Well I'm up to day four with this my first GoTo mount. Accuracy is variable and lacking - at present its like daylight saving has confused things and its pointing an hour behind where everything currently is or something, plus more pointing errors.
Just some initial observations about the mount and manual.
1. The mount arrives with the Alignment peg placed between two legs rather than over one, against Celestron's advice - increasing its turning moment and chance of making a nasty whoopsie all the more likely.
2. The manual probably should suggest the following:
Understand where 20 or so most prominent alignment guidestars are, else if the set up GoTo is wrong you will not have the knowledge to align the scope to the correct stars
realise the design we choose means the dec motor can often knock into the RA motor housing - possibly stuffing up alignment? whenever you get to close to Alpha Centuari.
in fact about a third to half my GoTo attempts failed outright to complete due to the motors colliding, is this a dud design like a car that can go forwards or back, right in either direction but left only in reverse? I'm wondering if this lack of clearance is simply a fatal design flaw doomed to kill half the GoTos you could issue.
the scope doesn't understand this last point, and if there are two options to get to a new Goto point - bet your bottom dollar that it chooses the one that causes Dec motor housing to have a clunk and stop rather than take the obstruction free route
same with the the 90 degree prisms hitting the tripod leg on some viewing angles cause of the travel route it favours
3. If you point to an incorrect wrong star as one of your three alignment stars you can't really undo, you have to re-boot and start from scratch again.
4. About 50% of the time on goto first alignment star it points below the horizon which is just plain wierd!
5. Accuracy - well its about three finger knuckles behind where it should be on Spica and Jupiter.
6. Quick align on Jupiter then move teh scope and search for Jupiter again fails. With a small move doesn't the mount is unable to find Jupiter - the one alignment star that you choose 30 seconds earlier.
7. The manual has no trouble shooting section
8. The manual has no first use diagnostic to give feedback on how to check your scope is functioning correctly (no benchmark diagnostic tests)
So right now I don't know if its a lemon, operator error and/or a setup fault
Here I go again - attempt 8 tongiht at a alignment that is accurate enough to then get within even the 8 * 30 finderscope for Jupiter.
Any help or suggestions would be greatly appreciated guys. I had such high hopes and desires and now I am left feeling very flat. Simply follwoing all directions to the best of my ability is producing very mediocre results at best.
PS
Test 10 - some better luck, changed the location from Google Earths GPS coordinates of my backyard to just the manufacturer defined Sydney and suddenly GoTo is a whole lot better. This time Jupiter was in the wide angle scope about halfway in. Still though half my GoTos fail with one of the motors hitting some the other.
PPS
Can anyone else here who uses a CG5 mount validate or refute my worries?
Set up properly does it Goto things quite accurately?
Can it be commanded to GoTo and object along a route that won't involve it briusing itself most of the time?
I suspect the peg between the legs should mean fewer tripod collisions compared to the peg over a leg?
An American work colleague once came to one of our meets with a Celestron GoTo ‘scope and for the alignment, he had to point the OTA N (not S) and use Time Zone 14 in the Celestron Manual, although he had a Alt/Az Nexstar5 which may be a different hand controller/protocol than yours?
When he accidentally pointed the OTA S as the initial position, he got weird slews.
When he correctly pointed the OTA N but used the incorrect Time Zone he also got weird slews.
When he finally read the manual, pointed the OTA N and used Time Zone 14, everything appeared to work quite well.
No the peg position between the legs means the centre of weight is about 4- 6 inches further away from the tripods centre of suspension. This means to tip it over accidentally you have to bump the scope 4-6 inches less than is the centre of weight is closer to the point of balance.
Not sure which controller I have other than its the flash upgradeable one - with no documentation supplied on how to do this!
I just wished there was a diagnostic test documented to confirm it is working or not.
Still anyone else have data on this mount or know of a url where test matters are discussed?
Hi Matt,
Here a few links that you should look at which you can join and will help you immensely.
The CG5 mount is a very good “Go To” type mount and once you work it all out will give you many enjoyable viewing nights.
Your a God send with those views and links. Hugely appreciated, off to browse.
Matt
PS
I noticed on first alignment slew last night it was about 70 degrees off, pointing at horizon rather than high in the sky - shows some sort of offsite.
PPS
Annoyance - the Yahoo Celestron group takes a week to join before you can read it even, arggghhh!!!
Oh Matt! I hear ya mate! Major frustration! Let me just try to address each point in turn...
Quote:
Originally Posted by g__day
Well I'm up to day four with this my first GoTo mount. Accuracy is variable and lacking - at present its like daylight saving has confused things and its pointing an hour behind where everything currently is or something, plus more pointing errors.
I have found with mine (prior to fitting the GPS module) that despite setting the time accurately (as wellas location, etc) the drive was always behind in RA. The amount it was "behind" varied, and since fitting the GPS module, this error has gone, sine the drive is always up to date (time?) from the GPS signal. I suspect the drive does not start the clock when you enter the time, but after you have completed your alignment. Other than that, my drive is reasonably accurate... provided you put accurat info into it. Its the old GIGO problem (garbage in, garbage out).
Quote:
Originally Posted by g__day
Just some initial observations about the mount and manual.
1. The mount arrives with the Alignment peg placed between two legs rather than over one, against Celestron's advice - increasing its turning moment and chance of making a nasty whoopsie all the more likely.
Hmmm. I have my alignment peg between the legs, as delivered. I have not had a problem with this. Given the location of the counterweight and scope this should be the most stable position. I could see that with some OTAs it might be necessary to move the peg to the other side to avoid a crash between the OTA and the tripod leg, but otherwise I would be concerned about it.
Quote:
Originally Posted by g__day
2. The manual probably should suggest the following:
Understand where 20 or so most prominent alignment guidestars are, else if the set up GoTo is wrong you will not have the knowledge to align the scope to the correct stars
realise the design we choose means the dec motor can often knock into the RA motor housing - possibly stuffing up alignment? whenever you get to close to Alpha Centuari.
in fact about a third to half my GoTo attempts failed outright to complete due to the motors colliding, is this a dud design like a car that can go forwards or back, right in either direction but left only in reverse? I'm wondering if this lack of clearance is simply a fatal design flaw doomed to kill half the GoTos you could issue.
the scope doesn't understand this last point, and if there are two options to get to a new Goto point - bet your bottom dollar that it chooses the one that causes Dec motor housing to have a clunk and stop rather than take the obstruction free route
This is a worry... If the housings are clashing I suggest either the drive is faulty, or the alignment marks are not properly aligned during the start up alignment procedure, or the RA and Azimuth limits in the drive are not set. They should be set from the factory but can be changed.
Quote:
Originally Posted by g__day
same with the the 90 degree prisms hitting the tripod leg on some viewing angles cause of the travel route it favours
Are you talking about your star diagonal? What OTA are you using? I can't imagine this with my C8.
Quote:
Originally Posted by g__day
3. If you point to an incorrect wrong star as one of your three alignment stars you can't really undo, you have to re-boot and start from scratch again.
Actually it lets you correct 2 out of 3... but I share your frustration with this one!
Quote:
Originally Posted by g__day
4. About 50% of the time on goto first alignment star it points below the horizon which is just plain wierd!
Way below? A reasonable amount of time the drive will try to find a star that theoretically visible but it might be below your local horizon. If it's pointing below horizontal, though, something is wrong. Either the alignment marks not aligned during the start up alignment procedure, the database filter is disabled, etc.
Quote:
Originally Posted by g__day
5. Accuracy - well its about three finger knuckles behind where it should be on Spica and Jupiter.
Yup! This, I believe is a timing issue which the GPS module fixes.
Quote:
Originally Posted by g__day
6. Quick align on Jupiter then move teh scope and search for Jupiter again fails. With a small move doesn't the mount is unable to find Jupiter - the one alignment star that you choose 30 seconds earlier.
In a Quick align, the sky is just modelled from the time and location data you enter. It doesn't take any notice of where the scope is pointing... so it still goes to where it thinks Jupiter is.
Quote:
Originally Posted by g__day
7. The manual has no trouble shooting section
8. The manual has no first use diagnostic to give feedback on how to check your scope is functioning correctly (no benchmark diagnostic tests)
So right now I don't know if its a lemon, operator error and/or a setup fault
Here I go again - attempt 8 tongiht at a alignment that is accurate enough to then get within even the 8 * 30 finderscope for Jupiter.
Any help or suggestions would be greatly appreciated guys. I had such high hopes and desires and now I am left feeling very flat. Simply follwoing all directions to the best of my ability is producing very mediocre results at best.
PS
Test 10 - some better luck, changed the location from Google Earths GPS coordinates of my backyard to just the manufacturer defined Sydney and suddenly GoTo is a whole lot better.
What was the difference? The difference in position should be small, but obviously something about the way you've entered the data must be different???
Quote:
Originally Posted by g__day
This time Jupiter was in the wide angle scope about halfway in. Still though half my GoTos fail with one of the motors hitting some the other.
PPS
Can anyone else here who uses a CG5 mount validate or refute my worries? Set up properly does it Goto things quite accurately?
Definitely more accurately than you are describing!
The accuracy is only as good as the alignment and data entered. If your initial alignment is out by a couple of degrees (you won't neccessarily do any better by compass) then everything is out by a couple of degrees until you drift align.
The biggest inherent accuracy issue I have found with my CG-5 is the timing issue, which the GPS module fixes. Prior to the GPS I would set the time accurately, but I suspect the clock in the drive didn't start running till after the alignment procedure was finished. So if it took 20 minutes to muck about with the alignment (and maybe a collimation as well) then the scope is out 5 degrees in RA.
Since I have installed the GPS, the goto is reasonably accurate. The night before last for instance, I did a rough align only (compass alignment of tripod followed by 3 star auto align) and it slewed to about a dozen different DSO's and everytime the DSO was well within the FOV of a 30mm EP in the scope. I changed to a 13mm Nagler and some were inside the FOV and some were just outside. If I had bothered to drift align, I would expect all objects to be inside the FOV of the 13mm Nagler.[/quote]
Quote:
Originally Posted by g__day
Cn it be commanded so the GoTo without briusing its self most of the time?
I dunno what's happening here. Only once I've had this issue, and I didn't get to the bottom of it. I switched it off before it did any damage, so then I couldn't see what data it had wrong in it to make it do what it did. In my experience this just isn't an issue in normal operation. You could muck about with the RA and Dec limits in the drive, but I think you'll find that too limiting. I suspect something is not right to be causing the crashes. Have you sought advice from the dealer you bought the scope from?
First off, I must admit that I don't know anything about a CG Mount so this might be wrong.
Is your date and time inputted in the correct format? especially date, is it required to be entered in the American format ie mm/dd/yy? is time required in UT format?
I only ask this as the Gemini is required in this format, maybe that is what is wrong !!!!!!!!!!!! only a guess. It is rather strange behaviour.
Cheers
I am not sure whether is will be any help now after all the other comments , but may be useful. Sheeny comment about setting the time is an interesting conundrum indeed.
Welcome to the world of Synta (the real manufacturer of this mount) Skywatcher/Celestron CG5
First of some basic question.
Is the tripod level prior to placing the EQ Head on top?
Is the polar axis pointing due south (counter weight on the southern side of the mount) and set to the correct elevation?
Does the mount have a polar alignment scope and if so can this be used to accuracy align it with the constellation of Octans which is located near the SCP and if the scope did not come with one ask the supplier why?
Is the mount/scope balanced properly?
If you’re southern view is obstructed by housing use a compass to find magnetic south and then adjust for magnetic variation to find true south. Mark it on the ground so that you can use it for later reference.
What I have done is gone through some of the basic set for an EQ mount.
Time to set up the GO-TO, I would recommend that you do a factory reset and set your location for Sydney. We will worry about enter your location data later, mainly because the software is written for the northern hemisphere e.g. the good old USA.
Now for the alignment process, ensure that the index marked in both R.A. and Dec are aligned. This is very important as the mount need to know were it is starting from. Go to the Two Star Alignment Menu, now you are going to choice two alignment stars it the Eastern part of the sky. There is an obvious reason for this and that is Meridian Flip. We are keeping things simple.
Choice two stars that lie about 45 to 90 degrees apart. Choose the first alignment star and allow the mount to slew to it. Align on the first star press enter to accept the alignment select the second alignment star and allow the mount to slew to it. Align on the second star; press enter to accept the alignment. Job done, the scope should point accurately enough to find most object in the eastern part of the sky (most objects will end up in the FOV of a standard 26mm Plossl EP). When you flip over to the western part of the sky you should be able to locate a know object and from the software menu you may have some this like “Align on Object or Sync” this should sync the scope for operation in the western part of the sky.
Finally go back to the manual and have another read. Remember it is written for the northern hemisphere.
P.S. I will get back to you about setting your location data later.
Yeah, I agree John. Something simple like that would seem the simplest explanation for the behaviour.
Alignment marks?
Date wrong format?
Wrong Time zone?
Wrong time (am/pm)?
Matt, I assume your electronic compass works by detecting magnetic field. Are there any magnetic anomalies around you that could affect your compass? EG concrete building(reo), power lines, etc. That could have a big effect on your alignment (but not big enough to have it looking for stars underground!)
Also are you still using you PC to drive it or have you gone back to the hand controller? I suggest going back to the hand controller until you get it sorted, just so any complications from the PC system are not introduced.
Hang in there mate! It would be nice to put two drives side by side to see the differences!
I ponder the internal clock issue because on a reset the last time it knows about is the clock when alignment started, not the time when it was powered down - which implies the clock wasn't running, which would definetely contribute to the problems I encountered - and as my first alignment took 20 - 45 minutes would say why my GoTo errors were so large. By the end of the night alignment took < 20 minutes - so pointing accuracy on Jupiter was far better.
Alignment marks checked on both axis on each power down reset. Also checked vs the handcontrollers query - and the DEC alignment marks are spot on, but the RA is about 3 degrees out - the RA alignment marks should be a bit to the left of the marked position to get a 0 00' 00" reading so I countered for this later in the night.
Date wrong - well its MM/DD/YY so it wont accept 17 as a valid month, so I set 06/17/06 yesterday, only had a date error on my very first set-up.
Time zone is 10 for Sydney (and I pretty sure it was +10) checked this twice.
Time was entered both as pm but normally using 24 hour miltary time. I've been round the world 15 times now and can kinda do it in my head.
I used two compasses, both gave readings for 170 (I treat Celestial South in Sydney as 11 degrees East of magnetic South). I also roughly checked where the crux and two points intersect as a rough double check, and did a 20 mintue drift track on Jupiter and adjusted to improve. It wasn't perfect but it should be within 5 degrees.
Backyard has no concrete buildings or powerlines within 50 yards.
I thought modelling 3 points give you a complete sky picture - PLUS compensation for the drives not being properly polar aligned. I assumed the software was specifically looking to estimate and conteract this.
Mount stability - rock solid and not bumped all night.
Tripod base level - yes according to both my spirit levels and the internal bubble on the mount.
Scope as perfectly balanced as I could get it.
I have gone back to the Hand controller to drive it while its in the back patio.
No Polar alignment scope - probably the next thing I buy.
GPS - YES I think its my next major buy, from Andrews again if I can - that way its one supplier fixing all the issues and no finger pointing to somebody elses problem, and if doesn't work in the end its a warranty call.
Factory reset - very temped too.
* * *
Questions on the GPS option. I presume it plugs into the hand controller, and is only present at the start-up time (otherwise you couldn't computer control the mount, unless the PC plug goes into the GPS? Or is it GPS or PC but not both in one viewing session?
* * *
On the drive housings bumping. They are not round with a clear gap in all positions / rotations, they are horseshoe shaped and if you are looking close to SCP there are many positions which they will hit each other.
Similarily both the guidescope and the 90 degree diagonal can hit the tripod in the wrong positions looking near the SCP.
This is simply because the drives are too close to each other and the mount is not tall enough to rotate fully and not position the scope to collide with the mount or tripod.
* * *
Well rather than viewing again tonight I'll likely just spend teh night websurfing trying to find a diagnostic or a fix.
Keep the advice comming guys - especially if you know of a suorce that has experienced and solved this problem.
Hang in there mate! I know its frustrating, I've been there myself (just not as deep I think! )
The GPS option, FYI, includes the GPS receiver and an accessory module. A cable joins the GPS module to the accessory module and another one joins the accessory module to the hand controller port on the RA housing. There are two other ports on the accessory module - one will take your hand controller, and the other is for your PC connection. So it's all hooked up and available 100% of the time if you want it! The GPS runs continuously so the time in the scope is accurate... always!
It would be nice if the GPS option was cheaper (of course!) but I am SOOOO glad I got it!
That's very pleasing to hear! How is the GPS powered? What voltage / ampage does it need?
Where did you get it and how much? I've asked Lee of Andrews to price one for me, they are trying to help me but its a new issue to them and they are in the process of refering me to a collegue with greater specific mount knowledge.
* * *
I finally got into the yahoo CG5 forum and the faq states something interesting
For alignment to work, the GoTo Electronics require that you use two stars to the West of the Meridian and one star to the East of the Meridian.
Well with my limited knowledge of stars I simply chose alignment stars in the alignment catalogue whose names I knew - no idea what side of the Meridan they were on, nor if that is a Northern Hemisphere restriction only!
I got my GPS module from AstronomyOnline for $680 I think (from memory!). It draws it's power from the scope drive, no separate power supply required.
The standard auto align procedure is fine. Stick with that to start with. In the southern hemisphere (i.e. for us!) it will pick two stars in the eastern hemisphere and one in the west, than calculate cone angle errors etc.
If it picks a star that you can't see, just press the Undo button, and it'll go to the next one, etc until it gets the stars it needs. If it picks a star that you aren't sure about, you can "undo" that as well if you like. Once you get into it, it's pretty straight forward, it will lead you through.
I used two compasses, both gave readings for 170 (I treat Celestial South in Sydney as 11 degrees East of magnetic South). I also roughly checked where the crux and two points intersect as a rough double check, and did a 20 mintue drift track on Jupiter and adjusted to improve. It wasn't perfect but it should be within 5 degrees.
Hi
The wording is correct it is my very rusty navagation skills. So you are correct by saying True South is 11 Degrees east of magnetic south.
Your understnading is correct about finding true south.
The magnetic delination or magnetic north in Sydney is moving in an easterly direction. Currently magnetic north is about 13 Degrees East of True North, therefore True north is 13 degrees west of Magnetic North. True south will be 13 degrees East of magnetic south. See diagram. If I am wrong "OOOOp's" which I was before correcting the postso sorry for the confusion .
Using Crux and the Two Pointers to find due south is a very good way to get rough polar alignment. Using drift is also a good idea as well.
Last edited by anthony2302749; 20-06-2006 at 12:32 PM.
Lee from Andrews has now got Steve Boyle (the Celestron guru in Oz) in the link trying to sort this with Celestron in the USA, so my peace of mind has risen substantially!
I now know the names and locations of about 10 alignment stars so set up is alot quicker now! And yes I know all about the UnDo buton and select alignment stars which you know!
Anthony,
Was that a major oops on my part? BinTel told me 11 degrees East of Magnetic South for Sydney, but if its 13 degrees West well that's a major stuff up! Anyone point us to the definite correct answer? What is the compass heading for the SCP, is it 169, 167, 191 or 193 degrees?
Location Lat. Long. Declination Incorrect Error
(degrees) Declination (degrees)
(angle between (degrees)
where a compass (angle between
needle points north magnetic
and true north dip pole and
pole) true north pole)
My apologies, Myastroshop is correct with his compass direction. It's me, generally my navigation skill were spot on, obviously I am getting to old. Go with the second one, 13 degrees west of magnetic north. So on your compass true south should be 167 degrees from magnetic north.
Last edited by anthony2302749; 20-06-2006 at 12:39 PM.
Reason: Correcting Error in the Post
Although I don't do this any longer, (as I have three fixed registration marks in the back garden), I used to align the polar axis with the green line in the attached image. This would place the four stars of Octans, one of which is Sigma Octans, in the FOV of my Polar Alignment Scope where I would then align more accurately by adjusting the Alt Az knobs of the GPDX mount.
Edit:
I have just added a scan of a Brisbane map, (coincidentally showing Cambroon, Ron's location) which graphically shows the relationship between Grid North (GN), True North (TN) and Magnetic North (MN).
This appears to indicate that when the compass needle is pointing N on the previous photo of the compass, (=0 deg), then we need to subtract 11 deg, which gives 349 degrees.
We then set this 349 deg at the “READ BEARING HERE” mark and let the compass point to N as shown by the rotating pointer at the “N” mark in the white outer bezel. Then, the True North line will be along the green line.
At least I think that is correct? Corrections welcome and gladly accepted!
Cheers
Dennis
Last edited by Dennis; 19-06-2006 at 05:51 PM.
Reason: Added scan of map showing Grid/True North and Magnetic North
Hi
Magnetic declination varies by 1 to 4 degrees between places only tens kilometres apart. For my place 33 45 S and 150 28 E it is12.27 degrees east.. You subtract East declination from your magnetic bearing. In other words your compass is pointing 12 27 degrees East from true North. If you don’t believe me, take your compass and point it on constellation of Octans.. You will read around 170 degrees.
Very good Web site to find Declination is http://www.ngdc.noaa.gov/seg/geomag/jsp/Declination.jsp
Karl
Found the problem and a simple correction to the set-up fixed all the problems, the motors knocking and the pointing being simply crappy. Its was so easy when I figured it out. The thing that twigged me to it was I tried doing a 3 star align using Antares, Acturus and Spica - in under 5 minutes as the cloud cover started to roll in. Well Antares was star numer one and the scope pointed below the horizon. Then for star 2 I stopped it just before the motors went to hit. Spica was totally wrong. So got these entered in under 10 minutes and searched for Jupiter - again the motors went to collide and nothing I could do manual slewing to any position and then executing Goto when close to Jupiter could stop a motor collision. At this point I was think what a piece of total **** this mount was... I tried a factory reset and no joy there either.
Then it hit me. I re-powered and set the scope to its initial trangles pointing to each other on each axis position and stopped the set-up and checked the axes positions. Bingo - 0 00 00 and 90 00 00 - DEC was ninety degrees out as it had arrived from the factory. So I simply manually slewed back to a point where the mount axes said 0 00 00 and 0 00 00, then released the clutches and moved the DEC axis back to its alignment mount. I re-powered and what a difference! Initial set-up and slewing to the first 3 alignment stars was good. And the motor drives never clunked. I executed a few gotos - Antares, Spica, Jupiter, Alpha Centura and M4 - beautiful, absolutely beautiful. Close to centred even on my rough set-up and the motors moved very cleverly around each other and never touched once!
...but I'm intrigued now... what was wrong from the factory? Is it:
the position of the alignment markers on the body of the dec axis housing?
the initial position in the software of the scope once the initial alignment was done?
the scope's home position?
I'm not sure if the home position affects the alignment - I assume not, but I've never played with it. You can change it if you want to.
You can check No 1 visually when it's set up. With the mount setup and aligned to the SCP the motor bulge in the dec housing points to the west when the alignment marks are lined up. Do yours?
I guess if it's neither of those things i has to be No 2. Which I would think is weird!
Other than that, my drive is reasonably accurate... provided you put accurat info into it. Its the old GIGO 
, but may be useful. Sheeny comment about setting the time is an interesting conundrum indeed.
so sorry for the confusion 
.
