This paper demonstrates the use of CitNetExplorer and VOSviewer to cluster scientific publications and analyze the resulting clustering solutions. CitNetExplorer, a software tool for analyzing and visualizing citation networks, is used to cluster a large set of publications in astronomy and astrophysics based on direct citation relations. VOSviewer, another software tool for constructing and visualizing bibliometric networks, is used to analyze the clustering solutions at an aggregate level. The paper highlights the complementary visualizations provided by both tools, with CitNetExplorer focusing on individual publications and VOSviewer on aggregate-level analysis. The clustering technique used in CitNetExplorer is based on maximizing a quality function that determines the relatedness of publications through direct citation relations. The paper also discusses the clustering results for a dataset of 111,616 publications in astronomy and astrophysics, providing insights into the topics covered by different clusters and the citation relations between them. The authors conclude by emphasizing the ease of use of the freely available software tools and their potential for sophisticated cluster analyses without requiring deep knowledge of clustering techniques or advanced computer skills.This paper demonstrates the use of CitNetExplorer and VOSviewer to cluster scientific publications and analyze the resulting clustering solutions. CitNetExplorer, a software tool for analyzing and visualizing citation networks, is used to cluster a large set of publications in astronomy and astrophysics based on direct citation relations. VOSviewer, another software tool for constructing and visualizing bibliometric networks, is used to analyze the clustering solutions at an aggregate level. The paper highlights the complementary visualizations provided by both tools, with CitNetExplorer focusing on individual publications and VOSviewer on aggregate-level analysis. The clustering technique used in CitNetExplorer is based on maximizing a quality function that determines the relatedness of publications through direct citation relations. The paper also discusses the clustering results for a dataset of 111,616 publications in astronomy and astrophysics, providing insights into the topics covered by different clusters and the citation relations between them. The authors conclude by emphasizing the ease of use of the freely available software tools and their potential for sophisticated cluster analyses without requiring deep knowledge of clustering techniques or advanced computer skills.