star adventurer Star Adventurer calibration?

[stevebeukema]

Hi all,

First post here, and I'm pretty new to AP, just picked up a Star Adventurer mount a couple months ago and have been happily playing around with it with DSLR and various lenses and a 72mm Sky-Watcher refractor.  I'm new to the whole setup process, and I'm trying to do a decent job of leveling the tripod/mount, polar alignment, and I should probably think more about balancing the weight of things.  I've gotten some decent shots, like 60-120 second subs with up to 300mm lens.  My last time out I was getting star trails at 200mm and 15 second exposures, which could have been just a sloppy polar alignment, but today out of curiosity I looked through the polar scope and rotated the RA axis 360 degrees, and I saw that the target circle jumped a few times.  I'm guessing that the target circle should appear not to move while the numbers 3, 6, 9, 12 would rotate around as I rotate the RA axis.  So my guess is that the polar scope would need to be calibrated?

[PaulB]

If you get the "Polar Align" app you will see a diagram for the SA.

It has reticules for all the major eq mounts including ours. I use it all the time to precisely align my mount. See if that works before making adjustments.

[Adreneline]

6 hours ago, stevebeukema said:

I saw that the target circle jumped a few times

Hi. I don't have an SA but I do have an NEQ6Pro and I generally start an imaging session by placing the pole star at the crosshair interesection in the polarscope. I then rotate the RA axis and check it stays in the centre so I am reassured the polarscope is aligned correctly with the mount. I've never seen the phenomena you are describing. (The main reason I centre the pole star is to make sure it is also centred in my imaging scope/camera lens and everything is pointing in the same direction - one of the many disadvantages of having to set-up/strip-down for every imaging session!). Once I'm happy everything is aligned I then use an iPhone app to position the pole star in the correct position on the setting circle.

An SA expert is bound to pop up soon but I would suggest something is a little amiss with the mount  .  I'm pretty sure the target circle should not jump around.

Adrian

[Mr niall]

Yes that sounds right - if you set up during the day on a distant object like a telegraph pole or chimney or pylon or something as a guide. Level the cross hairs in a target then slowly spin the reticule through 180 degrees - if it’s not bang on target then it needs adjusting fractionally. There’s a few good YouTube videos but the star Adventurer manual explains it pretty well actually.

the best piece of advice I can give is to use the optional counterweight shaft and arm - purely because it has a hole in the middle that allows you to recheck your alignment after you’ve added your equipment - mine had a tendency to “sag” slightly after I’d put my camera on. 

But don’t be disheartened- what you’re achieving already is pretty good without guiding.

[SteveNickolls]

Hi Steve,

Thanks for posting. As Adreneline mentions you will need to check the Star Adventurer (SA) reticule cross hair remains central while you rotate the RA axis, all this is explained in the manual. I found mine was fine out of the box. You may also be experiencing movement from your tripod set up. I first tried a heavy duty photographic tripod but it had some spring in use so now use an old Celestron Alt-Az mount with a 3kg house brick in the eyepiece tray to improve rigidity. Never got on with the wedge, very coarse and jumpy in operation. I'd have thought you should get more lengthy exposures from a 300mm lens, the maximum I've obtained has been three minutes. I find if you complete the polar alignment routine on either a division on the polar reticule, i.e. 0, 10, 20, 30, 40 or 50 minutes (or the half way point in between) improves the alignment. One of these-https://www.darkframeoptics.com/product/polarite-right-angled-polarscope which has a magnify capability allows the reticule to fill almost the entire view and so aid accuracy.

Many people experience some 'adjustment' of the polar alignment when loosening or tightening the clutch or tightening a ball head knob but as you gain experience you can do these tasks in the dark without affecting the polar alignment. There is a well known issue with the clutch seizing up and SkyWatcher have produced this helpful video in case it ever happens-

The SA is a cracking mount and I hope you get lots of enjoyment and good images from it.

Best Regards,
Steve

[Davey-T]

7 hours ago, stevebeukema said:

I saw that the target circle jumped a few times.

Hi Steve and welcome to SGL, lots of SWSA users here.

Did you buy the mount new ? as someone may have tried to adjust it previously.

The problem is if you try to use Polaris to align the reticle and loosen all the screws at the same time the reticle can fall backwards out of the screws it then needs disassembling to fix it.

I fitted an O ring behind mine to keep it held forward when adjusting.

Dave

[stevebeukema]

Thanks for all your responses!  I bought the SA brand new a couple months ago, and overall it's been great.  I haven't tried any calibration of the polar scope yet, but I rotated the RA axis a bunch of times yesterday and I noticed that during part of the rotation it moves smoothly, and during another part of the rotation it's a little harder to rotate, and it's consistently at the same spot in the rotation.  I also saw the target scope in the polar finder "jump" a few times as I rotated the RA axis.  I shot a brief video (link below) showing the jumping phenomenon during a 180 degree rotation.  The video was shot with a small refractor and a counterweight and pretty well balanced.   Hopefully calibration will clear this up.

https://www.youtube.com/watch?v=N9Pa9-Wq7xA

[Davey-T]

Check that the three little grub screws are tweaked up.

Dave

[stevebeukema]

Thanks for your responses, everyone, my problem is solved!  Actually, I Googled around, checked forums, and even emailed Sky-Watcher, and I couldn't find anything about my specific problem, and Sky-Watcher said they had never seen this phenomenon before.  The impressive thing about Sky-Watcher, is that a real person responded to my email within 5 minutes of me sending it!

Ok, so here's what I did.  I unscrewed the eyepiece of the polar scope, observed the 3 alignment screws, which seemed to be tight, and then I rotated the RA axis, and I saw a piece inside the polar scope move.  There appears to be another piece/lens thingy connected (is this the reticule?) and it appears to screw in, and it wasn't tightly connected.  I took an alan wrench and put it in a notch (that you can see at around the 12:00 position in the photo), and tightened it.  I put everything back together, and now there is no longer a "jumping" motion when I rotate the RA.  I still need to calibrate the polar scope, but at least I'll be able to do it without the reticule jumping when I rotate it.

[Davey-T]

It doesn't screw in it's just held by the three grub screws, beware if you aim at Polaris to calibrate it as it can fall back and become loose again when you loosen the screws, I fitted an O ring behind the reticle, this stops it falling out of position and makes aligning it much easier.

Dave

[stevebeukema]

I’ll certainly keep an eye on it.  Sky-Watcher called it a retaining ring, and the support guy said he’s never heard of one coming loose before.

[SteveNickolls]

Pleased the issue has been resolved for you.

Best regards,
Steve

[Mr niall]

Hang on... you got an email response from Sky-Watcher????? I have honestly never heard of that happening to anyone ever, and I mean ever ever.

glad it’s sorted though.