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UltravioletPhotography

Wanted - Andrea U 52mm filter Please ?


colinbm

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Thanks Bjorn

Yes Please, I would like to see how this Andrea-U filter works with the Sigma, as the reflections off the AstroDon UVenus' mirrored surface are too bad.

Let me know the cost & priority airmail to Australia & I can send the money via PayPal.

You have my email address ?

Cheers

Col

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Yes, it has the rear dichroic layers to stop IR. You can see it in <UV Techniques & Tests/Inside Tips> by Bjorn on this site
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Thanks again Dave

The 2" & 1.25" Baader U both seem to have different coatings, but both reflective ?

This is why I am looking to try the Andrea U as it is an absorption filter ?

With the AstroDon UVenus, I am getting too many reflections.

Cheers

Col

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Col, are you sure it is the AstroDon filter and not the reflectivity of the inner lens on the DP ??

Did you try a lens hood to block some of the angled rays and perhaps help prevent some of that ?

 

 

The Baader-U has an absorptive substrate and dichroic interference coatings.

It was made for astronomy, so it must be reversed in the filter mount for photographic use.

That is, pink side facing the subject not the sensor.

 

I wonder if the AstroDon also needs to be reversed for photographic use.

Are the two sides of this filter differently coloured ??

 

The Precision-U and Andrea-U are both absorptive.

The Andrea-U seems to pass some visible light around 400nm, so gives a different UV look.

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Hi Andrea,

 

so far, I've been using the Baader in the "normal" orientation (pink side facing the sensor). - Could you tell from my images? - If yes, please elaborate.

 

Best,

Nico

 

P.S. I've been quite busy and therefore mostly quiet lately. I'm hoping to post on a more regular basis over the holiday season. – There are enough captures sitting on my harddrive.

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Nico, I am repeating what I have been taught about that Baader-U filter by Bjørn and Klaus. It is not clear to me that the pink side is any shinier than the green side. However, I'm thinking that it might be that the pink side has more to do with the IR interference?

 

I'll page Bjørn to answer this question. I should be knowing that answer myself !!

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Anyone can set up a small experiment to test the hypothesis there is a difference. Or be satisfied with Baader's recommendation.
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Thanks Andrea

I would like to try a Andrea-U filter to eliminate the reflections of & within the AstroDon UVenus filter as the cause of the reflections in the images ?

I haven't got any other absorptive UV pass filters as most pass some IR that is a problem. Though I do have a number of various 'hot mirrors', that could be useful.

Yes I do use a lens hood, & I try to position the camera in the shade.

I have tried the AstroDon UVenus both ways facing out, with no difference in the image that I can see.

The AstroDon UVenus is basically clear to look at to the eye & has a silver mirror finish on one surface. The edge of the filter is finished in black so I can't tell what the glass edge appearance is ?

"The Precision-U and Andrea-U are both absorptive.

The Andrea-U seems to pass some visible light around 400nm, so gives a different UV look."

Yes, the Andrea-U is what I would like to see & I feel it is the wavelength range that maybe best suited to the Foveon sensor.

Cheers

Col

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I would mount the silver side of the AstroDon facing the subject to avoid possible flare.

 

I fear your problem is simply with the interior of the DP lens.

However only an experiment with another filter will tell that tale. :)

 

As the Andrea-U passes some tiny amount of violet/blue, it may very well be interesting over the Foveon sensor.

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Answer: The Pink Side of the Baader-U should face the subject to prevent possible flare. The Pink Side has more IR coatings.

 

If I recall correctly, my ancient experiments with the Baader-U facing both Pink Side out & Green Side out did not seem to affect the recording of the UV-signature, per se.

 

However, flare is a nasty thing in UV photography, way too easy to produce. And sometimes you do not realize you have contaminated your UV photo until you get home and begin editing the photos. So if Baader Planetarium suggests that the Pink Side should face the subject, well, then I believe them !!

 

Because of the way telescopes are constructed, the Pink Side is facing the subject when the Baader-U, as manufactured, is used for astronomy.

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As the "Famous Eccles" used to say in the Goon Show (anyone not listening to BBC radio in the 1950s will not have a clue what I'm rambling on about) "HO HO HO, You learn something new every day". I hadn't seen the bit about having to reverse the Baader-U so I guess all my photos are backwards :) , a bit like printing negatives from the wrong side.

 

If someone as mechanically inept as me can unscrew the retaining ring on the Baader-U, invert the filter and then screw it up again, anybody can. It still rattles so I suppose it's loose enough. As Eccles said when asked for his name "Aha, the hard ones first eh?"

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Thanks again Andrea

Yes I have looked inside my cameras, too many times for my last favourite :)

I was thinking of the B+W 403 or Hoya U360 etc & matching to one of the hot mirrors I have, then I was reminded about the Andrea-U & that seemed a logical step to try.

I asked here as most of you are now using the Baader U, & I am hoping someone will have an Andrea-U spare to their needs now, that I could purchase.

I am hoping that Bjorn can make a positive find.

 

Cheers

Col

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Thanks very much Bjorn for the opportunity to try the Andrea-U filter on my Sigma cameras.

Yes the results will be posted here first, in a couple of weeks.

Cheers

Col

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My Baaders do not show a green side, only pink and golden. As I assume the golden side intended to reflect IR, I have put that to the object. When I recall that correctly, a few -not so precise- tests opposite mounted a couple of years ago did not show visual differences.

 

 

Werner

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The Baader filter are asymmetric regarding their coatings. What colour they displayed have changed over the years, but one side golden is common to several incarnations.
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