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RCX 400 in dome

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#1 carriebelltoot

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Posted 13 April 2013 - 07:29 PM

I have an RCX 400 in a Technical Innovations fiber glass dome. I have not had the two together very long. Is it to be expected that the GPS will shut down when the scope is closed up in the dome? The scope is not keeping the time and date accurately.

#2 Christopher Erickson

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Posted 13 April 2013 - 09:43 PM

Unless you have metallic skin on the dome, the GPS should work just fine.


Also, I believe your scope only reads the GPS during bootup, depending on your firmware settings.

#3 GrassyPond

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Posted 14 April 2013 - 07:21 AM

My LX200R's GPS works fine in my 10' TI dome.

#4 carriebelltoot

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Posted 14 April 2013 - 11:21 AM

Thanks for the reply. If anyone has a suggestion as to why the scope will not retain the position time, date and info, please let me know.

#5 nitegeezer

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Posted 14 April 2013 - 11:36 AM

I think you need to provide a little more information.

Does it lose time while it is operating?

After being powered down, is the problem when you first power up?

Is it failing to get a GPS fix?

Other than time, are there any other failure symptoms?

What other info is it losing?

#6 Lorence

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Posted 14 April 2013 - 02:54 PM

I have an RCX 400 in a Technical Innovations fiber glass dome. I have not had the two together very long. Is it to be expected that the GPS will shut down when the scope is closed up in the dome? The scope is not keeping the time and date accurately.


If you find your GPS will not function inside your dome you can install a GPS reradiator.

http://www.mobilegps...uct_info&amp...

I have one in my observatory. Note these units are illegal in some countries.

#7 carriebelltoot

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Posted 14 April 2013 - 04:36 PM

Thanks for your reply. This evening I am going to power up again and look at all the issues you brought up. Surely appreciate the input. I am in Belize, far south.

#8 carriebelltoot

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Posted 14 April 2013 - 04:42 PM

Thanks for that info. I am not clear on this. You say the function of the GPS is to initially find the position of the scope and the rest of the viewing time other components do the tracking?

#9 carriebelltoot

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Posted 14 April 2013 - 04:46 PM

I have only had my dome up a month and not during the rainy season. You are south like me and in a hot damp area. Is humidity a problem inside your dome and if so, how do you deal with it. I am in Belize.

#10 carriebelltoot

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Posted 14 April 2013 - 05:22 PM

Thanks for the suggestion. I will do some more checking to see if I can figure out the situation and might have to consider this. The dome is fiberglass and should apparently not affect the GPS.

#11 nitegeezer

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Posted 14 April 2013 - 06:21 PM

I believe the GPS in the 400 is used the same as in the 200. During auto alignment, the GPS is turned on to determine where and when it is. To my knowledge this is the only time the GPS is used. I never look at the time until after this procedure but I would not be surprised if the clock was inaccurate following a power cycle. Once alignment is complete, the internal clock has been updated and from then on time and tracking are controlled from the base controller. In older units before the GPS was used, I believe there was a real time clock which was powered with a button battery so the operator would not have to enter the time every setup. I am not sure if this has been removed from the newer models as a cost reduction, it may still be there for polar mounted scopes so they can align off one star and go. As far south as you are, I doubt polar mode is an option so I would expect you to do a complete alignment anyway. If you were expecting the GPS to update continuously like a portable unit, since the controller does not expect to change location during operation, polling the GPS would be an unnecessary task.

#12 Christopher Erickson

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Posted 14 April 2013 - 07:12 PM

Thanks for that info. I am not clear on this. You say the function of the GPS is to initially find the position of the scope and the rest of the viewing time other components do the tracking?


Yes. The GPS is only accessed during mount initialization after power-up. During the rest of the time the scope is running, it's internal CPU keeps track of everything.

#13 carriebelltoot

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Posted 15 April 2013 - 12:06 AM

I tried to get this scope on track this evening. No such thing. When I turned it on I did the calibrate sensors routine and the GPS responded and went to Polaris but it was not very accurate. It did not lose time or date while the scope was on but when I shut it down and turned it back on, it kept the date but lost the time, taking it back to a time I had put into it about 3 nights ago. When I turned it on and told it to do a one star alignment and designated Polaris the hand box told me "Not aligned" even though I thought I had it aligned on Polaris.

#14 Spacetravelerx

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Posted 15 April 2013 - 12:10 AM

I am not an expert on this telescope, but isn't there an internal little battery in this unit (one of those flat round ones)? If it is going bad could this be causing your problem.

#15 Christopher Erickson

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Posted 15 April 2013 - 05:18 AM

I am not an expert on this telescope, but isn't there an internal little battery in this unit (one of those flat round ones)? If it is going bad could this be causing your problem.


If it is like the LX200GPS scopes, there is a button battery inside that helps the GPS to maintain its ephemeris data between GPS sessions. It performs no other function. And if it is dead, the only impact is much-longer times for GPS fixes.

I don't have a RCX-400 scope so I can 't say for sure if it is the same as the LX200GPS scopes in this respect.

#16 Christopher Erickson

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Posted 15 April 2013 - 05:27 AM

I tried to get this scope on track this evening. No such thing. When I turned it on I did the calibrate sensors routine and the GPS responded and went to Polaris but it was not very accurate. It did not lose time or date while the scope was on but when I shut it down and turned it back on, it kept the date but lost the time, taking it back to a time I had put into it about 3 nights ago. When I turned it on and told it to do a one star alignment and designated Polaris the hand box told me "Not aligned" even though I thought I had it aligned on Polaris.


If your RCX-400 scope is the same as my LX200GPS scope, the last date entered is saved in flash memory. However the LX200GPS does not have a real-time clock that maintains time while the scope is turned off. When the scope boots up it normally gets time from the GPS module and uses it to set the clock in the mount's computer. The mount computer's clock goes off when the scope is turned off. It does not maintain time while the scope is off.

If the LX200GPS scope either doesn't get fix data from its GPS module, or if the GPS is disabled in controller configuration, the scope asks for manual time input by the user. It always defaults to 8pm.

Hopefully the RCX-400 is similar-enough to the LX200GPS that this information is useful to you.

#17 nitegeezer

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Posted 15 April 2013 - 06:13 AM

When I turned it on and told it to do a one star alignment and designated Polaris the hand box told me "Not aligned" even though I thought I had it aligned on Polaris.


If your scope is permanently mounted in polar mode, then it can align using one star if that star is significantly away from Polaris.

If your scope is in Alt/Az mode, my understanding is that you must align using two stars with neither being Polaris.

This alignment is required no matter what scope/mount you have. If it is similar to an LX200GPS, there is an Auto Align mode that does several sensor checks and then requires that you center two stars from it's alignment list. Since you are in an observatory, there should be a park mode before you turn it off. If using this mode, you must never loosen the clutches. The next time you power up, you can come out of park mode and then confirm alignment using one star but again it must not be Polaris.

#18 jrcrilly

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Posted 15 April 2013 - 07:04 AM

If it is like the LX200GPS scopes, there is a button battery inside that helps the GPS to maintain its ephemeris data between GPS sessions. It performs no other function. And if it is dead, the only impact is much-longer times for GPS fixes.

I don't have a RCX-400 scope so I can 't say for sure if it is the same as the LX200GPS scopes in this respect.


Yes, they both use the same scheme.

#19 jrcrilly

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Posted 15 April 2013 - 07:06 AM

When I turned it on and told it to do a one star alignment and designated Polaris the hand box told me "Not aligned" even though I thought I had it aligned on Polaris.


It was behaving normally. The "not aligned" message was to inform you that you had not aligned it.






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