The Sky Guide Chal­lenge

Do the Hub­ble Deep Space Field-lite.

Sky at Night Magazine - - CONTENTS -

The Hub­ble Deep Field (HDF) is an amaz­ing im­age which brought home how in­cred­i­ble our Uni­verse re­ally is. It con­sisted of 342 sep­a­rate ex­po­sures taken by the Hub­ble Space Tele­scope (HST) over 18-28 De­cem­ber 1995. The com­bined re­sult pro­duced an un­prece­dented look into deep­est space. The tar­get area was a rather bland sec­tion of Ursa Ma­jor ap­prox­i­mately one 24-mil­lionth

the area of the en­tire sky. De­spite mea­sur­ing just 2.6 ar­cmin­utes across, around 3,000 dis­tant gal­ax­ies fill the frame.

The orig­i­nal HDF tar­get area lies just north of the Plough as­ter­ism. As this is cur­rently well placed in the UK’s night sky, we thought try­ing to repli­cate the HDF would be a good chal­lenge. Okay, un­less you own your own space tele­scope, it’s not go­ing to hap­pen, but you should be able to record some of the brighter ob­jects vis­i­ble in the orig­i­nal im­age. This is best-suited to a CCD/tele­scope com­bi­na­tion but other com­bi­na­tions may work too. And it’s not lim­ited to large aper­tures ei­ther, so any setup should re­veal some­thing of the HDF.

The first is­sue is lo­cat­ing the cor­rect bit of sky. As it was specif­i­cally cho­sen be­cause it looked empty, you’ll need to em­ploy a bit of star hop­ping to get there. Use stars Alioth and Me­grez as your start­ing point. From there nav­i­gate to the two 6th mag­ni­tude stars we’ve la­belled A (HIP 62402) and B (HIP 61936, or 76 Ur­sae Ma­joris). Use these as shown to nav­i­gate to the cor­rect bit of sky.

The Hub­ble Deep Field cov­ers an area 2.6x2.6 ar­cmin­utes, roughly 1/12th the ap­par­ent di­am­e­ter of the Moon. A setup cov­er­ing an im­age area of 30 ar­cmin­utes or smaller is rec­om­mended and you’ll need good track­ing or prefer­ably au­to­gu­id­ing to avoid long ex­po­sure trail­ing. We sug­gest ex­po­sure times in ex­cess of 900 sec­onds.

As ever, ex­per­i­ment with your ex­po­sures to see what works best for you. Im­age reg­is­tra­tion and stack­ing will def­i­nitely help smooth out some of the noise that gets in the way and we rec­om­mend a full cal­i­bra­tion sweep of darks, flats and bias cor­rec­tion.

The orig­i­nal HDF re­vealed how vast our Uni­verse truly is. Your own ver­sion of the HDF will re­veal how much of that Uni­verse is avail­able for even mod­est equip­ment to im­age. Don’t for­get to send your re­sults in to our Hot­shots gallery (see page 28).

You won’t be able to match the glory of the orig­i­nal HDF with your equip­ment but you might be sur­prised how much you can cap­ture

Lo­cate the two stars la­belled A and B to help you fo­cus in on the cor­rect HDF area

The HDF field im­aged with a 4-inch re­frac­tor and CCD cam­era show­ing fea­tures down to at least mag. +22.25

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