Attempting to calibrate RELCO Starter against 12V Compact Fluorescent Lamp in order to work out the wavelengths of the main lines on RELCO spectrum

Today, I have had a go at calibrating the homemade RELCO Starter bulb calibration lamp I made against 12V compact fluorescent lamp bulb in order to determine the wavelengths of the main lines on the CCDSPEC spectrum of the RELCO bulb.

Download calibration files from analysis by clicking on link below – calibration files RELCO vs CFL CCDSPEC no telescope 30/9/2018:

Spectrum RELCO Starter on CCDSPEC without telescope 300918

Also look at to find out what happened when I tried to compare the lines I identified below with the atlas of lines from – sadly they don’t seem to match!


RELCO Starter Bulb spectrum taken with CCDSPEC Spectrometer (below):

Spectrum of compact fluorescent light bulb taken with CCDSPEC (below):

Graphing both above spectra together:

Calibrating spectra of both RELCO and CFL using above two lines in RSPEC gives following calibrated spectra:

The following is my final labelled image showing main lines on RELCO starter bulb spectrum (below):

“Pacman nebula ” and clusters in Cassiopeia.

Swadlincote  29/9/18 Vixen 102 Vixen lvw 22mm and lvw 5.0 mm eps, Oiii filter.

Stunningly dark , just a quick session before the moon climbed up. 4″ aperture catches open clusters , giving good contrast and colour.

Revisited the great number of open clusters in Cassiopeia. A great range here , from wide huge sparse clusters to compact dusty ones. An amusing “Loch Ness Monster ” cluster , Cr 463 showed up rearing it’s head .

I was very surprised to catch nebulosity in NGC 281 ( IC 1590 ) with an Oiii filter. Closing into the central bright star , it resolves into the delicate triple of Burnham 1.

Psi Cassiopeiae (SAO 11751 ) showed as a delightful triple , with the paired companion. I measured h2028 with the astrometric eyepiece , getting 60″ , pretty good ! Clear skies ! Old Nick.


Spectroscopy of Arcturus – re-analysis of spectrum from 4/8/2018 on 26/9/2018

Hi All

The following images are of my analysis of a spectrum of Arcturus I took using my CCDSPEC spectrometer. On this occasion, I used my Sky Watcher Equinox Pro 120mm OTA on EQ6 Pro (although I was hand guiding it rather than using the drives). The camera is a QHY6 and the acquisition software was EZCAP which comes with the camera. I took the spectrum in Lichfield, Staffordshire, UK on 4/8/2018 and analysed it 26/9/2018 using RSPEC software.

Attached are:

  1. Uncalibrated spectrum line graph (x-projection).
  2. Calibrated spectrum of Arcturus – I used an amateur spectrum on the internet to provide three data points for the RSPEC Calibration Wizard (linear approximation).
  3. A plot of my calibrated spectrum against the closest reference spectrum I could find in RSPEC. Arcturus is spectral type K1.5IIIFe-0.5 but closest match I could find on RSPEC was K1iv, so I have plotted against that. In spite of the slight differences, I have been able to identify almost exact matches for range of lines between the two spectra – it amazes me how amateurs can obtain incredibly precise data using spectroscopes on their very modest backyard setups!
  4. From this I have generated a calibration graph for my own future use which I have also posted here – if you have a better/alternative one you have created please do upload it in response to my post here.


Comparison of spectra of 12V Compact Fluorescent Light Bulbs

The 12V Compact Fluorescent Light Bulbs I have purchased come in two flavours – 2700K and 6400K (later is daylight). Tonight, I took spectra of both types using my CCDSPEC spectrometer to determine whether the peaks shown on the spectra were the same. It turns out that they are and hence can be readily used for calibration purposes on my spectrometers. The main difference between the two is the intensity of the peaks with the 2700K light bulb having much lower intensities than the 6400K light bulbs.

Information on different colour temperatures of compact fluorescent bulbs can be found at


2700K spectrum:

6400K spectrum: