Then and Now

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The York University Astronomical Observatory is a humble little dual-dome observatory housing a 60cm on one side, and a 40cm on the other. The staff and volunteers of the observatory run multiple projects including, public outreach and original research. When the observatory was built, it was at the north edge of York University campus, which itself was at the edge of North York. Much like the David Dunlop Observatory, at the time this really was not a bad of a place to observe from. The DDO is in the middle of Richmond Hill and was able to produce some very high impact research! As time moves on, light pollution has gotten worse and worse, and observatories like these are becoming less effective (in terms of research) each year. But light pollution isn’t the only problem, so is nearby construction. Here is the York Observatory as it stands today:

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York Observatory as it stood a few years ago:
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Then and Now. Things change! Ongoing construction on campus has slowly, but surely, cut off more and more of the observable sky. Over the last 6 years, a 4th floor was added to the Petrie Science and Engineering Building (which is the building to the right, and is attached to the observatory), and a new health science building was erected to the immediate north.

Mounting the Spectrograph

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The York University Astronomical Observatory has two telescopes under two domes. One of the scopes is 40cm in diameter the other is 60cm in diameter. Both of these use an SBIG ST-9 CCD camera for us to take pictures with. Currently, the 60cm is engaged in a variable star monitoring campaign, wherein we continually image a series of stars known to periodically change their brightness. We literally take a picture of the star every few minutes and measure the brightness of the star, and how it changes over a 10 hour time-scale. The act of taking the picture is called ‘photometry.’

The other side of the astronomy coin is ‘spectroscopy,’ where instead of taking an image of the sky, you first pass the light from an object (like a star) through a prism. Sir Isaac Newton figured out (and you may remember this from elementary school science class), that light is made up of smaller components. When you pass light through a prism, it breaks up into a rainbow. A spectrum of a star/galaxy/nebula can tell you a lot more about that object than its corresponding photometry. It can tell you what elements are present and tell you how much of them are there. Spectra are pivotal to modern day astrophysics!
The good news is, the York Observatory now has a Spectrograph!

This is the spectrograph, an SBIG instrument with a ST-7 CCD on the back, sitting on a desk, about to be mounted onto the 60cm telescope. 

Here is the spectrograph (on the left) attached to the back end of the 60cm telescope, with the ST-9 camera on the right. We use a box with a mirror in it to switch between the two instruments. 

 

Moving forward, we’ll see what we can do with this spectrograph, in terms of science. The first step is to understand what we’re looking at after taking a spectrum. Now that it’s on the back of the scope, we just have to wait for a clear night!

Notes on MDM

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Acquiring Targets, the Red Slit, the Guide Map

Acquiring a target on OSMOS was a bit of a learning curve.  The OSMOS 4x4k CCD can be used with two two different slits, a ‘centre’ slit and an ‘inner’ slit.  The inner slit is best used if you would like to concentrate on the redder end of the spectrum, and is thus dubbed the red slit.  The red slit is located just over 75% to the right edge of the CCD from the left side of the CCD.  When looking for targets, you first take an image without a slit/disperser in the light-beam.  The object will most likely be located very close to the centre of the CCD (as a result of focus and pointing maneuvers taken earlier in the night).  It is now your job to move the object into the portion of the CCD covered by the red slit.  This is done by:

1. Image the field and locate the object, while guiding using the guide camera

2. Put the red slit in the light beam and take another image; this results in a vertical bar on the CCD in the location of the CCD

3. Use the program oalign.py to calculate the separation between the centre of the object, and the centre of the slit:

oalign.py -l maskImage.fits fieldImage.fits *

this will calculate a number of steps (on the guide camera!!!) in the offset between object and slit.  In order to move the telescope to match the two up you must:

4. turn guiding off momentarily

5. enter into the guider GUI the number of steps to move the guider camera, enter (watch the stars on the guide camera jump out by the entered steps

6. move the telescope back  so the original guide star is back in the guide box, resume guiding

The object should now be in the slit.

NOTES: Important here is I was using the red slit.  The inner slit is quite far from the centre of the chip, and the guide camera can only move so far.  I found many times I was requiring the guide camera to make large movements that were TOO LARGE for its range of motion.  As a result, I would have to move the guide camera most of the way, and then begin guiding on a DIFFERENT star.  This would allow me to move the rest of the way.  Note also that there is a ‘red slit’ option on the guide camera GUI that forces you to use guide stars that are in the proper spot to account for such large changes.  I found that I could only switch to that option after making one small jump.

*this is considered a ‘back-up’ way of doing this.  There should be another way, that I was unable to get to work, that uses propsero scripts.

 

HgNe comp lamp

The Mercury-Neon (HgNe) needs only 5 sec of integration for a good comparison spectrum, however, the lamp needs to be on for at least 40 sec.  What happens is the Neon gas is first heated up, and that heated Neon gas is used to heat the Mercury gas.  This takes approximately 30 sec; it is safe to wait 40 sec in order to be sure that the Mercury gas has been heated up.  After the Mercury is heated up, the Neon gas is dialed down automatically leaving you with only a Mercury spectrum.