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Filter for light pollution

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What sized filters do your lenses need...

The larger IDAS filters are quite expensive - I have the 77mm one and step down ribgs so that I can use it with most of my lenses...

You might want to consider a 2" filter to start with if your lenses use filters aroun 50-55mm with step up rings.. The reduction in aperture will alter the focal ratio and will usually clean up star shapes in the corners and edges of the frame...

IIRC Skywatcher have something which might work..


Sorry on the smartphone so it's not appeared as a clickable link...

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That I don't know, how do you find out?


I have a Nikon D3100 with the 18 - 55mm lens.


Can anyone tell me how I find out what size filter I need?

I have a Canon 18-55mm and should be the same as yours . Mine calls for a 58MM filter . Look on the front focus ring of your lens and it tells you . It should have a little zero with a back-slash through it . That's the semble for filter size .

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Hi thanks for the reply, have looked at the front focus ring but no sign of what you described, however I have found something on the side of the lens it has a circle with back slash and number 52. Would that be the filter size?

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The 2" filter has a 48mm thread.... Make sure you get the right adaptor you want to use a smaller diameter filter on a larger diameter lens there are two different types step up and step down and some sellers describe them wrongly...

Whats the rest of your setup? Mount etc...

This isn't the best LP filter out there but should help reduce skyglow ... at the fraction of the cost of one of the high performance filters... Have you got a pic of your LP?

This thread shows the difference the "cheap" skywatcher filter makes...


example with and without in the first post http://stargazerslounge.com/topic/234757-skywatcher-light-pollution-filter-first-use/?p=2541083

FLO have a pretty good returns policy if it doesn't do anything for you...


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The 2" filter has a 48mm thread....


At the moment I am just using the camera with a tripod (no tracking) completely new to this and is all trial and error at the moment, mostly error I may add ;o).

1st photo taken


And reason for LP.


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Thats what I suspected so there's no point in using a filter that will cut through the LP allowing 5-10 minute exposures that would need a tracking mount and auto-guiding...

I would try the cheaper option first :)


Thanks, will go for the cheaper option 1st. :laugh:

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