DIY prism shift image stabilisation for spotting scope/telescope/monocular (1 Viewer)

[Richard D]

Ive no idea whether this will work, but I'm enjoying the experiment.

 

[kimmik]

Ive no idea whether this will work, but I'm enjoying the experiment.

Couldn't have phrased it better myself lol.

Mirador 30x75 original Porro prism:

New Schmidt Pechan prism mounted on 2 axis "gimbal", made out of a speaker diaphragm. Next step is to attach 2 actuators at 90deg orthogonal.

 

[kimmik]

Actuators and connections completed!

Arguably the next steps are more complicated, as I am new to programming.

 

[Binastro]

Is the Mirador 30x75 drawtube scope a prism design rather than a relay lens?

If a Porroprism it is probably more accurate than a roof prism.

The laser seems too abrupt and maybe too slow.

Maybe a sinusoidal movement is needed?

I suppose the frequency and amplitude have to be optimised.

Of course it is beyond my capabilities.

I can't even work a computer.

Regards,
B.

 

[kimmik]

Hi B, correct it uses porro prisms for image erection, and an additional parallelogram shaped prism to make the eyepiece centred. It seems excessive in fact, as removing the prisms made the image far brighter and with more contrast. The prism surfaces may in fact be uncoated, I'm not sure.

Presumably it was done this way to reduce the scope length, as a relay would have been much longer.

Objective lens measures 75mm doublet, 360mm focal length, so around f/4.8.

Weight was originally 1250g. Removing all armour and the prisms is 1050g.

 

[kimmik]

Video through the modified telescope - this is demonstrating the opposite of "stabilisation", as the telescope is mounted, and signal input is manual and thus induces instability. 15% power level 0.5v rms 30mW.

 

[Binastro]

Ah.
It is so much better when the stabiliser is turned off.

The parallelogram prism is interesting, as I wondered how it could be centred.

A relay lens system would probably have had a small field.

Does the stabiliser need damping if you get it to work?

Regards,
B.

 

[kimmik]

I’ve wondered about damping too, the canon lens i took apart had small silicone grommets for damping and suspension.

The speakers probably provide enough damping as the video showed.

 

[kimmik]

This video tutorial shows the source code required for a gyro controlled stabilizer - it is beyond my time commitment to learn unfortunately, so will have to stop the project at hardware development.

The video does show that the programming required is possible at the DIY level using a common arduino uno.

Later I will hook up both axes of the prism shifter and power up to 100% for a demonstration then call the experiment concluded .

 

[kimmik]

Block diagram of a potential complete IS telescope design: Arduino microprocessor, MPU6050 gyroscope, MCP4725 DAC, PAM8403 amplifier.

 

[kimmik]

Blueprint for a full system, pocket IS telescope

25x50
f3.5 175mm focal length
Helical focuser at front, like camera lens
Waterproof with internal rechargeable battery, like gopro but serviceable
UsbC charge port, under waterproof cover, like gopro
Transitions seamlessly to non-IS telescope when out of battery
Prism shift 2 axis stabilisation
1degree shake compensation like a canon
Same area footprint as iphone
Weight around 600g

 

[kimmik]

Update to the project, found a suitable prism gimbal and installed into the mirador 30x75, in place of the original fixed porro prism.

Currently the issue is reprogramming it for the correct amount of shake correction. As is, it works optically as a typical draw tube telescope, brighter than the original given the modern coatings of the new prism.