Astronomik UHC-E (1.25") filter

[bobson (Bob)]

Hi

I am new here, sorry if this was already posted, I searched and couldn't find about it.

I read some guys talking about Astronomik UHC-E (1.25") filter. What are they used for? Will I notice difference in viewing, or will I see more, maybe colour? They cost $119 from Bintel, they are not cheap.

Thanks in advance

bob

[Jeff]

Hi Bob,

The intent of the UHC-E filter is to improve viewing of certain deep sky objects (eg. nebulae and supernova remnants), especially from light polluted suburban skies. The important wavelengths for these targets tend to be the Hydrogen Alpha, Hydrogen Beta, and Oxygen-III spectral lines.

By filtering out wavelengths from common light pollution sources (eg. sodium vapour and mercury vapour street lamps), the background sky is appears darker which which improves contrast for viewing details of the nebula or supernova remnant.

Attached is a link to info page at Astronomic:
http://www.astronomik.com/english/eng_uhc-e.html

Cheers,
Jeff

[JethroB76 (Jeff)]

If you're interested in UHC style filters for nebulae, I'd recommend doing a search on the forum for the DGM NPB filter.
You won't get one locally, but direct from the manufacturer in the US, you can get a 1.25" for <$100AU delivered.

Great performers and well regarded, check em out.

[bobson (Bob)]

Thanks guys, I'll check those links.

Jeff,

When you say to improve viewing especially from light polluted suburban skies. Does it mean if I go out, away from light poluted skies, I don't need those filters as much, or not at all?

thanks

bob

[wavelandscott (Scott)]

Like most things in life there are different types and levels of quality in filters...UHC/OII/coloured/polarizing etc.

A good filter will block out a particular wavelength(s) of light and only let pass through the observationally desired portion. Different filters let through (filter) different wavelengths of light. This makes it easier to see some objects as only the specific spectrum(s) of light that is of interest are passed through the filter. Think sunglasses.

For example, filters can be employed to block out the specific wavelengths of light given off by sodium/mecury streetlights...hence improving the view. Another example would be the use of a colored filter to pull more detail out of planet observations.

Having said that, no filter can ever replace a dark sky for DSO work! The light given off by the streetlight will make getting your eyes dark adapted impossible and so while they can aide the blocking of the non-Astronomical they will not turn a backyard into the Outback.

I actually find that DSO filters work best in a dark sky situation...while this may sound counter intuitive, a good filter will discriminate against the light you don't want and thereby make some objects "pop" right out.

Maybe I am just getting lazy or have becoem a bit of an observing snob but I tend to choose to view bright objects not as impacted by the light pollution from my backyard saving my DSO cravings for when I am under a darker sky...and with a DSO filter amazing.

There are many good articles on Cloudy Nights website...many written by an amatuer observer from Nebraska (David K)...well worth a read if you are interested in filters. Clear Dark Skies!

[Jeff]

Hi Bob,

When directly viewing nebulae & supernova remnants from truely dark skies, I don't use DSO filters at all .... since the dark sky already gives excellent contrast. Having said that, a DSO filter will still offer a slightly alternate view (eg. accentuating dust lanes in a nebula).

Note that you will not see any colour, since the faintness of the objects will only activate the cones in your eyes (monochrome), but not the rods. To see all of the beautiful colours in DSO, astrophotography is the way to go ... lots of example photos in these forums.

Hope this helps.

Cheers,
Jeff

[Stephen65]

I believe the UHC-E is optimised for smaller telescopes than the UHC. While the UHC gives improved contrast on nebulae etc its at the cost of some loss of light, the UHC-E has broader pass bands so it doesnt deliver quite the same contrast improvement but it also doesn't dim the objects as much.