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Testing and setting up a new iOptron CEM60

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#1 Ragnar1

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Posted 16 February 2020 - 02:37 PM

Hi All,

 

I have a new iOptron CEM60 and tri-pier on order and they may be arriving within a week. I plan to use it mainly for astrophotography. I am relatively new to astrophotography (been doing it for about 5 months using an iOptron skyguider pro; and have a very small amount of experience with guiding). I read the forum posts and internet articles on the CEM60, and would like to make sure I test the important aspects of the mount within the 30 day return window. I collected the following tips/tricks/testing procedures: 

 

Setup/tips:

  1. Read manuals before receiving mount
  2. Order second counterweight to balance 8" SCT
  3. Practice using magnetic clutches/switches
  4. Put teflon tape under mount to ease azimuth adjusments
  5. Order computer control cable: Ioptron Equatorial Telescope Upgrade Control Console Cable Coding Line Ieq30pro RS232 to 4P4C RJ9 (6FT, for Ioptron) - this seems less bulky/complicated and Amazon reviews say it works with the CEM60
    1. Alternatively, could order the USB2.0 to Serial (9-pin) DB-9 RS-232 adapter cable (FTDI chipset) for computer control - may just order the iOptron one
  6. Possible sideways balance fix: https://www.cloudyni...fix-for-cem-60/

Regarding testing, my current thinking is:

 

Testing (indoor/daytime testing possible):

  1. Listen for any grinding or stalling sounds when slewing, with different loads attached
  2. Check whether polar scope is coaxial with RA axis and fix if not (http://www.ioptron.c...e_Alignment.pdf)
  3. Can I test computer control by slewing to a target and checking it's pointing approximately in the right direction (pretending it's polar aligned)?

Testing (clear skies needed):

 

  1. Set PhD2 guide rate to 0.80 and calibration step to 3000 (I read that this is what works for the CEM60) UPDATE: removed this - does not seem accurate based on users' experience
  2. Test RMS error (I have a ZWO ASI224MC which I am planning to use as a guide cam, with a Nikon d5300 as the imaging cam):
    1. I assume it makes sense to test both with and without guiding. Is this right?
    2. Is it possible to measure RMS error in PhD2 without sending guiding signals to the scope? If so, how?
    3. I assume it should be tested with different loads - I have an 8" SCT (Celestron non-Edge HD) and 72mm refractor. I know the non-Edge HD SCT is suboptimal for astrophotography but I'm only planning to use it for testing at this point
    4. When testing guided performance, does the focal length of the guide scope matter for the purposes of testing? (I realize there is a separate consideration about matching the guide scope/camera to the imaging scope/camera, but here I'm asking about testing the mount's performance.) I have 50mm aperture/190mm focal length and 72mm aperture/430mm focal length scopes that could be used as guide scopes (for the 72mm scope and the 8" SCT respectively)
    5. What RMS RA/Dec error is acceptable?

Is there anything else I should test or should have thought of? Or any other tips/tricks to be prepared when the mount/tri-pier arrive? Thanks.


Edited by Ragnar1, 16 February 2020 - 10:04 PM.


#2 eyeoftexas  Happy Birthday!

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Posted 16 February 2020 - 03:00 PM

1. Download PS Align Pro app for polar alignment.  (or)

2. Buy PoleMaster for polar alignment

3. Have fun.smile.gif



#3 zakry3323

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Posted 16 February 2020 - 03:37 PM

Tip #1 - no need to tighten the azimuth compression caps beyond lightly hand tight, a good balance will keep it from moving, and overtightening in the slightest may throw off your polar alignment.

 

Tip #2 - leave the altitude adjustment clamps loose regardless of whether the mount is under load or not, and take care that the clamping "tabs" don't catch on the slotted housing, as mine did. Doing so will cause gouging- thankfully only cosmetic in my case. I needed to remove and deburr the edges of the tabs myself, they wanted to catch regardless of the tension I put on them, and I still keep an eye on them when adjusting altitude. 

 

IMG_20200205_101822.jpg

 

Tip #3 - The CEM60 lends itself very well to modification for having a PC mounted on the OTA. All wires can be removed and replaced so that you can have power and/or data right at the saddle, allowing you to eliminate hanging wires. Several good videos on youtube, this one got me started, though I did a few things differently myself! https://www.youtube....=Oy8ilrOm3vA&t=

Good luck and enjoy!  



#4 rgsalinger

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Posted 16 February 2020 - 03:54 PM

I think that, unless you use an OAG, you should be prepared for mediocre results even if the guiding looks good. You will have some degree of differential flexure as the mirror moves with gravity and the guide scope (which is attached to the OTA and not the mirror) doesn't move. You should also realize that you will not get round stars in the corners- the scope's imaging circle is way smaller and an APS-C chip. Don't let any of this disappoint you, just note it, work out what it's all coming from and move on. 

 

I don't know where that .8 guide speed recommendation is coming from. I'd go with whatever iOptron recommends rather than experiment. Calibrate the guider (after focusing it) at the meridian/equator junction for best results. Don't skip building a dark library for the guide camera. 

 

Buy a copy of a book and read it. I like the Deep Sky Imaging Primer but some should recommend others that are also excellent.

 

If you can see Polaris then get the pro copy of Sharpcap and use that rather than spending mucho bucks on a polemaster. If you can't see Polaris pay close attention to the assisted Polar Alignment that's in PHD2.6. It works but you need to understand how to do a drift alignment.

 

There's no need to use an ST4 cable. Use "ASCOM" guiding instead. That's one less cable to trip over and you will not need to recalibrate on every target. In fact you will not need to recalibrate the guider at all if you keep the guide scope and camera attached to the OTA.

 

Get a good imaging software package. I suggest Sequence Generator Pro or Voyager. Both will need helper programs but both work very well. I've used both but just to see what's what. 

 

Looks like you also need a good USB hub and a Bahtinov mask. The hub will help with cabling. The mask is an absolute requirement if you want accurate focus but don't want to spend a lot of money on it. 

 

See if there's a local club with an imaging group. Given the popularity of this mount it is very likely that you will find others using it and a mentor. 

 

You can test out slewing indoors but you won't know if it's accurate or not. Plate solving - which are both supported with helper programs in Voyager and SGP are the best thing that's happened in AP in a long time.

 

Rgrds-Ross


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#5 gotak

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Posted 16 February 2020 - 07:46 PM

Get ready offset weigh solutions to achieve perfect balance. You need to offset things like cameras or other bits hanging off the side of the scope.

If you don't achieve perfect balance the mount is likely to have some random 1-2" deviations cause my imbalance.

Once you have it prefectly done you should tv enable to unlock both worms and leave the scope in any RA or DEC orientation and it would stay there.

Both RA and DEC are sensitive to balance. In DEC if balance is biased in any way you'll see it in results that looks like backlash.

#6 Ragnar1

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Posted 16 February 2020 - 07:57 PM

Hi All,

 

Thanks for the suggestions.

 

Eyeoftexas, I have a Sharpcap Pro license for use with the SkyGuider Pro I currently use. I'm planning to try it with the CEM60 and see how it goes.

 

Zakry3323, thanks for those hands-on tips. I'll add them to the list once I've gone through the setup/testing.

 

Ross, I found the PHD2 settings suggestion here: http://www.opticstar.../CEM60_Tips.pdf. I will plan to get the OAG for SCTs eventually. For now my primary imaging scope is an AT72EDii, but I want to test the mount with the SCT + AT72EDii to test how it performs with a bit of load - in case some problems show up with heavier loads.  I understand that even if I don't get good images from the SCT, I should still be able to evaluate mount performance by using PhD2 looking through the guide cam - is this correct? I do have Bahtinov masks for both scopes. Regarding the cable - I'm not very clear on the connections. My understanding is that ASCOM is a driver/piece of software. How would the computer be connected to the scope when using ASCOM - isn't it via the RJ9 port on the mount?


Edited by Ragnar1, 16 February 2020 - 08:02 PM.

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#7 Ragnar1

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Posted 16 February 2020 - 08:00 PM

Gotak, thanks for the note. I'll try to get balance as close to perfect as possible. As a point of curiosity, is a slightly off-balance setup more of an issue for this mount than for other mounts with similar weight capacity?



#8 OldManSky

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Posted 16 February 2020 - 08:15 PM

Like Ross, I don't know where you read to use 0.8x sidereal guide rate.  I've been using 0.5x since I got mine, with excellent results (all sessions so far under 0.5" RMS error, most are around 0.3").

 

You should receive a PE printout with the mount -- that will give you a rough idea of your particular mount's periodic error.  It will most likely be well under 10" (mine was about +- 3").  Essentially any PE is fine as long as it's smooth and can be guided out as far as imaging goes, but of course the lower and smoother the better.  The focal length of the guidescope won't matter much, PHD2 will let you know what your errors are.

 

Enjoy the new mount.  I'm very happy with mine (2 months now). :)



#9 gotak

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Posted 16 February 2020 - 08:56 PM

Gotak, thanks for the note. I'll try to get balance as close to perfect as possible. As a point of curiosity, is a slightly off-balance setup more of an issue for this mount than for other mounts with similar weight capacity?


For DEC it seems sensitive. I think this is due to the spring loading on the worm. It removes backlash but it also gives abit if the balance is wrong and so looks like backlash.

For RA it's the same as any other mounts. Just that if you are balanced with spring loaded worms you don't need things like east heavy biasing. For worm driven mounts when the balance is biased towards the rotation on RA, you end up with a slip and catch behaviour in the worm/wheel interface. And that shows up as sudden deviations. When it's biased against that RA rotation you get a smooth movement. This is why you have the east heavy setting people use on some mounts to take up backlash. On spring loaded system just do perfect balance and you don't have to mess around with weights at meridian flips.
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#10 RaulTheRat

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Posted 16 February 2020 - 09:20 PM

Yeah since you've covered a lot and seem to know what to check, I'll also say balance - you can get a really great balance with these because of the worms disengaging, and you should IMO if you want the best performance. I need both off-axis balance weights on the OTA (so that it'll balance both horizontally and vertically in Dec), then also even after RA balance is perfect (ie on either side of the pier the OTA and counterweights are balanced with the bar horizonal) I still get a rotation (clockwise looking from the front) of RA anywhere near the vertical counterweight bar position (no matter which side of the pier the scope/weights are on its still clockwise) meaning that the whole scope must be off centre (presumably the saddle isn't centred but I haven't checked) so I also need an M12 bolt with washers screwed into one of the counterweights which iOptron helpfully threaded for this purpose to be able to eliminate that torque and get the thing balanced perfectly in absolutely any position.

#11 Ragnar1

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Posted 16 February 2020 - 10:11 PM

OldManSky, thanks. I got the suggestion here: http://www.opticstar.../CEM60_Tips.pdf. But given the opposing data points from you and Ross, I've updated the original post to remove that suggestion.

 

Gotak and RaulTheRat, thanks for the balancing info. I'll try incorporating your techniques to get precise balance.



#12 ajaxuk

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Posted 17 February 2020 - 01:52 AM

Hi Ragnar1

 

Like you, I have just made the move from the SkyGuider pro to CEM60. 

 

On top of the points above:

 

I have found that my cables for USB and 12v power that feed the USB and additional power have a tendency to wiggle out when slewing. Took me a little while to figure out what was happening! It could just be my cable connectors are not very good, but keep an eye out for it.

 

The illluminated built-in polar scope is good, I would also do the finer adjustment using SharpCap pro.

 

After calibrating, use Guiding Assistant for PHD2 and let it run for 5-10 minutes, this will give you feedback can also test the DEC backlash. It may also give some recommendations for parameter changes. I apply these.

 

Enjoy the mount!



#13 Ragnar1

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Posted 17 February 2020 - 10:58 AM

Ajaxuk, thanks. I'll keep those tips in mind.



#14 Drew57

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Posted 17 February 2020 - 02:50 PM

Just completed bench test for my new CEM60 and so far seems like a nice mount. Soldered up new harnesses for it & the iEQ30pro just waiting on another Kendrick power cord. Gonna have to order the Tri-Pier as well, oh well. But it solves most of my troubles.

 

So far I'm not set up for advanced astrophotography 'kinda scared of it! But I did get an SBIG STi monochrome way back when, figure it should work ok as guider with the Kowa lens kit (main scope is f=731). Just have a 2" DSLR adapter & accessories enough to do some basic stuff.

Not keen on removing the factory cable management so ran 12V 5AMP power and 5V USB2 to the input ring, seems pretty darn nice to me. If I could route the Kendrick power through the ring up to the saddle front panel that would be sweet so looking into that as long as clean pro install possible. Edit: adding up the amps for heater strips & camera plenty of power the Digifire 8 can run off the saddle the way things are now. So I'll terminate the Kendrick cable to power plug instead of powerpoles for now, then its all free-spinning! 

 

I thought the picture was funny as the guidecam looks like how 'ol Mack The Newt will feel up on its new base! The CEM60 will carry me well into the future.

 

cem_bt.jpg


Edited by Drew57, 17 February 2020 - 03:36 PM.


#15 Ragnar1

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Posted 17 February 2020 - 10:17 PM

Drew57, thanks for the photo. The CEM60 did feel like overkill for my measly AT72EDii (the only "real" imaging scope I have right now - don't have high hopes from my 8" SCT), but I figured it allows me room to grow.

 

The astrophotography I've done so far is so simple, I've never had to do any kind of cable management. Looking forward to seeing what I can accomplish with this mount.



#16 rgsalinger

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Posted 17 February 2020 - 10:53 PM

I know nothing about "opticstar" but I have to say that if you need to set the guide rate to 80 percent of sidereal to get a good PHD calibration then by all means do so. I doubt that it will hurt anything. I also have to say that it doesn't make sense to me. If I thought that it was correct I'd post it as a problem on the PHD forum. (I have not searched.) The key to a good calibration is to do it near the intersection of the meridian and the celestial equator and to get the step size and number of steps correct. 

 

You should be using the through the mount cabling to the extent that you can. The fewer cables between the computer and the mount the better. All of my power and USB connections are held in tension by using a bit of stretchy electrical tape between them and the saddle plate (on the 120). That may not be practical if you are setting up each night but I try (I really do) not to touch my systems unless it's unavoidable. 

Rgrds-Ross



#17 Ragnar1

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Posted 18 February 2020 - 11:45 PM

Ross, thanks. I'm in tune with the philosophy of minimizing cable clutter and avoiding re-wiring anything. Will try it out.




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