Spectroscopy & Spectrography

Spectroscopy with CCDSPEC 27/4/2019 Vega and Deneb and failed attempt to get M57

Using CCDSPEC spectrometer with Equinox Pro 80mm hand guided on Manfrotto mount.

Calibration pictures – Compact Fluorescent Bulb:

I use the following picture which I prepared using data from Wikipediato help with calibration using CFL bulbs.

Vega – I took spectra of Vega at two points tonight:

Deneb:

Failed attempt to obtain spectra of M57 Ring Nebula (As you can see lines do not line up especially 5800A hydrogen line which is very bright in the nebula = I think what I thought was M57 was in fact another star – I need to get a flip mirror to help finding faint objects for CCDSPEC.

New illuminated eyepiece for CCDSPEC Spectrometer

I am quite excited about this new Meade Illuminated 9mm eyepiece – it has adjustment screws which can Chang ether XY position of the cross hairs and allow me to align the cross hairless exactly over the spectrometer slit on my CCDSPEC spectrometer overcoming a problem I have using it at Night – the fact that i can’t see where the slit is in the dark!! Up until now I have relied on the fact that a star separates into a small spectrum when it reaches the slit but this can be hit and miss at Night.

I have tried 12.5mm illuminated eyepiece without adjustment screws (also shown below for comparison) – that is OK but the cross hairs are not quite on the slit so still can be difficult in practice getting single star in correct position.

Can’t wait to try this out under the stars….

Andy

CCDSPEC with new Meade 9mm illuminated eyepiece in position:

Photos with Samsung S7 phone through illuminated eyepiece showing slit and cross hairs of eyepiece with and without being adjusted so they are in correct position:

Photo of 12.5mm illuminated eyepiece for comparison:

Spectra of Moon, Vega and Jupiter taken with CCDSPEC on Sky Watcher Equinox Pro 80mm scope with Rob Leonard 11-12/5/2019

Rob kindly invited me around for an evening of observing. The Moon was half full and high and the humidity level high with mosture all over our telescopes but we still had a whale of a time – quite apt description as Rob found the Whale Galaxy for an amaxing view in his 14 inch Orion US scope – all star hopping – well done to him!!

I took some spectra of the Moon, Vega and Jupiter, using my CCDSPEC spectroscope on my Equinox – I know manual alt-az mount is not ideal but it is transportable so I used my Manfrotto mount tonight manually guided and star-hopping to targets – limiting me to bright targets. I would still like to take spectra of the Ring Nebula but I can’t see it in the CCDSPEC so I do need my EQ6 or HEQ5 mounts up and running to have a chance with that….

Particularly exciting tonight was our spectra of Jupiter, showing methane absorption lines – Jupiter’s spectrum is essentially that of reflected sunlight but its atmosphere does absorb light in the methane bands.

Rob and I were able to identify two of these bands in our spectrum this evening of the planet.

Andy

In spectra below my spectrum from tonight is in red and reference spectrum is in blue.

Moon – essentially this is a solar spectrum from reflected light:

Vega – Balmer series lines very obvious:

Jupiter – showing two methane absorption lines – one of main features that are different between Jupiter’s spectrum and the solar spectrum (In spectra below my spectrum from tonight is in red and reference spectrum is in blue).

Spectroscopy of Moon, Capella and Sirius 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. I love this photo – which can only be done with the Star Analyser – on the CCDSPEC you don’t see the Moon in the same shot!

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.

Spectrum of Sirius:

Nick took a spectrum of Sirius using his Canon DSLR/Star Analyser/Canon kit lens:

Some lines are visible in centre of graph (dips) – to determine what these are we would need to calibrate the graph. Turned out calibrating the Star Analyser spectra requires a bit more work on the light used – my CCDSPEC slit easily uses just about any light with clear identifiable lines but we need to point or at least narrow light source for the Star Analyser which we did not have available tonight……a job for Nick to make himself one!

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:

Notes on DADOS Calibration Lamp from Baader Planetarium Website

The following explains why the light kept switching on and off when Lee and I changed the plug at RAG mid-monthly meeting last Friday!

It also explains the black ring under the lamp – this appears to be so that it can fit over 2 inch end of a spectrograph – will it do same on my CCDSPEC?

Andy

 

Notes on DADOS Calibration lamp

The Neon calibration lamp only shines in the dark due to a twilight switch. So incidence of extraneous light while taking spectra of this Neon lamp is avoided. Please fix the Neon lamp with its adapter directly at the 2 inch entrance of the DADOS spectrograph to focus DADOS and to take reference spectra. The brightness of this Neon lamp is adequate in this configuration.

However, the lamp is too faint to be used in front of a telescope. The visually perceived color “Neon red” is a quite unique color between dark-orange and light-red due to the spectral distribution of the emission lines.

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