AstroDude42 The 1.25" to T2 tube can not completely get screwed in anymore.
Yeah, that happens when you use the ZWO T2 nosepiece. Unlike companies like Baader, ZWO's stuff are not really designed to mate well within the entire family -- it is almost like the left hand did not know what the right hand was doing.
However, the light would need to leak through many turns of the screw thread, and I doubt it would leak badly enough for 0.5 to 2 second type exposures. So, as long as you tape off the thru-holes (if your version still has thru-holes) on the T2-1.25" adapter (for the lens spanner) I think you will be OK.
Another way is to use an O-ring inside the 42mm camera flange.
But you probably also have a M48 to M42 adapter that came with one of your cameras, that leaves you an additional way to do it. That adapter should seat properly, and the outer diameter fits 2" eyepiece holders, and you can also extend with M48 tubes that does likewise.
I have been using 2" filters so far, both for my Borg 55FL (which can also take cheaper 52mm filters that are common in the photography world. And I also use a 2" filter with my Askar FRA230 guide scope.
By the way Olli, if you are using a sensor that is not so sensitive to near IR, I have also experimented with a Wratten #29 filter (deep red - see Wratten's spec sheets for their filter curves.) which are easily obtainable in the 1.25" mounting. And if that still blocks out too much light, just a simple red filter from an LRGB set with still be a bit better than wideband guiding; although with multiple star guiding, the extra benefit might be too small to even notice.
Multiple stars averages the variances of the centroids and as long as atmospheric turbulence affects each star independently, atmospheric turbulence has a very small affect on the result -- that is why we can use short exposures for guiding.
As it is, with a 685nm IR pass filter, I am just seeing an extra 10% reduction in RMS error -- not something you would spend an extra $100 on; it is really for people who like to experiment and learn about effects of atmospheric turbulence, etc. With multi-star centroids, the variance halves each time you double the stars. So the RMS (if error is sinusoidal) drops by a factor of 1.4 each time you double the amount of stars -- that has a huge impact on reducing atmospheric turbulence. With 8 stars, your measurement RMS error falls by a factor of almost 3, instead of 10%.
That said, the use for 2x2 binning should make up for a lot of loss of green and blue photons.
Chen
