Filter advice please

[Gina]

I've been having another go at super cooling an 1100D now that I have succeeded in converting the sensor to mono by removing the Bayer matrix (Colour Filter Array). This involves having a sealed chamber with desiccant to remove the moisure and prevent misting of the sensor when it's cooled well below freezing. So I need an optical window to seal the light path and it seems to me I might as well combine the sealing properties with a filter for light pollution or at least IR/UV blocking. So... possible options :-

1. IDAS LPR filter - expensive - http://www.firstligh...ion-filter.html
   
2. Baader Neodymium Filter - http://www.firstligh...ium-filter.html
   
3. Baader IR/UV blocking filter - http://www.firstligh...cut-filter.html
   

I'd welcome opinions, please, bearing in mind the camera will be intended for DSO imaging mainly NB and maybe luminance.

Thank you

[Oddsocks]

Hi Gina,

Do you have a bad Light pollution problem that requires the IDAS or Baader Neo?

If you are going to add narrow band filters externally then the IR/UV would be the logical choice to seal the chamber, the IDAS or Baader Neo would probably not work well in combination with an external narrow band filter, generally I've not had good results using two different interference filters at the same time.

If you used the IDAS or the Baader Neo to seal the chamber then you would be limited to just additional external RGB filters to give you the L-RGB image sets.

There is also the option of just a plain glass multicoated filter to seal the chamber like the QHY MC Nosepiece filter.

This would allow the NIR to pass through for luminance imaging and then additional external NB or RGB would block IR anyway.

Choice here depends on whether you are using a refractor, IR/UV blocking essential for luminance imaging, or a reflector, no need for IR/UV block as all wavelengths focused to same point.

http://www.modernast...iltersOther.htm

William.

[steppenwolf]

If 'twer me, I'd get a simple IR cut filter and leave all your other filter options open for the future, including the excellent IDAS LP filter if required.

[Gina]

Thank you for your replies William and Steve - that is exactly what I wanted to know Looks like the QHY IR nosepiece filter would be ideal then and less than half the price of the cheapest of my options

I only have any problem with light pollution low down to the S or SW - most of the sky is pretty good. All my optics contain refractive glass - even the MN190 to a lesser degree.

[StuartJPP]

If 'twer me, I'd get a simple IR cut filter and leave all your other filter options open for the future, including the excellent IDAS LP filter if required.

That is the correct answer

[Psychobilly]

For the older orange Sodium glow that I suffer from around here my prefered LP filter is the Hutech IDAS I have it in 2" , MFA (Canon APS-C in body ) and 77mm format For use with my 5D mk III. I have used the Astronomik CLS-CCD but it's my 2nd choice .. Also had othere filters includin the Lumicon abd BP offerings...

Peter...

[russellhq]

Gina, I've seen a company recommended here a couple of times that makes custom glass pieces at a reasonable cost. You should be able to get something made to your requirement for not much money.

Maybe someone else can remember their name...

[Gina]

Gina, I've seen a company recommended here a couple of times that makes custom glass pieces at a reasonable cost. You should be able to get something made to your requirement for not much money.

Maybe someone else can remember their name...

Yes, I've seen mention of that before - thank you   But I wonder how long they take to supply the goods.  I'd like to progress this project as fast as I can and an IR cut filter would mean I could get away with an empty hole for a luminance filter (though this would not be parfocal with other "filters")