Old 05-12-2020, 07:30 PM
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Loupy31 (Peter)
Invented the Four Track

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Focal reducer

Hi Guys

Ok, I have an ASI294 mc pro, its attached to An Orion ED 80,
If I place a .85 reducer into the optical path, will the focus distance be closer to the scope ?

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Old 05-12-2020, 09:03 PM
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Joshua Bunn (Joshua)
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Yes, it will focus closer to the telescope, a Barlow (focal extender) will push the focus away from the telescope.

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Old 05-12-2020, 09:10 PM
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I have a TV85 with a FL of 600mm. I use a 0.8 reducer which gives me a 480mm FL.

Bearing in mind ZWO cameras require a 55 mm backfocus I have spacers screwed into the camera so that there is 55 mm between the top of the reducer to the chip.

When I measure with a tape there is 480 mm from the front lens of the scope to the lens of the reducer when everything is in focus.

You have an ED80 which has the same FL, but a 0.85 reducer. So I would do roughly the same to get a rough focus, i.e camera with 55 mm of spacing to the chip, then reducer, then roughly 510mm to front of telescope lens and you should see stars when you take a photo. Then you need to fine focus from there.

Last edited by Zuts; 06-12-2020 at 02:00 AM.
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