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Unmounted Chroma Filter Orientation

Chroma Lum
3 replies•145 views
John Binney avatar
John Binney avatar
I have recently purchased a set of unmounted Chroma filters. I have been trying to get clear instructions on which side of the filter faces the camera. The manufacturers say it doesn't matter. Cloudy Nights has several long discussions that agree it does matter but do not come to a clear conclusion. I appears most people suggest either the top of the text is towards the camera or the reflective side is towards the OTA. Others suggest try one way and if that doesn't work flip the filter to see if that gives a better result.
For a very expensive set of filters this is not satisfactory. If anyone from Chroma reads this can they please advise how they set up the bare filters in the filter ring for mounted filters.
Alternatively, if any reader is 100% sure which way the filters are fitted their advice would be much appreciated.
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Rick Krejci avatar
Rick Krejci avatar

My chromas are set up coated/shiny side toward the OTA and I’ve had no issues. You can tell the coated side by holding something like a cloth/qtip up close to the surface, there should be a single reflection with no gap between the object and reflection. That’s the general recommendation for most filters to minimize reflections bouncing between the sensor and filters.

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Glenn Baxter avatar
Glenn Baxter avatar
Got an unmounted set at the start of the year and knew about the controversy so had to try both ways for myself, as I think you'll end up doing for peace of mind. Didn't make a difference for me.  "Bottom of the text to the sky" is the consensus so I just left them like that in the end. There seems to be plenty of examples where it does make a difference though. Perhaps it is scope or placement related.
Tony Gondola avatar
Tony Gondola avatar

The way I have always understood it is the side that looks like a mirror needs to be towards the sky. Reflective side out.