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Old 17-02-2013, 01:39 PM
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toc (Tim)
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Off axis Guider: Atik or TS-OAG9?

I really want to go down the path of Off Axis guiding - Ive heard good reports from the Atik, but the slimline design of the TS unit is appealing. I plan on imaging with both my 12inch Meade (in the fullness of time, I will almost certainly need to update my mount for this) and WO refractor.

Given that I already have a SCT crayford focuser, Im worried that I wont have enough focus travel with the Atik unit. On the flip side, Ive heard the TS unit is tricky to adjust the guide position, due to its limited movement.

I plan on using one of the newer QHY5-II units as the guide camera.
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Old 17-02-2013, 11:53 PM
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Tandum (Robin)
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Tim, you need to look at path lengths to the sensors on both the imaging camera and the guide camera. The distance from the prism to each sensor needs to be pretty close to the same so they both achieve focus together. So it makes a difference if you are using a mono camera and wheel compared to a OSC camera. You don't want to have to put extensions/spacers between the OAG and imaging camera nor do you want the guide camera sitting on the end of a bunch of extension tubes.

You also need to consider backfocus distances to any reducers/flatteners/correctors you'll want to use. I'm setting up a new imaging train here and ended up with one of these to go between a 3" ASA corrector and a starlight wheel with the atik 11000 on the end. My problem was adapters to connect it all together. I didn't know how thin they could make the ASA flange adapter. Lucky for me it measures up just right or I'd have been forced to leave the OAG out of the train.
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Old 18-02-2013, 11:35 AM
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toc (Tim)
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Quote:
Originally Posted by Tandum View Post
Tim, you need to look at path lengths to the sensors on both the imaging camera and the guide camera. The distance from the prism to each sensor needs to be pretty close to the same so they both achieve focus together. So it makes a difference if you are using a mono camera and wheel compared to a OSC camera. You don't want to have to put extensions/spacers between the OAG and imaging camera nor do you want the guide camera sitting on the end of a bunch of extension tubes.

You also need to consider backfocus distances to any reducers/flatteners/correctors you'll want to use. I'm setting up a new imaging train here and ended up with one of these to go between a 3" ASA corrector and a starlight wheel with the atik 11000 on the end. My problem was adapters to connect it all together. I didn't know how thin they could make the ASA flange adapter. Lucky for me it measures up just right or I'd have been forced to leave the OAG out of the train.
Great advice - I will start measuring.
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