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Absolute encoder upgrade

nakbrooks

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nakbrooks Member

nakbrooks

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I am considering upgrading my DDM85XL to use absolute encoders. ASA have given me a quote which is expensive, although a lot cheaper than buying a new mount.

 

I am considering this because I intend to move to a hosted facility and need trouble-free remote operation.

 

Can anyone advise me whether the benefits of absolute encoders are worthwhile for remote operation, given the upgrade cost of several thousand euros.

 

Thanks

 

Nigel

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lukepower Member

lukepower

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I am using two ASA's with the old encoders remotely at Nerpio, without serious issues.

The only thing you will need is some sort of remote IP camera to check the mount position before doing a homefind. I also added two marks (with duct tape) to know where the encoder reference marks are located, so that I can move the mount in the right position easily.

 

If you have the bucks, do the upgrade. Othwise buy a decent IP camera.

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ChristerS Member

ChristerS

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Hi Nigel, I second Lucas stick with the encoders and use the cams, also use a park position after each session to be in the right position for the next run.

The DDM85 should have gyros built in to try to find the zenit-east position before atemting a homefind, this worked excelent at first but after a while, perhaps some software change, they was not reliable so I now use the cames when homefind after parked close to zenit-east. 

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nakbrooks Member

nakbrooks

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Thanks. I've also been using my DDM85XL remotely (albeit from the comfort of the adjacent house, not a thousand miles away). I've had a couple of occasions where the mount has lost track of its position and got into a very strange position but have managed to get it back using the cameras. Think I'll continue to rely on that, although I may need to rethink if I automate an entire night session using ACP without any visual supervision.

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ChristerS Member

ChristerS

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Nigel, one other thing after it started to not find home using the gyro was that it often even after I placed it at zenit-east I noticed the pier side was west not east witch made the homefind fail, so now I always check and set correct pier side, since then I have not hade any problems.

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Josch Member

Josch

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Hi Nigel,

I am running a DDM85 from a remote site in Chile since 2011. If you park the mount and do not power down but only switch off the motors, then there is no need to do a homefind every night before the start of the session.

Only if you loose power a homefind using an IP Cam is necessary. No need for aboslute encoders.

I run literally every night and am sleeping when the whole system starts and gte data.

Of ocurse nothging is fool proof and sometimes the annoying thing is that MAXIM looses connection to the CCD randomly (like last night) and I loose half of the night as I check when getting up in the morning.

 

Josch

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nakbrooks Member

nakbrooks

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Thanks Josch, that's reassuring.

 

Incidentally I've had problems with Maxim losing the camera connection almost every session for years. I have to reconnect the camera. I've not been able to diagnose the problem but I suspect USB issues.

 

In the new observatory I will have new cables and a new PC and will not need to use an extra USB hub so I'm hoping that will solve my problem.

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john32712 Member

john32712

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Nigel,

 

Apologies for the slow response! I live on Marco Island Florida where the recent hurricane has devastated the area.

 

Anyway, regarding the benefits....

1. In my opinion, for the level of sophistication of the drive system, it made no sense to me to have a mount that could lose its position if power was lost or various other reasons. Let's face it, even the lowest level of consumer mounts has a home find routine that "counts" from the initialized position. I'm sure this comment will not sit well with some. But I love that the position of the mount is known always and extremely accurately

2. It might be my imagination, but the mount appears to track better and slews seem more accurate

3. If I remember correctly, it took about 5 weeks to get my mount back

 

What you probably want to know the most, is it worth it? I would say a resounding yes! Startups are a breeze and home finds are a distant memory

 

John

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nakbrooks Member

nakbrooks

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Thanks for yours reply John, particularly given your other priorities at this time.

 

I'm still undecided. It's very tempting to get the upgrade now while everything is disassembled as I move it to e-eye in Spain. However the cost is significant so I may wait and see how it goes.

 

I never had major problems in the past - just a couple of excursions following power outages mid-session, but I was able to resolve those ok using cctv.

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Corpze Member

Corpze

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May I ask how much the upgrade is?

 

The DEC bearing of my DDM85 standard is probably giving up soon, I can feel small uneven resistance when I am turning the axis.

I am thinking of returning my mount for service and upgrade.

 

/Daniel

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