BORG 55FL F3.6 with Filter Box & IDAS Filters

This is the Series 80 standard focuser version. In addition to FTF sets, R&P focuser version is now commercially available as well. US price is $1,450.00

After using both focusers myself, I concluded –  if I don’t need a motor, R&P just good enough. Very smooth and precise. 1/10 reduction allowed me to fully control focusing manually. The cost is below half of FTF. So I highly recommend this set unless  you control the focuser from PC.


Sunrise Blue


Sunset Orange



BTW, I realized I didn’t use ASI 183MC for a while.  So I set a camera with 55. The sensor size is 1/2.7 of full frame.  Looks like it will be similar FOV in full frame at 540mm f.l. And both are quite similar number of pixels.

I originally bought this camera for small galaxies as a resolution killer. So generally this is the spring season camera for me. Anyway, since a camera doesn’t block IR, we have to consider where and how filter(s) is/are set in the optical train. BORG filter box – 7519 is a convenient tool. It allows to set up to 52mm filter. So large enough for full frame sensor camera as well.


Easy to swap filters shown above, depending on the targets and sky conditions. Also thanks for BORG’s smart mechanical designs. There are some other filter threads in optical train shown below. One for in front of reducer. Another is at inside 7522. These will be useful as a base filter location like a regular UV/IR blocking, if you don’t have to switch a filter. Also two-stacking filters take you to the new world, which gives you more fun for imaging even with OSC camera as well.


IDAS plans to release some new filters within a couple of months. Please stay tuned here. Those should be very attractive for you.








~ by tedishikawa on December 3, 2018.

One Response to “BORG 55FL F3.6 with Filter Box & IDAS Filters”

  1. You write ” since a camera doesn’t block IR, we have to consider where and how filter(s) is/are set in the optical train”.
    With my ASI1600 camera came an adapter ring that allows to place a 1,25″ filter within the M42 extension ring that sits closest to the camera. Maybe the best position to place the IR cut filter for small format cameras. Then you can use the other positions at the reducer for various other filters.

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