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DSO Filters ?


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Just checking, you'd be disappointed if you used them on galaxies :)

I don't see a huge difference between the two in practice, [O III] is a bit more contrasty as it cuts more background but UHC is more general purpose as it picks up H-beta too. So I'd probably lean towards UHC

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I use my [O III] in the TV76 sometimes so i'm not convinced - the filter just reduces the background, e.g. stars dim by a magnitude or so, but the [O III] (and H-beta, in the case of the UHC) are the same as you'd see normally, just with greater contrast.

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Some O-III filters are "harsher" than others (eg: the Baader O-III) so tend to produce less satifying views in smaller aperture scopes in my opinion. I use an Astronomik O-III which has a slightly wider band pass width than some O-III's and provides great views in all my scopes from 4" to 10" aperture. I like to see some background stars when viewing nebulae :)

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My most favorable experience was with a OIII filter in my 250px. Under dark skies I was looking for the Rosette nebula. Having given up looking for it with out a filter I banged in the UHC. I did find the Rosetta with the UHC but it lacked definition. As I'd found the nebula I figured I may as well try the OIII and bump it was there. I have read one filter will work on one nebula and fail on another. The UHC did make the Rosetta apparent but did not offer the views of the OIII. I know they are expensive but IMHO they are worth it. The down side I found is that they only really perform at there best under dark skies, which for most people the idea of buying a filter was to help with objects under LP skies.

SPACEBOY

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Thats what I'm trying to find out,

Which one works best under "medium" LP skies.

Mark :)

Before the Astronomik O-III I had an Orion Ultrablock in the 2" size. The Ultrablock is a type of UHC filter. That worked very well I thought and showed the Veil Nebula quite nicely in my 4" scope from my moderately light polluted back garden.

With some objects these filters can mean the difference between seeing nothing and seeing something when you have some light pollution to contend with. The Veil Nebula is an example of this as is M97, the Owl Nebula.

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I understand what you are looking for Mark but unfortunately filters are like scopes, one alone will not do the job of all. The LPR/UHC/OIII filters will work under LP skies with varying degrees of improvement. But one may work on one nebula where as another won't. My best advice would be to have a browse thought this link Filter Performance Comparisons - Article decide which Nabula your interests lye most with and then cross reference the review to which filter would offer you the most bang for the buck. As I know it the LPR filter is the best for LP areas simply because the light wave lengths were intended to cut out the same as that of a common st light. Unfortunately again the then common st light refered to is no longer that common and the LPR filters performance relies a lot on the type of st light around your district. I understand I'm not really being of much help to answer your question but it really depends on what you want to look at and the TYPE of light pollution you have. I went with all 3 filters in the end because each do a job and DSO's are my main interest which nebulas make up a fair few of them. It need not be expensive if you keep an eye out for deals or second hand listings. Castell are a budget but good performing filter.

SPACEBOY

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