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General Astronomy >> General Observing and Astronomy

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Tom Polakis
Carpal Tunnel
*****

Reged: 12/20/04

Loc: Tempe, Arizona
Re: Seeing Across The USA new [Re: Jon Isaacs]
      #5757867 - 03/26/13 10:21 AM

Quote:

Quote:

Note that steadiness as seen through a telescope often has little correlation with naked-eye twinkling of stars. It's pretty common in my back yard to have almost no visible twinkling and 5-arcsecond seeing.




Tom:

At first I thought maybe you had meant 0.5 arc-second seeing.

I have to think San Diego has significantly better than average seeing. Generally south of the jet streams and with mild winds blowing off the Pacific, it is generally quite steady. Splitting a 1 arc-second double is pretty typical.

Of course if the wind turns around and blows across the mountains from the east.. not good, clear but turbulent.

Jon





Jon,

I was just throwing 5 arcseconds out there as a bad example of no scintillation/lousy seeing. The median seeing in my back yard in Tempe is around 2 1/2 arcseconds -- still not good, I know.

Not as often, I see violently twinkling stars, but remarkably steady views at 300x. You can't tell much of anything about the steadiness until you look through the scope.

Tom


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csrlice12
Postmaster
*****

Reged: 05/22/12

Loc: Denver, CO
Re: Seeing Across The USA new [Re: hfjacinto]
      #5757936 - 03/26/13 10:52 AM

Yes, I've noticed all the various shades of grey the sky can have....I tell you young whippersnappers there twas a time in this old world where the skies actually had a blue color, and during the rest phase, would get black with lots of shiney things in the sky. People used to look up at these shiney things; but it created fear in their hearts....grey is such a nice claming color.......What color of grey are your clouds today?

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csrlice12
Postmaster
*****

Reged: 05/22/12

Loc: Denver, CO
Re: Seeing Across The USA new [Re: hfjacinto]
      #5757941 - 03/26/13 10:56 AM

"Mid-latitudes -- say 40 to 50 in both hemispheres -- tend to have poor seeing due to the jet stream. That includes both New York City and Denver".

Ah, but on those nights the Jet Stream heads North.......tis a different story.

But agree that New Mexico has some fantastic skies; lived in the middle of nowhere New Mexico...the skies---WOW!


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Eric63
professor emeritus


Reged: 06/16/12

Loc: Ottawa, Ontario
Re: Seeing Across The USA new [Re: csrlice12]
      #5758110 - 03/26/13 12:28 PM

I find this topic very interesting since many newcomers that are interested in lunar and planetary viewing, are often recommended to go with more aperture. Without knowing their seeing conditions this may be the wrong recommendation. Here in Eastern Ontario the seeing is 3/5 or less (on the Clear Sky Chart scale) approximately 80% of the time. That means that it is rare that I will get below 2 arcseconds. This fact convinced me to stay with my 127mm Mak for planetary since I would not be able to take advantage of a larger scope to see more detail (but I would have increased brightness). In fact from what I have read, a larger scope may make things worse under these conditions. But for those where the seeing can get them below 2 arcsecond more often, like on the west coast or in the Florida Keys, then yes, more aperture is worth it. For most of us under the Jet Stream though, smaller is often better.

Eric


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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Seeing Across The USA new [Re: Eric63]
      #5758640 - 03/26/13 04:52 PM

Quote:

I find this topic very interesting since many newcomers that are interested in lunar and planetary viewing, are often recommended to go with more aperture. Without knowing their seeing conditions this may be the wrong recommendation. Here in Eastern Ontario the seeing is 3/5 or less (on the Clear Sky Chart scale) approximately 80% of the time. That means that it is rare that I will get below 2 arcseconds. This fact convinced me to stay with my 127mm Mak for planetary since I would not be able to take advantage of a larger scope to see more detail (but I would have increased brightness). In fact from what I have read, a larger scope may make things worse under these conditions. But for those where the seeing can get them below 2 arcsecond more often, like on the west coast or in the Florida Keys, then yes, more aperture is worth it. For most of us under the Jet Stream though, smaller is often better.

Eric




Eric:

Actually, in 2 arc-second seeing, an 8 inch scope can outperform a 5 inch when viewing the planets. Vla of the website Telescope Optics has done some simulations that shown this.

Jon


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BluewaterObserva
Postmaster
***

Reged: 05/18/04

Re: Seeing Across The USA new [Re: Jon Isaacs]
      #5758668 - 03/26/13 05:05 PM

Denver is tough... The light dome extends very very far...

Two closest decent spots?

Guenella (sp?) pass... Observing outside at 12,000'+ is an aquired taste.

The Greenland exit half way between Denver and Colorado Springs.

We used to go three hours or so out on the Pawnee Grasslands... We used to hear the mysterious native american chants and drums in the wee hours, we did not think much of it until we seen it on one of the those Ghost investigator shows. Spooooooky thinking back on it now.


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GeneT
Ely Kid
*****

Reged: 11/07/08

Loc: South Texas
Re: Seeing Across The USA new [Re: jpcannavo]
      #5758821 - 03/26/13 06:31 PM

I check a half dozen weather sites every day. Watch the coming and going of fronts. I check the jet stream over my location each time I am going to view. If I were moving to Denver, I would check with their astronomy clubs with recommendations on where to live for best access to good viewing.

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GeneT
Ely Kid
*****

Reged: 11/07/08

Loc: South Texas
Re: Seeing Across The USA new [Re: Eric63]
      #5758827 - 03/26/13 06:36 PM

Quote:

I find this topic very interesting since many newcomers that are interested in lunar and planetary viewing, are often recommended to go with more aperture.




Yes and no. For six months I viewed with an 18 inch Ultra Compact and a 12.5 inch Portaball. My Portaball consistently provided better views of the planets. Quality of optics and other factors figure in here. For one thing, I believe my primary and secondary mirrors were better than in my UC. However, my 18 UC had more than twice the light gathering of my 12.5, so there was no contest on DSO's.


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Eric63
professor emeritus


Reged: 06/16/12

Loc: Ottawa, Ontario
Re: Seeing Across The USA new [Re: Jon Isaacs]
      #5759059 - 03/26/13 08:18 PM

I guess I would beleive that the 8" would be better at 2 arc-second, which is not the average up here. I assume there is a point where aperture is no longer an advantage and the trick is to know how often the seeing is better than that particular point. Average seeing according to the shy charts falls between 2 arc-seconds and 5 arc-seconds for a 6 inch scope. So when the statistics tell me that I have average seeing (or worse) 80% of the time, I am not sure how often I am closer to 2 arc-seconds or 5 arc-seconds, which is a significant difference. Since I am new to this, I have yet to figure out how to tell if I have 2 arc-second seeing. My rule right now is if Jupiter is drab grey, forget it, but if I can see nice redish brown colour, details will be revealed and I may even have glimpse of amazing seeing. One one of those nights I saw the GRS, swirling around the spot, three white ovals in the SEB and some details such as barges, shading at the poles etc. But right now most of the time I simply see three grey bands.

Eric


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Eric63
professor emeritus


Reged: 06/16/12

Loc: Ottawa, Ontario
Re: Seeing Across The USA new [Re: GeneT]
      #5759084 - 03/26/13 08:24 PM

You are not helping me keep my aperture fever in check I am still trying to understand my seeing conditions and how it will affect my choice of scope(s). Being mainly interested in lunar and planetary I am still debating either getting a larger CAT or a good APO as my next scope. But I guess that's part of the fun.

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Tony Flanders
Postmaster
*****

Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: Seeing Across The USA new [Re: Eric63]
      #5759580 - 03/27/13 04:56 AM

Quote:

Being mainly interested in lunar and planetary I am still debating either getting a larger CAT or a good APO as my next scope. But I guess that's part of the fun.




Traditionally, Newtonians have been the instruments of choice for serious planetary observers. But an SCT is a lot easier to mount and motor drive.

Given the availability of excellent 6-inch telescopes for reasonable prices, it seems silly to go with anything smaller. Even in an area with mediocre seeing, a 6-inch scope will often outperform a 5-inch scope.

Personally, I think it's silly to go with less than 8 inches. It's tough for APOs to compete in that range. Granted, a 6-inch APO might well deliver as much planetary detail as an 8-inch Newt, and would almost certainly outperform an 8-inch SCT. But a 6-inch APO isn't cheap.


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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Seeing Across The USA new [Re: Eric63]
      #5759620 - 03/27/13 06:21 AM

Quote:

You are not helping me keep my aperture fever in check I am still trying to understand my seeing conditions and how it will affect my choice of scope(s). Being mainly interested in lunar and planetary I am still debating either getting a larger CAT or a good APO as my next scope. But I guess that's part of the fun.




This is what Roland Christen has to say:

What is the best Planetary Scope

My thinking is that the best planetary scope depends on your situation and your criteria. If you live where the seeing is typical poor, then the "best planetary" scope is probably is probably a scope that can make the best of a bad situation. On the other hand, if you live where the seeing is generally good and can be excellent, then the "best planetary" scope is one that is large enough to take advantage of that excellent seeing.

My situation tends to be in the later category but observers whom I trust like Alan French say that when their seeing is poor, typically there are moments of excellent seeing when a large scope can show it's stuff.

Jon


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jpcannavo
scholastic sledgehammer
*****

Reged: 02/21/05

Loc: Long Island New York
Re: Seeing Across The USA new [Re: Jon Isaacs]
      #5759636 - 03/27/13 06:53 AM

Although the OP is hoping this thread doesn't digress along other lines, such as "best scope for...", I will offer this: Seeing is quite important for deep sky work as well. Aperture reveals detail in faint extended objects by allowing higher magnification while preserving surface brightness. But poor seeing can foil this optical leverage.

I recall one night in Benson Arizona where I was decidely unimpressed with NGC 4565 and m51 through a 14.5" newtonian (The old Vega Bray observatory at The Astronomers Inn). On a diiferent night - similar transparency/NELM - however detail emerged that I still remeber to this day! This was all seeing related. On another ocasion, at The Oregon Star Party, similar diiferences on different nights of very different seeing revealed dramatic differences in deep sky that led to much recollection and commentary during daylight hours.

Also, the OP was not only curious about Denver - but is glad to receive the heads up/input (And will be attending The Rocky Mountain Star Stare in June!). Its fun to hear these reports on seeing from everywhere - good and bad!


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t.r.
Post Laureate
*****

Reged: 02/14/08

Loc: Upstate NY
Re: Seeing Across The USA new [Re: jpcannavo]
      #5759737 - 03/27/13 08:29 AM

Eric, I'm just downwind from you on the south shore of Lake Ontario. Yes, indeed our seeing is challenging! A friend of mine recently asked if it was really worth it to be in this hobby in NY and considered selling his gear! One night, in the summer no less, we set up his 7" refractor with my 5" refractor side-by-side. We went to Jupiter and guess what? Even though Jupiter was brighter in the 7", there was NO additional detail to be seen, although the red spot, a moon shadow and several belts were well defined! Micro planetary detail is hard to come by here in the NE even with increased resolution from aperture!

For thirteen years I used a 4" Genesis refractor side-by-side with a very good C8. For planetary...75% of the time the 4" won out! The seeing crippled the SCT. There were of course nights, usually in the summer no surprise, that it surpassed the 4", and it always did show better deep sky faint fuzzies of course. I have now moved to a 5" apo refractor as my primary instrument with a C11 for the good nights. THe 5" does show more than the 4" did, so my new minimum is now the 5 and I think you are right on the mark with the 127 you own for getting the most useful resolution per days of the year for planetary viewing. On the very best of nights in Jun/Jul/Aug the C11 pummels the 5" apo on planetary and it always shows great deep sky! For all those that say "Aperture Rules" I add "When Seeing Allows"!


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bunyon
Carpal Tunnel
*****

Reged: 10/23/10

Loc: Winston-Salem, NC
Re: Seeing Across The USA new [Re: t.r.]
      #5759746 - 03/27/13 08:34 AM

For what it's worth, North Carolina, depending on where you are, has periods of good seeing and periods of bad. Late spring/summer/early fall tend to be good, the rest not.

As for choosing where to move (not that the OP is saying that), one would choose based on interest. If you're primarily a planetary observer, then seeing is more important than darkness. If you find a place that is both dark and has excellent seeing, you'll probably find a professional observatory there.

Seeing is one of the key factors used to choose sites for big observatories. Resolution is just as important in DSOs as it is for planets once you have a dark enough sky and big enough scope to see the DSO well.


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Eric63
professor emeritus


Reged: 06/16/12

Loc: Ottawa, Ontario
Re: Seeing Across The USA new [Re: t.r.]
      #5760150 - 03/27/13 12:28 PM

Hi Tim

I’m glad to hear that you confirmed my suspicions about best useable aperture. As you know the weather here has been pretty bad these past months. Since last fall, I have only been able to observe my favourite planet, Jupiter, 17 times. If weather was not the issue, then family obligations were. Anyway, of those 17 times, 11 had bad seeing. The best I could see were the main bands in a drab grey colour. Three other times, I could make out colour and a hint of shading at the poles, and had I looked closer, I think some detail would have shown itself. But the three last times the seeing was above average and now the colour was amazing, the belts well defined, the GRS easy to see and with detail around it. White ovals were very clear and other details too such as barges and a hint of festoons. So in my case, 64% of the time Jupiter was a wash out, 18% was ok and another 18% was quite good. I also had the sense that my scope could do even better since during the good seeing I had fleeting moments of better views; but I’m too new to his hobby to make such comparisons right now. I can’t wait for better seeing in the summer…but Jupiter will be only be available in the early morning hours

Since my wife and I plan to downsize to an apartment condo in the next few years, I think that small scopes will continue to be on the horizon…but I will not rule out a C8

Eric


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azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Seeing Across The USA new [Re: hfjacinto]
      #5761037 - 03/27/13 06:51 PM

Some people actually swear by city seeing. You might find summer in NYC offers far better seeing than winter.

Pete


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Tony Flanders
Postmaster
*****

Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: Seeing Across The USA new [Re: azure1961p]
      #5761130 - 03/27/13 07:40 PM

Quote:

Some people actually swear by city seeing.




I think that in general seeing is better in cities due to the "urban heat island" effect. Basically, cities cool off less at night. Helps with dew, too.


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jpcannavo
scholastic sledgehammer
*****

Reged: 02/21/05

Loc: Long Island New York
Re: Seeing Across The USA new [Re: azure1961p]
      #5761143 - 03/27/13 07:45 PM

Quote:

Some people actually swear by city seeing. You might find summer in NYC offers far better seeing than winter.

Pete




No doubt summer tends to be better here - but that ain't saying much! The main problem for the NY area (I think) is that the jet stream is omnipresent.

Joe


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Cotts
Just Wondering
*****

Reged: 10/10/05

Loc: Toronto, Ontario
Re: Seeing Across The USA new [Re: jpcannavo]
      #5761233 - 03/27/13 08:26 PM

Lots of interesting information here. And lots of generalizations.

The jet stream moves from nearly 60 degrees latitude to 20 degrees. It isn't 'over' one particular latitude range constantly at all. It may be slightly more frequent further north than more southern climes.

My experience in the Great Lakes region is that air masses and the fronts associated with them have a lot to do with seeing (and transparency which isn't a part of this discussion).

If a strong cold front blows through, the high pressure, cooler air mass behind it (first night after) usually has excellent transparency and terrible seeing. The air is turbulent but cooler and drier. The jet stream is often south of us or over us. If the high pressure zone lasts a second and third night the seeing often improves greatly but at the expense of some transparency.

Warm, humid, sub tropical air masses (we get these in June - Sept. here) from the Gulf of Mexico region can often have the very best seeing while water is dripping from every surface. In this situation the jet stream is well north of us.

In addition to the above, local conditions from micro (your lawn vs. your driveway) to meso (city? country? lake nearby? e.g.) to macro (lee of ocean breeze, mountain ranges etc.) all play a part.

A complex subject where the best answer is often, "It depends."

Dave


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