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:


Inspired by Neil’s image of IC1333, I had a  go myself.

I did my best with the conditions but

I was hampered by a number of things.

  1. The moon was only 15 degrees off the target and 75% full
  2. Only a small amount of data collected. Red 9 x 5 minutes, Green 9 x 5mins, Blue 7 x 5mins.
  3. The camera decided not to function in the cooling mode so all images at ambient temperature  (hence noisy),
  4. Me!

Observing Log 17/2/19

Observing Log 17/2/2019 @ 19:00-22:30.

Andrew Thornett



·       Orion 10 Dobsonian Telescope

·       Celestron NexYZ camera/telescope adapter

·       Explore Scientific 14mm eyepiece

·       Ethos 6mm eyepiece

·       Tele Vue Radian 12mm eyepiece

·       Tele Vue Nagler 7mm eyepiece

·       Samsung S7 phone

·       Tele Vue Paracorr coma corrector.

·       Tele Vue 2x Big Barlow


The great thing about ten-inch dob is it is easy to move around garden so I can avoid trees ton see different objects.

Today I have been sorting out my shed and thrown away a load of stuff to create space – mainly old radio gear (homemade antennae, old satellite dish, poles from trampolines, and the ilk) and it is amazing how much space I have created!

However, my back aches especially as I have also been swimming. Nevertheless, I must take the chances to observe, don’t I? In the UK, the sky does not clear on demand!

Tonight, I have also tried out my new USA Orion two-inch filter slide on the UK Orion 14-inch Dobsonian telescope. Unfortunately, I found that I could not get enough in-focus alone with the ES eyepieces but there was plenty of in-focus with the Tele Vue Big Barlow added in as well. However, that resulted in the 20mm ES effectively becoming a 10mm eyepiece, removing my finder eyepiece. I do have a 40mm eyepiece in the box and a 35mm one in another box, so I think those two need to be bought into action. The Paracorr gives a 15% Barlow effect but that did not give enough back focus for the filter slide.

Moon, Current Location 52º 41′ N 001º 49′ W,52.68523374, -1.810645505, Bright nearly full.

Excellent chance to try out new phone adapter. Better than hand-holding!

But would not fit around large ES and Ethos eyepieces so needed to change to Radian and Nagler eyepieces – I need to look at this in daylight to see if can open the jaws further and overcome the inward slope at the top of the bigger eyepieces which makes it difficult for the adapter to grip.

Still, I got some fine photos of the moon.

Orion Nebula, M 42, NGC 1976, LBN 974, Current Location 52º 41′ N 001º 49′ W,52.68523374, -1.810645505, Nice view although smaller as moon close by and wiped out some of fainter nebulosity. Unable to get photo with adapter as having to use eyepieces with too high a magnification so difficult to keep objects in view long enough to have time to centralise phone to centralise on Celestron NexYZ adapter. The adapter was too sloppy, and I need to look at it in the daylight to find out how to tighten it.

Owl Nebula, M 97, NGC 3587, ARO 25, PK 148+57.1, PN G148.4+57.0, VV 59, Current Location 52º 41′ N 001º 49′ W,52.68523374, -1.810645505, Despite a very bright moon which wiped out any view of the M108 galaxy, I was able to get a definite view of the Owl Nebula nearby to it. Boy was it faint with this bright moon nearby. I needed to use averted vision, nudging the eyepiece (where I touch the eyepiece to make it vibrate and this makes it easier to observe faint objects as they move in the field of view) and OIII filter to see it but see it I did – quite large once I found it.

Orion Nebula, M 42, NGC 1976, LBN 974, Current Location 52º 41′ N 001º 49′ W,52.68523374, -1.810645505, Back to M42 this time with OIII and UHC filters and 14mm ES. The difference between no filter and OIII is profound with much more nebulosity evident in the OIII than without a filter. I think the OIII does better than UHC filter bringing out more of wings of nebula but both clearly excellent filters on this object.

NGC 1975, Current Location 52º 41′ N 001º 49′ W,52.68523374, -1.810645505, These reflection nebulae just above the fish mouth of M42 were visible tonight using my OIII filter and slightly visible with UHC filter although the difference between the views in the two filters was quite significant. Not visible without filter with this bright moonlight.

IC 1805 (bright central region of the Heart Nebula), Current Location 52º 41′ N 001º 49′ W,52.68523374, -1.810645505, I thought I would have a go tonight at seeing if I could observe the Heart Nebula despite the bright moonlight. I was trying to find the Double Cluster in Perseus as a starting point for a star hop to the Heart Nebula. I had left the UHC filter screwed on to the end of the 14mm ES eyepiece. To my surprise I came across a definite patch of nebulosity. Looking at Sky Safari, I realised that I had wondered off my line to the Double Cluster accidently hit the Heart Nebula (its central bit at least)! I was able to confirm the find from the sky location and star pattern in the area compared to what Sky Safari said I would find there. I never did find the Double Cluster tonight…. The reason I have used the designation of the central patch of the nebula for this find tonight is that this central patch is particularly bright and is what I found. There did appear to be other nebulous patches nearby but those were far less bright, and I did not take time to try and identify them.

Bode’s Nebulae, M 81, NGC 3031, UGC 5318, PGC 28630, MCG 12-10-10, CGCG 333-7, IRAS 09514+6918, 2MASS 09553318+6903549, Current Location 52º 41′ N 001º 49′ W, 52.68523374, -1.810645505, My last two observations are M81 and M82. Both seen with this bright moon about 90 degrees to southeast high in sky. M81 much more visible than M82, with its bright core & clearly oval rather than circular with fainter periphery compared to the core. UHC and OIII filters gave a much worse view of this galaxy than without any filter. Visible with these filters by direct vision but quite faint compared to unfiltered view.

Bode’s Nebulae, Cigar Galaxy, Ursa Major A, M 82, NGC 3034, UGC 5322, PGC 28655, MCG 12-10-11, CGCG 333-8, Arp 337, IRAS 09517+6954, Current Location 52º 41′ N 001º 49′ W, 52.68523374, -1.810645505, M82 was much fainter than M81 tonight. I don’t normally seem to notice such a difference when I am observing M81 & M82, but the moon seems to emphasise it. I think it is the bright core of M81 that really stands out. Although filters did not help with the view tonight of M81 and M82, changing the eyepiece from the 14mm ES to the 6mm Ethos really helped. In the books, it says that increasing magnification can help boost contrast and that certainly worked tonight on these two objects. In fact, I found M82 tonight using the higher magnification eyepiece having had difficulty with the 14mm. I found M81 relatively easily with the 14mm.

22:30 – Closed up for the evening.


Rosette NB1 filter

I thought id have a crack at the Rosette nebula to test out my new IDAS NB1 filter and I’m very pleased with the result. First thing you’ll will notice with the filter is that due to the higher cut off point and different wavelengths the histogram saturates pretty quickly under a near full moon. The large majority of this is Halpha but its very pleasing to obtain anything under a bright moon especially a part colour image. At this point id say its one of my best astro purchases!

51X2.5min under the moon