Go Back   IceInSpace > Equipment > Astrophotography and Imaging Equipment and Discussions

Reply
 
Thread Tools Rate Thread
  #1  
Old 25-09-2012, 02:44 PM
mbaddah (Mohammed)
Registered User

mbaddah is offline
 
Join Date: Aug 2007
Location: Sydney
Posts: 803
Will this method of polar alignment with telephoto lens work?

I've been doing a bit of reading on polar alignment for my astrotrac and was thinking would the following method work.

1. Align tripod true south and set tripod head 34deg (Sydney) longitude
2. Mount SLR onto tripod head, and take a 30 second exposure shot using something like a 50mm lens
3. Playback screenshot, and home in little more using longer telephoto lens then previous focal length (say 70mm). Take another screenshot.
4. Repeat steps #3 until you have a reasonable focal length (say ~200mm) with the SCP always appearing in the centre of the playback shot without it drifting to the side of the lcd playback screen.
5. Remove DSLR, attach astrotrac, ball head, remount astrotrac on ball head and away you go!

Does this make sense ? Or is it total gibberish ?
Reply With Quote
  #2  
Old 25-09-2012, 06:54 PM
seeker372011's Avatar
seeker372011 (Narayan)
6EQUJ5

seeker372011 is offline
 
Join Date: Oct 2004
Location: Sydney
Posts: 3,531
You won't be able to make out star trails at 30 secs with a 50 mm unfortunately and it is very difficult to pick out sigma pctans

You need to go longer I think

Also found it very difficult to align the astrotrac on the tripod so the camera is pointing south and aligned perfectly in two axes

Having said all that it or a slighly different approach that i used .. Which was to take longer images, identify the point around which stars are rotating and centre that point works well enough for aging at small focal lengths and short durations

Investing the time and drift aligning works better but then you may not always have the tome
Reply With Quote
  #3  
Old 25-09-2012, 09:36 PM
mbaddah (Mohammed)
Registered User

mbaddah is offline
 
Join Date: Aug 2007
Location: Sydney
Posts: 803
Quote:
Originally Posted by seeker372011 View Post
You won't be able to make out star trails at 30 secs with a 50 mm unfortunately and it is very difficult to pick out sigma pctans

You need to go longer I think

Also found it very difficult to align the astrotrac on the tripod so the camera is pointing south and aligned perfectly in two axes

Having said all that it or a slighly different approach that i used .. Which was to take longer images, identify the point around which stars are rotating and centre that point works well enough for aging at small focal lengths and short durations

Investing the time and drift aligning works better but then you may not always have the tome
So taking longer duration images should work out fine for smaller focal length shots?
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 04:04 PM.

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