This summer has been mostly a bust for astronomy due to the huge number of wild fires and subsequent smoke. I was very reluctant to take the scopes out as there was so much ash in the air I feared damaging the optics. But that does not mean things have been stagnant. A friend in Japan contacted me to let me know he had found a very rare scope – a Takahashi FCT-125. I have never seen one, nor heard of anyone using one so it was a huge find.
Two nights back I decided to give it a try so I took the FC-125 off of the HGM-200 and mounted the FCT. Right out of the box, and with essentially no cool-down it was giving great images of the Moon. Very sharp and contrasty. I was actually shocked at how good the image was, though I do not know why. To check for color correction I ran the image in and out of both sides of focus – nothing! Obviously in-focus was totally color free. I also moved the image around the field of view to see if there was significant field curvature- nothing noticeable. What was noticeable was the incredibly shallow depth of focus – at f/5.6 you had to be dead on and the slightest movement of the focus knob meant the difference between in-focus and out of focus. But the big focuser on the FCT is smooth and precise and focusing was a cinch.
Saturn was just below the Moon so I pointed the FCT at it. The image scale was pretty small, but it was a nice image, far better than the 16” R-C at “Hopservatory” we visited a week ago. I tried all the eyepieces I had, but the shortest was a Pentax XW 5mm which ran at 140x. I did not have the HGM tracking which was a mistake. Next time!
Out of curiosity I changed scopes and spent some time with the FC-125 for comparison. The image scale of the longer focal length scope was more pleasing, but sharpness on the Moon was a push. Reaching focus was easier in the FC, but once reached you would be hard pressed to tell any difference. The FC is really well corrected for color - I racked the focuser in and out and could just tease a slight, and I mean slight, fringe of faint yellow/green on one side of focus and faint purple on the other. I had to work to see the colors they were so slight. No color at all in-focus. Nada.
The Moon looked great in everything I threw at it up to the 5mm XW at 200x. The 6mm Delos was very sharp, nearly as sharp as the Pentax . Turning to Saturn I was immediately struck by the sharpness of the image. It would be hard to say it was sharper than the FCT, but the image scale and ease of focusing certainly made it appear more detailed. Cloud belts on the globe, Cassini’s, etc were all clear as was Titan. Titan was also clear in the FCT so, again, a longer test with the mount drives on is in order.
Hercules was nicely placed so I swung the FC to M13. It never ceases to amaze me how the superior contrast of refractors seemed to allow them to perform above their actual aperture – M13 was wonderful! Dim, but clearly a ball of pinpoint start. It looked better than any 8” SCT I have ever seen M13 through. Great image!
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This post was modified on 9/30/2017 4:11 AM