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AstroZap C-11 Dew Shield and T-Shirts

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#1 phemmert

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Posted 04 December 2020 - 02:45 PM

Hi everyone, I have a C-11 equipped with Hyperstar and an Astrozap dew shield, having fun with t-shirts and a Spike-a-Flat light panel. Does anyone in the crowd use an embroidery/quilting ring that fits over that dew shield to tighten those cloth covers - if so what size? I found out a 12" ring is a tad too small, and the tightening tolerances with these rings aren't huge. Thanks all!



#2 ShaulaB

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Posted 04 December 2020 - 03:10 PM

I share your frustration. The embroidery hoop I bought just doesn't work on my C8. Best of luck finding a work-around.



#3 jgraham

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Posted 04 December 2020 - 03:27 PM

Heh, heh, I bought the largest, cheapest white long sleeve shirt that I could find and drape it over the end of my C11 AZ dew shield. I also wear it as my mosquito shirt in the summer. :)

I have a look large quilting hoop that I've been eyeing, but I haven't tried it yet.

#4 TelescopeGreg

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Posted 04 December 2020 - 06:21 PM

An embroidery hoop is what I use.  I think you're holding it wrong....  smile.gif

 

The hoop consists of an inner ring and an outer ring.  The inner ring is just a ring; the outer one has a thumb screw for tightening it.  The intent is to stretch your fabric around the inner ring, and hold it in place with the outer one.  That makes for a portable taught fabric surface, with a ring around the outside.

 

Just hang the ring over the end of the scope.  As long as the ring is larger than the diameter of the OTA, it will just sit there.  There is no need to have the fabric stretched on the OTA itself, as long as it's stretched on something.  Mine was sized for my 8" Newt, so it's a bit oversized for the 5" refractor I image with now, but it still works just fine.  There's 2 layers of fabric in there (T-shirt front and back).

 

Flat hoop.jpg

 

Flat hoop on scope.jpg



#5 phemmert

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Posted 04 December 2020 - 06:29 PM

An embroidery hoop is what I use.  I think you're holding it wrong....  smile.gif

 

The hoop consists of an inner ring and an outer ring.  The inner ring is just a ring; the outer one has a thumb screw for tightening it.  The intent is to stretch your fabric around the inner ring, and hold it in place with the outer one.  That makes for a portable taught fabric surface, with a ring around the outside.

 

Just hang the ring over the end of the scope.  As long as the ring is larger than the diameter of the OTA, it will just sit there.  There is no need to have the fabric stretched on the OTA itself, as long as it's stretched on something.  Mine was sized for my 8" Newt, so it's a bit oversized for the 5" refractor I image with now, but it still works just fine.  There's 2 layers of fabric in there (T-shirt front and back).

 

attachicon.gifFlat hoop.jpg

 

attachicon.gifFlat hoop on scope.jpg

Thank you, that's excellent information. I thought peeps were using the ring by tightening it around the dew shield itself, with the cloth tucked in between the shield and the hoop. So, any hoop will work as long as it's larger than the shield. The one I got was too small to do as you advise, will get another one asap. I point the scope straight up so that should work just fine. 


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#6 phemmert

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Posted 04 December 2020 - 06:52 PM

An embroidery hoop is what I use.  I think you're holding it wrong....  smile.gif

 

The hoop consists of an inner ring and an outer ring.  The inner ring is just a ring; the outer one has a thumb screw for tightening it.  The intent is to stretch your fabric around the inner ring, and hold it in place with the outer one.  That makes for a portable taught fabric surface, with a ring around the outside.

 

Just hang the ring over the end of the scope.  As long as the ring is larger than the diameter of the OTA, it will just sit there.  There is no need to have the fabric stretched on the OTA itself, as long as it's stretched on something.  Mine was sized for my 8" Newt, so it's a bit oversized for the 5" refractor I image with now, but it still works just fine.  There's 2 layers of fabric in there (T-shirt front and back).

 

attachicon.gifFlat hoop.jpg

 

attachicon.gifFlat hoop on scope.jpg

Are you using a light panel, or sky? I have a panel that will need to rest on top of that too.



#7 TelescopeGreg

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Posted 04 December 2020 - 08:09 PM

Are you using a light panel, or sky? I have a panel that will need to rest on top of that too.

I've mostly used the fabric hoop with either the sky or aimed at the white-ish wall in the garage.  It's not too critical where it's aimed, as long as there aren't any shadows on it.  I'm now experimenting with directly using my laptop screen, balanced on top.  No hoop.  That works fine, too. 

 

I don't think you need to use both unless the panel has some fine grain detail or such that needs to be fuzzed out, or is too bright.  With the laptop screen, I load a medium gray background into LibreOffice (PowerPoint-ish app) Slide Show so I don't blow out the camera, and even so the Flats are taken at well under 1 second exposure.



#8 phemmert

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Posted 04 December 2020 - 08:41 PM

I've mostly used the fabric hoop with either the sky or aimed at the white-ish wall in the garage.  It's not too critical where it's aimed, as long as there aren't any shadows on it.  I'm now experimenting with directly using my laptop screen, balanced on top.  No hoop.  That works fine, too. 

 

I don't think you need to use both unless the panel has some fine grain detail or such that needs to be fuzzed out, or is too bright.  With the laptop screen, I load a medium gray background into LibreOffice (PowerPoint-ish app) Slide Show so I don't blow out the camera, and even so the Flats are taken at well under 1 second exposure.

Yeah, I've got a Hyperstar/C11 with a ZWO 1600mm camera, so getting the brightness down for the LRGB filters is the challenge. Running the Spike-a-Flat at the lowest setting I'm still getting really short exposure times, which should probably be increased if possible, thus the t-shirt gig.




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