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Shims/Spacers

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6 replies to this topic

#1 CrookedEyes

CrookedEyes

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Posted 27 October 2020 - 10:21 PM

How is everybody doing? So, I finally got all of my gear and downloaded all of the ASCOM platform/drivers etc for my first imaging rig. Tonight, I was going to put the imaging train together and attach it to the telescope and then work on operational checks with the laptop tomorrow. However, I ran into an issue with the ZWO OAG attaching to my filter wheel. I have the imaging train as close to the 63mm BF that the Sky Watcher FF requires. I am @ 64. I was going to attach the OAG directly to the FF, then after the OAG, 11mm extender, 2mm T2-T2 coupler, ZWO EFW, ASI 1600MM Pro. When trying to get the OAG attached to the EFW side of the imaging train, it ends up crooked (see pic). Other than Delrin shims, does anybody have a creative way to fix this issue? I couldn't find any T2 Delrin shims at first but I finally found some. They were 20 bucks for 15 shims...3 shims for each of 5 thickness. I sprung for the quick ship which was another 20 bucks. 40 bucks for a few Delrin shims. Oh well, Gotta do what ya gotta do. I just need to keep it backed off a small amount so that I can fit the top of the OAG on to hold the guide camera. Thanks for reading my post and thank you in advance for any suggestions. 

Attached Thumbnails

  • RESIZED_FilterWheel_OAG Needs Adjustment_27 October 2020.jpg


#2 PirateMike

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Posted 28 October 2020 - 12:10 AM

I am having the same problem and it appears to me that the only obvious way to correct it is with shims. Not a good solution because it changes the actual back focus distance, as I'm sure you know.

 

ZWO says the the 11mm spacer should go between the EFW and OAG. The reason is that if the OAG is overly close to the imaging chip then it can not be brought into focus. See this...https://astronomy-im...tions-55mm.html

 

I think my solution will be to have the neighborhood machine shop trim down the 11mm, allowing me to shim as required.

 

Maybe that is not a good solution but I'll do it anyways.

 

 

Miguel   8-)

 

 

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Edited by PirateMike, 28 October 2020 - 12:20 AM.


#3 michael8554

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Posted 28 October 2020 - 11:04 AM

If I've understood your problem, the guidescope is rotated about 80 degrees compared to the flat bottom of the EFW housing ?

 

If the OAG is like many others, if you remove the 3 equally spaced knurled screws, the prism assembly housing can be removed and relocated to be at the top of the EFW, there being some radial adjustment available between the 3 lugs in that assembly.

 

I also cut shims from plastic drinks bottles and the bottom of ally drinks cans and combine to get the right rotational position on screwed equipment


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#4 CrookedEyes

CrookedEyes

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Posted 28 October 2020 - 08:02 PM

michael8554, I haven't gotten back to putting it all together this evening....yet. I have some things to do for work right quick before I get back on it. However, I pulled the OAG out and it looks like your suggestion will absolutely work. I am really frustrated with myself that I didn't even think about this being a possibility. At any rate. Thank you very much for your response! These forums are fantastic. People's generosity and willingness to help new imagers like myself is awesome. Thanks again for your suggestion. Once I get to fiddling with the equipment, I will let you know if it works for sure! Thank you!

 

PirateMike, if, for whatever reason, I am unable to rotate it as michael suggested, I too think shims are the only bet. However, trimming the 11mm extension down by a couple mm is also an intriguing idea! Thank you for the response and your suggestions!


Edited by CrookedEyes, 28 October 2020 - 08:09 PM.

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#5 PirateMike

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Posted 28 October 2020 - 11:26 PM

Hello CrookedEyes,

 

It seems that I didn't fully understand your question, so yes, loosen the three screws, turn the OAG body and it will come off the attachment piece. Then put it back together so the orientation is better, just like michael8554 says.

 

 

I did have to shim the camera a little so that the long side of the chip was perpendicular with the prism insert, other wise the prism can easily get in the way if the chip.

 

 

Good luck, OAG's can be an adventure... or so reality has so far proven.

 

 

Miguel   8-)

 

 

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#6 CrookedEyes

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Posted 29 October 2020 - 01:53 AM

Man, as I was looking back on all of the research I had been doing, I remember reading something or watching a video about the three "toothed" insert. Matter of fact, I had the whole OAG, for the most part, in pieces. So, I apologize for wasting everybody's time. But I definitely want to thank you all for your responses. I think I am just expecting something to go wrong. At any rate, it's good. I will have to shim the camera to orient it a little better and include the shim size in my back focus calculation, or rotate the OAG a little bit to get better orientation of the sensor to the prism. But, I am excited that it is moving along.

Attached Thumbnails

  • RESIZED_ImagingTrain.jpg

Edited by CrookedEyes, 29 October 2020 - 01:54 AM.


#7 PirateMike

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Posted 29 October 2020 - 04:42 AM

Our pleasure. waytogo.gif

 

 

Miguel   8-)

 

 

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