What's a good Moon (neutral density) filter?

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notFritzArgelander
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Re: What's a good Moon (neutral density) filter?

#21

Post by notFritzArgelander »


Lady Fraktor wrote: Sun Mar 29, 2020 8:18 pm
stewe wrote: Sun Mar 29, 2020 8:14 pm
notFritzArgelander wrote: Sun Mar 29, 2020 5:08 pm

I've never looked for the 1.25" diameter. All I have are the 2" and that's all I use.
I see. I have to admit, I also had trouble finding any B+W filters in the 2" size online, all I saw at European vendors' sites were various filters for camera lens sizes.
They do not make astro sizes, you can buy standard 48mm or 46mm filters with a 48-46mm step down ring.
They do, or did, but rarely. I ordered mine through: http://www.company7.com/home.html The process you suggest is likely quicker.
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Re: What's a good Moon (neutral density) filter?

#22

Post by Arsene37 »


Hello !
Lady Fraktor wrote: Sun Mar 29, 2020 8:35 pm … I cannot comment on the Baader but it is likely sealed for a reason.
Found this on their site :

"Both filters form a unit, to keep the filters perfectly aligned to each other – this double filter cannot be seperated into to single filters. This way, the filter delivers high-contrast views even at high magnifications. Polarizing filters offer the highest flexibility; if you are looking for superior image quality, you should use regular Neutral Density Filter, where there are less glass surfaces in the light path."

You can buy two single polarizer to separate them.
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Re: What's a good Moon (neutral density) filter?

#23

Post by stewe »


stewe wrote: Sun Mar 29, 2020 8:19 pm
Lady Fraktor wrote: Sun Mar 29, 2020 8:11 pm try one part on the nosepiece and one part on the eyepiece.
When you want to vary the density, turn the eyepiece.
That should get rid of your reflection issue. This can also occur when stacking different filters so the seperation is rather common thing to do.
I will give it a shot if I have a chance and let you know what I found.
I tried this and the results were quite interesting.
I use a 2" APM mirror diagonal with dielectric coating. When one part of the variable polfilter is installed on the eyepiece, the other half on the telescope side of the diagonal (i.e., the mirror is between the two filters), then the following can be observed:
- the reflections due to the imperfect alignment of the filters wrt the optical axis remain,
- the polarization becomes frequency-dependent, resulting in a change in color (and not the change in intensity) as one rotates the eyepiece.

The latter is probably due to the dielectric coating on the mirror. I found a thread at CN that discusses this effect in some detail, basically concluding that the effect is smaller for older mirrors with thinner coatings and there is no observable such effect for cheap uncoated mirrors:
https://www.cloudynights.com/topic/5964 ... n-viewing/

So my verdict about the TS variable polfilter:
- when mounted to the diagonal nosepiece: reflections and massive loss of contrast,
- when mounted separately with the diagonal mirror in between the pieces: refections and loss of contrast remain, tunability of flux does not work with a dielectric mirror,
- when mounted on the eyepiece: would hit the diagonal mirror, i.e., does not work.

In summary: useless, worthless product.

I just ordered a Baader ND0.9 filter, let's see what that one delivers in terms of optical quality.
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Lady Fraktor Slovakia
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Re: What's a good Moon (neutral density) filter?

#24

Post by Lady Fraktor »


Unfortunate that this occurred, have you been in touch with TS for a return?
I suspect the filter was from a bad batch as they normally do work better than this.
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Re: What's a good Moon (neutral density) filter?

#25

Post by NGC 1365 »


I use the Baader orange 570nm longpass filter , best optical quality filter I have used for lunar observing. I've tried polarised and so called moon filters, but don't like the image through them.
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Re: What's a good Moon (neutral density) filter?

#26

Post by West83 »


NGC 1365 wrote: Wed Apr 01, 2020 9:20 pm I use the Baader orange 570nm longpass filter , best optical quality filter I have used for lunar observing. I've tried polarised and so called moon filters, but don't like the image through them.
I am looking at so called Lunar filters, and was thinking of getting the Neutral Densitiy (12,5%) from Baader, but I think that the orange 570nm might be a more versatile choice. It does say on their website that this filter "enhances lunar and planetary observations at dusk". I am curious about your experience, did you observe the full moon with this filter, and any other advantages you feel it has?

EDIT: Did you use it during the night as well?

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Re: What's a good Moon (neutral density) filter?

#27

Post by NGC 1365 »


I use the filter for full or near full observing and also for dusk/ dawn lunar viewing where it helps in enhancing detail. I use it for most of my lunar viewing except at high power(over roughly 350x magnification. I do view without a filter as well, but personally like the filtered view. The orange cast might not be to everyone's taste.
Ivan
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