HEQ5 and ST4 Guiding

[Mike Waring]

Please offer suggestions on improving this guy in Ottawa's ST4 guiding.

Log 5 the fifth Calibration on Vega was successful, but the Log 7 guiding session after GA was higher in Dec on M51.

Log 8 guiding session was on M57 which is closer in Dec to Vega where the Cal was carried out.

 HEQ5 mount; Orion Deluxe Mini 50mm guide scope with StarShoot (52064) autoguider

Sky-Watcher 100mm (F9) Evostar Black Diamond ED APO refractor; 0.85x 100ED focal reducer/field flattener 

Canon (modified) T6i with IDAS LPS D1 filter; 

I only have the Guidelog:

https://stargazerslounge.com/applications/core/interface/file/attachment.php?id=365683

Thanks

Michael

Wiltshire UK

[Andy Galasso]

Hi Michael,

Guiding appears to be limited by the 13.6s period RA error component.  I think that the RA guiding could be improved by using shorter guide exposures, like 1s, or 1.5 s at most.

I'd also suggest upgrading to the latest version of PHD2 (or better, the latest dev version), and running the Guiding Assistant with 1s exposures to get recommendations for the RA and Dec min-move settings.

The ~765mm focal length of the imaging scope should be relatively forgiving and the above-mentioned RA guide error may not even be visible in the main camera subs.

Andy

[Mike Waring]

Thanks Andy

He's worried about drift in some of his subs, which I looked at and thought minimal.

The 13.6 sec component is too fast for PPEC ?

Michael
Wiltshire UK '

[Brian Valente]

Michael - It's possible to try and address it with PPEC, but you would need very short guide exposures, like 0.5 sec ish

I had a 31s periodic error, and my main PE was handled by the mount's PEC. so i used a fixed 31s PPEC interval and very short exposures, and it helped. but there is a tradeoff in that you are starting to chase seeing there

B

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Brian Valente

portfolio brianvalentephotography.com 

[Andy Galasso]

On Sat, May 25, 2019 at 3:56 AM Mike Waring wrote:

He's worried about drift in some of his subs

I would suspect differential flexure.  If the amount of drift in the imaging subs is more than a couple arc-seconds, differential flexure is the culprit.

Andy

[Mike Waring]

Thanks Andy, as I thought.

Brian, as you can see he has a finderscope type guide mount, scope held against a ring at the front and by 3 screws at the rear.
I've tried explaining to him how poor this is.......

Having said that his elongation is minimal in my opinion, but he prefers to reject up to 50% of his 3 minute subs.

You could argue that's an easier way to get good results than improving an HEQ5 !

Michael
Wiltshire UK

[steve]

Hi

I've an eq6 which had a similar 10s peak. I eliminated it by moving the
idler gear relative to that on the motor spindle. I think the heq5 has a
similar meshing. Maybe worth a try?

Cheers and HTH,

Steve

>

[Mike Waring]

Thanks Steve

Could you expand that a bit please ? Where is the idler gear located, is it an intermediate gear between the motor and the worm ?

An image I could pass on to the owner would be appreciated.

Michael

Wiltshire UK

[steve]

Hi

NP. Here is the gearbox. It's trial and error. Remove the RA centre gear and rotate it a few teeth at a time until the harmonic goes away.

Photo of the mount with the cover removed here.

HTH

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