Positioning of an IR filter

Hi Folks

I took the plunge and ordered a Mono DMK DMK 31AF03.as and filter wheel, for the jump to RGB imaging and was wondering if the positioning of the IR filter makes a difference to the resulting image quality.

For example, would having the IR filter in the nose piece of the Filter wheel, sitting in front of the R,G and B filters in the wheel yield different results than having the IR filter in the Camera nosepiece, behind the three filters in the Wheel?

Many thanks

Steve,

The positioning of an IR filter is generally not important. There is a small caveat here. Most filters in one way or another, change the focus position a tad. So if you have an IR filter in front of the colour filters the focus position between the colour and luminance filters will be just a tiny bit different. (because there is no colour filter behind the IR on the luminance frame. This might not be noticeable but could be on a night of excellent seeing.

The solution is to get good quality interference filters from the beginning. You wont need an IR filter with these colour filters since they already have UV/IR cutoff built in. Astronomik filters are what I (and Carl) uses and they are excellent and all totally parfocal.

Steve,

Further to Dave's comments, I picked up a set of brand new SBIG filters which are IR-blocking for $100 ... plus $12 for shipping.

Because many people are moving up to 2" filters, you will find lots of good deals on Astromart. Just exercise some patience as usual.

Thanks lads....... you guys are the best!!!

I'll most certainly look into the interference filter options. The Astronomiks seemed impressive alright, when Carl showed them to me when I was up yonder in Balbriggan!!