cant focus on anything beyond the moon and cross in the middle of image celestron powerseeker 127EQ

[chris pfleger]

hi all.... completely new to this. I get clear images of the moon, clear terrestrial images and none with obstructions.

 

however I have tried to focus on Jupiter. it comes out as a funny blurry bit of light and has a cross with a circular middle. this cross what is in front of the telescope holding one of the mirrors in place. what am I doing wrong? or is there something wrong with the scope?

20190629_090445.heic

Edited June 29, 2019 by chris pfleger
upload of picture

[knobby]

Sounds like you need more inward or outward focus ... can you try pulling the eyepeice out a bit as a test ?

[chris pfleger]

will try tonight... seems odd though

[John]

The cross is the shadow of the secondary holder and it's support vanes. This means that the scope is not in focus. You will need to adjust the focus inwards or outwards until the cross disappears and the target object is clearly focussed. Your target will appear at it's smallest when the scope is at focus. Either side (inwards or outwards) of sharp focus it will appear to expand into a disk of light with the shadow of the secondary holder showing against it when well out of focus.

 

[chris pfleger]

thanks... I have used the focus knobs without avail... so I guess as suggested above by knobby I will try by moving the eye pieces further out manually

[John]

28 minutes ago, chris pfleger said:

thanks... I have used the focus knobs without avail... so I guess as suggested above by knobby I will try by moving the eye pieces further out manually

If the focus knobs are moving the focus tube (the tube that the eyepiece is in) in and out then that should work. If you can get the moon in sharp focus (ie: craters, mountains etc showing crisply), you should be able to get planets and stars in sharp focus because the focus adjustment needed is only small - a 1/4 turn of the focuser knob or somthing like that.

Use low power eyepieces (eg: 25mm, 20mm focal length) rather than high powers to ge the hang of it.

[chris pfleger]

I'm using a 4mm and 20mm.

[Gfamily]

If you can focus on the moon, then you will use exactly the same focus position on Jupiter. 

However, if you're in UK, you may struggle with Jupiter at the moment - it's really low in the sky and the hot weather may well be causing a lot of thermals that will disrupt the image.

A friend at last night's astro club meeting said he wasn't able to get Jupiter focused because of the above.

If you're seeing the shadow of the secondary and the vanes, then you've gone way out of focus and need to go the other way. 

[John]

10 minutes ago, chris pfleger said:

I'm using a 4mm and 20mm.

Go for the 20mm.

 

[chris pfleger]

that's the one I mostly use... but still have those issues. I will try moving them bit more manually in the mount. but otherwise I have no other idea as to what it could be.

 

thanks for the ideas

[Gfamily]

Like I said, there's no difference in focus between the moon and anything in the sky, the problem with Jupiter is a combination of its position and the weather.

[John]

I don't know where you were observing from but Jupiter focused sharply enough from here last night at 90x - 150x. Above that it softened though.

As said above though, if you can focus on the moon, the planets are very nearly in sharp focus as well without adjusting the focuser.

Remember that Jupiter is going to look pretty small in the eyepiece though - a lot of newbies get caught out by just how small even the largest planet in the solar system is when viewed with a small scope.

What scope are you using by the way ?

[happy-kat]

Given Jupiter's position you don't want to use the 4mm eyepiece that will I think be asking too much. Your telescope has a 1000mm focal length but is a much shorter tube so in effect is using a built in barlow so is giving x250 magnification which is too much but will be fine on the Moon on good observing conditions.

Enjoy your telescope there is much to see up there.

Edited June 29, 2019 by happy-kat

[barkis]

What scope have you got. Model and Make?  Focal length and objective diameter?
I would guess you have a Newtonian reflector, so most of the answers already given
are likely correct, in as much as  you cannot reach focus because the distance between the main mirror, and 
the secondary mirror is too long. Perhaps a lower profile Focuser would suffice to correct the difficulty you're having.
Otherwise, moving the main mirror further towards the secondary  is needed. That  could 
create another problem if the secondary is too small to catch the reflected light cone.
Ignore all tjhis If you don't have the type of telescope I refer too.
Your link may be the Info. on your telescope,  but  I can't open the file.
Ron.
 

 

[chris pfleger]

thank you all for your tips and advice.

I'm using the Celestron 21049 Powerseeker 127EQ Reflector Telescope

I tried moving the 20mm eye piece further out... and that did work. however although I saw a round glowing object with a couple other smaller ones, that's all I saw. I have a pair of binoculars that show me that much of Jupiter.

or am I aiming at something like a star hence the difficulties. however it is extremely bright.

I'm in the south of England at a campsite so not much light pollution.

 

[michael8554]

This is what Jupiter and its moons should look like with your telescope and a 20mm eyepiece, but currently it is near the horizon so will be more blurry than this simulation !

 

[barkis]

Does this scope not  have  an artificially induced focal length to compensate for the mirror being spherical, and not a parabola ?
This is usually achieved by placing a lens inside the focuser. 
Often this can make good collimating of the system  quite difficult, resulting in poor quality at higher magnifications.
Hope I'm wrong here. 
Ron.

 

Edited June 30, 2019 by barkis

[wookie1965]

Take a picture of your focuser if you can as I know the Skywatcher focuser's have a screw to hold focus so no matter whether you try focus one way or another it will still be the same.

This would need to be loosened off then the focuser will do its job.

Edited June 30, 2019 by wookie1965

[Cosmic Geoff]

Sorry to be discouraging, but I think the problem is a combination of excessive expectations, poor telescope quality and atmospheric conditions.  If focus is achievable on the Moon, it will also be achievable on Jupiter and reveal a small glowing blob as in  Michael8554's simulation. 

The view of Jupiter + moons is distinctive, and you cam focus on the moons, which should look like white dots in a small telescope (or with poor seeing and low altitude, wobbling white blobs).

We had a discussion a while ago on how much focusing on the Moon differed from focusing at infinity, and the conclusion was that the difference was too small to be detectable or significant.

[chris pfleger]

thanks again... yes I think my expectations were too high. I was hoping to see the bands etc ... but yes I saw a blurry jupiter and moons... just need to learn how to use it properly and set it up. my view finder is very tricky to align so adds to the difficulty.

 

 

[Geoff Lister]

4 hours ago, Cosmic Geoff said:

The view of Jupiter + moons is distinctive, and you cam focus on the moons, which should look like white dots in a small telescope (or with poor seeing and low altitude, wobbling white blobs).

I have found that, to get the best focus on Jupiter, particularly at its current low altitude, it is best to achieve a sharp (sometimes wobbly) focus on one or more of its moons, and then slew to centre the planet, without touching the focus. Just keep looking, for several minutes, and your brain will start to 'see' more features. It is often better to go for lower magnification to get a sharper image, and let your brain fill in the details.

Geoff

Edited June 30, 2019 by Geoff Lister
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