Quote:

---

And if anyone has filter comparison between Lumicon's, Baader's and whatnot's filters, share it with the group. That'd be good, since those Ls are pretty hard to come by these days...

Jake

---

Well, the Lumicon filters are still available (Lumicon was bought-out by Parks). The Orion (U.S.) equivalent of the UHC is the Ultrablock, and its performance is very similar to the Lumicon model (more "Gaussian" passband, but no red passband for H-alpha). The Astronomik UHC is also pretty much the same as the Lumicon model in performance. For OIII filters, the Astronomik and Lumicon models are very similar, but the Astronomik is a bit broader, so it might not yield quite as dark a sky background as the Lumicon OIII filter. It still should work fine however. The Tele Vue OIII is *way* too broad to be considered a "true" OIII filter (more like the UHC), so if you are looking for an OIII, Tele Vue might not be a good choice. Thousand Oaks also makes its line of filters, and they are fairly similar to the Lumicon models. Clear skies to you.

--------------------
David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

Post Extras:

Quote:

---

And if anyone has filter comparison between Lumicon's, Baader's and whatnot's filters, share it with the group. That'd be good, since those Ls are pretty hard to come by these days...

Jake

---

Post Extras:

Quote:

---

Here an other::

http://home.freeuk.com/m.gavin/grism2.htm

Greetings!

Amalia

---

I have seen this link in several posts since, but no one thanked me...

So:
Thank you, Amalia!

Amalia

--------------------

Post Extras:

Quote:

---

How many times have I asked that? The answer for many common nebula can be found in this CN article by our esteemed colleague, David Knisely. This is an important read for anyone thinking of buying a new filter. IMO it should be stuck to the top of this forum.

Way to go, David!

---

Post Extras:

Quote:

---

For everyone thinking about a nebula filter see the article in Astronomy, August 2005, page 82. Very similar review to the one on CN, but less nebulas and more filters. Nice comparison between different brands.

---

This article is misleading at best. It would be better to take it with an extremely large grain of salt. For what works on a specific object, I might recommend reading my article, but for specific recommendations, the broadband "LPR" filters like the Lumicon Deep-sky are best for reflection nebulae, and the Narrow-band filters like the UHC are probably the best overall for emission nebulae. For some objects like the Veil or for many planetary nebulae, the OIII filters are best, and for a more limited number of faint emission nebulae, the H-Beta filter may be of at least some use. Clear skies to you.

--------------------
David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

Post Extras:

Quote:

---

The German astronomer André Knöfel measured the transmission of about 50 filters...

http://www.astroamateur.de/filter/


Amalia

---

Well, I can't read German but I can tell that the transmission curves aren't very accurate (or if they are, then at least some of those filters need to be discarded). The Lumicon OIII and UHC do not have some of the huge bumpy secondary passbands in the deep violet that are shown with transmissions well over 40%. The various versions of the transmission curves are puzzling at best. I find that, while there are some variations between filters, the curves found in the RASC Observer's Handbook in the section on filters tends to be fairly accurate, at least for the Lumicon line. Clear skies to you.

--------------------
David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

Post Extras:

Quote:

---

David,

all I can answer you is the following:

# 1 The 4 various versions of the transmission curves regarding the
Lumicon UHC and Olll are different because of the year of fabrication
and because André had several filters at his disposition.

---

Quote:

---

# 2 I think it is very interesting to be able to see how the curves vary.
I prefer this to a single "This-is-the-truth!" curve.
This is a scientifical approach to me.

# 3 I wonder how you know the curves of the RASC Handbook are
more precise than these by André?

# 4 Right now I holded my two Lumicon Olll filters against a halogen
light. My fingers got coloured (in two different) violets by the passing
light. What is the meaning of this?


Amalia

---

Well, it probably means that the OIII you have does have more than one passband (or that you are not quite holding the filter perfectly straight on which can shift the location of the passband). Objects should look a bluish-green color when viewed through the OIII. Again, some of the OIII filters on the market do have a red secondary passband around H-alpha, but some do not. The only way to know what you have for certain is to use a small spectroscope for a quick visual inspection. Clear skies to you.

--------------------
David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

Post Extras:

Quote:

---

David,

my two Lumicon Olll filters are both bought from the same high-price Swiss
vendor, and they came both in boxes on which the transmission in
Olll 496nm and Olll 501nm are written by hand. This leads me
to the conclusion that they are both premium versions (considering
also today's prices of SFr. 150.- resp. SFr. 350.- {= 120$ / 280$ vs.
Adorama US prices: 100$ / 200$}).

Swiss are asking for high quality.

---

Yes, all the Lumicon filters I have gotten also have the transmission figures hand written on the packages. My first ones date back to the mid to late 1980's (premium grade) but surprisingly, they have aged little (I do tend to take good care of them). My old OIII (1.25") has 94% transmission at the 501 nm line and 88% at the 496 nm line, with zero transmission at H-Beta (about 80% transmission at H-alpha). My new one has 0.2% transmission at H-Beta, 92.4% transmission at the 496 nm line and 91.2% at the 501 nm line, but has only 0.1% transmission at the H-alpha line. There is some variation as to the exact curves from filter to filter, but as long as you can mainly see only the primary passband at the two OIII lines and little else, the filter should work OK. From the pictures you posted, you have a bit of the opposite situation that I have, in that my 1.25" filter is the one that has the booming red secondary passband while my 2" Lumicon OIII has almost no red passband at all. If you see a very large violet passband using the spectroscope, then there may be a problem with the filter. There should only be a low amplitude "violet leak" way down towards 400 nm or so if it exists at all. If a red passband exists in addition to the primary passband, then it can be a bonus, because in larger apertures, this may allow H-alpha emission to be visible in brighter nebulae. I can see faint reds in M42 with my older OIII filter because it passes a lot of the H-alpha line, but with my new 2" Lumicon OIII, I don't see the red at all. Clear skies to you.

--------------------
David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

Post Extras:

Quote:

---

If a red passband exists in addition to the primary passband, then it can be a bonus, because in larger apertures, this may allow H-alpha emission to be visible in brighter nebulae. I can see faint reds in M42 with my older OIII filter because it passes a lot of the H-alpha line, but with my new 2" Lumicon OIII, I don't see the red at all. Clear skies to you.

---

Oh, I see - so I will compare the performance of both filters on several
objects, specially on M42.

Thank you for this interesting discussion!

Amalia

--------------------

Post Extras: