Difference: LogBookAstronomyEntry0052 (3 vs. 4)

Revision 428 Oct 2014 - SimonWoeginger

Line: 1 to 1
 
META TOPICPARENT name="LogBookAstronomy"

Log Book Entry No.52

Days, Calendar Created: 27 Oct 2014 19:23:05 Days, Calendar Last Revised: 28 Oct 2014 21:41:59 Person SimonWoeginger Text MSc Observation_LN_SW
Line: 16 to 16
  Conditions: Mostly clear, a little muggy. No cloud coverage.
Changed:
<
<		Begun observation session with a run down of the procedure to prepare the dome (i.e. opening the shutter, rotating the dome).
>
>		Begun observation session with a run down of the procedure to prepare the dome.

Dome Procedure:

  • Enter dome

  • Close the hatch to prevent heat rising and entering the dome. The floors beneath are heated which causes a ‘chimney’ like effect if the hatch is left open as the hot air from below will rise up through it. Ideally the scope and dome should remain cool so noise due to thermal fluctuations is kept to a minimum.
  • In the Maxim DL suiteconnect to the telescope. This allows control of the camera for example you can set exposure times and capture images from the program.
  • Enable the CCD cooler in Maxim. This should be done ~1 hour before taking exposures. If you take observations too soon after enabling the cooler you get a ring like effect on your observations around the outer area of the frame. The ring progresses further to the sides of the frame as the CCD cools until it eventually disappears.The set-point of the cooler is set to -10 degrees celcius and the CCD itself fluctuated around this point slightly once the cooler had taken full effect.
  • Untie the ropes that control the shutter of the dome. Pull on ropes to open the shutter of dome, if the shutters do not open with ease, there is a long stick with a metal prod at one end which can be used to manually push the shutters open from near the top of the dome.
  • Once shutter is open, tie the ropes off again to make sure that they are kept out the way of the moving parts of the done which can rotate bothe counter and clock-wise
  • Using the door on side of dome, go outside and do some preliminary naked eye observations to find an interesting object to observe (this is important for aligning the telescope as detailed later on). This allows you to plan roughly where the telescope and open shutter should be pointing to allow unrestricted viewing.
  • Using the dome control unit, align the dome opening with what you want to observe.
  • When finished observing, realign both the dome and telescope to their origional position. Close the dome shutters and tie up the ropes.
To begin making observations you need to align the telescope to a bright object in the sky and then enable tracking. Tracking corrects the position of the telescope relative to the sedereal motion of the stars. This is necessary because the field of view of the telescope is so narrow if it was left stationary, the object you are observing will move out of frame. To align the telescope, the first step is to identify a bright object visible to the naked eye in the nights sky. You can acess the roof from the dome via. the door on the side. Once on the roof you are able to evaluate potential targets. We identified the star Vega (25ly away, 2.1M0, alpha lyrae - the brightest star in the lyra constellation and 5th brighest in the night's sky). The star charts provided in the program stellarium coupled with manual positional measurements allow you to identify the star you are looking at with the naked eye.
 
Changed:
<
<		Identified a bright object in the night sky with the naked eye to set as our target for observation. Aligned the open dome shutter and telescope with said object. This was done crudely first by eye, then using the viewfinder and finally centred with the help of continuous exposures in the Maxim suite. By setting the camera mode to continuous and applying a short exposure time, you are able to produce images of what the telescope is looking at in relatively rapid sucession allowing for an almost real time feed of what the telescope is aligned with. This makes centering and aligning the telescope easier.
>
>		Once a object in the sky has been chosen, the next step is to align the telescope to enable the activation of tracking.
 
Changed:
<
<		Went through the alignment and tracking procedure on the telescope to account for the rotation of earth.
>
>
  • Telescope Alignment:

    • Use a high speed on the control paddle (speed button -> 9 is fastest, 1 is slowest on number pad) to crudely align the scope with what you want to observe using the arrow buttons. This can be done roughly by eye by lining up the two bolts on the side of the telescope with what you are looking for.

    • Then use the viewfinder which has a set of crosshairs to align the scope more accurately with the object in the sky. A medium speed setting on the paddle can be used to move the scope with a greater deal of precision.
    • Once the crosshairs are centred on the object you wish to view, take an exposure in the maxim DL suite. Once the image has been taken and downloaded you can adjust the scope to get the object centred in the frame. If you set maxim DL to take continuous ~1s exposures you can get a better sense of the best way to align scope and object.
    • Once the scope is aligned, enable GPS lock. This continuously corrects the scope to account for the rotation of the earth. The field of view of the scope is very narrow causing the object you are observing to move through the frame if the scope remains stationary.
    • Once tracking is enabled, the scope should keep the object you are trying to view in frame automatically.
    • Using the control paddle, tell the telescope which star/object it is currently aligned to
    • With the telescope connected to stellarium which now allows you to control the scope through the program itself. Using the star charts, you can align the scope to stars/objects shown in stelarrium. (Wait for the ‘beep’ if you move the scope in the program. The scope moves quickly at first but then makes finer corrections to ensure the scope is aligned well. The 'beep' occurs once the telescope is properly aligned, it can take some time ~20-30 secs).
    • While repositioning the telescope it is important to be aware of it's orientation with respect to it's base. The telescope is capable of flipping over on itself which can cause the CCD attatchment to collide with the stand. In a situation where this may happen, power down the telescope via the power controls located on its stand immediately.

With the telescope aligned you can control where it is looking via. the stellarium program. Multiple exposures of Vega were taken at different exposure lengths using the Maxim DL program.
 
Changed:
<
<		Once the scope was tracking the star, used positional data coupled with stellarium to identify it as the star Vega (alpha lyrae). Took multiple observations of Vega at different exposure lengths.
>
>		Using stellarium, the telescope was then trained on the open cluster M-39 in the constellation cyganus (800ly away from earth). Again took multiple exposures. The cluster is composed of a number of stars. Using the star chart in stellarrium the star patterns were compared to that shown in the exposure allowing for individual identification of the stars the cluster is made up of.
 
Changed:
<
<		Using stellarium, focused the telescope on the open cluster M-39 in the constellation cyganus. Again took multiple exposures and through comparison to the stellarium star chart, identified individual stars.
>
>		You have the ability to manually focus the telescope. If it is out of focus the exposures of stars can present as donuts (dark centres with bright outer ring) or they seem flat and blurred at it's edges. The procedue to manually focus the telescope is first to 'unlock' the mechanism. There are two dials, the shorter one can be rotated to unlock the device allowing the second longer dial to be turned focusing the telescope.
 
Changed:
<
<		Experimented with the manual focusing of the telescope. Noted that the earth's atmosphere above can act to take the image out of focus.
>
>		Last target of the night was the andromeda galaxy known as M-31 (as it is a messier object) and is 2.5x106 ly away from earth and the closest spiral galaxy to the milky way group. This galaxy has a mass ~ 1.5x10^12 M0. 10 exposures were taken one after the other with the intention of eventually using them to form 1 image with considerably less noise.
 
Changed:
<
<		Last target of the night was the andromeda galaxy (spiral galaxy also known as M31). Took 10 exposures one after the other with the intention of eventually using them to form 1 image with considerably less noise.
>
>		An interesting point to note is that movement of the atmosphere above the telescope can cause exposures to shift in and out of focus. This was made evident as during continuous exposures of M-39, the stars were alternating between being in focus and out of focus.

The exposures taken during the night of observation are attached to this post.

  Back to: LogBookAstronomy
View topic | History: r4 < r3 < r2 < r1 | More topic actions...
 
This site is powered by the TWiki collaboration platform Powered by PerlCopyright © 2008-2022 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding RHUL Physics Department TWiki? Send feedback