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Old 13-12-2016, 12:51 PM
AstroApprentice (Jason)
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Zwo oag

ZWO OAG is now available:
https://astronomy-imaging-camera.com...ories/zwo-oag/
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Old 27-12-2016, 01:33 AM
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g__day (Matthew)
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It's a neat little OAG - having purchased one two days ago then spent two nights before getting it all to work with two ZWO cameras and a ZWO filter wheel (having come from a base with a lot of experience in OAGs). Lucky I had spare spacers of the right diameter and threading because they where needed and not all sold with the unit (which the otherwise skilled dealer assembled incorrectly)!

The first big problem I see in that link is the last picture on the page is misleading to folk who are inexperienced or will be adding more components to their imaging train. The parfocal distance is checking the distance from the pickoff prism to your guider's imaging chip at the tip of the prism is the same as the distance from the tip of the prism your main imaging chip! The red lines they have drawn shouldn't go from the centre of the tube - think about it - the prism would be so far down it would block the main imaging tube! However technically this is right if the vertex of that right angle meant the apex of the prism when fully inserted would be at the exact midpoint of the imaging tube. Better diargrams would help alot.

Also look very closely at the second last picture - the (semi) adjustable position of the OAG - clockwise or counter clockwise (not in or out) of the pick off prism to the imaging chip - it's not orthogonal (at right angles to the X or Y axis of the imaging chip) if you are unlucky! There are three black prongs that protude from an adapter that screws into your imaging camera. These prongs are held by three equally spaced bolts around the perimeter of the OAG. However the machining of where the thread starts may unfortunately restrict you from placing the guide camera at the orientation to the imaging camera that you desire - especially if you have a filter wheel on one end and the imager can only be place orthongonally if its next to the filter wheel - but its too larger diameter to fit that close!

You need some spacers - even thin black cotton thread - about 5 - 12 loops can work to give you perfect spacing - but what a dum kludge - they should have thought thru the machining a bit better. Luckily for me when I relalised I need not one, or two but three spacers to get all their gear to mate corrrectly (no warnings on that) it left the three prongs in exactly the position I needed for the guide camera - pure blind luck or whatever - glad it worked for me - but should have been planned that way - and documented from the start!

The better focus this in the day time comment on their website - great - unless you are using heavy astronomy telescope's in an astro lab - like buyers of this may find themselves in the position! When I posted about a problem on their facebook page that single dumb remark was the only help they offered. Their Australian dealer I used didn't know how to correctly mate the filter wheel to the main imaging camera then add in the OAG - the resulting focal positioning was so bad when the prime was in focus the focus was so bad in the imaging chip - it didn't even give me doughnuts - it just gave me really wierd, totally bloated stars even on super fast images. That took a day of research and guessing just to see what was going wrong.

Next issue with the OAG - the guide camera - a ZWO 120MM-S - wobbled horribly when I placed it in the OAG and tightened the locking nut. Fit was snug but I showed their dealer in the store - wobble was horrible in a brand new unit! Turns out there is the easiest of (undocumented) fixes. The prism arm has a locking bolt that is obivious and shown clearly on their screen shots. What is not shown is just slightly below this locking bolt is a tiny Allen bolt. Tighten this 1/2 a turn or so then the prism still slides smoothly when you loosen the locking bolt, but once you lock it their is no wobble whatsoever in the guide camera!

Jason, et al, - I think this is quite a nice unit - but the assembly and user documentation is very poor. The unit needed essential, cryptic, small adjustments out of the box. The dealer needs training on how to service, sell and fit ZWO components to this unit, and probably across the ZWO range. Also they should be able to say when you mate specific components of their range together - this is the mating sequence, this is how many spacers you need - and sell these spacers at time of purchase. Better yet have one large spacer instead of three odd length ones to make up the required length!

Once you are past all this (if you didn't simply return all the gear as faulty, undocumented, dealer unskilled in correct assembly, dealer not knowing what parts to sell to mate it to motor focuser they previously sold me, unit components not properly tightened on sale - some too lose, some way too tight)... it is actually a great unit.

But the simply avoidable pain I hate to go through to make it all work!

Refer you to this thread describing all the effort and discover to get all this brand new, expensive gear to function correctly http://www.iceinspace.com.au/forum/s...d.php?t=151636

Last edited by g__day; 27-12-2016 at 01:46 AM.
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Old 27-12-2016, 11:37 AM
AstroApprentice (Jason)
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Hi Matt, Thanks for sharing the OAG issues. I've ordered one, but not sure if I have the correct spacers. Anyhow, Thanks for the heads up, it looks like your pain is our gain!
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