LS50F: is there vignetting?

[Merlin]

I have a LS50F etalon double-stacked to a PST and it gives good results, showing a mass of sharp solar detail on good days of seeing. But, can anyone say if the Lunt etalon is vignetted by the PST's 40mm diameter objective?

When the beam leaves the back of the etalon is it narrower than when it entered, allowing it to slide through the PST objective without vignetting?

[cdd2455]

Hi Merlin

A front mounted etalon such as your LS50F has no lenses in it to focus the incomming light, 50mm aperture in at front & 50mm aperture out at back, so yes, your PST 40mm will vignette the 50mm aperture of your LS50F.

Best Regards

Carl

[Merlin66]

As Karl said, the PST objective will act as an aperture stop to give you a 40mm f10 system.

The front etalon combo will give a reduced bandwidth (around 0.5A) and should show the solar surface in better contrast.