ICEINSPACE
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Waning Gibbous 94.4%
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02-06-2022, 06:58 PM
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Registered User
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Join Date: Oct 2011
Location: Albany, Western Australia
Posts: 1,463
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Quote:
Originally Posted by Sunfish
A big impossible 72mm OAG only 20mm thick with at least one dovetail scope side adapter including a short t2 threaded guide camera mount.
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I like it
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03-06-2022, 07:25 PM
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Registered User
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Join Date: Jan 2011
Location: Rylstone, NSW, Australia
Posts: 1,398
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Hi Josh,
I've never seen a device that could correct for an off-centered chip! Tilt, sure, off center, no way!
One way I thought of doing it would be to measure the chip offset, then intentionally offset the threads on both ends of the adapter the same amount, i.e., make them non-concentric. The device would be rotated until it compensated for the chip offset and then locked down with a locking ring.
Would that work?
Cheers,
Peter
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03-06-2022, 08:18 PM
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Registered User
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Join Date: Jan 2009
Location: Adelaide
Posts: 9,944
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How about a counterweight for cameras? That is for cameras with large filter wheels, where the counterweight provides balance the correct balance for the whole imaging system.
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03-06-2022, 08:59 PM
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Registered User
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Join Date: Feb 2006
Location: Sydney
Posts: 17,902
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Quote:
Originally Posted by Joshua Bunn
I like it
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A thinner MMOAG type OAG would be great. Especially if it were able to rotate.
Greg.
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04-06-2022, 01:30 AM
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Registered User
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Join Date: Oct 2011
Location: Albany, Western Australia
Posts: 1,463
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Thanks Guys!
Quote:
Originally Posted by PRejto
Hi Josh,
I've never seen a device that could correct for an off-centered chip! Tilt, sure, off center, no way!
One way I thought of doing it would be to measure the chip offset, then intentionally offset the threads on both ends of the adapter the same amount, i.e., make them non-concentric. The device would be rotated until it compensated for the chip offset and then locked down with a locking ring.
Would that work?
Cheers,
Peter
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Sounds familiar Peter and an interesting idea.
I have my reservations about making the threads non-concentric with each other. This would be quite costly. Also, yes, you could lock it down at the desired location, but this will alter your backfocus. This would most likely need another adapter to then get your backfocus right. I think probably the cheapest and simplest way would be to use a dovetail that has a couple of millimeters of lateral movement, by which the camera can be moved left, right, up and down.
Quote:
Originally Posted by Paul Haese
How about a counterweight for cameras? That is for cameras with large filter wheels, where the counterweight provides balance the correct balance for the whole imaging system.
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I could see a need for that Paul. Something like a "tube ring" to go around an adapter which then has a CW bar threaded into it.
Quote:
Originally Posted by gregbradley
A thinner MMOAG type OAG would be great. Especially if it were able to rotate.
Greg.
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That's a great idea Greg, something that could be built.
Is there a big need to be able to rotate the OAG/guide cam separate to the imaging camera, especially with square chips, as opposed to rotating the guide cam and imaging camera together?
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04-06-2022, 06:56 AM
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Registered User
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Join Date: Jan 2011
Location: Rylstone, NSW, Australia
Posts: 1,398
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"I think probably the cheapest and simplest way would be to use a dovetail that has a couple of millimeters of lateral movement, by which the camera can be moved left, right, up and down."
Yes, you are right Josh, but where would you place such a dovetail in the optical train. To not disturb the back focus it would need to be located somewhere in front of that assembly. The Gemini rotator in my system has a dovetail...perhaps there is some room to play with???
P
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04-06-2022, 10:33 PM
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Registered User
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Join Date: Oct 2011
Location: Albany, Western Australia
Posts: 1,463
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Quote:
Originally Posted by PRejto
"I think probably the cheapest and simplest way would be to use a dovetail that has a couple of millimeters of lateral movement, by which the camera can be moved left, right, up and down."
Yes, you are right Josh, but where would you place such a dovetail in the optical train. To not disturb the back focus it would need to be located somewhere in front of that assembly. The Gemini rotator in my system has a dovetail...perhaps there is some room to play with???
P
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Are you still having off axis issues Peter on rotation?
The only place for such a thing would be right in front of the camera, that is where the issue lies. Putting it infront of a filter wheel or OAG will put them off axis which is a bad idea.
Josh
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05-06-2022, 11:03 AM
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Registered User
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Join Date: Jan 2011
Location: Rylstone, NSW, Australia
Posts: 1,398
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Hi Josh,
Yes, I am. But of course putting it right in front of the camera will totally mess up my flattener distance!
Anyway, I'm just about to get going in my new observatory. Time will tell if I can live with things the way they are.
Peter
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05-06-2022, 11:25 AM
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Registered User
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Join Date: Oct 2011
Location: Albany, Western Australia
Posts: 1,463
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Hi Peter.
Best of luck with your observatory build, that's awesome.
Do you do a closed loop slew after rotation or a meridian flip?
Regards Josh
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06-06-2022, 08:19 AM
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Registered User
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Join Date: Jan 2011
Location: Rylstone, NSW, Australia
Posts: 1,398
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Yes, a CLS does solve pointing. That isn't the problem though annoying.
What it will not solve are differences in star shapes at field edges upon rotation.
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06-06-2022, 10:04 AM
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Galaxy hitchhiking guide
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Join Date: Dec 2007
Location: The Shire
Posts: 8,111
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My wish list would be a thin non-rotating focuser/spacer...AP (2.7") threaded..
Say 8mm-13mm thick (i.e 5mm of travel) . to allow for perfect backfocus adjustment.
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06-06-2022, 11:38 AM
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Registered User
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Join Date: Oct 2011
Location: Albany, Western Australia
Posts: 1,463
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Quote:
Originally Posted by PRejto
Yes, a CLS does solve pointing. That isn't the problem though annoying.
What it will not solve are differences in star shapes at field edges upon rotation.
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Ahh yes, I feel your pain there Peter.
My STL11K has that issue on the cdk12.5 that I use to have, when your imaging circle is just large enough for the sensor size.
Remind me again what connection You have to your camera. For memory, you have lots of backfocus to spare from the adapters I made you, correct?
Quote:
Originally Posted by Peter Ward
My wish list would be a thin non-rotating focuser/spacer...AP (2.7") threaded..
Say 8mm-13mm thick (i.e 5mm of travel) . to allow for perfect backfocus adjustment.
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That's a good one Peter, leave it with me. I Made one of these for PRejto ^ but it was a rotating one, not the easiest to use.
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06-06-2022, 01:07 PM
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Galaxy hitchhiking guide
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Join Date: Dec 2007
Location: The Shire
Posts: 8,111
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Quote:
Originally Posted by Joshua Bunn
That's a good one Peter, leave it with me. I Made one of these for PRejto ^ but it was a rotating one, not the easiest to use.
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Indeed, non-rotating helical would be the tricky (but essential) bit.
If you can create such a beastie, send me a PM...I'd bee happy to fund the project.
P.S. I'm thinking a fine thread, outer focus ring might be the way to go?
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06-06-2022, 02:51 PM
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Registered User
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Join Date: Feb 2006
Location: Sydney
Posts: 17,902
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Quote:
Originally Posted by Peter Ward
My wish list would be a thin non-rotating focuser/spacer...AP (2.7") threaded..
Say 8mm-13mm thick (i.e 5mm of travel) . to allow for perfect backfocus adjustment.
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Yes I would want one of these also.
Greg.
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08-06-2022, 10:26 PM
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Registered User
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Join Date: Sep 2010
Posts: 2,100
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just want to re-iterate the suggestion of a tilt adjuster. Shooting now and I've got some crazy tilt out of nowhere.
Would love a large tilt adjuster with M48 threads, because otherwise I wouldn't be able to access the screws since the filter wheel and flattener bulk out enough to prevent access. Maybe something 100mm in diameter.
Something like this just isn't big enough
https://www.firstlightoptics.com/ada...-adjuster.html
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08-06-2022, 10:29 PM
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Registered User
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Join Date: Oct 2011
Location: Albany, Western Australia
Posts: 1,463
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Quote:
Originally Posted by AdamJL
just want to re-iterate the suggestion of a tilt adjuster. Shooting now and I've got some crazy tilt out of nowhere.
Would love a large tilt adjuster with M48 threads, because otherwise I wouldn't be able to access the screws since the filter wheel and flattener bulk out enough to prevent access. Maybe something 100mm in diameter.
Something like this just isn't big enough
https://www.firstlightoptics.com/ada...-adjuster.html
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Hi Adam,
Absolutely, I am in the process of designing a tilt adapter, that can be adjusted from the edge (not the face) and having an integrated rotator as well. Just a manual one at this stage
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08-06-2022, 10:59 PM
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Registered User
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Join Date: Sep 2010
Posts: 2,100
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Quote:
Originally Posted by Joshua Bunn
Hi Adam,
Absolutely, I am in the process of designing a tilt adapter, that can be adjusted from the edge (not the face) and having an integrated rotator as well. Just a manual one at this stage
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That's awesome to hear, Joshua! Can't wait to see what you come up with.
Also, I really like this idea
https://astrodymium.com/products/rot...tilt-adjusters
I'm imagining something that instead of being three pieces, is one piece with the same rotation concept as the above. You shift one or two pieces in various directions to adjust tilt.
Big benefit, these are as thin as shims, so take up almost nothing from your back-focus.
That said, if yours has a built in rotator, well mate you are onto a winner there.
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08-06-2022, 11:07 PM
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Registered User
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Join Date: Oct 2011
Location: Albany, Western Australia
Posts: 1,463
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That's a pretty simple and elegant solution.
The only issue that may happen there is if you have a particularly heavy image train that could compress the edge of that plastic shim, especially if the torque was perpendicular to a line that goes through the raised section of the shim.
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08-06-2022, 11:23 PM
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Registered User
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Join Date: Sep 2010
Posts: 2,100
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Good point! I've ordered some anyway to test out and use as an interim solution until you've finished your design
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08-06-2022, 11:45 PM
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Registered User
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Join Date: Oct 2011
Location: Albany, Western Australia
Posts: 1,463
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Cool, it'll be interesting to see what you think of them.
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