Focus

#578959
Hugh Allen
Participant

Hi David,

Congratulations on taking the plunge, I am sure you’ll really enjoy spectroscopy. I think a spectroscope is a wonderful observing tool but many starters seem to fall by the way side. I’d echo the advice to stay initially on bright targets, ideally A- and B-type main sequence stars that have strong Balmer absorption lines. This will allow you easily to see when things are not working so that you can quickly develop understanding of spectrum image capture and processing without losing heart. I think a key thing to learn is good focusing of the spectrum. Here’s a study I did on Vega with my Star Analyser 200 to find the optimum focus point for the sharpest spectrum (narrowest, deepest absorption line). It is not perfect focus on the star itself but slightly backed off. The Bahtinov mask focus image shows that very clearly. When I use my Star Analyser I begin each session by setting the focus on a bright A-type star. Good luck and of course feel free to ask any questions

Cheers

Hugh