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Switching to iOptron: What I learned from my new GEM45

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#1 Michael Covington

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Posted 01 May 2021 - 05:39 AM

These are short notes on things I learned about using my new iOptron GEM45 equatorial mount, moving from Celestron mounts (AVX and CGEM). The CEM40 is very similar to the GEM45, and other iOptron mounts are also rather similar. I assume you have the instruction manual for your (actual or planned) iOptron mount; manuals are available on line.

Click here to view the article
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#2 zeddie

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Posted 01 May 2021 - 07:49 AM

Where in the menu is the "Search Zero Position" option? It's not with "Set Zero Position" or "Goto Zero Position" (at least not on my iEQ45 Pro). Does the iEQ45 Pro not have the internal index marks, or is it possible I need a firmware update? Also, I know you can add your own index marks, but how do you set it at the time you are going to add the index marks? Or, If you don't add the index marks, do you have a good way to set the zero position? I use an inclinometer, but I think that holding it against the counterweight bar is prone to error, and not the best solution. I use the inclinometer to set the counterweight bar parallel to the ground and then use the inclinometer to set the declination axis to my latitude. Then use the inclinometer to set the counterweight bar perpendicular to the ground. I feel like there must be a better way.

 

-Thanks


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#3 Billx

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Posted 01 May 2021 - 10:45 AM

Great article describing how iOptron mounts work.  I have the iEQ30 pro and can remember when the camera accidentally hit the tripod when slewing.  It made that awful noise and I thought I damaged it.  But it seemed to work fine afterward.  I am glad you verified how the gears work.  As in  the reply above, how do you search for zero, and does it matter where I set it as long as I set it when I set up, aiming close to Polaris.  I am using a Asiair to polar align and image.



#4 daveco2

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Posted 01 May 2021 - 07:28 PM

Excellent.  I went from an AVX to CEM40 and sure could have used this information at the time.  Nonetheless, thanks for clearing up some nagging questions.



#5 Michael Covington

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Posted 02 May 2021 - 10:58 PM

Where in the menu is the "Search Zero Position" option? It's not with "Set Zero Position" or "Goto Zero Position" (at least not on my iEQ45 Pro). Does the iEQ45 Pro not have the internal index marks, or is it possible I need a firmware update? Also, I know you can add your own index marks, but how do you set it at the time you are going to add the index marks? Or, If you don't add the index marks, do you have a good way to set the zero position? I use an inclinometer, but I think that holding it against the counterweight bar is prone to error, and not the best solution. I use the inclinometer to set the counterweight bar parallel to the ground and then use the inclinometer to set the declination axis to my latitude. Then use the inclinometer to set the counterweight bar perpendicular to the ground. I feel like there must be a better way.

 

-Thanks

2 things.

(1) I am getting reports that some mounts either do not have "Search Zero Position" in the menu, or report something like "Feature not available on this mount" if you choose it.  Apparently not all of them have the internal mechanical-photoelectric index.

(2) You can use bubble levels to find zero position.  Do it carefully and think through what you're doing -- make sure your level isn't free to move in some direction that throws it off.  Or set up the mount, star align, and then set the R.A. to 6 hours ahead of the current sidereal time and the declination to +90.  I think that will move the mount to zero position.  Then tell it to stop tracking.  I have not actually done it this way and would like to hear from anyone who has.



#6 Michael Covington

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Posted 02 May 2021 - 10:59 PM

From discussions in the iOptron group on Facebook I'm learning that there are a LOT of differences between model and model -- in fact there is apparently a "new" GEM45 that may not support "Search Zero Position" but I don't have precise details.

This comment section is a great place to accumulate information about such things.  Thanks in advance for all your contributions!


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#7 zeddie

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Posted 02 May 2021 - 11:35 PM

Hi Michael. It's pretty obvious how to set the RA axis to zero position using a bubble level, but how would you do the DEC axis?

 

Thanks.



#8 GOLundby

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Posted 03 May 2021 - 03:08 AM

From discussions in the iOptron group on Facebook I'm learning that there are a LOT of differences between model and model -- in fact there is apparently a "new" GEM45 that may not support "Search Zero Position" but I don't have precise details.

This comment section is a great place to accumulate information about such things.  Thanks in advance for all your contributions!

We need a short foot note describing the changes done to GEM45 recently. Basically they have simplified the production by delivering GEM45G without the built-in IGuide. The changes basically is in connectors where there is only one USB2 input placed at the end of the RA house together with a 2.5-5.5mm power in. This USB2 is internally connected to a USB2 hub with 3 clients; the Mount, the IPolar and the USB2 connector at the sadle. The Sadle is also changed and now contains the box where the IGuide scope would reside, making it much wider. It is now dual purpose with the "Vixen" clamp just below the "Losmandy" clamp. (If you have a short OTA and are using an Auto Focus device, this may conflict with and hit the box for IGuide.) The sadle has two outlets for power (2.1-5.5mm) and a guide port in the rear area and a USB2 port in front. There no more is a possibility to reconfigure the connectors from back to front to make room for own internal cabling.

 

As mentioned, there seems to be no seek Zero position implemented for this model. I guess that during setup as described, when you have counterweights on, if you let it swing freely the Zero for RA is where it stops (gravity). For the DEC I have so far just, in darkness, felt when the front edge is parallell with the DEC motor house. The locking of the worms engage then in the exact position.

 

The IPolar tricked me when setting up the first time. Before I got to make the RA rotation, it said "Finished" and displayed the cross for the axis (far down left) From then on my PA was always far off. To avoid this error, you must clear the values in setup, redo the operations but COVER THE IPOLAR until you have rotated about 90 degrees. If you really is obsessed by accuracy, you should redo this several times turning left and right and each time make a note of the axis coordinates, calculate average and use for the future.

 

That's about what I have so far after just having received the new GEM45. More later if I find something worth mentioning.


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#9 Michael Covington

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Posted 03 May 2021 - 09:21 AM

We do need some notes.  I can only write about the mount I actually have (a GEM45 with a low serial number) and am relying on the rest of you to gather the rest of the information.

As to how to use a bubble level to find zero position, I'd have to actually play with the mount a bit before saying.  It's tricky.  I wish iOptron would print index marks on the housing the way Celestron does.



#10 dswtan

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Posted 03 May 2021 - 07:13 PM

Familiar with Losmandy and Celestron CGX, this article is very helpful for my CEM25, which is still a new alien beast to me!



#11 redsan

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Posted 04 May 2021 - 12:42 AM

Sideways is not an option -> do turning the DEC 90 deg and setting it as the Zero position didn't do the trick?



#12 Michael Covington

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Posted 04 May 2021 - 11:28 AM

Sideways is not an option -> do turning the DEC 90 deg and setting it as the Zero position didn't do the trick?

No.  You will not then have full range of movement in declination.  The dec axis cannot swivel around and around -- it has cables inside.



#13 ranvis

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Posted Yesterday, 12:21 PM

Sir, I would like to draw your kind attention to the the 1st Para of "Quirks" which is "If you put the GEM45 mount head on the tripod and don't add the counterweight bar, you'll find that it is top-heavy and will turn upside down when the RA gear lock is released. This is not a risk with the CEM40."

'If you .... DON'T ADD COUNTERWEIGHT BAR.... will turn UPSIDE DOWN' as above is surely correct but I not complete, it also turns upside down even if the CW shaft/bar is attached (as far as I know from your sharing of experience on the FB).

However, an indication of such turning upside down is there in this article under 7th Para - 'The Gear Locks' with the marking 'below' (meaning - elaborately any where in subsequent para). But probably due to oversight that might have not been elaborated further. This is brought to your kind attention for further modification, if required.



#14 ranvis

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Posted Yesterday, 12:21 PM

Proper modification, if any, to the above point may help avoid unexpected damage. 



#15 fielderda

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Posted Yesterday, 05:50 PM

Excellent notes Michael, especially since I'm upgrading from a CGEM mount.

 

I've been waiting for my GEM45 since Dec 26th and hope it will arrive before Christmas!

 



#16 Jason27183

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Posted Yesterday, 07:49 PM

Connection error detected: Dec board

 

Thanks for the article.  I just got a used GEM45, read your article and decided to try the "Search zero position" command.  It spun the RA axis around and found it's "zero" position, but then the DEC control stopped working.  I power cycled the mount and got a "Connection error detected: Dec board" error.  

 

2 hours later I had pulled about 50% of the mount apart and found that the internal wiring had gotten wrapped around the RA axis and pulled the wires out of the main control PC board.  Luckily I was able to fish the wires out from around the RA axis w/o pulling the RA axis out of the mount.  I reconnected them and got it working again.

 

I'm willing to bet that this is going to be a significant problem with this mount.

 

EDIT:  Apparently there are two hard stops for the RA axis.  A screw provides this hard stop for each one.  Apparently one of my hard stop screws is backed out, missing or bent and it didn't stop the RA axis from turning too far.




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