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#1 -Starfighter-

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Posted 12 August 2014 - 05:14 PM

I was just curious about all the observers viewing from their driveways or nearby their homes, what is the apparent magnitude that you can see? What is your measure of reasonably good from your home taking into account the neighbors lights and possible street lights?

 

What mags are people achieving at their dark sites with what aperture?

 

My limit from driveway is mag +5 / (+6 on a good night, even then it's tough.) Nearby the house at a darker spot perhaps +7?

 

Thoughts, comments?



#2 mdowns

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Posted 12 August 2014 - 05:32 PM

Though the milky way is always obvious throughout the summer here,5th mag is about the limit for me in the orange zone where I live. I might do better if I try really hard.



#3 jethro

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Posted 12 August 2014 - 05:57 PM

Where I'm at, it averages at 5 mag. Occassionally, it will hit around 6 mag.
The worst time is December. I can't see anything since one of my neighbors
turns his yard into Santa's Sweatshop. I used to like X-mas time- until I
was bitten by our friendly starbug.

#4 joaoba

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Posted 12 August 2014 - 05:59 PM

The best I've seen from my backyard is mag 6.9. Our house is considered an "orange" zone, but the view from the backyard always seems better than it should be. From a dark site I've seen as faint as 7.5. I've spotted M81 a couple of times with naked eye.

 

Edit... I checked my notes and the best from my backyard was 6.09, not 6.9. It was a little star in the question mark of the Alpha Persei cluster (HP 15988). My backyard is terraced and area where I set up is sunken and shielded by a tall fence. There is only one yard light in the alley and it is blocked by my neighbors shed, and the house blocks out city lights to the south. The M81 nights happened at black sites at high elevation (7200' and 9000'). There's a mag 7.1 star nearby that makes a nice guide post.


Edited by joaoba, 13 August 2014 - 02:51 PM.

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#5 jethro

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Posted 12 August 2014 - 06:02 PM

I want to move to Montana!

#6 Feidb

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Posted 12 August 2014 - 08:52 PM

I live in a red/orange zone in Northeast Las Vegas right next to a high school with a football field, about two blocks away. Yeah, a perfect place. Nellis AFB is also just north of me. The Strip is to the West. I'm lucky to see down to mag. 3 most nights. However, there have been nights where I've been able to see down to mag. 4 unaided, just enough to aim my 16-inch at the correct spot and observe a few mag. 10 and 11 planetaries with high surface brightness. I've spotted M-57 when the keystone of Lyra was visible, which isn't that often. I've found the Orion Nebula but even in a 16-inch, it's nothing to brag about from that part of town.

 

The only reason I set up at all is when I just can't get to a dark site and the Observer's Challenge I'm working on for the Las Vegas Astronomical Society is bright enough and in an easy enough part of the sky that I have a reasonable chance of finding and actually seeing it in skies with a light-gray background. I've done it twice now, so it IS possible, but I don't really like it.



#7 magic612

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Posted 12 August 2014 - 10:32 PM

I'm 40 miles south of Chicago. I've identified 5.0 magnitude stars overhead, and seen about 90 degrees of the Milky Way (45 degrees each way from the zenith) on a few selected perfectly transparent nights.

 

But typically, humidity and other factors often put the sky at 4.5 magnitude NELM on most nights. 



#8 galexand

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Posted 13 August 2014 - 10:14 AM

Urban (red zone) front yard...if I can see Vega (mag 0), it's clear.  If I can see gamma lyrae / sulafat (mag 3.2), it's worth taking out the telescope.  If I can see rest of the trapezoid in Lyra (mag 4-4.5), I might spend a couple hours out!  Once in a while, I've seen down to mag 5.



#9 havasman

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Posted 13 August 2014 - 11:11 AM

White zone here with a lit church parking lot behind my house just across the alley with an 8' stone wall between. I can usually see the 12 - 15 brightest stars with unaided eye. Sometimes fewer. But it's never been so bad that I couldn't find a couple of stars to align the scope and check out some doubles, clusters and bright extended objects. No challenging targets presented this year except on 1 or 2 rare nights. The small scopes just provide some ideas of what's missing most of the time.

I'd really enjoy mag 5 skies for a change.

Good seeing to us all!



#10 tigerroach

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Posted 13 August 2014 - 11:49 AM

I live on the fringes of a white zone; I can see all the way to mag 2 if it's really clear. :grin:

 

From the back yard though I'm well screened from any direct street or porch lights, so I can and do observe the moon and bright planets from there.


Edited by tigerroach, 13 August 2014 - 11:52 AM.


#11 Tony Flanders

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Posted 13 August 2014 - 01:49 PM

I was just curious about all the observers viewing from their driveways or nearby their homes, what is the apparent magnitude that you can see? What is your measure of reasonably good from your home taking into account the neighbors lights and possible street lights?


I have two homes, one in the city and one in the country.

My city home has no backyard or driveway, so the only way to observe right next to it is from the sidewalk. I normally only do that for the Sun, Moon, and planets -- and rarely at that.

In many ways, having no backyard is a blessing, because it means I don't have to put up with suboptimal conditions. When I observe in the city, I usually bicycle or drive to one of various parks that have no lights overhead. From the closest, 3/4 mile from my apartment and 4.5 miles from the center of Boston (a metropolis of 5 million), I can see stars roughly down to mag 4.7 on a good night. M31 and the Double Cluster are fairly easy to spot naked-eye, but I have never seen the Milky Way there.

My country home has pretty severe light pollution for a rural area, but there are no nearby lights and few visible lights at all, especially when the leaves are on the trees. The Milky Way is instantly obvious, but it's lacking in snap. M13 is easy naked-eye; M33 is visible with averted vision but tough. I can see stars roughly down to magnitude 6.5, but I'm much too lazy to pin it down finer than that.

#12 Starman1

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Posted 13 August 2014 - 05:48 PM

My naked eye vision isn't acute enough to give a realistic estimate of the naked eye limiting magnitude here in L.A.

I can, however, give you a range of the SQM that covers it: 16.8mpsas under average conditions to 17.5mpsas under clear skies with no Moon.

That's about 4.3 to 4.8 NELM at best.  I can't see that with the naked eye, but other people have verified that.

 

I prefer to drive to a site to observe.  My close site averages 21.35 mpsas on the SQM (6.75NELM)

My more distant site averages 21.65mpsas (6.9NELM).

The darkest I've seen in SoCal was a 21.89 under incredible conditions (~7.0NELM)

 

The SQM figures are averages for an 80 degree-wide cone on the zenith, too, and since the zenith is always darker, that last figure was truly magnificent.



#13 17.5Dob

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Posted 13 August 2014 - 06:33 PM

I don't think I've ever seen the Milky Way in my "bright" red backyard . At the best, most nights run in the 4-4.5 mag range, "IF" I can wait 'till after midnight for the many extraneous park lights, softball field lights,and the few 100,000+ smaller porch lights in the neighborhood to go off.

At least I'm blessed with a plethera of "Grey" zones starting just 1 hr away.



#14 GeneT

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Posted 13 August 2014 - 06:40 PM

The skies are Mag 3 in my back yard. In addition, the trees are too tall. I won't view in my front yard because I don't want drive bys to see an expensive telescope and mark my house for a hit. I drive to a site about 22 miles from my house. The skies are about Mag 5. You guys who have Mag 5 or better skies in your back yard are very fortunate. 



#15 sedmondson

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Posted 13 August 2014 - 11:33 PM

The best I have from my rural home is mag 5 or maybe a little better. But with the summer haze it usually more like 4.5. Still I think I am fortunate. Its reasonably dark, very little neighbor's lighting, and lots of open sky. I don't go out to dark sites much these days.



#16 DSObserver2000

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Posted 13 August 2014 - 11:43 PM

From my yellow/orange backyard I can see magnitude 6 on really good nights. On almost any moonless night the Milky Way is obvious and on transparent ones I can see it split into 2 branches in Cygnus and M13 barely naked eye.



#17 havasman

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Posted 14 August 2014 - 01:40 AM

Despite the challenges of locale, tonight's little driveway session rescued a bad week 4 me. It was clear and relatively dry for a change with almost no breeze and there was nothing really to complain of given the normal white zone conditions in the driveway. I took the XTi10 out for a look and started with M11, a personal fave that resolved well @ 133x and better @ 240 but 300x was pushing it too hard. Well resolved with the stacked V's, it was a good beginning. Staying in Scutum, I went to see M26 and found that the busy, rich field that can camouflage the cluster was wiped to a background haze that allowed the subject to stand out pretty well. I had to back off to the ES82 18mm @ 67x for a finder but M26 resolved well @ 179x. Then to IC4756 and NGC6633, a pair of large, neighboring open clusters that presented brightly in the ES82 30mm. Then to Ophiuchus for some double stars starting with Rho-Ohp appearing in the RACI at the apex of a delta of stars and resolving clearly @ 133x, widely @ 300x. It's listed span is 2".9. At an A-B split listed @ 1".4, Marfik presented a challenge with wide splits of A-C 119", A-D 308". All 4 components resolved pretty easily @ 133 and 300x but no color was noted at all. So I tried Z-Her but failed to get even a hint of a split @ listed 1".2 and didn't even attempt Sabik's 0".6 tight double that is at the theoretical limit for my scope. Looking for something easier and beautiful, I punched M6 into the intelliscope controller and swapped ep's for different perspectives of a fave grand open cluster. Integral to my enjoyment of it is walking back and forth from M6 to M7 and taking it all in. NGC6631 stood out surprisingly well in the Scutum haze, again benefiting from the bright sky that wiped the rich field to a bland gray. Finally as the moon got 20deg or so above the horizon, the big oak east of me in the yard couldn't shade the increasing sky glow as i checked in on NGC6520 in Sagittarius. A last, freehand look at Alberio and the ring nebula capped the night.

So the negatives of white zone view home sites can be dealt with and can seem to facilitate some targets' acquisition. Maybe best of all, 25 minutes after the last peek into the eyepiece everything was packed away and I was enjoying one celebratory fresh margarita and 45 minutes after that i'm finishing this note to you.



#18 Love Cowboy

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Posted 14 August 2014 - 06:24 AM

I live on the fringes of a white zone; I can see all the way to mag 2 if it's really clear. :grin:

 

From the back yard though I'm well screened from any direct street or porch lights, so I can and do observe the moon and bright planets from there.

 

Remember, limiting magnitude means the absolute faintest stars you can possibly see.  Not just the faintest stars you can see at a casual glance.  I'm in Houston too... I used to think it was 2 as you do, but then I started actually trying hard to see fainter stars that I knew were there and saw more.  On a clear night it's usually about a 4 here.    However, despite that I too usually stick to the lunar and planetary from home though.  My club's dark site has spoiled me for suitable skies for deep sky objects.  Speaking of which, if you haven't joined HAS, you might want to consider it. 



#19 cpper

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Posted 14 August 2014 - 06:41 AM

5.5 naked eye, 12.75 with the scope, on a good night.

I wonder if could catch 10 mag galaxies if I can see 12.75mag stars...


Edited by cpper, 14 August 2014 - 06:46 AM.


#20 Starman1

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Posted 14 August 2014 - 09:14 AM

5.5 naked eye, 12.75 with the scope, on a good night.

I wonder if could catch 10 mag galaxies if I can see 12.75mag stars...

If the galaxies are small and that brightness, then yes.

If the galaxies are large, probably not.

There are 2 magnitude figures, both of which have to be taken into account to determine visibility.

There is the Total Integrated Magnitude (the one often quoted) which is the brightness of the galaxy if the galaxy were compressed to about one square arc minute.

Then there is Surface Brightness, which is the brightness of the extended galaxy per square arc-minute (or arc-second in different figures).

A good example of how they can compare is M33, which has a TIM of 5.7,  Wow, that's bright!

But, the average SB is 14.1, and wow, that's faint.

So you really need to know both figures to determine the visibility of the galaxy in your scope.

A small magnitude 10 galaxy might have a SB of 11, and that would be a bright, easy galaxy compared to M33.

 

Lastly, you also have to take into account the Brightness Gradient of the galaxy.

That's the steepness or shallowness of the increase in brightness from the edge to the center.

Taking our example, M33, it has a moderately steep BG and its core is much brighter than the edges, so you'll see at least the core in a small scope.

M31 in Andromeda has an even steeper BG and it's hard to imagine a sky so bright the core wasn't visible in a telescope.

NGC891 in Andromeda, on the other hand, has a very shallow BG and the center is only a trace brighter than the edges, making it hard to see for

a lot of amateurs even though it has a high TIM.

 

TIM and SB are listed for many galaxies in reference works, both printed and on-line.

BG is not, though knowing the brightness of the center square arc minute would be useful to know for the larger galaxies.

If two hypothetical galaxies of TIM 9.0 peaked at 4.0 and 10.0 respectively, you could pretty much know in advance which one would be easier to see in an urban/suburban setting.


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#21 Tony Flanders

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Posted 14 August 2014 - 10:41 AM

5.5 naked eye, 12.75 with the scope, on a good night.


12.75 seems not very faint for an 8-inch scope if you can see magnitude 5.5 naked-eye. I would expect to see down to magnitude 13.0 at the very least, and probably well below that.

I note that the shortest eyepiece listed in your signature is 10 mm, giving you a magnification of 120X. That's not very high at all for an 8-inch scope. You could probably see fainter stars with more magnification.
 

I wonder if could catch 10 mag galaxies if I can see 12.75mag stars...


Certainly. Typical 10.0-magnitude NGC galaxies, with a reasonably high brightness profile, should be no problem at all. Probably even visible with direct vision.

Edited by Tony Flanders, 14 August 2014 - 10:41 AM.

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#22 cpper

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Posted 14 August 2014 - 12:20 PM

Wow, thanks guys. I thought that I can only see less than 10 galaxies in my skies. Don, I've always seen the "Surface brightness" label in Stellarium, but never asked myself what it's for. I will take your advice into account from now on. I find the SB more important that the TIM now   :hmm: .
Tony, I made a mistake... 12.75 is not the limiting mag in my scope, but it's the mag of a fainter star that I easily saw, and checked afterwards for it's mag. It's the relatively bright star near the Ring, and oops, it's 12.95 not 12.75. I will have my Shorty 2x (and 13mm Ethos  :evillaugh:)  in less than two weeks, thus making the 10mm a 5mm.


Edited by cpper, 14 August 2014 - 12:21 PM.


#23 Tony Flanders

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Posted 14 August 2014 - 12:35 PM

Tony, I made a mistake... 12.75 is not the limiting mag in my scope, but it's the mag of a fainter star that I easily saw, and checked afterwards for it's mag.


That makes more sense! But beware of magnitudes for faint stars -- depending what catalog they're from, they may not be very reliable.

#24 cpper

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Posted 14 August 2014 - 01:15 PM

I was using Stellarium, is it reliable ?



#25 cpper

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Posted 16 August 2014 - 12:55 PM

I have a query, but don't want to create a new topic just for this...

To be sure that I understand the relation between Magnitude(TIM) and Surface Brightness(SB):

Let's say there's a planetary nebulae with TIM=7 and SB=12 labeled A1, and one with TIM=12  and SB=7 labeled A2. From my understanding A1 will be a  large, faint, M33-like object. But what about A2 ? Is it a small, bright object then ?








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