DSLR Mod: Installing a Narrowband Filter Directly on the Sensor (Results Included) - Forums

Hello everyone!

I wanted to share a super fun mod I did on my DSLR in case anyone is interested or has feedback — or if someone out there has tried something similar!

I recently sent my main astro rig to a remote observatory, and honestly… I started missing those camping nights under the stars way too much. I didn’t want to spend another fortune on new gear, so I decided to work with what I already had and build a capable imaging setup.

I’m using a Nikon D810 that was previously modded (one internal filter removed) to make it more sensitive to Hα. But I really wanted to use narrowband filters with it and with all my lenses from fast to slow and wide to zoomed in. As many of you probably know, dual-band / clip-in narrowband filters for Nikon FX DSLRs are very limited. So I tried 3D-printing an adapter to hold a 2” round filter in front of my lenses — and it kinda worked, but I ran into major issues:

Problems with the 2” Filter Adapter

Extreme vignetting — even at low f-stops and longer focal lengths
Terrible star shapes at anything faster than f/4
Completely unusable with wide or ultra-wide lenses

So… I started thinking differently. What if I put the filter right next to the sensor? And eventually — what if I actually placed it directly ON the sensor with no space in between?

I couldn’t find any guide or post about doing this — so I just went for it!

Here’s what I did:

Bought an Optolong L-eXtreme clip-in filter for Z-mount
Used acetone to dissolve the glue and free the filter glass (tested it first on a cheap filter to make sure the coating wouldn’t be dissolved!)
Disassembled my Nikon D810 and removed the middle sensor filter. (This is what normal mod for Nikon DSLR is)
Placed the Optolong glass between the sensor and the dust-protection filter
3D-printed tiny spacers to keep it firmly in position
“Sandwiched” the narrowband filter in place (sensor → filter → dust cover)
Reassembled the camera just enough for testing
Moved the sensor forward so infinity focus would work again (the extra filter thickness changes the focus plane)
Took some test shots and adjusted sensor tilt until the stars looked clean

Removed one of the memory card readers — this gave the sensor direct airflow and helped cool it much better than before

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Camera looks the same as original from outside, no change in mirror, focusing or measuring system.
Shutter Cover/blade is fully functional as original
Behind the shutter blades, you can see the Dual-band filter behind dust protection filter.
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and finally, you can see the memory card reader that I removed to give the back of the sensor access to direct airflow.
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