DSLRs and IR

[Greenman]

As I am now in possession of a refractor a bit more suited to DSO’s I am considering cameras. Of course there are temptations to spend on a good ZWO for this purpose, but at the moment I need to sell some equipment to fund this. So I wondered about getting my EOS 100D modified to remove the IR blocking filter. But it appears now that the 100ED has a wider spectral range.

I had a look around for information on the sensors, but it seems that Canon are shy of releasing details (competitive secrecy I guess). However, I came across a blocking filter that had a bandpass above 720nm for the 100D to use it as an infrared camera. Exactly how far the camera’s extends sensitivity into the NIR, I am unsure, but it would be interesting to test it on some emission nebulae against comparative data.

I wondered if anyone here knows of the CMOS capabilities of the newer canons (100ED circa 2013). And how adaptable this camera may be without removing the IR filter?

[yobbo89]

Generaly you want to image with a ir/uv blocking filter for astrophotgraphy especially with a refractor , Newtonians are more suitable for full spectrum inc ir. As for ir imaging with a filter that blocks off everything but ir then a refractor I am unsure of, you loose alot of resolution imaging in ir and bigger appature helps. Generally alot of chips have a low or lower quantum efficiency in ir and it's even worst for colour chips.

The 100d seems to have a 43% qe, I'm guessing that's peak in the red end..

https://www.astrophotography.app/EOS.php

[Greenman]

Generaly you want to image with a ir/uv blocking filter for astrophotgraphy especially with a refractor , Newtonians are more suitable for full spectrum inc ir. As for ir imaging with a filter that blocks off everything but ir then a refractor I am unsure of, you loose alot of resolution imaging in ir and bigger appature helps. Generally alot of chips have a low or lower quantum efficiency in ir and it's even worst for colour chips.

The 100d seems to have a 43% qe, I'm guessing that's peak in the red end..

https://www.astrophotography.app/EOS.php

Hi Yobbo,



Thanks for the input, I hadn’t realised that in general a refractor, needed IR blocking. I had also thought that some of the emission line filters were in the IR but taking a look at Astronomik tells me I’m mistaken. The pass filter is not one I intend to use, I wasn't clear enough, I was commenting on the fact that there must be sensitivity above 720nm on the 100D sensor.

It sounds as if I just leave things as they are, a good result!

Oh, on a sensor the normal practice is to quote both average QE & resolution. Useful table that thanks for the link.

[yobbo89]

if your intentions was to gain some more ha signal as well then you should absolutley do that , the low pass filter on dslr chips block part of the ha spectrum, you'll still need to add a ir and uv blocker after the mod, i just think going fully ir for dslr and astro isn't going to give good results because of how much more exposure time you need due to the low qe, it will be fine for day time stuff with a dslr lense..