years using the same APO, & same EP magnifications I used in the early 2000's. When I compare observing from skies others astronomers consider premium (seeing wise), my location produces good results IMO. When I log seeing values as mediocre, I usually word it like "I'm having short periods of very stable seeing conditions." I also consider good as better than mediocre.

 

Perhaps it's lower expectations on my part? I do find my 4" refractor isn't generally able to be pushed past 240x on the larger planets and double stars, so would that be considered poor seeing conditions? I'm usually more than satisfied running my NP101 at 154x and on a good night of seeing, maybe up to 215x.

 

In most cases, how unstable the stars look visually, gives me an idea the seeing might be substandard, average or possibly above average. The OP is asking how to rate the sky w/o a scope or binoculars, so the twinkling stars method works but doesn't determine whether I set up or not.

Without respect to aperture (since I use a range of apertures suited to where I find the optimum during a session):

Backyard seeing here on the valley floor is often ~150x level for planetary, that is poor seeing, and 100x level seeing is not uncommon.  A night that supports about 225x decently is mediocre and that is fairly common.  I prefer something in the 275x range to start getting the sort of planetary detail I am after, but that is rarely well supported here.  Nights that will allow me 350x or so are uncommon--and have become far less so in recent years--corresponding with replacement of orchards to the S and W with new subdivisions.  It has been years since I had 400x+ planetary night in the valley. The 350x+ nights are where things start to get really interesting, especially when I can bump 400+.

 

Where one finds the optimum for planetary with a given scope in excellent seeing is a personal thing, so we each have our own factor.  However, when seeing is a big limitation I have noticed that folks tend to run about the same level.   Club nights when I'm finding 150x about all I can stand with the 8, 10, or 20", I discover that everyone else is stuck around the same magnification in their 8" and larger scopes.  On better nights folks will be pushing more.

 

On nights of good/very good seeing I tend to find optimal for planetary/lunar is around:  120x with the AT60ED (sometimes 144x for a bit more scale, but not detail), 144x w/AT72EDII, 150-171x w/Orion ED80, 193 to 220x for the Orion 110ED (FPL 51 type doublet, shows some color).  I have more history with the 8" SCT in very good/excellent seeing and have always found it topping out for planetary at 290x nominal/310x+ actual since a 2" TV w/high hat adapter is used--but it almost never reaches that level out here, which is why I had to augment my normal planetary set of 9 and 7 Naglers with an 11 and then a 13 to get me through typical evenings.  My son's 10" has supported 357x well when the seeing was very good, and 417x briefly when the seeing was at its best before declining again.  The 20" has been very limited locally, 357 and 417x for planetary on the best nights; while in East Texas 500x was not uncommon and I sketched Mars at 714x with it.  Back then I was planning to try albedo mapping Ganymede...life got in the way, and it hasn't been feasible here due to seeing.

 

I get better average seeing between 4,000 and 8,500 feet, but that still doesn't compare with what I was accustomed to for my first decade of observing.  The poor seeing in the valley, along with the rapid increase in light pollution have served to "extinct" my backyard observing enthusiasm.   If the seeing was as good or nearly as good in the back yard as it is at my dark sites, then I would do far more backyard observing than I do, particularly when the Moon is up.  For some folks it is the other way around, their backyards have better seeing (but are bright), so for them it is merely a matter of switching target types.  

 

Very tight double stars are different with respect to optimum magnification, because the contrast is greater, so if the diffraction pattern is discernible I can push substantially higher to see more, rather than beginning to lose modest contrast planetary detail.  Scale is generally an ally for close doubles.  The spurious disks can punch through the mess as long as the seeing is about 3/10 or 4/10 for the aperture.  However it takes better seeing to identify close high delta magnitude companions at higher mags.

 

6/10 seeing with a 4" is about 4/10 with an 8", and about 2/10 with a 20", and about 7/10 with an 80mm.  For reference, 6/10 with a 6" aperture is listed as "fair to good" on the Pickering scale, while 7/10 is "good".  Of course, 6/10 with a 20" is about 9/10 with a 6" and rated as "excellent."  

[pugliano]

The OP joined in 2011 and this is only their second post.

 

They may not be back for another 14 years! So let's make their time here pleasant.

 

I'm with the "any observing is better than no observing" crowd, but I have no answer to your specific question.

 

If you think it's too much of a chore though to take your dob out from the shed each cloudless night, the benefit not being worth the cost if the seeing is less than stellar, then I'd suggest you either have the wrong scope for your level of interest in the hobby, or that you may want to consider making a simple observatory so that your scope will always be instantly available without the hassle of taking it out of the shed. Do you wheel out your dob or carry it by hand?

 

Like some others here, I just judge how my views might be on any given night based on the twinkle of the stars, but that's not the deciding factor on whether or not I'm going to observe.

 

But everyone is different and has different desires and standards.

 

Good luck to you! I hope someone can answer your specific question.

Edited by pugliano, 04 May 2025 - 08:32 AM.

[vtornado]

Would a pair of binos help with judging twinkling and seeing?  I keep a pair on a peg by the door.

[WillR]

Is there a way to judge "seeing" conditions quickly and easily without setting up your whole astronomy rig and conducting intricate tests?

Even better, is there a way to do that without leaving your armchair, some sort of remote camera set up outside with software that automatically evaluates seeing and notifies you when it's particularly good?

This is for backyard observing with a dob kept in a shed. It's not realistic to wheel it out every night, so I'd like to focus my efforts on the best nights.

Well, you can look at an app. Or you could get out of your chair and go outside and look at the sky. But if you can’t be bothered to get out of your chair, just how serious are you about observing?

[daveb2022]

I think the OP is looking for an electronic or other method to determine seeing other than visually using some type of grab and go optics.

I'll stop short of suggesting lack of ambition being an issue, because there are a host of reasons I might not want to observe, including weather and even my health issues if seeing conditions make observing questionable.  

 

Odd timing, but a few nights back I had the worst seeing conditions I've had for 25 years from my home observing site. It was a wind shear event. I just don't get those here. On this night, the stars were twinkling enough that it showed below average seeing, but after the wind shear, visually the stars appeared more steady. However in the scope, the stars were bloated and appeared out of focus. The stars were not rumbling much at all, which is more similar with poor Pickering levels. The seeing went from below average (average for my site) to worthless in less than 30 minutes. I had been taking images of the moon, but after the event hit, the moon was not observable. It flat stopped my session, but was a fascinating weather phenomenon. I've had similar conditions at remote spots, but from home, it was a record...the worst skies I've encountered from the back patio. 

Edited by daveb2022, 09 May 2025 - 01:21 PM.

[Redbetter]

Would a pair of binos help with judging twinkling and seeing?  I keep a pair on a peg by the door.

 

I guess someone could try to calibrate/correlate their particular aperture x mag binos to observed seeing through a scope, but it seems like a lot more work than just using naked eye correlation or using a scope.

 

Binos don't provide anywhere near the scale needed to evaluate seeing on their own, so it would again be down to twinkle, which is a way of evaluating at 1x scale.  And even the larger binoculars would be marginal for evaluating seeing in terms of aperture, even if one was using telescope levels of magnification. 

 

For example, a 60ED scope at 100x or so still provides only very limited information about the seeing.  It can reveal the seeing will be bad, but provides very little information for good seeing.  8/10 Pickering as seen and evaluated through a 60mm is about 5/10 in a 6 inch, and 4/10 in an 8 or 10".  And mediocre appearance of the diffraction pattern in a 60mm will be poor in medium aperture.  My experience has been that 80mm begins to provide somewhat more useful discrimination with respect to quality of the seeing, using one as a "seeing scout."  An 80 will more readily reveal the difference between fair and good seeing, but it won't reveal differences below about 1 arc second.  

Edited by Redbetter, 09 May 2025 - 01:40 PM.

[Androux]

Thanks for all of the constructive comments, from basic rules of thumb to more technical. I must admit surprise at the smattering of grouchy remarks cast my way after asking a simple question in a beginner's forum that sparked some otherwise thoughtful conversation. Maybe lack of sleep? It's okay to be an occasional astronomer. 

Edited by Androux, 10 May 2025 - 11:13 PM.

[Eddgie]

If there are no clouds, I bring out a telescope.

 

If seeing is poor, I look at things that don't need good seeing, which is the vast majority of things in the sky. 

 

To me, the only things that are affected by less than very good seeing are double stars and solar system objects. (If you are doing limiting magnitude study, this too will be affected, but most armatures don't do this kind of observing.) Everything else will not be so affected enough by seeing as to stop me from wanting to view them. 

 

My advice is to go outside and use your telescope and not worry about seeing, but rather focus on what you will be able to see given the conditions available that exist. It is like the old saying, when life gives you lemons, make lemonade. 

Edited by Eddgie, 15 May 2025 - 07:27 AM.

[GSwaim]

Most people hardly ever look up at the sky for any reason unless there's a reason. Amateur astronomy hobby is one of those reasons. 

 

Most weather forecasts are inaccurate by at least 50% of the time. I've seen rain the daily forecast with a clear sky and no clouds before, so ..

After a while of doing the hobby of amateur astronomy one gets a feel for what the weather will be like by simply going outside to have a look.

For those that are too lazy to get off of their bottom to actually get up & go outside to look then they can look at security camera footage if they have such a system installed at their residence. But then the question becomes are they even motivated enough to move equipment outside to setup a telescope in the first place?

 

Amateur astronomy is a hobby in which one can actually apply & learn real science and perhaps make real discoveries too. This hobby requires much patience, good equipment, and a open mind to learn new things.

Edited by GSwaim, 15 May 2025 - 09:11 AM.

[AuroraBo]

Is there a way to judge "seeing" conditions quickly and easily without setting up your whole astronomy rig and conducting intricate tests?

Even better, is there a way to do that without leaving your armchair, some sort of remote camera set up outside with software that automatically evaluates seeing and notifies you when it's particularly good?

This is for backyard observing with a dob kept in a shed. It's not realistic to wheel it out every night, so I'd like to focus my efforts on the best nights.

The closest thing to what you're looking for, i.e., a software that automatically evaluates seeing, that I know of is the app Astrospheric. It gives you an idea of the cloud cover, transparency, and seeing. It also makes predictions for the future. 

[ClsscLib]

Thanks for the suggestions about Astropheric — what a handy app!

[pmoos]

Astropheric has worked pretty well for me, and often predicts the best 'window' of time on a given night.  But I find that the bottom line is just going outside and checking it out.  I will usually check things out with binos, and then if conditions look promising bring out a bigger scope.  Sometimes I enjoy the binos so much that I never get around to getting the bigger scope out.

[scout]

I often check one of the several live online Jet Stream Maps if the stars are twinkling a lot. If the jet stream is hanging above me, I know the seeing probably won't improve much that night and I'll take out a small refractor for some low-powered views.

 

But if the jet stream isn't above making a mess of the sky and the seeing is still bad, don't give up, because the seeing often improves dramatically a few hours after sunset.

[WillR]

Thanks for all of the constructive comments, from basic rules of thumb to more technical. I must admit surprise at the smattering of grouchy remarks cast my way after asking a simple question in a beginner's forum that sparked some otherwise thoughtful conversation. Maybe lack of sleep? It's okay to be an occasional astronomer. 

Yes, I was one of the grouchy ones. Must have been lack of sleep. My apologies.

 

Use an app and take your chances. That’s about the best you can do. If you are in a dry climate, leave your dob out and cover it. Clear skies to you.

[csrlice12]

You view the skies you have, not the sky you wish you had....for some, getting out is easy; for others, we don't get out often.  Not because we don't want too, but we have sick kids or spouses or our own limitations....to us, any clear night we can get out is a treasure, even if it's only to be in dark skies using our naked eyes.  Having a dog can also be an impediment to getting out for both you and the dog.

[havasman]

I often check one of the several live online Jet Stream Maps if the stars are twinkling a lot. If the jet stream is hanging above me, I know the seeing probably won't improve much that night and I'll take out a small refractor for some low-powered views.

 

But if the jet stream isn't above making a mess of the sky and the seeing is still bad, don't give up, because the seeing often improves dramatically a few hours after sunset.

Yes, this is the only type of tool I know that may fulfill the OP's need. I like to use aviation winds aloft maps as they can indicate turbulence via showing differing speeds and directions at different altitudes. And they also have predictive functions so you can look ahead in time to make choices. 

 

And as often said above, the choices definitely include what to observe given the predicted conditions. Whether to observe is a different choice. Good observing can be done in less than optimum seeing.

Edited by havasman, 25 May 2025 - 11:39 AM.

[CarolinaBanker]

My quick and dirty test is how high in the skies are the stars twinkling, if it’s really only noticeable to 30 degrees it’s probably decent seeing. With that said I’ll just adjust to the seeing, if it’s bad, I’ll focus on open clusters.

[annas]

In my area, the early indicators of bad seeing typically include dusty/foggy air or high altitude cloud cover or both. For clouds, I rely on weather radars and forecasts. To assess dust, fog, and overall air quality, I use a PTZ zoom camera before sunset.

My camera has a 30x zoom capability, which I point toward a large mountain near me about 15 km away. At maximum zoom I examine fine details like rock formations and tree clusters on the mountainside. Over time, I learned to gauge and estimate the approaching night’s seeing conditions based on the clarity of these distant features.

This method has proven highly reliable to me many times to identify nights that aren’t worth the effort and more importantly those with pristine skies that cannot be missed!

[NinePlanets]

I... 30x zoom capability, which I point toward a large mountain near me about 15 km away. At maximum zoom I examine fine details like rock formations

I do a similar thing with a spotting scope. It at least gives an idea of the level of near-ground turbulence.
 

[csrlice12]

I use the Barbarian method...I go outside and look up.  Then consider other factors such as is it day or night, is it cold, alien invasions, etc...

[dexx]

The simplest check is to look outside at the stars.  If there is little to no twinkle then the seeing is likely good, very good, or excellent.  Stars lower in the sky twinkle more, so if those are steady it is likely very good.  

Wow i dont think i have ever seen the stars not twinkle.  Even when overhead; Sirius, Canopus, and similar bright stars look like disco balls!

[robjme]

I've heard of the Pickering Scale before but never gave it much thought. To better understand this thread, and to learn something new, I did a search on the Pickering Scale and came across this site that made the whole thing clear to me.   https://www.damianpe...m/pickering.htm

 

Thanks for all of the constructive comments, from basic rules of thumb to more technical. I must admit surprise at the smattering of grouchy remarks cast my way after asking a simple question in a beginner's forum that sparked some otherwise thoughtful conversation. Maybe lack of sleep? It's okay to be an occasional astronomer. 

Androux makes a good point here. This is a beginner's forum and his post began an interesting thread. Thank you Androux for your question.

 

As for me, I have something Androux may, or may not have, and that is experience judging the sky at dusk. My advice to any beginner is: keep looking up and become sky aware. Forecasts and Apps can be helpful, but you don't need a weatherman to tell you what the skies overhead look like. Of course, things get more complicated when one must travel to the observing site.

 

Something else, the weather can change rapidly. I once left my scope out on a perfectly clear night and then had to scramble outside as the rain began to pour. The sky conditions at dusk may become very different later in the evening. Sometimes, there are low hanging clouds with dark, clear skies above. Under these conditions, I bounce around the sky to avoid the low clouds.

 

And finally, I've noticed that on many or most nights the sky settles down after twilight and the seeing conditions improve by midnight. It's usually worth waiting for, depending on your schedule. And then again sometimes things just get worse. Every night is an adventure.

[Jon_Doh]

Like dexx I've never ever seen stars twinkle.  I did see stars one time when I tried to bring down a fullback who broke into the backfield like a locomotive.  But they didn't twinkle.  

[ClsscLib]

Like dexx I've never ever seen stars twinkle.  I did see stars one time when I tried to bring down a fullback who broke into the backfield like a locomotive.  But they didn't twinkle.  

My college team won the first game of my first year and the last game of my fourth year, losing all the games in between.

 

But our fullback twinkled.