From: Milton Aupperle <milton@outcastsoft.com>

Date: August 29, 2010 10:51:44 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: guiding last night... [1 Attachment]

Mark;

On 29-Aug-10, at 12:14 AM, Mark Gaffney wrote:

Milton,

Is this better...?The previous attempt was confused by placing it at the end of the message after the other attachments..

Yes, it actually contains the text - not some html; gibberish.

The log shows just as bad (maybe worse) non repeatable movements as the first log you sent a week or so ago. If you looked through the first 20 lines of the file you can see this for your self.

CalibX4: R Dist 18.29 X1: 925.37 Y1: 472.34

CalibX5: L Dist 11.60 X2: 934.94 Y2: 478.90

CalibX6: R Dist 7.74 X1: 939.50 Y1: 472.64

CalibX7: L Dist 84.34 X2: 871.94 Y2: 523.11

CalibX8: R Dist 46.91 X1: 917.96 Y1 514.04

CalibX9: L Dist 8.49 X2: 909.59 Y2: 515.41

Your RA calibration result is horrible. For the same amount of movement time, it moves 8 pixels one time then 84 the next, then 46 pixels - it's all over the place. Tracking will be poor to none existent because of this.

Some hand controllers have a back lash setting for RA and Dec. If yours does have one, make sure both are set to zero for both RA and DEC. What it does is reduce the amount of motion that gets actually applied to the mount. So if it was set to to only move the scope after 10 arc seconds of motion has happened, well it chops 10 arc seconds of motion off. That also affects your GOTO positioning too.

But I think the issue is your mount has slop on the RA axis and needs to be adjusted. I don't know CGE mounts at all, so I can't help. Try searching Google / Yahoo with the query terms:

CGE RA backlash adjustments

and you'll find a tonne of references like:

http://www.cloudynights.com/ubbthreads/showflat.php/Number/3974086

If you have Gear backlash / slop on the Ra and Dec axis, you will not get good guiding and this also affects your GOTO repeatability. Since neither of them are repeatable, that suggest a mechanical issue with something loose.

In one of your messages on this subject you say that you use a guide rate of 0.5x or 0.75x for 1100 mm focal length..You also say you have the starting rate at 7.0 seconds & the min pixel distances at 25 for RA & 20 for Dec (this is in a message on the 19th August early in the morning here- 6.06 am).

Can you hazard a guess what I should be using for 2350 mm?

Since your not using the main scope for guiding, it doesn't matter what focal length your main imaging scope is at.

The Kwiq scope is pretty much the same item as my 9 x 50 finder from my C10. It`s been sold now as a complete deal to my uncle so I couldn`t cannibalise it`s finder- which can be done by removing the EP attachment screw in..(I tried this whilst waiting for the Kwiq scope to arrive)

Entering 50 mm aperture & focal ratio of F9 into "CCD calc" gives a FL of 450 mm. With the Scorpion this gives a chip size of 5.3 x 7 mm, an image scale of 2.01 arc/sec/pixel & a FOV of 40.3 x 53.7 arc minutes. Does this sound right?

No it doesn't sound right at all.

The Scorpion 20S0 has a Sony ICX274 CCD which is 8.5 mm W x 6.8 mm H and each square pixel is 4.4 microns. I got this from PGR's Scorpions manual on page 12.

Depending on whose calculator you use you get a FOV of about 54 x 40 arc minutes FOV and about 2 arc seconds per pixel.

On the CG-5 it is suggested that most of the backlash inherant in the gears is remove by doing the final approach to the alignment stars with the Up & right directions.

That's for slewing to objects manually, that has nothing to do with guiding.

Milton J. Aupperle