Old 15-11-2020, 01:49 PM
evltoy (Wayne)
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evltoy is offline
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Location: Melbourne
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Setting up the optical train with filters

Hi Guys,

I'm kind of getting a little confused on what filters and how to setup the optical train for some DSO on with my (unmodified Nikon D80) DSLR and Celestron C8.

Frist off. Do I require an IR cut filter to be in front of the DSLR no matter if I have other filters in the optical train? If so would it be wise to put a filter draw in front the the camera and just drop in a 1.25 IR cut filter?

Also will my images benefit with the use of LRGB filters with my unmodified camera with or without the IR cut filter?

What would be the priority, IR or LRGB filters?

The idea I have is from the C8 I will have a reducer -> T-Adaptor (M42) -> Filter wheel -> M42 spacers (if required) -> Filter draw (with IR cut) -> T-ring

The above idea was also going to be used with an Astro Camera too.

Thanks in advance for your input.
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Old 15-11-2020, 02:40 PM
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Craig_ is online now
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Your filter requirements may differ based on the unmodded Nikon D80 DSLR vs the astro camera (which isn't specified?)

I am not sure I see any point in using LRGB filters on any sort of colour camera be that astronomy OSC or a DSLR. LRGB filters are for mono cameras.

I would similarly assume that an IR Cut filter is not required on an unmodded DSLR as the sensor already includes a filter which cuts IR.

I can't comment on your proposed optical train as I'm not familar with your scope but your filter questions seem to be solving for two different cameras: you may want to use an IR cut filter imaging on an astronomy OSC, but you should not need one on a unmodded DSLR. You may need LRGB filters if the astronomy camera you refer to is mono, but if it is colour these would also be redundant.

In more general terms, you would not generally need to stack filters as you suggest here. LRGB filters should also cut UV/IR, so you do not need to use both at the same time. That said I am sure quality varies between brands so some may do a better job of cutting UV/IR than others.
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Old 15-11-2020, 05:48 PM
evltoy (Wayne)
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evltoy is offline
Join Date: Sep 2020
Location: Melbourne
Posts: 30
Hey Craig

Thanks for your advice. My questions were many related to my unmodded DSLR which you have answered for me

The Astro camera which first will be a colour planetary camera will not require the LRGB filters as you have said, but I will need the IR cut filter for it. Then down the track will come a more specific DSO astro mono camera

You have pretty much answered my questions... thank you
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