▁as ▁Alb ire o ▁in ▁the ▁const ell ation ▁C yg n us . ▁ ▁A ▁number ▁of ▁solar ▁system ▁objects ▁that ▁are ▁mostly ▁to ▁completely ▁invisible ▁to ▁the ▁human ▁eye ▁are ▁reason ably ▁detect able ▁with ▁medium - size ▁bin oc ular s , ▁including ▁larger ▁cr aters ▁on ▁the ▁Moon ; ▁the ▁dim ▁outer ▁plan ets ▁U ran us ▁and ▁Ne pt une ; ▁the ▁inner ▁" min or ▁plan ets " ▁Cer es , ▁V esta ▁and ▁P allas ; ▁Sat urn ' s ▁largest ▁moon ▁T itan ; ▁and ▁the ▁Gal ile an ▁mo ons ▁of ▁Jup iter . ▁Although ▁visible ▁una ided ▁in ▁poll ution - free ▁sk ies , ▁U ran us ▁and ▁V esta ▁require ▁bin oc ular s ▁for ▁easy ▁detection . ▁ 1 0 × 5 0 ▁bin oc ular s ▁are ▁limited ▁to ▁an ▁apparent ▁magnitude ▁of ▁+ 9 . 5 ▁to ▁+ 1 1 ▁depending ▁on ▁sky ▁conditions ▁and ▁observer ▁experience . ▁Ast ero ids ▁like ▁Inter am nia , ▁Dav ida , ▁Europa ▁and , ▁unless ▁under ▁exception al ▁conditions ▁H yg ie a , ▁are ▁too ▁faint ▁to ▁be ▁seen ▁with ▁commonly ▁sold ▁bin oc ular s . ▁Like wise ▁too ▁faint ▁to ▁be ▁seen ▁with ▁most ▁bin oc ular s ▁are ▁the ▁planet ary ▁mo ons ▁except ▁the ▁Gal ile ans ▁and ▁T itan , ▁and ▁the ▁d war f ▁plan ets ▁Pl uto ▁and ▁Er is . ▁Other ▁difficult ▁bin oc ular ▁targets ▁include ▁the ▁phases ▁of ▁Ven