From: Milton Aupperle <milton@outcastsoft.com>

Date: July 4, 2008 7:47:40 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: IR/UV filter...

Hi Mark;

On 3-Jul-08, at 8:24 PM, Mark Gaffney wrote:

Hi Milton, seems shifting the camera/nosepiece inside the eyepiece

holder won`t work for trees in the sunlight through the 10". Too much

light for the camera without a filter perhaps?

Most likely yes, especially since sunlight has a lot of infrared light in it too.

I can bring the 20mm

eyepiece into focus on nearer objects this way though. Mark.

The puzzling thing to me is that you did shoot some lunar images previously, which seemed to be pretty close to focus. Or was that taken with a different Telescope than this one?

I believe your 10" is a newtonian, right?  If you put a bright star in the field of view you twist the focus knob back and forth, you can usually see the star go from larger diameter (out of focus larger FWHM/HFD values) to smaller diameter (smaller FWHM/HFD values) and if you continue twisting it then it once again becomes a large star again.

If your not seeing that sort of behavior, the 10" might not have enough travel distance on the focuser then, either in or out to bring it into focus.

HTH..

Milton Aupperle

On 03/07/2008, at 10:47 PM, Milton Aupperle wrote:

Hi Mark;

No it wouldn't cause that. It primarily blocks off infra red light

which causes color balance issues (mainly lunar / solar, but Planetary

too like Jupiter) and also improves sharpness as IR light comes into

focus at a different point than visible light.

Usually when you can't find objects it's because the finder and the

camera / scope are not pointing at the same place. The small field of

view at prime focus with most scopes allows for very tight tolerance

in alignment. After I remove the coverings on my scope, I usually have

to re-adjust the Finder scope so that the finder and camera point to

the same object. I usually do this right before dusk and site them in

on a dsitant terrestrial object.

HTH..

Milton Aupperle

--- In Astro_IIDC@yahoogroups.com, "Mark Gaffney" <markgaffney@...>

wrote:

Hi Milton & others,I`m wondering if the lack of the above filter on

my IS DBK 21A F04.AS

would be affecting my ability to acquire stars in the camera window

of Astro IIDC. I`ve tried a

couple of times with my NexStar 4SE (as it`s easier to set-up) but

haven`t had any success

with more difficult objects. I`ll have to have another go with

Jupiter as I acquired it 2-3

months ago although quite overexposed with little chance it seems of

adjustment. Now that

my Firewire port has luckily started working again I can devote some

funds to a Baader filter

by the end of the month! Mark.