Synguider through Finderguider problems...

[MikeWilson]

Ah ok, with you now.

No vignetting on my setup. I've got the Skywatcher reducer/flattener in there aswell and have never noticed any problems. I did when I used my old WO66.

I can see why you would want it in there, that would be no fun at all, you'd probably need to lay down flat to have a look through.

I'm with you too, Sly.

Three times now I've had slipping of the Synguider which I think could be reduced by removing the diagonal. The first time was when I accidentally twisted it. The second time when I had to remove it to check that a star was in fact in the field of view (something happened and I lost it) and the third time I put the hand controller down and my new kitten decided to leap onto it.

The hand controller is a bit of a liability in my opinion - it's wide and flat and very light and hangs at the end of a rather tough wide flat wire. I wonder if it's possible to mod the cable with something more flexible like the SynScan hand controller cable...

[simon84]

Might be worth seeing if you can add a bit more tension to the focuser aswell, I had major problems with that but found a single grub screw underneath the focuser that could be tightened up to add more tension.

Not sure how to do it on an ST80 as its a rack and pinion but there must be something there to give it more bite.

Can you velcro the hand controller to the side of the scope or somewhere near the synguider?

Oh no not the hand controller cable, someone needs to tell Synta that curly cables are a load of old rubbish and only hinder the whole experience.....lol.

[MikeWilson]

If the curly cable is bad, this one is worse I assure you!

I'm currently having trouble focussing on stars. The seeing tonight is awful. I can barely make out Casseopeia from here and with Vega that's about it. There are other stars, but if I wasn't guide testing I'm not sure I would be making the effort today.

However my main OTA and guide scope are definitely not aligned at all. Will see in a moment if that makes any difference.

Incidentally, does anyone know what time the moon is due to [removed word] off below the horizon?

[MikeWilson]

And regarding the ST80 focusser - LOL. It's not good. Basically as you focus in and out it twists slightly. Right on the point I was trying to focus the central guide star with just the centre 64x64 pixels of the sensor.

That wasn't fun at all!

[AndyUK]

Hi Mike - Auto lock certainly works well on bright stars - I slewed to capella and centred using the parfocal eyepiece, took it out and replaced it with the synguider (zoom level 1 - star on screen and pressed lock... Job done! That could be very useful.

I must admit, I too am still also using the diagonal as it's simply easier to see...

Guiding on Vega...

RA: 875

DEC: 600

BRI: (about 130ish)

Is this good, chaps?

That's similar to what I'm getting - I suspect your exposure was pretty low though (16ms?), and a previous responder in this thread suggesting halving the RA and DEC values (). My capella lock is at 8ms, (Brightness 50) as I understand that the smaller the star on the screen the better it is at tracking... but of course lowering the exposure mean increasing risk of tracking the seeing (which is actually quite evident on the screen at 8ms). Still... It works... Now back to the finderguider ( may be gone a while!)

[simon84]

Going by my estimate at about 5:30am, ok so that was Stellarium from my location with the time speeded up....lol.

[simon84]

I got shot of my ST80, didnt like it one bit, at £85 new it could have been better, so for not alot more I got the William Optics 66 Petzval which was a brilliant little scope.

I used it for guiding, solar viewing, daytime scoping down at the beach and a bit of imaging.

That cable sounds terrible.....

[AndyUK]

Hi Mike - You just caught me...

And regarding the ST80 focusser - LOL. It's not good. Basically as you focus in and out it twists slightly. Right on the point I was trying to focus the central guide star with just the centre 64x64 pixels of the sensor.

That wasn't fun at all!

JGS01 helped me out with a similar problem on my 100ED - You need some teflon tape to pad out the focuser tube. Alternatively (and I don't know if these exist on the ST80), my ST102 has a grub screw near the tube focus lock - You could try tightening this a tad (but not too much...)

[MikeWilson]

Hi guys,

I'm ok with the issue right now since I have the parfocal eyepiece but I can see how the teflon tape could be useful. There's simply too much 'travel' (i.e. wobble) in there. I will take a look for a grub screw.

Right now I'm having real problems trying to get a guide star amongst the mess of light pollution and moonlight. I'm wondering if it might be worth applying the 1.25" skywatcher light pollution filter that I have to the SynGuider and trying again..

[simon84]

You can but try. You may need to adjust the gain though.

[MikeWilson]

Update - my inability to find a guide star was because I had the exposure set too low. Once I increased it from 32ms to 512ms I had a dozen to choose from. I let the SynGuider pick one for me and it's guiding no issues at all.

So reflecting on the finder/guider issue again I would have thought that I wouldn't be able to guide so easily with a finder/guider - however the finder/guider would mean I'd only need one 10kg counterweight (I am now using two) and I'd be able to adjust where the finder/guider was looking - whereas with my current "fixed in place" ST80, I cannot.

I cannot get my camera to focus (out of laziness, really - I don't want to take multiple pictures and adjust the focuser in-between each one) as the only star I can see on the Live View is Vega and it's just disappeared behind my bamboo tree.

[simon84]

You should be able to use the moon or Jupiter to focus. I find a bright star like Vega also works but not from behind a bamboo tree.

Get your self a marker pen so you can start marking positions on your focuser, I've got an approx mark at 32mm which I know the camera will be very close to being focused, makes the next session much easier.

You shouldnt need to move an 80mm scope anywhere to find a guidestar, there are others that have guided with a scope in a fixed position and have never had to move their scope. I splashed out £125 on guiderings and a second dovetail only to find out I just didnt really need them.

The other advantage of the finder/guider is that you can mount it on the finder shoe on the scope so no exspensive hardware required at all.

[MikeWilson]

Thanks SlySi. I'll give a marker pen a go. I was tempted not to mark things as I like to keep my kit in as pristine a state as possible (should I need to sell it) but I guess I'm bedding in for the long haul so out with the marker pen!

As for focussing, I never thought to focus on Jupiter. Does focus on Jupiter == focus on stars?

Regarding the guider - it seems to be ruining my images.

Attached two images (out of focus) with the guiding turned off and with the guiding turned on. The one with trails is the guided image.

EDIT: Problem resolved. It turns out that the brightness value was too high. I dropped the exposure down to the lowest setting it would go to without dropping below 10. It's currently at around 15-20 and I produced a guided image that looks like the unguided one.

Now to try for three minutes.

[simon84]

Its a long long way away is Jupiter so yes it will work. Try imaging it with your camera with a lens on and have a look at the result. All the stars around it will appear sharp aswell.

Dont go by the infinity marker on the camera lens though, I've never had one thats accurate enough to use by itself. It'll get you close though.

As for the images, couple of things to check, was the synguider calibrating? How was your polar alignment? Did you knock the setup during the image? I'm no expert on imaging and guiding but they would be the first few things I'd check, something might have slipped and caused the error.

Thats another reason why I like PHD, you can watch a live graph and a big error really stands out. Does the Synguider have any kind of log?

[MikeWilson]

Thats another reason why I like PHD, you can watch a live graph and a big error really stands out. Does the Synguider have any kind of log?

PHD may have caught this issue. I had the exposure time much higher than it should have been for this particular star. After locking the guidestar the next step is to reduce the exposure time as low as possible without going lower than the BRI value of "10". I think I've done that now.

EDIT: There is no log that I am aware of. In fact this SynGuider is missing a trick by lacking a USB interface to use as a QHY5 style CCD camera.

[AndyUK]

Although obviously not imaging, with the ST102 only being used as a guider, the guidestars (Caph and then Capella) literally stayed absolutely locked in the centre of the crosshair. I had to reduce the exposure to reduce the size of the stars on the screen (hence 16 and 8ms exposures on such bright stars), but they simply didn't move for 20+ mins. HOWEVER...

With the finderguider on the ED100, all seemed quite hopeful to begin with (using Capella) and I managed to lock and start guiding (BRI 94, exposure 128ms), but the star was much bigger in the screen (to be expected with that exposure) and, bizarrely, although it was initially locked and auto calibrated, after 60s it slipped away from the crosshairs in RA and eventually lost the star. I tried this twice, but got the same result... . At a bit of a loss on this one as I don't understand why if it's locked it shouldn't stay locked - the aggressiveness values were RA 990 and DEC 440...

I suspect that it's something I'm doing wrong (as Peter was able to get it locked), but on the basis of the results with the 102, I think I'm going to have to bite the bullet and get the guiderings after all... which is a shame as I seem to be SO close!

Mike - I use a pencil for marking the focuser tube - It may not be as permanent as a marker pen, but I find it still works (and of course you can wipe it off with a finger later if you need to).

Also for DSLR focusing I invested in a Bahtinov mask - Best bit of plastic I ever bought! Point the scope at a very bright star, switch on live view and zoom in (adjusting framing with the handset as necessary to get it central in the frame). Put the Bahtinov mask over the top of the tube and focus until the diffraction pattern is equalised. Take a quick 5s image and zoom right in to check and jobs a good 'un! I then lock the focuser down and that's it - It's focused!

Sly - No log with the Synguider unfortunately...

[MikeWilson]

Interesting post Andy. Could you try dropping your exposure down to 64ms in order to get your BRI value down to nearer 10? I am finding that guiding with higher BRI values (over 100) seem to produce poor auto correction, however I'm yet to have a star slip away because it it.

Regarding focussing - I think a Bahtinov mask is the way to go. I may get one too. I just did a live view focus on Jupiter's moons (zoomed in twice) and I think I'm pretty close although every time I lock the focuser down the focus goes just ever so slightly out.

Not a big deal though as the images always get resized down later in Photoshop which eliminates the tiny off focus issue.

I am just now attempting to image M45 (Pleiades) and have found a guide star (don't know which one) but the exposure has to be set at 1024ms in order to get a BRI above 10. Quite a difference compared to my random medium-mag star near Cassiopeia that I used for my earlier tests.

Seeing is dreadful though but I think that by the time the moon slips away, Orion will be up. If I can get guiding working tonight then I might even try for a shot at M42. I've never seen M42 before so that will be a real pleasure.

EDIT: 5 minutes on the Pleiades coming right up.

EDIT2: SiSli - focussing on Jupiter worked.

[MikeWilson]

Success.

8 minutes and 41 seconds. I could have kept going longer.

[AndyUK]

Hi Mike - That looks like a result to me...! Congrats...!!!

Thanks for the advice on reducing the exposure further - I'll see if I can have another go later, but I've given up on the guiding for the moment and am just about to have a crack at a moon mosaic. Imaging DSO's with the moon this bright is a bit tricky to say the least...

Good luck with M42 though - I haven't managed it yet as it doesn't become visible (for me) until c. 4:30am (hidden behind garage ), and when it does come up, it's then over the house () and later in the year it then gets obscured by the sodium lights (:()

[MikeWilson]

Hi Mike - That looks like a result to me...! Congrats...!!!

Thanks for the advice on reducing the exposure further - I'll see if I can have another go later, but I've given up on the guiding for the moment and am just about to have a crack at a moon mosaic. Imaging DSO's with the moon this bright is a bit tricky to say the least...

Good luck with M42 though - I haven't managed it yet as it doesn't become visible (for me) until c. 4:30am (hidden behind garage ), and when it does come up, it's then over the house () and later in the year it then gets obscured by the sodium lights (:()

Hi Andy,

Thanks! I wouldn't have done it without your help and encouragement. Well, maybe - but with a heck of a lot more time and late night swearing in the garden!

Since the moon is up I think I might just take a bunch of darks at the new longer exposure times. Or come to think of it, I might just leave the calibration images out for now on the basis that I can take darks even on a cloudy night just by leaving the camera outside taking photos of the inside of the lens cap. That would give me more time to collect data.

M45 is barely visible to my eyes at the moment, although now that I feel I'm >getting somewhere< with the guiding perhaps in the future I'll be able to get some better results when I do get to a darker site.

For sure I can say this - the brightness value needs to be as low as possible without going below 10. My BRI on the M45 guide star (probably not one of the main ones with a 1 second exposure) is hovering around 6-8 right now. I presume if it hits 0 the star is effectively lost and guiding will stop.

The other thing to note is that the calibration needs to be done every single time the target changes or the scope moves. Basically once you are in position, the workflow is this:

1. Set exposure to 512 or 1024 and the noise level to 1. Slowly increase the noise level until you see a star or selection of stars.

2. From the lock menu, select 'auto'. The synguider will find a star in the field of view and lock it. The display will show the position of the star (in x,y coordinates from the central point being 0,0).

3. Select 'guide' and the display will zoom in on the star.

4. Adjust exposure using the + and - keys until the BRI value is as close to 10 as possible without going below it.

5. Select 'AUTO CAL' (or whatever it's called) from within the guide menu.

c. 30 seconds later... you will be guiding.

[MikeWilson]

Guiding... (except I had to add a second counterweight on as one wasn't enough)

EDIT: RA aggressiveness is > 1000 and my BRI value < 10 (hovering between 6 and 8 at the moment). From the camera preview inbetween exposures the shots look pretty darn good but I'll have to wait and see what they're really like (as I haven't connected a USB cable to the DSLR as I wasn't expecting to be doing any imaging tonight with the moon up).

[MikeWilson]

I've published an image of 9 x 5 minute frames of M45 here:

http://stargazerslounge.com/imaging-deep-sky/117507-my-first-guided-image.html#post1563530

I would consider the guiding a success. I've gone all the way up to almost 9 minutes at which time it's the sky glow, and not the star trailing, that kills the image.

[AndyUK]

Hi Mike - That looks pretty damn good to me - 9 mins... Couldn't have done that unguided! The skys the limit from here...

I'm going to see if I can get the finderguider working again... Alnitak appeared briefly before disappearing behind the house, but I reckon it should be up again in an hour or so, so I'll give it a whirl then (but have to say, not very hopeful as even after locking, RA drifts very badly... )

[AndyUK]

Change of plan - Clouds have come in... so packing in. All in all, a pretty good night (but now that I've locked the focus on the finderscope, I reckon I can still maybe get this working with the finderguider....)

[MikeWilson]

Hi Andy,

How is your mount balanced? Do you have say, OTA on the west side and weights (heavier) on the east side?

I think it could be that the guider is deliberately interfering and getting confused by the brightness of the guide star. Lower your exposure and try again - get the BRI figure right down (but not hitting zero ) and I think you'll be pleasantly surprised.