Author Topic: What good are filters for?  (Read 669 times)

calfkommomu

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What good are filters for?
« on: December 27, 2017, 08:46:07 PM »
I saw some eyepiece filters at my clubs' swap and shop. I know that a solar filter
is put over the front of the scope to see the sun, but what are the many colored eyepiece filters for,
and are they worth the price?



chuckgemslerswe

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Re: What good are filters for?
« Reply #1 on: December 29, 2017, 01:29:17 AM »
filters can be used to enhance a view (Moon, Mars, Saturn, etc) or filter out undesired components (light pollution for instance, emissions that interfer with seeing some special thing in a nebula, etc) . Whether they're worth their price (for you) depends on you and your goals, requirements, and hurdles . Wish I could say more but there are those who can put it far better and ask all the "right questions to clarify the situation in more detail...

junktranasop

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Re: What good are filters for?
« Reply #2 on: December 29, 2017, 05:41:58 PM »
The effects of color filters (red thru blue) are very subtle and so will make only small changes in the image. Small but significant when one looks very close.

Alex Strouth

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Re: What good are filters for?
« Reply #3 on: January 03, 2018, 03:15:59 PM »
Filters are also used on cameras for similar reasons they are used for the eye. Some are better suited for photography than visual.

The prices tend to reflect quality and how difficult they are to make for the intended purpose. The nebula filters tend to be more expensive and higher quality for instance.

Are they worth the price? They can be, but it may take some time to learn the nuances. Personally I enjoy using them and think most quality filters are worth their cost, especially at used prices.

If you want to know more about the roles of filters, viewing conditions and vision then this article might be a good place to start. It is more technical than other articles, but it goes beyond just listing what object to view with a given filter.
http://www.alpo-astr...es/FILTERS1.HTM

jingdilenma

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Re: What good are filters for?
« Reply #4 on: January 04, 2018, 01:49:26 PM »
I think those sets of four color filters are pretty worthless. I will not deny that some observers get some value added through them. But, in essence, if you like a pea green Jupiter or Saturn and can see something extra with it....well go right ahead.

I prefer the colors that actually come through in the white light view, as the planets provide plenty of those. I've never heard anyone say that the color filters are useful on the moon. Maybe they are.

I keep thinking I should sell my color filter set but the money it would fetch is small and as a result it just rides around in my kit. Going on 15 years now. Used them once.

The filters that actually do something and make you want to come back to them are:

1. OIII - nebula filter
2. UHC - nebula filter
3. Neodymium - very good on Jupiter and Mars
4. Polarizing filter - helps tone down the Moon, and has *super* effects used in conjunction with h-alpha set ups for the sun.
5. I will mention h-alpha setups, technically they are filters, but they are much more complicated, and cost a great deal more. Daystar quark is one of several options out there. This is solar viewing kit.
6. H-beta filter - used primarily for Horsehead and California Nebula
7. Spectroscopic filter - can be used to detect small planetary nebulae (in theory) and also will give a nice spectral display on bright stars.

I would say that the R G B Y filters that cost $50 are strictly noob, but I can't really say that, because I know accomplished hard core observers who use them. But such individuals are few and far between. The number of experienced observers using all or a combination of filters 1-7 above is, I venture to say, one or two orders of magnitude greater than the number of experienced observers who still reach for the RGBY.

Now, this has nothing to do with photography, where color filters are a vastly different matter (and MUCH more expensive).

Greg N

Marvin Neboet

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Re: What good are filters for?
« Reply #5 on: January 04, 2018, 04:41:28 PM »
Quote
The effects of color filters (red thru blue) are very subtle and so will make only small changes in the image. Small but significant when one looks very close.


Edit : Need to add that color filters are for use on Planet & maybe the Moon.

acbanlota

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Re: What good are filters for?
« Reply #6 on: January 04, 2018, 05:50:36 PM »
A yellow #8 filter is useful to cut down on CA with a refractor on bright objects. They have special fringe killer filters but they are a lot more
money than a #8.

I think I can see a wee bit more detail on mars when using an 82A light blue filter.
I just bought a neodymium filter for a great price. I will see what that does.
A moon filter is a must have to comfortably view the moon.

I don't like using the darker colored filters. They make the colors on planets too fake, and block a lot of light.

tanktositsoft

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Re: What good are filters for?
« Reply #7 on: January 08, 2018, 12:27:51 AM »
Many of the simple coloured ones are I think of little use. Some people like them for whatever reason but I suspect that it is more they like a coloured image more then the filters do anything significant.

The main thing to remember is that a filter only removes light, it is where it removes it that needs a bit of though.

Filters like Ha, OIII and similar allow through only the specified wavelength. In the case of Ha then the small amount of light that is Ha from the object gets through the rest is blocked. It means that the contrast is hightened - this being done by the removal of the non-Ha surrounding the object. As said previously this means that about 90% of the light is blocked/removed, not that the Ha is hightened.

Equally dropping an OIII filter in to look at the Rosette Nebula is not going to do much. As all the nice Ha from the Rosette is blocked by the OIII filter.

It is "amusing" the times that I read that someone has dropped in an OIII filter and an Ha filter expecting to see both Ha and OIII, What they actually get is nothing. The Ha filter blocks the OIII and the OIII filter blocks the Ha.

Chris Harwood

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Re: What good are filters for?
« Reply #8 on: January 08, 2018, 04:20:16 PM »
Quote
The only filter I have direct experience with is a neutral density 13% moon filter. It really helps if you experience uncomfortable brightness while viewing the moon. I've seen them for $12.50 new. There are also 25% and 50% filters. The lower the percentage, the dimmer the moon will be. Another trick for dimming the moon is to just use higher magnification. If you're looking for details on the lunar surface, you may be doing that already. If you want to use lower magnification for an overview of the moon, the moon filter may be of use. I've read of people using polarizing filters for lunar observation. They are adjustable but more expensive.
Quote

A yellow #8 filter is useful to cut down on CA with a refractor on bright objects. They have special fringe killer filters but they are a lot more
money than a #8.

I think I can see a wee bit more detail on mars when using an 82A light blue filter.
I just bought a neodymium filter for a great price. I will see what that does.
A moon filter is a must have to comfortably view the moon.

I don't like using the darker colored filters. They make the colors on planets too fake, and block a lot of light.


I don't own a refractor myself, but I see you have a short focal length refractor in your signature. I think it is an achromat, and thus may give you purple fringes around bright objects. This is the CA (chromatic aberration) vtornado is speaking of.

Many of the other filters mentioned here are pricy enough that I wouldn't buy one myself without trying a friend's first.

Also, note there are both hydrogen-alpha (H-alpha) and hydrogen-beta (H-beta) filters. I know little about them, but during my reading, I didn't pay attention to the difference at first.

Antonio Zuniga

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Re: What good are filters for?
« Reply #9 on: January 09, 2018, 08:58:53 AM »
Quote
I saw some eyepiece filters at my clubs' swap and shop. I know that a solar filter
is put over the front of the scope to see the sun, but what are the many colored eyepiece filters for,
and are they worth the price?


You may want to ask the same question in the Solar System Observing forum.

Ed D

reapriavoland

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Re: What good are filters for?
« Reply #10 on: January 10, 2018, 12:27:24 AM »
Colored, planetary filters are good for hard-core planetary observers as they each enhance features that would otherwise be difficult or even impossible to see. However, for solar system sightseeing, a variable polarizer or some neutral density; i.e. sunglasses, filters to knock down the glare so you can see detail are best. The colored filters have a detrimental effect on the aesthetics of the view.

frosperloacatch

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Re: What good are filters for?
« Reply #11 on: January 10, 2018, 07:37:25 AM »
Quote
Actually, narrowband and OIII filters are the two most commonly used, with narrowband filters being effective on a greater number of objects. H-beta filters will enhance a rather limited number of nebulae, most notably B33 (the Horsehead Nebula) and NGC 1499 (the California Nebula).

http://www.cloudynig...sky-objects-r60

By the way, UHC (Ultra High Contrast) is actually a propriety designation for a particular brand of narrowband filter.

<p class="citation">QuoteEqually dropping an OIII filter in to look at the Rosette Nebula is not going to do much.

That statement does not coincide with reality. A narrowband or OIII filter will certainly enhance the Rosette Nebula. I've used both types many times to observe NGC 2237-9 with a variety of telescopes.

NGC 2237-9 “ROSETTE NEBULA” (diffuse nebula in Monoceros).
(100mm f/6, 22x)
DEEP-SKY: (2) Some increase in contrast, but nebula is still more of a diffuse haze around the central star cluster with hints of irregularity.
UHC: (5) Noticeable increase in contrast, with more outer nebulosity visible and some irregular light and dark structure being visible. Nebula was visible when UHC was held up to unaided eye!
OIII: (5) Higher contrast than with UHC, with more dark irregular detail throughout the region (especially in the 10 inch), but not quite as much nebulosity visible as in UHC.
H-BETA: (1) Very faint glow around the star cluster, not much better than without a filter (but much dimmer).
RECOMMENDATION FOR ROSETTE NEBULA: UHC/OIII.


http://www.prairieas...common-nebulae/

Traditional color filters can be useful for certain applications. In general, they are more effective when employed with large apertures. I use them primarily for observing Mars, in particular the Wratten #21 (orange) and #80A (blue) and CC30M (magenta) filters.

http://agenaastro.co...ary-filter.html

Neutral density filters and polarizing filters also have their proponents.

Dave Mitsky