issues w/ Nikon trinocular eyepiece tube " F " (trinocular head)

[WaterGoblin]

The top viewport on my trinocular head doesn't work. Unlike most heads, this one doesn't have a slider, I looked it up and the manual (https://neurophysics.ucsd.edu/Manuals/N ... ctions.pdf) says this:

When using the trinocular eyepiece tube
" F "
As shown in Fig. 8, when the observation
tube is turned toward the user, 100% of
light enters the observation tube.
Observation
tube 100%
Fig. 8
As shown in Fig, 9, when the observation
tube is revolved 60° leftward, 100% of light
enters the vertical photo tube.
In either case, turn the tube to the limit.

I tried spinning the top part while looking at a glowing light bulb trough it but nothing works:

Any idea what I'm supposed to do?

[WaterGoblin]

basically, no light passes trough the top viewport of my trinocular head

[PeteM]

The head moves from viewing through the eyepieces to a clear path (no glass) direct to the trinocular tube by having the head fixed on the stand and then rotating the entire binocular portion about a quarter turn. It could be that you're just trying to rotate the trinocular tube versus the body? The rotation needs to be with respect to the dovetail.

The "F" head is a good choice for photographers since it provides all the light to the camera when needed, with no additional glass in the way to gather dust or defects.

[blekenbleu]

The "F" head is a good choice for photographers since it provides all the light to the camera when needed, with no additional glass in the way to gather dust or defects.

It turns out that Trinocular "F" heads came with at least two different "chimneys":

• one disassembles to expose a 38mm DIN photo tube

• another is one piece

• either can be completely unscrewed from the head

The head's photo port has a recessed 42mm thread;
a mirrorless digital camera adapter can be improvised.

M200.jpg (22.34 KiB) Viewed 17191 times

Whether a DSLR will work depends on its flange-to-sensor distance.

These parts comprise an adapter:

• 42mm-39mm step-down ring, e.g. https://www.ebay.com/itm/253981920429

• 39mm filter e.g. https://www.ebay.com/itm/373952962485

• M42 to M39 focus helicoid

• M42 T2 male coupling ring e.g. https://www.ebay.com/itm/165634683808

• thin 42mm mirrorless camera flange adapter

Known to work: https://www.ebay.com/itm/304855693654 for Canon EOS M, M2, M3, M5, M6, M6 II, M10, M50, M50 II, M100, M200
For mirrorless cameras, a helicoid with 17-31mm focus range works. I recommend brass helicoid tube, e.g. https://www.ebay.com/itm/164318262310
This amounts to about US$65

[sreynolds]

[re. 'F' head tall/short chimney] either can be completely unscrewed from the head

I had an 'F' head with the tall chimney and could not unscrew it from the body/dovetail. Since the binocular viewing part is rotated to change from eyepiece to photoport, there must be stops that limit both ends of the rotation, and when trying to unscrew the chimney I believe I was pushing against one of the stops, and afraid I might put something out of alignment. I applied pretty strong force without effect. I suspect you need to put the dovetail in some kind of vise to loosen that chimney, so the torque is applied to the dovetail and not the rotational stop. Am I right? Anybody actually done this?

[blekenbleu]

I applied pretty strong force without effect.
I suspect you need to put the dovetail in some kind of vise to loosen that chimney,
so the torque is applied to the dovetail and not the rotational stop. Am I right? Anybody actually done this?

My hand strength may be greater than average, but was able to unscrew the short 38mm photo tube from "F" head by one hand,
as was another owner with the one piece chimney,
holding "F" head with other hand, disconnected from Optiphot; no strain on circular dovetail stops.
Nikon seemingly applied no thread locker to those threads, but strain was required to loosen it.

Consider a strap wrench https://www.amazon.com/dp/B003UDS83U, which can be handy for other torque applications on the chimney, with the head held in a bench vise with padded jaws.