Should I buy nebula filter for my 120mm refractor?

Hi there. You posted:

I'm considering buying Lumicon UHC and/or O III filters. Is my scope's
aperture too small for this? Also, which one should I buy if I only
have enough money for one filter?

No, your scope is not too small, although the number of objects which may be
improved by the filters may be somewhat limited due to your smaller aperture.
The best power range to use with these filters is from 4x to 10x per inch of
aperture, so for a 120mm scope, you will want an eyepiece which gives you
something in the range of 19x to 47x. If you can only afford one filter, I
might suggest either the UHC or Orion Ultrablock. If you can get two, the
OIII makes a good companion filter. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 10th Annual NEBRASKA STAR PARTY *
* July 27-Aug. 1st, 2003, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
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I completely agree with David - your scope is not too small and I would go
for UHC at first.

Go with the UHC I've used both and the UHC is the most used. But after a while
you won't even use it. But they hold there resale price good.,b

I'd go with the O III filter. Hydrogen rich nebula will never look better.

Michelle Stone
Custom Telescopes by Plettstone
http://www.plettstone.com/telescopes


(Ante Perkovic) wrote in message . com...
Hi,

I have 120mm f/8.33 Konus Refractor.

I'm considering buying Lumicon UHC and/or O III filters. Is my scope's
aperture too small for this? Also, which one should I buy if I only
have enough money for one filter?

Thanks,

Ante

(Ante Perkovic) wrote in message . com...
Hi,

I have 120mm f/8.33 Konus Refractor.

I'm considering buying Lumicon UHC and/or O III filters. Is my scope's
aperture too small for this? Also, which one should I buy if I only
have enough money for one filter?

Thanks,

Ante

I found the UHC to be useful with an 80mm short tube.

Regards,
Russell

Hi there. You posted:

I'd go with the O III filter. Hydrogen rich nebula will never look better.

Well, the problem is that the brightest Hydrogen emission line (H-alpha, at
6562.8 Angstroms) is so far into the red that the human eye has difficulty
seeing that kind of emission. The OIII also eliminated the effect of the
second brightest line (H-Beta at 4861 Angstroms), so for hydrogen emission
nebulae in a small telescope, the OIII isn't exactly the filter of choice
(although it certainly can be used in smaller instruments). For planetary
nebulae which have the strong OIII emission lines, the OIII overall is the
better filter, but for smaller apertures trying for diffuse emission nebulae,
the UHC (or another narrow-band filter) can be somewhat more useful. The
broader bandwidth of the UHC will also not dim the stars quite as much as in
the OIII, so it will be a little easier to "navigate" areas, especially in
smaller apertures. In fact, there are some nebulae which are hurt by the OIII
over the UHC or H-Beta filters. On the Cloudynights web page
http://www.cloudynights.com is an article comparing the performance of various
filters on over 80 emission and planetary nebulae, and it can be a useful
guide to which filter to use.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 10th Annual NEBRASKA STAR PARTY *
* July 27-Aug. 1st, 2003, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

Hi Michelle,
I think perhaps the H-Beta might do better on hydrogen rich nebulae.
Clear skies,
Shneor Sherman


I'd go with the O III filter. Hydrogen rich nebula will never look better.

Michelle Stone
Custom Telescopes by Plettstone
http://www.plettstone.com/telescopes


(Ante Perkovic) wrote in message . com...
Hi,

I have 120mm f/8.33 Konus Refractor.

I'm considering buying Lumicon UHC and/or O III filters. Is my scope's
aperture too small for this? Also, which one should I buy if I only
have enough money for one filter?

Thanks,


Ante

Hi there. You posted:

David, do you know why the 2" Orion Ultrablock sells for only $99 in
the Fall 2003 catalog, while the Lumicon UHC sells for $199? The 1
1/4" versions are only $20 apart. I need a 2" nebula filter but have
to wonder about the quality of the Ultrablock at that price, though
I've heard that they are good filters.
Any thoughts?

Its tough to say, but I do know that Lumicon filters are of good and fairly
consistent quality. I only own the Orion Ultrablock in the 1.25" size.
Another option is Astronomik's UHC filter or the Narrowband DGM filter. Clear
skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 10th Annual NEBRASKA STAR PARTY *
* July 27-Aug. 1st, 2003, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************