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Hi Matt
I haven’t done any side-by-side tests between the C9.25 and the M180, and since I acquired the M180, the seeing in Brisbane has not been as good as it was when I used the C9.25 to image Jupiter. So, based on more of a feeling than hard data, my impressions are as follows:
On double stars, the M180 is clearly superior to my C9.25. The M180 behaves more like a refractor in that it delivers pin point stellar images with nice diffraction rings and good background contrast, whereas my memories of the C9.25 seem to be filled with more bloated stars and a more greyish, smeared background.
On Jupiter, the C9.25 seems to produce “better” images. That is, the detail still looks nice and sharp at a greater image scale than if I tried to pump the M180 with Barlow’s to achieve the same image scale. So, the M180 simply loses out here in the light gathering department.
I am a little hesitant to commit the above in writing for fear of spooking you! The impressions are just that; a series of impressions and memories as I have never done a side-by-side shoot out. Interestingly enough, Robert, who sold me the M180, when asked about the C9.25 vs. M180 for hi-res planetary work, seemed to favour the C9.25 which is why he parted with the M180. Anyhow, the M250 is a huge light bucket compared to the M180 so image scale should be less of a problem and certainly the Tak mirrors are razor sharp.
When the seeing is poor, say 3 to 5/10, it affects the M180 as much as the C9.25 so there is no real advantage for either OTA under those conditions.
Personally, having now owned an M180, VC200L and C9.25, I would instantly choose the M250 over a 12inch SCT, but I am more of a refractor person rather than a DOB person, which certainly biases my decisions.
Cheers
Dennis
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