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Keith,
Assuming your mirror focal length is 1200mm, your magnifications with that selection will be 48 (with the 25mm), 75 and 150 with barlow, 171 and 342 with barlow. Now 48 and 75, 150 and 171 are not that different and seeing is rarely good enough to get to 342.
If instead, you get a 13mm and 9mm, the magnifications will be 48, 92 and 184 with barlow, 133 and 266 with barlow. This spread is better and the 266 high power is more do-able.
Regards, Rob
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