AZ-GTI - sprung worm or fixed and guide results ?

[knobby]

As you probably know the worm on these mounts is sprung ... However it seems to stick hence most users tinker and adjust in the same way as an HEQ5. What are your opinions / results ? - ideally post average guiding results and sprung or fixed.

[Avocette]

I’ve not made any modifications to my AZGTi which is mounted on a SW Star Adventurer EQ wedge. I have a 25cm long piece of 12mm studding as a counterweight bar, with 1kg of large washers at the end, I suppose the effect is of a 1kg weight acting at about 20cm from the axis. The RA axis doesn’t rotate smoothly enough to allow me to find an actual balance between the counterweight and scope/camera load (61ED, DSLR, ZWO mini guide scope and ASI120MC). Here is a practical guide graph from a session this week. 

This is the KStars/Ekos/Indi internal guider analysis graph using the multi-star option. The red line is the total RMS guiding error, although I think much of this comes from the Dec axis. The horizontal pale blue lines show the HFR measurements for the 18x240 second images. Guiding sometimes restarts after dithering and you can see peaks above 3 arcsecs. My assumption for the moment is that it may be worthwhile playing with the details of the guiding parameters but that there may be some stiction/friction in the axes. I am reluctant to open the mount up with such results which give me acceptable images with my 275mm focal length refractor.

[knobby]

Personally if it's guiding that well I'd leave it as is 👍🏻

[knobby]

Over the weekend, I stripped and cleaned mine ( I had been using it with the fixed worm - HEQ5 style as in adjusted as best as possible) adjusted the spring movement to be free but not loose.

Scrubbed all the grease and debris from the gears and lightly lub'd with lithium grease.

More than happy on  the 90 minute test on Sunday night !

Had spells of sub 1arc second for 3 or 4 minutes  - overall for the 90 mins was 1.67.

Going to try upping the guide rate to 0.9 (defaults to 0.75 in synscan app) to give Dec a chance to react next time.

 

[AstroNebulee]

Hi, I'm thinking of stripping my az gti mount and regrease it as its a bit stiff, what is the best lithium grease to use. Also how is the fixed worm method working for you, I have watched cuiv the lazy on YouTube a bit doing this method. 

Edited April 7, 2021 by LeeHore7

[knobby]

Hi Lee, early days but it seems way better with the sprung set up (to be fair, that's how SW designed it )

It's only a tweak of the locking nut needed to make sure it has free travel so easy to change back.

I used https://www.amazon.co.uk/Lucas-Oil-10533-3676/dp/B004X70LZA/ref=sr_1_5?crid=2XLA51IVXF6N5&dchild=1&keywords=white+lithium+grease&qid=1617799700&sprefix=white+lithium%2Caps%2C169&sr=8-5

The stiffness on mine was the collar on the RA bearings screwed down too tight.

Don't sweat too much though as even with this loose it still isn't free enough to balance the mount 😞 but with careful adjustment it gets a lot smoother.

 

 

[AstroNebulee]

Thanks @knobby, thsts the lithium grease I was looking at on amazon also, so will purchase that and when I'm brave enough open up my az gti mount. So would you recommend not having the fixed worm method for the mount.

Clear skies 

[knobby]

They seem to be all different ... But mine performs better with it sprung ( so far anyway )