Adjustable IR filters

[bojan]

While browsing on ebay, I found this filter:
http://www.ebay.com.au/itm/Adjustable-Optical-Infrared-IR-Pass-X-Ray-Lens-Filter-77mm-530nm-to-720-750nm/371421074803?ssPageName=STRK%3AMEBI DX%3AIT&_trksid=p2060353.m1438.l2649&autorefresh=true

I will buy it for sure... in the meantime, did anybody try to use it and what were the results?

[luka]

Could not find much about them apart from this forum post (http://www.apug.org/forum/index.php?threads/adjustable-infrared-filter.139019/) and not so favourable reviews here (https://www.lifepixel.com/photography-gear/variable-infrared-filters).

To quote:


What do you plan using them for?

[bojan]

Idea was to use it for AP in IR... IR spectroscopy as well.

[luka]

You can probably get rid of the cross pattern using flats in AP.

[Merlin66]

Bojan,
For IR spectroscopy, besides having a suitable sensitive camera all you need is a Red sorting filter - something like a Wratten 25 - this will suppress any overlap with the 2nd order at higher wavelengths (>7500A)