In your 12.5" scope you should get 6, 90% of the time depending on conditions and elevation, sometimes you may only get 5. Elevation and transparancy are important factors in seeing all 6 using scopes in the 6" to 10" range. Usually in 4" and 5" scopes you will only get 5 and may if your lucky occasionally get the 6th (F star).
They are always tougher in a SCT. Due to the number of optical surfaces inherent in the design ie Corrector Plate, Primary, Secondary, Star Diagonal and also the size of the central obstruction you will not have the same light transmission as a Newtonian or a refractor. Not a great difference but definately down a couple of percent which can matter when your talking borderline objects.
All is not lost You just need to get things in your favour.
High Altitude (hence less air to look through)
Good transparency
The correct magnification is important. In your 10" scope somewhere between 120X and 180X should be the zone. Your 16mm Nagler T2 should be fine. I will help you in seeing them next time Orion is well placed and we are together, if the 16mm Nag isn't fine I will lend you my 20mm Pentax XW.
Always see 6 in my 12.5" f6 dob. When the seeing has been very ordinary I have had to put a bit of effort in to tease the "f" component out, but I never gone without seeing all 6. My 4" short tube achromat has shown me the "e" component on a few nights of good seeing, but never the "f".
Thanks for the replies gents. Just wondering what others saw. I see 6 easy with the 12.5" The achro usually shows me 5 but on very favourable nights 6.
I've seen 6 a couple of times, 5 more times, and 4 all the time. Seeing has to be fairly steady for me to get the "f" component. I'm sure the trap will be the subject of one of the summer MOC's
6 on a good night, with anything bigger than my 80mm. The 80 shows 5 and I have yet to see 6 with it. I reckon though that the Trap is seeing dependant, much like Antares.
You just need to get things in your favour.
