Celestron CG-5 GOTO Mount Problems

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RE: Celestron CG-5 GOTO Mount Problems

Postby dellboy » Sun Oct 26, 2008 6:23 pm

Adam
i have the manual cg-5 mount to which i have added a retro-fit goto system.
I have recently stripped the mount using astroboy's instructions as i had always had excessive play in the mount.
It is now much better, how ever i nearly always loose some begining shots, even when using PEC ,mirror lockup and remote shutter release due to trails.
Derek
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RE: Celestron CG-5 GOTO Mount Problems

Postby gord » Fri Dec 19, 2008 4:50 pm

I find my CG-5 a pain too (well I am new to this type) and am looking to upgrade to GoTo. Just try! If anyone can get me a price on the parts I NEED without another tripod, weights and bar point them at me please. Thanks, Chris [email=ancaster@ntlworld.com]ancaster@ntlworld.com[/email]
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RE: Celestron CG-5 GOTO Mount Problems

Postby 1981astro » Thu Dec 25, 2008 8:36 pm

Without sounding detrimental to you, make sure you have done the following properly.
From what you have provided, I am making an [b]assumption[/b] you only do a polar align and not a 3 star auto alignment, which is how your mount learns over time and it'll start doing the alignments more accurately. This could explain why you are slewing in the general direction but not getting there dead on if you have never done this procedure; after a few nights of aligning this way, you'll find that the alignments get closer to the star it choses, without the need to slew the scope to much to set it up.

(a) Stand your tripod where you want to do your viewing session.
(b) Adjust your tripod so that the mount faces perfect North
(c) Remove the RA cover and look through. You should hopefully see Polaris in there somewhere.
- the aim here is to get Polaris dead centre. You can use a polar finder scope in the slot, or do a rough estimate (I do the latter). Move the tripod gently if you need to move Polaris left or right. Adjust the latitude screw if you need to move it up or down.
(d) Once you are happy with this, put up the OTA onto the mount and do your usual balancing for RA and DEC.
(e) The following is best with a illuminated EP - I have a 12mm one that is perfect for this job.
- Power the mount and start the 3 star auto alignment. Enter the relevant information (remember it's american'ised, so date actually is MM/DD/YYYY not DD/MM/YYYY)
- The mount will use the provided information to find 3 stars in the sky. It will automatically choose these, and on the controller will display the name of the star it is slewing to. This is what it learns. The first time this will not be accurate. Use a sky chart, or software on a laptop close to the scope, to find exactly where that star should be (if you look up and dont have a clue like me [8|] ) Now slew your scope to that star, align with the finderscope, then when aligning with your EP (remember the illuminated one) and line this up centre of the EP.
- The scope will now slew to the next star. Repeat the above alignment process.
- The scope will now slew to the final star. Repeat the above alignment process, and the mount will save it's settings.
NB: It may slew to a star that isn't in your visible view, the mount won't know that [;)] so you can cancel where it's heading and let it select another
(f) It should now return to it's "home" position. You can use the controller to do a GoTo. This should be in the FoV, and hopefully if you are accurate enough on the alignment procedure, be very very close dead centre to your FoV.

If you are always viewing from the same spot, alignment procedure will be quicker each time and the initial 3 star alignments will actually be closer to the star you are looking for.
If you are leaving the tripod / mount in the same spot and not moving it (i.e. covering it up and only removing the OTA and accessories), you don't need to redo the alignments, just make sure the mount has the correct time and date information.

I've been told to try aligning with the illuminated EP using a 2x barlow as well for more accurate alignment, but since using the illuminated EP, I was getting very very good alignments and tracking (2 mins +)

I've yet to try any kind of drift alignment, and in fact due to where I live haven't used the scope for a while (new housing estate = more light pollution!) I'm hoping to get out over the weekend, the above was a good test for me to see if I remember how to do it all properly :D

Good luck, hope that helps. There are rarely any problems with the CG5 mount, and there are also a number of modifications you can make to make it a very good mount for astrophotography and longer tracking times.

Luke
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RE: Celestron CG-5 GOTO Mount Problems

Postby quietquackers » Thu Dec 25, 2008 11:56 pm

Hi Luke
Thanks alot for your reply, unfortunately all of the problems stated in the original post are after accurate polar alignment [i]and [/i]a three star auto align.
I've checked the dates, location etc and the problems are all still the same. I think I've pretty much memorised the handbook by now aswell!
Also, having taken up some astrophotography, I have noticed that the tracking is also awfull - small star trails show up even on 30 second exposures.
Don't really want to blame the equipment, but I think I've got a dodgey mount!

Thanks
Adam
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RE: Celestron CG-5 GOTO Mount Problems

Postby astro_baby » Fri Dec 26, 2008 6:00 pm

It maight have been covered but what are you running the mounts power from ? Could poor power be the cause ?

I dont know about the CG-5 but the Synta HEQ5 and 6 both need very good power AND crucially when using GoTo a thicker lead from the power supply to the mount as the supplied one is too feeble to cope with the amps that an HEQ5 with GoTo draws.

HEQ5 and 6 mounts can suffer the poor tracking your experiencing when not powered with a) enough wallop from their batteries or power tanks and b) when using the supplied 12v power lead.

I have a non-GoTo HEQ5 and the tracking on that ( when polar aligned accurately ) is phenemonaly accurate.
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RE: Celestron CG-5 GOTO Mount Problems

Postby quietquackers » Sat Dec 27, 2008 12:40 am

I'm getting power from a Celestron 7Ah PowerTank but I am using the standard cable. Do you know where could I get a beefier cable from?

Been out tonight and thought I'd start from scratch. Mount properly balanced, calibrated and polar aligned. Still same problems though.
Just a thought, even though the mount isn't great at tracking, would using an autoguiding setup correct the tracking or would it still be useless?

Thanks
Adam

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RE: Celestron CG-5 GOTO Mount Problems

Postby astro_baby » Sat Dec 27, 2008 12:03 pm

Astronomiser do a beefier cable - take a look [url=http://www.astronomiser.co.uk/pwrhbx.htm#cpwr][b]HERE[/b][/url] - whether that would solve the problem I dont know. I know on Synta mounts the cable is the cause of lots of aggravation.
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RE: Celestron CG-5 GOTO Mount Problems

Postby ajd » Tue Dec 30, 2008 1:06 pm

How do you polar align it? Do you use the goto computer's polar align function? (forget using the polar scope as that is nowhere near accurate).

I've had this setup for 18 months now and I've never had any trouble except when I entered the wrong date! And even if I am way, way out on polar alignment a 2 star alignment gets slewing accurate enough for the target to be in the finder. Thinking about it, my goto computer does not have a "3 star auto align" feature...

My standard setup, which gets excellent goto results within 5 minutes is:
1. Set mount to index marks, use mount adjustment screws to center polaris in reticule.
2. Adjust finder to center polaris as well (so scope and finder are aligned).
3. Turn on goto computer, initialise and do a 2 star align.
4. Do a polar align from the goto computer (adjusting mount screws only).
5. Set mount to index marks and do a 2 star alignment again.

That gets me 30 sec exposures with no trailing. If I want up to 60s exposures then I have to do a drift alignment, which I do as step 4.5 in the above process, but this adds a whole hour to the setup time (as I am not so good at that). Exposures past 60 seconds is really autoguiding territory for a mass produced mount like the CG-5, which I am just starting to experiment with now...

Andrew.
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RE: Celestron CG-5 GOTO Mount Problems

Postby quietquackers » Wed Dec 31, 2008 2:26 am

Hi Andrew
I don't use the drift alignment method, but other than that my setup is exactly the same i.e. using the goto computer's polar alignment function.

As someone else said, I'm hoping that the RA and Dec locking clamps were too loose out of the box, I've now adjusted / tightened them but haven't had a chance to test this theory yet!

Adam
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RE: Celestron CG-5 GOTO Mount Problems

Postby ajd » Wed Dec 31, 2008 3:13 pm

I had to make that adjustment once, but that was my fault as I left the mount in storage for over a month with the counterweights still attached to it. Doh! I think that did some damage to the gears, which I eventually tamed by adjusting the worm gear tension and the clutches.

To be honest I wish I never had to do a drift alignment, I'm rubbish at it and it takes so long it's my least favourite part of the setup! I suspect a pier is my next investment. And then a EQ6-Pro. Then a roll-off obs. Uh oh I'm living in dreamland again! I suspect my better half wants me to get back to work and pay off some bills first [&:]

Andrew.
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