LP Filters

[blueroom]

I bought a Skywatcher LP filter a few weeks ago, but having used it a few times it hasn't improved my views of the night sky, infact it makes it slightly worse.

Now I read on here somewhere that LP filters don't improve the view of stars and planets, so my question is what's the point of a LP filter? would it improve the view of nebulars or galaxies?

Thanks

[umadog]

Planets are bright and so aren't affected by light pollution. LP filters and planets don't mix. LP filters work best on narrow-band emitters like nebulae. They don't work on stars or galaxies and will, as you notice, make things worse. The UHC and OIII filters are the most effective for nebulae. The more broad-band LP filters (which seems to be what you have) are less radical and result in less of a contrast boost.

Do some reading on filters by searching on Google, that way you'll know what to expect. These links, for example, should answer most questions:

http://www.knoxville...lprfilters.html

http://www.prairieas...w-band-filters/

http://www.astronexus.com/node/4

Also, there was a question about this topic just a few days ago:

[blueroom]

Ah that's very useful, thanks

[LukeSkywatcher]

If its nebulae you want to improve upon, then a UHC filter would be of more use as it covers a wider range of nebulae then the OIII filter.

Simply put: UHC filters make the already visible nebs MORE visible and OIII make the invisible nebs visible.

[E621Keith]

What has been mentioned above describe narrow band filters. Nebula emits light at very specific wavelengths and narrow band filters, such as OIII and UHC, only allow those wavelengths to pass. This can significantly improves the contrast between the nebula and the background skies. Narrow band filter cannot be use on broadband objects such as galaxy and globular clusters.

I believe what you bought is a broadband filter. Broadband filter are designed to block street lights. Low pressure sodium and mercury street lamp emits light at very specific wavelengths and broadband filters blocks these. Broadband filter cannot block white light from houses, cars, and LED street lamps, so they are much less effective than narrow band filter. However, unlike narrow band filters, which only work on nebulae, broadband filters work on most objects, including stars and planets, by dimming the sky background. Whether they are worth it depends on the amount of orange street lamps in your area.

[umadog]

Here is a comparison of broad and narrow band filter pass-bands: http://starizona.com/acb/basics/equip_filters_lpr.aspx

More info on filter types: http://www.cloudynights.com/item.php?item_id=63

Here is more info on a specifc broad-band filter:

http://www.cloudynights.com/item.php?item_id=2389

Here is a comparison of different filters for different objects:

http://www.cloudynights.com/item.php?item_id=1520

The take-home message is that any nebula that is helped with a broad-band filter tends to be helped more with a narrow-band.

Reports on the effectiveness of filters on galaxies or star clusters indicate that they help only marginally. If you want better views of those objects than a dark sky trip is pretty much your only option.

[E621Keith]

The take-home message is that any nebula that is helped with a broad-band filter tends to be helped more with a narrow-band.

Reports on the effectiveness of filters on galaxies or star clusters indicate that they help only marginally. If you want better views of those objects than a dark sky trip is pretty much your only option.

Totally agree with this. Nothing beat dark skies when it comes to galaxies. Broadband filters may help a little, but not much, and certainly not to the extent a narrow band helps nebula.