Celestron CGX Reviews and Testing

[toc (Tim)]

Well the last few nights out have been pretty frustrating and unsuccessful. Not really sure where I am going wrong - could be balance I guess, but getting reliable guiding is very difficult. Seems to be acceptable (but still not amazing) when imaging closer to the SCP, but in other locations I am getting jumps on RA (up to 3" or 4" that are ruining subs.

I mentioned this in CN, but PHD2 tells me that I have significant backlash in DEC, which I was not really expecting. Could this simply be a balance issue? Could this somehow affect my RA guiding?

I did have an issue with an unnoticed slipped counter weight that I thought might have done some damage, but I think that is a red herring.

[glend (Glen)]

Originally Posted by toc

Well the last few nights out have been pretty frustrating and unsuccessful. Not really sure where I am going wrong - could be balance I guess, but getting reliable guiding is very difficult. Seems to be acceptable (but still not amazing) when imaging closer to the SCP, but in other locations I am getting jumps on RA (up to 3" or 4" that are ruining subs.

I mentioned this in CN, but PHD2 tells me that I have significant backlash in DEC, which I was not really expecting. Could this simply be a balance issue? Could this somehow affect my RA guiding?

I did have an issue with an unnoticed slipped counter weight that I thought might have done some damage, but I think that is a red herring.

Tim did you check the antibacklash settings? Have a read through that section in the manual, on page 20, it gives you a routine for checking and adjusting it. I have not had a problem with mine so have not checked my settings yet. Importantly it says that for guided imaging the settings might need to be higher than for visual use.

My guide plot is pretty much a flat wiggling line, no jumps at all.

Re balancing, i find the CGX is not as touchy about that as my old NEQ6, but i still balance east heavy usually but not near as much as with the old mount.

I did have a problem with the Az lock bolts that are worth checking. Two of the four bolt holes were not tapped right though, so the bolt was bottoming out and binding, feeling like it was locked down tight when in fact it had not pulled the two plates together. I discussed it with Eric from Celestron and he asked fir a report and photos, which i supplied. Check your Az bolt washers, if you can turn them with a finger the plates are not properly locked and this could cause some movement of the scope or inaccurate alignment.

I have given up on those various CN threads, i think i will stick with this one.
Good luck.

[peter_4059 (Peter)]

I thought the CGX had spring loaded worms. Isn't that meant to eliminate backlash?

[glend (Glen)]

Originally Posted by peter_4059

I thought the CGX had spring loaded worms. Isn't that meant to eliminate backlash?

Yes it has spring loaded worms, but there are still anti-backlash software settings. There are two factors (vertical and horizontal) involved in drive meshing: The spring loaded worm keeps the worm engaged with the ring teeth by applying a constant pressure (about 5lbs), but one with the ability to adapt (compress or extend) in response to very small irregularities in the worm itself - thus it is non-binding. The CGX worm drive belt is also held under tension, eliminating the meshing issues sometimes found in gear driven worms. Some older systems used grub screws to press a pad that pushed the worm onto the ring; the problem with this system is that it was subject to binding if tightened too much as it was non-forgiving of irregularities in the worm or its bearings.
The anti-backlash adjustment is a separate thing, as it deals with the potential gaps between the worm spiral and ring teeth. All gear driven systems have some slack in the grooves/teeth alignment. Anti-backlash settings ensure that when a movement is completed the worm motor drive assumes a position that will allow the next move to happen without a jump at the beginning or the end of the move (in other words it is preparing its position at the meshing interface). In the case of the CGX, the controller buttons are used to adjust the backlash compensation. This means that guiding commands are executed without a jump. The anti-backlash compensation adjustment process is described on page 20 of the manual. It suggests that settings would be different for visual observing and imaging; with visual settings at a value between 20-50, and a higher value needed for imaging guiding.

This represents my understanding of how it works at this time.

[toc (Tim)]

Thanks very much Glen Lots of great info.

[toc (Tim)]

Didn't have much luck solving my DEC backlash, so for now I am just ensuring that I balance the scope with the weight on the mirror side. That said, I am seeing the same level of performance as others wth the CGX, which is good.

[glend (Glen)]

So how are people coming along with their CGXs? I realise the heat has shutdown many of us, myself included. Who has what problems? Any new mounts purchased in the last few weeks? Any "L's" on order?

[toc (Tim)]

Originally Posted by glend

So how are people coming along with their CGXs? I realise the heat has shutdown many if us, myself included. Who has what problems? Any new mounts purchased in the last few weeks? Any "L's" on order?

I am a bit frustrated - i can't get rid of my DEC backlash problems, so I might just not guide in DEC from now on. I tried last night to use the backlash compensation on the handset, but this caused PHD2 to go nuts during the calibration phase. Since the backlash seems dependant on what part of the sky I am imaging I am not sure how that would help anyway. I think I can mange it with balancing, but it is a big pain to have to redo the alignment to re-balance every time I want to image something on the other side of the sky. Btw I can tell the backlash issues are real because I can see phd sending many corrections in DEC before the mount moves. I have adjusted the backlash on the mount itself, but I haven't not been able to reduce it significantly.

Despite this I can occasionally get good results, almost always around the area of ETA carinae or the turancula nebula.

[glend (Glen)]

Originally Posted by toc

I am a bit frustrated - i can't get rid of my DEC backlash problems, so I might just not guide in DEC from now on. I tried last night to use the backlash compensation on the handset, but this caused PHD2 to go nuts during the calibration phase. Since the backlash seems dependant on what part of the sky I am imaging I am not sure how that would help anyway. I think I can mange it with balancing, but it is a big pain to have to redo the alignment to re-balance every time I want to image something on the other side of the sky. Btw I can tell the backlash issues are real because I can see phd sending many corrections in DEC before the mount moves. I have adjusted the backlash on the mount itself, but I haven't not been able to reduce it significantly.

Despite this I can occasionally get good results, almost always around the area of ETA carinae or the turancula nebula.

Tim, out of curiosity, what is your tracking like without guiding? A correctly aligned CGX should be able to hold a target for a long time unguided. Are you running on the factory default settings or have you changed from them? I'd suggest going back to Nextstar default settings if you have moved off them, and testing again. Have you tried a target on the celestial equator, like the Horsehead, there should be very little DEC movement required there. Is your wedge altitude set correctly, have you checked that? I use Metaguide so I don't know much about PHD2. Do you have a place to specifiy the Declination of the target in the setup (Metaguide does)? Also do you have an aggressiveness setting for DEC? I'd ask why is PHD2 sending so many small DEC commands to the mount, or why the mount is ignoring them - sounds like a setting sensitivity issue. I know you asked about this topic on CN as well but there are no Southern Hemisphere CGX owners on CN other than us, but maybe that does not matter.
BTW I don't have your problem. Why not send a PM to Dylan and see if he can offer some advice, he has not been around here in awhile. Alternatively, get onto Celestron's forum and ask there.
If there is some setting you would like to compare with mine just let me know and I will check (but obviously not being a PHD2 user I can only advise on CGX settings).

[toc (Tim)]

Originally Posted by glend

Tim, out of curiosity, what is your tracking like without guiding? A correctly aligned CGX should be able to hold a target for a long time unguided. Are you running on the factory default settings or have you changed from them? I'd suggest going back to Nextstar default settings if you have moved off them, and testing again. Have you tried a target on the celestial equator, like the Horsehead, there should be very little DEC movement required there. Is your wedge altitude set correctly, have you checked that? I use Metaguide so I don't know much about PHD2. Do you have a place to specifiy the Declination of the target in the setup (Metaguide does)? Also do you have an aggressiveness setting for DEC? I'd ask why is PHD2 sending so many small DEC commands to the mount, or why the mount is ignoring them - sounds like a setting sensitivity issue. I know you asked about this topic on CN as well but there are no Southern Hemisphere CGX owners on CN other than us, but maybe that does not matter.
BTW I don't have your problem. Why not send a PM to Dylan and see if he can offer some advice, he has not been around here in awhile. Alternatively, get onto Celestron's forum and ask there.
If there is some setting you would like to compare with mine just let me know and I will check (but obviously not being a PHD2 user I can only advise on CGX settings).

- Generally I can do unguided exposures of about 1 minute - not perfectly round, but roundish. This is at about 1000mm FL.
- Have not touched the factory defaults for guiding.
- Horsehead is not bad for tracking, but the longest I have done the Horse head and M42 is about 3 minutes guided. I start to get some missed subs anytime longer than that. DEC seems ok for these targets, but RA is quite a lot worse.
- Does not appear to be a setting for 'wedge altitude' in PHD2, or any location to specify the declination of the target. I think it just relies on you doing another calibration
- PHD2 does have an Aggressiveness setting - I am using the defaults mostly here - I have played around a bit with it, but didnt see an improvement. I guess the issue is that the backlash is bad enough that PHD2 is sending a correction, and the mount is not moving. I could try to ramp that up I guess.

I think you have the same scope as me - a Skywatcher 190MN. How are you balancing the scope? do you bias it one way or the other, or leave it perfectly balanced?

Thanks for the help! If I get a chance tonight, I will forgo any imaging, and just fiddle.

[glend (Glen)]

Originally Posted by toc

- Generally I can do unguided exposures of about 1 minute - not perfectly round, but roundish. This is at about 1000mm FL.
- Have not touched the factory defaults for guiding.
- Horsehead is not bad for tracking, but the longest I have done the Horse head and M42 is about 3 minutes guided. I start to get some missed subs anytime longer than that. DEC seems ok for these targets, but RA is quite a lot worse.
- Does not appear to be a setting for 'wedge altitude' in PHD2, or any location to specify the declination of the target. I think it just relies on you doing another calibration
- PHD2 does have an Aggressiveness setting - I am using the defaults mostly here - I have played around a bit with it, but didnt see an improvement. I guess the issue is that the backlash is bad enough that PHD2 is sending a correction, and the mount is not moving. I could try to ramp that up I guess.

I think you have the same scope as me - a Skywatcher 190MN. How are you balancing the scope? do you bias it one way or the other, or leave it perfectly balanced?

Thanks for the help! If I get a chance tonight, I will forgo any imaging, and just fiddle.

Yes i have an MN190, and i am actually in the middle of imaging NGC3324 (Gabriel Mistral Neb). Waiting for the moon to get out of the way so i can shoot Oiii. I balance it east heavy on RA, and rear heavy on DEC - just a little bit. It does not need as much heaviness as the old EQ6. I get nice flat guide plots for eastern targets. I am shooting 5 min narrowband subs. My PA is sitting on 9 arc secs off the SCP.

Dave (Syscore) on CN has just finished testing his CGX, worth a read in his new thread. He is very happy and has put up some 60" unguided subs as examples.

[Wombat (Wayne)]

Originally Posted by Wombat

Hi Glen
Got in touch with Bintel and have been told to ring monday because that is when their tech "Don" gets back from holidays. So I will ring first thing monday.
Wayne

Mount now on it's way to US to be repaired at Celestron's expense, apparently no one in Australia knows how to do repairs on these mounts as they are pretty well straight out of factory.

[glend (Glen)]

Originally Posted by Wombat

Mount now on it's way to US to be repaired at Celestron's expense, apparently no one in Australia knows how to do repairs on these mounts as they are pretty well straight out of factory.

Gee that's ashame Wayne. I assume the techs at Celestron California will be looking at it and that is where any US returns go. Who is covering the shipping cost, hope its not by boat. I hopevthey only sent the head unit.

[Wombat (Wayne)]

Originally Posted by glend

Gee that's ashame Wayne. I assume the techs at Celestron California will be looking at it and that is where any US returns go. Who is covering the shipping cost, hope its not by boat. I hopevthey only sent the head unit.

Hi Glen,
The mount head only goes to US tripod stays. Celestron is picking up the shipping cost, and I do believe it is air freight as it went through Celestron's DHL account.

[glend (Glen)]

Full page back cover advert for the CGX in the Australian Sky & Telescope (issue 100) which arrived in the post this morning.

[toc (Tim)]

You are probably sick of seeing my annoying posts, but I have a minor update to my DEC saga

I think I have the culprit... (but I am waiting for some comment from Celestron)
I took the cover off the DEC housing and looked at the belt and gears when moving. There is a noticeable wobble on the gear that is connected to the motor. I thought that perhaps it was not seated correctly, but it looks like to me that the hole in the gear has been drilled on an angle. When I reversed the direction I could see that at times the slack on the belt (presumably because of the uneven pressure) meant that it there was a bit of a delay in driving the gear. This might not necessarily be a huge drama, but thought I would feed this back just in case others see similar issues.

Part of me wants to return the mount for repair, but I am loathed to have to return the mount to the US, and be without a mount for 3 months because of one 50 cent gear. What would be awesome is if they could send me a replacement - it would be a very simple job to swap the part over. I will let you know what mr C says

[glend (Glen)]

Tim have you communicated directly with Erik the Celestron product engineer? I have his email address if you want it, i can PM it to you. He asked me to send him some photos of the problem i had with the base Az holes not being tapped all the way through. He certainly takes an interest. If you post your comments about the DEC gear on CN he will probably see it. Put some photos up or a video on utube of the wobble

Edit. Tim i have sent you the email address via PM..

[toc (Tim)]

Originally Posted by glend

Tim have you communicated directly with Erik the Celestron product engineer? I have his email address if you want it, i can PM it to you. He asked me to send him some photos of the problem i had with the base Az holes not being tapped all the way through. He certainly takes an interest. If you post your comments about the DEC gear on CN he will probably see it. Put some photos up or a video on utube of the wobble

Edit. Tim i have sent you the email address via PM..

Thanks

[glend (Glen)]

Perhaps contact Dylan as well, he is suppose to be a Team Celestron rep, whatever that means, and was quick to spuik the mount on launch but has pretty much disappeared since then. I would like to hear from him in this thread.

[dylan_odonnell (Dylan)]

Hi guys!

I haven't read through this thread yet sorry, I've been out of action because my beloved CGX also had to be sent away like Wayne's for repair.

Glen suggested that I may shoulder some responsibility for problems others may have had with the 5 that were sold early from Bintel because I spilled the beans they were in the country before their official release. If that is the case, I do apologise. I did preface my original thread by saying something like "(Disclaimer, I'm on "Team Celestron" so am an ambassador of sorts for them, and I work as a third party with Bintel. However neither of these companies pay me for comment and I pay for my own gear like anyone, though I do get discounts and heads up on new stuff from time to time.)" (that's a copy and paste from what I said on Cloudy Nights)

I shared my results to everyone who asked for them with graphs and logs etc as nobody else was doing so at the time. They were good results, and ironically my faulty CGX worked great. It just had an intermittent shudder (which I also described on cloudy nights) that was fixed by slowing the default slew speed down.

But a new mount is a new mount, and like you guys, I paid for a new mount and went back to Bintel and Celestron did the right thing and took it back at their cost. Which is the same for Wayne I believe.

I don't have any more info than you guys, and I don't work for Celestron. I'm not a social media influencer as I don't get paid for comment. I said it before "If it sucks - I'll tell you!".

Anyway .. I'm BACK thank god. My wife was getting jack of me playing heavy metal again while I missed a few good imaging weekends with no mount. The CGX is back in the obs and I've summoned the clouds forthwith.

I'm on "Team Celestron" simply as a user. A fan perhaps, but also a big user of their gear. I write for their website and I'll be speaking for them (unpaid) at the world science festival in Brisbane with Dr Alan Duffy, Dr Lisa Harvey-Smith and Dr Duane Hamacher on March 25th for a free star gazing evening. You should all come

I've also put together the Star Stuff event, which is now sponsored by Celestron and Bintel and ESA (among others), with zero funding or support from government or academia. In fact, I'm paying for it all out of my own wallet because that's how much of a space nerd/fan I am. You should come to that too! ( https://www.starstuff.com.au )

I hope that clears it up and sorry to hear about any issues other may had. I believe this first batch was literally 5/50 that came straight off the factory floor and were shipped internationally. I only know of 2 returns so far and apparently all of the UK stock was fine with no returns. But I'm not Celestron, if you have an issue - discuss it with your Authorised dealer (Bintel) first as they have more weight with Celestron than we do. That's what I did.

I reckon those first few did have factory-first / early-adopter / manufacturing issues that Celestron has resolved. Still the best mount I've ever had.

d