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Old 08-05-2020, 06:42 AM
SB (Chris)
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East bias. What weight for string method for HEQ5 pro?

Hi Folks
Im using HEQ5Pro. Has 9Kg imaging loaded on Losmandy saddle.

I’m getting 0.8” to 1” tracking error which I’m happy with but only at >45degrees and <80 degrees altitude approx. Close to the meridian and at low altitudes RA tracking gets worse and get mild to moderate oval stars. Im setting up East bias weighting using string method. I found 250g helps a little with RA error. No problems with DEC error.

Any suggestions for optimum weight on the string?

Thanks

Chris
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Old 08-05-2020, 04:21 PM
RyanJones
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Hi Chris,

Just a quick question, is your mount belt modified ? I use the same mount with 11.5kg on it and get between 0.5 and 0.7 arc second error with the very occasional bump that might degrade a couple of images in a session. The other thing you can try is to tighten the backlash in the worm drives. Really easy to do but you have to be careful not to go too far. Sorry if this is a Segway from you asking about string balance weight. Please ignore if you’ve tackled both of these suggestions.

Cheers

Ryan
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Old 08-05-2020, 05:51 PM
SB (Chris)
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Hi Ryan
Thanks for your reply.

The mount is not belt modded. I have seen the Rowan Astronomy belt mod from FLO which is tempting but would like to see what I can achieve with current setup first. Good suggestion to tighten up the worm gears. I’ll give that a go. Is your HEQ5 belt modded?

Thanks.

Chris
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Old 08-05-2020, 06:22 PM
RyanJones
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Quote:
Originally Posted by SB View Post
Hi Ryan
Thanks for your reply.

The mount is not belt modded. I have seen the Rowan Astronomy belt mod from FLO which is tempting but would like to see what I can achieve with current setup first. Good suggestion to tighten up the worm gears. I’ll give that a go. Is your HEQ5 belt modded?

Thanks.

Chris
Hey Chris,

Yeah, I modded my mount last year and I can’t express how much of a difference it makes. It’s really easy to do and money well spent. It doesn’t get rid of all of the backlash as there will always and should be a very minor amount in the worm drive but the worst of the backlash is in the spur gears that the belt mod replaces. Meridian weighting becomes a whole lot less nessesary then so you can almost have your OTA “balanced”.

Cheers
Ryan
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Old 11-05-2020, 10:26 AM
SB (Chris)
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Hi Ryan,
Tightened up the worm gears by loosening the three hex bolts on RA and DEC motor assembly and adjusting play appropriately. The guiding was great for the first two 10 minute subs but then got gradually worse heading to 1.5" error with RA shifting wildly. Will check everything out for stability again and will have another run tonight.

BTW I'm using ASIAir and Orion 50mm guide scope. Would be interested in your ASIAir guide and mount settings.

... just noticed that the scope is sliding in the tube rings despite the rings being tightened to the max. The guide scope is off-set on the scope so would add minute twist. Could explain the worsening tracking in RA as the scope moves closer to the Medidian... will add some felt to the rings and test tonight.

Chris

Last edited by SB; 11-05-2020 at 11:20 AM.
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Old 11-05-2020, 07:39 PM
RyanJones
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hi Chris,

The OTA shifting in the rings is not good. Good that you noticed it though before you made a million other changes chasing it

My ASIair setting are pretty simple really. I always make sure the speed it set to 8x ( advice given to me when I couldn’t get things to work ). The maximum DEC is factory ( I think ) at 2000ms, the RA I’ve increased to 3000ms. The aggressiveness on DEC again is set factory at 100%. Again the RA gets a push at 175%. Although the adjustments seem quite aggressive, they seem to work. Only when they are combined with a 3 sec exposure though. At 2 seconds they were a bit different.

I’d imagine the guide scopes we are using might be making a difference too. Mine is an 80mm f/5 refractor.

I’m waiting on a filter ( or 2 ) to try on my guide scope also to reduce the glow around the guide star and sharpen it up. It may or may not make a difference, time will tell. I think it’s a worthwhile experiment given the poor seeing I often image in. I’ve also ordered an offaxis guider but that’s going to be for my C9.25.

On the weekend I also stripped down my mount and regreased the bearings. I found some things about the worm drive that I wasn’t all that happy with and may re-address in the future. I’ve readjusted everything and I’m reasonably happy with how it came out. I won’t know if it’s helped and won’t until I get a clear night, hopefully this week sometime.

PM me if you like and want to discuss our findings more ?

Cheers

Ryan
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Old 25-05-2020, 09:50 AM
SB (Chris)
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Hi Ryan,
Thanks for the suggestion to adjust the spur gears. That and tightening things up on the scope rings certainly made a difference to guiding at 0.69" (see attached).

Chris
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  #8  
Old 25-05-2020, 03:04 PM
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Sunfish (Ray)
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I found that non orthagonal mounting of the scope caused cone error where the scope and guider are not pointing in the same direction as the mount axis. As well as backlash , worm adjustment and even a loose puck. Many errors in guiding get worse over time particularly in the west with a lot of weight and balance issues.

You can order the Rowan kit in oz pretty quickly if they have one. Easy to do. Works very well.

https://www.siderealtrading.com.au/p...elt-drive-kit/
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  #9  
Old 25-05-2020, 10:11 PM
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Camelopardalis (Dunk)
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Another thing to consider is that below about 40 degrees altitude you’re looking through much more atmosphere which can cause the guide star to pulsate and jump around a bit more than higher up. You can see this effect but looking at stars closer to the horizon...twinkle twinkle is not cute, it causes rough guiding
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