
26-12-2013, 10:20 AM
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Join Date: Jul 2008
Location: Sydney
Posts: 76
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Nothing is going to look as detailed through the scope as any of those great images of the galaxies etc. It is all to do with the light, basically the photographs are often long exposure and usually multiple images stacked together. They also use high end gear which increases the detail captured. Specialised cameras, superior optics and focus techniques and so on.
You can see a fair bit with a 10 inch scope but the image will not look like those photographs. You would need a massive scope and some great seeing conditions.
As for photography. It depends on many things.
I currently own a 12inch Dobsonian, which severely limits my astrophotography.
Not sure if your scope is a Dobsonian or has an equatorial mount. The Dobsonian is easy to use but it doesn't have any tracking ability. Even with Goto tracking it is not possible to take long exposures.
You have to get near perfect alignment to even manage a 10 second exposure. Sure you can stack multiple exposures but field rotation then kicks in.
Field rotation means the field literally appears to rotate it is more noticeable near the edges. It gets quite severe after a few minutes. This includes if you take a ten second shot then another and another etc. Eventually the field is rotated so much that you can not stack the images.
Now you can get field derotators but they are another cost and thing to learn. Easy enough once you get it but I suspect even then other tracking errors will kick in if you are not using an equatorial mount.
But alas all is not lost. You can take great photographs of the moon Saturn, Jupiter, Mars, possibly Neptune and Uranus. You might even grab a few second exposure on a few bright deep sky objects (star clusters work well).
One relatively easy way is afocal. You just set your camera lens to infinity and point it at the eyepiece. Some people get good result doing this but I have found it to be hit and miss often with vignetting and out of focus areas. But if you take enough shots you get a few that turn out.
Attaching your DSLR is pretty easy all you do is attach the adapter and then attach it to the scope. The problem is focus. You will probably need about 45mm extra focus (plus however long the extension tube is if you have one (I have one that is only a few mm). A good thing to try is focus using an eyepiece and measure the distance to the sensor (at least close enough to it) and then see if the focus tube has that much play.
I hade lots of trouble with focus. My telescope will not focus at prime focus on my camera sensor.
I also considered eyepiece projection. Same problem with focus if not worse in some cases. However some lateral thinking got it working moderately well.
What I ended up doing is getting a camera extension tube and a Plossl eyepiece. I unscrewed the silver tube from the eyepiece and screwed that directly into the nopiece part of my adapter (it should screw off the camera adapter). Then I attached the camera extension tube via a T-ring (teleconverter). Then I attach that to my camera and telescope.
It works only with certain eyepieces,, you can not remove the end on most of them but with Plossl's I find a fair few you can. I found the best results using a 13mm and a 20mm Plossl.
Now with this method you los a lot of light. So your exposures start getting longer for example I use about 1/40th second as ISO 400 for the moon and ISO 800 for Jupiter. This is short enough to minimise most tracking errors but the higher the ISO the greater the noise you get. I usually take one or two shots and stack them. Works for me.
Keeping the extension tube as short as possible (while still allowing the eyepiece to fit inside and not inside the camera itself) will help keep exposures down.
I hope I helped you out I worked this out after a fair amount of trial and error. But now I can happily take photographs and even movies. It isn't perfect but it works.
I now have a nice CCD camera which helps with my focus issues. But alas that is another learning curve
Sorry for the long post . The photography aspect can be tricky to get right. It took me a fair bit of thinking, reading and confusion to get it right on my dob. I really like the results though . When you start capturing a few images you will be happy. The experimentation is part of the journey.
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