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Old 12-09-2014, 06:40 AM
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codemonkey (Lee)
Lee "Wormsy" Borsboom

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Join Date: Jul 2013
Location: Kilcoy, QLD
Posts: 2,058
Quote:
Originally Posted by LewisM View Post
Check RA spur gear tolerances. Replace the factory grease. Remove any detritus that has stuck in/on the grease. Backlash in Dec was always a major issue for me, until I cleaned, polished, re-meshed the tolerances.
Ok, thanks for the tip Lewis :-)


Quote:
Originally Posted by cometcatcher View Post
Your guide star looks horrible. I'm not surprised PHD is having trouble guiding. Are you trying to guide on a waaay off axis star? I haven't used my OAG for years but star quality wasn't it's strong point.
I get all kinds of crazy shapes with the OAG, from slits, to triangles to crescents, depending on how it's adjusted, but the one thing that I never get is a normal looking star. I'm pretty confident that this isn't related to the star shape as I saw the same kind of movement when trying to guide with the Atik 314L on axis.

Quote:
Originally Posted by Shiraz View Post
No, you certainly don't need to take it to bits - only do that as a last resort. There are some hex head bolts that lock the worm carrier to the main body. You undo them very slightly so that the worm carrier can slide on the body and then use the small opposing screws to wind the carrier in or out to adjust the clearance. Then tighten the main bolts back up. takes about a minute when you get the hang of it. It is a normal part of owning an EQ6 - they are even supplied with the key wrenches to do it.

This shows you how and explains what the process does (you should not need to do the end float adjustment on the worm bearings though)
http://www.astro-baby.com/EQ6%20rebu...0alignment.htm

others have commented on the guide star image quality. I have found that the centroid calculation in phd is quite OK with images like yours - it seems to be doing well in DEC in your case and I doubt that there will be any problem in RA. However, it is worth choosing an unsaturated star, rather than one with obvious saturation like the one in your example.
Awesome, thanks mate.

I've tried various exposures to try and reduce the effect of seeing, lending me to blown stars (worse than seen here) and well exposed ones, but the problem persists regardless.

I agree, the fact that DEC is fine suggests to me that the shape has nothing to do with this.

Quote:
Originally Posted by Peter.M View Post
Honestly, I assume you are using an OAG due to the star shapes. I would take an image and see how it comes out, if star shapes are less than ideal then look into it. My graphs are regularly like this (in arc seconds) and I have no issues with my images.
Thanks Peter, that's what I believed.

I took some exposures in the beginning and ended up with square stars, thus the quest to optimise the graph, but you're right... I could have a horrible graph and good results.

Quote:
Originally Posted by Amaranthus View Post
Lee mentioned that he was using an OAG. As others noted, star shape is not critical - the centroid is based on an assumed not characterized star shape.

I'd strongly advise you try, as a first step, to increase the Westerly bias on the mount. This can really help in keeping the gears engaged. It should NOT be perfectly balanced!

PHD and PHD2 use identical guide algorithms.
Thanks mate :-) I've biased the balance in every possible way, perfect, east heavy, west heavy... it no doubt had an effect but nothing resulted in me having a graph that looked like it would give usable results.

Quote:
Originally Posted by jjjnettie View Post
We should get together one evening Lee. Do some trouble shooting. Not that I'm all that technically minded, I've had a little experience with it.
That sounds great Jeanette!

Quote:
Originally Posted by atalas View Post
Hi Lee

Mate don't go pulling the mount apart!!its a very we'll tuned mount.
I never ever had a occasion where it failed to guide well with guide scope.
The PHD graph is showing it to be too aggressive and slight balance.
Balance isn't equal in all areas of the sky.
The noise is normal for all EQ6.
Hey Louie, thanks for posting mate :-)

The last part of the graph has minimum move set to 1px, aggressiveness to 50% and hysteresis to 10, so I think I can safely rule out the aggressiveness of the software settings as being a factor.

The maximum pulse was also reduced to 400 in RA and 120 in DEC (RA was down at 120 at one point a few nights ago but I bumped it back up because PHD seemed to be struggling to get it back after it went out in one direction).

I also tried shifting the balance at various points after slewing to that location but before recording this chart that you see (there were other charts, different but equally bad).

This was somewhat low on the eastern horizon, and I think it did seem worse than when I was pointed close to the meridian, which might suggest that balance is a factor in it though...?
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