|
ColHut,
Everyone else has given you sound advice already in terms of limiting your magnification. Roger has also given you sound advice as to what that 4mm eyepiece is suitable for.
I will add my .02c worth.
While your Bushnell Northstar might beat-as-it-sweeps-as-it-cleans, I think and don't hold me to this, it uses the same Optical Tube Assembly as the Tasco 4.5"/f8 which is made by Synta in China. This has a SPHERICAL primary mirror, usually of FAIR quality. Regardless of whether it uses the Synta OTA it will have a spherical primary.
I will try not to get too technical. While at F8, the scope exceeds Raleigh's Criterion for parabolisation of a 4.5" mirror, really it comes up a bit short. Many experienced opticians believe Raleigh's Criterion to be about 25% conservative at this aperture, which means to push really high magnifications with a 4.5" scope it needs to be F10 or longer if the mirror is spherical, or it needs a parabolic mirror at F8. What does all this mean? Probably that regardless of how good the seeing is your best views will be at low to medium power. In other words under about 140X. The 675X advertised on the box? Breaks all the rules about buying a telescope. Never buy a telescope that's advertised as having a maximum magnification, it is always and I mean always, from a practical point of view, a load of cocky sh_t. In fact it usually implies by convention the contents of the box to contain a CBTT. (For those wondering CBTT = Christmas or Birthday TRASH Telescope)
Don't be disheartened. Get some slightly better eyepieces (the scope isn't worth eyepieces costing over $100 each) stay at low to medium power and you will get some really nice views.
CS-John B
|