Daz­zling deep skies

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et­ting amaz­ing images of ob­jects in deep space isn’t down to mag­ni­fi­ca­tion or ef­fec­tive fo­cal length: in fact, there are some very good rea­sons to start out at lower mag­ni­fi­ca­tions. It’s eas­ier to get sharp re­sults with lower-power tele­scopes, and they also usu­ally let in more light than high-pow­ered mod­els. The im­por­tant el­e­ments in suc­cess­ful shots are the qual­ity of the te­le­scope, the smooth­ness of the track­ing mount and ac­cu­rate align­ment. Here’s more on the four key ar­eas you need to con­sider… fig­ures: th­ese re­fer to the mag­ni­fi­ca­tion for view­ing with an eye­piece fit­ted, so you can ig­nore the fig­ures for pho­to­graphic pur­poses. To find out how a te­le­scope will work with your cam­era you’ll have to dig a lit­tle deeper into the spec­i­fi­ca­tions and find the fo­cal length. Some­times this is ex­pressed as a num­ber such as f/500, which looks like an aper­ture, but is ac­tu­ally the fo­cal length – just the same as the fo­cal length as a nor­mal lens.

The most im­por­tant fig­ure for astro-pho­tog­ra­phy, the ef­fec­tive aper­ture, isn’t al­ways clearly stated in the spec­i­fi­ca­tion. But all you need to do is di­vide the fo­cal length by the di­am­e­ter of the ob­jec­tive lens. For ex­am­ple, a te­le­scope with an 80mm di­am­e­ter and a fo­cal length of 600mm will have an aper­ture of f/10. strengths and weak­nesses. If you are just start­ing out in astro-pho­tog­ra­phy and want to use an SLR with a te­le­scope, the best op­tion is a re­frac­tor te­le­scope with ED or apochro­matic el­e­ments.

You’ll also need a mount to fix your cam­era to the scope. Th­ese vary ac­cord­ing to the man­u­fac­turer, but most de­signs re­place the eye­piece with a tube assem­bly, onto which you can screw an adapter called a T2 mount that en­ables you to at­tach your cam­era body.

Adapter and T2 mount

kit list: dep sky pho­tos You will need… Te­le­scope or long-tele­photo, wide-aper­ture lens A Ger­man equa­to­rial mount such as HEQ5 or EQ6

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