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I'll begin this post by saying, I've searched every forum.  I've tried every tip.  And I'm hoping you beautiful people can provide some suggestions based on my specific issue.  Because, as my title states, I'm just about ready to give up.  Here's a bit of background before I list the many ways I've tried to resolve the issue.

I own a Celestron NextStar 8SE and a Canon Rebel T6.  After many nights of trying, I cannot get a clear image of planets, or even the moon.  I've given it plenty of time to reach thermal equilibrium each night (1-2 hours).  When viewing through the eyepiece, the image is an absolute blur.  When viewing from the camera, I get no image at all.

Here are the things I've tried on the telescope itself:

  • Focusing the telescope via the "Focus Knob"
  • Collimating the mirror via the 3 screws
  • Using a Duncan Mask to make collimation easier.
  • Focusing the telescope on an object much closer, getting a clear, sharp image through the eyepiece and the DSLR, then attempting to view a star.
  • Waiting for, and viewing during, a near-perfect clear night with very little atmospheric turbulence.

I live on the westcoast of the US.  So, the only objects I'm able to see clearly (with the naked eye) are the moon and Venus.  I cannot describe the level of disappointment and frustration I feel when I can't clearly view them from the scope.  Venus is as bright as ever, and I'm getting a blur.  I tried using the DSLR and the planet doesn't show up at all.  Just black skies.  My DSLR settings are as follows:

  • Manual Focus
  • Shutter Speed: Bulb
  • ISO: 1600

What am I missing?  I feel like I've tried everything and I just want to throw up my hands in defeat.

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Hi and welcome,

You are certain that your collimation is good ? So when pointing to a star and turning the focus knob left and right before and past focus you see concentric circles ?

The corrector plate is not dewed over ?

What eyepiece are you using ?

Is this a new telescope ?

I think the first thing should be to resolve the problem of not being able to use the telescope visually, after that we can look into the imaging.

 

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20 minutes ago, Miguel1983 said:

Hi and welcome,

You are certain that your collimation is good ? So when pointing to a star and turning the focus knob left and right before and past focus you see concentric circles ?

The corrector plate is not dewed over ?

What eyepiece are you using ?

Is this a new telescope ?

I think the first thing should be to resolve the problem of not being able to use the telescope visually, after that we can look into the imaging.

 

Well, I'm not certain the collimation is as it should be.  Because no matter which way I turn the collimation screws, the blurriness doesn't change.  I see no fluctuation in the image quality at all.

The corrector plate wasn't dewed over.

I use the 25mm+ eyepiece.

Yes, the scope is new.  Are my expectations too high?  I mean, I've seen images of various planets amateurs post. Nice clear images.  But when I look through the eyepiece, I just see a blob.

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When you're looking at stars they should be pinpoints.

When you're looking at a deepsky target like the Andromeda galaxy, you see a smudge of light with a bright centre, this is normal, but the stars must be in focus.

Maybe check out a SCT collimation how-to on you tube to be certain you got this right, it's possible it's way off.

 

I would say, if you get your collimation in check and you still don't get a sharp visual of, say the moon, you may want to contact the dealer that sold the scope. 

 

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Can you achieve focus visually through the eyepiece, on a distant object, in the daytime?

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Posted (edited)

How do slightly out of focus star images look ?

When well collimated you should see several perfect concentric circles like this....

76ABF877-D490-4D9B-874A-85DFFF29ACD4.gif.a4dbd352ca3da866923f295c9c0f645a.gif

Edited by dweller25

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Sounds like it's out of collimation  as stated above.

Peter

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1 hour ago, LordSaladMan said:

............Well, I'm not certain the collimation is as it should be.  Because no matter which way I turn the collimation screws, the blurriness doesn't change.  I see no fluctuation in the image quality at all...........

As per the replies so far,  the first stage in checking/fixing is to just get something sharp visually with eyepieces, not the camera, which adds to the complication.

As Aram has just suggested, this can be done most easily in daylight.   If you can't get a really sharp image with a fairly low power eyepiece, then your collimation is the problem.  The collimation screws should never need more than half a turn, and usually less than that, from when the scope was first purchased.  There will be blurriness present until all three are exactly right, so they can't be adjusted by simply looking for a change in the image through the eyepiece.  You have to follow one of the techniques advised.

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As replies above, the first thing to do is to estalish that the collimation is correct. When I received my (used) C8SE the performance and the collimation were both awful, but I soon managed to correct it.

Then we come to other matters that will affect the visual performance.  The C8 is big enough to be  substantially affected by poor 'seeing'.    You will find plenty of pretty pictures taken through a C8 which bear little resemblance to what you see through the eyepiece. The main reason again is the 'seeing'.  The popular planetary imaging techniques involving making a video which is then processed to get rid of all the crud and bad seeing and preserve only the moments of excellent seeing in the final image.

In fact I moved to planetary imaging (with specialist cameras) to see the planetary detail my telescopes were capable of revealing.

Given the large focal range of a SCT it should be possible to get any camera in focus. Are you making the camera look through they eyepiece, or using the telescope as a telephoto lens?  Once you have a focus, it is a good idea to put the eyepiece back on and note how far (usually) you have to pull it out to get a sharp focus. That should give you a reference.

What finder are you using? Whatever finder came with the C8 may not be adquate for imaging, where you will want to locate your subject using the finder only. I recommend at a minimum a 9x50 RACI (right angle, corrected image) finder.

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start with pointing an object on the ground during day, large tower chimney, can you see things fine ?

be ware of the sun, never go near it

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On 05/03/2020 at 04:52, LordSaladMan said:

Here are the things I've tried on the telescope itself:

  • Focusing the telescope on an object much closer, getting a clear, sharp image through the eyepiece and the DSLR, then attempting to view a star.

Does this mean you WERE able to get a clear image, but couldn't view a star ?

If so, stars are very hard to see on a DSLR viewfinder or the Liveview screen if the scope is way out of focus, best done with Liveview on a computer screen.

If not, your collimation may well be way out, but I would ignore that for the moment and concentrate instead on FOCUS.

Daytime, with my Meade SCT and DSLR, I can focus on objects in my garden about 50 feet away, and see them clearly in the DSLR viewfinder.

So you should be able to focus on distant terrestrial objects during the day.

Be aware that the mirror focus on a SCT has many many turns of range, maybe 40 half turns with the wrist, then perversely there is only a tiny range that gives good focus.

Next try your luck on the moon, you should get a pretty good focused image in the DSLR viewfinder as the moon is bright and hard to miss !

Then stars and planet should also be in focus without any further adjustment.

But I found your whole post confusing, I can't tell if your scope is way out of of focus, or if your expectation of Venus in an eyepiece is way higher than reality.

Images will be somewhat blurry due to viewing through the atmosphere.

(Which is why planetary imaging software only stacks  the occasional sharp frames from video sequences)

Michael

 

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A new SCT rarely needs collimating. My advise is don’t (at least not yet).  Instead concentrate on better focusing the camera. 

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I had to recollimate my new C9.25 on first use.

Peter

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Posted (edited)
50 minutes ago, noah4x4 said:

A new SCT rarely needs collimating. My advise is don’t (at least not yet).  Instead concentrate on better focusing the camera. 

I think it’s too late for that as the OP has been tinkering 😩

I must have been unlucky as my C6 and C9.25 needed collimating, however my C8 was spot on 🙂

Edited by dweller25

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Personally I would forget the DSLR for the moment as that just introduces more uncertainty into the equation.

I suspect your collimation is probably way out if you have been making lots of adjustments, don't could take a while to get it back into shape.

You may need to be more clear in your descriptions so we properly understand what is going on. Saying it is a complete blurr doesn't give much info. Get the Moon centred in the eyepiece with either the limb or terminator in view, then run through the full range of focus adjustment. Does it improve to a best point then get worse again, or not change? Can you see any lunar craters or detail at it's best?

Assuming you can get it to a best point on the Moon, what do you see if you centre on a bright star?

Finally, if you put your scope horizontally and stand about 3 or 4 meters in front of it, centring your eye on the secondary holder, do you see concentric reflections or are they offset? I suspect they will be offset, so you should adjust using the secondary screws until they are concentric. Then do a star test and refine it further.

The strange thing is that even with the collimation a little out, you should be able to see something. I assume you are using a diagonal? Which sort?

Some photos of your setup may help too. 

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Posted (edited)

Hi

I read no mention of a diagonal except for the last post Stu's above, without a diagonal you will not reach infinity focus i.e. stars.

8SE > diagonal > eyepiece

or

8SE > extension > camera

Also is the finder scope aligned with the telescope, you could tweak this during the day on a very distant aerial or tree (not the sun)

Edited by happy-kat

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Do you wear spectacles, they can affect the focusing results.
if you normally suffer from poor distance vision without wearing spectacles,
then you need to focus wearing your glasses, This can be a discomfort, but necessary.
Ron.

 

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On 05/03/2020 at 05:52, LordSaladMan said:

I've searched every forum

Hi

Sorry you're having trouble.

Easy fix? My guess would be that within 5 minutes of arriving at your local astro society meeting with said hardware, the group's celestron expert -there always is one- will have everything sorted out for you. In the -very- unlikely event he can't, he'll know someone who can.

Cheers, don't give up and HTH.

 

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58 minutes ago, happy-kat said:

without a diagonal you will not reach infinity focus i.e. stars.

SCTs have a large focus range, accommodating everything from an eyepiece in the visual back, or via a diagonal, up to long camera, OAG, and filterwheel setups. 

We still haven't established whether he can achieve focus but it's poor due to collimation or atmospherics, or whether he has been unable to find focus. 

Michael 

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4 minutes ago, michael8554 said:

We still haven't established whether he can achieve focus but it's poor due to collimation or atmospherics, or whether he has been unable to find focus. 

Michael 

Agreed! That's what I was trying to establish.

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