Saturday, 26 May 2012

How to image a satellite with a telescope

I hope you all enjoyed my last post on how to image a satellite using the long exposure method, this time its time for method 2 how to image a satellite using a telescope. The things you need to image a satellite using a telescope are camera ( it will need a camera adapter so that you don't have to hold it) or webcam, a dobsanian or alt az telescope (you could try with an equatorial but it would be allot more difficult), and preferably a compass as well. The first thing you will need to do is visit the heavens above website and find out when the next  ISS pass is and what direction it comes from,  you can image other satellite but its best to start with the ISS as it is really big so you should be able to make out some detail on it. On the night that the pass is due over you need to to take your telescope and camera outside about an hour before the pass is due to let them cool, you then need to align your  scopes finder perfectly. About 10 minutes before the pass you need to loosen all the locking bolts on your telescope and point it in the right direction using you compass. Also you need to set your camera to the highest frame rate possible to stop and motion blur.  For your first pass you might want to use quite a low magnification to keep it in the field of view easier, then use the higher magnifications once you've had a bit of practise. Then about 1 minute before the pass is due you need to start recording with your camera or webcam. As soon as you see the ISS coming over the horizon you need to start tracking it with your finder scope ( a non magnified finder is best for this) , it will move very quickly across the sky so it will be hard to keep up with. Once the ISS has gone over the horizon you can now see what footage you managed to capture, your video will mostly contain a lot of empty frames and only a couple of ISS frames ( with practise you will manage to get more ISS frames in one pass.

Now that you have your video file you need to get rid of all the empty frames using virtual dub there's a tutorial for people who haven't used it before: tutorial, now you will be left with a very short movie file with only frames of the ISS in it, but you will have noticed that the ISS jumps around a lot in it.The next step is to process are video file using a program called castrator all you have to do is put in the video, select the brightness and the video size and it will then create a video file for you with the ISS in the centre of every frame. You can now either just use an individual frame for your image or you can process it in registax, you process it just like a video file of the moon. You will now be left with a single image which you can process in any software that you us for your other astrophotography images for instance photoshop. Once you have finished this process you will have your own image of the ISS. With practise you will be able to improve the image, if you have any questions feel free to contact me. Post any comments or tell me about your satellite imaging attempt below.
Part 1 is here.

Saturday, 19 May 2012

How to take a long exposure image of a satellite

Well we have had over a month of pretty much solid rain here in Shrewsbury so no stargazing could be done. So I have decided to make a post explaining the process of tracking a satellite with a telescope. At night often lots of satellites pass overhead often with different brightneses the brightest one that will pass over is the iss which is very bright therefore you don't need to use a telescope or binoculars to see it. The iss passes overhead very quickly like its a plane and will be the brightest thing in the sky apart from the sun and the moon. Once you have practised seeing the iss a few time you may want to attempt looking at other satellites like tiangog 1. Once you have seen a satellite pass over a couple of times you may want to try to image it. If you are trying to image a sattelite the best one to choose is the iss as it is one of the few satellites that you can see detail on due to its huge size. There are 2 methods for imaging a satellite they are long exposure via a camera and using a telescope to capture a close up image of it.

The first one that I will focus on is a long exposure image of a satellite. The equipment you will need for this is a camera which can take long exposure or if your camera can take short exposures you could take them one after another and then stack them using a program called startrails . Also you will need a camera tripod and preferably a cable release for your camera as this will mean that your camera does not shake will you are holding down the shutter button.The first step is to check out when the iss will be passing over your house and which directions it will be coming from. Next you need to go outside about an hour before the pass ( to give your camera time to cool ) and put your camera on your tripod and face it in the direction that the iss will come from. Next you need to set your camera to the highest exposure setting or if your camera has it the bulb setting, the final step is to set your camera to the widest aperture possible. Now you just have to wait till the iss comes into your camera view and start the exposure, and then when it is just about to leave the camera view you end the exposure. You can now edit your photo with whatever processing software you normally use. Now to you can look at your image and see how you want to improve it for next time, for instance a more interesting setting e.t.c Good luck! I will post the guide to imaging method 2 next week. If you have any questions feel free to contact me. I wish you clear skies.

Friday, 11 May 2012

How to balance a telescope

Well it's been over a month and I still haven't been able to do any more observing :( but as the rain is clearing I hope to be able to do some in the next couple of days. So I have decided to make another guide, this one is on how to balance a telescope. Balancing your telescope is important if you want it to hold its position and not slip while you are viewing an object, also if your telescope is really badly balanced then it could in extreme cases topple over. You will need to rebalance your telescope every time you attach or dispatch a piece of equipment to it. The first step in balancing your telescope is to loosen the r.a axis so that the telescope tilts one way or another, you then need to slide your counter weights along the bar until counter weight bar is horizontal while doing this it is important to make sure that the counter weight bar is over one of the tripod legs and not between them otherwise your scope could topple over. The next step is to balance the declination axis, to do this you first need to loosen the screw on your declination axis. Then you need to carefully loosen the dovetail attachment on your scope and slide the tube until it stays horizontal, then you need to tighten the dovetail attachment. Now if you release both clutches (loosen the screws) tour telescope should stay pretty much perfectly in the position you put it in, it might still need a tad more adjustment. Your telescope should now be balanced, therefore it should make your observing easier. I hope you found my guide on how to balance a telescope useful, if you need any more advice or have any problem feel free to contact me.
Below is a video showing what your telescope should be like when corrclty balanced. BTW I am putting the telescope into a position then letting it go.

Tuesday, 1 May 2012

How to use telescope setting circles

Due to the current thick clouds overhead i have not been able to do astronomy for a couple of weeks now, this also means that I missed both of the occulations :( . So i have decided to make a post on how to use telescope setting circles. On some telescopes mounts (mainly equatorial) there are 2 dials called setting circles, one of them is called right ascension and the other is declination. These are basically the latitude and longitude of the sky, the declination is the latitude and the right Ascension is the longitude. The setting circles on a telescope are used to easily locate object that aren't easily visible to the naked eye.  Once you have set your telescope up at night you will have to align the right ascension setting circle, but you wont have to align the declination ( if you are using a equatorial telescope make sure that the tilt is set to your latitude, this will have most likely been done when you bought your telescope).

The RA circle is marked in hours and then minutes each hour will have its hour number written next to it. To align the RA setting circle we first need to find an object in the sky for instance Jupiter, you then need to look up its RA for that specific date and time. Once you know that you then turn the RA circle so that the pointer is pointing to Jupiter's (or whatever object your using) current RA, your RA circle is now aligned. Then you find the objects you want to observes RA and declination for instance m42 and slew your telescope until the RA and declination pointers are pointing at the correct degree (declination) and minute (RA). You should then be able to see the object in your eyepiece. To find and object with setting circles it is generally easiest to locate it with a low power eyepiece to give you a wider field of view.

Specific note for skywatcher explorer 130:
If you have this scope you will notice that the pointer for the RA moves with the dial, this shouldn't happen. To fix this once you have aligned your RA circle tighten the screw so that the dial turns with the mount, then you can use the mark in between the R and the A as a pointer.
              This picture shows that the pointer moves with the setting circle for some unknown reason.
The Mark between the R and the A can be used as a a pointer.
I Hope you have found my guide on how to use telescope setting circles, if you have any questions feel free to ask.