From: Mark Gaffney <markgaffney@mac.com>

Date: April 30, 2008 11:21:00 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Jupiter..


Dear Milton, I actually have the keyboard and mouse on a long usb cable ( or my bluetooth keyboard/mouse is perhaps useable) next to the monitor so I can perform adjustments in exposure. I do have the monitor perhaps slightly too far away inside the nearby garage at the moment for proper focusing. I get a good rough idea! That`s because I`ve been persuaded I need to keep as much as possible protected from sudden rain etc.!  The finder on the 4SE is a small laser dot job which gets me in the vicinity but I have to find Jupiter in the eyepiece before it`s anywhere near the camera`s FOV. The finderscope on the 10 inch needs adjustment every set-up and is one of the numerous things I have to do each time! (2X 3 star alignments, one before, one after polar alignment). I`m still waiting on a replacement plastic screw for the 10" finder which will have to come from Celestron in America and am making do with a metal screw of similar thread I found. I`m also finding with the 10 inch, adjustments with the HC are often in reverse of what you`d expect and it moves in arcs, not directly, as with the alt/azimuth alignment on the 4 inch.Often very confusing! I`ll try your suggestion of decreasing the exposure time next time (last time was a basic experiment!) though I seem to remember Jupiter disappeared altogether much below 533.33ms.That may be due to other factors ( like me juggling with focus, alignment and exposure!) It`d be great to see some detail in the images! Thanks, Mark.

On 01/05/2008, at 2:33 PM, Milton Aupperle wrote:

Hi Mark;


On 30-Apr-08, at 6:31 PM, Mark Gaffney wrote:

Hi everyone, Last night I got my first view of Jupiter coming back  

from my IS DBK 21A F04.AS to the screen. I`ve had troubles with  

focusing which has been solved pretty well by putting my old LCD  

monitor out near the focusing knob on the scope. I don`t have a lap- 

top which I know a lot of you have, so have had to use a long VGA  

cable. Jupiter didn`t come into view until I`d done some nudging back  

and forth with the hand control on the Celestron 4SE I was using and  

set the exposure to 533.33 ms. I must read up in the manual what this  

means exactly and any other advice! I didn`t manage to bring the  

"stripes" into view but was pleased I`d finally been able to find an  

object smaller than the moon.


Your 533.33 ms exposure time (ms is milliseconds, so 533.3 ms is 0.533 second exposures) is too long to see anything except the bright disk.


Using a long exposure like that is useful to get an object centered and focussed when your not sure how much your focus is out. Once you get it roughly in focus, you decrease the exposure time and brightness until you begin seeing details on the disk.


However 533.33 is way too long an exposure to see any details on the disk, especially jupiter. At prime focus (say 2,000 mm or less) with a C8, probably 33 ms (0.033 second) exposures is all you need and even that might be too much for a 10 inch scope.


Unfortunately, about the only way your going to get proper exposures and fine tune the focus at the same time is to lug the Mac and the VGA LCD outdoors beside your scope.


Lastly, one thing I like to do is adjust my finder scope so that it and the camera point at the same thing. So once you get Jupiter perfectly centered in camera field of view (FOV), adjust the finder scope so the cross hairs are right on it. Then the next time you go looking for a target, it will be likely be right in the cameras FOV.


Hope some of this helps..


Milton J. Aupperle

President

ASC - Aupperle Services and Contracting

Mac Software (Drivers, Components and Application) Specialist

#1005 - 815 14th Avenue. S.W.

Calgary Alberta T2R0N5

1-(403)-229-9456

milton@outcastsoft.com

www.outcastsoft.com