CCDSPEC Spectrometer and PCSpectra software

Spectroscopy of Moon and Capella in Lichfield 18-19/2/2019 – Andrew Thornett & Nick Rufo – CCDSPEC slit-based spectroscope and Star Analyser spectroscopy grating

Last night was predicted to be clear all night. The Moon was bright, so it seemed to be a good opportunity to do something other than observing. Nick and I are both interested in spectroscopy so he bought around his Star Analyser on his camera and I took outside my Sky Watcher 120mm Equinox on EQ6 mount with CCDSPEC spectroscope. Of course, it did not turn out to be clear all night but nevertheless Nick and I were able to do some good work & enjoy ourselves……apart from when I dropped his camera lens on the floor – Andy strikes again – ahhh!

The Star Analyser has advantage of being quick to set up whereas the Equinox/EQ6/CCDSPEC was lot of faff to set up – Nick was photographing spectra well before me!

Successful procedure for aligning EQ6 mount/Sky Watcher Equinox 120mm telescope/CCDSPEC & taking spectra:

In fact, last night was a very positive experience for me because I got the procedure of taking spectra with tracking mount working properly for first time – hitherto my spectra have been on undriven Manfrotto mount with Sky Watcher Equinox 80mm.

Process that worked last night was:

  1. Balance EQ6 using heaviest eyepiece I have – 20mm Explore Scientific 100 degree eyepiece in 2″ diagonal – last night I also had finder scope for 120mm on scope and also Ed Mann’s wonderful powered and heated laser finder. I used 2 counterweights on the EQ6. Do NOT pull dew shield out during balance process.
  2. Perform 3 star alignment using the eyepiece. This is NOT easy to do with CCDSPEC eyepiece so use the heavy Explore Scientific 20mm eyepiece for the 3 star alignment. Need finder and laser to help with alignment.
  3. Exchange eyepiece for CCDSPEC. In CCDSPEC use illuminated reticule eyepiece – this has cross hairs that enclose the slit at centre helping to get stars on slit. Focus CCDSPEC using its eyepiece so star or Moon even better focused on slit – this involves racking focuser right out – hence why balance an issue as moment on the balance point of mount is changed – so need to use heavy eyepiece initially. Pulling dew shield out at this point helps with balance of scope as eyepiece exchanged for CCDSPEC.
  4. Slew to object of interest. Laser pointer and finder help if 3 star alignment not perfect.
  5. Use illuminated eyepiece to slew object onto slit as likely to be slightly off in field of view.
  6. Once object hits slit it will spread out from point light source into tiny spectrum.
  7. Take photo of spectrum using QHY6 camera on CCDSPEC and Nebulosity software – choose ASCOM camera in camera choice drop down list and then QHY6 camera in drop down menu that follows in Nebulosity from choosing ASCOM camera.
  8. Analyse spectrum in RSPEC.

Spectrum of the Moon:

The following is a photo of spectrum on Star Analyser showing the Moon to the left and its spectrum to the right taken by Nick with his Canon camera on undriven mount with Star Analyser grating.

In the following image, I have graphed the spectrum taken with CCDSPEC of the Moon last night against a reference solar spectrum (CCDSPEC pointed at cloudy sky in day) taken by myself 1/8/2018 (below). The spectrum of the Moon as taken by the QHY6 camera is shown on the left and a graph of this in RSPEC on the right, together with the reference solar spectrum. It shows that the lines on the spectrum from the Moon match those on the spectrum from the Sun – this is because the spectrum from the Moon is in fact the spectrum of reflected sunlight bouncing off the Moon which does little to alter it as it has no significant atmosphere.

Spectrum of Capella:

I was really pleased when I could slew the EQ6 to Capella and within two attempts get spectrum of this star. The laser pointer REALLY helped to compensate for problems in my poor 3-star alignment.

In the screenshot from RSPEC below, Capella’s spectrum is on the left as it comes out of the QHY6 and on the right this spectrum is graphed against the same solar spectrum as above. Some but not all of the lines match, showing that the two stars differ in composition.

Calibrating the spectra:

I have not got around to doing this yet – but this process involves identifying lines with known wavelengths so that the pixel measurements above can be replaced with wavelengths.

To this end, I took a spectrum last night of a 12V Compact Fluorescent bulb using same set-up as above. For some reason the graph is the wrong way around and needs to be inverted left-right but I seem to be having difficulties getting RSPEC to do this on the data set for this spectrum, hence why I have not yet calibrated the above spectra!

I will be able to identify the lines using this graph below:

CCDSPEC Spectrometer/QHYCCD 6 camera – effect of turning on the fan

When I last used my CCDSPEC spectrometer with its QHYCCD6 camera, I was concerned about the number of apparent hot pixels appearing on the image. OK – it did not matter as the nature of the spectrum meant a few hot pixels were neither here nor there but still I wanted my new kit to work properly!

….Then I noticed that I had not been turning on the fan – so tonight I took pictures of the night sky (without telescope) using Nebulosity – with and without fan turned on the QHYCCD6 camera. The effect of cooling by this method is dramatic for these 30 second exposures as you can see below.

NB The spectrum of the night sky is just visible in the middle of each picture (30 second images).

All images from tonight’s session, including FITS files can be downloaded here:

QHY6 camera on CCDSPEC spectrometer – spectrum images of LRO night sky (30s exposure) without telescope – taken on 13/01/2019

Andy

With fan TURNED OFF:

With fan turned ON – only a couple of hot pixels remain:

Dark frame of fan turned ON:

Using the “subtract background” function in RSPEC Software to bring the baseline down towards zero on Altair spectrum from 10/10/2018

Following my recent post:

Attempt to generate instrument response curve in RSPEC software for CCDSPEC using Altair spectrum from 10/10/2018

Peter Hill asked me whether I had used the “subtract background” option in RSPEC to bring the baseline down towards zero on the spectrum – I had not done it and did not know what to do so I looked it up and here is the difference it makes……(below)

A dramatic improvement! Thanks Pete for the advice!

Andy

WITHOUT the “subtract background” feature being used (below):

WITH the “subtract background” feature being used (below):

Attempt to generate instrument response curve in RSPEC software for CCDSPEC using Altair spectrum from 10/10/2018

This post follows on from this previous one:

Spectroscopy of Altair (and Vega) in Lichfield, UK 11/10/2018, using CCDSPEC, Sky Watcher Equinox Pro 80mm OTA on Manfrotto manual mount

Today (11/10/2018), I had a go at generating an instrument response curve in RSPEC software for CCDSPEC using Altair spectrum from 10/10/2018.

Andy

My Altair Spectrum from 10/10/2018 (LRO, CCDSPEC, Sky Watcher Equinox Pro 80mm):

Dividing Altair spectrum by smoothed A7V reference spectrum leads to instrument response curve below:

Applying instrument response curve above to Vega spectrum in RSPEC:

See following post for a follow up to this post 11/10/2018:

Using the “subtract background” function in RSPEC Software to bring the baseline down towards zero on Altair spectrum from 10/10/2018

Spectroscopy of Altair (and Vega) in Lichfield, UK 11/10/2018, using CCDSPEC, Sky Watcher Equinox Pro 80mm OTA on Manfrotto manual mount

A new star tonight for me – Altair! I have not taken a spectrum of this star before. Being also an A type star (A7V), it was going to be similar to Vega (A0V). Therefore, I took a spectrum of Vega for comparison too..

Taken using CCDSPEC spectrometer with Sky Watcher Equinox Pro 800mm Telescope on alt-az undriven Manfrotto mount – hand-guided for 50 second exposures.

RSPEC software has some great reference spectra which I was able to use to calibrate these images this evening. Cross checked using my own image of Vega as reference spectrum.

Note Vega = A0V spectral type

Altair = A7V spectral type

Andy

The post below follows on from the above post:

Attempt to generate instrument response curve in RSPEC software for CCDSPEC using Altair spectrum from 10/10/2018

 

RELCO Starter Spectrum from CCDSPEC at LRO graphed against Three Hills Observatory ALPY data and with lines identified including those used by ISIS for calibration

On the RELCO starter spectrum below, my CCDSPEC spectrum is graphed against the ALPY spectrum from Three HIlls Observatory from Robin above, and I have marked the lines I identified together with those lines that ISIS use for calibration – this gives some more lines for me to use at LRO.

Comment from Robin at Three Hills Observatory (https://stargazerslounge.com/topic/226911-neon-lamp-to-set-spectroscope/), “Your spectrograph has roughly the same resolution as the ALPY (R~500) and these lines are known to be reliable and give a very accurate calibration to better than 1A with the ALPY.  I have attached a list of wavelengths of the 13 lines. They correspond to lines identified in the spectrum by Richard Walker using his DADOS with 200l/mm grating (R 900).  If you identify as many of the lines in your spectrum as possible and make a 3rd order fit,  any wrongly identified lines will immediately stand out as they will have larger errors.”

Lines used by ISIS to calibrate ALPY

  • 3946.1A
  • 4158.59A
  • 4510.73A
  • 4545.05A
  • 4657.9A
  • 4764.87A
  • 4965.08A
  • 5400.56A
  • 5852.49A
  • 6266.49A
  • 6506.53A
  • 7147.04A
  • 7383.98A

Andy

Identifying lines on my CCDSPEC RELCO Starter Spectrum using Atlas of Emission Lines

Here is my go at identifying emission lines on y RELCO Spectrum using the Atlas of Emission Lines 200 lines/mm spectrum.

Andy

My RELCO with my attempt at identifying lines:

I used the following spectrum from http://www.ursusmajor.ch/downloads/sques-relco-sc480-calibration-lines-5.0.pdf from which to identify above lines:

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 https://stargazerslounge.com/topic/226911-neon-lamp-to-set-spectroscope/?tab=comments#comment-3521335 to find out what happened when I tried to compare the lines I identified below with the atlas of lines from http://www.ursusmajor.ch/downloads/sques-relco-sc480-calibration-lines-5.0.pdf – sadly they don’t seem to match!

Andy

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):

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.

Andy