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Old 27-11-2020, 05:37 PM
MarkInSpace (Mark)
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Is a 1.25” filter large enough for ASI294MC Pro

I’m wondering if 1.25” filters will be ok on my ASI294MCpro - currently i use 2” filters and a filter drawer, but a small filter wheel+1.25” filters would be a lot cheaper, especially if i change over to an ASI294MM.
I understand vignetting may be a problem, I would like to hear actual experiences
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Old 28-11-2020, 11:54 AM
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Camelopardalis (Dunk)
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I use an ASI1600MM, which is only slightly less in diameter than the 294. With my Esprit 100 at f/5.5 the vignetting isn’t noticeable. With my Quattro at f/4 it is. The light cone is just that bit steeper at f/4.

So I think it will depend on the focal ratio of your scope...
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Old 28-11-2020, 03:47 PM
MarkInSpace (Mark)
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Excellent input

That’s really interesting, I hadn’t considered that aspect.
I have a 115mm F7 with a 0.8x reducer corrector, so I probably should be fine, I guess.
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Old 28-11-2020, 08:52 PM
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No guarantees, but it should be bearable (correctable with flats).

Also be careful if you do see some vignetting that you don't mistake it for the reducer... if the reducer has a 2" barrel, then that's creating an obstruction before it gets to the filter.

Oh and fwiw, put the filter as close to the sensor as you can. ZWO usually include a little ring that you can thread a filter into and then thread that into the 10mm female-female spacer when it is on the front of the cameras. That gets the filter a few mm in front of the sensor chamber glass.
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Old 29-11-2020, 12:55 PM
Zuts
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Quote:
Originally Posted by Camelopardalis View Post
No guarantees, but it should be bearable (correctable with flats).

Oh and fwiw, put the filter as close to the sensor as you can. ZWO usually include a little ring that you can thread a filter into and then thread that into the 10mm female-female spacer when it is on the front of the cameras. That gets the filter a few mm in front of the sensor chamber glass.
I would be interested to know what is the benefit of this? Currently I screw the filter into the base of the reducer rather than into a camera spacer.

Cheers
Paul
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Old 29-11-2020, 09:40 PM
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It’s because you don’t want the filter to be an obstruction and cut into the light cone. 1.25” filters have clear aperture of about 28.5mm, so you’ve not got a lot to play with when using a sensor size like the 294.
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