Bresser AR90/500 guid­ing kit

An all-in-one so­lu­tion to keep­ing your tele­scope trained on its tar­gets

Sky at Night Magazine - - CONTENTS - WORDS: TIM JAR­DINE

D eep-sky astropho­tog­ra­phy is be­com­ing ever more pop­u­lar among am­a­teur as­tronomers and many ob­servers dip their toes into the hobby us­ing a cam­era on their tele­scope and mount. It soon be­comes ap­par­ent, though, that tak­ing stun­ning, long-ex­po­sure pho­to­graphs re­quires some ex­tra equip­ment and a process known as ‘auto-guid­ing’. Tak­ing that next step has been easier thanks to the in­tro­duc­tion of Bresser’s new AR90/500 guid­ing kit, which aims to pro­vide a sim­ple, ev­ery­thing-in-the-box so­lu­tion to auto-guid­ing.

In sim­ple terms, auto-guid­ing is a method of en­sur­ing that a tele­scope re­mains pointed pre­cisely at an ob­ject be­ing ob­served, fol­low­ing it as it moves across the sky. Even very ex­pen­sive mounts can ben­e­fit from au­to­matic guid­ance, as sev­eral fac­tors in­flu­ence how well a mount will hold steady on its tar­get and en­able you to take long-ex­po­sure pic­tures that aren’t spoiled by star trails.

The AR90/500 con­sists of a 90mm achro­matic tele­scope with a fo­cal length of 500mm, a 6x30 op­ti­cal fin­der-scope, a Bresser GPCMOS0200­0KPA colour guide cam­era, a 26mm Plössl eye­piece, a 1.25-inch di­ag­o­nal, a univer­sal clamp, a tube clamp, ca­bles, a soft bag and ToupSky imag­ing soft­ware.

The 90mm tele­scope is firmly at­tached to the main setup and acts as a sep­a­rate ‘guidescope’. The lit­tle cam­era on the guidescope is fo­cused on a star near your pho­to­graphic tar­get, and it re­lays in­for­ma­tion via a lap­top or PC to keep your mount locked onto your de­sired ob­ject.

Keep­ing things light

We were pleased to see, then, that the 90mm tele­scope in this kit is light­weight. In fact, the whole as­sem­bly only added around 2kg to our tele­scope and cam­era rig. In gen­eral, the less weight a mount has to carry, the more ac­cu­rate it will be.

Hav­ing de­cided to mount the AR90/500 on top of our setup, we used the sup­plied bolts and clamp, at­tached to our own rail, to hold the Vixen-style dove­tail in place. Al­though the guidescope was not per­fectly aligned with the main tele­scope, and there’s no method of ad­just­ing the align­ment once the clamp is in place, it was close enough for our pur­poses. Find­ing a rough fo­cus po­si­tion is made

easier by us­ing the kit’s ba­sic 26mm Plössl eye­piece, which we then swapped for the guide cam­era it­self. It would have been prefer­able if the cam­era could have been used straight through, but we found that it’s only pos­si­ble to fo­cus the guide cam­era if the in­cluded 1.25-inch di­ag­o­nal mir­ror is used. Setup was fairly quick be­cause of our ex­pe­ri­ence with auto-guid­ing, but new­com­ers may be frus­trated by the lack of use­ful in­struc­tions.

Hav­ing in­stalled the cam­era soft­ware from the ac­com­pa­ny­ing CD, we were pleased to see that the cam­era was im­me­di­ately recog­nised in PHD2, our pre­ferred auto-guid­ing soft­ware, al­though the cam­era is com­pat­i­ble with all ma­jor auto-guid­ing soft­ware pack­ages.

Ready to go, we slewed to our first tar­get, the Rosette Ne­bula near Orion. Right away we were pre­sented with a choice of stars to guide on, picked out by the sen­si­tive lit­tle cam­era. It’s worth men­tion­ing that each star had a slight halo, which we be­lieve is the re­sult of us­ing a colour cam­era on an achro­matic tele­scope. This does not af­fect the guid­ing soft­ware, though, and soon our first five-minute test ex­po­sure was un­der­way. When we checked the star shapes, they were tight and round. Thus em­bold­ened, we in­creased the ex­po­sure length to 10 min­utes, and then to 15 min­utes, and the AR90/500 per­formed its task ad­mirably. In fact, over suc­ces­sive ses­sions on a va­ri­ety of nights – and no mat­ter where in the sky our tar­get was – our imag­ing tele­scope was held ac­cu­rately on tar­get, al­low­ing us to get on with the real busi­ness at hand: deep-sky astropho­tog­ra­phy.

By bring­ing to­gether ev­ery­thing you need to take astropho­tog­ra­phy to the next level, the AR90/500 pro­vides a cost-ef­fec­tive, sim­ple an­swer to the ques­tion, “What do I need to start auto-guid­ing?”

A sin­gle, 15-minute ex­po­sure, taken us­ing the Bresser AR90/500 kit, 150/1,000mm apo, h-al­pha fil­ter and Atik 11000 cam­era. Note the crisp, round stars and ab­sence of any trail­ing

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