My Astronomy




My Telescopes

My Main Telescope - C14 and Paramount ME

My new Paramount MyT and 8-inch Ritchey-Chretien Telescope

MyT Hand Controller

My Meade 12 inch SCT on a CGEM (Classic) Mount

My 4 inch Meade Refractor with Sky Watcher Guidescope and ZWO camera on a CGEM (Classic) Mount

Skywatcher Star Adventurer Mount with Canon 40D


My Solar setup using a DSLR and Mylar Filter on my ETX90

DSLR attached to ETX90. LiveView image of 2015 partial eclipse on Canon 40D

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 I try to log my observing and related activities in a regular blog - sometimes there will be a delay but I usually catch up. An index of all my blogs is on the main menu at the top of the page with daily, weekly or monthly views. My Twitter feed is below. I am also interested in photograping wildlife when I can and there is a menu option above to look at some of my images. I try to keep the news feeds from relevant astronomical sources up to date and you will need to scroll down to find these.

The Celestron 14 is mounted on a Paramount ME that I have been using for about 10 years now - you can see that it is mounted on a tripod so is a portable set up. I still manage to transport it on my own and set it all up even though I have just turned 70! It will run for hours centering galaxies in the 12 minute field even when tripod mounted.


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Spectroscopy Part 4 - Balmer Line identification in Vega

Continued from Part 3

This shows the position of the Hydrogen Alpha, Beta and Gamma Balmer Lines on my Vega Raw Spectrum.

 Even though calibrated this is still a raw spectrum because it is the Vega Spectrum modified by the spectral response of the camera. To see the true Vega spectrum I need to compensate for that. I used the RSpec software to determine the instrument response and then divided the above spectrum by that. This is the final Vega profile showing the Alpha Beta and Gamma lines again.(Right to Left)



So what can I get from this - well what is it that I am looking at.

First of all the Balmer lines are caused by Hydrogen in the atmosphere of Vega absorbing  light at the particular line frequencies causing dips in the curve or black lines in the spectrum.

Secondly the shape of the continuous spectrum - the line graph - is defined by the temperature of the star. We are looking at part of a "black body Planck curve" that has a specific shape for a star at a particular temperature. In my spreadsheet I used the black body curve equation to generate the theoretical curve for Vega and matched it against the above observed Vega Spectrum

The plotted curve for Vega generated by my spreadsheet is shown below. The wavelength axis is in nanometres rather than Angstroms. The Vega (coloured) spectrum is shown at the bottom explaining why we are only seeing part of the Planck Curve.

The curve comes to a peak that indicates a temperature of 9162k. There is a simple formula connecting the wavelength of the peak of a Planck curve with stellar surface temperature.