Scan around the field of view to stop your brain from mis­tak­ing dim tar­gets as ‘noise’

Sky at Night Magazine - - DEEP-SKY TECHNIQUES -

WHEN YOUR FULLY dark-adapted eyes are work­ing in very low light you will prob­a­bly no­tice lots of ran­dom flashes, sparkles and other gen­eral back­ground noise. If you then stare fixedly through the eye­piece, even us­ing averted vi­sion, any low-con­trast ob­ject will fade from view. This is be­cause the eye and brain will just treat the ob­ject as part of this back­ground noise. Scan your eye around the field, how­ever, and you stand a much bet­ter chance spot­ting your tar­get. When the retina is ex­posed to a dim, low-con­trast pat­tern that is mov­ing, the brain recog­nises it as some­thing real rather than back­ground noise.

To de­tect a faint galaxy some­where in the eye­piece, al­low your eye to nat­u­rally scan around the field of view at ran­dom. As well as cre­at­ing some move­ment of the ob­ject on the retina, the im­age will oc­ca­sion­ally land on the retina’s more light-sen­si­tive pe­riph­eral parts, mak­ing the galaxy briefly vis­i­ble.

Even with the eye scan­ning around the field, the brain tends to ig­nore spread-out ar­eas with a low-con­trast gra­di­ent. If th­ese ar­eas are moved rel­a­tive to the darker edges of the eye­piece field, how­ever, they then be­come much eas­ier to see. Try us­ing small back and forth move­ments of the tele­scope or re­peat­edly tap the side of the eye­piece and see the dif­fer­ence it makes.

If scan­ning the eye around the field doesn’t help, try tiny move­ments of the tele­scope

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