8 replies to this topic

[dagree]

Hi people

 

I know that this sounds like a dumb question, so please bear with me if it is.

 

I am shooting with a full spectrum (no UV/IR cut filter) modified Sony a6000 and a duo-band filter (STC Astro Duo-Narrowband Clip Filter) that should only let in light around 500nm (OIII) and 656 (Ha). However, I recently noticed in the documentation of the filter that it also lets in light below 350nm. As my camera is full spectrum, I am not sure if light in that range is being filtered and if it is a problem for my astrophotography if it is not being filtered - any experts who can help me answer that?

 

I guess I could always add a UV/IR cut filter on top to be on the safe side, but the less glass the better.

 

Thanks,

Niels

 

[bobzeq25]

Your camera still has a Bayer matrix filter for color over the sensor.  That system has little response at wavelengths shorter than 350.

 

https://pic4.zhimg.c...b7cd5bce2_r.jpg

The filter will block the relevant IR.

 

https://nimax-img.de...d-Filter-2-.jpg

 

So, no.

 

Take home message.  Look at spectral response curves.  Google is a good source.

Edited by bobzeq25, 20 July 2022 - 10:08 AM.

[bobzeq25]

Your camera still has a Bayer matrix filter for color over the sensor.  That system has little response at wavelengths shorter than 350.

 

https://pic4.zhimg.c...b7cd5bce2_r.jpg

 

The filter will block the relevant IR. 

 

https://nimax-img.de...d-Filter-2-.jpg

 

So, no.

[dagree]

Thanks, makes sense. 

[buytaert]

Hello,

 

I am also considering to remove the stock glass form my A6000 to make it sensitive to Ha. Since you did not replace that glass with anything else, I wonder if you are stil able to get focus at infinity with a lens ? Or are you using your camera only with telescopes ?

Did you look for a UV/IR replacement ?

Many thanks for your answer, Jan

[Digitaliz.se]

I looked at the spectrum of that filter. I cant see it leta UV in. Where did you find that documentation?

[buytaert]

I looked at the spectrum of that filter. I cant see it leta UV in. Where did you find that documentation?

I am not sure that I understand your question... I have no documentation on the original glass filter that is in place. But if it is removed and not replaced by glass with a similar thikcness, the optical lenght is shortened and the sensor should be moved forward to reach focus when used with a lens (not the case if used with a telescope). Therefor I was looking for a replacement glass with a pass between 400nm to 700nm, because I want to keep using my 135mm lens with this camera.

Are you still using your A6000 with a lens ? If so, can you still reach focus without a replacement of the original glass  ?

Regards, Jan

[Digitaliz.se]

Sorry,
The filter is just letting Oiii and Ha pass. I looked at the spectrum of the filter so it doesnt matte that the camera is full spectrum modded.

[GR-Amateur]

Some filter need additional filters, some filters don’t need, an example here below. I have this filter (IDAS NB3) and I confirm that shooting with a full spectrum camera without IV/UV cut filter is a mess. Anyhow, filter makers are usually share the band pass charts and clearly state in the specs whether you need or not an additional filter to shoot with.

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