Go Back   IceInSpace > Equipment > Astrophotography and Imaging Equipment and Discussions
Register FAQ Calendar Today's Posts Search

Reply
 
Thread Tools Rate Thread
  #1  
Old 17-08-2014, 08:05 PM
Spookyer's Avatar
Spookyer (Brett)
Brett P

Spookyer is offline
 
Join Date: Jun 2013
Location: Dayboro
Posts: 580
Shooting wide field, not getting much signal

I have put a 70-200mm f4 camera lens on my STT8300 for the first time and I am shooting Rho Ophiuchi at 70mm. Even with a 10min sub I am getting very little nebulosity on the Lum and now the Red filters, can see the stars fine but can barely see M4. Can only just tell it is a cluster.

Am I doing something wrong?

Brett
Reply With Quote
  #2  
Old 18-08-2014, 01:46 AM
MrB's Avatar
MrB (Simon)
Old Man Yells at Cloud

MrB is offline
 
Join Date: Jan 2007
Location: Rockingham WA
Posts: 3,435
Strange. If it's an AF lens(doesn't have the aperture ring that manual lenses have), have you checked it's not stopped down to f16 or something stupid*?
I'm pretty sure Canon's are wide open when there's no power on them, the few I have are anyway, but different brands may behave differently(yours is a Nikon?) worth checking anyway.

Edit: *stupid f-ratio, not you stupid

Last edited by MrB; 18-08-2014 at 10:55 AM.
Reply With Quote
  #3  
Old 18-08-2014, 07:11 AM
Octane's Avatar
Octane (Humayun)
IIS Member #671

Octane is offline
 
Join Date: Dec 2005
Location: Canberra
Posts: 11,159
Yeah, most likely your lens is stopped down.

Are you getting diffraction spikes on the brights stars, such as Antares? That would be a giveaway.

On Canon lenses, if you wish to stop them down (they're natively wide open, as Simon wrote), you close down to the desired aperture, press the depth-of-field preview button, then, take the lens off the camera. It will then be stuck at whatever aperture was chosen.

It's perfectly safe to do it on Canon lenses, but, I don't know anything about Nikon.

H
Reply With Quote
  #4  
Old 18-08-2014, 07:35 AM
multiweb's Avatar
multiweb (Marc)
ze frogginator

multiweb is offline
 
Join Date: Oct 2007
Location: Sydney
Posts: 22,071
I had that same issue first time I did widefields with a lens. The lens iris was closed.
Reply With Quote
  #5  
Old 19-08-2014, 05:52 AM
Spookyer's Avatar
Spookyer (Brett)
Brett P

Spookyer is offline
 
Join Date: Jun 2013
Location: Dayboro
Posts: 580
I had considered that but the lens iris should be wide open except when you actually take a shot. So when I took it off my D4 the lens should have been wide open. Nothing should have changed between then and sticking on the CCD but I will check as it would explain the results.

Brett
Reply With Quote
  #6  
Old 19-08-2014, 06:00 PM
Spookyer's Avatar
Spookyer (Brett)
Brett P

Spookyer is offline
 
Join Date: Jun 2013
Location: Dayboro
Posts: 580
Okay, after some research I see my assumption was wrong. All of the newer nikon afs lenses have a spring that closes the aperture down when you take them off the camera. Now I have to find a way of opening them up when mounting on the CCD.

Nothing is ever easy.

Any nikon lens shooters out there?

How are you getting over the aperture issue when using them with a CCD camera?

Brett
Reply With Quote
  #7  
Old 19-08-2014, 06:12 PM
Peter.M's Avatar
Peter.M
Registered User

Peter.M is offline
 
Join Date: Sep 2011
Location: Adelaide
Posts: 954
Found this online, I have however never attempted it.

"Nikon G lenses physically needs the aperture feeler to be holing it in place to stay open. Look for a tab sticking out at the rear of your lens; it should be in a slot and it slides about inch or so. Locate it and move it with your finger check to see if it controls the aperture blades, if so you could lock the aperture at any setting by inserting a small slim made of folded paper or a piece of business card or anything similar that will snugly fit in. Remember it should not be loose so that it slides off and not too tight so that it damages the lens."
Reply With Quote
  #8  
Old 19-08-2014, 06:15 PM
Peter.M's Avatar
Peter.M
Registered User

Peter.M is offline
 
Join Date: Sep 2011
Location: Adelaide
Posts: 954
So I have a nikon lens near me with one of these spring loaded latches on it for the aperture. I dont think it would be too hard to get it to stay open for the STT.
Reply With Quote
  #9  
Old 19-08-2014, 09:35 PM
Spookyer's Avatar
Spookyer (Brett)
Brett P

Spookyer is offline
 
Join Date: Jun 2013
Location: Dayboro
Posts: 580
Thanks Peter, I will look into that.

Brett
Reply With Quote
  #10  
Old 20-08-2014, 10:02 AM
ZeroID's Avatar
ZeroID (Brent)
Lost in Space ....

ZeroID is offline
 
Join Date: May 2010
Location: Auckland, NZ
Posts: 4,949
KM lenses are the same, closed is 'normal'.
Reply With Quote
  #11  
Old 20-08-2014, 10:51 AM
PeterEde (Peter)
Prince Planet

PeterEde is offline
 
Join Date: May 2013
Location: Albert Park, Adelaide
Posts: 691
Another reason to go Canon
Reply With Quote
  #12  
Old 20-08-2014, 01:39 PM
ZeroID's Avatar
ZeroID (Brent)
Lost in Space ....

ZeroID is offline
 
Join Date: May 2010
Location: Auckland, NZ
Posts: 4,949
Quote:
Originally Posted by PeterEde View Post
Another reason to go Canon
Nyah !!! I get 12 fps @ 24 megapixels, brill for motorsports

I would like Live View though, I have considered buying a Canon just for that reason. But I resisted !!!
Reply With Quote
  #13  
Old 20-08-2014, 01:57 PM
PeterEde (Peter)
Prince Planet

PeterEde is offline
 
Join Date: May 2013
Location: Albert Park, Adelaide
Posts: 691
I use live view to focus at 10x
Can't imagine focusing through a viewfinder now
Reply With Quote
  #14  
Old 23-08-2014, 04:05 PM
Spookyer's Avatar
Spookyer (Brett)
Brett P

Spookyer is offline
 
Join Date: Jun 2013
Location: Dayboro
Posts: 580
I have cut a little piece of plastic off the sprue of a plastic model kit to suit. I have inserted it into the gap created when you move the aperture lever open manually. Seems to stay in okay. I will give it a go if I ever see stars again.

Brett
Reply With Quote
Reply

Bookmarks


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 09:20 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement