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Omega Optical CaH filter

Posted: Sat May 12, 2018 8:00 am
by GreatAttractor
I was browsing through Omega Optical filters on Ebay and noticed this:

Optical Filter Astronomy 396.9SC0.2 Ca H filter 1.25"

(full description: link)

CaH with 2 Å bandwidth and 90% transmission for $300. Seems promising, what do you think?

Re: Omega Optical CaH filter

Posted: Sat May 12, 2018 8:16 am
by TheSkyBurner
It is not 90% transmission, and omega filters are not fully trustworthy. Some of them are moldy right out of the box and they are never new as advertised. Use caution.

Re: Omega Optical CaH filter

Posted: Sat May 12, 2018 8:19 am
by TheSkyBurner
A side note, the seller is good at allowing returns as i have gone through 8 hydrogen alpha filters trying to find one that actually works. But i never found one and got a refund. So if you do buy, keep in mind you can keep sending them back , which is relatively common for his filters.

Re: Omega Optical CaH filter

Posted: Sat May 12, 2018 1:50 pm
by Merlin66
I’m trialing a stacked combo of three Omega CAK filters (see my other thread)
So far the results have been promising.viewtopic.php?f=9&t=23536

Re: Omega Optical CaH filter

Posted: Sun May 13, 2018 1:13 pm
by TheSkyBurner
Merlin66 wrote:
Sat May 12, 2018 1:50 pm
I’m trialing a stacked combo of three Omega CAK filters (see my other thread)
So far the results have been promising.viewtopic.php?f=9&t=23536
MErlin can you post focused images of your omega filters, hold a magnifying glass up to them in front of the camera to get a macro focus.

Trying to look for visible defects to determin if you got new filters or old stock filters from returns or over runs.

Re: Omega Optical CaH filter

Posted: Sun May 13, 2018 2:07 pm
by Merlin66
Why?
They work for me......

Re: Omega Optical CaH filter

Posted: Sun May 13, 2018 2:55 pm
by TheSkyBurner
wow... I guess i just have to show you guys.

there is a difference between worlds here. Whatever works for you will obviously not work for me or other people. Very simple to post a picture of what you have and are working with. When I said I gone through 8 of his hydrogen alpha filters i assumed that was enough to request a photo. So here are my omega optical filters for 393nm that I was sent. I got a total refund and refused to try getting more replacements..

One has a giant epoxy seperation visible on the top layer, the second one had total seperation between two glass glass plates and produces unlimited reflections, the third one is not even mounted in a cell that supports its thickness and has mottled bubbles all inside the glue, also has unlimited reflections.

ENJOY!
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Re: Omega Optical CaH filter

Posted: Sun May 13, 2018 3:05 pm
by TheSkyBurner
Now remember, these are sold "as new manufactured parts, specifically made for ebay customers" They clearly are not manufactured for anybody.
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Re: Omega Optical CaH filter

Posted: Sun May 13, 2018 3:06 pm
by TheSkyBurner
Clear visible damage to a "new filter", which is reminiscent of PST ITF rust. Mold, mottling, degradation whatever you want to call it. This is what he mails people sometimes.

You MAY get a good one, but the story is more often bad than good for most people.
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Re: Omega Optical CaH filter

Posted: Sun May 13, 2018 3:06 pm
by TheSkyBurner
again. every filter i have gotten has some sort of damage. So when ordering from ebay bjomejag and not directly from the manufacturer its like playing the lotto.
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Re: Omega Optical CaH filter

Posted: Sun May 13, 2018 3:18 pm
by TheSkyBurner
This one i cant even begin to explain. The side of the filter is marked 540nm, but it transmits nothing but red. So much for that continuum filter i ordered..
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Re: Omega Optical CaH filter

Posted: Sun May 13, 2018 3:30 pm
by TheSkyBurner
Ill stop there, but if you want to see more of his "new filters" i will gladly post about 32 more photos because thats how many paper weights i have sitting here in a desk drawer.

However it is understandable to have faulty deliveries. There are people still getting faulty coronados , faulty quarks, and faulty lunt equipment. Stuff happens. But rarely from those major companies, and they dont sell things on ebay.

Moral of this thread, you might have to send back your filters from ebay because; ebay is a "thrift" shop made for some goods which cannot be sold elsewhere and specifically for people to sell used equipment under specific circumstances..

Re: Omega Optical CaH filter

Posted: Mon May 14, 2018 12:14 am
by Valery
My experience with Omega is rather poor. The filter he sent me is the worst optical detail I have ever saw.

Here is this filter unevenness in CWL. I stacked it with Lunt etalon.


Valery

Re: Omega Optical CaH filter

Posted: Mon May 14, 2018 6:55 am
by Montana
I have one of those, it is optically clear but I didn't see much difference with it. I don't use it anymore.

https://www.flickr.com/photos/alexandra ... 0715279858

I must admit I tried it with the SCT and the Baader solar film and I couldn't see anything at all, does Baader film cut below 400nm? it works great with the solar wedge. I can sell you mine for a cheap price if you like? but you probably don't want it :)

Alexandra

Re: Omega Optical CaH filter

Posted: Mon May 14, 2018 7:50 am
by Merlin66
Alexandra,
The ND 3,8( or the ND 5) filtering extends into the UV.....
Just not enough light getting through to the filter - as you say, works well with the wedge.

Re: Omega Optical CaH filter

Posted: Mon May 14, 2018 4:45 pm
by GreatAttractor
Thank you everyone for input. CaK imaging is a plan for the future anyway, it's Hα for me right now.

Re: Omega Optical CaH filter

Posted: Wed May 16, 2018 8:56 am
by TheSkyBurner
Montana wrote:
Mon May 14, 2018 6:55 am
I have one of those, it is optically clear but I didn't see much difference with it. I don't use it anymore.

https://www.flickr.com/photos/alexandra ... 0715279858

I must admit I tried it with the SCT and the Baader solar film and I couldn't see anything at all, does Baader film cut below 400nm? it works great with the solar wedge. I can sell you mine for a cheap price if you like? but you probably don't want it :)

Alexandra
Alexandra, it looks like your cah picture is chockfull of ellerman bombs. Perhaps it would make a great an8mation filter for offband cah? Perhaps you got a good filter after all, although its just not onband. Could be the diamond in the rough if you play around a bit more!
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