Lumicon OIII Oddity

[Paul73]

Hi Guys

A nice used 2" OIII arrived today from the States to join my ABS aquired 1 1/4" version. I have had the 1 1/4" for a while and always been pretty happy with the results. However, I always thought that it dimmed the background stars a bit too much.

I immediately noticed that the two filters had, to my eye, startlingly different coatings. Here are a couple of pictures to show what I mean. Any idea why they might be so radically different?




The 2" Bright image



The much dimmer 1 1/4" image



Any thoughts on why there is such a big big difference?

Paul

[jetstream]

Hi Paul, my new Lumi OIII looks like your 1.25", I think they changed the filters a while back, with the new ones different. The older one swere laminated I think the new ones dielectric coated something like that anyway.

[NGC 1502]

Hi Paul. Cannot be certain, but maybe they simply updated the coating ? Lumicon were taken over some years ago ( I think by Parkes ) perhaps they updated the coating then ? They kept the Lumicon name on their filters following the takeover.

My old Lumicon OIII, made prior to the takeover, can be recognised because the "Lumicon OIII" designation is engraved on the edge of the filter rim, but my much later Lumicon UHC has "Lumicon UHC" printed on the rim, not engraved.

Televue have been known to update coatings on their eyepieces during the long production runs of different models, so quite normal for that to happen.

But I wouldn't worry, any Lumicon is top notch.

Hope you get first light with the new OIII soon, try the Veil in Cygnus, just ideal for that filter.

Regards, Ed.

[Paul73]

Thanks Guys

Yes, this filter was bought pretty much exclusively for the Viel. The forecast is good for tonight.......

I was aware that the coatings have changed. But was very surprised at the degree to which they have changed. The 2" doesn't have the USA on the side and has a gold Lumicon sticker on the box which does not mention the Lumicon Website.

Paul

[alan potts]

Paul,

You mentioned the dimming of background stars, this was the one reason I went for the Astonomik's on the back of John's observations. Maybe the one I have is more suited to smaller scopes. However I do have a fairly large scope now. I would like to get a Lumicon and see for myself, as Ed stated they are still going to be the highest quality, so I wouldn't worry. If you notice the pass percentages are a little different too.

Alan.

[Paul73]

Yes. I would have thought that the pass % would have gone up as the eyepieces got newer. However, I believe that the current versions are right up there.

I guess that the brightness and additional colour comes from a wider band pass in the older 2" version.

Paul

[John]

You only want a high % pass for the narrow lines that the filter permits. Everything else should ideally be 0% with sharp drop off's at the edges of the permitted lines. The Astronomik O-III has that profile but the band pass permitted is a little wider than the Lumicon 0-III and slightly offset towards the longer wavelengths as the comparison chart below shows. The Astronomik O-III has a profile very similar to the Tele Vue Bandmate O-III:

[Paul73]

Thanks John

Good graphic.

I was suggesting that the brighter image from the older Lumicon might be due to the filter allowing a wider range of bandwidths through than the newer version. Ie. Closer in character to the Astronomik. Of course, it very much depends on the extent of the spread!

Btw. The poppies in the pictures are actually bright yellow!

Paul

[faulksy]

i would say the 2" you have is no good, best thing to do is sell it to me good luck for tonight with the veil you will love it

[Paul73]

i would say the 2" you have is no good, best thing to do is sell it to me good luck for tonight with the veil you will love it

I'll get back to you in the morning!

Paul

[Paul73]

I'll get back to you in the morning!

Paul

Sorry. Keeping it!

I had a fine evening on the Viel, Eagle and Swan/Omega nebula(s). Under the twilight conditions both filters performed well. Interestingly, and contrary to my previous observations, the drop off in background stars didn't seem too severe. Since last seriously using OIII filters, I have changed my eyepieces from MaxVision 68° to Delos with the 1 1/4" and ES 82° with the 2". This may account for the difference??

I'm afraid that I didn't get around to testing using the same eyepiece. But, both gave similar levels of brightness and contrast. The 2" showed some red inthe brigher Stars and the 1 1/4" casts a slight green hue to the brighter stars.

The wide view of the Viel was something special. Can't wait to try these in the dark!

Paul

[RikM]

I may be way off here, but if you are seeing red through it, it sounds more like a UHC than an OIII to me.

[alan potts]

All i managed last night was a very black nebula which was the whole west of the sky at 8.00PM it looked like night. This nebula then threw lots of rain and bolts of lightning at the area all around us and managed to turn all our lights off. The Olll filter had no effect what so ever.

This is not Bulgarian I normally have wall to wall clear skies from May until October, I am really getting to understand how you feel in the UK. The trouble is I am finding this bad weather acually makes you think of buying more gear.

Sorry for going a bit off track

Alan.

[Paul73]

I may be way off here, but if you are seeing red through it, it sounds more like a UHC than an OIII to me.

Interesting. It definitely reads OIII on the side and appears to come in the original box.....

However, I have just tried the 2" against a UHC. The view is surprisingly similar but with there is definite spectrum broadening in the UHC. It could be that the older Lumicon is just not as tight as the newer version which picks up a few of the outliers (reduced in brightness) in which the UHC majors. Bare in mind that the UHC bandwidth includes the OIII part of the spectrum as well (some UHCs such as the Baarder pick have a big spike in the Ha region as well).

Either way it gives nice easy views in wide field. I wouldn't recommend an old Lumicon if you want a really tight OIII only filter.

Paul

[YKSE]

Either way it gives nice easy views in wide field. I wouldn't recommend an old Lumicon if you want a really tight OIII only filter.

Paul

Are you sure? If you look at the passband graph above, you can see that Lumicon OIII does let through some red light.

[Paul73]

Are you sure? If you look at the passband graph above, you can see that Lumicon OIII does let through some red light.

Good point. I'm not entirely sure that I have got the age of the filters the right way round. The 1.25" seems to let through a good dollop of everything except Yellow/Orange as the yellow poppies show as red and the leaf is green. The 2" only lets through Light Blues and Some Reds (see sharp spikes on John's graphs.

Can anyone snap a photo through a known new Lumicon for comparison?

Paul

[faulksy]

Good point. I'm not entirely sure that I have got the age of the filters the right way round. The 1.25" seems to let through a good dollop of everything except Yellow/Orange as the yellow poppies show as red and the leaf is green. The 2" only lets through Light Blues and Some Reds (see sharp spikes on John's graphs.

Can anyone snap a photo through a known new Lumicon for comparison?

Paul

ask john,swampthing,estwing and migmak they all have them

[estwing]

Good point. I'm not entirely sure that I have got the age of the filters the right way round. The 1.25" seems to let through a good dollop of everything except Yellow/Orange as the yellow poppies show as red and the leaf is green. The 2" only lets through Light Blues and Some Reds (see sharp spikes on John's graphs.

Can anyone snap a photo through a known new Lumicon for comparison?

Paul

sorry don't do AP!

[jetstream]

Here is my new OIII, it's picking up clouds and blue sky.... it is basically reflective

[John]

Mine looks just like yours Gerry

Similar pass figures too, though different production runs will vary slightly.

[alan potts]

One thing that just puts that little extra on the Lumicon package for me is the handwritten pass figures and batch number information. As good as Astronomik's are meant to be they have nothing like that. It may well not mean much to some but to me it just adds that bit of care and attention to detail.

Alan

[YKSE]

As good as Astronomik's are meant to be they have nothing like that. It may well not mean much to some but to me it just adds that bit of care and attention to detail.

Alan

It may worth an effort to send them an email. I found out mine was made 2007, no test protocol since they didn't test all the filters at that time. Their tested samples had transmissions between 90-95% at 495.9nm, and 93-96% at 500.7nm, kind of like the transmission curve given in John's graph.

[Dom1961]

Sorry for hijacking the thread, but which in your opinion performs better? Lumicon or the Astronomik as I see the Lumicon is only a few £ more

[John]

Sorry for hijacking the thread, but which in your opinion performs better? Lumicon or the Astronomik as I see the Lumicon is only a few £ more

Very, very little in it. Both are top drawer in terms of quality. The Astronomik has a wide band pass so you see more background stars. The Lumicon might provide slightly better nebulosity enhancement in larger scopes (12 inches or more) but it's a very close run thing.

I had an Astronomik O-III for a few years and loved it. Equally I've been very impressed by the Lumicon O-III I now have.

[Dom1961]

So for my 8" the astronomik will be better suited?