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Equipment Discussions >> Electronically Assisted Astronomy

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Atl
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Reged: 04/13/12

Does a SCT need an IR filter for imaging or video? new
      #5807508 - 04/18/13 07:05 PM

That is my question. Thanks for a response in advance.

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GlennLeDrew
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Re: Does a SCT need an IR filter for imaging or video? new [Re: Atl]
      #5807915 - 04/18/13 11:22 PM

I don't use such a filter with either of my 80mm f/5 achro w/ MFR-5 reducer and 8" SCT w/ 0.33X reducer, with my VSS+ attached. I see no real need. Star images are as crisp as they're going to be, and there are no discernible color oddities...

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robininni
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Re: Does a SCT need an IR filter for imaging or video? [Re: Atl]
      #5807921 - 04/18/13 11:24 PM

It is my understanding that it does not unless you are using lenses (focal reducers, field flatteners, etc.). IR cut filters are for refractors OR other lenses that cause the infrared light to focus differently from the visual light causing muddy images.

Rob


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Atl
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Re: Does a SCT need an IR filter for imaging or video? new [Re: GlennLeDrew]
      #5808011 - 04/19/13 12:36 AM

Thanks for the info. That has been a confusing issue to me. I am not a big fan of filters. My experience with various nebula filters is that they reduce the overall light that reaches the eye.

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nytecam
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Re: Does a SCT need an IR filter for imaging or video? new [Re: Atl]
      #5808115 - 04/19/13 04:06 AM

Quote:

That is my question. Thanks for a response in advance.


I don't use IR-block filter for my SCT imaging even though I use focal reducers [lenses] - under test IR light contributes noticeable to image density - maybe 30%. Blocking IR effectively needs a longer exposure and in brief [video] exposures we need all the light we can get.

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rmollise
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Re: Does a SCT need an IR filter for imaging or video? new [Re: robininni]
      #5808481 - 04/19/13 11:04 AM

Quote:

It is my understanding that it does not unless you are using lenses (focal reducers, field flatteners, etc.).

Rob




Nope, not even if you are using reducers--as almost all folks doing video do. They are helpful for refractors in keeping star bloat down.


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