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This seems incorrect. Everywhere I look I hear effectively:

> All refractive optics require IR filters.

The reason seems to be it prevents "bloating" of bright points of light - eg stars, and increases contrast in the visible range by cutting off UV and IR (which CCDs are apparently sensitive to), so it is in fact desirable to have IR filtered out.

Now, does that mean it's default? Maybe not.

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Possibly desirable for optimal image quality, sure, but taking pictures is not the only use for a telescope. Many things just require knowing how much light is present, and how that changes over time. Occultations are one such case which I have familiarity with. Objects are often so faint that every little bit of light is essential to improve SNR - https://occultations.org/

IR filters are generally pretty effective too, so just having one anywhere will do the trick unless you're dealing with a lot of light. Cameras which would be undesirably sensitive to IR would usually have the filter built in, basically right on top of the sensor. No need for added coatings on the telescope itself.

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