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WO Field Flattener

astrophotography
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#1 Drumgar

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Posted 02 April 2020 - 01:52 AM

Hi folks

i am looking for some advice.

I have a WO GT81 and it's dedicated Field Flattener. To this I attach my ZWO ASI 071.

The problem is when I fit the camera to the Field Flattener it is squeaking when I screw it on. It also appears to be scraping the threading and I end up with a lot of dust on the sensor.

My question is this can I put some lubricant on the thread of the Field Flattener and if so what would should I use?



#2 sg6

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Posted 02 April 2020 - 04:13 AM

Well I would lubricate the threads.

What with is the question. Also do it lightly.

 

I guess the attachment is a steel ring to the Aluminium of the flattener, and as the materials are different there may be preferential lubricants for different mating materials.

 

I wonder if an oil wiped over the threads by a cloth or tissue would be better. However oil is a liquid and so likely classed as volatile.

 

Old method was copper grease, these days it seems to be graphite grease. Copper not sure why but the graphite makes sense as graphite is a lubricant itself between surfaces, so even if the carrier grease goes the graphite remains.

 

The unknown being are either acceptable.

 

You will get lots of answers. The ones against will be the grease/oil volatiles evaporating on to the lens surface. So expect Yes and No. The point to consider is: Is the use of a strap wrench more or less hazardous then some lubricant.

 

Really need someone from the high end mechanical engineering side, and not the astronomy side. Too many opinions in astronomy. Any universities around you with a good mechanical Engineering section?

 

Add a location, someone may know of a good place to approach and ask via email.

 

Flat81's are rare.


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#3 drd715

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Posted 02 April 2020 - 08:51 AM

Sounds like you need to debur/polish the threading. Run the treads together with a fine polishing compound. Repeat until it turns smoothly. Make sure to keep all compounds and oils off of the optics. Final extreamly light lube with moly coat lite. Remove all excess lube.

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#4 Cfreerksen

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Posted 02 April 2020 - 09:02 AM

Go to the auto parts place and get a small packet of anti-seize. There is a type that has aluminum flake in it. It is sold for spark plugs. Use a very tiny amount.

 

Chris


Edited by Cfreerksen, 02 April 2020 - 09:08 AM.

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#5 drd715

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Posted 02 April 2020 - 09:02 AM

PS; i doubt that the zwo camera threads are the problem. Check the field flattener extension to make sure it is spected with the proper thread pitch to match the camera. There could be a mismatch in the thread size/ pitch. Between the field flattener and camera should be the spacer to match the specified distance between flattener and camera. Make sure the spacer is the correct length and thread. Sometimes multiple spacers are stacked. The problem of fit is most likely on the spacer side. Spacers are cheap. You don't want to damage the camera face threads.

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#6 drd715

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Posted 02 April 2020 - 09:06 AM

If you are polishing the spacer you might want to use a mating spacer instead of the camera flange - spacers are cheaper than cameras.

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#7 Pauls72

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Posted 02 April 2020 - 09:27 AM

A small amount of a dry lubricant like Silicon Spray or Graphite would be OK. Spray it or put it on a rag and wipe it on.


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#8 Hypoxic

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Posted 02 April 2020 - 09:41 AM

Go to the auto parts place and get a small packet of anti-seize. There is a type that has aluminum flake in it. It is sold for spark plugs. Use a very tiny amount.

 

Chris

I would not use this around lenses and sensors. Anti-seize grease is notorious for smearing and getting on everything if its in a high-touch location; very abrasive as well.


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#9 Drumgar

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Posted 02 April 2020 - 05:00 PM

Thanks everyone I will consider the suggestions



#10 OldManSky

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Posted 02 April 2020 - 08:18 PM

The rear of the field flattener has M48 threads -- what adapter are you using between the front of your ASI 071 and the rear of the flattener?  



#11 nimitz69

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Posted 02 April 2020 - 09:20 PM

I have the WO81GT with flat 6AII and my ZWO camera came with spacers that had M48 threads.  Definitely check as it does sound like a thread mismatch. 




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