Auto-guiding for Skywatcher 130P Supatrak Auto

[redstamp]

I was bought a telescope for my birthday a couple of years ago and have been slowly getting into the hobby - trying a few imaging techniques but nothing overly successful - webcams are my next project, but currently using my Nikon D7000 attached to the telescope.  The auto-tracking on my skywatcher explorer 130p supatrak is OK, but cannot hold anything in the centre of the viewfinder for long, esp at high magnifications.

I have been researching this forum and have been considering improvements to my technique:

1) a counterweight to offset the camera weight which may be affecting the tracking

2) auto-guiding set-up to adjust the telescope automatically

Realise a heavyweight EQ mount and separate guiding scope and dedicated auto-guiding unit will get better results, but will probably cost an arm and a leg and probably require a complete refresh of all my current equipment.

So I have two questions:

1) Will a counterweight make a significant difference, or should I just concentrate on accurate telescope alignment (I already use the compass and spirit level in my iPhone - outside range of telescope interference)

2) In terms of auto-guiding, I presume an economical way would be an eyepiece splitter (one for imaging and one for auto-guiding) and attach webcam + laptop with relatively cheap guiding software & attach laptop to telescope RJ11 port?  I cannot find anything on the forum / web about whether my telescope can be used with auto-guiding software like this, although it has an RJ11 port for the controller handset, so presume all the fundemental elements exist?

Thanks in advance for all advice and help.

[Kropster]

I think the Supatrack is an alt-az mount?

For astro photography you really need an equatorial, otherwise you will get field rotation even if you can keep the object in the centre. 

It would only be any good for very short exposures such as moon shots.

[szymon]

Yours is an alt-az mount, and won't really track well for longer exposures.  The 'sidereal tracking' it does is an approximation at best, good enough for visual but not for astrophotography.  I would suggest you look around for a second hand equatorial mount with a motor which will allow for true sidereal tracking.

[jambouk]

1. Worth a go, but don't exceed the reported weight limits for the mount as the motors won't be happy. Try to balance it all as best you can. How are you powering it? If using AA batteries, think about upgrading this to thing like a car jump start unit or a leisure battery if you can get your hands on one - a nice reliable power source may improve things a bit. Whatever, you want to get as good a set up with your kit as possible; lots of threads on here about how to do that with this mount - level, stable, correct data, balanced, high mag eye piece (reticle one) for star aligning etc...

2. You are always going to have field rotation with an alt-az mount, which is going to limit your exposures to 20 seconds at top i guess, so i can't see an advantage of trying to get this working.

Lots of people manage some great basic imaging with this mount and scope, again search on here, but they work hard to achieve that. If you want to get that quality you need to sort out your power, balance, setup, focus and processing first. If you want "better" images, or go for fainter targets, you really need an equatorial mount, and i'd suggest a different telescope.

Let's see some of your images.

I'm glad you are having fun with it all.

As always, get involved with a local astronomical society and/or observing group and see what kit others are using and what results they can achieve.

Good luck

James

[redstamp]

Thanks guys, always useful and informative!  I kinda thought I may be advised to get an EQ mount, as this is what everyone else seems to be using for photography.

jambouk - I am using AAs, so will take your advice and invest in a powerpack, as seems will be re-usable whatever kit I end up with.  I had thought field rotation could be removed using stacked images in Deepsky Stacker, although maybe I mis-understood something about this software.

I have (rather unsuccessfully) been trying multiple exposures using my iPhone and TriggerTrap app / dongle to set-off the Nikon in mirror-up mode.  Trouble is scope goes out of alignment quickly as this isn't a quick way yo get multiple images - hence the auto-guiding query.

Have tried just with camera with TriggerTrap but haven't really got deep enough pockets for a fast wide angle lens!

Apologies for seeming to talk about photography now as probably shuold have posted in the other section.

Anyway - onawrds and upwards - thanks again.

1. Worth a go, but don't exceed the reported weight limits for the mount as the motors won't be happy. Try to balance it all as best you can. How are you powering it? If using AA batteries, think about upgrading this to thing like a car jump start unit or a leisure battery if you can get your hands on one - a nice reliable power source may improve things a bit. Whatever, you want to get as good a set up with your kit as possible; lots of threads on here about how to do that with this mount - level, stable, correct data, balanced, high mag eye piece (reticle one) for star aligning etc...

2. You are always going to have field rotation with an alt-az mount, which is going to limit your exposures to 20 seconds at top i guess, so i can't see an advantage of trying to get this working.

Lots of people manage some great basic imaging with this mount and scope, again search on here, but they work hard to achieve that. If you want to get that quality you need to sort out your power, balance, setup, focus and processing first. If you want "better" images, or go for fainter targets, you really need an equatorial mount, and i'd suggest a different telescope.

Let's see some of your images.

I'm glad you are having fun with it all.

As always, get involved with a local astronomical society and/or observing group and see what kit others are using and what results they can achieve.

Good luck

James

[jambouk]

Yes, if you are getting field rotation over a series of images the stacking software will get rid of it, but the area which stacks well will get smaller as you image over a longer period of time, and if you are using a long focal length scope like a skymax 127, that will be a very small patch of sky.

your mount clicks left and right, and up and down, whereas the sky is apparently turning in a circular motion. So if you did an exposure of say 60 seconds Even though the scope may keep the target bang in the centre of the field of view, it will be blurry at the edges as the field is rotating as well as going left/ right and up/down...

So, even if you guide, with alt az, your exposure length will be very much more limited than if you had an equatorial mount.

James

[jambouk]

If your target is drifting out if the field of view very quickly, it suggests to me your set up and alignment is poor, or could at least be better. There are various threads on here on how to tighten this up.

James

[rowan46]

If your target is drifting out if the field of view very quickly, it suggests to me your set up and alignment is poor, or could at least be better. There are various threads on here on how to tighten this up.

James

I was going to suggest the same thing. I am not overly familiar with this mount but from what I understand you point the north leg north and then the tracking takes over. I would assume that the more accurately north it is pointed the better the tracking

[jambouk]

There is no north leg on the synscan goto mount (well not on the one i have); there is an option to start the mount pointing north and relying on that for accuracy, but there is also an option to do a two star alignment (after levelling and other set up steps) which can result in very accurate goto and tracking.

James

[Herbig]

I had a Supertrak mount and I found it was almost impossible to get it to track with any accuracy.

As far as I know this mount does not have an auto guide port?

Also how would you attach your counter weights?

I think if you want to get decent results you are going to have to get your self an EQ mount.

I have seen second hand CG5 GT's for about £385, you should also be able to sell your Supertrak for about £100.

It will save you a lot of trouble in the longrun.

[jambouk]

I know if you are meticulous with the set up, and maybe a chunkier power supply helped i'm not sure, i could leave the mount tracking an object and it would do very well, keeping it in the centre of the fov for 30 munutes plus. The issue is field rotation. If you want subs longer than 20-30 seconds or so you will get noticeable field rotation on every sub which stacking software won't be able to cope with; duration will depend upon focal length i suspect.

As i said above, i think, various people have done some really impressive stuff though with this kind of mount, it just means stacking hundreds of 20 second subs.

If you want to take longer subs get an equatorial mount.

James

[rowan46]

There is no north leg on the synscan goto mount (well not on the one i have); there is an option to start the mount pointing north and relying on that for accuracy, but there is also an option to do a two star alignment (after levelling and other set up steps) which can result in very accurate goto and tracking.

James

I klnow thats true of the synscan but the autotrack doesn't have goto unless you buy the synscan handset or so I understand (i have never seen a synscan enabled one Only the threads by people who have done it)

to the op 

I believe the supertrak has been used by some people for webcamming but it isnt suitable for any sort of long exposure work

[jambouk]

Ah! I have only been talking about the synscan one with goto, sorry

James

[jambouk]

Maybe get a synscan handset then? £80-100 second hand often on astrobuysell. But you might as well put that towards an EQ mount.

James

[rowan46]

I think if you want do some photography you would be better off selling your scope and putting it towards a seond hand  cg5gt or eq5 synscan (the cg5 is better but noisier) and a 130pds its probably the cheapest way into long exposure astro photography

[Herbig]

As I mentioned above I had a Supertrak which I used for my PST, got fed up with it as it would drift off target in 20-30 minutes at best.

Now got a Celestron SE which holds the target all day.

A well set up motorised EQ mount will do the same all night with no field rotation.

[Cornelius Varley]

As I mentioned above I had a Supertrak which I used for my PST, got fed up with it as it would drift off target in 20-30 minutes at best.

Now got a Celestron SE which holds the target all day.

A well set up motorised EQ mount will do the same all night with no field rotation.

20 - 30 minutes isn't that bad considering that the Supatrak mount only has a very basic alignment (raise the telescope to your latitude setting and then press SET/LAT on the handset). The Se mount is a full goto that can use the Sun as a alignment point, so it will be able to track better in the daytime than the Supatrak.

[redstamp]

Thanks so much for the help chaps (& chapess' if relevant), couple of responses to your exceptionally helpful comments:

As far as I know this mount does not have an auto guide port?

It has an RJ11 port which the (basic) handset connects to in order to control the mount motors, so I was presuming that was enough, provided the software knew what it was doing to the telescope, ie understood how much to drive the motors and in which direction.  Linked to auto-guiding, presumed there would even be a feedback loop, so the auto-guiding should work out what it's supposed to do based on how much the target moves when it does tell the mount to move... or maybe I am just being overly-simplistic in my reasoning?

Also how would you attach your counter weights?

Great question and one I had been pondering.  Wrap something around the base of the scope which will hold a weight on the opposite side to the eyepiece (where the Nikon is mounted)

As i said above, i think, various people have done some really impressive stuff though with this kind of mount, it just means stacking hundreds of 20 second subs.

Indeed - that's what I was planning, as I thought this was better for removing noise as well.

There is no north leg on the synscan goto mount (well not on the one i have); there is an option to start the mount pointing north and relying on that for accuracy, but there is also an option to do a two star alignment (after levelling and other set up steps) which can result in very accurate goto and tracking.

The instructions just said point North in the level position and press 'set' on the handset (after setting the latitude).  Didn't see anything about 2-star alignment, but this maybe just for Synscan Goto and I just have the Supatrak.

Maybe get a synscan handset then? £80-100 second hand often on astrobuysell. But you might as well put that towards an EQ mount.

Didn't realise you could upgrade handset, so will definately take a look, although the mounting advice seems to suggest sell everything I have and start again now that I have an itch that needs scratching ;-)

I think if you want do some photography you would be better off selling your scope and putting it towards a seond hand  cg5gt or eq5 synscan (the cg5 is better but noisier) and a 130pds its probably the cheapest way into long exposure astro photography

Brilliant - just my luck  FLO had a clearance sale for the last year(!) on these and sold the last two in May!  Oh well, looks like I should be saving pennies whilst learning my way through the hobby to invest in a complete set-up and look for second-hand stuff which may save me 20%...

Thanks again,

Jon

[redstamp]

20 - 30 minutes isn't that bad considering that the Supatrak mount only has a very basic alignment

I'd be over the moon with 20-30 minutes - I might get 2 - 3 minutes using my 3x Barlow on my Skywatcher 130P before the target disappears stage (top) right

[Cornelius Varley]

If your mount is the Supatrak, without the Synscan handset, then autoguiding the mount would not be possible- you would have no way to interface the mount to the guider software.  Autoguiding an alt-az is not going to work either due to the limitations of the mount (field rotation) so a limit of 30secs max exposure is probably all that the mount is capable of. Even if you could connect the GOTO version of the mount up to the autoguiding software would struggle to control the mount in two axis over longer exposures.

[jambouk]

To get the "pointing north" bit correct, could you level the mount, point the scope to polaris, then just drop the altitude axis (no moving the azimuth) until you get the scope level (spirit level level), then start your mount up again from that position... Just a thought.

James

[Herbig]

I think you are getting the message from the advise here that trying to get your mount to guide is going to be a waste of time no matter how hard you try. To upgrade it to SynScan could be done but it's going to cost you £80-100 and youd be better off putting that cash towards an EQ mount.

[redstamp]

I may have misunderstood of the purpose of auto-guiding - I was looking for auto-guiding capability in order to keep AP targets within the eyepiece for sufficient time to take a couple of hundred frames on my DSLR ready for image stacking.

I am however getting the impression from the responses above that (good) auto-guiding is mainly used to generate exposures of long lengths, and probably using dedicated AP cameras.

Would this be a fair assessment?

Thanks.

[jambouk]

Guiding is conventionally used for longer sub exposures yes, but on a well aligned (polar aligned) equatorial mount. Even if you could guide your mount, and keep the subject in the centre of the field of view, a long sub (30 seconds +) would be all smeary due to field rotation as it is an alt az mount.

But if you could "guide" and just took lots of short subs, say 10-20 seconds, you would minimise the field rotation on individual subs, but over an hour or so there would be lots for the stacking software to deal with, and depending on your fov, there might only be a small area of the object actually visible.

But as you've seen, this can be done.

I think the costs and hassles and fact no one else has seem to have done it suggests to me it is something i wouldn't bother doing, especially as you will still have very limited results even if it did work.

If you really can't get the tracking to be better on your current set up, i'd say try with a synscan handset to see that that improves things. If that fails, i'd look at just getting an equatorial mount.

Where are you in the country? I have a spare synscan handset you could borrow for a few weeks.

James

[redstamp]

Where are you in the country? I have a spare synscan handset you could borrow for a few weeks.

James

I'm in Newbury.  That would be fantastic if I could borrow one to try out.  Can I pay for postage, as I dont often pass Nottingham - perhaps we should PM?