Hartung's Prism

[Kev11]

Thanks to Markus (Stonius) I too have the reprint of Hartung’s. Reading the descriptions I frequently see reference to “prism”. For example in Centaurus: NGC4976 “...single prism image...”; NGC5307 “...bright single image in the prism”
The guide to observation section has a brief discussion of spectroscopy and a mention of Hartung’s DIY prism.
My question is: how useful do people feel it is for a visual observer not interested in spectroscopy as such to own such a device, which I gather is mainly to distinguish or enhance nebulas?
Cheers
Kevin

[Merlin66]

Think about the simple 60 degree prism in this context as a "nebula filter".
The smaller prisms are pretty cheap and can be mounted in/ through a plastic film cassette which can then be aligned behind the eyepiece to allow emission line objects to be better seen.
I have one I made up in the 1970's. Very easy, very simple, very effective.

[Merlin66]

The attached images show the simple arrangement.
The canister it held against the eyepiece and the FOV viewed through the opening......

[Kev11]

Ken, thanks for anticipating my next question with your photos.
Cheers
Kevin