Disassembly of the Lunt LS80 DSII etalon.

[pupak]

I received this etalon with a damaged collimating lens, so disassembly ensued. The Etalon is surprisingly easy to dismantle by unscrewing the front part. The joint appears as a small groove about 1 cm before the end. A little more force is needed because the thread is sealed to hold the gauge pressure. The output positive lens is then freely accessible and its focus, which is 245mm, can be easily measured.
Since I probably won't get a new collimating lens, I will try to adjust the standard as naked with pressure tuning through the thread using a needle bearing.
I got another interesting toy.
Hopefully the work will be successful and the etalon will continue to serve.

[christian viladrich]

Very interesting. Thanks for sharing !

Could you post some pictures to see how it looks like ?

[pupak]

Very interesting. Thanks for sharing !

Could you post some pictures to see how it looks like ?

The net diameter of the etalon is 36mm. The front aperture is 35mm, the rear 33mm. On the outer edge of the lower screen there is a hole with a diameter of 1 mm that supplies air. It's a long slanted hole up to the pressure cylinder.

[pupak]

One more note about collimated etalons. I thought, and I'm not alone, that the position of the etalon relative to the back focus is not critical. This is a big mistake. Since we did not know the focal point of the collimating lens and set the position by measuring with little accuracy, probably no one hit exactly the right place at 0.1 mm. After measuring the focus of the collimating lens, I adjusted the position of my etalon and the quality of the contrast and homogenity is completely different. Evidently a deviation of +- 1 mm already plays a role there.
It's enough if you do simulations in Optgeo and it's very easy to see.

[christian viladrich]

Thanks for the pictures and for the info !

[marktownley]

Thanks Petr.

[pupak]

An attempt to modify the etalon for mechanical pressure tuning failed. The construction of the etalon is obviously different from other types. A lot of material and work went to waste, but hopefully this information will help someone avoid a similar situation.