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

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

1. Extreme vignetting — even at low f-stops and longer focal lengths

2. Terrible star shapes at anything faster than f/4

3. 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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