From: Mark Gaffney <markgaffney@mac.com>

Date: May 1, 2008 2:09:22 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Jupiter..

Hi again Alan, I mean with the basic alt/azimuth 2 star alignment I was using on the 4 SE I lost Jupiter a number of times from the FOV of the camera. This complicated getting a stable exposure. I think my options were rather limited but I`ll try again next time and see if I can get a faster shutter speed. I guess there might be other options with Astro IIDC as well for adjusting the image. Mark.

On 02/05/2008, at 3:15 AM, Alan Friedman wrote:

Hi Mark - 

As Milton has said, there are many problems going to a shutter as long as a half second. I sometimes use a long shutter (133ms), but when I do I always focus using the fastest shutter that provides an on screen image - even if the gain must be pushed beyond what I would choose for capture. Slowing the shutter brings compromises the real-time advantage to imaging with a streaming camera - at .5 second, accurate focusing would be very difficult.

At the focal length I work at - 7.5 to 11 meters, I don't find the finder scope very helpful as a tool to locate the image on the chip. The three screws and crosshairs are not really capable of sub arc minute accuracy. I do use it to locate the image in the visual field, then center it carefully and hope my tracking is good enough to keep it in view as a swap the camera for the eyepiece.

best,

Alan

On May 1, 2008, at 12:06 PM, Mark Gaffney wrote:

Dear Perry, My brother suggested plastic tipped metal screws as being
the go he thought, because the plastic on! es are just so obviously 
flimsy. The finder probably needs something softer on it`s surface
than metal. I just haven`t been near a nuts and bolts or hardware shop
to look yet! Mark.
On 01/05/2008, at 11:14 PM, hpholcomb wrote:

> Mark,
>
> I find that I have to realign the 7X50 finder on my VMC200L
> catadioptric more frequently that I'd like to.
>
> To minimize realigning effort, I replaced the small thumbscrews and
> Allen-head setscrews with something similar to "Bob's Knobs". Got
> them at Lowe's. Turns out that the rear set of set screws needed more
> length anyway for easier adjustment. I'm not going back to the
> others!!
>
> Perry