CG5 GoTo Blues...

[anthony2302749]

Hi

Glad to see that you have got it worked out and the fix turned out to be a simple. I can also see why your pointing accuracy is way off. In the manual it describes following;

Before any of the described alignments are performed, the telescope mount needs to be positioned so that the index marks are aligned on both the right ascension and declination axes (see Fig 2-8).
Once the index position has been set, the hand control will display the last entered date and time information stored in the hand control. Once the telescope is powered on:

What Celestron should say is “Before powering up the hand controller, the mount needs to be positioned so that the index marks are aligned on both the right ascension and declination axes”. If the hand controller is power up before the index marks are aligned the hand controller will accept that as the home position.

So just looking a one axis, the declination, if the index marks are not aligned, say by about 10 to 15 degrees, and the hand controller is powered up there will be an error of 10 to 15 degrees in declination. Moving the mount to the index marks after powering will not correct for this error. The same will occur in RA if the index marks are not aligned before powering up.

Putting in simply, the index marks must be aligned before the hand controller is powered up. The hand controller need to know the home position e.g. index marks, so that it can calculate were the first alignment star is and so on. If the mount is powered up before the index marks are aligned there will always be an error in pointing.

[g__day (Matthew)]

The position of the alignment marks were fine, as is the software, but the data wasn't. The encoders weren't storing a correct set up value on both axes for the alignment position - meaning:

1) On alignment each star looked like it was 90 degrees out of position and
2) Each motor was almost guarannteed to knock into each other on half of all gotos

So in alignment position I assummed each axis should read 0 00 00 or 90 00 00, but one on 90 and one on zero seemed confused.

What did surprise me last night when I finished up and went into hibernation I read the axes and they said 90 and 90, even though I'd adjusted them to be 0 and 0 on set-up.

So once the weather clears I will try them again.

Oh and I fixed up a really annoying DEC backlash - somehow the settings had moved from 0 to 18, setting it back to 0 fixed everything.

[anthony2302749]

Originally Posted by g__day

So in alignment position I assummed each axis should read 0 00 00 or 90 00 00, but one on 90 and one on zero seemed confused.

The first set of digits represents Right Ascension (HH:MM:SS), the second set of digits represent Declination (Degrees:Minutes:Seconds).

I suppose when you first power up the hand controller after aligning the index markers you may get a reading of 00:00:00 for RA and 90:00:00 for Dec. Remembering when using celestial coordinate’s declination is measured in degrees north and south of the celestial equator. The South Celestial Pole is at 90 Degree Declination and would be written as -90 degrees, the minus denotes south of the celestial equator (0 Degrees).

Now remember at power up, the telescope does not know were it is and may give a reading of 00:00:00 for RA and 90:00:00 for Dec (This is the home position). The things in need to know is its location, date, time and the location of one, two or three star. Once it has all this information it can then compute the location of any object with in the data base of the handset and find them. The hand controller will give you the correct coordinates for any given object as well.


Still work on the other problems you are currently experiencing.

Just been reading the manual, very confusing chinglish, it should be re-written so that it will make sence.

[sheeny (Al)]

Originally Posted by anthony2302749

In the manual it describes following;

Before any of the described alignments are performed, the telescope mount needs to be positioned so that the index marks are aligned on both the right ascension and declination axes (see Fig 2-8).
Once the index position has been set, the hand control will display the last entered date and time information stored in the hand control. Once the telescope is powered on:

What Celestron should say is “Before powering up the hand controller, the mount needs to be positioned so that the index marks are aligned on both the right ascension and declination axes”. If the hand controller is power up before the index marks are aligned the hand controller will accept that as the home position.

Hmmm. Interesting Anthony! Generally I align the marks prior to powering up as you suggest, even though the program prompts suggest you can align the marks after powering up... if you are right you might have shed some light on the one or two times my drive has done some screwy things!

Thanks,

Al.

[g__day (Matthew)]

Hmmm,

My process was

1) Put axes markers in start position
2) Power on
3) Abort alignment by pressing menu
4) Read axis position in Utilities menu
5) Adjust scope using RA and DEC until ALt and AZ both read 0 00 00
6) Unlock clutch and manually move scope back on alignment marks

7) Not sure if I powered down or not

8) Start alignment - setting time and date

Three stars latter all is well and no motor housing clunks whilst operating

9) Slew back to alignment marks at end of night
10) Read Alt and AZ - now 90 00 00 and 90 00 00 (I expected 0 and 0)
11) Hibernate and power down.

Perhaps the Dec should be 90 at start up but the alignment marks should be 90 degrees further around?

[anthony2302749]

Hi Al

I have been reading the manual to nut this problem out and find It is a bit screwy in places.

1. Before starting the alignment procedure the manual ask you to aligned the index marks on both the right ascension and declination axes. I would assume this is done before powering up the mount.
2. The manual then repeats the same set of instruction in Step 2 on page 19. If it was done as per paragraph one, page 19 why repeat the instructions. Step 2 to should real say "If you have not aligned the index marks on the mount the hand controller will prompted you to do so, and then suggest ways to correct the problem.

My suggest would be to align the index marks manually prior to powering up the mount.

3. Entering the time and date is not a problem, but location is, the manual is obviously written for the northern hemisphere in mind and gives no explanation of how to set the coordinates for locations in the southern hemisphere other then go look up appendix list.

4. The other thing I find strange is the alignment procedure. Reading "Auto Align" it states the following:

Once the telescope is finished slewing to your first alignment star, the display will ask you to use the arrow buttons to align the selected star with the crosshairs in the center of the finderscope. Once centered in the finder, press ENTER.

The display will then instruct you to center the star in the field of view of the eyepiece. When the star is centered, press ALIGN to accept this star as your first alignment star.

Why two key strokes, one would be enough no wonder it takes so long to complete a alignment proccess. The commonsence way of doing it would be to instruct the use to sight the alignment star with the finderscope first then center the star in the EP and then press ENTER. This is how you do it with the LXD75 mounts.

Anyway what I am trying to do is re-write the manual in regards to Alignment process so that it makes sense. Give me a couple of days.

[anthony2302749]

Follow these instructions

• Align the index marks on the DEC and R.A.
• Power up the mount
• Select Auto Align
• Follow the instructions as outline in the manual, I think page 20.
• If you have follow the instruction carefully you will have a Successful Alignment, and you are now ready to find your first object.

Please do not take it the wrong way but your procedure is flawed. There is no requirement for the user to adjust the scope so that the RA and DEC read 00:00:00. after power up. See manual

The start postion for the telescope is the index marks. As I pointed out early the hand controller dose not know were it is until the time,date,location and 3 star alignment is complete. By moving the mount to RA 00:00:00 and DEC 00:00:00 will cause a lot of trouble as you have found out. Example if the Index Marks are line up correctly on the DEC (e.g. the front of the telescope is pointing south) and then you rotate the DEC in an Easterly direction so that the DEC reading on the hand controller reads 00:00:00 and then do a alignement you will more then likely be 90degress of your first alignement star. I think you have experienced the problem already.

So have a go at my procedure and follow the instruction in the manual and you will have success.

Originally Posted by g__day

1) Put axes markers in start position
2) Power on
3) Abort alignment by pressing menu
4) Read axis position in Utilities menu
5) Adjust scope using RA and DEC until ALt and AZ both read 0 00 00
6) Unlock clutch and manually move scope back on alignment marks
7) Not sure if I powered down or not
8) Start alignment - setting time and date

Three stars latter all is well and no motor housing clunks whilst operating

9) Slew back to alignment marks at end of night
10) Read Alt and AZ - now 90 00 00 and 90 00 00 (I expected 0 and 0)
11) Hibernate and power down.

Perhaps the Dec should be 90 at start up but the alignment marks should be 90 degrees further around?

[sheeny (Al)]

Originally Posted by anthony2302749

Hi Al

I have been reading the manual to nut this problem out and find It is a bit screwy in places.

Yes.

Originally Posted by anthony2302749

1. Before starting the alignment procedure the manual ask you to aligned the index marks on both the right ascension and declination axes. I would assume this is done before powering up the mount.
2. The manual then repeats the same set of instruction in Step 2 on page 19. If it was done as per paragraph one, page 19 why repeat the instructions. Step 2 to should real say "If you have not aligned the index marks on the mount the hand controller will prompted you to do so, and then suggest ways to correct the problem.

My suggest would be to align the index marks manually prior to powering up the mount.

3. Entering the time and date is not a problem, but location is, the manual is obviously written for the northern hemisphere in mind and gives no explanation of how to set the coordinates for locations in the southern hemisphere other then go look up appendix list.

Now that you mention it there was some doubt when I first fired up the mount... but I'm used to it now... well I should say I was... I don't have to do that anymore now that I have the GPS!

Originally Posted by anthony2302749

4. The other thing I find strange is the alignment procedure. Reading "Auto Align" it states the following:

Once the telescope is finished slewing to your first alignment star, the display will ask you to use the arrow buttons to align the selected star with the crosshairs in the center of the finderscope. Once centered in the finder, press ENTER.

The display will then instruct you to center the star in the field of view of the eyepiece. When the star is centered, press ALIGN to accept this star as your first alignment star.

Why two key strokes, one would be enough no wonder it takes so long to complete a alignment proccess. The commonsence way of doing it would be to instruct the use to sight the alignment star with the finderscope first then center the star in the EP and then press ENTER. This is how you do it with the LXD75 mounts.

The CG-5 changes slew rate on the drive when you press the Enter key to make it easier to centre the star in the EP, that's all. Once you get the hang of changing slew rates on the hand controller, this wouldn't be an issue at all. When I was new to the drive I didn't mind it doing that... except when I hit the Align button accidentally instead of an arrow button and it aligned on nothing!

But you're right, the procedure is slow and could be simpler! I would really like to understand the maths the drive does... how much does initial misalignment affect the so called cone error that it calculates?

Originally Posted by anthony2302749

Anyway what I am trying to do is re-write the manual in regards to Alignment process so that it makes sense. Give me a couple of days.

I used to struggle through the auto align and then do a drift align... and it all becomes a bit tedious. These days, if I'm just doing some quick observing or some planetary imaging where some drift is not critical, I just do a compass alignment, then auto align. If I'm planning to some more accurate imaging and want to accurately drift align, I'll do the compass alignment, a quick align (the CG-5 just models the sky) then drift align. Then I'll power down and up again and do the auto align to calculate the cone error. Sounds messy doesn't it?

I have found that my dec alignment marks are about 1mm inaccurate (checked by looking through the eyepiece while rotating round the RA axis).

Al.

[anthony2302749]

Hi Al

Have you consider getting a polar alignment scope, it will give you a quick and easy method of polar alignment all the time with little of no error, I had one on my old EQ5 which worked very well. I would get accurate tracking up to 15min plus with minimal drift in DEC. The mount was only fitted with a simple dual axis drive. I would use the mount mainly for astrophotography and I got some very good results using film.

[g__day (Matthew)]

Anthony when you said ""The start postion for the telescope is the index marks. As I pointed out early the hand controller dose not know were it is until the time,date,location and 3 star alignment is complete. By moving the mount to RA 00:00:00 and DEC 00:00:00 will cause a lot of trouble as you have found out. Example if the Index Marks are line up correctly on the DEC (e.g. the front of the telescope is pointing south) and then you rotate the DEC in an Easterly direction so that the DEC reading on the hand controller reads 00:00:00 and then do a alignement you will more then likely be 90degress of your first alignement star. I think you have experienced the problem already."

Actually my procedure corrected this and for the first time things just worked. When this orocedure wasn't applied the motor housings would always knock and alignment was nigh on impossible to complete.

I didn't try and complicate things for fun or sheer bloody mindedness, I need it for survival and it subsequentially brought me joy. Following the manual on page 20 over my first 16 attempts simply failed until the correction I gave above. I am still awaiting Celestron's response beyond the rather helpful (I kid you not) "doesn't this guy know how to use a GE mount?"

I am still very puzzled why when I set it to 0 00 00 manually for the star alignment position, then ended the in the same position - why it now read 90 00 00 and 90 00 00.

Perhaps its a bug in my mount?

PS

I need to re-test to see what I changed. I believe it was the RA and DEC settings, but what if it was the ALT and AZ readouts? My unfamilarity with the handcontrollers menu may have lead me to confuse the two. On the next clear night I'll be more exacting as to what I do and how cleanly it fixes the problems.

PPS

I noticed comming out of hibernation the scopes RA drive movement was jerking back and forth slightly on start up. This occurred yesterday to and when I looked at the setings for +ve and -ve RA and DEC backlash all four were set to 18. I re-set these back to 0 and all jerkiness went away again.

Why is this happening now and why must I reset this on every start-up?

[sheeny (Al)]

The backlash settings in the drive are set to 18 from the factory. This probably correspnds to the average backlash they expect from the drive gears.

There is a procedure for adjusting the backlash. I don't have it with me to refer to at the moment. Unfortunately I suspect it is written in Chinglish as Anthony describes it, and it really takes some study to work out what you should be doing. I have worked through the procedure a couple of times (once with some success) but I note that do need to do it again since I have a significant jump in one change of direction.

There are two figures for each axis, one tells the drive how far to turn at high speed during a direction change to take up the slack in the drive gears... the other one I can't remember... It is in the manual. If you are thinking of doing any guided imaging work you'll need to sort this out.

Al.

[sheeny (Al)]

PS. It doesn't sound right that you have to reset the backlash settings everytime. It should remember them.

Al.

[g__day (Matthew)]

I concur! It wasn't doing this on the first 3 outings. Two days ago it was only DEC up that was jerky. This morning I powered on and both RA directions were jerky until I set backlash to zero. I wonder if there is an issue with problems caused when the motor housing were briefly clunking? Again setting backlash to zero fixes this, but I hear 18 is the factory default setting.

I hope this isn't a sign that they should be at 18, not zero, but some damage was done during motor housing clunks. I presumed real damage would be aborted as there must be a friction clutch which gives when the scope tries and impossible (blocked move).

Sigh, just one more thing to worry about.

Celestron say now they can't recreate the problem, have never heard of it, say the scope would be in a contorted position to view anything if it was used like this (fully agree there!) and don't know why it occurred and have asked for pictures. So I've sent them some and reminded them its the slew route, not the slew destination (well ultimately that too) that is trouble number 1. I will await their reply tomorrow.

Meanwhile I'm keen to get some clear viewing and try again to see exactly how my fix holds out for viewing experience five!

[anthony2302749]

Hi Al

Finally got around to re-writing the procedure for aligning the CG5. I hope it will clear up any confusion.

[g__day (Matthew)]

Must read that thanks!

Tonight did alot more testing. Strangely everything worked like a charm all night long with no hassles of the last few nights. My change seems to have worked and sticked.

I did a 2 star align + 4 calibration stars and everything was great. All 6 stars were within the finderscope each time!

So I am happy but puzzled what caused problem and how it just went away...

[sheeny (Al)]

G'Day Anthony,

Your re-write is certainly clearer than the manual!

Al.

[sheeny (Al)]

Originally Posted by g__day

Must read that thanks!

Tonight did alot more testing. Strangely everything worked like a charm all night long with no hassles of the last few nights. My change seems to have worked and sticked.

I did a 2 star align + 4 calibration stars and everything was great. All 6 stars were within the finderscope each time!

So I am happy but puzzled what caused problem and how it just went away...

I'm glad it's settled down and you can make some progress... but it's a pain when things seem to just "go away" without working out what solved it!

Enjoy it while you can!

Al.

[siriuslyfuzzy (Mick)]

date format is American style .....month day year...?

[AstralTraveller (David)]

Originally Posted by siriuslyfuzzy

date format is American style .....month day year...?

Yes, it's a trick for young players from sensible countries. IMHO all dates should be YYYYMMDD though DDMMYYYY is acceptable. MMDDYYYY is madness.

[siriuslyfuzzy (Mick)]

Originally Posted by AstralTraveller

Yes, it's a trick for young players from sensible countries. IMHO all dates should be YYYYMMDD though DDMMYYYY is acceptable. MMDDYYYY is madness.

.............

yes you woudnt realise till you got to the 13th day of the month ...even then you most likely would just put the American format in with out realising you had fixed it?