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Old 12-09-2009, 06:33 PM
Crusader
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Neximage and focusing

I had my first imaging session last night (will post results later). I'm struggling to get perfect focus.

I've made a Hartmann mask but when trying to focus on a star nothing is showing up. Could the Neximage not be sensitive enough or am I just missing it in the fov.

In desperation I used the mask to focus on Jupiter directly and that seemed to work (to a degree). Would focusing on a star first achieve better results?
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Old 12-09-2009, 11:14 PM
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mithrandir (Andrew)
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A Bahtinov or Carey mask is likely to work better. See the thread http://www.iceinspace.com.au/forum/s...ad.php?t=47090 for one member who makes them. I bought two from him.

A NexImage is only likely to pick up fairly bright stars. It is only intended for solar system work.

What scope are you using? On my C8 it does work down to about mag 5 or 6 but that's about it. I would not use it for deep space photography.
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Old 13-09-2009, 12:28 AM
Crusader
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I'm using it on the 8SE. I think my problem is that I'm just missing the star from the FoV and without an optical finder it's a bit difficult to get the star in the FoV.

If conditions hold I'll give it a try again tonight.
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Old 13-09-2009, 11:10 AM
picklesrules (Nicholas)
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hey man ive got a neximage and ive found that it dosent really pick up stars that well, i think last yr i tried it on sirus and still got nothing, your best bet for focusing is a bahtinov mask if u want to, focusing on a planet like jupiter
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Old 13-09-2009, 09:34 PM
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mithrandir (Andrew)
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Quote:
Originally Posted by Crusader View Post
I'm using it on the 8SE. I think my problem is that I'm just missing the star from the FoV and without an optical finder it's a bit difficult to get the star in the FoV.

If conditions hold I'll give it a try again tonight.
The NexImage on an 8SE (or a C8 which has the same dimensions) has a FOV of 4.5 x 6.1 arcmin. That is pretty small. You have to be really accurate with your alignment to get a small object on the CCD. Something large like the moon is harder to miss.

It is more usable on a shorter scope. For instance on an 80mm scope with 400mm focal length it gives 23.1 x 30.8 arcmin - about 5 times the linear dimension and 25 times the area.
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Old 11-10-2009, 07:54 AM
p3nn (James)
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Something else to consider would be the cameras settings. What works for me is to turn off "full auto", set "white balance" to auto, set "gain" and "gamma" to minimum, set "brightness" and "saturation" to the middle, and then adjust the shutter speed until you get the desired result. I've had no probs imaging stars with it so far. Even been able to separate Rigel Kent's companion in the shots

Hope this helps
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Old 11-10-2009, 10:16 AM
p3nn (James)
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Also how are you trying to focus. What I end up doing is placing in a 3x barlow and a 20mm eyepiece for the initial focus. Then I'll swap the eyepiece for a 12.5 mm and recenter the image in that. Then when I place the neximage into the barlow the image is at least in the capture window and I can finish the focus and aligning from there
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