Paracorr outward focus with camera

[codemonkey (Lee)]

I've got an older paracorr on the way that I intend to use with my ASI 1600. It's the PLA version with no tunable top.

I note that TeleVue state that the 15% barlow effect was added so as to push focus outward. I've looked up a lot of threads but they're all targeted at visual users with the tunable top.

So my question: Does anyone know how much further out the paracorr will push the focal plane? Just trying to determine whether I need to move my primary further down the tube. I can easily move the mirror down 30 or 60mm, just need to know whether it's necessary.

[astro744]

See message in the beginner equipment section regarding 31mm Nagler and focus. The OP didn't mention Paracorr but I thought I'd try both to see what effects there are on focuser travel. Then I found your post.

I think the tuneable top was, (maybe still is) available for the Paracorr you have so the base may be the same design. I'm not sure the effects on a camera but for visual with a 31mm Nagler and Paracorr tuneable top set to position 5, the extra in focus travel is approx. 6 - 7mm with Paracorr in place.

The note on the Tele Vue web site stating that the 1.15x magnifying factor was introduced to push out focus but this should not be taken as to push out past the position with no Paracorr but rather push out from a reference position of a Paracorr with no magnifying factor. This is to better allow usage of the Paracorr with most telescopes without modification. The 1.15x factor also flattens the field a little.

[peter_4059 (Peter)]

I'm using the universal Paracorr with my QSI. I use 55.3mm of spacing between the Paracorr and the CCD. The attached image shows where the draw tube sits on the SN10 when in focus.