I have recently procured a sample of the Radian Triad Ultra (used) and the Antlia ALP-T, and have been working on some testing to compare how these filters perform relative to each other. To fill out the comparison I have also included some other well established filters:
- Baader Planetarium UV/IR Cut ($127)
- IDAS NB1 ($199)
- IDAS NBZ ($299)
- Optolong L-eXtreme ($309)
- Radian Triad Ultra ($1075)
- Antlia ALP-T ($380)
My testing included both imaging and bench top spectrometer measurements. I intend to put a test report together eventually, but figured I would share my test results so far. You can view my image captures at the Flickr link below. Also posted to the album are my measured filter spectra, plotted assuming a few different telescope f-ratios.
My initial take-away is that the difference in performance between the NBZ, L-eXtreme, Triad Ultra, and ALP-T is pretty subtle. Based on what I am seeing, I don't understand why anyone would pay $1075 for the Triad Ultra when it does not perform significantly different from filters 1/3 the price.
I will update the thread as I get more of my data reduction completed.