CCD vs Film? Lots of time vs no patience? Alright, this is your place to discuss all the astrophotography what's and what's not. You can discuss about techniques, accessories, cameras, whatever....just make sure you also post some nice photos here too!
can anyone explain to me what the 3rd pic is talking about? under the part "UNDERSTANDING HOW IT WORKS"
It basically show that it'll took a very, very long time for the star at the eastern/western sky to show any drift if your AZIMUTH is misalign. So you must use stars near the intersection of the meridian and the celestial equator for Azimuth alignment.
also which stars do you guys choose for your polar alignment?
Any stars that you can see near the intersection of the meridian and the celestial equator... basically straight overhead in Singapore and any stars you can see that is about 15 - 20 degrees above the Eastern/Western horizon.
Have a nice day.
Yang Weixing "The universe is composed mainly of hydrogen and ignorance."
perseid wrote:If you have a camera that has exposure of over 2 minutes, you can do the "digital" way of alignment.
Instead of using an illuminated recticle, I use my DSLR camera to do my polar alignment.
Here is the way.
1) Attach your camera to your telescope, like you do when taking images. Focus as good as possible.
2) As with the manual alignment, place a star near the zenith in your camera field of view. Set your exposure around 200ASA (too high ASA, stars may be washed out).
The total exposure time is 2 mins and 10sec. First 10 seconds of exposure, just leave your camera and the mount drive on.
For the next 60secs, press either RA+ or RA- button with 2x sidereal speed. After 60secs, press the other way.
You should get an image such as these.
Your first image may be similar to the one on the left. As you can see, initially the star is on the left side, but after 2 minutes, the star has drifted to the right. Don't worry about which direction the star move, either N, E, S or W. Just adjust the polar axis of your mount, slightly to the east or west. Then repeat the procedure. You can stop the alignment process when you only get a straight line, and not "v" shape.
You can do the same thing for declination alignment. Just point your camera as near to the eastern or western horizon.
Very good method!
Only thing is, is there a rule to determine whether should u adjust towards east or west?
perseid wrote:If you have a camera that has exposure of over 2 minutes, you can do the "digital" way of alignment.
Instead of using an illuminated recticle, I use my DSLR camera to do my polar alignment.
Here is the way.
1) Attach your camera to your telescope, like you do when taking images. Focus as good as possible.
2) As with the manual alignment, place a star near the zenith in your camera field of view. Set your exposure around 200ASA (too high ASA, stars may be washed out).
The total exposure time is 2 mins and 10sec. First 10 seconds of exposure, just leave your camera and the mount drive on.
For the next 60secs, press either RA+ or RA- button with 2x sidereal speed. After 60secs, press the other way.
You should get an image such as these.
Your first image may be similar to the one on the left. As you can see, initially the star is on the left side, but after 2 minutes, the star has drifted to the right. Don't worry about which direction the star move, either N, E, S or W. Just adjust the polar axis of your mount, slightly to the east or west. Then repeat the procedure. You can stop the alignment process when you only get a straight line, and not "v" shape.
You can do the same thing for declination alignment. Just point your camera as near to the eastern or western horizon.
can anyone explain to me what the 3rd pic is talking about? under the part "UNDERSTANDING HOW IT WORKS"
It basically show that it'll took a very, very long time for the star at the eastern/western sky to show any drift if your AZIMUTH is misalign. So you must use stars near the intersection of the meridian and the celestial equator for Azimuth alignment.
also which stars do you guys choose for your polar alignment?
Any stars that you can see near the intersection of the meridian and the celestial equator... basically straight overhead in Singapore and any stars you can see that is about 15 - 20 degrees above the Eastern/Western horizon.
VinSnr wrote:Only thing is, is there a rule to determine whether should u adjust towards east or west?
Most of the time, I just check if the "V" get bigger or smaller, to determine if I am getting closer to alignment or not.
Actually, you can know exactly which direction to move your mount. As with the manual method, you must determine if the star is moving northward or southward before fine tune your alignment. When I have a star in the FOV, I'll slightly move the scope northward or southward. while bserving the star behaviour. If I am using my DSLR to look at the star, then the orientation is correct. In this case, if I move my scope northward, the star should move in the opposite direction (south).
When looking at the image, as were are exposing the star with tracking on for the first 10 seconds, it should be recorded as a dot. During exposure, it will make the "V" line. So, you will end up with a "V" with a dot on one of the end. This is where the star were during the start of the exposure. The star at the end of the exposure is at the other end of the "V".
"The universe is composed mainly of hydrogen and ignorance." 
ake more time only