#1  
Old 11-10-2014, 12:40 PM
astro.photo
Registered User

astro.photo is offline
 
Join Date: Oct 2014
Posts: 4
Astrophography Newbie

Hi All.

First off - great site. I have spent a bit of time reading trying to understand the basics and was lucky enough (I think) to pickup an old Australian Geographics 900x130 reflector telescope with EQ mount for a cheap price.

I am trying to take photos with a Canon DSLR but am running into a bit of a problem. I bought a Tmount kit for the camera as well as an adapter to mount the camera to the telescope but then I run into trouble. As i try to focus, the telescope focus hits the stop and wont retract any furthur. I have tried fitting a 3x Barlow to see if that works and it does to a certain degree but it magnifies too much.

So my question is, is there any way (other than buying a new telescope as funds are limited) to get the camera to focus?

Thanks in advance.
Reply With Quote
  #2  
Old 11-10-2014, 01:22 PM
raymo
Registered User

raymo is offline
 
Join Date: Sep 2011
Location: margaret river, western australia
Posts: 4,927
Many Newtonians suffer from this problem. First question is whether the
camera nearly focuses, or whether it obviously is quite a way off. Ideally,
you could post pics of your adaptor arrangement, because maybe you are doing something wrong, or there is another way to get your camera closer to the focuser. You can in the meantime use a 2x barlow of course.
Budget level 3x barlows are often optically very average. With many Newts that won't come close to focus, the only option is to modify the scope by moving the primary mirror further up inside the tube, but with others that come close, there are easier fixes.
Someone who is familiar with your particular scope will probably put you on the right track.
raymo

Last edited by raymo; 11-10-2014 at 01:25 PM. Reason: more text
Reply With Quote
  #3  
Old 11-10-2014, 01:39 PM
glend (Glen)
Registered User

glend is offline
 
Join Date: Jun 2013
Location: Lake Macquarie
Posts: 5,314
Cheapest option is to move the mirror up, you can try doing this by allowing it to rise on the collimation screws to the limit of the travel, if that's not enough you could get longer bolts and springs but I would discourage cutting the tube to shorten it.

I'd try cranking out the mirror first and see if that gets you to focus, but it will push the visual eye piece focus further out to the point where you may need an extension to reach EP focus.

You need to work out how much more travel range you think you will need to reach focus with the camera, that informs your next step.





Good luck

Last edited by glend; 11-10-2014 at 03:36 PM.
Reply With Quote
  #4  
Old 11-10-2014, 06:08 PM
Geoff45's Avatar
Geoff45 (Geoff)
PI rules

Geoff45 is offline
 
Join Date: Jul 2006
Location: Sydney
Posts: 2,407
So the first step is to determine exactly where the focal point is. Take out the eyepiece and point the scope at the moon. You should be able to focus it on a piece of cardboard held up to the drawtube. To get focus with your camera you need to be able to place the imaging centre at the point of focus that you have just determined, so as above, the position will guide you to the next step
Reply With Quote
  #5  
Old 11-10-2014, 07:04 PM
raymo
Registered User

raymo is offline
 
Join Date: Sep 2011
Location: margaret river, western australia
Posts: 4,927
We could be all jumping the gun here; his scope might well reach prime focus using the right adaptor setup. We need him to post a pic of his gear. Many newbie owners of Skywatcher Newts have problems because
they don't know how to use the supplied adaptors.
raymo
Reply With Quote
  #6  
Old 11-10-2014, 08:25 PM
RobF's Avatar
RobF (Rob)
Mostly harmless...

RobF is offline
 
Join Date: Jul 2008
Location: Brisbane, Australia
Posts: 5,491
It would definitely be helpful to see a pic of the focuser assembly and threading.
Reply With Quote
  #7  
Old 12-10-2014, 07:21 PM
astro.photo
Registered User

astro.photo is offline
 
Join Date: Oct 2014
Posts: 4
Hi All

Thanks for the responses..

Will take some pictures and post and hopefully that will answer a couple of the questions...

Cheers
Reply With Quote
  #8  
Old 12-10-2014, 07:45 PM
astro.photo
Registered User

astro.photo is offline
 
Join Date: Oct 2014
Posts: 4
Here are some photos - hope they help!

Click image for larger version

Name:	Telescope01.jpg
Views:	18
Size:	153.3 KB
ID:	171485
Click image for larger version

Name:	Telescope02.jpg
Views:	25
Size:	179.3 KB
ID:	171486
Click image for larger version

Name:	Telescope03.jpg
Views:	16
Size:	127.9 KB
ID:	171487

If you need anymore let me know...

Ta

AP
Reply With Quote
  #9  
Old 13-10-2014, 05:30 AM
ZeroID's Avatar
ZeroID (Brent)
Lost in Space ....

ZeroID is offline
 
Join Date: May 2010
Location: Auckland, NZ
Posts: 4,950
Have you tried a Barlow ?
The only realistic solution I see here is to move the primary up the tube. Probably about 25-30mm I'd guess, the CCD focal plane is well to the rear in the camera. Quite a way back from an EPs closest point.
Reply With Quote
  #10  
Old 13-10-2014, 08:03 PM
RobF's Avatar
RobF (Rob)
Mostly harmless...

RobF is offline
 
Join Date: Jul 2008
Location: Brisbane, Australia
Posts: 5,491
Yes, some models have a few tricks that can save precious centrimetres, but you're only choice there it would seem is moving the mirror up the tube or changing focuser. You probably won't find a focuser that will help under the price of the telescope, so that's probably no help.

As far as moving the primary, you may be able to put longer screws in if cutting the tube isn't your thing.

Its likely you are going to get quite severe vignetting with the relatively narrow focuser, and moving the primary will make that a little worse.


What sort of mount do you have? You may only want to do short pics of the moon and planets perhaps?
Reply With Quote
  #11  
Old 14-10-2014, 06:58 AM
Geoff45's Avatar
Geoff45 (Geoff)
PI rules

Geoff45 is offline
 
Join Date: Jul 2006
Location: Sydney
Posts: 2,407
We can all speculate here until the cows come home but until we know exactly where the prime focal point is it's just idle speculation.
Reply With Quote
  #12  
Old 14-10-2014, 10:36 AM
raymo
Registered User

raymo is offline
 
Join Date: Sep 2011
Location: margaret river, western australia
Posts: 4,927
Which is why I asked him if it nearly focuses, or is obviously way off, but
never got an answer on that.
raymo
Reply With Quote
  #13  
Old 14-10-2014, 07:13 PM
astro.photo
Registered User

astro.photo is offline
 
Join Date: Oct 2014
Posts: 4
Hi all....

I should remember to do two things:
1. Check my posts and
2. Answer the questions that have been asked !!

First off - thankyou to everybody who have responded!!!!

@raymo - the focus is almost there, I would think if I could turn the focus an extra 1/4-1/2 turn then it would be there.

@RobFo - I have got an equitorial mount and the photos I would like to take would be of the moon, Mars, Jupiter and Saturn (if I can get them). I would love to take some of the great starscapes that I see however I don't think I have the equipment to do it and unfortunately am saturated in light pollution to take long duration exposures. I have posted a photo of the assembly, would a better picture of the threads help?

@ghsmith45 - I will give it a go this weekend and report back!

I might give the screws on teh bottom a go - is there a recommended method that I should follow to minimize the possibility of error?

Thanks again for all your help..

AP
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 05:48 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
SkyWatcher Australia
Advertisement
Lunatico Astronomical
Advertisement
NexDome Observatories
Advertisement
Bintel
Advertisement
Celestron Australia
Advertisement
Meade Australia
Advertisement
OzScopes Authorised Dealer
Advertisement
Astronomy and Electronics Centre
Advertisement