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Why Light Pollution Can Be Better

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#1 Daniel Mounsey

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Posted 25 April 2010 - 03:40 PM

So why post this in the refractors forum? Because most refractors freaks are "contrast" freaks, myself included. We're all striving with the obsession of more and more contrast. BUT, what about too much contrast? Can this ever happen? How about and nice LCD television and lets just turn up the contrast all the way shall we? Why is it that television consumers realize that too much contrast looks bad but astronomers don't? After last nights star party to celebrate astronomy day with the Sidewalk astronomers association at a local church, I was continually bombarded with comments about how much better the Moon and Saturn would be from a dark mountain top, yet most observers couldn't be further from the truth.

The dark sky myth probably ranks in the top five biggest astronomy myths of all time. Observers are actually headed the wrong way with this mind set and it just never seems to subside, in fact its almost incredible. If you are a planetary enthusiast who views from a light polluted city, it may just be the biggest blessing in disguise, provided you also have good seeing to boot.

I am just nearing completion of my observatory which resides under heavily light polluted skies. Some of my astronomy buddies scoffed at this idea but I think some observers need to be reminded that astronomy isn't just about faint deep sky targets. Lunar/planetary, double stars and carbon stars are all very enjoyable targets that are in fact unhindered by light pollution, provided certain ones are not too faint. There are countless examples that are bright enough to provide a lifetime of enjoyment. I can literally spend entire evenings viewing all this stuff and so can you. I often enjoy it even more than deep sky sometimes. Why do so many observers always believe they have to find the darkest skies they possibly can in order to enjoy astronomy? I've seen carbon stars and double stars that could make your heart skip a beat!

In this particular case, for these particular targets, light pollution can in fact be better to have, not worse. Pretend you are reading this now from your computer screen except its late in the evening and all the lights are turned off. Now sit there and just read this for a while and pretty soon some strange things start to happen. The screen starts to look bigger, and all the sudden you start to see a glowing haze around the monitor and your eyes feel more agitated and strained. You also start to notice that the contrast between light and dark appear to encroach on each-other and the edge of this contrast begins to take on a "softer" appearance.

This phenomena is also known as "irradiation" which occurs with your eyes and is what actually damages the delicate features we see on the Moon and planets and even multiple stars in some cases. You are in effect, experiencing too much contrast now. Do your eyes a favor. Set up your refractors or better yet, your aperture packed reflector and go back into your house and turn up the lights to full. if it's dark outside, then do everything in your power to "prevent" your eyes from dark adapting.

After ten or fifteen minutes of being under white light, go back outside and look at the planets in the eyepiece and see the immediate results. If you want to experience the most amazing contrast, then this will be the time. Since your eye is not dark adapted yet, the background you see around the the planet will appear jet black! with a hard, outlined planet in the center provided your seeing is also good. The reason that this particular effect of contrast is perfectly fine is mainly because your eyes are not dark adapted yet, nor should you want them to be.

After a minute or so goes by, your eyes slowly and tragically begin to dark adapt again. The background starts to look more gray and the limbs of the planets don't appear to look as sharp anymore. You are now experiencing contrast saturation. White is now encroaching on black.

So you say, why not just use an ND filter? You can, but it still isnt necessarily better because it still does not prevent your eyes from dark adapting. The key is not to dark adapt. So, what's another way around all this? The answer is more light pollution. The more you have, the less saturated the Moon and planets appear. This in turn helps prevent your eyes from dark adapting but more importantly, helps reduce the contrast you appear to see between the sky and the planets themselves. Your color perception can also be rewarded too during this process.

When you view planets and your eyes are dark adapted, you are doing nothing but destroying the Moon and planets you see at the eyepiece, particularly with big reflectors and fat diffraction spikes. Light pollution helps hide these unwanted gremlins. My opinion is this.

It is far better to leave some ambient lights on around you but just make sure you are not shining them into the eyepiece or down the optical tube. Continually make efforts to look at white light in order to prevent your eyes from dark adapting.

Stephen O'meara, one of the greatest planetary observers ever, commented that most of his finest planetary images occured during twilight or dawn while barely any other stars were even visible. This is when you should be viewing the planets. You are in effect, viewing under the ultimate light polluted sky. All these tricks will help keep your Moon and planets on a healthy diet.

Conclusions:

1.) Avoid dark adapting as much as possible.
2.) Try to view your targets at twilight or dawn, while barely any star is visible.
3.) Keep some ambient white lights on and make sure the heat coming from them is downwind or away from the optical path.
4.) Use white lights to read any lunar charts or planetary charts, not red.
5.) Realize that light pollution in this particular case is actually a better thing, not a bad thing.
:)

#2 zjc26138

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Posted 25 April 2010 - 04:45 PM

I can't argue with your logic. I'll have to try this next time I'm doing some planetary observing. :bow: :)

#3 GlennLeDrew

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Posted 25 April 2010 - 04:49 PM

Your thesis does hold water when the objects under observation are sufficiently bright, such as the Moon, the planets at least out to saturn and stellar objects. For such things as the deep-space 'fuzzies', there can never be enough contrast for our liking--dark skies are King.

Comparing a TV image with a live view as regards contrast is fallacious. For starters, the dynamic range of a display device is many orders of magnitude less than that of the eye. More imprtantly, on a TV too-high contrast tends to push the more subtle shadow details down to below the floor of the device's range, which we call black.

#4 mikey cee

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Posted 25 April 2010 - 05:12 PM

Hurray for Daniel! :bow:I've always thought along these same lines. Some people think I'm nuts. First off who gives a rat's pitutty and secondly I feel kind of pityfull for them. I never could quite explain it but I feel more at ease with my urban sky than out in the boonies. Seems like when I'm out in the pitch black darkness I'll feel overwhelmed and lost. Here at my urban observatory I feel an odd calmness. Sure when I first had my 8" f/13.3 Brandt mounted 30 years ago in the countryside I could see all M objects with ease. But fuzzies soon got to be shall we say somewhat blase'. Planetary and lunar were viewed only several times a month so hitting the "perfect" nights with them was like hitting a lottery. Now I can be observing them "all" of the time from my home within 5 minutes. Many more chances of good nights with double stars etc. when learning to accept urban skies that's for sure. Many globulars and brighter open clusters for me really couldn't look much nicer than here...I've just acclimated myself to enjoy the less "harsh" views. Again thanks Dan for helping me feel more at ease with what I ultimately had to decide on for myself when I built my present observatory in 1985. :smirk: ;)Mike

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#5 t.r.

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Posted 25 April 2010 - 05:51 PM

Stephen O'meara, one of the greatest planetary observers ever, commented that most of his finest planetary images occured during twilight or dawn while barely any other stars were even visible. This is when you should be viewing the planets.


I've been doing it for years and my best view of Saturn came in an orange-filled dawn sky! It also seems at these times the atmosphere is most stable. Any progress on designs to artificially illuminate a refractor lens to accomplish this? This was rumored a few years back...

#6 GlennLeDrew

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Posted 25 April 2010 - 06:10 PM

About adding illumnation within the instrument. It's not necessary to make something to fit the objective. It's easier and more economical to add something of standard size near the eyepiece. A well made beam splitter could do the trick, with the 45 degree face re-directing a diffuse, field-filling glow, adjustable in both brightness and color. Simple!

#7 t.r.

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Posted 25 April 2010 - 06:31 PM

Okay, now which color is optimal?

#8 GlennLeDrew

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Posted 25 April 2010 - 07:04 PM

There is probably no one optimal color, as it would likely depend on the color of the object being observed. And I'd think that it most cases one wouldn't want a very 'pure' color, but rather more subtle variants. For a first stab, perhaps the safest (and easiest) would be simply a neutral white, as could be obtained with a white LED.

If color is desired, an illminator made from, say, three LEDs, one each of red, green and blue, could be made so that the relative intensities could be continuously variable and hence result in any desired mix.

#9 Jon Isaacs

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Posted 25 April 2010 - 07:59 PM

Daniel:

All good stuff. Jupiter at dusk a couple of years ago in my 16 inch... The colors were amazing. This morning, Jupiter was low on the horizon over the desert and climbing into the sunrise. The seeing was unstable but I was surprised at how much detail I could see.

A couple of points:

-Often the seeing in the mountain where the skies are dark are is poor, I find this is particularly true if one is on the east side, I attribute this to the tumbling of the prevailing westerlies over the ridges. The seeing is often quite good from my backyard, I am close to the ocean and the temperatures are mild.

- One needs to be an opportunist. When the skies are dark, look at Galaxies and DSOs. When the moon is up or the skies are light polluted, spend time on the planets and double stars.

I have heard the recommendation that one leave a light on nearby when viewing the planets... For many of us, this requires no effort. :foreheadslap:

Jon

#10 djeber2

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Posted 25 April 2010 - 08:10 PM

Thanks for this post Daniel. During this time of the year (with longer days and shorter nights) I have tended to do some lunar and planetary viewing during twilight because of time constraints (how late it is when it gets dark and having to get up early the next morning for work). It is nice to now know that this is actualy a good time for lunar and planetary viewing.

#11 Cobalt5120

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Posted 25 April 2010 - 08:24 PM

I'll tell you what, you made me rethink my astronomy hobby and the direction I will pursue. I am where I am, and perhaps I need to quit wishing I were in the darkest skies on earth and start exploring and appreciating those things that are available to me right here and now. Doesn't mean I won't treat myself to a nice dark sky vacation or star party some day, but I really do need to make the most of what I do have, And the way you described it, it's really not that bad.

Like Dorothy said, "there's no place like home".

Thanks for the wake up call.

#12 wb9sat

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Posted 25 April 2010 - 08:28 PM

Here's some food for thought for those who are plagued with light pollution. If you're into astrophotography or want to get into AP, light pollution has very little to no effect when using narrowband filters.
Bill

#13 PlanetMan

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Posted 25 April 2010 - 08:49 PM

We use this to good effect when our club holds star parties for local schools, especially during daylight savings time. We start our SS observations as soon as we can pick out the objects. BTW, I also think the moon looks stunning adjacent to a dark blue evening sky.

#14 mikey cee

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Posted 25 April 2010 - 10:16 PM

I've always felt that air polution over cities and inversion layers etc. etc. helped calm down seeing conditions. Even the moon light no longer bothers me if I have a ready made list of doubles to go for. Besides when it's really dark I can barely see my equipment but under urban sky glow I get a double whammy. Yessiree folks I get to sit in my observing chair and view my scopes outlined against the night sky. You see I'm fortunate enough to not only have nice stuff to look thru but also to look at. I can have my cake and eat it too!! :grin: :grin:Mike

#15 mountain monk

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Posted 25 April 2010 - 11:18 PM

Quite interesting--if you wish to see a tree; but if you wish to see the forest--best get thee to a dark sky.

mm

#16 galaxyman

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Posted 26 April 2010 - 12:21 AM

Well unfortunately I'm a little shall we say not fond of any astronomer (particularly amateur) who decrees "light pollution can make things better". :mad:

Of the 42 plus years of astronomy and a leader of this fight (light pollution) since 1982, It is a bit disheartening to read this post.

You cannot begin to imagine how long and tough of a road this has been for me and many others out there, just to make some headway. All astronomers when given the opportunity should speak about the detrimental effects of poor outdoor lighting and the effect it has on the night environment.

In fact the issue here is planetary only observers can basically observe with good results about anywhere they desire, whereas the rest of us must not only endure the monthly lunar bright sky cycle (1st quarter to last quarter), but also the bright skies of manmade light. In other words about 10 to 14 days or so of the month able to go to a dark site to observe, providing we get a good clear night. So the DSO guys do have it much tougher.

Planetary observing needs a lot less in terms of sky quality then us DSO observers.

What has happened of the last 5 decades is that amateur astronomy has change in a number of ways. The biggest I feel is with deep sky observing...why?

Well years ago most amateurs did not have near the size and quality of scopes as today, so back then most took up planetary, double star, lunar, and variable star observing. Some did DSO's but mostly only a handful of backyard astronomers and only observe a handful of deep sky objects (mostly M objects). You can find in some used book stores, astronomy ( for amateurs) observing reference books (I still have a couple) that were dedicated mostly to solar system objects, double and variable stars, with only a taste of DSO's.

Today of course with larger and better telescopes and eyepieces, the ability to see many objects beyond the solar system is astounding. Many show detail that for amateurs to see 5 decades ago, he or she needed to open a book with observatory photos or the end credits of the Outer Limits program.

So for those new to this great hobby or lifestyle I must say that by far the biggest threat to us is light pollution, for it is one of the larger factors why amateur astronomy is not growing as it should.

So instead of just saying light pollution helps astronomical observing of the planets, then I have another way. Shine a small flashlight in your eye then observe Jupiter or maybe stare at the Sun a few times before sunset.


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#17 BlueGrass

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Posted 26 April 2010 - 12:26 AM

Interesting thread. Most of us have been 'indoctrinated' with the Dark Sky is King philosophy. I've never given it much thought as to whether it's 'true' since logic tells us 'Yes, it must be true". Anyone who's been under stellar dark skies knows what I mean. The sheer depth and number of objects easily visible is overwhelming. I understand the rational given to aid viewing of brighter objects and planets.... but given a choice? Suburbia or dark sky?

#18 blb

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Posted 26 April 2010 - 12:57 AM

Dark sky is King when viewing faint fuzzes. When I look at the planets though, some of my best views are at sunset when the sky is still blue. Blue sky is the best filter allowing me to see more detail clearer than two hours after sun set. On the best of nights at home I can only see to magnitude 4.0 to 4.5 and I found that while doing the Astronomical League's Double Star Club, all that light pollution did not hinder me on double stars. On the other hand faint galaxies and clusters, as well as nebula, except for planetary nebula, are only a poke and hope. You can only see the brightest of galaxies and clusters. For these you definitely need dark sky.

Buddy

#19 Scopyfrank

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Posted 26 April 2010 - 04:25 AM

Hi,
thank you for "opening" my eyes.
After reading you, I must admit to have better scrutinized Rupes Recta on the moon last day at dawn than in the dark. To much light "overexposed" the shadow.
On the other side, I also appreciate highest darkness for the shadows some mounts cast on the surface - the shape is sometimes better visible.
I will certainly experiment your way of doing next time on planets (currently, Saturn is "going up" and in a few months, it's Jupiters' turn).

#20 ukcanuck

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Posted 26 April 2010 - 04:59 AM

What an interesting idea for a thread, and well done for Daniel for having the nerve to write it.

I live in South London, UK. :tonofbricks: The only place locally I can think of that would be more light polluted is right in the city, where I used to enjoy catching glimpses of Deneb & Vega while walking to the train station (those were the only two I could see), then Orion as I walked across the Thames...

This is where I am in the world, and I'm not in a position to sell my house and move for the sake of gaining darker skies. I also have 3 high mounted sodium street lights within 100ft of my back garden, which I cannot get away from. After my son arrived, and astronomical time became a rarity, I found myself going outside less and less. I've only recently started venturing outside again, but struggle to get inspired by deep sky targets (this is not a comment on deep sky viewing overall, simply a comment on the conditions my light polluted area create). However, lately I have found planetary viewing and double star observing to be a more rewarding area to view.

I've never thought to intentionally spoil my dark adapted eyes. However, with so much ambient light, I can usually read the eyepiece labels without a torch, even if the street lights happen to be out of sight....so I don't really think I would need to.:grin:

Of course, when I can escape to a truly dark skies, I will marvel at the Milky Way (can't see it at all from London), and feel a pang of jealousy that I can't share these skies more often. Meanwhile, I find inspiration in hearing from others, like me, making the best of the situation that they are in. :cool:

Thanks for writing this Daniel.

#21 drksky

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Posted 26 April 2010 - 09:39 AM

I have to agree with galaxyman here. Amateur astronomers extolling the virtues of light pollution is indeed a sad state of affairs. I can't say I enjoy peering at faint fuzzies through the eyepiece, but I do enjoy photographing them and I don't think there's anything more breathtaking than seeing a dark sky unmolested by light pollution.

Like the health care debate, this is a perspective of "I have mine, don't care about you".

And like galaxyman said, there are better solutions to increasing your contrast under a dark sky other than ruining it for everyone else.

If you like solar system observing from in a city because the light and air pollution make for better conditions, fine, but don't cheer on those who propagate them.

#22 mikey cee

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Posted 26 April 2010 - 10:35 AM

Whose extolling the virtues of city air pollution?? I never said or meant it was way better. But it isn't as restrictive as you want to believe. And "we" aren't wanting to make our situation expand to make you Deep Sky folks irritated. I've learned to make the most of it and learn to enjoy it....because for me in my situation I can't just pack up and run away to avoid what we've all helped create. :smirk:Mike

#23 Cobalt5120

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Posted 26 April 2010 - 11:55 AM

Galaxyman and Drksky:

I don't see anything in the initial post that advocates "ruining" anything for anybody. I took the point of the article as being that there are "some situations" where the presence of light pollution actually helps and where dark adaptation actually hurts. I don't see that a rallying cry to have cities and towns light up the sky any more than it already is.

Personally, I despise light pollution. I wish the skies where I live were pitch black, because my preference is DSO's. But they are not. So the only alternative is to try and look at the bright side of the issue (pun intended) and realize that the situation I find myself in doesn't ruin EVERY aspect of astronomy and to make the best of what I consider to be a bad situation.

#24 Scott Rose

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Posted 26 April 2010 - 04:32 PM

I observe from a light polluted suburb and have found no difference in observing the moon, planets, or double stars from where I am or an hour drive to a darker site. For DSO, sure you want darker skies, but that is only part true. I do absolutely fine with open clusters and globs. Nebula and galaxies are challenging, but not my favorite visual targets ( like them better for AP). And if you read Daniels post carefully, he is NOT throwing his dark skies in our face, as he is building is observatory in a light polluted area. I appreciate his thoughts and observations. He is presenting material for discussion which is a good thing. It gets tiring about reading what scope is better or what scope should I buy. This is refreshing and thought provocing. Daniel, just remember.... the guy who said the earth was round got a lot of *BLEEP* from those who swore it was flat.

#25 galaxyman

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Posted 26 April 2010 - 08:54 PM

Galaxyman and Drksky:

I don't see anything in the initial post that advocates "ruining" anything for anybody. I took the point of the article as being that there are "some situations" where the presence of light pollution actually helps and where dark adaptation actually hurts. I don't see that a rallying cry to have cities and towns light up the sky any more than it already is.

Personally, I despise light pollution. I wish the skies where I live were pitch black, because my preference is DSO's. But they are not. So the only alternative is to try and look at the bright side of the issue (pun intended) and realize that the situation I find myself in doesn't ruin EVERY aspect of astronomy and to make the best of what I consider to be a bad situation.


Hi Larry

What I find the problem with this issue is the blasé attitude most amateur astronomers take the LP issue.

So what do I mean about that comment?

Well, I've been involved with the LP issue longer than the IDA. Being it writing articles or newspaper, radio, and magazine interviews, and doing public presentations with audiences from 15 to 3000 people.

In all this what frustrates me the most is that a small minority of us that actually gets involve with this issue, and that is sad. In fact I've seen a step up of non-astronomers getting involved, but they also need our support for more success.

Now what I find funny here is if you read my prior post, you may determine that the words "faint fuzzy" is something from the past, and yes even galaxies. With the advancement of the modern amateur telescope and eyepieces, many of these objects are far from faint fuzzies, and show a wealth of detail when viewed from good dark site.

For here in the refractor forum, the unbelievable growth of good large refractors owned by the amateurs today is not subtle. So yes, many like me do love the DSO views from a 4"+ refractor. The late Walter Scott Houston used a 4" refractor under great dark skies for many of his observations of DSO's.

For me, though I do own 22" and 12.5" dobs, my refractors do lots of DSO observing in particular the APM 8" f/9. This scope from a dark location shows detail in many more DSO's then the number that one observes the very few SS objects. Also as I stated before this scope (and me) observed a number of Arps in the past couple years, and a some in detail. Couldn't quite do that back in the late 60's with my 60mm refractor. ;)

Remember one of...no thee biggest threat to the growth or interest of astronomy is light pollution.


Karl
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Homemade (Parks Optics) 12.5" F/4.8 Dob
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ES 6" f/6.5 achro. New
Orion 4" f/6 Refractor. Also not bad for an achro
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