What is the primary function of the Baader 2" SCT to T-2 Adapter?
It changes a male T-2 (M42x0.75) thread into a male 2-inch SCT thread (2"-24 TPI), so an accessory with a female 2" SCT thread can be screwed onto a part with a male T-2 thread. It does not screw onto the male 2" thread of an SCT rear cell.
Why is the 1mm optical length of this Baader adapter so important?
The minimal 1mm optical length is critical for astrophotography. SCTs, especially when used with a focal reducer, have a very specific and limited back focus distance required for sharp stars across the field. This ultra-thin adapter consumes almost none of that precious distance, allowing you to fit more accessories like filter wheels and off-axis guiders into your imaging train without being unable to reach focus.
Can I use this Baader adapter to attach a DSLR to my Celestron 8" SCT?
Not directly. This adapter has a male 2" SCT thread and a female T-2 thread, so it does not thread onto the male 2" rear cell of an SCT. It puts a male 2" SCT thread on a male T-2 part. This creates a secure, all-threaded connection for prime-focus astrophotography.
Will this adapter work with an off-axis guider (OAG) in my SCT imaging train?
Only where the threads match: the adapter's female T-2 side screws onto a male T-2 thread, and its male 2" SCT side takes a female 2" SCT thread. It does not thread onto an SCT rear cell. Where it fits, its 1 mm optical length leaves the most back focus for the OAG body and the camera.
What accessories can I connect using this Baader adapter?
Its female T-2 side screws onto any part that has a male T-2 (M42x0.75) thread, and its male 2" SCT side then takes accessories with a female 2" SCT thread. T-2 parts this applies to include:
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Astrophotography cameras, only through a part with a male T-2 thread (camera T-2 threads are normally female).
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DSLR T-Rings, only through a part with a male T-2 thread (standard T-Rings have a female T-2 thread).
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T-2 filter wheels or manual filter drawers.
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T-2 off-axis guiders (OAGs).
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T-2 extension tubes for achieving precise spacing.
Is the 2" SCT thread on this adapter the same as a 2" filter thread?
No, and this is a critical distinction. This adapter uses the coarse 2" SCT thread (2"-24 TPI) found on the rear cell of most Celestron and Meade SCTs. It is not compatible with the fine M48x0.75 thread used for 2" astronomy filters.
