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Lewis H

What is the best filter for observing DSO's?

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I recently bought a Skywatcher Explorer 200p and live in London, so light pollution is a big problem, and have began looking into filters and am finding everything rather confusing as I am new to this. I have had my eyes on a Baader OIII filter, as it looks quite suitable and cheap (money is an issue, and I don't really want to be spending more than £75), but I am thinking that further down the line I would like to begin with imaging. Narrowband filters also caught my eye, but all of the different symbols and stuff confused me, and they are ALOT more expensive, so I guess the two questions I am asking are: 

Is the filter I have suggested good enough?

and

Should I invest in a narrowband filter, as they look better for imaging (although like I said before, price is a major factor in all of this, so nothing too expensive)

Thanks, and this is my first post, so I am sorry if I am repeating what others have said in separate discussions.

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LOL. I have been debating this with myself for the last day or so and have just placed an order with FLO for the above mentioned 1.25" OIII filter for visual use, literally in the last half hour.

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The OIII is a narrowband filter designed for viewing nebulae. I think the Baader Neodymium filter may be a better bet if you are looking to cut down light pollution for general viewing.

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Hello Lewis welcome to SGL.

You may find this article useful - http://www.prairieastronomyclub.org/resources/by-dave-knisely/filter-performance-comparisons-for-some-common-nebulae/

The topic of filters often comes up on SGL and the debate whether to buy a UHC or OIII filter. Although I have both types plus a H-Beta filter I would recommend a UHC filter to start with.

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Neodymium filter is the best filter for use in light polluted skies - I have a relatively darkish garden and always leave mine in, makes a big difference to me.  Then my OIII and UHC filters are great for use in dark sites - but don't help too much with any LP in my experience

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First off welcome to the stargazers lounge.

Observing nebulae from urban locations is largely going to be a disappointing experience TBH.

LP washes nebulae out very easily. Filters can help a bit, but TBH your better off either:

1~ Getting out of town

2~ Choosing a different object to observe.

Lastly. Line filters like the O-III require good dark adaption, without it you'll struggle to get the benefits. Getting your eyes sufficiently dark adapted from town is not easy.

Personally for my nebulae observing I opt for suggestion 1 above.

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Thanks everyone for helping, I am now thinking of opting towards gettign the Baader Neodymium Filter instead, that Mitchelln and CodnorPaul suggested

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I agree with Steve / swamp thing that getting away from the light pollution is by far the best way to get better views of deep sky objects. Filters will improve things slightly under light polluted conditions but won't work miracles I'm afraid.

Sometimes it's necessary to modify observing interests to better suit the conditions prevailing  :wink:

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Think you could get an assortment of opinions on this.

Certainly a dark sky is by far the better, as you do not have a problem to correct for.

I recall a post over on CN where the person said get an O III the rest do no better and cost more.

The poster was someone that wasn't prone to making ill thought posts.

Whether they were correct or not I have no real idea, don't have a filter. Also suspect that if I did I couldn't realistically say which would be "best" they are afterall different filters and do a different job.

If you attend any club - Baker St Irregular Astro (?), perhaps someone could let you attach one to your scope and try it. Say this as I suspect some people will prefer one to another as a personel aspect.

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As I say, I have a Baader OIII on the way from FLO. As said, I guess it's a bit of a personal thing like EP's, but I'll post my findings anyway when it arrives and I get a decent night.

I've gone for the OIII as others have commented on the great views that can be had from certain objects and I should hopefully have enough aperture to compensate for the narrow band pass.

There's always a bit of conflicting advice on these things, so I'm just going to give it a whirl and see what's what. After all, they're not £££.

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An OIII is an excellent filter investment.

From home, look for planetary nebula when they are positioned high and somehow try to ensure that your eyes are as fully dark adapted as poss. If you can get to a dark site, it will receive a lot more, worth while, use. 

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I use an O-III by Astronomik as my only DSO filter. It's expensive but very effective under my skies which have some light pollution but are pretty dark overhead. The Baader O-III is rather severe in my opinion as it's band pass width is narrower than most O-III filters. It's effective in larger aperture scopes but dims the view rather to much in smaller scopes, in my opinion. A UHC filter is generally thought to be more versatile than an O-III but the O-III is more effective on those objects where it does make a difference. The ideal situation is to have both of course !

These filters improve the contrast of nebulae and especially planetary nebulae and super nova remnants. They don't have any benefit for galaxies and clusters which are best viewed without a filter.

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Interesting topic.

Been thinking about get a filter for some DSO viewing with my C8 for when the planets disappear until winter.

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Interesting topic. Been thinking about get a filter for some DSO viewing with my C8 for when the planets disappear until winter.

If we get to meet up soon ant you're more than welcome to try my O-III filter. :)

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Cheers Steve, that would be great.

That is also a very big IF.  :laugh:

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I think that as said above, filters are very like eyepieces in that people have different opinions of them. I mainly observe from home with a fair amount of LP to deal with but I find a UHC filter very effective in improving the views of emission nebulae and some planetaries. I also have an Oiii and for some objects this is better but in general, I prefer the UHC. The Oiii gives more detail and contrast in the dark bits, the UHC seems to increase the extent of nebulosity you can see without dimming the view too much. So it depends which you prefer.

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You may find Mel has changed her opinion since that was written

Last time I observed with Mel and some others we observed the veil nebula using a 120ED we compared my Lumicon O-III and her UHC. No contest the O-III was way better in fact so much better that both of the other observers bought O-III filters soon afterwards. With no filter it was invisible from the site we were at.

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My advice to someone who lives in London and has recently bought a telescope would be to enjoy looking at the Moon and planets, and if they can see anything else then consider it a bonus. Any kind of filter will probably make little or no difference.

Nebulae filters (OIII, UHC etc) are great under the right viewing conditions, but their job is to transmit only a small amount of light, meaning they are highly reflective. At a light polluted site this high reflectivity can mean you end up getting ambient light reflected back up into your eye, so you see nothing. To use them under heavily light polluted conditions you may need to completely cover your head and the eyepiece with a cloth to block out light (a good idea at heavily light polluted sites anyway).

Nebulae filters only work on emission nebulae (e.g. Orion Nebula, Crab, planetary nebulae etc) - if they work at all. On anything else (e.g. galaxies) they just make everything dimmer.

"Light pollution" filters (neodymium etc) seem to work for some people, but light pollution in London is effectively white. To filter it out you would need something that could distinguish between white light made by humans and white light made by stars - and no filter is that smart. It may be worth a try, but borrowing someone else's would better than shelling out for something that might prove useless.

I own one filter - a Lumicon UHC - and on the few occasions when I use it at my dark site it works fine. I've successfully used it on Veil, Horsehead and many more emission nebulae. But the vast majority of DSOs are galaxies, and those are what I mainly look at, so my filter rarely comes out of its case.

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i will be getting an eyepiece and filter kit as I am on a budget much like you but I know I have to save a bit for the kit. Until then I am learning how to use my new scope with the current eyepieces and I have barely somewhat mastered using the barlow lens (almost got saturn in focus before I lost it ) Where I live , light pollution is also a problem but no so much that I can't make out any constellations or planets with just my naked eye. The street lights where I live give off a yellowish orangy glow which I think were done that way in attempts to cut down on some of the light pollution. Whenever there is a blackout and its night time though bet your stars I will be out side taking advantage of it.. I also go out of the city about once a month or so with my husband on camping trips.  


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I just use a cheap Skywatcher UHC filter from the edge of town. It makes M27 and M57 really stand out . I can also get bright parts of the Eastern Veil . It is great to make any brighter planetary nebula stand out. Also very useful on bright planets and that's through a refractor.

I'd definitely recommend it as a starter filter .

I borrowed a Lumicon narrow band last year to use with my 10" Dob. Under pristine dark skies on Northern Skye, I found it hard to use, blocking out the fine details of nebulae . I might try it again this year, hurrah !

Nick.

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I live in a suburban area which is not completely ruined by light pollution so I can make out a few constellations, along with a couple of planets. I will continue to search for visible DSO's (if there are any), and if I have any success I might think about getting an OIII filter.

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I recently bought a Skywatcher Explorer 200p and live in London, so light pollution is a big problem, and have began looking into filters and am finding everything rather confusing as I am new to this. I have had my eyes on a Baader OIII filter, as it looks quite suitable and cheap (money is an issue, and I don't really want to be spending more than £75), but I am thinking that further down the line I would like to begin with imaging. Narrowband filters also caught my eye, but all of the different symbols and stuff confused me, and they are ALOT more expensive, so I guess the two questions I am asking are: 

Is the filter I have suggested good enough?

and

Should I invest in a narrowband filter, as they look better for imaging (although like I said before, price is a major factor in all of this, so nothing too expensive)

Thanks, and this is my first post, so I am sorry if I am repeating what others have said in separate discussions.

Another consideration would be an Orion Ultrablock filter. This would have been out of reach of your budget, however there is a 2" version of this filter for sale on Astro Buy and Sell, at the top of your budget allowance. I have used one with my 8" SCT at home in light poluted skies and at dark sites. It will be more forgiving than an OIII, which to be frank I only use at dark sites.

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The Orion Ultrablock is pretty much a UHC isn't it?

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Yes it is a narrowband nebula filter and so works similar to a UHC.

Google the following Cloudy Nights thread and follow the links;

Telescope Reviews: Orion Ultrablock Narrowband versus Orion Oxygen III

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