Return to the Cloudy Nights Telescope Reviews home page


The long-awaited conversion to CN 3.0 is in progress. Please see this thread for important information.

See update on outage timing here.

Astrophotography and Sketching >> Solar System Imaging & Processing

Kokatha man
Postmaster
*****

Reged: 09/13/09

Loc: "cooker-ta man" downunda...
Re: Jupiter.....the "soft" approach!
      12/04/12 08:42 AM

Quote:

looks interesting
if it's give (only)1.25x wouldn't be a extension tube work on a sct optics for the same result? I forget the "true" F? for the given BFL of a C14 but perhaps a slider can be made to experiment for a small mods of the FL. It may alter the spherical correction of the system tho... so is the Barlow if it's not used with a designed distance me think.
Mick




Not sure I quite understand what you're saying Mick - an extension tube on the end of the scope itself as I understand your comment wouldn't achieve anything except make me have to throw the focal point back by bringing the primary closer to the secondary.....I understand about SA when shifting primary-secondary distance (as in extending the focus out from the barlow) but I've never thought about whether bringing the 2 mirrors closer actually effectively lengthens the native f/l..?

My inderstanding of optics most definitely isn't world-class but I suppose the secondary is actually a "barlow" of sorts...

***stopped typing at this point to do some research (thanks for that!) and "yes" changing their relative distance does change the effective f/l.....I seem to remember however that nearer together is worse in some respects for SA and other distortions.....and perhaps the barlow isn't creating as much distortion when the image plane is nearer as opposed to further out from it.....

At any rate in the end I'm a practical person and if I don't see any obvious effects (and I don't) then I'm happy to go the way I have...

But thanks for your comments Mick - food for thought...it'd be interesting to experiment as see what sort of scales can be achieved the way you suggest, and I'll probably do so when I find the time..!

ps: I use an i7 quad-core laptop in the field but I really don't know/think if that sort of "performer" is necessary for the ASI120MM.....but not having any specific knowledge/advice I refrained from responding to your thread question.

Post Extras Print Post   Remind Me!     Notify Moderator

Entire thread
Subject Posted by Posted on
* Jupiter.....the "soft" approach! Kokatha man 12/04/12 07:04 AM
. * Re: Jupiter.....the "soft" approach! Kokatha man   12/04/12 07:05 AM
. * Re: Jupiter.....the "soft" approach! Kokatha man   12/04/12 07:13 AM
. * Re: Jupiter.....the "soft" approach! Space99   12/04/12 07:56 AM
. * Re: Jupiter.....the "soft" approach! Kokatha man   12/04/12 08:42 AM
. * Re: Jupiter.....the "soft" approach! Daniel Chang   12/04/12 09:38 AM
. * Re: Jupiter.....the "soft" approach! RedLionNJ   12/04/12 10:22 AM
. * Re: Jupiter.....the "soft" approach! Space99   12/04/12 05:44 PM
. * Re: Jupiter.....the "soft" approach! Kokatha man   12/04/12 07:44 PM

Extra information
3 registered and 8 anonymous users are browsing this forum.

Moderator:  TG, Starman81, bilgebay, WOBentley 



Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled

Rating:
Thread views: 512


Jump to

CN Forums Home



Cloudy Nights Sponsor: Astronomics