Quote:
Originally Posted by morls
Hi,
I want to get 3 eyepieces for my 180 Mak (f15). I've decided on two, but not the middle focal length...
1. Panoptic 35mm - 77.1 magnification, 2.3mm exit pupil, 0.82deg TFOV
2. ?????????
3. Delos 10mm - 270.0 magnification, 0.67 exit pupil, 0.27deg TFOV
The 35mm Pan gives close to the widest TFOV (although one day I might get a 55mm plossl, giving a 0.98deg TFOV), while I think the 10mm would get more use than anything shorter (suburban Melbourne most of the time).
I'm just wondering what others might suggest as a useful mid-range focal length to complete the set?
Cheers
Stephen
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180mm f/15 is a long focal length:2700mm.
The issue is in getting anything with a large exit pupil or a general use eyepiece with around a 2mm exit pupil.
If confined to just 3 eyepieces, they would have been a 55mm Plössl, a 30-32mm widefield and a 18-19mm widefield.
Your 10mm is a nice step up in terms of magnification, but a bit high for a "general use" high power, where a slightly lower magnification would be desirable.
Since you have the 10mm, and a 35mm, I'd first add something in the 18-20mm range, then think about that 55mm Plössl.
A low power of 49x and a true field of 0.98° and a 3.7mm exit pupil would be more appropriate as a low power, widest-field eyepiece.
If, on the other hand, you have other scopes and this is just your lunar/planetary/double star telescope, then a 17-18mm eyepiece would be useful as a "middle power".
In general, I usually recommend 4 eyepieces with a scope like that:
low power 4-10x/inch (28-70x) or 39-96mm focal length eyepieces
medium power 10-20x/inch (70-140x) or 19-39mm eyepieces
High power 20-30x/inch (140-210x) or 13-19mm eyepieces
Extra high power 30-40x/inch (210-280x) or 10-13mm eyepieces
Depending on which eyepieces you chose, you might get by with 3 eyepieces and a barlow lens.