CG-5 mount alignment issues

Louwai (Bryan) · #1 06-09-2007, 08:35 PM

Hi all,
Have tonight set up & have done the 3-star alignment.
After pointing at a couple of things I find that the alignment is out so I realign.
Go-To Jupiter & the planet doesn't even appear in the FOV.

Totally shut down, align from scratch.
Same problem.
For some reason I just can't get it right.

I was set up in the same position last night using the same method & it put the target in the center of the FOV every time.

Does anyone have any suggestions as to what may be causing this????

Cheers, Bryan

Dennis · #2 06-09-2007, 09:22 PM

The first thing I would check is the mechanical train of gears. If the gears are locked on their shafts (that connect to the worm) using small grub screws, just make sure that one or both of them haven't worked loose.

If they have, the gear will slip on the shaft and GoTo's will not be accurate.

Next, I would check the software settings such as your Latitude, Longitude and Date/Time.

Cheers

Dennis

Louwai (Bryan) · #3 06-09-2007, 09:32 PM

Thanks Dennis,
Have checked all you note below other than the screws.
The manual lock levers are tight.

Since the last post I have been checking.
It's as if the alignment was say 15deg out.
Looking through the finder, the target seems the be a similar distance away from the cross hairs each time.
Just outside the FOV.

I just don't understand.
Just now I moved to Vega which was 1 of my alignment stars & it sat right in the middle of the FOV. Straight away went to Jupiter & the scope stopped about the same distance away as it was before going to Vega.

Dennis · #4 06-09-2007, 09:51 PM

Hmm, 15 deg = 1 hour. Have you accidentally set daylight saving time?

Cheers

Dennis

Dennis · #5 06-09-2007, 09:56 PM

As I’m not familiar with the mount and controller, I can’t offer any specific advice. If there is a set up menu, I would scroll through it to make sure that all the settings, values, signs (+ -), N/S hemisphere operation, timezone, etc make sense.

Cheers

Dennis

Louwai (Bryan) · #6 06-09-2007, 10:12 PM

Quote:

Originally Posted by Dennis

Hmm, 15 deg = 1 hour. Have you accidentally set daylight saving time?
Cheers
Dennis

Sorry Dennis, Not exactly 15deg. That was just a guess. To be truthful it's probably more like 8 to 10deg.
Haven't been through the setup, mainly because nothing has changed from last night. It's sitting in the exact same spot, with all parameters the same as last night.
I've just been out playing with it some more. Finally gave up & packed it all away.

I hope it fixes itself by tomorrow night for the public meeting at MPAS.

Dennis · #7 07-09-2007, 07:07 AM

The only other thing that I can think of is to check your polar alignment as IIRC, my altitude clutch slipped once on my German Equatorial Mount and my GoTo’s were consistently off by the same amount.

Some mounts require precise Polar Alignment for accurate GoTo operations, whereas I think my Vixen GPDX could model the errors the more alignment stars I choose and sync’d on. Good luck!

Cheers

Dennis

sheeny (Al) · #8 07-09-2007, 07:33 AM

Louwai,

I have a CG-5 and I think I've been there and done that. MY guess is that your alignment is out in RA. Am I correct?

If so, what I think is happening is that you set the time at the start of the alignment process, then do a three star align. The mount doesn;t seem to advance the time while you are doing the alignment

, so your alignmnet always ends up lagging behind in RA.

I solved the issue with my mount by installing the GPS option. Best thing I ever did, but an expensive solution. You would think there would be a better workaround!

Al.

OneOfOne (Trevor) · #9 07-09-2007, 07:49 AM

My CG5 (now sold) generally performed quite well and would usually get the target into view each time...for several hours. When you are selecting the time on the keypad it has a Daylight savings option so you just enter the current local time and tell it if it is daylight savings or not.

I seem to recall a couple of times having the goto out quite a bit because I couldn't recognise 2 stars in the east (it needs 2 in the east and one west). I had to go inside and get the planisphere and bino's and try to find another star. It seemed the goto was not so great, so I was suspicious that while aligning the clock is "stopped" so you could be out. I since found out that selecting the same star in the east twice works if you are desperate.

I would suspect something slipping?

rumples riot · #10 07-09-2007, 09:32 AM

Its time related I think. My CGE is the same and I am going to get a GPS unit to solve the problem. That way it always gets it right from the start.

Dennis · #11 07-09-2007, 10:12 AM

Hmm that sounds weird? If we work on objects rising over the E horizon by 1 degree every 4 mins, then even if you take 10 to 12 minutes to perform an alignment, the GoTo pointing error should only be around 2 to 3 degrees?

Cheers

Dennis

g__day (Matthew) · #12 07-09-2007, 11:07 AM

I've had the same thing in the past too, and the 15 degrees = 1 hour always make me check time and daylight savings switch - that caught me at least 3 times.

Also I time starts from the moment you start the alignment process - so it you started set-up - entered date but waited 30 minutes before you entered time all your alignments would be screwy.

Also I always try to do my 3 star align as fast as I can - well under 10 minutes if I can. I once completed a 3 star align over a 4 hour period - gotos where completely off. This was just to prove to me the clock doesn't completely adjust / update correctly between choosing stars.

On a pier once polar aligned what I ended up doing was a 1 star align to avoid time drag issues in the alignment. Then all I did was add stars at my leisure. Go to some star - then press align - replace alignment or calibration stars, centre it and lock it in.

This way always worked best. Then I'd finish my observing with a park at a home position and use hibernate. All I'd have to do from wake-up routine was select change on power-up and re-set time and date as accurately (and quickly < 20 secs) as I could then press enter.

This consistently produced great goto results for me.

dugnsuz (Doug) · #13 07-09-2007, 12:18 PM

Hi,
Maybe some tips/answers in my recent thread?
All the best - Doug

http://www.iceinspace.com.au/forum/s...ad.php?t=23582

Dennis · #14 07-09-2007, 02:46 PM

Just for a comparison, I believe that my Vixen Skysensor 2000 keeps track of the time, so you can align at your own pace, and keep re-aligning and re-syncing all night long. This is useful when doing a long slew that crosses the Meridian – touching up the alignment at the end of the slew makes for more accurate GoTo’s.

This may be one of the more “hidden” value-add capabilities of Vixen Japanese products versus Chinese Clones, that contributes to the price difference.

Cheers

Dennis