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1.25" filters in a 2" focuser interface

ZWO ASI1600MM Equipment Filter Wheel CMOS
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EvlLeperchaun avatar
EvlLeperchaun avatar
Hello,

I am about to purchase the ASI1600mm-c with the EFW. I am going through the manual to make sure I have all the parts necessary and in the section for attaching the filter wheel, it mentions using the 1.25" adapter or the 2" adapter, depending on your focus interface. What is the affect, if any, of using a 2" adapter on a 1.25" filter?

Thanks in advance!
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Dipl.-Ing. Jörg Woker avatar
Dipl.-Ing. Jörg Woker avatar
Hi,

if the dimensions of the sensor are fitting the size of the smaller filter - it will affect nothing using the 1.25" filters. The lightpath will not be obstructed. You should have a look at the mounting of the filters, if you want to screw the smaller filters into the 2" interface you will need an additional ring for adapting the smaller filter to the larger thread…

Joerg
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EvlLeperchaun avatar
EvlLeperchaun avatar
Joerg,

So I should clarify: the filters are going into a filter wheel made for 1.25" filters. The 2" adapter is for interfacing the filter wheel onto the telescope focuser. I was wondering what the light traveling from the 2" focuser into a 1.25" filter would do.

Thanks!

Josh
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Dipl.-Ing. Jörg Woker avatar
Dipl.-Ing. Jörg Woker avatar
Joerg,So I should clarify: the filters are going into a filter wheel made for 1.25" filters. The 2" adapter is for interfacing the filter wheel onto the telescope focuser. I was wondering what the light traveling from the 2" focuser into a 1.25" filter would do.

Thanks!

Josh

Ok, the inner diameter of a 1.25" filter will be, dependant of it's construction, app. 31mm - the diameter of the ASI's chip is 21.9mm. No affect is to be expected. In Germany most sets with the ASI 1600 mono are sold with the EFWmini and a 1.25"-LRGB-Filter set as a standard configuration from various shops. The reduction from the larger focuser should not contain reflecting elements like rings, clamps or tubes, that would be what I look for to avoid optical effects from inside the setup.

Joerg
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