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A multiresolution approach to enhance small telescope data under non-ideal conditions

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Abstract

Astronomical imaging of a star cluster is one of the paramount ways to learn about stellar evolution, stellar dynamics. A large telescope is not generally accessible to all observers. In that context, small telescope observations with a proper denoising scheme can be an excellent alternative. This paper proposes a technique to denoise star cluster data using an undecimated wavelet transform, with a modified thresholding process. Our work aims to prove the effectiveness of such a wavelet-based technique on real-time data. We present drastically noise-infested observational data of the NGC 2301 star cluster, captured over five nights from Fr. Eugene Lafont Observatory, Kolkata. We observe that for highly noise-polluted data, the conventional methods of dark frame subtraction and flat frame division are inadequate to produce the desired quality of images due to functioning exclusively in the spatial domain. Thus, we take the wavelet-based multiresolution approach to ameliorate those raw images. We also introduce a modified thresholding function to modulate the image at different resolution levels. A standard star detecting software Daophot II quantifies the increment in the number of detected stars from raw images to the images processed by our proposed method as: for red filter 397–903, for green filter 663–945, for blue filter 362–896. On the contrary, Daophot II can’t detect any star in the highly noise-polluted images processed by the conventional methods. Therefore, we hope our proposed processing methodology will motivate others to initiate small telescope observations from any site restrained by its geographical location.

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Acknowledgements

The authors would like to thank Anjasha Gangopadhyay, faculty at Hiroshima Astrophysical Science Center, Hiroshima University, Japan, for valuable discussions and technical assistance for detecting stars using Daophot II. Special thanks to Subhash Bose, faculty at Department of Astronomy, The Ohio State University for insightful discussions on Johnson–Cousins BV R Filter System and isochrone fitting.

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Authors and Affiliations

  1. Department of Physics, Indian Institute of Technology Kharagpur, Kharagpur, India

    S. Chakraborty & T. Mondal

  2. Department of Physics, St. Xavier’s College (Autonomous), Kolkata, India

    A. Debnath & S. Roychowdhury

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  1. S. Chakraborty
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  2. T. Mondal
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  3. A. Debnath
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  4. S. Roychowdhury
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Corresponding author

Correspondence to S. Chakraborty.

Appendix A. Histogram plots showing gain in star count

Appendix A. Histogram plots showing gain in star count

See Figure 19.

Figure 19
figure 19

Two histograms depicting star counts for the HNSTD processed data and raw data as detected using Daophot II. \(V_J\) is Johnson V magnitude. The violet region represents overlap of data.

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Chakraborty, S., Mondal, T., Debnath, A. et al. A multiresolution approach to enhance small telescope data under non-ideal conditions. J Astrophys Astron 43, 22 (2022). https://doi.org/10.1007/s12036-022-09807-w

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