Modified ETX-70 ED petzval

Hello world!

Huh? An ETX-70 ED Petzval?!

Yep. Ingredients: An ETX-70 OTA, a William Optics 66ED Petzval with a broken front lens, a GSO crayford style focuser + a lot of tinkering and voila:





From the WO 66ED I took the rear lens doublet which contains an ED lens (very likely FPL51) + the mounting bracket. The GSO focuser is from the 125mm achromat I gave up on. The ETX-70 OTA was removed from the mount. Only some cutting and driling was required, the GSO focuser exactly fits the ETX OTA. Cutting was required to reach focus. The WO rear lens doublet sits in the focuser (just as it was with the WO 66ED). To keep it there it is assembled in a baffling thingy I took from a Celestron focuser I had no other use for. Due to the wieght of the GSO focuser that is attched to the metal ETX-70 tube, the whole construction feels rock-solid.


Visually it is almost color free! Photographically there is color, more than with my Astro-Professional 102 ED refractor. It's about the same amount of color I had in my WO 66ED petzval. These are 30 seconds exposures (ISO 400):





Maybe future in it for my ideal grab-and-go astro snapshot astrograph ...