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Tilt adjusting a ZWOASI071-Pro, How do you do it?

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#1 scadvice

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Posted 19 July 2019 - 10:53 PM

I have a new 071 and I've have my own ideas about detecting tilt and how to go about adjusting a tilt out if some night needed to. This camera comes with an adjustment plate built in for those that don't know. I'd like to hear how others determined when first, there is a tilt problem that is related to the camera... and second, their process for readjusting it out?


Edited by scadvice, 20 July 2019 - 12:22 AM.


#2 hoxca

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Posted 20 July 2019 - 07:47 AM

One of idea to adjust the orthogonality of the sensor is to use the following described idea.

The main advantage of this kind of method is to done this kind of adjustment in the calm of cloudynights wink.gif

 

But i never done this with my ASI071.

 

The main reason i did not do it, is that if it's suggested for aligning  astarlight xpress ccd mono camera;

i'm worried to damage the microlenses and bayer matrix of an OSC with the heating power of the laser beam.

I want to avoid dig tiny hole in this precious sensor wink.gif

 

here is the described method :

 

The idea is the reflected beam will be splited by the photosites matrix and projected as a multi dot matrix on the screen.

 

adjust_ortho.png

 

So i diverge from this previous idea, and i was thinking to build a flat panel of multiples artificial star...

This panel could be built from those chineses 100ยต fiber optic designed for star ceiling and positionned at n*focal point to achieve focus with the whole instrument to tune the tilt of the whole system indoor.

 

The alignement of the panel could be done with a laser reflector (mirror) glued on the center of this 1.5 * 1.5 meter panel with multiple artificial stars.

But for now this idea is just pure theory as i did not have the time to complete the project !

 

I'm too busy to construct my argon atmosphere controled glove box for the dessicant maintenance wink.gif

 

For now, i just burn some clear night time and use the sky to do tilt adjustment but an indoor method could be of great help.

Any other idea out there ?


Edited by hoxca, 20 July 2019 - 07:50 AM.


#3 H-Alfa

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Posted 20 July 2019 - 08:22 AM

Hello,

I opened a new thread a few days ago abut this subject also:

https://www.cloudyni...centering-also/

To identify and cuantify it, I use a quite simple method:
1.Center a bright star in the fov
2.Focus it with the aid of a Bathinov mask and the software bahtinov grabber
3.WITHOUT Refocus, move the stars to the corners and check the amount of defocus on each corner (with bahtinov Grabber).

If the defocus on each corner is the same, there's no tilt. Otherwise, you have to adjust the tilter until this 4 corners have the same value (or at least, they are within your CFZ).

You can find a more detailed explanation about this procedure in my website:
https://aiastro.word...ilt-adjustment/

Hope it helps.

Alberto.

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#4 CCDer

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Posted 20 July 2019 - 10:41 AM

Hyperstar has the smallest Critical Focus Zone of them all, about 10um, so tilt has a big impact and it's very apparent once removed. Every time I assemble a "stack" of camera/connectors/spacers/filter wheel/filter drawer (any or all of the listed) for screwing onto Hyperstar, I must get the tilt out of the entire stack.  And with the method I describe below, I see differences in tilt each time I change spacing anywhere in the stack. I've used this method with an ASI1600MC, ASI1600MM, ASI183M, and ASI071 cameras and never need to make any further adjustment for tilt after the camera's mounted. I know this with certainty using CCD Inspector's Real-Time Curvature Map feature to monitor every sub for correct focus. This method should work for any "stack" that can be removed and reattached to any telescope unless that attachment is optically bent in some way with the surface it rests on.

 

All of the camera sensors listed above reflect a regular matrix of dots from a low power red laser pointer source which I have not seen damage an unpowered camera sensor in any way. Surprisingly, this reflected matrix does not move as the camera's sensor is moved laterally for a laser that is mostly perpendicular to the sensor (This sounds like magic but that's what it does.). When the camera's sensor is moved too far latterly, the matrix of dots will disappear but it will not move which makes the adjustments described below possible. This means that if you can set up a laser that is perpendicular to a transparent surface that the entire "stack" can rest on, then the reflected matrix of dots (which has a center dot) can be used to remove all tilt from the "stack" by adjusting the camera's tilt until the center dot of the matrix is reflected back into the laser. 

 

 

Step 1: build a simple laser alignment tool consisting of a laser pointer, or just its head", mounted into the approximate center of about a 14" x 12" board (plywood will do) which has some form of tilt adjusting. To adjust board tilt, I simply used 3 bolts of several inches in length going through the board and into T-nuts on the underside. The laser doesn't need to be perfectly perpendicular to this board since the tilt adjustment from the bolts will do the work. 

 

Step 2: Mount about a 4 inch clear square of 1/4" thick Plexiglas over about a 2 inch diameter hole of a separate 3/4" x 6" wood plank about 3 feet long.  This is the surface the "stack" will rest on. Make sure the Plexiglas does not bend (remains flat for a clean reflection) after mounting.

 

Step 3: Place the board with the laser on the floor. Above it,  secure the plank onto a desktop high surface (screwed or held down with weights). Slide the board along the floor to approximately center the upward pointing laser into the desk mounted plank's hole. Then adjust the floor board's tilt until the laser reflects back into itself off the Plexiglas bottom surface. Since angle of incidence = angle of reflection, this guarantees the laser light that continues out above the Plexiglas top surface is also perpendicular to the Plexiglas top surface. You can now place the camera/connectors (i.e. "stack") on top of the Plexiglass and center it until an array of spots are reflected off the camera sensor back onto the board on the floor. All cameras I've used show these spots, ASI183mm/mc, ASI1600mm/mc, ASI071. Identify the center spot. This will be the spot closest to the laser and is also in alignment of the entire grid of dots. Other spots can appear reflected off the sensor cover glass but can be ignored by checking for their overall grid alignment. The grid's center spot must point back into the laser source to have a zero tilt on the camera sensor.

 

(Only, for cameras without a built in tilt adjustment) If you see tilt (and you will), add the 11mm thick ZWO tilt adjuster into your optics. In the case of Hyperstar, since the tilt adjuster mounts flush onto the camera's body, the adjustment screws must point down (toward the scope) which conflicts with Hyperstar's default filter drawer setup. So a shorter "custom" Hyperstar adapter is required. Space consuming and clumsy for making fine adjustments, I throw away the tilter's large thumb screws, replacing them with low profile flat hex bolts (just the pull screws) and insert thin strips of whatever that works to adjust tilt. 


Edited by CCDer, 20 July 2019 - 10:46 AM.

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#5 H-Alfa

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Posted 20 July 2019 - 11:16 AM

Hyperstar has the smallest Critical Focus Zone of them all, about 10um, so tilt has a big impact and it's very apparent once removed. Every time I assemble a "stack" of camera/connectors/spacers/filter wheel/filter drawer (any or all of the listed) for screwing onto Hyperstar, I must get the tilt out of the entire stack. And with the method I describe below, I see differences in tilt each time I change spacing anywhere in the stack. I've used this method with an ASI1600MC, ASI1600MM, ASI183M, and ASI071 cameras and never need to make any further adjustment for tilt after the camera's mounted. I know this with certainty using CCD Inspector's Real-Time Curvature Map feature to monitor every sub for correct focus. This method should work for any "stack" that can be removed and reattached to any telescope unless that attachment is optically bent in some way with the surface it rests on.

All of the camera sensors listed above reflect a regular matrix of dots from a low power red laser pointer source which I have not seen damage an unpowered camera sensor in any way. Surprisingly, this reflected matrix does not move as the camera's sensor is moved laterally for a laser that is mostly perpendicular to the sensor (This sounds like magic but that's what it does.). When the camera's sensor is moved too far latterly, the matrix of dots will disappear but it will not move which makes the adjustments described below possible. This means that if you can set up a laser that is perpendicular to a transparent surface that the entire "stack" can rest on, then the reflected matrix of dots (which has a center dot) can be used to remove all tilt from the "stack" by adjusting the camera's tilt until the center dot of the matrix is reflected back into the laser.


Step 1: build a simple laser alignment tool consisting of a laser pointer, or just its head", mounted into the approximate center of about a 14" x 12" board (plywood will do) which has some form of tilt adjusting. To adjust board tilt, I simply used 3 bolts of several inches in length going through the board and into T-nuts on the underside. The laser doesn't need to be perfectly perpendicular to this board since the tilt adjustment from the bolts will do the work.

Step 2: Mount about a 4 inch clear square of 1/4" thick Plexiglas over about a 2 inch diameter hole of a separate 3/4" x 6" wood plank about 3 feet long. This is the surface the "stack" will rest on. Make sure the Plexiglas does not bend (remains flat for a clean reflection) after mounting.

Step 3: Place the board with the laser on the floor. Above it, secure the plank onto a desktop high surface (screwed or held down with weights). Slide the board along the floor to approximately center the upward pointing laser into the desk mounted plank's hole. Then adjust the floor board's tilt until the laser reflects back into itself off the Plexiglas bottom surface. Since angle of incidence = angle of reflection, this guarantees the laser light that continues out above the Plexiglas top surface is also perpendicular to the Plexiglas top surface. You can now place the camera/connectors (i.e. "stack") on top of the Plexiglass and center it until an array of spots are reflected off the camera sensor back onto the board on the floor. All cameras I've used show these spots, ASI183mm/mc, ASI1600mm/mc, ASI071. Identify the center spot. This will be the spot closest to the laser and is also in alignment of the entire grid of dots. Other spots can appear reflected off the sensor cover glass but can be ignored by checking for their overall grid alignment. The grid's center spot must point back into the laser source to have a zero tilt on the camera sensor.

(Only, for cameras without a built in tilt adjustment) If you see tilt (and you will), add the 11mm thick ZWO tilt adjuster into your optics. In the case of Hyperstar, since the tilt adjuster mounts flush onto the camera's body, the adjustment screws must point down (toward the scope) which conflicts with Hyperstar's default filter drawer setup. So a shorter "custom" Hyperstar adapter is required. Space consuming and clumsy for making fine adjustments, I throw away the tilter's large thumb screws, replacing them with low profile flat hex bolts (just the pull screws) and insert thin strips of whatever that works to adjust tilt.

Interesting... Do you have any image of this procedure?

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#6 hoxca

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Posted 20 July 2019 - 11:19 AM

Informative CCDer, what kind of red laser are you using for this kind of operation ?

 

for reference:

https://www.cloudyni...s-on-hyperstar/

https://peternagy.sm...ollimation-Rig/

 

For information, i've checked my ASI071 and i can confirm the reflected dot matrix wink.gif

This method is really interesting as it's doable indoor and permit the camera only tilt adjustment.

 

My second proposition with a panel of hundred of artificial stars allow adjustment of the whole optical train also indoor.

I suppose this is only reliable with full threaded setup (to be repetable).


Edited by hoxca, 20 July 2019 - 11:25 AM.


#7 scadvice

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Posted 20 July 2019 - 02:52 PM

Hoxca Yes I've seen that method devised by Starlight Xpress but it is basically for the camera only I'm looking for a tilt as part of the optical train and camera.

 

http://www.sxccd.com...ligning_CCD.pdf

 

H-Alfa your method to check for tilt looks interesting. 

 

All,

 

As a fast check I was wondering if defocusing a centered bright star take an image to reference for any excising coma. then move the scope and image sample each of the four corners(equal distance in each angle) with that defocused star, would it alert you to tilt by the change in the astigmatic like teardrop profile at those points by doing pixel measurement of the long axis. Shouldn't they all be inclined toward the center  pretty much equally?


Edited by scadvice, 20 July 2019 - 04:41 PM.


#8 CCDer

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Posted 20 July 2019 - 03:11 PM

I had pics online via Google drive but deleted them. I think I can find them on older hard drives. I'll make the effort and hopefully post them in a short while, hopefully.



#9 hoxca

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Posted 20 July 2019 - 03:56 PM

CCDer i remember those pics, and i'm sure i show it from an old CN thread.

Don't throw them away, it's always valuable ;)



#10 CCDer

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Posted 20 July 2019 - 03:58 PM

Images showing 2 constructed parts:

 

 

Image of dot pattern reflected by 1600MC sensor (before any alignments). Note two dots at center of grid. Second dot is probably of sensor glass. Paper was placed only to show dot pattern clearly.

 

 

 

After tilt table on floor was adjusted:

 

 

After camera tilt was adjusted:

 

 

 

The extra white plastic covering the Plexiglas is not needed and was only to make rotating the camera in place easier. I eventually removed it to allow any size "stack" to be placed and rotated.

 

Optionally for more precision or easier viewing: one could cover the laser pointer end with a mask with a smaller hole to allow the laser to pass and show reflections with more clarity. But I haven't bothered with it.

 

Any low power laser will do. Many laser elements can be found on EBay at tiny prices. I already had a keychain/flashlight laser which I disassembled and added a switch and battery pack.

 

Also, this was early on when I only adjusted the camera with tilter and a single spacer. Later I realized it was best to adjust the entire "Stack" that screws onto Hyperstar.


Edited by CCDer, 20 July 2019 - 04:01 PM.

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#11 akulapanam

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Posted 20 July 2019 - 04:45 PM

Easiest way is to use @focus3, measure focus in each corner, adjust tilt to ensure each corner focuses at same point. Takes ~30 minutes even with a very fast scope.



#12 ezwheels

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Posted 03 August 2019 - 11:03 AM

CCDer, 

 

Awesome idea and thanks!

 

I copied your design and it seemed to work so far. I haven't had a chance to test it out under the stars, but in the office there was noticeable tilt in each of my ASI camera trains that I was able to correct(071MC pro and 1600MM pro). I use a Gerd Neumann CTU for the 1600 train and the native push pull bolts on the 071. I was able to center the reflected beam for each camera in about 5 minutes. I did notice a few extra center reflected spots that became a little confusing and I think it may have something to do with the quality of the laser I have. I got the laser pointer from ACE as a cat/dog toy for $3. I wish it had a more focussed beam output, so I may try to make a much smaller circular mask for the tip of the pointer. 

 

If this pans out, I would by far consider this the best way to adjust for tilt if it can be used for your imaging train. Best thing is, it is done in the office and during the day or a cloudy night. Super easy to see what needs to be done and very quickly and obviously demonstrates the screws on the adjusters that need to be turned and in which direction.



#13 CCDer

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Posted 03 August 2019 - 09:15 PM

ezwheels,

 

My $3 keychain laser/flashlight was money well spent. But I notice when batteries get low the laser spot becomes oblong and almost worthless so that's always something to check. I to always see an extra dot or two coming off the camera but you have to ignore anything that doesn't line up with the grid lines made by the dot pattern (i.e the dot to put over the laser is the center dot of the grid). I did finally put a 4x4" white plastic mask on the floor board over the laser using a 1/8" hole to allow the laser to pass and some metal tape on the backside of the plastic mask to block all light not going through the hole. This allowed me to discover something else. At least for the ASI 183MM and MC, there's a super fine grid of dots in the shape of an X that appears at the center of the overall dot grid but only when the laser is exactly centered on the sensor. It takes a little work to move the camera around to see this fine grid but it allows even finer adjustment of the tilt because you're centering that fine grid instead of the center dot of the grid. I'd take a pic but its not very bright which is why I hadn't seen it until I put the white mask over the laser source.


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