From: Milton Aupperle <milton@outcastsoft.com>

Date: September 13, 2010 9:24:04 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] new guiding log...

Hi Mark;

On 13-Sep-10, at 8:09 PM, Mark Gaffney wrote:

Milton,

The grinding noise has pretty well disappeared altogether now that I`ve loosened the knob below the tripod a little (whilst keeping the rocking play of the mount on top to a minimum) & wasn`t there at all before, unless I stopped slewing & started again when bringing the RA index marks together going west to east.

I've never had that happen on an HEQ5.

The adjustment of this knob requires a compromise between the two.. the rocking or the grinding. I think I presently have it set at best for both..

That should not cause the mount to grind though. That just holds the head / mount to the tripod, right?

I just re read your first post where you said:

"autoguide rate on the mount at 75 % of sidereal"

You might want to cut it down to 50%.

You say in a version of the Manual I`ve printed out that if using long focal lengths, larger Min RA & Dec Dist`s should be used.

Actually it says that only if you have lots of turbulence. See page 17 of the manual.

Your using a very short focal lengths of 450 mm, which is 39% of what I use.

I only had these set at 25 for RA & 15 for Dec.

You mean the minimum distance to move? I would go with 15 and 10 with a 450 mm.

The only value you want to change is likely the "Start Time:"

Should I increase them dramatically next time?

No. If you read the manual, those set the minimum distances limits you expect it to move for your "Start Time". If it moves less than your minimum, then it increases the Start Time to make sure it meets the minimum.

I realise that you`re guiding through your reducer & OAG & not a guidescope & would be using cameras by & large of smaller pixel size..

I don`t understand if the guiding in my set-up based upon the focal length of the Kwiq scope or of the C9.25 or is it again, some sort of compromise between the two?

It has nothing to do with the C9.25 as it doesn't even know the C9.25 exists. All it knows about is the Scorpion Camera and the GPUSB Guider.

Would the FL of the Kwiq be (at 9 x 50 mm) a FL of 450 mm..?

Yes it is.

How much slop would be reasonable..?

Assuming turbulence isn't too excessive < 4%.

I know from your log you`ve sent me you`re getting 2 arc second differences (but this is probably an excellent result obtained from much practise at doing this on your part..?).

It really has nothing to do with practice. It has everything to do with a finely tuned mount that has no slop. You have a lot of erratic backlash on RA and Dec, and that will make guiding poor.

You`re saying you have the distances set at 40 + for just an 1125 mm focal length so what would I need for 2350 mm if this is the case...?!

No, the amount of time it moves controls the distance.

Use < 4% difference depending on turbulence. So if your mount is being moved 100 pixels in each direction, then acceptable variances would be 96 to 104.

I`ll try what you suggest & slew back & forward between targets to see if I`m turning up at the same position as before.

The weather`s pretty dodgy again here so I don`t know when this`ll be possible...

I had one night in the past 7 weeks to image. It's rained for the past week and were expecting snow on thursday. This is about 6 to 8 weeks earlier than normal, so much for "Global Warming" turning Western Canada into a "desert". Going to be a long winter...

TTYL..

Milton Aupperle