Re: (IAAC) Problems with Lumicon Sky Vector (and ASTRO)

At 01:01 AM 12/10/97 +0000, you wrote:
>At 17:34 09/12/97 -0500, you wrote:
>>firstly, what scope?
>A British made f4.4 20" Dobsonian with a rectangular section open tube. The
>tube is made from 4 right angle section aluminium struts from which the
>previous owner had cut the 4 previously existing diagonal running braces.
>Tube flexure could be a problem but optically in terms of image quality it
>is not noticeable.

>to exactly horizontal. A source of error could be that the vertical level in
>the spirit level is quite small. How much error can be tolerated in this

don't know

>The diagonal support is central in the tube to within a couple of mm but it
>is possible that the mechanical and optical axes are not lined up well
>enough. How can you check this?
>>are you using it alt-az?
>>thirdly.. practice on lower elevation objects ALWAYS first if you are using
>>it in alt-az mode, build up to the zenith last, as it holds the highest
>I will try that. I had been starting to observe near the zenith.

zenith is awful on dobs

>>Thanks!   -Todd
>Thanks for your kindness in helping

Nick , no problem. At your first opportunity, pick up the SKY COMMANDER
digital setting
circles - works better for DOBS. No vertical or horiz. alignment needed and
you can 
use polaris as your first (in fact it prompts you to) alignment star. This
hastens the process
by about 70%.

Still have trouble with 1 to 2 degree errors near the zenith. Very closely
though up to around 60-70 degrees above the horizon

Thanks!   -Todd

Todd Gross
Boston Meteorologist
homepage: www.weatherman.com