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Help with imaging with a Zwo ASI120MCS


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I just bought the ZWO ASI12MCS camera. Using the camera alone in my refractor focuser, I can take reasonable video of Saturn using Firecapture. But Saturn appears very small. When I plug the camera into a 2X or 3X Barlow to increase magnification, Saturn does not show up at all on my computer screen. I have tried defocusing the image to make it larger and I have tried turning up the gain in Firecapture to actually see Saturn on the screen but can't find it. I try to center the image in the reticle without the Barlow then adding the Barlow but still lose the image. Can anyone offer some guidance here?

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Can you achieve focus with the camera and Barlow? When I add the Barlow I also have to add extension tubes at it pushes the focal point past the outer limit of the focuser.

Sent from my iPad using Tapatalk

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Lots of possible reasons. Most likely:

- the field of view greatly reduces when adding a barlow so there is a high chance the planet isn't in the fov

- when adding a barlow, the focal point shifts, and if something dim like saturn is out of focus, you win't see a thing.

- depending on what scope you have, adding a barlow may mean you can not achieve focus

Have a go in day light by looking at something distant on the horizon (or something bright like the moon) and work out if focus can be achieved, and if so how much adjustment in focus you need to make (number of quarter turns say, and in what direction) and note this down and use that at night.

Good luck

James

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  • 3 weeks later...

I have experienced this problem, I had achieved focus with a 5x Televue in day light using a distant object, but could not do so with Saturn.

As James says, the field of view greatly reduces when adding a barlow, and in my case it was exactly the problem, I simply wasnt pointing at the target.

I got around it by fine tuning/dialing in the finder scope to the best degree possible, then using it to re-find the target after knocking the scope about when fitting the Televue. It also helps to set the firecapture resolution to achieve the widest field of view possible to start with.

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I achieved what I thought would be impossible by meticulous aligning - I imaged Jupiter with a Philips SPC900NC, through a X2 Barlow, using a (obviously unguided) SW Skyliner 200p Dob.

During the day I used a reticule eyepiece to get a single Beech nut at the top of a faraway tree (it was a calm day!) aligned in the center and then aligned my RACI up, toing and froing until they both matched perfectly. I put the camera in the focuser, taking out any slop by winding a single layer of masking tape around the camera nose. After a few practice runs I was confident that when Jupiter hit the finder center I got a central image on the laptop. Then I dropped the Barlow in.  Tracking the planet was a nightmare, I was relying on the flexure of the tube rather than the Dob bearings, because as soon as you got over the friction the mount would jump way too far. This was my image:post-30409-0-26734800-1430397654.jpg

Moral - spend tons of time getting things perfect before venturing out at night!

HTH,

Neil.

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