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@skipper-billy

Yep, and accepted suggestions.

On Astrobabys guide, how tight do you do the

'Tighten the upper set screw JUST UNTIL ANY PLAY STOPS.
Note: You should loosen and tighten these screws
by approximately 1 quarter of a turn each time
.'

bit ?

How can that be defined / quantified ?

 

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Posted by: @GazAstro

Tighten the upper set screw JUST UNTIL ANY PLAY STOPS

Hi Gary,

I'm going through this same process myself. I found that there was only a hairs-breadth difference between 'until any play stops' and when the axis starts to bind. A quarter turn of the set-screw was FAR too much adjustment to find the sweet spot. I tightened slowly until there was no movement and it started to bind, and then backed off slightly. I still have a very slight amount of play in RA but no binding.

My guiding is about the same as yours at the moment. I definitely have a problem with balance - guidescope is mounted off-centre on the main scope, and is pulling everything quite strongly to the side. I'm also considering replacing the bearings with new ones. I've already re-greased following the astro-baby instructions.

Padraic.

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Posted by: @GazAstro

Note: You should loosen and tighten these screws

by approximately 1 quarter of a turn each time.'

Quarter of a turn is too much when fine tuning. A sixteenth of a turn will give more accurate results. Don't forget to check the worm gear for lateral movement, by making sure the float adjuster is not too tight, or too loose.

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Posted by: @padraic-m
Posted by: @GazAstro

Tighten the upper set screw JUST UNTIL ANY PLAY STOPS

Hi Gary,

I'm going through this same process myself. I found that there was only a hairs-breadth difference between 'until any play stops' and when the axis starts to bind. A quarter turn of the set-screw was FAR too much adjustment to find the sweet spot. I tightened slowly until there was no movement and it started to bind, and then backed off slightly. I still have a very slight amount of play in RA but no binding.

My guiding is about the same as yours at the moment. I definitely have a problem with balance - guidescope is mounted off-centre on the main scope, and is pulling everything quite strongly to the side. I'm also considering replacing the bearings with new ones. I've already re-greased following the astro-baby instructions.

Padraic.

Cheers Padriac, how old is yours and what weight are you carrying ( not you persoanlly, but the scope ? )

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Posted by: @GazAstro

what weight are you carrying

Cheeky bug@er! :-)

The mount is quite new - maybe 2-3 years old. I bought it new myself. I think that at this stage, I have spent more time tuning it than I have imaging with it, given the weather of late.

My payload is 6.5kgs so well within the HEQ5 limit - Esprit 80, ASi1600MM Pro, ZWO efw mini, Starwave 50mm guidescope w/ ASI290MM Mini. I've had to buy a replacement dovetail bar for the Esprit, and will need to get some scope rings as soon as they come available again, so that the guidescope can be properly piggybacked on top and the whole thing balanced.

 

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Posted by: @skipper-billy

Are you 'tuning' your mount at the same sort of temperatures that you will be imaging at ??? I had a Sirius (Heq5 but black) and I couldn't figure out why it had zero backlash in the lounge but did when it was outside - all down to the temperature!!

Very good point, I did try to keep it stable. Mount was in garage nice and cold but it probably did warm up a bit while I was lovingly tweaking and cleaning.

In theory the casing should expand when warm but so should the worm gear ... Different amounts of course but enough to make a difference I guess.

We keep going back to backlash but I'm thinking maybe it's too snug ? I've backed it off a tad so maybe a tiny bit of play but with it East heavy that won't matter.

If it tracks well like that then maybe I'll just tweak it in very slightly and check each time ... Could take years though ?

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Rushed out to garage after dinner ... Checked and backed off very slightly with the reasoning that too tight could stall but too loose would give backlash ( East heavy would hide that ) PA to excellent in Sharpcap ... Aimed toward Betelgeuse and calibrated ... Ran guide assistant for 5 mins ... Accepted suggestions ... Got excited when it settles at around 0.6 Dec and 0.9 Ra (1.2 total)

Sadly after about 5 mins it crept back up to 1.8 ?

Might be on its way to Darkframe ?

Thanks again to all your suggestions, very much appreciated.

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  • 2 months later...

So, I finally gave in as I was wasting so much time on this. Sent to Darkframe - got it back in 3 weeks ...

Had a fair old crack with it last night trying different settings ( 1 to 3 seconds guide images, EQmod guide rates etc)

Settled on 3 seconds PHD2, binned guide cam (ZWO 290 mm) 0.5 guide rate in EQmod and followed guide assisitant recommendations.

Had good spells below 1 arc minute, still having occasional spikes but so much better than previous attempts.

Logs attached in case anyone sees any room for improvement. Also a wee Horsehead, about 45 mins of 300 second Ha subs attached.

Thanks again to all that helped 👍

PSX_20210219_115741.jpg

PHD2_GuideLog_2021-02-18_174042.txt

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