Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

Recommended Posts

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.

Share this post


Link to post
Share on other sites

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.

 

Share this post


Link to post
Share on other sites
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.

Share this post


Link to post
Share on other sites

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. 

 

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites
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

Share this post


Link to post
Share on other sites

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

Peter

Share this post


Link to post
Share on other sites
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.

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites
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

 

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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

Peter

Share this post


Link to post
Share on other sites
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

Share this post


Link to post
Share on other sites

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. 

Share this post


Link to post
Share on other sites
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

Share this post


Link to post
Share on other sites

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.

 

Share this post


Link to post
Share on other sites
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.

 

Share this post


Link to post
Share on other sites
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 

  • Like 1

Share this post


Link to post
Share on other sites
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.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Corpze
      So, I have been testing three different kind of lasers, each one is supposed to be the "best" in each category or what you want to call it, the hotech and HG is almost the same, but whit the difference in how you lock it down.
      The Catseye is very different in how it works.

      I made a Youtube video of my thoughts

      https://youtu.be/ERF33hNVieQ

      What do you think? which one do you use?

      Regards, Daniel


       

    • By Camalajs525
      I tried searching for some easy deep sky objects on the internet but I never got a staright answer. Could someone please name some easy targets that I could use tonight. Mostly in Canis Major or in Canis Minor if possible. The deep sky objects that I am trying to find are quite simple. That can be seen by binoculars. Thanks, any help would always be appreciated. 😀
    • By Deltox
      Hi all,
      I'm trying to get back into astronomy (had a Meade DS 2090 Mak when I was 10 but was too young to get into it) and I'm having a very hard time choosing a telescope.
      My main goal is to observe a bit of everything. Planets and the moon are great and I definitely would want to observe them, but my main focus would be DSO's. That being said, I would also like to have the possibility of doing some basic astrophotography afterwards. Not expecting to do 2 hours of long exposure and getting some insane images, but having a telescope (or rather a mount?) that can track would be nice to get some decent images. Basically, visual observation is a must, AP would be great but only basic, no need to get one JUST for that. I realize that visual observing and AP are 2 very different things, but my question is if it is possible to find something that is mainly used for VO and is somewhat capable (even if it's not great) to do AP with. Furthermore, a push to or goto would be fantastic as well since I'm not too familiar with the night sky. Is it really difficult to find DSOs yourself without reading and learning for hours and hours?
      My budget would be around 800 euros, that is everything included, telescope, mount, eyepieces etc... (If it's a little bit more than that that's fine as well).
      After hours of doubt and searching I thought the Orion Skyquest Xt8 Intelliscope would be good (push to) (around 750 euros), however being like most dobsonians, this one wouldn't track. This made me think :
      Should I rather look for a newtonian reflector with an EQ mount, or just give up my basic AP wish and go for a dobsonian that doesn't track? Some people have suggested to drop AP for now and go for the dob, is there a possibilty to upgrade later to make the dob work for AP, like putting it on an EQ mount, or would I have to buy a new telescope again?
      Any telescope, mount and added equipment like eyepieces and filter suggestions would be reaaaally appreciated, cause everything just feels overwhelming and I don't know what to look for anymore.
      Thanks in advance!!
    • By Camalajs525
      Since I am very new to this, I struggle a lot. Especially when observing planets and also recently deep sky objects. My telescope is an amateur telescope and its almost 11 years old (The telescope was re used a year ago). During summer of last year I took photos of Saturn,Jupiter and a month ago took photos of Venus and Mars. About 2 days ago I stumbled upon a new thing in the sky, (Unfortunately, I didn't take a picture). It definitely was in the Orion constellation  as I had observed Betelgeuse and the 3 stars that were close to each other. After a couple of minutes later I saw 2 stars next to each other and another two which were on top of the other star, surrounding these set of stars were a blue-ish and grey-ish colour at the same time. I had done some research and many people told me it was the trapezium cluster found in Orion. I honestly don't know. Any ideas? Thanks. 
    • By Camalajs525
      So I'm having some issues recently and have a lot of questions for the erecting eyepiece 1.5x. I want to know if they are useful, better, and i also want to know if they have a lot of detail in them. How do you use a erecting eyepiece? What is it for? When can i use it? Also my issue is when I try to use an erecting eyepiece on a star it is out of focus and cant seem to find the right focus.  yesterday I had tried on sirius but it just showed me a huge ball of light. Any help and tips will be appreciated.
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.