Really amazing! The auto-guider is really effective... only require a 700mm guide scope. Unlike manual guiding, which require a guide scope that has at least 2 times the focal length of the main scope.
Have a nice day.
New image: M86,84 and more than 20 more galaxies
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tanguan2001
- Posts: 146
- Joined: Fri Oct 10, 2003 10:06 pm
- Location: Braddell
- Contact:
Arief,
I focus using a Hartman mask and with the help of DSLR Focus. The mask is just 3 holes cut into a piece of cardboard that fits over the apeture of the scope. DSLR Focus handles the mechanics of taking an exposure, and displaying it on the screen.
Point at a star, trip the shutter. It's out of focus if the star appears as 3 dots rather than one. Adjust till the 3 dots become 1..
Things to look out for - exposure must be as short as possible while still being able to see the star image. DSLR Focus helps with changing exp times from the PC.
- also watch out for multiple stars. The always appear as multiple dots! Consult your star chart. There are so many multiples that some time I do rough focus on a bright multiple then switch (with longer exposures) to non-multiple for fine focussing.
Hmmm - turned out to be quite a long explanation...
On the autoguider - its GuideDog with my SAC7 running long exposure - this really is an art. I haven't got it right yet. Lots of parameters to play with on the software as well as on the mount. Lots more experimenting to do, but I try to be systematic and record any changes. In practice the focal length of the guidescope has not turned out to be limiting because the pixel size of the SAC7 is smaller than the Canon so each pixel in guiding covers about 2/3 of a main camera pixel - hope this all makes sense...
TG
I focus using a Hartman mask and with the help of DSLR Focus. The mask is just 3 holes cut into a piece of cardboard that fits over the apeture of the scope. DSLR Focus handles the mechanics of taking an exposure, and displaying it on the screen.
Point at a star, trip the shutter. It's out of focus if the star appears as 3 dots rather than one. Adjust till the 3 dots become 1..
Things to look out for - exposure must be as short as possible while still being able to see the star image. DSLR Focus helps with changing exp times from the PC.
- also watch out for multiple stars. The always appear as multiple dots! Consult your star chart. There are so many multiples that some time I do rough focus on a bright multiple then switch (with longer exposures) to non-multiple for fine focussing.
Hmmm - turned out to be quite a long explanation...
On the autoguider - its GuideDog with my SAC7 running long exposure - this really is an art. I haven't got it right yet. Lots of parameters to play with on the software as well as on the mount. Lots more experimenting to do, but I try to be systematic and record any changes. In practice the focal length of the guidescope has not turned out to be limiting because the pixel size of the SAC7 is smaller than the Canon so each pixel in guiding covers about 2/3 of a main camera pixel - hope this all makes sense...
TG
Hi TG,
I've used a 3-hole Hartmann mask too, with the canon 300D to do fine focus. However, I don't have an autoguider, so I have lots of trouble trying to do my drift alignment as well. Is the autoguider something that is a must ? Are there other alternatives ? I have a Meade DSI. Do you think this can even obtain any decent results (I haven't been successful so far).
JB.
I've used a 3-hole Hartmann mask too, with the canon 300D to do fine focus. However, I don't have an autoguider, so I have lots of trouble trying to do my drift alignment as well. Is the autoguider something that is a must ? Are there other alternatives ? I have a Meade DSI. Do you think this can even obtain any decent results (I haven't been successful so far).
JB.
Celestron 9.25SGT, Meade ETX125, Orion ED80
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tanguan2001
- Posts: 146
- Joined: Fri Oct 10, 2003 10:06 pm
- Location: Braddell
- Contact:
JB,
You can do drift alignment without the guider. Just set up, aim at a star close to overhead, and take an image, say every 15 to 20s. If your alignment is out the star will drift either north or south. Described more here:
http://www.angelfire.com/space2/tgtan/techniques.htm
This will eventually rid you of the drift north or south - a result of mis-alignment with the polar axis. It will not get rid of any error in tracking speed in RA. So if you want to do any long exposures (how long depends on the accuracy of your mount) you will have to guide. With my GPD, at f6.3 the limit is about 90s. With shorter focal lengths this can be longer.
My own experience has been that getting autoguiding going has been a liberating experience - highly recommended.
Don't know enough of the Meade DSI to say if it can be used for imaging.
Hope this helps.
TG
You can do drift alignment without the guider. Just set up, aim at a star close to overhead, and take an image, say every 15 to 20s. If your alignment is out the star will drift either north or south. Described more here:
http://www.angelfire.com/space2/tgtan/techniques.htm
This will eventually rid you of the drift north or south - a result of mis-alignment with the polar axis. It will not get rid of any error in tracking speed in RA. So if you want to do any long exposures (how long depends on the accuracy of your mount) you will have to guide. With my GPD, at f6.3 the limit is about 90s. With shorter focal lengths this can be longer.
My own experience has been that getting autoguiding going has been a liberating experience - highly recommended.
Don't know enough of the Meade DSI to say if it can be used for imaging.
Hope this helps.
TG
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Dark Prince
- Posts: 44
- Joined: Tue Nov 16, 2004 5:25 pm