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Narrowband Imaging with--


Angeleyes
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Hello

Here is my first stupid question for the forum lol.

I have a Meade Narrowband filter,Meade say it was not intended for imaging but i ask,can it be used to produce an image with greater detail than say no filter?

Will the image contain narrowband wavelengths ie greater detail in say m42?

the Camera's i use are the dsi colour 1 and a dsi pro 1 .

I ask because i do not have the finance at the moment to buy additional filters and am trying to make do and fancy trying narrowband but will it work or am i wasting my time?

Can you help with advice on this type of imaging?

below is a chart of the band pass of my filter.

Thank you

Regarde

Tim

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I think the filter you have appears to be a type of UHC filter - basically strong sky glow filter, so it only lets through the important wavelengths. However, it also seems to let through IR (beyong Ha), which is why they say not suitable for imaging. As IR is not focused the same as visible light, it could potentially make the image a little more blurred. However, it's worth a try, particularly if you suffer from light pollution.

I did have the DSI1 imager and it had an IR filter already in front of the sensor. I recall that it was removeable. So you might be ok if you have this in place already.

Edited by sgazer
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mmmm food for thought.

Its clear here tonight so say the met office so i will give it a go.

Yes the DSI Colour has a IR cut filter of sorts,i will try it in combination with the narrowband filter.

If anyone can add to this then please do.

regards

tim

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its not narrowband imaging in the conventional sense....conventionally what we mean is we place a filter in front of the imaging sensor, that isolates just one emission line. For example, an Ha filter that lets light of 656.3nm pass through but rejects all others (virtually).

The bandpass tells you what wavelength range it will pass. A 6nm Ha filter means it passes the Ha emission line (656) and that its Full Width Half Max FWHM is 6nm. This means the width of the transmission curve corresponding to half the peak transmission as a width of 6nm....think of it as passing 656nm+-3

when we look to your transmission graph, the filter is design to pass Hb, O[iII] doublet, Ha and S[iI] (not depicted). It does not pass light at 589nm for example, where the horrible sodium doublet lies, which gives rises to our horrible orange LP skies.

so what this filter does is pass good wavelengths from the astro object, Hb, Ha, O[iII] and reject earth borne bad ones like sodium at 589

so you have a light pollution filter there, not a narrowband filter, in the conventional sense. Where the narrowband comes in is that your filter is slightly more restrictive in the wavelengths it passes than other LP filters....

for true narrowband imaging one needs the filters that pick out one line only, say Ha, O[iII] or S[iI] and a colour or monochrome sensor. You take images in 3 filters and combine them, a bit of PS jiggerypokery and your done

as correctly stated the filter you have is not IR blocked, meaning if you image through a refractor, it wont bring the IR to the same focus as the Visible light. You image will look a bit fuzzy. Also your camera isnt optimised to receive NIR light, so its best policy to block it when imaging

the eye is NIR blocked :) so this is more a visual use filter, though it can be used with either an IR block filter or your colour ccd which you have said is IR blocked.

hope that helps

paul

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