MnAstro Forums

New member first time posting a question. I live in the south metro and I swear every time I get my scope out my neighbors all turn their outside lights on. Looking for input on using nebula and light filters. What do I look for? Are there specific perimeters to look for? I have a 10 inch dob and 90mm refractor. Any guidance would be greatly appreciated
Thank you

Usually the issue with neighbors’ lights is that they shine in your face while you are trying to observe. There is no filter for your scope that will help with that. Your best bet would be to gently ask your neighbors if they would turn off their lights (maybe along with an invitation to look through your scope), or to erect something that will block the light, like a tall fence, or maybe a strategically placed tarp. Some people just drape a towel over their head.

Filters will potentially help remove the sky glow above you; darkening the background and increasing contrast. But they will also darken the objects you look at at least a little. The most common filters for visual observing would be a light pollution filter and an oxygen III (OIII) filter. The light pollution filter is designed to remove the most common wavelengths emitted by street lights (mercury vapor and sodium vapor), but with many or most streetlights now converted to broad spectrum LED, those filters don’t work as well as they once did. But if your sky is relatively dark (can you see the Milky Way when you are away from lights?) then the light pollution filters aren’t going to make as much difference anyway. Oxygen III filters are great for viewing many emission nebulas even under dark skies. They make dim ones pop right out. This is because most emission nebulas have a lot of ionized oxygen, even if most of their light is given off by hydrogen (hydrogen alpha).
OIII filters do not help with most star clusters. They darken stars significantly.

Thankfully, planets are bright enough that light pollution doesn’t really diminish the view.

There are a few famous nebulas, like the horse head, that look best through a hydrogen beta filter, but most people would probably wait a while before investing in one of those.

If you use a lot of 2” eyepieces, it may be worth the investment in 2” filters.

Maybe someone in the club would be willing to bring some filters over for you to try out. I’m sure someone lives nearby.

Here is a fairly good overview :
https://agenaastro.com/articles/guides/ ... tml#filter

I have used the lumicon UHC gen 1 filter at home in Woodbury. My site is Bortle 6 with SQM reading of 19.15. I found the UHC improved the view some on some objects but not all. I wouldn’t call it dramatic though. I usually save the nebulae hunting for darker sites.

I may switch to the Lumicon UHC Gen 3 next summer.

As Deane said, usually the problem with local light pollution coming from neighbor's lights is that they are shining directly in your eyes. Some folks have made makeshift light shields using rectangular frames from 1" or 1-1/2" PVC pipe and elbows, and fit them with black poly film plastic, just duct taped to the frame. You can make two or more of them, then set them up at an angle to each other so they can stand on their own, and use velcro straps (or more duct tape) to hold them together.

Or, as Deane suggested, take an opaque black cloth and drape it over your head while observing. But if you do that instead of a light shield, you'll inevitably glance at the lights and lose your dark adaptation over and over again.

Thank you for the input. I hav e a better understanding of the purpose filters serve.