1.25" filters

Astrodon H-alpha 5nm 1.25" Chroma OIII 3nm Bandpass 1.25" Chroma SII 3nm Bandpass 1.25" Filters
1 reply•18 views
Tareq Abdulla avatar
Tareq Abdulla avatar

Hi all,

I have filters since long time ago at size of 1.25”, i bought them at good old prices, and i will not sell o give up them, but now having APS-C sensor cameras, how to use those filters then? I don’t like that 1” square sensor or even smaller one with IMX585, so what solution i can have t use those filters without selling them?

The filters are: Astrodon Ha 5nm 1.25”, Chroma OIII/SII 3nm 1.25”.

Tony Gondola avatar
Tony Gondola avatar

The clear area of a 1.25” filter is between 24mm and 27mm. The average diagonal measurement of an APS-C senser is 28mm. You are going to have clipped corners even with a very slow system. I guess you have a choice, wait until a small senser that you like is developed or learn to love the 533/585 class of sensors.

Helpful Concise
Related discussions
Keep or sell my Optolong filters?
Hi, I have Optolong SHO filters with 6.5nm and 7nm 36mm since 2018, and i used them several times in the past without nice results due to LP in my area, and later when i added 3nm filters i no longer using those Optolong 6.5nm/7nm filters anymore, bu...
Author has similar narrowband filters; discusses keeping versus selling equipment.
Aug 22, 2025