As­tropho­tog­ra­phy

Mars and Venus in con­junc­tion

Sky at Night Magazine - - THE SKY GUIDE -

THE IN­NER PLAN­ETS Mer­cury, Venus and Mars are rel­a­tively fast movers against the fixed back­drop of the night sky. Un­like the more dis­tant mem­bers of the So­lar Sys­tem, th­ese rocky worlds tend to have more fre­quent en­coun­ters with other ob­jects. When two ob­jects ap­pear close to­gether in the sky, this is known as a con­junc­tion. This month we have a meet­ing be­tween Venus, Mars and – for two nights – a cres­cent Moon, pro­vid­ing a per­fect op­por­tu­nity to pho­to­graph some­thing rather spe­cial.

Watch­ing two or more bod­ies ap­par­ently come to­gether in the night sky can be mes­meris­ing. Venus and Mars will be best seen low in the west-south­west from 19-23 Fe­bru­ary, and they are a dis­tinc­tively mis­matched pair­ing: Venus is around mag. –4.0 at the time of clos­est ap­proach, while Mars is a far more mod­est mag. +1.3. This means that Venus will be 132 times brighter than Mars.

Pho­tograph­ing the pair against a dark­en­ing twi­light sky will pro­duce a shot with two star-like dots. This can be done quite sim­ply, us­ing a cam­era and a lens with a fo­cal length of at least 100mm at­tached to a fixed tri­pod. Use a re­mote shut­ter re­lease to take shots with­out wob­bling the cam­era, a mid-to high-ISO and a rel­a­tively short ex­po­sure.

It pays to be cre­ative with your com­po­si­tion. Plac­ing a fore­ground ob­ject in the view can help to make the fi­nal re­sult more in­ter­est­ing to the viewer. This doesn’t need to be com­pli­cated, and some­thing like a tree sil­hou­et­ted against a not-quite-dark twi­light sky can look amaz­ing. Sim­i­larly, if you’re lo­cated in a town or city, a shot with ev­ery­thing lit and car­ry­ing on as usual be­low the ce­les­tial meet­ing above can add dy­namism. The trick is to avoid hav­ing some­thing too bright in the fore­ground that will sim­ply over­ex­pose the shot.

An­other op­tion is to stop down the cam­era lens. In­ter­nally, this is per­formed by aper­ture blades re­duc­ing the size of the hole that lets light through to the sen­sor. The con­struc­tion of the blades means that typ­i­cally, the hole isn’t per­fectly cir­cu­lar but rather made up of very short straight edges de­signed to em­u­late a per­fect cir­cle. Through a stopped down lens, a longer ex­po­sure on a bright light source such as Venus can show a very pleas­ing and at­trac­tive star­burst diffrac­tion pat­tern.

Here, stop­ping down the lens will re­duce the amount of light that en­ters the cam­era. Con­se­quently, to get a de­cent re­sult the ex­po­sure time has to be in­creased. This is where a driven equa­to­rial mount comes in handy, be­cause a fixed tri­pod will re­sult in trail­ing.

If a fixed tri­pod mount is all that’s avail­able to you, an­other in­ter­est­ing tech­nique is to stop down the cam­era and set it at a low sen­si­tiv­ity. Us­ing a lock­able re­mote shut­ter to take a long ex­po­sure of the plan­ets set­ting will ren­der them as trails head­ing to­wards the hori­zon. If you sim­ply want a static dots-in-the-sky type shot, our nat­u­ral photo enhancer – the Moon – will be on hand to help out. On 20 and 21 Fe­bru­ary, the lovely sight of a thin wax­ing lu­nar cres­cent show­ing earthshine will pro­vide a su­perb ad­di­tion to the scene.

A well-cho­sen fore­ground ob­ject can add depth to oth­er­wise sparse con­junc­tion pho­to­graphs

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