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Skywatcher Star Adventurer


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Checking back through the thread I see you've checked the polar scope alignment already.  Rotational alignment of the polar scope is pretty easy to check during the day and shouldn't be hard to get fairly accurate, but correct alignment of the reticle relative to the setting circles, or getting Polaris in exactly the correct spot, whichever way you do it, may be more tricky.

Perhaps it would be worth trying drift alignment instead.  Depending on your location you may be able to do that before it even gets "properly" dark.

James

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7 minutes ago, alcol620 said:

thanks Ray for reassurance re trailing rather than spacing, although there looks to be a bit of it too.

Yes you could well be right.  Always hard to fight 2 issues at once, so you are doing the right thing in tackling the tracking issue first.

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Morning folks

More testing last night. Took care on polar alignment and balancing but still have some movement. I am coming to the conclusion that I may have to accept what I have got, although when I zoomed right in on the images so that I could see the actual pixels (I think), this suggests that the actual movement only amounts to a few pixels and perhaps can be ignored? Again all the trails are in the same general direction across the image. (Images taken around Deneb so high in the sky). I have attached a copy of images to illustrate the actual trailing for 30s and 60s images. Am I right in saying the trailing is only a few pixels? I suppose if I was a bit adventurous I could give the mount a bit of maintenance with new grease and adjustment of the gears?

James to mentioned drift alignment, I don't have guiding.

 

 

1406658216_31aug30scentreimagezoomed.JPG.7a670e1758fcf0cd8dfeed445b84dc03.JPG1236402207_31aug60scentreimagezoomed.JPG.dbb91c9329c1cc10920e55aa30edd578.JPG?

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Doesn't look right to me.

Can you post a PNG of the whole image and capture equipment details and I'll see if I've got something similar to compare as 30secs with something like a 50mm lens on a static tripod could look like that.

Do the trails get longer and longer if you do a couple of minutes exposure ?

Dave

Edited by Davey-T
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Drift alignment isn't about guiding.  It's just a different way to ensure that your RA axis is properly aligned with the NCP.  It's perhaps easier to do on mounts that can be controlled by a computer, but it's certainly possible with the Star Adventurer.

James

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Looking at those frames I'm thinking that the trailing doesn't actually appear to be significantly more in the 60s frame than in the 30s frame, which might suggest a mechanical issue rather than an alignment problem.

Anyone else think the same, or am I misreading the images?

James

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18 minutes ago, JamesF said:

Looking at those frames I'm thinking that the trailing doesn't actually appear to be significantly more in the 60s frame than in the 30s frame, which might suggest a mechanical issue rather than an alignment problem.

Anyone else think the same, or am I misreading the images?

James

Yea it doesn't look quite right for trailing. I'd have expected the 60s trail to be double the length of the 30s trail. But it doesn't appear that way.

Does your SA have any wobble to it of you try to shake it? Or backlash?

What tripod is it attached to? How high do you have your tripod?

Have you tried putting your camera settings to the lowest ISO it will go and taking a long exposure to see if the trailing starts and stops/ jumps around?

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Thanks Guys

Answers to a number of the questions raised.

I will post a PNG of the whole image and capture equipment details

Will do longer exposures tonight if possible.

Will have a go at drift alignment, although I think PA is pretty close now.

The SA does have wobble if I give it a good shake, but it seems pretty solid.

Can't feel any backlash.

Tripod at 0.8m and when bought 2nd hand it was said to be a Az3 Alt Az mount. The SA is bolted directly to the centre bolt of the AZ3

Will do a long exposure and post the result.

Thanks again for all your inputs and help.

 

 

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47 minutes ago, alcol620 said:

Thanks Guys

Answers to a number of the questions raised.

I will post a PNG of the whole image and capture equipment details

Will do longer exposures tonight if possible.

Will have a go at drift alignment, although I think PA is pretty close now.

The SA does have wobble if I give it a good shake, but it seems pretty solid.

Can't feel any backlash.

Tripod at 0.8m and when bought 2nd hand it was said to be a Az3 Alt Az mount. The SA is bolted directly to the centre bolt of the AZ3

Will do a long exposure and post the result.

Thanks again for all your inputs and help.

 

 

Attached are 30s and 60s PNG images stretched with Pixinsight. Equipment ASI1600 MC camera and the TSAPO60 scope with reducer flattener focal length 260mm1245961370_testingaugust31stdenebresetpolaralign_2018-08-31_223017_60sec_gain_139_offset_21_Light_frame2.thumb.png.e3d14103654f3261994c6707054e93ba.png

 

 

 

1723968752_testingaugust31stdenebresetpolaralign_2018-08-31_222123_30sec_gain_139_offset_21_Light_frame4.thumb.png.0586f96912ed8e050a6710e18f320a06.png

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Hmmmmm that looks more like you have 2 issues to me, spacing and tilt.  The aberrations to me look variable across the screen, which they wouldn't do if it was tracking.

I'd take a few very short test shots pointing up at the zenith and analyse those first, as I really don't think tracking is your main issue here at this point.

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28 minutes ago, Davey-T said:

Is that a different image as those look OK ?

Zoomed in 800X only maybe a bit of coma.

Dave

SWSA-Star-test-1.png.bc11ceb2bda31299c5cfae23efd64fc2.png

 

The stars on the right hand side of the image are rounder than those towards the left hand side, where the trailing or what ever it is, is greater. They are from the same batch of images.

Ray what would you be looking for with the test shots at the Zenith?

Spacing has always been critical with the ASI1600/ TSAPO60 combo and impossible (in my case to get it perfect) I have run the combination previously on an AZEQ 6 mount and still get some triangulation of stars in the corners.

Does any one know if the 2 brass screws on the TSAPO60 between the focuser and the scope tube can be used to adjust tilt?

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4 minutes ago, alcol620 said:

Ray what would you be looking for with the test shots at the Zenith?

This helps to eliminate draw tube sag and points towards other issues like mating surface not true or sensor misalignment.  Just make sure you are pointing up as close as possible to vertical, and take a few shots around this area.

Not sure if yours is similar to my TS80, but if so it isn't adjustable.

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I've had similar problems with my WO ZS71 which I seem to have resolved by sitting the scope on the dew sheild and loosening the nylon screws that allow the focuser to rotate then using gravity to make the focuser sit straight gradually tighten the nylon screws until tight (a bit each time going round in a circle) may be worth a try if you have a similar set up on the TS 

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1 hour ago, knobby said:

I've had similar problems with my WO ZS71 which I seem to have resolved by sitting the scope on the dew sheild and loosening the nylon screws that allow the focuser to rotate then using gravity to make the focuser sit straight gradually tighten the nylon screws until tight (a bit each time going round in a circle) may be worth a try if you have a similar set up on the TS 

Thanks knobby, did what you suggested, time will tell if it helps

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A laser collimator can be handy for checking everything is true.  I recall John posting about using one in his 150ED thread.  I think he may also have explained exactly what he did should you feel the need to go that far.

James

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Had the scope pointing at the Zenith, but still getting odd shaped stars. Took great care with PA and made slight adjustments to the spacers to get the required 70mm spacing including the camera's 6.5mm back focus. Hope to load up some images late tomorrow to illustrate the star shapes.

I assume I get reasonable polar alignment by the following:

Get Polaris in the redicle and make sure I can run it vertically up and down the vertical axis. Then I move the alt and az screws to get Polaris in the position on the reticle circle that represents the Hour Angle of Polaris?

There must be something I am doing wrong?

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5 minutes ago, alcol620 said:

Then I move the alt and az screws to get Polaris in the position on the reticle circle that represents the Hour Angle of Polaris?

That's about it.  You can also then rotate your mount through 360 degrees and Polaris should stay on the line all the way round.

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Latest instalment from last night - doesn't look to good.

Pointed the scope at the Zenith to try to take out any horizontal flexing of the optic train. PA as accurate as I am capable, balanced similarly.

Results attached for 30s, 120s 300s and 600s following a quick stretch in Pixinsight. Included a screen grab of the stretched histogram with a double hump, is this strange? Any further suggestions would be welcome. Thanks Alec

 

 

465917964_30stestingsept1stzenithcheckforstarshapes_2018-09-01_210904_30sec_gain_200_offset_50_Light_frame5.thumb.png.ee98cff9c10a2392a2fa5940851567cd.png79341160_skywatcheradvimagehisto.thumb.JPG.0ebdd254f5df70b1801f7467e538f11b.JPG

1373646653_300stestingsept1stzenithcheckforstarshapes_2018-09-01_213417_300sec_gain_75_offset_15_Light_frame3.thumb.png.aec2f8bd2fafb3603f7d3b899ba069d2.png288231558_120stestingsept1stzenithcheckforstarshapes_2018-09-01_211448_120sec_gain_139_offset_21_Light_frame3.thumb.png.481bcc6ee43ed590415de9193a0b482d.png1985204371_600stestingsept1stzenithcheckforstarshapes_2018-09-01_215929_600sec_gain_20_offset_10_Light_frame3.thumb.png.c4770cde8941f16bfec57fd724a0afad.png

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The thing that is so odd is that the longer subs are not hugely different to the shorter ones, which pretty well eliminates tracking.  Have a little look at Louise's @Thalestris24 thread posted here where she has a really good video showing quite bad backlash, possibly caused by loose gear retention grub screws or similar.  Maybe try running it out of balance slightly to make sure the gears are engaged only on the driving side which will eliminate potential rocking in the gears.

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2 hours ago, RayD said:

The thing that is so odd is that the longer subs are not hugely different to the shorter ones, which pretty well eliminates tracking.  Have a little look at Louise's @Thalestris24 thread posted here where she has a really good video showing quite bad backlash, possibly caused by loose gear retention grub screws or similar.  Maybe try running it out of balance slightly to make sure the gears are engaged only on the driving side which will eliminate potential rocking in the gears.

Thanks for the mention! Further down in the above thread I posted images of how to disassemble the SA in order to get at the motor gears in order to adjust the backlash :). It would have been a great help if SW had included a 'porthole' that would have allowed access to the second motor screw thus facilitating motor adjustment without having to undo everything. I'm tempted to drill a hole in the body that would do the job! My SA is out of warranty so no worries on that score :) Oh, worm drive adjustment is 'easy' since it's just the silver hex bolt visible on the time lapse switch side after removing the bottom cover. 

Louise

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