Filters For Light Pollution - Visual Observing...

[Guest]

I'm not quite sure where to post this, so here goes... 

For visual observering in a light polluted area, what filters would people recommend? 

My area has mostly white LED street lights, but it's a bright yellow sodium one at a nearby garage site that is giving me most problems, I believe. There are some Double D CFT bulkhead lights that are causing frustration too! 

[mikeDnight]

Others may have much more experience of light pollution filters than I have, but I've found that the greatest problem these lights cause is at the eye/eyepiece interface. By blocking this interference at that point, you can greatly increase your eyes sensitivity to faint objects. A dark blackout blanket over your head and eyepiece really can work wonders. 

[RT65CB-SWL]

Traditional light pollution filters were OK on the old sodium street lights; but now as local authorities are now using LED street lights they are not so effective. If my memory is correct, LED's are higher up the blue end of the light spectrum.

You could try a neodymium and see it that makes a difference or you could try a UHC or O-lll filters. Though I would advise you to read this topic first... 

 

[Guest]

22 minutes ago, mikeDnight said:

A dark blackout blanket over your head and eyepiece really can work wonders. 

"Watch the birdie"! 🤣. Sorry, couldn't resist. 😉

[Stardaze]

17 minutes ago, Philip R said:

Traditional light pollution filters were OK on the old sodium street lights; but now as local authorities are now using LED street lights they are not so effective. If my memory is correct, LED's are higher up the blue end of the light spectrum.

You could try a neodymium and see it that makes a difference or you could try a UHC or O-lll filters. Though I would advise you to read this topic first... 

 

There is more blue in the spectrum of LED lighting for sure, but a single light fitting at a local garage won't affect the overall light pollution in your area, but it will contribute to the whole of the perceived darkness overhead as a contribution of the whole. If it does fall into your peripheral vision, then the above would work. That's more down to stray localised light causing a reduction in contrast and/or affecting your night vision at the eyepiece. 

It is interesting with the move to LED. In theory, as more traditional light sources are changed, the effect of traditional 'sky glow' filters should become less effective. The wavelengths of sodium lighting are as attached, you can see the spike in the blue for LED.

Edited June 16, 2020 by Stardaze

[TerryMcK]

I use the IDAS LPS D2 for astrophotography to minimize the effects of LED light (also works onsodium, mercury and tungsten) and can confirm it works really well. However that filter is designed for cameras only and when you look through it visually it impairs a greenish tint to everything so not really confident that is what you are looking for.

[Guest]

19 minutes ago, Stardaze said:

There is more blue in the spectrum of LED lighting for sure, but a single light fitting at a local garage won't affect the overall light pollution in your area, but it will contribute to the whole of the perceived darkness overhead as a contribution of the whole. If it does fall into your peripheral vision, then the above would work. That's more down to stray localised light causing a reduction in contrast and/or affecting your night vision at the eyepiece. 

It is interesting with the move to LED. In theory, as more traditional light sources are changed, the effect of traditional 'sky glow' filters should become less effective. The wavelengths of sodium lighting are as attached, you can see the spike in the blue for LED.

Here's an idea of what I'm up against. The video is the communal back garden, in which you can see the Sodium light over the fence and the two bulkhead lights.  The photo is the front garden, showing the LED streetlights. They are very white. A hospital near me has LED street lights that seem to be creamy white! 😯

I can turn off one bulkhead light and mute then other, a bit. 

[TerryMcK]

I feel your pain

[johnoelliott]

Everyone has their own opinion of which ones work best so my solution to the problem was to buy a 5 position manual filter wheel and put in UHC, Deep Sky, Hb and Oiii filters leaving one empty.

I can quickly go back and forth comparing them to see which ones work best for the target I'm looking at

[johnturley]

4 minutes ago, johnoelliott said:

Everyone has their own opinion of which ones work best so my solution to the problem was to buy a 5 position manual filter wheel and put in UHC, Deep Sky, Hb and Oiii filters leaving one empty.

I can quickly go back and forth comparing them to see which ones work best for the target I'm looking at

This is exactly what I did as well.

John 

[Guest]

33 minutes ago, johnoelliott said:

Everyone has their own opinion of which ones work best so my solution to the problem was to buy a 5 position manual filter wheel and put in UHC, Deep Sky, Hb and Oiii filters leaving one empty.

I can quickly go back and forth comparing them to see which ones work best for the target I'm looking at

Don't you have to take out a second mortgage to cover the costs of all those filters? 🤔😯

[Graham Darke]

There are lots of things you can do. Filters are just one part of the strategy. Here are my tips for observing from a light polluted location. 

Cover or block out any local sources of light pollution on your property and around it. It is easy to make a basic screen from bin liners and garden canes to put up around your telescope. The reason this is so important will become clear. Artificial lighting has two effects on our observing.

The first effect is direct light pollution, i.e any light sources which shine directly onto our observing area. It is very difficult for your eyes to get properly dark adapted if you have a bright light source in your field of vision. When I say difficult, I mean impossible. So get yourself into a spot where you can’t see direct sources of light pollution and stay there. I have found that this does help a lot. The old cloth over the head trick works fine until you come to move the telescope to another target. The moment that bright light shines in your eyes then you’re back to square one with your night vision. 

The second effect of light pollution is the glows it imparts on the sky. This is where filters will help. UHC and O III filters are most effective. 

Observing objects that are higher up in the sky helps. Those lower down in the murk are more affected by light pollution.

Observe objects that are less impacted by light pollution. Not just the moon and planets, but double stars, planetary nebulae and many clusters will stand up well. 

Keep your eyepieces clean. It is possible to lose a magnitude in performance with dirty eye lenses. You really don’t need this when fighting light pollution. 

[Stardaze]

2 hours ago, merlin100 said:

Here's an idea of what I'm up against. The video is the communal back garden, in which you can see the Sodium light over the fence and the two bulkhead lights.  The photo is the front garden, showing the LED streetlights. They are very white. A hospital near me has LED street lights that seem to be creamy white! 😯

I can turn off one bulkhead light and mute then other, a bit. 

That does look a nightmare. I have two street Lights either side of my garden and I have to block them out with careful positioning behind a tree and fence. I’d be tempted to pop a black bag over those bulkheads for the time you’re observing. If really fed up with them, and they’re still 2D fluorescents ie not LED, I’d unscrew the covers and take the lamps out 😁 I work for a lighting manufacturer so that actually wouldn’t be an issue, but appreciate that’s taking things quite far, but if they’re quite accessible, it’s easy to do. Very tricky all round, they will hamper your night vision more than anything. If ever I have to move around during observing, I’m constantly trying to avoid catching sight of one of the street lanterns. The other killer is when the wife switches on the kitchen light mid session. There’s light to be blocked all round, guess it’s what’s practical. One of my spots is relatively tight to a fence.

Edited June 16, 2020 by Stardaze

[Stardaze]

The ultimate solution for those bulkheads, and appreciate this may well be completely over the top, is that there are gear trays available (we as a company do do them) that can be controlled by a remote control. Obviously that would require an electrician to pop them in at a cost (unless you know a friendly one, it’s not a big job) The remote can turn them on/off.

IF, they’re not LED and still 2D fluorescent, there are retro-fit LED lamps available with microwave sensors incorporated which are more sensitive than PIR. You can set the time delay period and they will stay off for a period or be triggered whenever you wave at them. Just an example here: https://www.ledbulbs.co.uk/products/kosnic-12w-led-2d-2pin-2d-cool-white-kled12std-2p-w40?variant=18181776965690&currency=GBP&utm_source=google&utm_medium=cpc&utm_campaign=google+shopping&gclid=CjwKCAjw26H3BRB2EiwAy32zhef4W_MXbMDgvC4ywE2NaCSXf10BuySkEWAJgilUwB_Ryc_0NGaq-BoC67UQAvD_BwE

They would just plug into the lamp holder like a fluorescent lamp would, so very simple and you wouldn’t need an electrician. 
 

Edited June 16, 2020 by Stardaze

[Zermelo]

Also remember there are two "ends" to the problem. You want to try to cut out as much of the light that shouldn't be there, but you also want to let through as much as possible of the light that should be there. The characteristics of the first of those is fixed, depending on the pollutants in your environment (and as others have said, LEDs are difficult) but the second is variable according to your current target in view. You can only ever cut out light with a filter (from the target object and the pollutant), but the aim is to selectively remove the right wavelengths so as to improve the contrast between target and background, even though the image as a whole is dimmed.
For nebulae in particular, a filter that does this trick best for one object may not be the best filter for a different object, because the spectra differ. People have spent a lot of time comparing lists of objects with different filters and made recommendations, e.g.
https://www.prairieastronomyclub.org/filter-performance-comparisons-for-some-common-nebulae/

 

Edited June 16, 2020 by Zermelo
typo

[Louis D]

4 hours ago, merlin100 said:

"Watch the birdie"! 🤣. Sorry, couldn't resist. 😉

You jest, but lots of folks swear by these observing hoods:

[sputniksteve]

Is nobody going to say anything about that car?!

 

 

 

[TerryMcK]

Same vintage as Supercar TV programme from the early 1960s

[johnturley]

12 minutes ago, sputniksteve said:

Is nobody going to say anything about that car?!

 

 

 

Humber Sceptre I think.

John 

[AstroMuni]

@merlin100 If you are facing the street with all those streetlights then a screen between your scope and the lights might do the trick. This would somewhat restrict your ability to view objects closer to the horizon but otherwise would work !

An old tent also may do the trick 🙂

Edited August 6, 2020 by AstroMuni