Old 01-09-2008, 11:00 PM
bmitchell82's Avatar
bmitchell82 (Brendan)
Newtonian power! Love it!

bmitchell82 is offline
Join Date: Jul 2008
Location: Mandurah
Posts: 2,597
slowly getting there but focus???

heres my latest attempt... weather conditions where less than favorable. dammn wind

question. I have used the hartmann mask to get bright stars perfectly set, but how do i get things like this in perfect focus?

Picture of 47 Tuc, at 13 second exposures and stacked in registax with 60 subs
Attached Thumbnails
Click for full-size image (47tuc-stax.gif)
64.8 KB47 views

Last edited by bmitchell82; 01-09-2008 at 11:02 PM. Reason: whats the picture of :D
Reply With Quote
Old 02-09-2008, 12:49 AM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 7,188
Another idea is to use a Ronchi grating on a flip mirror. Set the CCD to your "best" Hartmann focus and then put a Ronchi grating on the guide port of the flip mirror, adjust until you get the gray null image of a star and lock in place. If the focus is spot on, all you need to do the next time is set a bright star to null with the Ronchi, flip to the CCD and away you go!
If you find the focus is still "soft" adjust it slightly and note the view in the Ronchi ie three wide bands etc. When it's 100% then re-adjust the Ronchi screen ( without moving the focusser) back to a null. Then you have a great reference for the future....
Reply With Quote
Old 03-09-2008, 09:26 PM
jjjnettie's Avatar
jjjnettie (Jeanette)
Registered User

jjjnettie is offline
Join Date: Feb 2005
Location: Far Far Away
Posts: 16,726
With my Gstar I use "point and zoom" to achieve focus.
Put the mouse on a star to magnify it, and then adjust focus.
I get live view from my camera to the puter screen, I don't know if you can do that with your camera though.
There's a couple of different versions for free download here
Reply With Quote
Old 04-09-2008, 05:06 AM
montewilson's Avatar
montewilson (Monte)
Registered User

montewilson is offline
Join Date: Apr 2007
Location: Sydney
Posts: 374
I find I get good final focus by picking a star that is just on the verge of being too faint to see on the screen and getting it to come in and out of view. When in focus the star appears and when out , it simply dissapears. Its quite accurate.
Reply With Quote
Old 04-09-2008, 10:12 AM
bmitchell82's Avatar
bmitchell82 (Brendan)
Newtonian power! Love it!

bmitchell82 is offline
Join Date: Jul 2008
Location: Mandurah
Posts: 2,597
that sounds like a good one, for me at the moment. untill we get some better gear.!
Reply With Quote


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 07:34 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Celestron RASA
Star Adventurer
Lunatico Astronomical
Astronomy and Electronics Centre