Unusual R-C Light Leak - HELP!

Acquisition Deep Sky
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Gary Seven avatar
Gary Seven avatar
I have an unusual light leak problem with an iOptron (GSO clone) 10" truss tube R-C. There is a severe lightening in one of the corners.

- It is only visible in Red and Luminance. Absent in any other filter position.

- It is absent with the same camera and filter wheel on my Takahashi Epsilon.

Has anyone seen this before? Ideas?

masterLight_BIN-1_6248x4176_EXPOSURE-180.00s_FILTER-L_mono_autocrop.jpg
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andrea tasselli avatar
andrea tasselli avatar
I would be more concerned about the stray light from an off-side star if I were you. When I get a bright corner (or side) is usually some stray light from the neighbours' security light (thanks so much!).
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SonnyE avatar
SonnyE avatar

Not having a truss type RC, I have seen where many use a shroud on theirs, which could help control stray light.

Much like my dew shields do for my refractors.

If you could do a live view you might be able to move a shade around to find where the light is coming from.

Like Andrea sez, maybe a neighbor or even some more distant light source is buggering you up?

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Brian Puhl avatar
Brian Puhl avatar

Red light in the corner, probably coming from a red light on your mount, or something bright and red near the scope. Seen it before.

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Tony Gondola avatar
Tony Gondola avatar

andrea tasselli · Mar 13, 2026, 04:13 PM

I would be more concerned about the stray light from an off-side star if I were you. When I get a bright corner (or side) is usually some stray light from the neighbours' security light (thanks so much!).

And it should be noted that if there’s a security camera nearby it’s illuminating the area in the near Ir 24/7

Gary Seven avatar
Gary Seven avatar

andrea tasselli · Mar 13, 2026 at 04:13 PM

I would be more concerned about the stray light from an off-side star if I were you. When I get a bright corner (or side) is usually some stray light from the neighbours' security light (thanks so much!).

Definitely stray light source - but my neighbor is also an imager - he is exonerated ;-)

I’ll start taping all of those LED’s in the dome.

Gary Seven avatar
Gary Seven avatar

SonnyE · Mar 13, 2026 at 05:15 PM

Not having a truss type RC, I have seen where many use a shroud on theirs, which could help control stray light.

Much like my dew shields do for my refractors.

If you could do a live view you might be able to move a shade around to find where the light is coming from.

Like Andrea sez, maybe a neighbor or even some more distant light source is buggering you up?

Ordered!

Over on the CN Cass & Casses forum, users are installing flocking paper in their baffle tubes and praise it highly. I own such a scope and ordered the paper, but have yet to install. I will try it in the R-C first.

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Gary Seven avatar
Gary Seven avatar

Brian Puhl · Mar 13, 2026 at 06:31 PM

Red light in the corner, probably coming from a red light on your mount, or something bright and red near the scope. Seen it before.

I just processed my M97 data - the project was 90 minutes shy of my desired exposure time in H-a and Oiii, but I wanted to see if the problem was present in that data.

And it is in both H-a and Red. Minimal to nothing in Blue, Green, and Oiii. Hopefully MSG and DBE can tame it.

I think the camera and filters are cleared. I spent all fall and winter with the f/3.3 Takahashi in the dome, zero problems. The issue is the baffling of this scope.

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SonnyE avatar
SonnyE avatar

Gary Seven · Mar 13, 2026, 08:50 PM

Brian Puhl · Mar 13, 2026 at 06:31 PM

Red light in the corner, probably coming from a red light on your mount, or something bright and red near the scope. Seen it before.

I just processed my M97 data - the project was 90 minutes shy of my desired exposure time in H-a and Oiii, but I wanted to see if the problem was present in that data.

And it is in both H-a and Red. Minimal to nothing in Blue, Green, and Oiii. Hopefully MSG and DBE can tame it.

I think the camera and filters are cleared. I spent all fall and winter with the f/3.3 Takahashi in the dome, zero problems. The issue is the baffling of this scope.

I friend of mine has/had a truss type RC and his problems were quite baffling… His seemed to take as much maintenance as a B-1b bomber.

But when it worked, Ooh La La, what a great picture!

Hope it works out for you!

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