Celestron Nexstar SLT Mount woes.

[HDJ]

Has anybody got one of these and had problems with Skyalign and the GOTO features?

Got a new one the other day and I have aligned it on a few occassions now and each time I do it say's it has completed with success, yet when I tell it to GOTO an object it ends up miles off (probably a few light years hehe).

I've tried Skyalign, Auto one, two and three star align and also Solar system align.

Tonight I used Saturn, Sirius and Betlgeuse (sp?) as the three alignment stars, accepted! great I thought, can;t go wrong using these bright stars can I.

Told the mount to GOTO M42 (Orion Neb),, off it went about 65 degrees away from M42?? wtf I thought.

I then aligned it to Saturn and Mars, then told it to GOTO the Moon, it missed!

Ended up a good 5 degrees off to one side and down a bit.

I'm setting location, date and time correctly, so how does this mount get so screwy on simple objects that a 2 year old could point out (the moon).

Also when set to Lunar Tracking after I have self aligned it, it seems to track too slowly.

Any Ideas? or is it FUBAR'd?

[Kai]

I wouldnt think the Mount is fubar'd .I recon 90% of problems we (including me) have is not entering the info correctly, the date format being the most popular.

I havent used one of these mounts but can you really select Saturn as a alignment 'star' , on my Skywatcher you cannot.

Im sure one of the members with a Slt will chip in soon.

[davekermito]

You can select any bright planet or the moon on the NexStar.

As Kai says, check the format you are entering the date in. It had me bamboozled for a week or two!!

mm/dd/yyyy

Also, it eats batteries. Even a small amount of use will cause inaccuracies with the minor loss of power. If you can use a mains supply to test, you can rule out this straightaway.

[dogfish]

Also, it eats batteries. Even a small amount of use will cause inaccuracies with the minor loss of power. If you can use a mains supply to test, you can rule out this straightaway.

Dave has the answer, I reckon. I had a 6SE and tried it first with 8AA's. Wouldn't even last a session and produced the kinds of problems you describe. Get yourself a power tank (if you don't have one already) and try that. Another possible problem is the daylight saving setting. The correct setting is daylight saving off and Universal time. Also, location is in hours, minutes and seconds; and not the digital format - depending on your location, it can be possible to enter location in the digital format.

HTH, Martin

[dave1978]

I have similar issues with my 102Slt! I use mains power, dates, locations etc all correct. I have tried the SkyAlign to no avail and if i use Solar Align on say Mars and then slew to another object its always just off (up and to the left slightly). At first i thought it was down to the tripod not being level so as it slewed from Mars to the right it went off! So next time i paid more attention to getting it as level as i could but with the same results. I previously owned a Meade ETX-70 and never had alignment issues with that so i feel i know what im doing but just cant get the Nexstar right!

Its starting to do my nut to tell the truth as are the ridiculous levels of vibration when focusing or moving the scope (how the hell are you supposed to focus well when the scope is vibrating like im in a MAG 6 quake)

Makes me wish i could put the 102 on a Meade tripod and align with that, also the Meade had no issues with vibration.

[HDJ]

Same here Dave,

All the locations and time formats are correct.

UT and Daylight off.

Clock wa sset using my Radio clock so is as correct as possible.

I am using AA's at the moment but these are high capcity ones and so far 3 sessions and they still work fine. 2Ah plus per cell.

Gonna give it one more go later, as I wanted this for tonights Lunar Eclipse for webcam tracking.. looks like I'll be using prime focus on the Dob instead.

will report back on this.

[George]

I no longer have my SLT120 but it was fairly accurate running on mains power. GOTO put the target in a 25mm fov everytime which i thought was pretty good for a sub 300 quid scope.

[John]

I am using AA's at the moment but these are high capcity ones and so far 3 sessions and they still work fine. 2Ah plus per cell.

I reckon mounts of this type are extremely sensitive to the power output - if the batteries are even a touch below max output they appear to be working but the errors start to creep in.

Before blaming the mount I would definately try a session with it connected to a mains supply or powertank.

John

[HDJ]

Will do.

I'll hook up a 7Ah supply yo it the next clear night I get.

[palefire]

I've got one of these mounts, and as indicated above, they are very sensitive to power inputs. Looking at your comment "2aH plus per cell" I'm assuming that you're using rechargables. The important thing to note with these is that they don't output the required voltage (1.2V, not 1.5V) when multiplied by 8 this makes a big difference (9.6V rather than 12V). So, while the batteries are not running down and are still holding a charge they aren't able to supply the necessary voltage to power the mount.

[HDJ]

A very valid point indeed!

I'll certainly be testing it next time out with a 12V lead acid battery and a mains powered unit.

[palefire]

Good luck with that HDJ. I've been powering mine with a Maplin's jump starter pack (20 quid in the half price sale) which comes with the cable you need to drive the mount too.

So far I've been pretty impressed with the GoTo & the tracking. I'd only set the mount up very roughly (location set to Bristol, not Cardiff, quick + rough align) and the mount put the targets into the FoV of a 32mm Plossl every time and tracked things for half an hour with little drift. It's been brilliant for finding open clusters (I've always found 'em pretty hard to pick out).

After touring 'round for a couple of hours I got the mount to slew back round to saturn (one of the alignment 'stars') and it dropped it into the FoV of the 9mm eyepiece I'd left in the scope.

By the way, I'm using the mount with a C5 OTA, so the FoV is pretty narrow (in comparision with shorter f-ratio scopes).

[HDJ]

Success!!!! :hello1:

Ok, the scope is indoors and shooting through double glazing but it works!

I'm using a RC battery 12V 1.7Ah, fully charged.

Alignment works a treat and tracking.. wow it actually tracks and keeps the object dead centre for quite some time.

So consider myself duly ashamed for not figuring out the voltage drop by using Ni-Mh batteries.

I also have one of those Maplin Booster Packs on order, might arrive in the morning but I think Monday is a safer bet for that.

I've managed to snap some 30 second vids of Saturn and the Moon using the GOTO and tracking, though they have severe ghosting due to the angle of the scope Vz the double glazing.

Once I've sorted some extension cables out I can remote control it all from indoors on cold nights

One thing I have found however, is the Nexremote software doesn't sync with the hand remote.Once the hand remote is set and aligned you'd think the software would read that and sort itself out. As soo n as you remote control with the software all the tracking goes to pot.

Apart form that all I need now is a remote focuser.. save me a load of time that would.

So thanks guys.. with your help I have solved my initial problem.

Before I end this post, Do all Nexstar remotes not keep track of time, each time I turn it on it remembers the clock time when I last programmed it, even though it may have been running and tracking for over an hour. Is this a bug or just the way it is.

No hardship entering the correct time for each use, but you'd have thought that would be a basic feature that it could keep track of the time itself.

[davekermito]

Before I end this post, Do all Nexstar remotes not keep track of time, each time I turn it on it remembers the clock time when I last programmed it, even though it may have been running and tracking for over an hour. Is this a bug or just the way it is.

It's very annoying isn't it?!

I'm glad you've got it sorted. Now all we'll get is cloud!

[palefire]

glad that it's panned out alright for you.

No, the controller needs telling the time each time you restart the mount. Annoying, and a simple thing they could do to smooth the process markedly.

I also think they're missing a trick with regard to the internal battery packs - it's clear that usual rechargables don't work, but they could sell custom rechargable packs like you get for laptops etc. The mark up on these things are quite high, but I'm sure a fair proportion of goto mount owners would shell out for the convenience (particularly for the SLT/SE type mounts where portability is the aim of the game).

The Maplin jump start pack works well with it, but I could do with getting some velcro to put some slack in the cable (and maybe a longer cable). Only lost power the once, but it'd e nice not to worry about it.

[HDJ]

I use a slim RC (radio Control Car) battery at the moment.

12v 1.7Ah, so lasts a while and fits perfectly on the mount tray underneath the scope. I made a lead for it that gives loads of slack so no problems there.

The Yuasa type batteries that you fond in alarm panels would also be a good solution.

I have the figures from the manual regarding the power consumption but some time this week I'll hook up a couple of DVM's and measure these in real time so I can get an exact reading on power usage, this will help me work out the best battery for the mount. If the RC battery fits the bill it can stay put.

I have some wooden tripod legs from an older mount, and these will fit the Nexstar motor head, so I wonder if these would make a worthwhile upgrade to reduce vibration etc.. they are also much longer so would provide lots of extra scope height adjustment.

The downside is portability, though I think the quick release plastic tray from the Nexstar tripod will fit the wooden legs... gaining back some portability in terms of fold-up time.

Will report back soon with how all this goes.

[thumbless]

Glad you got your problem sorted.

So it was all down to power supply.

That is another point i will remember when choosing a Goto

Thanks

Davey.

:moon:

[dave1978]

Sorted my problems out too! My alignment issues are all down to the built in bubble level on the Nexstar mount! Previous nights i have always used this to level the tripod and thought nothing of it but last night i decided to check using a proper spirit level and to my supprise it was quite a way off being level.

Oh well bear this in mind in future and never rely on the built in unit!

[HDJ]

Yes, good point.

What I might do is setup a flat section of ply or mdf etc.. and get it perfectly level then stand the tripod on there.

Thus having a reference point to adjust and the stand legs and/or the bubble itself.

Also an UPDATE:

I fitted the wooden legs and also transfered over the Nexstar plastic tray assembly.

Only minor alterations were required, had to drill out the mount leg holes by a couple mm in order for the larger and far sturdier bolts to pass through and I also moved the pins lower down that held the original tray on the wooden tripod.

It's far better now, more stable, greater height adjustment and the best part is it is 100% portable, a quick turn on the tray and th elegs all fold in to the centre making it very portable in approx 5 seconds.

My next plan for it is where the AA's were once stored under the cover I might make that the new home for the USB hubs and camera mod boxes.

USB to serial etc...

This way it keeps all the wiring very tidy, and I can fit some sockets to the cover so that there doesn;t have to be any trailing cables when the imaging is not in use.

For the money this mount is easily the best value for money I've realised from my astronomy purchases.

[Helen]

That sounds interesting! have you got some pictures of your mods?

Thanks

Helen

[HDJ]

Hopefully, here are some pics.

(click to enlarge)

This picture shows the Triangle in the center of the tripod legs. This is the original Nexstar item transferred to the Wooden tripod legs. It's very fast quick release design allows the tripod to be gathered up in seconds. Prior to this the original centre was bolted to the wooden legs and took time to unscrew and assemble etc.

(click to enlarge)

The photo above is an overview of the wooden tripod with the Nexstar mounted on top. This is obviously in it's gathered state which makes it very easy to pick up and walk around with, especially through doorways.

(click to enlarge)

This photo shows the battery compartment with the plastic top and tray removed. There is ample room here for mounting USB mod boxes for camera use and the cables/wires you see are the original AA battery feeds, since these supply a nice 12V from the external supply I will no doubt modify this feed to supply an external 5V for the USB and Camera supplies, thus removing the need to add voltage stabalizer circuits to add-on mods.

For the money these mounts do offer a good level of useage for small scopes and as can be seen can be modified slightly to better suit the end user.

[Helen]

Thanks for the pictures - I might try modding the tripod myself (its rather wobbly isn't it?)

Helen

[HDJ]

Mine wasn't so bad, however with the heavier tripod and larger bolts etc, it's certainly more rigid now than before.