Comet Hill near the North Celestial Pole in 2011

Comet 2010 G2(Hill) was visible l0n 1st May 2011 although it was quite faint. It was predicted at magnitude 13.9. The first image taken is below. In this image the comet is in front of a star which is given a magnitude of 15.43 in the USNO Catalogue. It is difficult to distinguish from the star itself in this 30 second image using the C14. 

The comet is much easier to spot in the second image, taken 50 minutes later.  

 

Comet Garradd Animation from 2012

All my images of Garradd from 10th March 2012 were combined into an animation. Garradd was on the border of Draco and Ursa Minor.

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.

THE END

Spectroscopy Part 3 - Vega Spectrum Calibration

Continued from Part 2

I am working on my previous 135mm lens Vega spectrum today using RSpec and first show the Vega image adjacent to the generated raw profile.

To calibrate the spectrum I need two reference points. The first one is easy. The star image has passed directly through the grating without deflection and so zero Angstroms corresponds to the pixel position of the star as shown below.

The second reference relates to the Balmer Series Hydrogen Beta line which is clearly visible in the raw spectrum and corresponds to a wavelength of 486.1 nm or 4861 Angstroms. I entered this value which corresponds to the pixel position of 2722 pixels on the Canon chip.

This is how I calculated the Hydrogen Beta line wavelength for the above calibration value - as shown in the extract from my spreadsheet below.

 The Balmer series of lines are all caused by an electron transition between orbit 2 and higher orbits. For the Beta line it is between orbits 2 and 4.

Once the x-axis changes to Angstroms, the number of Angstroms per pixel is shown - in this case it is 4.3 A/pixel. Now that is known,  in future I will only need to set the zero point to produce a calibrated profile on any star using the 135mm and grating with the same camera.

 

I will continue with this in Part 4.

Spectroscopy Part 2 - Spectrum of Vega

Continued from Part 1

I managed to acquire a spectrum of Vega so that I could measure the Angstroms per pixel  for the 135mm lens and grating combination. This is a type A star that I need as explained yesterday.

But first of all here is the Capella spectrum from Part 1 shown as an uncalibrated profile.

The Canon 40D has 3,888 x 2,592 pixels. The longer axis of the CMOS chip corresponds to the x axis with the horizontal spectra. What I need to be able to do is to calibrate the x axis so that it displays in Angstroms i.e. wavelength units rather than pixels.

Here is the uncalibrated profile for the star Epsilon Aurigae shown in the same manner as above

Back to Vega now - here is a 15 second image of Vega

 Continued in Part 3

Spectroscopy Part 1 - Spectroscopy with a DSLR and SA100 Grating

I have an SA100 grating on loan from Bolton Astronomical Society that I decided to put into action with my Canon 40D DSLR. Although I had used this grating previously with a CCD camera I had not tried the DSLR. The advantage of using a DSLR is that it can give boost to the resolution of the grating by positioning it in front of the camera lens as opposed to using it beween a CCD camera and telescope. I cut a rough hole in the lens cap for my 135mm manual lens (that I used to use with a Zenith B film camera in the old days) and screwed the grating and spacer into it. A firm fit.

I used the APT software to get Capella into the field of view.  What you need to do is get the star on the left hand side of the screen to allow space for the first order spectrum on the right of that. It is best to get the spectrum horizontal although you can rotate it to the horizontal later but that may introduce artifacts. I then added the lens cap with the grating and eventually ended up with a horizontal coloured spectrum after a bit of trial and error rotating the lens cap.

This is a 30 second image. The spectra of Capella and Epsilon Aurigae are shown. Both of these can be analysed but the spectra of Eta and Zeta cannot because you need to be able to see the (zero order) star in each case as well to be able to calibrate the spectrum.

This was just a trial to see if I could produce spectra from the DSLR grating combination - this was my first attempt at this.In reality I need a less common Type A star as my first attempt at science with the DSLR and grating rather than Capella which is a type G star. This is because in order to determine the spectral resolution in Angstroms per pixel and to calibrate the profile X axis in Angstroms rather than pixels I need to have a star with clearly defined Hydrogen Balmer lines that I can guarantee are correct.

 Continued in Part 2

BL Camelopardalis Light Curve from Sunday's measurements

The resulting light curve from Sunday night's images of BL Cam over 3 hours is here

So what does this mean and where does it come from - the full process is shown below:

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Last year I plotted a light curve for this star that only covered one cycle. I wanted to extend this to a few cycles as this can be achieved in a single night. BL Cam is a Short Period Pulsator (SPP) and is an SX Phoenicis variable.

SX Phe variables are Population II stars and have low metal abundances. They are old stars which did not have metals from previous generations but formed from Hydrogen and Helium - thus the low metallicity.

The similar family of variable stars " Delta Scuti" stars are population 1 and are younger stars. 

The AAVSO site allows the name of a star to be entered and various searches to be carried out - I put in BL Cam and asked for a chart to be plotted.

 The resulting chart gives details of the star as well as indicating comparison stars that can be used.

The expected period is 0.0390976 days. Multplying this by 24 gives 0.93 hours which is about 56 minutes. I will compare the period that I measure with that value. Its magnitude range is given to vary between V 12.95 and V 13.25. I aim to take unfiltered images so my magnitude estimates will only be approximate.

 I took continuous 10 second images using my C14 and SBIG ST9XE camera for about 3 hours. Early in the process the laptop decided that it had to close down so I lost part of the light curve during the restart time. This is clearly reflected in the resulting light curve.

I ended up with over 700 images - far too many so I reduced this to 70 by using only every tenth image.

  I had taken 20 flat, 20 dark and 20 bias frames so I used CCDSoft to reduce the 70 images with those frames.

I used CCDSoft again to align the reduced frames and uploaded these images into VPhot.

This is the list of uploaded images (part). Note that the images from the two Australian telescopes of the supernova in Tucana have arrived - I will look at these when I have dealt with BL Cam.

I used image 73 to produce a sequence of comparison star and check star.

This is the image showing this.

 Star 114 is the comparison star and Star 120 the check star.

 The photometric solution for this image is shown

So at the time this image was taken the magnitude of BL Cam was approximately 13.17.

The check star with a nominal magnitude of 12 was mearured at 11.97. Whatmatters is that this value should be consistent for each of the images taken - we will see that later!

I had saved the sequence as BLCamsecondB which can now be applied  now applied to each image to generate the light curve.

Three complete cycles have been completed. A period of 0.041 days is indicated which is about 56 minutes .

 The range of magnitude variation is from 12.92 to 13.25 which corresponds exactly with the predicted values.

Strong winds in Cabrera

It is difficult to sleep well when you have two telescopes on a platform up a mountain and a gale outside is threatening to blow both scopes away. It is 5.40 a.m. and checking the scopes half an hour ago I realised that the scope cover had been expertly removed from the smaller (CGEM) scope by the wind with snapped elastic cords lying around. I removed the OTA/camera assembly and brought it inside - replacing the cover over the tripod and power supplies which are in plastic boxes held down by heavy rocks. The tripods of both scopes are strapped down. The big scope is literally fastened to the mountain rocks with heavy strapping. The smaller tripod is strapped to the two heavy cannons that are the real reason for having the platform in the first place. Tomorrow a trip down to Turre to buy more elastic cords! Oh and probably a lot of sleep!

Turning out to be quite a day - blazing stars in the Pleiades Cluster now a cluster of Vultures

I have more data than I can cope with - I took about 700  X 10 second images of  the variable star BL Cam last night and I need to process those - images of Supernova ASASSN14jg have arrived from two telescopes at Siding Spring and when I went out on my walk I came across a spiralling group of these:

No - that's not the group - this is the group

I counted over 50 Griffon Vultures over Cabrera - with typical wing spans of about 7 ft!

I was trying to get nearer by climbing up the hill but they were drifting away - I wish I had spotted them earlier. By the time I got to a really good vantage point ,struggling for breath I should say, they had gone - probably in Africa by now - it is just across the Med. However I managed to get over 70 photographs of them - hoping that some of them would be in focus - manually focusing at a distance is difficult and autofocus does not work for me for birds at a distance.

A few more images.

 

  

I looked back at the house when i got up the hill.

and I am came across this

and then this

A Monday morning blazing with stars

One of those mornings - 5.55 a.m. and the sky is blazing with stars, No sign of the Moon that ruined last night's sky - unless you are a lunar astronomer of course! Orion dominates all with Sirius seeming unusually high in the sky -  the brightest of them all until I spotted Jupiter - it can't really be that Lepus just below Orion bright. Unusual stars below Orion - unusual in that they are usually lost in the murk of low altitude or below the horizon from the UK. Canis Major , Lupus and unfamiliar  Puppis and Columba It went through my head with Orion almost vertical - just West of South - that tent shaped Auriga was also the "right" way up. Constellation of GeminiGemini was recognisable because of Castor and Pollux overhead. Delphinus was clearly visible towards the south east but very high - to the North West Cassiopaeia was a W standing on its side. Gemini, Perseus and Taurus were there with the Pleiades very clear. I was only outside for 5 minutes - it was quite chilly but after a couple of minutes the light pollution that has increased gradually over the years became more evident - mainly in rows of concentrated bright street lights that seemed pointless at this early hour with not a car headlight - and I suspect no pedestrians - in sight. Cabrera was almost in total darkness with none of the low wattage walkway lamps switched on - the nearest things to street light in Cabrera. I knew Camelopardalis was there somewhere but not an easily recognisable constellation to spot.

Camelopardalis