My 300th observation of Near Earth Asteroids

Near Earth Asteroids are the ones whose orbits come very close to the orbit of planet Earth. Astronomers want to keep an eye on these objects all the time and since they cannot do it, amateur astronomers happily do that for them. As of today, there are 24,158 Near Earth Asteroids known to us.

For the last few months, I have been actively involved in the follow-up observations of Near Earth Asteroids from my observatory (N31) and as far as I know, this is the only observatory which is observing NEA from Pakistan.

The following picture is the stacked image of 100 NEA 2013 PY6 images, which I observed at around 17 magnitude. The three straight lines are the lights of an airplane, which crossed the field of view of the telescope.

You can see how many asteroids are in fact in the field of view

And this is the orbit (in Grey) of this Near Earth Asteroid.

orbit-viewer-snapshot (2).jpg


Periodic Error Correction

Worm gears in the mounts has an inherent error where they introduce a star going back and forth in the image, resulting in a not a perfect round star. Worm gear cannot be made perfect.

Since this is a periodic error, this problem can be reduced by using software to figure out the error and then tell the mount how to move in order to solve the issue. This is called Periodic Error Correction.

Pempro is an amazing software which i have used to ‘perfectly’ polar align my mount and the minimize PE. Recently i had opened the whole mount and cleaned and re-greased everything. Later i put a lot of effort to properly, as far as i can, adjust all the gears back. and today i ran Pempro and here are the results:

 
 

On the top right is the PE which is stunningly good for my mount.. i would want to believe that something is not right.. an error of just and arcsond.. really? is Losmandy Titan such an amazing mount? I am very very happy with these numbers.. but seriously.. 1 arcsecond?

ZWO 183 CMOS Linearity Test

A quick linearity test of ZWO 183 CMOS chip.. this is so surprising.. the linearity goes above 60k ADU. Is the CMOS chip that good or am i doing something wrong here?

Tpoint Pointing Model Automation

Making a star pointing model is extremely important to use your telescope properly.. without it you won’t be able to see any object in the sky.

Making a pointing model with a camera is not easy either. In the past, i have spent hours and hours in a session to make a model manually for about 50 stars. The problem has always been my super small Field of View which used to 8*8 arcminutes.

Enter the new world: Wide Field of View!

Installing new equipment had given me over a degree of FOV and now is the time to try automating pointing model. So tonight i did exactly that.. Lo and behold.. this is the result:

This is the path automation followed and the circles are the spots where the exact telescope’s position was noted. In numbers, 85 points were added. Now finding any object will be a breeze by my C14 telescope. Thank you Tpoint!

Telescope Corrector Plate cleaning

This alone is the work i always want to avoid.. cleaning the corrector plate of C14 telescope. It always damages the coatings of the optics, ever so slightly but nevertheless i have to do it after a couple of years or so.

It is not at all easy to find 95% isopropyl alcohal in my city; there is only one place that i eventually found this in Lahore.

Distilled water, isopropyl alcohal and surgical cotton is all i need to do the cleaning process.. look at the difference now.. Telescope is happy now :)

Near Earth Object - Asteroid 1984 QY1 Observed

Minor Planet Center shows a list of Asteroids (Figure 1) in need of observations. A few days ago, I saw the list and there was this asteroid 1984 QY1 which observation was “desirable”. It was not that dim at magnitude 16 so i had to observe it.

Figure 1. Minor Planet Center’s generated list of targets near a position i selected

With unguided 60 seconds of sub exposures, i recorded it at 16.4 magnitude (Figure 2). Figure 3 shows the stacked image where the asteroid is right where it is supposed to be.

 

Figure 2. 1984 QY1 observed at magnitude 16.1

 
 

Figure 3. In stacked image, position of 1984 QY1 is shown in red box

 

Dark Noise vs Temperature

When we first step in astrophotography, among the first instructions we hear is you CCD needs to be cooled. There are many cameras for lunar, solar and planetary imaging which do fine without cooling because the targets are very bright. But for Deep Space Objects, which are very faint, we need cameras which can be cooled below 0 Celsius.

C14 with SBIG ST9XE CCD Camera

My camera has a regular peltier cooling option and it has an advantage of water cooling as well. These days i am not using water cooling because pipes must be attached and it pulls the scope which in turns troubles the mount in making an accurate pointing model.

I did a test run of my camera to actually see how much Dark Noise it generates at different temperatures. I acquired 60 frames of 60 seconds subs and then BIAS subtracted them and then stacked them. Then i measured the average Pixel Value of the Dark Noise and plotted it with the temperature range from -20C to +35C with 5 degrees increments. The results are interesting.

Figure 1 starts with a lot of Dark Noise in the frame which was captured at +35C and then it ends with a frame at -20C. One can see the dramatic effect of lowering of the noise with lower temperature.

Figure 1. Animation of 12 frames of CCD having temperature of +35C to -20C

The graph (Figure 2) shows it in more detail. Above 0C, the Dark Noise increases rapidly.. kind of exponential growth. At +35C, the average pixel is producing some 10K ADU value. Now this is extremely high and no Deep Space Object can ever be imaged at this temperature with this CCD. Now DSLRs have low noise generating CMOS chips and they do get to have some nice Deep Sky Objects. There are those who install cooling units in their DSLRs to get more faint signal coming from space.

Below 0C, the noise is comparatively very low. Yes cooling gets you to image very faint object but there is not a huge difference of dark electrons generation in sub zero CCD temperatures.

Yes Pros use liquid nitrogen etc.. but that’s quite a different world than our mare mortals’. So yes.. we should be all happy with our sub zero chips. We have bigger enemies than CCD temperature.. we need to kill the clouds first!

Figure 2. Dark Current Vs CCD Temperature

Solar Outreach at Science Festival Faisalabad