Star Adventure(r) #3 is an attempt to reduce the focal length of my Zenithstar 80IIED semi-APO refractor, native f6.8 using my Meade f3.3 focal reducer.
Backspacing is clearly way off, and there is an 'eye-wateringly' bad tilt issue in the optical train, perhaps not surprising given reliance on compression rings. I calculated the focal length of this set up, using astrometry to be 166 mm, comparable with the FOV I get with my Pentax 200mm zoom lens. Despite the obvious issues, the stars in the centre of the frame are very much sharper with these optics.
A different orientation with the additional lenses, the image comprises RGB data - unfortunately the session was cut short due to a software error during acquisition. Data were collected in ATP, pre-processed in Nebulosity v4, and, as with previous images, Revision A processed with a standard workflow in Startools v1.8, and Revision B (mouseover) in Nebulosity v4. I like the extra depth and saturation achieved in Startools, even if there is a little too much green, and it accentuates the backspace, and tilt issues mainly on the right side of the image.
On the plus side, I have been enjoying using astrometry to hunt down targets, using the plate-solving tools built into ATP, coupled with Han Klein's excellent
ASTAP and HNSKY planetarium software. So much easier than star hopping, or sing 'push to' with Dimitrios Kechagias'
PolarScope Align Pro App and my iPhone. Both excellent, inexpensive software.
Tonight is clear again... I will try my Meade f6.3 reducer to see if this provides an optimum balance of FOV and tracking accuracy, and will pay special attention to the stars...
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