Masking the window heating (Altair 533M)?

[GTom]

The window heating wires on my camera seem to be quite reflective, shall I cover this part of the window with some kind of matte tape?

 

[Oddsocks]

Don’t use tape anywhere near optical components, especially heated ones!

The tape adhesive will migrate across the window over time and probably require solvent to remove, which might damage any coating applied to the window.

Masking the window to reduce the chance of reflections is a good idea however and these days with easy access to 3D printers, either self printed at home or via a printing service, it is quite simple to create a field stop diaphragm in black plastic that clips into the open port of camera, secured against falling out by friction fit alone via the baffling of the camera attachment port, or threaded if the baffling is a continuous thread and not concentric cuts, and leaving just the sensor area itself visible through the field stop diaphragm.

You would need to sit down with drafting paper (or use a CAD program) to determine the size of the opening in the field stop diaphragm to not intrude into the focal path and obscure the sensor, and for a square sensor a square field stop aperture will allow for a smaller sized opening and better masking of the gold heater matrix behind than a plain round aperture mask.

Printed plastic is itself quite reflective but that can be reduced by flattening/matting with wire wool.

Try the camera first, you might not see any scattered back reflection of the gold heater matrix from other optical components close to the camera anyway (filters, reducer-flatteners etc.,), but if you do then a simple field stop diaphragm that needs no adhesives to fix in place is the only safe option IMO.

Edited July 8 by Oddsocks

[GTom]

Tried with just a piece of blackened cardboard, no adhesives. The thread holds it nice in place, covers the wires fine. So far I can't see a difference in the flaring pattern of my trusted old 1.8/50 nikkor but doing no harm it'll remain in place.

When I get the time I'll print a black plastic unit that screws in.

Edited July 8 by GTom