Skyliner 250PX Flex Tube Auto Tracking Dobsonian

[DaveGarland]

I'm kind of liking the look of this scope and would like to hear some views from anyone who has it. Is it good?

Also as I have fences around my garden, how high does it stand when the scope is at, say 30 degrees? And also how heavy is the whole thing?

Are there good alternatives also? My budget is about £700 tops.

Thanks for any advice.

Dave.

[Crunchard]

I've got one and love it.

It is a fair lift for me and I consider myself an averagely fit 40 year old.

The tracking is excellent, get it level, follow the instructions and it rewards you keeping the object in view for a long while (20mins easily when I was looking at Cygnus/Deneb the other night).

Fully extended it stands about 5ft high I reckon - never measured it to be fair. When aiming at low declination objects I still have to bend my back - but then most scopes will put you in a strange position or two!

The only slight downside is it needs collimating every time it is used. I find it just doesn't keep collimation, no doubt owing to the truss design and the sliding up and down. But that is minor and only takes a minute to correct.

There is also no obvious counter-balance method for large EP's. I actually use a selection of fridge magnets - no drilling and they don't seem to mark the scope.

I'm sure others will chip in with their own comments too

I was able to have a good play with one before I purchased. So could see the design, size, test the weight, etc. I would recommend doing that

Cheers, Jeff

[swamp thing]

Hi Dave

A 10" scope is a really powerful tool and will show a wealth of objects very well indeed. I personally think this size is THE Goldilocks of scopes: Not too big that you will refrain from observing because of the agro of hauling a big scope out, and not too small that DSO show very little detail if anything at all.

However some would call a 10" a huge lump of a scope. it depends on your point of view, and level of fitness/strength. Therefore I would strongly urge you to go and see one in the flesh before making any decisions.

Good luck with your choice

Regards Steve

[DaveGarland]

Thanks guys. I guess the height sounds ok and I suppose it wouldn't be too difficult to set up a raised platform if I find myself disappointed. I'm also a reasonable fit 40 something year old so as long as it is manually moveable I should be ok. It'll give me another reason to keep up the gym work too

Dave.

[DaveGarland]

Oh, also, how steady is the mount? At the moment I have an EQ2 and it wobbles like a good un as we say in the west country. I'm assuming Dobsons are more stable.

Dave.

[Crunchard]

Rock solid ... except in high winds

[brantuk]

Infinitely more solid and stable than the EQ2 and very powerful as mentioned above. Best tip I ever had was to get an adjustable ironing chair for mine - it really takes the strain out of back bending for lower altitudes - and a snip at under £20 from amazon.

My 300P holds collimation for one or two sessions - it's a question of balancing up the tension on the trusses with the sprung ball bearing screws at the base of each truss. They need to be just tight enough to let it glide up and lock in place.

The tracking is good if you set up as per the manual to counteract any backlash or slop. The axis tensioners might need a small tweak but I'm going on the 12" - the ten might be better. I get 30+ mins before noticeable eyepiece drift. Highly recommended (by me, and Paul Money in SaN lol).

[derekm]

The adjustable ironing stools crop up a couple of times a year in the Lidl specials for about £15. Most other places ask silly money, up to £40!!

Aldi may do them but I don't recall.

[DaveGarland]

Brantuk, I've had a look on eBay for an ironing chair and I found this one. You might need to lend me a few bob for the postage though!!!

http://www.ebay.co.uk/itm/IRONING-PERCHING-STOOL-CHAIR-/250890946242?pt=UK_Health_Beauty_Mobility_Disability_Medical_ET&hash=item3a6a4406c2#ht_500wt_922

[Paulb3098]

Dave

I went from a SW150 EQ3-2 to the SW250px, great scope far easier to set up with a two star alignment and I have had some really great views. Fully extended it's 140cm / 4ft 7" (that’s my eight year old son in the picture). Only downside is it's fairly heavy, tubes 15kg and base is 18kg. Good luck. Paul

[Wildwood]

I love my 250px.

Really easy to set up and great at tracking. I too use an ironing chair and find it really comfy when used for long periods.

The only down side to this scope is the size (given that I keep mine extended at all times it can be awkward to manouver through doors when coming in tired). I'm 6' 4" with a bad back but can manage the weight easily enough in two trips.

I made a dew shield and shroud out of a cheap exercise mat from Sports Direct and they work a treat.

Collination is easy ( I replaced the secondary grub screws with some knobs) and takes a few seconds with a laser collimator.

If I had to be picky I would say that moving the scope at it's fastest speed can be noisy.

[DrRobin]

Hi,

I am having trouble with my 250 flex tube auto, modded to AZ Goto, it doesn't appear to track very well.

Some nights I can get it so so and others it's just hopeless. I have tried balancing and adjusting the tension nuts but most settings don't seem to make much difference.

Here's what happens, I align on brightest star in the North West and it then chooses something to the North for the second star. The second star is usually outside the field of view or close to the edge on the 25mm EP, not a good sign for starters. Then when I select an object, it goes to near it and I need to use PAE on the Goto to get it right.

Now the big problem, the tracking appears to 'lag' in both AZ and Alt. Centring on a star requires new adjustment after say 10 seconds to get it exactly centred and if I try DSO imaging, I am usually rewarded with star trails.

My problem appears to be in both axis, I have a largish battery, but wonder if it either isn't working properly or if there is a bad connection. There is no flickering on the handset though which I might have expected to see.

It looks to me like the motors don't start up quickly enough or there is some slip, but I thought these had dual encoders which should take care of that.

If I use the auto track handset, it's no better, except I don't have the luxury of the Goto pointing.

Anyone had similar experience and a solution?

Regards

Robin

[DrRobin]

Hi,

I have thought of a way of checking all the motors, battery and handset.

During the day, point the telescope on a object on the ground, align it with right and down movements, note the coordinates.

Slew the scope say 10 degrees in AZ and then slew it back to the object, again centring using right, down shouldn't be necessary. Compare the position with that noted before.

Repeat in Alt and repeat for different slew rates. If the encoders and motors are working correctly then the position should be the same every time the scope is brought back to the original position.

I can then try different nut tensions to find the optimum, I.E. Tight enough to stop slop or drop, but not so tight that the motors can't turn the scope easily. Ditto for different batteries/power supplies.

Since this test allows me to separate out the AZ and Alt axis, it should be obvious where the problem lies. It will also be quick to do and doesn't waste night viewing.

Once it is doing this correctly, if it doesn't track correctly then it is something to do with the handset or the date/time/location/level.

I will try it tomorrow and report results.

Regards

Robin

[Space Cowboy]

Batteries are not recommended any reduction in voltage will mess up the tracking.

[DrRobin]

Hi,

Thanks for the quick reply. The battery is a 7Ahr sealed lead acid, it's fairly new, 3 months old. I would have thought this was okay, but if you suggest a power supply I can arrange that.

Any idea of the current these scopes draw? I could measure it as I am an electronics/electrical engineer.

Regards

Robin

[Space Cowboy]

My mistake I thought you meant small batteries. That 7Ahr one should be fine. Sounds like you know a lot more about power sources than me lol

[DrRobin]

Hi Space Cowboy,

Thanks for the reply, I realised when I said batteries that it might mean anything from something you would use in a torch to a large battery bank for standby power.

I realise I should have said Power Tank. Thanks for your reply though. Have you had any problems with tracking?

Regards

Robin

[Crunchard]

I think you will find the dual encoders are only the actual goto model.

Whilst the goto will function (are you using the latest firmware release on the handset?) you cannot push it around and then expect the goto work once done unless you have the offical goto mount.

That said I had the goto handset for a while, but in the end decided to go back to manual searching.

The tracking on the track only option is superb.

What I would do is test just the tracking option if you can - remove the goto handset from the equation.

I can easily get 25 minutes with very little deviation from the target.

And now suck eggs time ... follow the instructions in the manual for aligning, levelling and setting home.

Good luck!

[DrRobin]

Hi Crunchard,

Good advice, thanks.

My flex tube does have dual encoders, there is one on the back of the stepper motor and a second attached to the shafts connected to the two axis, under the black covers.

I am not trying to push the tube around when in Goto and then expect it to track in Goto, but if I do, it's position updates on the handset, just the same as if I use the control buttons.

I do try to set up the mount as per the instructions and suggestions elsewhere and the Goto handset is ver 3.07.

I will try the auto-track handset again, but from memory that doesn't track very well either. In fact I think the Goto handset tracks better than the auto handset.

I didn't have the Goto handset originally and had some problems with tracking with the auto handset.

Regarding your 25 minutes, that is excellent, at the moment even 25 seconds is difficult enough.

Regards

Robin

I will let you know when I have found the problem.

[DrRobin]

Hi all,

Not sure it will solve my problem but noticed that the latest firmware for AZ Dobson is 3.08. This has corrections for Dobson with dual encoders to correct if the scope is moved manually.

Has anyone given 3.08 a try?

Regards

Robin

[Space Cowboy]

Hi Space Cowboy,

Thanks for the reply, I realised when I said batteries that it might mean anything from something you would use in a torch to a large battery bank for standby power.

I realise I should have said Power Tank. Thanks for your reply though. Have you had any problems with tracking?

Regards

Robin

Quirky is what I would call the tracking Robin. I had my mount replaced under warranty during the summer after tracking issues and a dodgy motor. The new mount is working well as I'm using the scope for Planetary imaging. I too have the GOTO handset alongside the auto-track and its the auto-track i'm using for imaging. The alt axis has a tendency to slacken off after a while and needs the nut giving half a turn.

With the original mount it always tracked fine in the western sky but constantly lost altitude in the east. As yet I've only been imaging in the west with the new mount so time will tell how well it works overall.

I've only used the GOTO handset once with the replacement mount and the tracking was horrid but this was probably because I was careless star aligning using Vega which was too high. Always make sure you use stars lower in the sky when aligning and use the "2 star" alignment. When the scope is set pointing north at 0 degrees at start of session make sure the "up" button is the last one used when leveling the scope. This is very important when using auto track and when the object is centered before activating tracking again finish with "up". If tracking drifts then de-activate tracking and re-center.

Try and use a high power eyepiece when star aligning or setting up tracking to gain that extra accuracy.

The GOTO handset will never be spot on but it gets the object within view of a wide-angle eyepiece i.e 32mm.

The number one important point is make sure the mount is perfectly level. I have mine sitting on a leveled paving slab.

Don't know about v3.08 I don't think it makes any difference.

[DrRobin]

Hi,

Interesting you had problems with your mount, I had to send two tubes back to them due to large dents in the side.

I appear to have tracking issues over a lot of the sky both with the Goto and the Auto-track so I am thinking it must be something to do with the mount.

My main problem appears to be that the tracking lags behind, so I am thinking it is either the motor which is not strong enough to overcome the friction (might be the nut is tto tight) or the power supply/supply cables are not up to job.

My day based static test will prove if it is the motors. If that works okay then I am going to make sure I clear all of the PAE as that is retained and PAE from poor alignments might be upsetting the tracking accuracy.

I have also had a read through the manual very carefully, once aligned on 2 stars if I use the Goto to go to eithe rof these two stars they should be absolutely spot on, I doubt mine is, again this would indicate some sort of slewing/tracking issue.

Finally my base is very level, I constructed a concrete slab, levelled and then hidden under a trap door in my decking. I open the trap door and put a low heavy table on to the slab and then stand the Dob on the table. I can the walk around the decking without transmitting any of the vibration to the scope as the decking and concrete slab are independant. I am not sure how level it is, but with a good spirit level (and bullseye level) it is exactly in the centre.

I will not get chance to make my day time test until tomorrow and I am out tonight so no observing even if it is clear, but I should have the answer by tomorrow afternoon.

Regards

Robin

[Crunchard]

Hi Robin,

When I had my AZ Goto handset it had 3.08 on it. No issues that I can remember.

I'd certainly give that a goif it were me.

25 seconds is not that clever at all, hopefully it isn't anything too serious!

Cheers, Jeff

[DrRobin]

Hi Jeff,

Thanks for the advice, I think I will give 3.08 a try, still not sure that is the problem. Hopefully tomorrow will prove what the problem is and if it is anything major it's only a few months old so it will have to be a warranty claim.

I am fairly sure that both handsets have th same problem so I think it is a motor, power cable, nut tension issue.

Typical it's clear tonight, but we were going out and back late so no chance of any viewing.

Regards

Robin

[Pingster]

Go to DIY shop and get some quality 5in wheels on it. Will make it a pleasure to "grab and roll" from your shed.