From: Milton Aupperle <milton@outcastsoft.com>

Date: June 29, 2008 12:37:08 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Cables, adapters, and stuff

Hi Tim;

You can see "Flop" / "Shift" pretty easily when you changed declination / altitude by 30 degrees. Stars become unfocussed when your shooting at around 1 arc second per pixel with my C8.

My only solution is to go with the Off Axis Guider, which is the only way to get decent guiding. I've had erratic hit and miss performance when using a Guide Scope, some nights it's good, other nights you have a steady 1 arc second per 5 minute exposure time drift.

The other issue with Guide Scopes is field of view and the wider that is, the more likely you are going to pick up a Satellite Zipping through it and might have the guider try to chase that, especially when your guiding on a 8th / 9th mag star and a Mag 4 satellite rips through. There are options in Astro IIDC guiding to limit that sort of thing.

TTYL.

Milton Aupperle

On 29-Jun-08, at 11:52 AM, Tim wrote:

Milton:

I like the serial port hub idea.  Last night was the first time I

really put the focuser control option of Equinox Image through it's

paces instead of just running the robofocus software on the PC, and I

was rather impressed with it.

I also think you're right about the mirror flop in SCTs.  Since I'm

guiding with the 9.25", I have this problem around the zenith - which

is unfortunately where the least atmosphere is getting in my way.

Last night, I took two image sequences.  The first was of M13.  The

whole sequence was over before it crossed the meridian, though, and I

had no noticeable flexure or mirror movement (but I haven't processed

the images yet and they were only 5 minute exposures IIRC).  But for

the Dumbell, I shot 20 minute exposures, and when I was shooting the

green frame, the scope was crossing the meridian (around 2am, I think

- I used my cell phone as an alarm to take naps while imaging).  The

clear and red frames are very nice and sharp, but the first green

frame was trailed.  I started a 2nd green and took another nap, and

found it had trailed again, but with a jump, and so a gap showed in

all the trails.  By then, it was 3am and I had a headache from so many

catnaps, so I buttoned everything up and stared at my eyelids for the

rest of the night.

If the 9.25" was easy to take out of its forks (it might be, I've just

never done it), I'd make a cradle to support my 6" f/5 Jaegers and 5"

f/5 Jaegers together (the latter needing a new OTA), and use one for

imaging and the other for guiding. But I'd want to be able to go back

to the 9.25" for planetary imaging.

Or...   ...hm.  If I made a folded refractor out of that 6" f/15 lens

I have, with 2 folds, that might fit nicely in place of the 9.25".

But probably I should just rig up a mirror locking setup for the

9.25".  That would require disassembling the OTA, though, to drill

holes in the backplate for lock screws.

Finally, the other way of getting around the mirror flop problem would

be to use another fixed-optic scope as the guider.  But I've already

got a lot of weight on the 9.25", so I'd have to think about this a bit.

-Tim.

--- In Astro_IIDC@yahoogroups.com, Milton Aupperle <milton@...> wrote:

Hi Tim;

Your best bet is to get a multi serial port device like

USB 4-Port Serial Adapter

http://www.keyspan.com/products/usa49wg/

That gives you 4 serial ports , which should be enough for Equinox

with the temp focus controllers, assuming Equinox can use both at the

same time.

As to Flexure. I've have determined that the lions share of my

flexure is mirror movement on the C8 scope. Unless I can lock the

mirror down, a second guide scope simply will not work for me.

HTH..

Milton J. Aupperle