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Not sure if this is a mount question or a software but I'm leaning towards ... neither ? 

Long, long story prolonged by pants weather and lack of time but my AVX died a while back so needed a new mount.

I was torn between the EQ6R and the HEQ5 belt modded. I' have a mildly iffy back so as much as I wanted the EQ6R I just thought it would rarely get used. Opted for the HEq5 belt modded which according to the supplier should manage just under arc second guiding with my C8edge. It was naff ! so naff that my AZ-Gti guided better ! retailer where great and sent me a replacement which is honestly only just better. I've tried all sorts of settings in phd2, perfect balance, East heavy, West heavy, a lot heavy and slightly heavy ...

Gave up on the C8 and had a dabble last night in the 2 hour clearish patch with just the 72ED.

Went through all the above again and after much faffing managed a spell towards the end of 1.2 ish arc seconds.

PA was near perfect according to Sharpcap but PHD nagged about improving it.

Also nagged about guide star focus but it's an OAG and as good as I can get it.

I'm starting to think that because Polaris is just above my roof that maybe I'm never going to improve this ?

One day, I'll take it somewhere dark to properly test it ? 

Guide log attached if you're bored and craving some vaguely astro related activity.

PHD2_GuideLog_2020-11-26_175742.txtimage.thumb.png.9519fe9d9089dd7dffbdc27837fff474.png

Best section was at 20:32 onwards

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I’ve just watched the latest Astrobiscuit Youtube video where he goes to DarkframeOptics where Dave tunes mounts. The video is called “best mounts for Astrophotography”. Dave is probably a world expert on many mounts (not my words) and after his small company has tuned the mounts then claims sub arc second guided with the HEQ5 with the Rowan belt mod and other tuning. He also recommends the EQ3-2(low price), HEQ5 and EQ6R (mid range mounts) as being great for AP.

I have an HEQ5 pro with the Rowan belt mod and not sure of my figures but get decent subs (from memory as it has been a long time lol). However I’m not using a C8. Also mine isn’t tuned by DarkFrame.

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Posted by: @TerryMcK

I have an HEQ5 pro with the Rowan belt mod and not sure of my figures but get decent subs (from memory as it has been a long time lol).

I saw the same video, and sub arc guiding after a belt mod and tuning is very feasible. I upgraded my old EQ6 with a belt mod, also replaced most of the bearings in the mount too. I get RMS of 0.6/7 quite regularly with good seeing. For anyone wanting to upgrade their mount with the Rowan belt mod, it's quite a simple operation, very few tools are needed.

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Posted by: @GazAstro

It was naff ! so naff that my AZ-Gti guided better ! retailer where great and sent me a replacement which is honestly only just better.

Just looking at your guidelog, the Polar alignment seems to be way out for Sharpcap, normally you can get within a few arc seconds, according to Sharpcap's readout. I doubt your bad guiding is because of polar alignment, seeing probably affects poor guiding more than any other condition. Also I would try and move the mount physically in the RA and DEC, even the tiniest bit of play can affect guiding and backlash. The mounts are quite easy to tune up, all that is needed is an allen key, or two.

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Cheers, it's strange as Sharpcap says 'excellent' it was 20 arc seconds from memory. Everything seems solid on the mount, no signs of untoward movement. Then the guide log disagrees !

I polar align twice, first time starting at home position, then 90° rotation . Then start again at 90° then back to home position.

Might have to have a dabble with drift alignment.

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Posted by: @GazAstro

Cheers, it's strange as Sharpcap says 'excellent' it was 20 arc seconds from memory.

I have had it within 10 arc seconds in Sharpcap, then when I calibrate the guiding in PHD2, and run the guiding assistant, it can be be severeral arc minutes out of alignment according to PHD2. So either Sharpcap is getting it wrong, or PHD2. I tend to trust Sharpcap more than PHD2, I recently saw a video on youtube were Sharpcap and Polemaster were compared for accuracy, and Sharpcap was the more accurate of the two. The only other reason for bad guiding, is flexure in the guidescope, or the guide camera

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Hello Gary

Looking at the info supplied I would suggest its a mixture of suboptimal polar alignment and either backlash or flexure. Are you certain that all components of your OAG are tight and flex free??

There is a good website here that explains clearly how to tune out the backlash - (and strip the mount and sort out the bearings if you are so inclined - its not difficult)

http://www.astro-baby.com/heq5-rebuild/heq5-m1.htm

There is also a good guide on getting the best out of PHD2 here - 2nd item down from the top.

https://www.davidbanksastro.com/how-to

And finally a good article on drift alignment using PHD2 which I have always found to be the most accurate method - you can get close with Sharpcap and Polemaster etc but drift alignment is the only method that cannot be wrong. 4th item up from the bottom.

https://www.davidbanksastro.com/how-to

I had an Orion Sirius (Same as HEQ5 but painted black) and I stripped it using the above guide and replaced the bearings with better quality ones from SKF/FAG etc - regreased it with 'Superlube' and very carefully adjusted out as much backlash as I could without binding. Then careful drift alignment and in decent but not extraordinary seeing my guiding was always ~0.5" total RMS.

unnamed.thumb.jpg.1c9ed449787cf1f2bf9d04f21055a7f8.jpg

 

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Posted by: @skipper-billy

Hello Gary

Looking at the info supplied I would suggest its a mixture of suboptimal polar alignment and either backlash or flexure. Are you certain that all components of your OAG are tight and flex free??

There is a good website here that explains clearly how to tune out the backlash - (and strip the mount and sort out the bearings if you are so inclined - its not difficult)

http://www.astro-baby.com/heq5-rebuild/heq5-m1.htm

There is also a good guide on getting the best out of PHD2 here - 2nd item down from the top.

https://www.davidbanksastro.com/how-to

And finally a good article on drift alignment using PHD2 which I have always found to be the most accurate method - you can get close with Sharpcap and Polemaster etc but drift alignment is the only method that cannot be wrong. 4th item up from the bottom.

https://www.davidbanksastro.com/how-to

I had an Orion Sirius (Same as HEQ5 but painted black) and I stripped it using the above guide and replaced the bearings with better quality ones from SKF/FAG etc - regreased it with 'Superlube' and very carefully adjusted out as much backlash as I could without binding. Then careful drift alignment and in decent but not extraordinary seeing my guiding was always ~0.5" total RMS.

unnamed.thumb.jpg.9086f94184f5df5d90f35fff67826fa1.jpg

 

Thanks Skipper, all good information ... But I'm not going to strip what is essentially a brand new mount ... Its about 4 months old but used 3 times ?

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Posted by: @GazAstro
Posted by: @KevS

Gaz, if you run the guiding assistant via PHD what does the "backlash" graph look like? This is my example with a bit of mount tweaking.

image.thumb.png.f67de141547f6ba40cd52a1b24680e03.png

I'll dig a screenshot out later but from memory it was slightly worse than yours ... 599ms rings a bell.

 ------------------------------------------------------------------------------------------------------------------

It was 500 ms

image.png.e4c3165e106a653176fb32e826340633.png

500 ms 

image.png.bb12f2d24737764d4536f92ee46abc51.png
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  • 2 weeks later...

Gary, try the following. Open up PHD, go to "Tools" then "Guiding assistant" On the bottom of the guiding assistant box open the tab that says "see previous". Go to the last guiding session which will provide polar alignment etc from the last run. Click the "show backlash graph" button. The graph it shows will provide an indication of any backlash in the mount. If the red and white lines deviated from one another you may have backlash issues. 

K

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So, stripped, cleaned and lub'd with superlube today, only did RA as Dec guides well.

Greeted with a nice shard of metal which didn't bode well but otherwise all seems ok.

RA setting circle is catching on something so I've left it off ?.

Loosened the pressure on Dec taper bearing as pretty stiff. Much better now.

I've attached a video taken in best Darkframe optics style ...

Overall pretty happy, can't wait to try it out ??

PXL_20201212_130556536.thumb.jpg.fc080eb2eb919bca899f48559838868e.jpgPXL_20201212_155107987.thumb.jpg.c8cd41db34281dd270f3d27d596dd188.jpgPXL_20201212_155128417.thumb.jpg.b063cdc76ba1df30fa1a407118153f4d.jpg

 

https://drive.google.com/file/d/1DmfINfbCffX7WjYmIPmmZHfpXReZa_iZ/view?usp=drivesdk

https://photos.app.goo.gl/K4aAfBc7ZA736eSB7

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Cheers chaps ... I just don't get it ... It shouldn't be this hard ! My AVX used to guide smoothly at just around 2 arc seconds, not brilliant but no sudden lurches how is it that with a better mount it takes so much baby sitting and tweaking ?

I see so many people saying theirs guides sub arc second.

Maybe I'll take up cross stitching ?

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Cheers, I really don't get it ! Did exactly what AstroBaby guide suggests, if anything I feel I might have over tightened the worm mesh, there really is no movement ... Checked it again this afternoon and ran an ammeter on supply as I adjusted the mesh while slewing. Sure enough as soon as it's snug (when you'd feel it get harder to turn by hand) the current draw starts to go up.

How it is now it's just backed off til current draw stops changing.

Another night to test please ?

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