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#1 Gindie

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Posted 15 May 2021 - 09:16 AM

Hi everyone

I am new to all of this so please excuse the stupid questions!

I recently purchased a Celestron Starsense Explorer DX 6”. I can’t seem to find much information about this, including on the Celestron website. Has it been discontinued?

When viewing Arcturus from a light polluted city setting with the 40mm eyepiece included with the scope, there is a large black hole visible in the centre of the star, which I gather means the image is unfocused. When I adjust the focus, the star becomes a tiny point of light and not much bigger than when viewed with the naked eye. Is this just due to the magnification available from the scope / eyepiece?

Would I get a bigger image with a Barlow / different eyepiece? If so, are there any that you would recommend?

Apologies if the answers to these questions are obvious, but as you will gather from the above I really have no idea what I am doing!
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#2 Couder

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Posted 15 May 2021 - 09:24 AM

A star (other than our own star, the Sun) will always appear as a point of light.


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#3 Dynan

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Posted 15 May 2021 - 09:25 AM

First, welcome to CN! welcome.gif Your source for astronomy related palliatives. smile.png

 

Stars will always remain a point of light...especially if you're focused well. Try other larger targets...the Moon, M31 Andromeda Galaxy, etc. You'll get good sized views.

 

The central black spot shows you are far from focus. But this will be useful in the future when you colllimate your scope (another can of worms you can look forward to :smile:)


Edited by Dynan, 15 May 2021 - 09:26 AM.

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#4 Alrakis

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Posted 15 May 2021 - 09:40 AM

Welcome to CN and amateur astronomy! The black spot is the shadow of the secondary mirror (the mirror under the plastic cap in the middle of the glass plate in the front of your scope). As others mentioned you want the stars to focus to a point. That is all stars are in a telescope. However, you can look for double stars and see many colors. A group of stars are star clusters or globular clusters. You should be able to see brighter galaxies, nebula, as well as the moon and the planets.

 

The only recommendations for eyepieces right now would be a 32mm plossl and a 2x Barlow. Your telescope should have come with a 10mm eyepiece for high powers. I would use the 40mm or 32mm for star clusters, galaxies, and most nebula. Reserve the 10mm for the moon, planets, and double stars.

 

Chris 



#5 Eye stein

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Posted 15 May 2021 - 10:02 AM

 All Stars are at such distances that they are to small to be seen...BUT

They are to bright to be ignored!!

Joe


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#6 Gindie

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Posted 15 May 2021 - 10:20 AM

Thank you, very helpful. Lots to learn!

Edited by Gindie, 15 May 2021 - 10:21 AM.

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#7 sevenofnine

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Posted 15 May 2021 - 10:57 AM

One thing that is very helpful is to get an astronomy guide book. After reading a few chapters, you will feel less lost under the night sky help.gif  A very good one is Terence Dickinson's "NightWatch." He explains all different kinds of astronomy gear and provides seasonal star charts so you can begin locating objects of interest. Good luck! waytogo.gif


Edited by sevenofnine, 15 May 2021 - 12:52 PM.

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#8 Sky Muse

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Posted 15 May 2021 - 06:06 PM

Thank you, very helpful. Lots to learn!

Yes, the stars are so remote that only our own star, the Sun, can be seen as a true, physical disk.  Then, Alpha Centauri, 4.37 light-years distant, is the closest star to the Earth, yet still too far away to present a disk.

 

However, if the magnification is high enough, oh, 150x or thereabouts, most any star will present an Airy-disk, if it's bright enough. 

 

This is a virtual drawing I made, from short-term memory, just after having observed Polaris through my 5" catadioptric-reflector...

 

Polaris - 081919c.jpg

 

Note that the main star, Polaris Aa, presents a physical disk of sorts, again, an Airy-disk, albeit illusory.  Encircling the disk are thin, razor-like rings, and known as diffraction-rings.  To the south of Polaris Aa is Polaris B, one of Aa's dimmer companion-stars; the other being Polaris Ab which is too close to Polaris Aa to be seen.  Hence, Polaris is a triple-star system. 

 

I entreat you to observe Polaris on occasion.  Let it become a fast-friend, and as it has become of my own.  One particularly nice thing about Polaris is that it does not move there in the northern part of the sky.  It stays put, the view of the star there in the eyepiece, seemingly forever.  If a telescope was trained onto Polaris for a hundred years, the star would still be there in the eyepiece's view after all of that time.

 

Then, observing a brighter, larger star, like Deneb, and just before it morphs into an Airy-disk, at a somewhat lower magnification, can be an eye-opener too. 



#9 EricSi

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Posted 16 May 2021 - 02:42 AM

As an example, Betelgeuse is a red giant star with a very large actual size that is fairly close (< 600 light years) to earth, so its apparent size is bigger than most. But it is still dozens of times less than one arcsecond, which is about the limit imposed by earth's atmosphere even on a good night.

 

Professional astronomers using sophisticated techniques like interferometry and adaptive optics have been able to produce a very blurry low-resolution image of Betelgeuse's surface, but that is far beyond what we mere mortal amateurs can do....



#10 phillip

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Posted 16 May 2021 - 05:06 AM

Polaris is a fun star target. It frequently gives me a clue of the current sky conditions. If image is small and tight, in for pleasant views. Please note it's fainter companion that rotates to different positions, is very close to edge of the North Star. Has a blue gray cast color for me, abit higher power eyepiece reveals it easily.

 

Suguest a 10mm eyepiece or lower number for medium powers as planets already rising in the morning southern sky, always a treat and easy objects for beginner as are bright for easy location. May need practice on the moon to make correct focus as you start into this amazing Hobby! 

 

Clear Sky! 


Edited by phillip, 16 May 2021 - 05:08 AM.


#11 Dave Mitsky

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Posted 16 May 2021 - 04:32 PM

Welcome to Cloudy Nights, Gindie.  You may some of the information on astronomy, amateur astronomy, and observing in my post (#22) at https://www.cloudyni...mers/?p=5184287 useful.  There are sections on various books, observing guides, stellar atlases, planispheres, planetarium programs, phone apps, deep-sky observing, binocular astronomy, and urban astronomy.


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#12 Gindie

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Posted 19 May 2021 - 06:13 PM

Thanks everyone. Managed to catch an in focus view of the moon tonight, which was great!
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