jump to navigation

First Science from the 30″ Robo-scope! September 14, 2010

Posted by jcconwell in Astronomy, Observatory, telescopes.
Tags: , , , , , ,
add a comment

On September 5th,  you saw first light.  This week we’ll talk about the first science measurements. The main research carried out at ARI and EIU with the 32″ scope and the 24″ scope are the search and measurement of  Near Earth Objects (NEO).  Just finding these objects are not enough, you must also precisely measure the changes of the position (astrometry) as the asteroid moves. These measurements determine the orbit, and allows astronomers to trace the future path of any asteroid. Below is a typical set of stacked photos from a CCD camera. The streaks are stars, caused by the rotation of the Earth, and the dot in the center is the asteroid (not moving with the stars).

Now after you take several of these photos and use a computer program like Astrometrica to analyze the data, you file a report at the Minor Planet Center at Harvard, the world clearinghouse for this data. So the data what’s it look like….(The first data from the new scope)

CON R. Holmes, 7168 NCR 2750E, Ashmore, IL 61912 USA
CON [ari@astro-research.org]
OBS R. Holmes
MEA R. Holmes
TEL 0.76-m f/6.8 Cassegrain + CCD
ACK Batch 001
AC2 ari@astro-research.orgK10R82M  C2010 09 13.15907423 39 23.63 +00 19 10.0          18.3 V      H21
K10R82M  C2010 09 13.16194523 39 22.39 +00 18 07.2          17.9 V      H21
K10R82M  C2010 09 13.16486023 39 21.12 +00 17 03.6          18.0 V      H21
K10R82M  C2010 09 13.16792823 39 19.78 +00 15 56.8          18.1 V      H21
K10R82M  C2010 09 13.17080923 39 18.51 +00 14 54.1          17.6 V      H21
K10R82M  C2010 09 13.17502023 39 16.67 +00 13 23.3          18.3 V      H21

The first lines tell the observatory code (H21) fro the Astronomical Research Institute. A few line down you see the telescope; a 0.76-meter in diameter f/6.8 RC Cassegrain + CCD Camera. You see that Bob Holmes was both the observer( who took the picture ) and the person who measured the data. Then comes the data:

K10R82M  C2010 09 13.15907423 39 23.63 +00 19 10.0          18.3 V      H21

K10R82M is the name of the asteroid,  2010 09 13.15907423 is the time of the measurement, and the position of the asteroid in Declination and Right Ascension are 39 23.63  and +00 19 10.0, followed by the apparent magnitude of 18.3. You need at LEAST 3 of these measurements to get an orbit.

So the telescope is all set? Not quite.

I’ll show you three more pictures,  and in Bob Holmes (Director of Astronomical Research Institute)  words show what to look for when you install a new telescope:


From Bob Holmes:

“Attached are three images taken with the 30” HOU telescope.

M57_2 (Ring Nebula)

This is an image from the 30″ telescope last night, a 1 minute exposure on M57_2. There were some thin clouds moving in during this exposure.  Images have not been flat fielded, but the camera is very clean and we have no vignetting of the image field so this is not a significant factor.

Note the primary mirror is not sitting correctly in the cell or the plungers are not tightened equally around the Cassegrain hole causing the malformed star images.  This may be a little worse in this image due to a warm mirror relative to the outside air temp.  There may also be some collimation errors adding to this distortion.  I will be working on these issues in the next day or so.Correcting this will increase the limiting magnitude better than the 20.8 in M57.

There is also a misalignment in the OTA to DEC axis (does not affect image quality) causing error in pointing by several arc minutes from one part of the sky to another.  This will require re-shimming the tower that holds the secondary to perpendicularity.


Image 2 is M13_1 with a one minute exposure reaching about a unfiltered magnitude 20.0.  Due to the size of the target in the image, the scale was reduced to show the entire object.  This was taken on 2010 09 13.  As you can see the star shapes are a little better due to the mirror cooling nearer the outside ambient air temp.

M27 (Dumbbell Nebula)

Image 3 is M27_1 with a one minute exposure reaching about unfiltered magnitude 20.2.  Due to the size of the target in the image the scale was reduced to show the entire object.  This was taken on 2010 09 13. ”
Bob Holmes


So we still need to tweak the alignment, then we install the cooling fans, to cool down and keep the primary mirror at ambient temperature, (otherwise the mirror expands and changes focus).  Then more photos to see if anything needs to be done but by October everything should be fine…..weather permitting.