Modded camera and Baader replacement filters

[kirkster501]

Hello, what do these filter do please? I am not completely sure. From what I can gather, the modification involves removing the harsh IR filter present in the DSLR from the manufacturer. That bit I get. But then it seems either a clear filter can be inserted in the place of the said filter to allow autofocus...? Does "in place of" mean literally where the original manufacturer filter sat over the CCD? Alternatively, from my understanding (which I am sure is wrong) a more active type of filter can be inserted instead like IR filter or OIII? But haven't we just removed the IR filter?

So in terms of these Baader replacement filters what type of filters can be inserted "in place of" the original? And why woudl I want one rather than the other?

Thanks, Steve

[kirkster501]

Anyone guys? Is this a daft question? Apologies if so, just seems a minefield of options when you remove the IR manufacturer filter and replace it. Was interested in what others had done.

I'll google some more and see what I can find.

[Merlin66]

OK here we go.....

There are two filter elements in a current Canon camera

#1 is a colour correction filter which is normally removed in a "mod"

#2 is a front anti-alias/ dust shake filter which is usually retained in a mod. BUT this filter also acts as a very effective UV-IR cut filter.

What this means is that NO additonal filters (Baader or otherwise) are required if you use the modded camera body on the telescope for astro work.

The replacement of #1 filter with either a plain glass or a Baader UV-IR filter (only because it's cheaper and readily available!!) is ONLY required if you need ACCURATE AF focusing with standard Canon lenses.

I have a modded 1000D ( both filters removed for maximum spectrum - for spectroscopy) and use a clip in Astronomik clear filter to regain the focus with standard EF camera lenses.

I can upload the spectrocopic transmission curves of each filter to confirm this.