Why do the stars twinkle

 

 

This video not only has a beautiful view but also shows a very common phenomenon knows as 'twinkling' (Try HD viewing here). This is very well known with the stars we see in the night sky but this video is showing the street lights twinkling as well. The further they are the stronger is the effect.

So what is twinkling anyway.. my Oxford dictionary of Astronomy defines it this way:

The rapid fluctuations in brightness of stars, more properly known as scintillation. Twinkling is caused by atmospheric turbulence distorting the incoming wavefront from a star. Twinkling is less noticeable in planets, which have an extended area. Excessive twinkling is a sign of bad seeing.

A light ray not only changes its speed but it also bends its path when it moves from one medium to a different medium, which have different densities. The vertical rising air and the fast moving horizontal air in the atmosphere are constantly creating different pockets of various densities. Which in turns varies the refractive indices of different regions in the air. Here when and where the wavefront is convex, the light rays converge and where the wavefront is concave, the rays diverge. This concentrates and de-concentrates the energy of the wave in certain patches. Twinkling is born.

These changes begins in the high layers of earth's atmosphere and extends all the way down to the earth or inside your telescope tube and even on the surface of the mirror or lens.

So to keep the observatories more thermally balanced they now have windows like features in the domes' walls which are opened when needed. In my observatory, which has a roll off roof structure, i have tried various ways to make seeing as good as i can. Since it is on the roof top of my house which has bricks all over, in hot season, i sprinkle water on the roof when the sun goes down. In about two hours when i am ready to image, the evaporating water has already taken a lot of heat from the brick roof.

I have also tried multiple times to turn on a pedestal fan at various speeds in my observatory in the hope of getting the convection layers as low as possible but honestly i have not noticed any difference in my seeing, perhaps the structure of my observatory does not allow convection currents in the air to minimize this way. The other problem is the mount, at these high wind speeds and such a long focal lengths the mount does shake and the image degrades so the fan is not helpful for me.

Adaptive optics technology in the professional observatories helps a lot in minimizing the bad seeing.. these 'rubber optics' which can adjust according to the incoming wavefront are one of the key technological marvel that astronomers can really feel proud to have. Though my SBIG AO-8 is marketed as adaptive optics but in reality it does not have a bending optical instrument, rather it has a lens that can move on two axis at quite high speeds. It actually is a good guider than a bad seeing corrector device.

Coming back to this video, the far off street lights are traveling such a long distance that the varying densities of air, caused by the movement of hot air, are making them twinkle. The nearest lights are much less effected and show quite a stable sources of lights.. great view!

More halpha 3D processing

Today, two separate files were recorded, one for dim prominences and the other for bright solar disk. Among 7,000 frames, 1,500 were selected, aligned and stacked in AviStack; sharpened in Registax and combined and processed in Photoshop CS5.

Twitter Posts

I saw an option on squarespace which can be used to add twitter posts at my website. So i have added a page for my tweets here. I will be posting about my thoughts and activities in and out of my observatory but mainly for my telescopic observation and imaging. You can follow me here what i am upto with my equipment, my failures and my successes.

Sunspot 1598

There are three active sunspot region on the sun. Solar & Heliospheric Observatory (SOHO) is showing the following image right now:

Solar disk with sunspots (SOHO website)

I have got AVIs of all these three regions but the most interesting is 1598; it has a complex structure and is  quite a big one. when compared with our earthly standards. Following are the images from my processing run or lets just say, "image ladder" AVI file contains many hundreds or thousands of images. Seeing allows both worst and good views to pass through the atmosphere. The image on right is the worst image in the AVI and on the left (traces of granulation) is the sharpest one.

After aligning and stacking in AVIstack, and then a pass through Registax and Photoshop here are the final mono and colored images.

And here is the comparison with our planet.. now you can truly see how big is this region when earth is put to scale here:

Sun today in halpha wavelength

Just got some videos from Imaging Source DMK21 camera and processed them.. This is happening on Sun today.

Telescope is back in the observatory

Shifting the monster is never easy.. and this is the only reason why i 'want' to avoid public sessions with my C14 and Titan mount but could never avoid to avoid this want.

An off day provided the opportunity to put back everything where it truly belongs.. i still have to figure out some cables issues and want to put back the main CCD setup at the telescope.

After attaching Lunt halpha telescope with the C14 OTA, i got a quick look at the sun.. and immediately saw a huge prominence where the arc was attached to the solar surface on both sides. I thought i must image it. So i installed imaging source DMK21 camera with this scope and carefully tuned the pressure tuner and focuser and quickly grabbed a few movies. Here are the results.. not bad!

Thandiani tour

So Thandiani was great.. so many people joined us from three different cities: Lahore, Islamabad and Abbottabad. I, on the behalf of Lahore Astronomical Society, am very thankful for those crazies who drove all the way up to the 9,000 feet high peak.

It is always nice to be up there.. i think i have been going there for fifteen years now and the main reason is that Thandiani has extremely raw night skies and it has a great scenic beauty; plus for us 'land dwellers', mountains always have very pleasant weather. The above shot is the morning view from my mobile camera, just a few yard away where we were staying.

Though we were struck by the astronomers' nightmare (clouds and a bit of rain), the sky did allow us to set our telescopes and watch clusters, binary stars and planets. Milkyway is always one of the best treats a good night sky can offer us.

I enjoyed meeting my old astro pal Saif Sahib from Islamabad and my new friend Asadullah from Abbottabad. We had a lot of time for our heavenly and earthly talks and everything in between.

I so wanted to image from Thandiani but this time clouds won.. Also, this time i did notice a considerable decline in the quality of night sky there.. It seems the nearby city Abbottabad is growing fast and in a few years we will definitely loose the advantage of a light pollution sky at Thandiani. 

Thank you again everyone who came for our two nights observation session at the mountains.. more trips coming up..

KSS and Suparco collaboration on WSW

This afternoon Suparco and Khwarizmi Science Society made a wonderful public event at Gulshan Iqbal Park, Lahore. Water propelled rockets were just great! Telescopes, Seismograph, crater mkaing material, lunar phases, satellites models, introduction to space movies and many posters were being presented to the public. 

World Space Week at FC College

WOW.. what a sun gazing session it was! We had set three telescopes there, two with Solar filter on and one halpha solar telescope with a binoviewer at the eyepiece end.

For three hours, students and faculty members kept on coming to our telescopes and most of them saw the solar surface first time in their lives. I heard many many 'WOWs" during that time period. It was a hot day and i with many others were trying their best to fight off the heat with all our astro will.

We were asked all sorts of question about how the sun generates such massive energy and what does individual feature on the solar surface mean, which they all were watching through these telescopes. 

I am very grateful for the media folks from Express Tv Channel, to have come there and recorded all the event and stayed there till the end. I am also very thankful to "Benade Physics Society" of FC College and specially their president Amina Saleem.

As always, the members of Lahore Astronomical Society always find time to arrange such events. Special Thanks to Maroof Mian, Ali Khan and Muhammad Ali.

Big Prominences

Solar Halpha Mosaic

9 AVI files, 5,000 frames each, AVIStack, Registax and Photoshop.

Lahore Astronomical Society's October Meeting

I am very grateful to all those who came this evening in our monthly meeting. It was also great to see so many students from Space Science Department.

Ali Khan, our head of ATM (Amateur Telescope Making) gave a thorough introduction of mirror making and then how to make a telescope. The grinding methods and polishing was beautifully explained by showing each step with the mirrors in hands. He also described some key terminologies and the advantages and disadvantages of various configurations of the mirror designs. Many attendees asked important questions of the procedure of grinding techniques and Ali, as he always does, came up with easy to understand words/examples that kept us hooked during his whole lecture. He was thanked with a big round of applause.

World Space Week will be very busy for us.. So many vanues were under discussion. FC college will probably be our first venue with solar observations both with white light solar filters and with Halpha dedicated solar telescopes.

And last but not least, we are definitely going to Thandiani, Abbottabad and the number of participants are growing so fast.. Perfect!

These are the pictures taken by our dear member Mudassir, who is always great with his camera.

More sun in '3D'

Someone in Lunt mailing list showed me 'solar action'.. I was in search of a method to easily color the mono images from halpha telescope. This tool is really a blessing, though i only like to color tool, others seems worthless to me.

Following is the first attempt with 'solar action'.

3D effects in processing

There are unlimited ways to process an astronomical image. Every imager has his/her own taste for the 'pretty picture'.

Some halpha imagers process by inverting the B/W image.. and then add colors to the image. It makes the filaments on the surface look like 3 dimensional.
I did just that with the following image and to me, it seems the 3D effect does appear with this processing technique.. what do you all think about it?

Sunday Solar Mosaic

Six AVIs, with 5,000 frames in each file, 800 best selected among them, using AVIStack, Registax and photoshop, here is our Mighty Sun, with the surface temperature of about 5,800 degrees celcius, with the core temperature of 15,000,000 celcius.

With this temperature it is fusing 600 million tons of hydrogen every second! 4 million tons of matter is converted into pure energy, every second and in only 10% of its volume and it will continue to do that, for the next 7,000,000,000 years! Sun is busy.

More halpha images today

All images were shot with DMK21 camera and with Lunt60 dedicated Halpha telescope with Televue 2.5X barlow attached.

Again each file was of 5,000 images, 800 best were selected aligned and stacked in AVIStack and sharpened in Registax. Final touches were done with Photoshop CS5.

Halpha Solar mosaic

Okay so today was my off day from work.. what better way to use your holiday than to spend all day with your dearest one.. (okay okay.. after my wife :)

Sky was all clear and seeing was also very stable. So i attached my barlow lens which magnify the image 2.4 times than the original image. Before the televue, barlow lenses were thought to degrade the view so astronomy community always tended to avoid these lenses. Things have long changed now. Telvue 2.5 X barlow does not even tell you its there.

I shot several AVIs files, each with 5,000 images and processed 800 out of them and made a mosaic.

Here is the color version and original size of the mosaic.

A broken heart

Our sun is quite these days with very few sunspots at the visible surface. There is no  good solar prominences as well.

Few days ago, i imaged a small sunspot, which is quite huge by our terrestrial standards. This spot has moved to the eastern limb now and a new region has appeared from the west (see arrowhead below). On the full disk it is barely definable but in  my image our Sun has just shown us its broken heart!

Click here for high resolution image

At least three sunspots have merged to create this group. Coming forecast seems to be clear for my location so i will try to see how this region evolve in the near future. Sun is a highly dynamic system and it is always going through visual changes. I also saw this region with Halpha telescope but i think i would wait for some time to image it in halpha light.

Granulation and sunspot

The sky was covered with patches of clouds everywhere, yet i tried to have first shots from the new Astrozap solar filter. The new filter was much better designed to fit on the front of the telescope, with three screws attached, the fit was in just a few seconds.

First i used my 25 mm eyepice at the back of the scope and the visual views were not bad but so very detailed since the earth clouds were moving across the surface of the sun. But the two sunspots and three tiny ones were clearly visible.

Then i attached DMK21 camera and shot an AVI of about 20,000 images. Quickly processed it with AVIStack and Registax and here is the final image, my first from the new filter!

I am happy to see the individual granules on the surface of the sun which i could not have seen with the Lunt60 Halpha solar scope previously. Solar granule is a small bubble in the image below and typically is around a thousand kilometer wide.. that's about the distance from Lahore to Karachi! The bright part is where the hot material is coming up on the surface and the dark boundary is where it is falling down again. These granules are the convection zones on the sun's surface.

The big sunspot in the middle is quite small when you see it on the solar disk here. I very roughly figured the size of this whole sunspot to be about 40 granules, so that would make it to be around 40,000 km wide. Thats like three times the size of our planet Earth. Sun is huge!

The whole disk of the sun. Image from Spaceweather

Astrozap white light Solar Filter

In the past, I have been using Thousand Oaks Solar filter which does not work so good when it comes to high resolution viewing of the Sun.

Thousand Oaks filter is made of glass and is an off axis filter. C14 telescope is too big to have a full aperture front solar filter because although solar filters drop the sunlight and solar heat way down, still in a big aperture telescope like C14, the amount of heat would generate too much temperature instability which will degenerate the solar views. That is the reason, probably no one makes a full aperture front plate solar filter as big as C14 can use.

Unlike Thousand Oaks, Astrozap uses solar film in their filters. Solar film filters have an advantage over glass filters when it comes to high resolution viewing and imaging of solar surface granulation. Though glass is much more durable than a film. It's hard to take care of solar film filters. But film can easily be replaced with a new one; these are not so expensive.

So the new upgrade is of the New Astrozap Film Filter for my C14 telescope! The off axis filter makes C14 essentially a 6 inch refractor scope. With the central obstruction of the secondary mirror gone from the view, this scope can provide very high resolution of the sun's surface.

In the image, you can see Astrozap white light Solar Filter attached on the front Schmidt plate of C14.