Modifying My Canon T3i... Some Notes

Modifying my Canon T3i was nerve-wracking.   I put it off for about 6 months as I knew that the mod could destroy the camera.   When I finally decided to go for it, I consulted and studied Gary Honis' website where he gives very good step-by-step instructions on the whole process.

http://dslrmodifications.com/rebelmod450d1.html

Why the mod?   There are dozens of nebulous targets for the small to medium sized telescope that emit light in the H-alpha frequency.   H-alpha lies at 656.28 nm and it's basically a "deeper" red color that is mostly blocked by filters that sit in front of the camera sensor.    It can be picked up by a regular digital DSLR, but it is only let through at 20-30%.   By replacing the stock filter with one that lets through 90-95% of H-alpha means that you'll be able to detect and image a lot of nebula more efficiently with less exposure time.

In terms of replacement filters, there are two major "brands" and two kinds of replacement options.
As far as I know only Baader and Astrodon produce a UV/IR filter that can simply be swapped for the stock filter.   These special filters are similar to the stock filter except that they let more of the deeper red/near infrared onto the sensor.   But they still block the infrared and UV.   The other type of filter is a clear glass filter that doesn't really block anything.   The reason why an aftermarket UV/IR filter is desirable is that stars will begin to bloat in optical systems that involve refractive elements.   Refractor telescopes and camera lenses are always compromises in terms of performance and price.   Lenses that focus UV light to near IR light cost a lot of money because they require more expensive and exotic glass elements (and designs) to perform well.

I sent my first DSLR away a few years ago to Hap Griffin to have him do a full-spectrum mod which basically meant he removed the stock filter and left it as is.  It made the camera extremely sensitive to H-a.  But it wouldn't focus with my camera lenses (with some exceptions) and the color balance was really screwy.   Another problem was that the sensor became a literal dust magnet.   Before each session, I had to use a blower which seemed only to move the dust.

Thus, in an effort to gain the advantage of better H-alpha sensitivity and adding some dust protection, I went with the Astrodon UV/IR replacement filter.   I figured I'd save $200 bucks by doing the mod myself.   In actuality, since I had to buy $60-70 worth of special tools, it wasn't much of a savings at all.

(DISCLAIMER:  I AM NOT CONDONING THIS MOD.  YOU WILL LOSE YOUR CAMERA WARRANTY IF YOU DO IT.)

I didn't document the process comprehensively, but I did snap pictures along the way:

Trying to keep track of all the little parts as I disassembled:

Uh oh, what have I done?

Gary Honis' instructions include making a makeshift tool from a tweezer and rubber band segments:

 Here I'm trying to use the tool to pull some delicate cables from their connectors:

All the major cables are disconnected:

Here is the sensor assembly:

I've removed the stock filter assembly from the sensor assembly:

The mod requires that you remove the stock UV/IR filter front the plastic support assembly.   It is glued in with something that resembles silicone.   Though I used an exacto knife to remove a bunch of the glue, it wouldn't budge.   I applied some pressure to separate it and it cracked in half!    BUT the most alarming part was that I SAW AND FELT glass particles (and a fine mist) shoot toward my face.   I felt a piece hit my forehead.   I immediately dipped my head down, then slowly walked to the shower and took a very awkward shower to remove any tiny glass particles from my face, hair and eye area.

Here is the assembly with a vinyl-type of gasket that holds the filter in place.   The gasket was so stretched that I could't re-use it.  But everything worked fine without the gasket.

The Astrodon replacement filter glued in place.    I don't show it, but I used a 8x magnifying glass to inspect the replacement filter.   There were lots of pieces of dust that took a while to remove:

I waited two days for the silicone to cure before I reattached the filter assembly to the sensor assembly:

[Addendum to above image:   On the left side of the image, you can see detailed notes I took along with a drawing of a torx screw.   Perhaps the single most crucial aspect of the mod involves carefully noting the exact position of 3 screws that determine the "orthogonality" of the sensor to the expected plane of the image.   If one of these screws is out of whack, then the sensor plane will not be flat to the body.]

Everything going back to together.   There is a very congested area in the upper right of the sensor board here where 3 cables sit on top of each other.   After screwing this board back in place, I found I couldn't completely reseat two cables into their connectors.  So, I had to disconnect all the cables again and unscrew the board and THEN connect the TRICKY stacked cables FIRST then screw down the board.

Here is that tricky area:

Since I was so freaked out and annoyed, I neglected to document the last re-assembly steps.   Let's just say that I was extremely pleased and relieved when the camera started up again.