GPS unit for Synscan controllers

[Damienandwendy (Damien)]

I am about to purchase a SW Goto Dob for myself and a smaller SW Mak on an alt/az Goto mount for the kids. I was thinking about getting a GPS unit so you don't have to enter date/time/position data when starting up, or if the power gets disconnected, etc.

From a few firmware revisions ago it seems that you can't just use any GPS - you have to use the SW one at around $200+.

So two questions:

1. Is it that annoying to have to re-enter the time/date/position data ?

If so:
2. Could I use just the one GPS unit to initialise the first handset/mount then once it's done disconnect and use it to initialise the second one ?

Most reports/posts I have been able to find on the net are 3-4 years old so any new ideas would be appreciated.

cheers

[Astro_Bot]

Originally Posted by Damienandwendy

1. Is it that annoying to have to re-enter the time/date/position data ?

No. If you're sensible with routing cables, etc., you shouldn't lose power either, so it'll be a once-per-session task.

I use my car GPS (removed and held in hand) for both time and position. I've thoroughly tested the SynScan handset time drift over a 6 hour session, and it was <0.5 seconds (basically dead on within my ability to determine).

I don't see any need for a GPS connected to the mount.

2. Could I use just the one GPS unit to initialise the first handset/mount then once it's done disconnect and use it to initialise the second one ?

Don't know, but if you don't already have a GPS, I'd say get a generic one for car or bush use (whichever you will use more) and just use that.

[mithrandir (Andrew)]

Originally Posted by Damienandwendy

2. Could I use just the one GPS unit to initialise the first handset/mount then once it's done disconnect and use it to initialise the second one ?

Neither of my mounts is a SW but you can disconnect the GPS after the mount has got the location + date + time. They set the RTC and it is preserved at least until you power off.
See if StarGPS works with your mount. They say it needs a specific firmware level but you can ask if your controller is different. If you get one of those and switch to a new mount you can just get the right adapter cable.

[shenanigans000 (Greg)]

Originally Posted by Damienandwendy

1. Is it that annoying to have to re-enter the time/date/position data ?

It's not too bad. The unit does remember the coordinates between sessions, so you only have to enter the current date and time at the beginning of each session. Unless of course you change location, then you would need to re-enter position data as well.

[Damienandwendy (Damien)]

Just updating time and date sounds Ok.

Does anyone know how accurate the lat/long co-ords have to be ? ie If I am regularly observing within say 30km of the "home" point that is stored will that be close enough or should I start storing a list of regular locations ?

cheers

[shenanigans000 (Greg)]

Not too sure about that one, as the furthest mine moves is from the sprare room to the back yard.

It will be coming on our next camping trip, but that's not for a few months, so I can't check it out until then.

One area where the manual isn't really clear is the format for entering the coordinates - ie, decimal degrees, or degrees/minutes/seconds. I've used the former as that is the format returned by my navigator.

But if anyone else in here knows any different I'd be interested to hear?

[Astro_Bot]

SynScan uses Degrees and Minutes, e.g. 153 deg 10 min E, 27 deg 14 min S. You can't enter Seconds.

[shenanigans000 (Greg)]

Originally Posted by Astro_Bot

SynScan uses Degrees and Minutes, e.g. 153 deg 10 min E, 27 deg 14 min S. You can't enter Seconds.

Ah ha! I thought I might be entering it wrong. I had this vague recollection of reading something out there on the interwebs about the SynScan unit not using decimal degrees and minutes, but rather the more "traditional" degrees/minutes/seconds - although in this case without the seconds.

Many thanks for the informations.

[sheeny (Al)]

I'm not sure if this applies to your mount... hopefully not. I'd like to think they've learned a thing or two and fixed some bugs...

My old CG-5 mount asked for the date and time and location at the start of the setup procedure, but as far as I could work out, it didn't start the clock running until I had completed my alignment procedure. So I was always out in RA - until I got the GPS unit.

Al.

[Astro_Bot]

SynScan starts the clock at power on with a default time of 8:00:00 pm (I've never seen an option to change that).

At the point where you press Enter to enter the current time, the time is updated and the clock continues to run - pretty much like updating any digital clock. As far as I can determine, the delay between hitting Enter and the time being "latched" by the handset is less than half a second.

I spent a 6-hour session frequently checking time and it was never wrong (within half a second).

[Astro_Bot]

All this talk of which GPS assumes you need one at all.

As already mentioned, you can determine your coordinates from, e.g., Google Maps beforehand - within a few hundred metres is quite accurate enough.

You can get time from your phone - I've used a cordless phone from the yard dialling 1194, but that also works from a mobile (at least on Telstra and Optus but I expect all of them).

Mobile network time, in my experience, is out by up to a minute*, so I wouldn't use that. But if you have a smartphone, you can go to http://time.is/ to see accurate time - it corrects for network delay and I've compared it to NTP servers and found it to never be out by more than a second ... or maybe it was the NTP servers I was using that were out, either way it's in close agreement with authoritative time sources.


* The interaction between phone handset and mobile time update is not easy to configure - my phone has only on and off settings, and I can't see network time directly - I suspect the mobile handset updates infrequently and drifts a lot.

[mithrandir (Andrew)]

Originally Posted by Astro_Bot

* The interaction between phone handset and mobile time update is not easy to configure - my phone has only on and off settings, and I can't see network time directly - I suspect the mobile handset updates infrequently and drifts a lot.

It depends on how your phone sets the time. They normally use the timestamp from the mobile provider and that has to be correct to within a millisecond or the towers can't work out where you are to arrange handoffs. I've got a couple of apps that set time from NTP servers and I suspect those are less accurate, but still within tenths of a second.

As for need, you are debating the difference between essential and useful. It's really easy to get the location or time wrong when you key them in, and remembering to allow for DST is the bane of everyone's existence.

[Astro_Bot]

Originally Posted by mithrandir

As for need, you are debating the difference between essential and useful. It's really easy to get the location or time wrong when you key them in, and remembering to allow for DST is the bane of everyone's existence.

I suppose that depends on how one defines "really easy" - I've never got them wrong.

To me, it's not so much essential vs. useful, but cost effectiveness.

[Steffen]

Originally Posted by Damienandwendy

Does anyone know how accurate the lat/long co-ords have to be ? ie If I am regularly observing within say 30km of the "home" point that is stored will that be close enough or should I start storing a list of regular locations ?

No, it won't be close enough, 30km is at least 16 arc minutes (more in longitude as you move away from the equator). The one arc minute accuracy with which you can enter your location corresponds to at most one nautical mile (1,852m).

I didn't think SynScan controllers could store a list of locations, can they?

Cheers
Steffen.

[Damienandwendy (Damien)]

Originally Posted by Steffen

I didn't think SynScan controllers could store a list of locations, can they?

I typed "storing" .... I meant "create excel spreadsheet with a list of local observing sites".

Thanks for the info on the accuracy.

Cheers