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Old 28-04-2017, 10:01 AM
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LaughingBeagles (Peter)
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Ok, a dumb question about my DSLR efforts

Hi All,

I've recently become the proud owner of a 102mm reflector and a bunch of other gear.

While waiting for my CCD camera to get a clean and spruce up, I thought I would have a go at taking a shot or two of Jupiter with my Canon 5D Mark II.

I was able to focus and take the shot but the image is ridiculously small. So small that zoom into crop just leaves a large chunky pixulated image.

"Ok," I thought, "go get the Barlow and see if that helps." Problem is, that I know the planet is framed but when I add the 2" Barlow to the image train, it's like Jupiter disappears. No matter that I focus all the way and all the way in looking for it (knowing it is in the FOV) it won't show.

Really got me stumped... The barlow worked fine on my old reflector (need it to bring the sensor into range).

Would appreciate anyone's thoughts.

Details for info:
Scope ED102mm
F7
714mm fl

My thanks in advance,

Pete
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Old 28-04-2017, 02:21 PM
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Retrograde (Pete)
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I suspect you might need more outwards focus - an extension tube may do the trick.
It might be worth waiting a few days until the moon is up and trying the barlowed configuration with the moon as it is big and bright enough that you should be able to work out roughly where you are at with focus.
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Old 28-04-2017, 03:52 PM
JA
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Location: Melbourne, Australia
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Quote:
Originally Posted by LaughingBeagles View Post
Hi All,

I've recently become the proud owner of a 102mm reflector and a bunch of other gear.

While waiting for my CCD camera to get a clean and spruce up, I thought I would have a go at taking a shot or two of Jupiter with my Canon 5D Mark II.

I was able to focus and take the shot but the image is ridiculously small. So small that zoom into crop just leaves a large chunky pixulated image.

"Ok," I thought, "go get the Barlow and see if that helps." Problem is, that I know the planet is framed but when I add the 2" Barlow to the image train, it's like Jupiter disappears. No matter that I focus all the way and all the way in looking for it (knowing it is in the FOV) it won't show.

Really got me stumped... The barlow worked fine on my old reflector (need it to bring the sensor into range).

Would appreciate anyone's thoughts.

Details for info:
Scope ED102mm
F7
714mm fl

My thanks in advance,

Pete
Unfortunately it's going to be small, especially on a full frame body. Your 714mm focal length will give you a horizontal FOV of 2.9 degrees, compared with a width of Jupiter of between 30 to 50 seconds.

That's between 1/348 th to 1/209 th of the sensor width. The Canon 5D MkII is 21MP and 5616pixels x 3744pixels maximum. So that would mean 5616/348 = 16.1 pixels to 5616/209 = 26.9 pixels. That's remarkable/surprising - now wonder it's pixelated if blown up.

Best
JA
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Old 28-04-2017, 05:14 PM
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luka
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Location: Perth, Australia
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Pete is right. I tried something similar with my ED80 and had to add extension tubes.

If you got a steady hand and lots of patience you can hold the DSLR by hand and move it outwards from the Barlow and watch the live view screen. If you can keep the camera parallel you should be able to get it in focus and see how many extension you need. Not the easiest thing to do and it works the best with a full moon, as already mentioned.

Having said that you will likely get a better/larger result by using a webcam with smaller pixels and recording a video. Then you can stack individual frames using autostakkert, registax or similar.
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Old 28-04-2017, 06:55 PM
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LaughingBeagles (Peter)
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Great suggestions all and will try when the moon is back with us. Times like this I miss my 550D.
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