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CGEM -- first impressions

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#26 jmiele

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Posted 04 May 2011 - 10:46 AM

Just to add to that - Celestrons packaging is as BAD as it gets. They ship a $4500 C-14 in less than 100lb burst strength cardboard. They only support and protect the tube at the ends with foam. You can push the box with your hands until you hit the tube at the center. If you are to use the same box again to send to someone else it will fail. Then everyone is mad at UPS/FedEx when they won't pay a claim. Joe

#27 EFT

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Posted 04 May 2011 - 11:03 AM

IMO, shipping mounts and telescope long distances is a fact of life. If manufaturers are making gear that cannot be shipped and still perform to a certain level, then that is a problem. Upon arrival, ANY of the gear from ANY maker, should perform to the documented spec. And it's NOT the carriers fault. We too often want to blame UPS and FEDEX. Poor design and packaging are the main reason things arrive out of spec. Can you ship Eggs via UPS.....? Sure you can, but not in the catron you buy at the supermarket. But as we learned in school, you can make a carton or package to support dropping the egg from the 2nd floor window without it breaking. Telescope and mount makers need to make gear and packaging the can live within the current delivery systems because we aren't going to pick everything up at the shop :)

3,4 maybe 5 cents :)

Joe


Joe,

You are generally correct and the CGEM in fact comes in a very good shipping box and packing. One of the best and far better than styrofoam packing. And for the most part, when a mount arrives it does work unless it has had very wrough treatment. I have yet to get a CGEM damaged in shipping. However, two things were different about this mount. First, it was not coming from the manufacturer or the dealer, it was coming from the original owner. Second, the mount had been previously adjusted to mesh the gears very tightly. That is not how they come from the manufacturer. In general, the adjustment of a mount from a manufacturer is loose enough to allow for shipment to different environments where the expansion and contraction of the different metals can affect the functioning of the mount. When you change those adjustments or have them changed in order to tighten up the mount you need to realize that fine readjustment may be necessary when it travels or is shipped long distances.

I am located in Phoenix, Arizona and I find that when I really tighten a mount up and then send to places with much different climates (like cold Canada or very humid Louisiana or Florida) a little fine readjustment may be necessary when the mount arrives at its destination because things may have either tighten or loosened up in the process. This is probably less the case with higher quality mounts that use flat metal plate machined construction, but with mounts that mix machined and cast metal parts I see it fairly often. For the most part, I don't think that it is attributable to handling in shipping. In general most mounts are actually pretty tough pieces of equipment that can handle a fair amount of abuse in shipping and tavelling without and real problems. About the only shipping damage I ever see, even with poorly packed mounts, is a bent adjustment bolt or a cracked plastic housing on a lower end mount and I get mounts from and send them to everywhere in the country and Canada.

#28 Mike Wiles

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Posted 04 May 2011 - 11:09 AM

My CGEM has performed admirably in the six months that I've owned it. I've set it up and taken it down perhaps 30 times in that period and I've had no issues. I do a 2 star alignment, and then 4 calibration stars. After that, I use the all star polar alignment routine to nail down the polar alignment. Many people will turn off the CGEM and start all over at this point. I simply slew to another bright star, sync to that star and get busy imaging.

The mount tracks well, autoguides well and does everything I ask of it every time I do it. I couldn't be happier with it - especially for what it cost.

#29 EFT

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Posted 04 May 2011 - 11:13 AM

Just to add to that - Celestrons packaging is as BAD as it gets. They ship a $4500 C-14 in less than 100lb burst strength cardboard. They only support and protect the tube at the ends with foam. You can push the box with your hands until you hit the tube at the center. If you are to use the same box again to send to someone else it will fail. Then everyone is mad at UPS/FedEx when they won't pay a claim. Joe


I haven't seen a C14 in the box but all of the C11s I have seen came in double boxes that were pretty good although not as good as the mount boxes. They use to come packed in the expanding foam that was better though. Some manufacturers use that stuff and it works pretty well. Considering the size and wieght of the C14 I would definitely want that double boxed and probably center supported.

If you ever need to ship something that was poorly boxed in the first place, that is the only time I will go to a pack-and-ship place to have them use the expanding foam material for packing. But you have to watch how they do it and make sure it is done correctly. For the most part I never recommend allowing someone else to pack your gear since they will just throw it in a box with peanuts and call it good. That is how gear gets broken in shipping. Peanuts are OK as long as the item being shipped is also very well wrapped in bubble wrap and cushioned with the peanuts packed tightly so that the item cannot just bounce around in the box.

#30 amys

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Posted 04 May 2011 - 11:26 AM

Just a quick set up question: how much should you tighten the RA and DEC knobs after balancing? With my Sphinx, I make them good and tight but every mount is different.

#31 BCB

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Posted 05 May 2011 - 04:38 AM

Make em tight.. Wont hurt a thing. The worm gears are double bearing (top and bottom) unlike the cg5 style of just smooth inner mating surfaces.

#32 amys

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Posted 05 May 2011 - 07:07 AM

OK, thanks. I'll pass that along.

#33 EFT

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Posted 05 May 2011 - 08:05 AM

Just a quick set up question: how much should you tighten the RA and DEC knobs after balancing? With my Sphinx, I make them good and tight but every mount is different.


The clutches on the Sphinx work much differently from the CGEM. If you clamp down on the CGEM clutches you will slightly deform the ring gears and the mount will run very poorly due to the gears no longer being round. You need to use as little pressure as possible on the CGEM clutches.

#34 clchildress

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Posted 05 May 2011 - 08:20 AM

Just a quick set up question: how much should you tighten the RA and DEC knobs after balancing? With my Sphinx, I make them good and tight but every mount is different.


The clutches on the Sphinx work much differently from the CGEM. If you clamp down on the CGEM clutches you will slightly deform the ring gears and the mount will run very poorly due to the gears no longer being round. You need to use as little pressure as possible on the CGEM clutches.


That's good information to have! I just acquired a used CGEM and the last thing I'd want to do is damage it, ham-fist style.

#35 EFT

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Posted 05 May 2011 - 08:35 AM

That's good information to have! I just acquired a used CGEM and the last thing I'd want to do is damage it, ham-fist style.


The gears seem to spring back reasonably well so if you have been overtightening the clutches you are probably OK. Its just that you can really tell when the mount is running with oval shaped gears. Two opposite quarters of the gear will run smooth and loose while the other quarters will bind and it is only temporary PE since the positions will change whenever you release the clutches. Even in these mounts changes of 100ths or 1000ths of an inch can make a significant difference sometimes.

#36 jrbarnett

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Posted 05 May 2011 - 04:50 PM

On the other hand, I've never had to touch the Atlas in this regard. Mine is many, many years old, is well traveled (including many off pavement dark sky trips) and has not been treated gently in any way.

I find it strange that a much younger and less traveled CGEM would manifest this issue unless caused by human intervention, when a much older, untouched, more abused Atlas would not. Would it be legit to use Locktite blue on these screws to avoid having to deal with the loosening screw issue in the future?

- Jim

#37 Phil Cowell

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Posted 05 May 2011 - 04:53 PM

Can you ship Eggs via UPS.....? Sure you can, but not in the catron you buy at the supermarket. But as we learned in school, you can make a carton or package to support dropping the egg from the 2nd floor window without it breaking. Joe


Joe you can put a house brick in 3 meters of packing and foam. Even that stuff they show on the ads for pillows that stop stop eggs being broken and you'll have house brick dust by the time it arrives. They teach these guys how to trash military survive space flight stuff.
The test sheets read:
1, 150' drop test....Passed
2, 60G edge impact....Passed
3, 60MPH vehicle impact.....Passed
4, Shoot from chicken cannon into aircraft windscreen.....Passed
5, Fedex, UPS test 500mile delivery test....Failed both carriers, nothing but dust in both containers.

They could trash anything and take pride in it.

#38 Phil Cowell

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Posted 05 May 2011 - 04:55 PM

UPS/Fedex have the same logo now....

The jobs not done until any delivered product won't run.

#39 EFT

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Posted 05 May 2011 - 05:16 PM

On the other hand, I've never had to touch the Atlas in this regard. Mine is many, many years old, is well traveled (including many off pavement dark sky trips) and has not been treated gently in any way.

I find it strange that a much younger and less traveled CGEM would manifest this issue unless caused by human intervention, when a much older, untouched, more abused Atlas would not. Would it be legit to use Locktite blue on these screws to avoid having to deal with the loosening screw issue in the future?

- Jim


If someone has a persistent problem with the worm gear housing bolts loosening up, then some medium strength (usually blue) threadlock on these bolts is fine. However, I have generally not heard of people having this problem. It is more common, when a mount is set very tight and shipped to a different climate, that a little fine adjustment may be necessary sometimes to counter the effects of differential expansion and contraction in the mount that may cause the gears to become a little more tight or loose (you probably won't notice loose but you will definitely notice tight).

#40 jrbarnett

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Posted 05 May 2011 - 06:20 PM

Thanks Ed. Makes sense.

Regards,

Jim

#41 deepskyguy

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Posted 05 May 2011 - 10:19 PM

One other question regarding the clutches. I always leave my mount together and carry it out in the back yard. When not in use, I leave it with the clutches disengaged. What would happen if the clutches were engaged and the mount got bumped or someone moved either the RA or DEC? Would that damage the gears?

Thanks,
DSG

#42 EFT

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Posted 05 May 2011 - 11:10 PM

One other question regarding the clutches. I always leave my mount together and carry it out in the back yard. When not in use, I leave it with the clutches disengaged. What would happen if the clutches were engaged and the mount got bumped or someone moved either the RA or DEC? Would that damage the gears?

Thanks,
DSG


How a mount will do with the clutches engaged varies with the mount to some extent. I worry less about an Atlas being bumped with the clutches engaged than I do a CGEM because the Atlas has only 3 large-toothed gears between the motor and the worm whereas the CGEM has about 8 gears between the motor and the worm. However, realistically, the greatest danger is to the worm and ring gears and the clutches would have to be very tight to not slip at all which is not very likely. Overall, there is probably not much to worry about with the CGEM and Atlas mounts and I have seen them shipped with the clutches both engaged and disengaged without damage. I think Celestron recommends shipping with the clutches disengaged but the mount is much more difficult to carry or even get in and out of the box with the clutches disengaged. I usually have to engage the clutches to place the mount in the box or take it out and then release them after it is in the box.

In a mount that has spring loaded worm gears the risk of doing damage to the worm wheels with the cluches engaged may be greater because, rather than the gears being locked together and the clutches slipping, the worm gear might slip up and rachet across the top of the worm wheel doing damage to one or both of the gears.

#43 jrbarnett

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Posted 06 May 2011 - 01:49 PM

Ed:

You said something interesting:

"...because the Atlas has only 3 large-toothed gears between the motor and the worm whereas the CGEM has about 8 gears between the motor and the worm."

Folks often assume that these are very similar mounts, other than cosmetics and motor type. It sounds like that may not be wholly accurate. Any idea why Celestron would opt for so many more gears in the drive train than Orion/Sky Watcher?

Are there advantages (real or theoretical) to either approach?

Thanks!

- Jim

#44 EFT

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Posted 06 May 2011 - 02:11 PM

Ed:

You said something interesting:

"...because the Atlas has only 3 large-toothed gears between the motor and the worm whereas the CGEM has about 8 gears between the motor and the worm."

Folks often assume that these are very similar mounts, other than cosmetics and motor type. It sounds like that may not be wholly accurate. Any idea why Celestron would opt for so many more gears in the drive train than Orion/Sky Watcher?

Are there advantages (real or theoretical) to either approach?

Thanks!

- Jim


The difference between the two mounts is due to the motors used. The Atlas uses stepper motors which require only a motor spur, an idler gear and a worm spur. The CGEM uses servo motors which have a motor gear box which contains 6 gears if I remember correctly, a motor spur and a worm spur.

There are advantages and disadvantages to both types of motor. The servo/encoder combination has a better idea of its position than the stepper motor without an encoder that relies on counting the steps (or microsteps) made. However, the stepper is far more robust and difficult to damage since if the mount gets jammed, the motor just starts to skip, which sounds awful but doesn't cause damage. The servo motor on the hand is far more delicate and if the mount jams the system applies increase power to the motor to overcome the jam which can result in the stripping of gears inside the gearbox.

When it comes down to it, personal preference for the sound and feel of the motors is often what decides the debate. I prefer the sound of servos over steppers but I can't really say that one works better than the other. The greatest difference between these two mounts is the hand controller.

#45 delgado39

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Posted 06 May 2011 - 07:33 PM

Would like to add that Ed helped me through the problem I experienced with my used CGEM when the DEC axis was binding on a high spot in the gears. Reported earlier in this thread by JRBarnett. Following Ed's worm gear adjustment directions and "taking my time" the issue was resolved; which I'm greatly relieved. After a 2 star - 4 star calibration alignment and using the precise GOTO feature, I was able to GOTO stars with a 5mm eyepiece and have them appear in the FOV. Amazing. Ed's a great resource in understanding CGEMs. My mount which he hypertuned for the original owner is incredibly well balanced.

#46 bob midiri

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Posted 07 May 2011 - 05:26 AM

Amy I received mine last spring. After a few weeks I started getting errors on the HC. Celestron exchanged HC with me and its been a pleasure to use ever since. I love it, and how it handles my C6R. I do a 2 star western alignment with 3 caleb stars in the east, and its goto's are just dead on. Great mount for the money. Bob

#47 amys

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Posted 07 May 2011 - 06:15 AM

I'm looking forward to having another opportunity to use it. In the meantime, I'll be checking to see if my Celestron CG-5 hand controller is flash upgradable and if so, will probably order the NexSXW board for my Sphinx. Why not take advantage of clearly superior software if I can, right? :grin: Especially with my small scopes, knowing that the go-tos are accurate will help me find those really faint fuzzies.

#48 BCB

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Posted 07 May 2011 - 06:34 AM

I'm looking forward to having another opportunity to use it. In the meantime, I'll be checking to see if my Celestron CG-5 hand controller is flash upgradable and if so, will probably order the NexSXW board for my Sphinx. Why not take advantage of clearly superior software if I can, right? :grin: Especially with my small scopes, knowing that the go-tos are accurate will help me find those really faint fuzzies.


Agreed.. Up here, we need all the help we can get with our light pollution.. I'm a few miles off the 95 corridor and ill tell ya, some nights, the southern skys BURIED in it..






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