Orwell Astronomical Society (Ipswich)

Sketches Of The Sun,
04 June 2023 - 10 May 2024

This page shows sketches of the solar disk made with the following instruments:

• OASI's Coronada Hα PST (Personal Solar Telescope) and various eyepieces. The instrument is an introductory model, intended more for visual rather than photographic use. The image is relatively dim, around half the brightness of that produced by OASI's Lunt LS50, making it especially challenging to pick out detail.
• A Celestron C4R 102 mm F9.8 refractor on a manually driven alt-az mount. To provide safe views of the solar disk in white light, the telescope was fitted with a Lunt 1.25" Herschel Wedge (diagonal) and an additional single polarizing filter fitted to the eyepiece (in accordance with instructions from Lunt). The eyepiece/filter combination could be rotated to adjust image brightness to a comfortable level.

Sketches made at the eyepiece of the PST were produced using a pencil and/or crayons. Some of the resulting images were scanned and subsequently post-processed in Gimp v2.6.

Sketches made at the eyepiece of the C4R were post-processed as follows:

1. Scan image to PDF using an HP Envy 5646 printer/scanner.
2. Copy/paste image into Microsoft Paint.
3. Flip image L-R horizontally to correct the effect of the diagonal.
4. Add black oval/circle to mask the edge of the solar disk.
5. Save image then copy/paste into GIMP 2.6 (1024 pixel square).
6. Bucket-fill the sky background black. Touch up remaining spots around the solar disk (paintbrush tool).
7. Save final image.

10 May 2024, 16:15-16:45 UT

Below left is a pencil sketch made using the PST with a 20 mm Plossl eyepiece providing a magnification of 20x. After some trial and error to achieve optimum focus, I found cupping my hands around the eyepiece significantly improved contrast. Wearing a wide brimmed hat reduced the glare from the Sun, and an adjustable observing chair provided a comfortable posture! My technique was detune the PST to the white light range to sketch the sunspots: this helped to anchor the sketch. I then returned the PST to the Hα range to sketch active regions, prominences, and filaments.

The colossal sunspot group AR13664 (labelled below in shortened form as 3664) triggered an intense aurora on 10 May.

For comparison purposes, below right is an image taken on the same day by the Helioseismic and Magnetic Imager (HMI) aboard the Solar Dynamics Observatory (SDO).

06 December 2023, 11:45-11:50 and 08 December 2023, 10:55-11:00 UT

Sketches of the Sun in white light using the Celestron C4R with a Star 25 mm Plossl eyepiece providing a magnification of 40x. Comparison of the images shows the motion and evolution of active regions on the solar disk.

17 August 2023, 15:00-15:20 UT

Creation of a sketch of the Sun using the PST with a 20 mm Kellner eyepiece providing a magnification of 20x. The image features prominances, filaments and active regions. Left-right: orignal pencil sketch, scanned version with colour added, final version with marbling added to prove the most realistic representation of the view through the eyepiece.

26 June 2023, 08:55-9:00 UT

Sketched using the PST with a Meade 26 mm Super Plossl eyepiece providing a magnification of 15.4x. The image features prominances, filaments and active regions.

04 June 2023, 12:30-12:35 UT

Sketched using the PST with a Meade 26 mm Super Plossl eyepiece providing a magnification of 15.4x. The scanning process lost some detail but retained key features including prominances, plages, filaments and active regions. Clearly a lot was happening on the solar disk!

Neil Morley

Original: emails 18 June, 26 June, 19 December 2023; 16 May 2024.
Updated: 17 May 2024