WOW...Sky Watcher LP filter!

[swlloyd3]

I don't know why I haven't actually held this filter up to my street lights after owning it for a couple of months but anyway... gave it a go tonight and I cannot believe what it does!

Its like the street light glow just 'disappears' it really is a strange thing to look through truly amazed!

anyway just thought I would share my story guess it blocks out the right kinda light pollution for me in Chester anyways!

Ste.

[laser_jock99]

When they change over to those wonderful new white LED lights it won't work any more........

[Carbon Brush]

I remember buying my first LP filter 2nd hand for what seemed a lot of money. Accross from my house was a bungalow with white fascia boards, and a white caravan. All lit nicely by the (not too bright) street lights. Looking through the filter, everything white painted just vanished. It was amazing.

[swlloyd3]

Yeh it was the same for me a brick wall on the street glowing orange from the lights just went dark

That is true about the white LED lights are they less light polluting in general? Also are they just as easy to block out by developing new filters?

Ste.

[Carbon Brush]

Sorry but white led lights are bad news for light pollution.

First they emit a wide range of wavelengths, so are impossible to filter. Old fashioned sodium and mercury lights by comparison emit specific wavelengths that are relatively easy to filter..

Second, because they use much less electricity than other lighting, there is the tempation to put more of them everywhere.

The only good things for astronomers and led lighting are that it is easier to make fittings that shine directionally, and they are expensive to buy. But this not much help as prices are dropping. Money spent on 'green' items is viewed as good. So they will (in my view) proliferate.

[swlloyd3]

Very bad news about the LED lights then

[great_bear]

Its like the street light glow just 'disappears' it really is a strange thing to look through truly amazed!

Well... That's all very well, BUT - for many (most?) people "skyglow" is not pure streetlamp light, but a mixture of advertising billboards, office blocks, road signs, nightlife etc. etc.

Against such a backdrop, the Sky-Watcher LP filter does *nothing* of any note unfortunately

[chiltonstar]

Mine doesn't even do anything on the streetlights as these are mainly high pressure Na-Hg, and therefore have emission right across the visible region - a quasi-continuum. An AK47 would be a more effective LP aid....

Chris

[Gregski]

My impression was that, rather than specifically blocking sodium and other known light polluting wavelengths, LP filters only 'let through' the wavelengths associated with astronomical objects. Granted, pure white light emission encompasses all wavelengths, including astronomical ones, but a decent LP filter should still help the contrast.

Greg

[Stephen]

Someone posted this for me, don't know if it helps the conversation

[engstrom]

I just tried holding it up to a streetlight. Wow indeed! It really does bin off all the orange light! Hopefully tomorrow will be clear so I can get to try it on my 'scope.

[great_bear]

My impression was that, rather than specifically blocking sodium and other known light polluting wavelengths, LP filters only 'let through' the wavelengths associated with astronomical objects.

No, you're thinking of Deep Sky / Ultrablock style filters - these work as you describe. LP filters *are* designed to block light-polluting wavelengths only and are much more gentle - but (as I say) useless in practice on "city" pollution; although some may be lucky enough that their local pollution is in the right waveband(s)

[mag10]

No, you're thinking of Deep Sky / Ultrablock style filters - these work as you describe. LP filters *are* designed to block light-polluting wavelengths only and are much more gentle - but (as I say) useless in practice on "city" pollution; although some may be lucky enough that their local pollution is in the right waveband(s)

Can someone help a newbie on this?

After reading this post, I immediately looked at a sreetlight through my deep sky filter (I don't know what it is because it's branded under my local astronomy shop's name).

I was told it's "like" an OIII filter. When I looked at the orangy coloured streetlight (sorry, my chemistry is basic to nonexistent), it did not make it go away. It just turned the light green.

What do I have and what is it good for?

It's 1.25" dia. and I paid roughly 24£ for it.

Thanks for any help.

[Gregski]

Thank you for your correction Great Bear. I had confused the two. My SW LP does a reasonable general job on DSOs from my London location although I could with more aperture to compensate for the light loss.

Greg

[great_bear]

What do I have and what is it good for? It's 1.25" dia. and I paid roughly 24£ for it.

Sounds like it's a "Narrowband" filter, and £24 is a good price!

Presumably it looks like a little mirror, yes?

These filters are for looking at nebulae. Try it out on the Ring Nebula. You should find it makes the surrounding area very dark, but leaves the nebula nice and bright.

If you use it on the Orion nebula you'll see more detail there.

[russ]

Second, because they use much less electricity than other lighting, there is the tempation to put more of them everywhere.

Or simply crank them to the max in order to recreate pure daylight conditions in the dead of night. These lights (in Hampshire at least) are incredibly bright, i'm trying to convince the Hampshire chief Lighting Engineer that they could easily be dimmed by 50% and still do their intended job (which isn't 24/7 daylight conditions). His reply is we dim them by 25% after midnight, which is still too bright.

[great_bear]

The dazzling video billboard on the Hammersmith roundabout is a real shocker too...

[hemihaggis]

Astronomik cls filter .does what it says on the tin , outstanding , best money i have ever spent on an item for this hobby .

[mag10]

Thanks Great Bear.

Sorry for not replying sooner. The curse-that-must-not-be-named seems to have (finally) lifted and conditions have been pretty good (well, for the moon, at least).

So now, I'll look at LP filters (since what I have is'nt one).

Heaven knows I need a little LP protection!

Thanks.

[Carbon Brush]

Hopefully not of topic.

Replying to Russ' on dimming led lighting.

Eyes (and ears) tend to have logarithmic response. That means if you half the signal power to them, they pick up only a slight reduction.

So a 50% light dimming would not be a bad thing.

But, for technical reasons, this is difficult with sodium based lighting.

No technical problem though to LED lighting. Just public perception.

[great_bear]

So now, I'll look at LP filters (since what I have is'nt one). Heaven knows I need a little LP protection!

For nebulae, the filter you have is the "ultimate" light-pollution filter but they're not effective for any other astronomical object.

With standard LP filters, definitely try-before-you-buy since for many people, the filters merely dim everything and aren't much help overall.

For some people however, they are effective against their local light-pollution. So it's not possible to generalise about whether the standard LP filter (neodymium-style filter) will be of use to you or not.

[obscura]

Bought a SW LP filter earlier this year and it cut out the sodium lamp light brilliantly. Since then the Hampshire council has replaced them all with white light, presumably LED. From what I am reading above, my SW LP filter is next to useless now.

Can anyone recommend a best fit filter for these white light lamps? DSO imaging is my objective. I realise white light is covers the visible spectrum. I could move house I suppose away from Hampshire.

[Gregski]

Moving house for your hobby is pretty hardcore - I salute your devotion to DSOs! However, friends of mine live on Lymington, Hampshire and their skies are pretty dark I'd say.

Greg

[virtualpilot45]

Is there any chance of someone taking a pic of a street light, once without filter, then with lens covered by filter? I'd like to see the difference in case I ever were to try to mitigate my horrible orange skies

[Sp@ce_d]

Is there any chance of someone taking a pic of a street light, once without filter, then with lens covered by filter? I'd like to see the difference in case I ever were to try to mitigate my horrible orange skies

There's been a fair bit of discussion here about filters. I remember one thread somebody took pictures. Think their front door featured but I cant find it. This one has a street light comparison shot. http://stargazerslounge.com/equipment-discussion/115239-light-pollution-filters-compared.html and a review of 3 types here.. http://stargazerslounge.com/equipment-reviews/65445-light-pollution-filter-review-part-1-a.html

I also find a google search is sometimes better for finding stuff here than the forum engine. I use the SW filter on my imaging setup. That made a welcome difference but does leave a colour cast. Easily delt with in processing.