Celestron Advanced VX 22020 Bedienungsanleitung PDF herunterladen (Seite 3)

68 December 2014   

S&T Test Report

For prime-focus deep-sky imaging, a focal reducer is

highly desirable. The Edge reducer, which is optimized for

small imaging chips, almost doubles the size of a tele-

scope’s ﬁ eld and cuts required exposure times in half. With

my Canon DSLR, stars were sharp all across the frame.

Unguided Imaging

Since astrophotography was in my plan on a trip to the

Chieﬂ and Astronomy Village in Florida, I kept things

simple. I shot through the SCT and reducer with my

DSLR, but I didn’t guide any exposures.

I mounted my Canon D camera to the scope with

a standard prime-focus adapter threaded onto the Edge

Reducer, which replicates the normal SCT threads. The

only problem I ran into was balance. The VX’s single coun-

terweight was not heavy enough to balance the telescope

in right ascension with the camera onboard. Fortunately, I

had brought an additional -pound counterweight.

Because good tracking is critical for imaging, once

the Go To alignment was complete, I performed the VX’s

All-Star Polar Alignment procedure. After centering a star

I chose from the hand control’s database, I completed the

process by re-centering it again using the mount’s alti-

tude and azimuth adjusters rather than the hand control.

Preliminaries over, I sent the scope to M and began

ﬁ ring -second exposures. I shot twenty -second

subframes of the globular. My stars were not quite round

in all frames, but stacking these short exposures into a

ﬁ nished picture yielded pleasing images. What’s amazing

is that a beginner could have achieved similar results. I

didn’t do anything special; I just snapped away.

The Oﬀ -Axis Guider

If you want to go much beyond -second exposures,

you’ll need to guide the VX. Today, that’s done with an

autoguider camera that plugs into the VX’s autoguide

port. You could use a separate small telescope to provide

guide stars for the camera to monitor, but ﬂ exure between

the main scope and guide scope can cause trailed stars.

Enter the Celestron o -axis guider (OAG).

When I opened the box containing the guider, my

heart sank. There appeared to be a million adapter rings

The author imaged the Dumbbell Nebula (M27) through the Edge

800 setup. The picture is a stack of twenty 30-second unguided,

prime-focus exposures using the Edge f/7 focal-length reducer.

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