Strange "double stars" with OAG

[kirkster501]

Hi all,

Following my "half moon" stars thread.

I've noticed a strange "double" star effect when guiding with my OAG.  This is a FSQ85 scope with Moravian OAG, G2-8300 camera and Lodestar X2 all properly balanced on a MESU 200.  So this is a reasonably high specification rig (more so since also have a full compliment of Astrodons too.)

There is the main body of the guide star as expected.  However, there is another version of the star either above or below the main star. This "second star" sometimes disappears.  It's really weird.  Sometimes the "second" star comes in above, then fades out and appears below the main star.  It appears on all stars so that rules out  genuine double stars.  However, the images on the main G2-8300 are absolutely fine and focused perfectly without this doubling, so this is something to do with the OAG or Lodestar.  My TEC scope (double mounted side by side on my rig) guides perfectly without this "double star" effect. The guiding graph looks rather poor and since I am within 8 minutes of PA of the pole and with a MESU mount, I'd expect it to be a bit flatter.  I think PHD is trying to lock on to this transient "star" sometimes and it then wrecks the guiding.  It is mill-pond flat with my TEC scope with its Atik OAG.  I am focused properly.  Bare in mind the  "half moon" stars I discussed on my other thread.

Any thoughts guys please?  I plan on swapping the guidecam to see if that is causing this effect.

Pics as below.

Thanks for looking.

Steve

[Zakalwe]

Is the pick-off prism silvered or clear? it might be an internal reflection in the prism. Perhaps blackening the rear of the prism would help?

[kirkster501]

Thanks, I will check into that.  Another theory is that I have done much of my tinkering in rubbish skies.  Last night was a quite misty and murky and not an AP night at all and I was playing with the OAG, hence this issue.  Could the fading in and out of the "double" star be atmospheric in some strange way?  I need a clear, reasonable night to test this.

[kirkster501]

Guys, what ascom driver do you use for your lodestar x2 and which guider do you select from th3 drop down in PHD2 please?

[ollypenrice]

On 1/30/2018 at 18:51, kirkster501 said:

Thanks, I will check into that.  Another theory is that I have done much of my tinkering in rubbish skies.  Last night was a quite misty and murky and not an AP night at all and I was playing with the OAG, hence this issue.  Could the fading in and out of the "double" star be atmospheric in some strange way?  I need a clear, reasonable night to test this.

I doubt it, personally. You have two crisp stellar images in the screen grab you posted. Murky nights produce soft fuzzy stars, not pairs of crisp doubles, and faint ones tend just to disappear. This is certainly a new one on me. Is the turret of your OAG absolutely rigid? It couldn't have the ability to rock slightly? We had this once with an older model SX OAG and I made a steel strap to stop it.

The thing is that whatever is happening in your setup is happening quickly because both the real and the spurious stellar images are sharp.

Can we completely rule out hot pixels? Are you subtracting a dark as you guide in PHD2?

Olly

[sloz1664]

2 hours ago, kirkster501 said:

Guys, what ascom driver do you use for your lodestar x2 and which guider do you select from th3 drop down in PHD2 please?

Hi Steve,

I use this one:-

Steve

[Whirlwind]

Have you definitely ruled out a guiding issue by seeing if the same thing happens when the lodestar is observing but not sending guiding corrections.  You explanation appears cyclical which I would not expect to arise from a shift of the lodestar - I would have thought that would have been more 'jumpy' as the stress overcomes the resistance.  A cyclical effect would imply a cyclical cause which would indicate a gear related issue?  What is you guiding exposure and mount correction rate?

[kirkster501]

Thanks guys. Could someone send me a acreenshot of the ascom driver you are using please?

[Davey-T]

Have you checked the prism, my Atik OAG prism came lose and actually fell out, only held in place with a nylon screw.

Dave

[kirkster501]

7 hours ago, Davey-T said:

Have you checked the prism, my Atik OAG prism came lose and actually fell out, only held in place with a nylon screw.

Dave

Yes Dave, appears to be but i will recheck it.   Will look into painting it black on the back though as per Zakalwe's suggestion.

Edited February 2, 2018 by kirkster501

[kirkster501]

Tearing my hair out with this problem, same tonight and wasting multiple precious clear nights.  It is a silvered mirror on the OAG and the thing is mounted as solid as a rock.  I just cannot think what could possibly cause such a problem, but a problem there is....  The guiding is all over the pace because PHD just not see a circular star, it sees both the main star and the mirror of it that seems to fade in and out, so the "centroid" is a oblong and PHD cannot be sure what it is guiding on.  All my drivers are the recent ones etc.

Going to try a different guide cam, back to the trusty QHY5 that has worked perfectly for years.

[kirkster501]

I got to the bottom of this.  It is something to do with the interlacing of the CCD chip and the driver software.  I regressed the driver back to 5.5.1, made sure binning was set to 2x2 and it all seems to be OK after a brief play about last night in terrible seeing.  Will need a proper clear night to thoroughly test but I think I am there at last.

Many thanks to @gnomus Steve, for his suggestions on this.  This was a very tricky problem to get to the bottom of.  I still owe him the bottle of gin when I next see him for helping me with my mount

FWIW, I am not sure the huge investment in the Lodestar X2 is such an improvement over the venerable QHY5 that has proved utterly faultless and bulletproof at a quarter of the cost.

[Jkulin]

I know you have fixed this but FWIW I'm using this with my Lodestar X2: -

I'm using the Starlight Driver 12.30.10.402 dated 27.08.15

Driver file name sxAscomInstaller-v6.2.1.17140.exe

Hope that helps?

[kirkster501]

This is the ASCOM driver I am using as advised to me by Steve.  I kept getting the "double guide stars" on my rig with the newer driver.  I have no idea why.  The binning must be 2x2 as well.

 

 

[Jkulin]

Where are you launching that SXCamera Setup app from as I can't find that on my system?

[kirkster501]

Ou get to it from the connect screen in PHD2.  Click the spanner thing and it takes you to the setup screen.  Note, sometimes this gets hidden behind other windows....

[Martin Meredith]

This is an old topic but it appears to crop up occasionally, and having run into it myself during some code development which involved reading the data off the SX ASCOM driver, I am almost certain that this is due to a problem with the SX ASCOM driver emitting the odd and even rows in the wrong order with no option provided to swap them. 

If I swap the rows in software the image is perfect; if I don't, I get the double stars. Binning 2x2 'solves' it, but only by default because the order of the rows is rendered irrelevant by binning with an even number. This solution doesn't help anyone who wishes to preserve resolution (as I do).

I leave this here in case it helps anyone (although the only solution at present is to bin, or to use a different driver).

I've contacted the driver developer to check if this really is the case. Meanwhile, for anyone using the SX ASCOM driver with the Lodestar I'd be interested in seeing your unbinned images to see how widespread an issue it is. It may be that some software knows about the issue and provides a 'silent' fix.

This is the kind of thing you see. Left is corrected, right is swapped odd/even rows. Top is stellar, lower is a capture of a straight edge. The effect is quite substantial.

Martin 

 

[Stuart1971]

On 30/01/2018 at 17:20, kirkster501 said:

Hi all,

Following my "half moon" stars thread.

I've noticed a strange "double" star effect when guiding with my OAG.  This is a FSQ85 scope with Moravian OAG, G2-8300 camera and Lodestar X2 all properly balanced on a MESU 200.  So this is a reasonably high specification rig (more so since also have a full compliment of Astrodons too.)

There is the main body of the guide star as expected.  However, there is another version of the star either above or below the main star. This "second star" sometimes disappears.  It's really weird.  Sometimes the "second" star comes in above, then fades out and appears below the main star.  It appears on all stars so that rules out  genuine double stars.  However, the images on the main G2-8300 are absolutely fine and focused perfectly without this doubling, so this is something to do with the OAG or Lodestar.  My TEC scope (double mounted side by side on my rig) guides perfectly without this "double star" effect. The guiding graph looks rather poor and since I am within 8 minutes of PA of the pole and with a MESU mount, I'd expect it to be a bit flatter.  I think PHD is trying to lock on to this transient "star" sometimes and it then wrecks the guiding.  It is mill-pond flat with my TEC scope with its Atik OAG.  I am focused properly.  Bare in mind the  "half moon" stars I discussed on my other thread.

Any thoughts guys please?  I plan on swapping the guidecam to see if that is causing this effect.

Pics as below.

Thanks for looking.

Steve

Hi,

I just posted a thread about this exact issue, with the X2 lodestar, I know this is an old thread but I solved it today by using the native SX driver in PHD instead of the ASCOM one, and now it’s perfect.

I had exact same star shapes as you the last three times I went out imaging, and was driving me mad, but mine was through a straight guidescope and not an OAG…swapping to native driver solved the lot, see here for before with ASCOM and after with native drivers…and both with same settings too…😮

‘I assume you solved your issue the same way, or was yours something else…

 

Edited January 14, 2022 by Stuart1971

[Stuart1971]

On 24/05/2021 at 21:05, Martin Meredith said:

This is an old topic but it appears to crop up occasionally, and having run into it myself during some code development which involved reading the data off the SX ASCOM driver, I am almost certain that this is due to a problem with the SX ASCOM driver emitting the odd and even rows in the wrong order with no option provided to swap them. 

If I swap the rows in software the image is perfect; if I don't, I get the double stars. Binning 2x2 'solves' it, but only by default because the order of the rows is rendered irrelevant by binning with an even number. This solution doesn't help anyone who wishes to preserve resolution (as I do).

I leave this here in case it helps anyone (although the only solution at present is to bin, or to use a different driver).

I've contacted the driver developer to check if this really is the case. Meanwhile, for anyone using the SX ASCOM driver with the Lodestar I'd be interested in seeing your unbinned images to see how widespread an issue it is. It may be that some software knows about the issue and provides a 'silent' fix.

This is the kind of thing you see. Left is corrected, right is swapped odd/even rows. Top is stellar, lower is a capture of a straight edge. The effect is quite substantial.

Martin 

 

See my post above, just had this exact same issue…so it’s still around, and no one at SX bothered as I have asked….just have to use the native driver and all good….👍🏼

Edited January 14, 2022 by Stuart1971

[Martin Meredith]

Glad that works for you. The developer's (third party, not SX) only response was along the lines of 'it would be surprising if the problem had been in the code all these years' .... then radio silence.... I do wonder how many people are living with this issue unawares. In my case it was obvious as I use the Lodestar for EAA rather than guiding.

Martin

 

 

[Stuart1971]

36 minutes ago, Martin Meredith said:

Glad that works for you. The developer's (third party, not SX) only response was along the lines of 'it would be surprising if the problem had been in the code all these years' .... then radio silence.... I do wonder how many people are living with this issue unawares. In my case it was obvious as I use the Lodestar for EAA rather than guiding.

Martin

 

 

Yes, I got the same response, so I guess we are all wrong, and all is good with the driver….🤔🤔