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Walking on the Moon

Chip tilt test jig.


ollypenrice
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20 minutes ago, symmetal said:

The sensors are manufactured with high precision so the cover slip would be parallel to the sensor array, so whether you choose the cover slip or a close pixel dot, both should not move when the tilt has been corrected and the camera is rotated. To see the close pixel dot clearly you would need likely need a larger laser angle which may not be possible if you have a filter wheel and separate tilt adjuster on the jig.

If the cover slip and AR coating are parallel and you have tilt then the bright dot which describes the largest circle when rotated would be the cover slip as the light path has travelled a greater distance. As you don't know if they're parallel that doesn't really help.

Alan

Ah, ok

In this video the top dot, I assume 🤔 is from the Cover glass, and the bottom is from the AR window…if so why does the AR dot move in a much wider circle, should they not move the same, or does this mean that the AR window is much more tilted than the sensor…😮

there is deffo a bit of flaring on the bottom dot, if you zoom in…so does this mean it is from the AR window…🤔🤔

The black dots are from me plotting the movement, as at the time I thought the bottom one was the one I should be watching, but since changed my mind…but I could still be wrong…😂

Edited by Stuart1971
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If all the surfaces giving reflection dots are parallel to each other then the dot on the paper furthest from the laser would be from the reflective surface which is furthest away from the laser, which would be the cover slip (also the pixel beneath it which is likely obscured by the cover slip dot). This possibly explains why the middle dot is 'cleaner' as its just reflected off the AR glass. The dot reflected from the cover slip has to pass through the AR glass twice, so encounters 4 extra surfaces which would likely increase the flaring from the cover slip reflection dot.

On the other hand, if all the surfaces were parallel then all the dots would move as one unit together and each describe the same diameter circle and it wouldn't matter which one you chose to chose as a reference, as when you correct the tilt on that dot all the other dots also will be corrected. 😃

If the surfaces aren't all parallel, then the dots don't all move together as one unit when you rotate the camera. Yours don't, which means the reflective surfaces aren't all parallel, so you have to make an initial guess as to which is the right dot, but as mentioned above it's likely not the 'cleanest' one. 🙂

Alan

 

Edited by symmetal
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16 minutes ago, symmetal said:

If all the surfaces giving reflection dots are parallel to each other then the dot on the paper furthest from the laser would be from the reflective surface which is furthest away from the laser, which would be the cover slip (also the pixel beneath it which is likely obscured by the cover slip dot). This possibly explains why the middle dot is 'cleaner' as its just reflected off the AR glass. The dot reflected from the cover slip has to pass through the AR glass twice, so encounters 4 extra surfaces which would likely increase the flaring from the cover slip reflection dot.

On the other hand, if all the surfaces were parallel then all the dots would move as one and each describe the same diameter circle and it wouldn't matter which one you chose to use as a reference, as when you correct the tilt on that dot all the other dots also will be corrected.

If the surfaces aren't all parallel which is the case in your situation, as the dots don't all move together as one when you rotate the camera, then the above scenario diesn't hold true, so you have to make a guess as to which is the right dot, but as mentioned above it's likely not the 'cleanest' one. 🙂

Alan

 

Interesting, as when the filter was fitted the three dots were in almost a straight line and directly in a line from where the laser is mounted, so the image below shows the three circles each dot made, the top dot is gone as the filter was removed after I plotted the circle, so maybe it is the bottom one, as it has some flaring and is furthest away from the laser, but does not explain why the circles are different diameters….the middle one is quite small and almost obscured by the dot….this one we think is the AR window…so does this mean the AR window has less tilt than  the sensor, is that why the circle is smaller…..?/🤔🤔🤯🤯

 

C30EED4C-BF81-43C9-8969-37E0D5C3F9B5.jpeg

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If the surfaces are tilted with respect to each other, ie. not parallel, than yes, they will describe different diameter circles. This is your situation. It's possible the AR window has some opposite tilt compared to the cover slip so has cancelled out some of the camera tilt, hence it plots a smaller diameter circle.

Alan

Edited by symmetal
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Yes, spot on….excuse the pun…

I too have just realised this, the AR window must also be a little out of true with the front face of the filter drawer I have fitted and that I am rotating the camera on, but not as much as the sensor, hence the two different size circles, also the more reflective surfaces you add puts more dots in the line, and as you said, the further from the sensor the surface is, the closer to the laser mount the dot falls, so with this logic, the bottom most dot is the correct one, so I had it right to start with…

If I add the filter back it added a dot and I also added another surface under the camera and it added another even closer to the laser mount, so it seems to hold with what we have said, or more like what you said….😂

Also out of the filter, the AR window, and the cover slip, the cover slip has the most tilt….in relation to the front Face I am rotating on…😮😮, not good…

Thanks for helping as I have gone on enough to you about this, I must be driving you mad…👍🏻

Edited by Stuart1971
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Glad we're in agreement. 😁

I put most of the imaging train on the jig just so that if there is some tilt caused by the other components they will all be cancelled out by the tilt adjustment. This assumes that the camera rotator is before the train on the test jig, which is normally the case. This allows you to rotate the camera orientation without affecting the tilt. In reality I've found that the camera itself has been the cause of most if not all of the tilt, and the other component contribution hasn't been significant.

As you're using a separate tilt adjuster this has to be part of the train on the jig and if using a filter drawer you may as well include that too.

If you wish, you could just put the camera alone on the jig and see how the results compare with your previous results. It's likely they will be similar implying that the camera itself is the main cause of tilt which is preferable than having it spread out over various components.

Tilt on the AR window itself doesn't matter. It's only the cover slip/sensor which needs to be correct. 🙂  Your filters are most likely tilted in different directions slightly, each time you put them in, but it doesn't affect the image tilt.

Alan

Edited by symmetal
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Ordered the Baader UFC tilt adapter today so should be here on Wednesday, perfect as I use the baader UFS filter drawer system, and this fits straight to the back of that with just 9.75-10.5mm backspace, simple to adjust as the adjustment screws are in the edge and have in and out screws, couldn’t be simpler….so it’s perfect for me, as soon as it arrives the camera will be back in the tilt jig, and all sorted…hopefully

Why didn’t QHY just make a tilt adapter built into the camera, would save so much trouble, there QC control is rubbish TBH to send out cameras with this issue….not happy at all

https://www.baader-planetarium.com/en/baader-ufc-tilter.html

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On 01/10/2022 at 16:50, symmetal said:

It doesn't make any difference where on the sensor the laser is pointed as long as you get a visible reflection off it. The sensor and cover slip glass are optically flat, one would hope, 😉 and the angle of reflection is the same from any part of the sensor.

Laser pens like this are commonly used as they are cheap and plenty available from ebay. Just check it's a 1mW one, and has Class 1 on the label. Red or green is fine though red seems most commonly used. I made a 3d printed holder to keep the pen at an 10 degree angle and it can then be easily moved around for the clearest reflection if you have a filter wheel, tilt adjuster etc. also fitted to the jig which reduces the available sensor area visible to the laser.

It's the flat cover slip reflection which you want to adjust on. It's generally the brightest reflection spot, though there may be two or three reflection spots close together. Rotating the camera and see what group of bright dots move the least points you to where to start. Moving the laser pen a little should make the pixel reflections move so they can be eliminated. If you can't tell which is the right spot you have to choose one, adjust the tilt so it doesn't move when the camera assembly is rotated, and try it on the scope for a test image. If it looks good you're OK. On my ASI6200 it took two tries and I had to choose the second spot before the tilt was gone. 🙂

Alan

Well I got one of those laser pens you linked to, and was supposed to be a class II 1mw laser, and the one that has arrived is a class III 5mw laser, so am a bit loathed to point this at my sensor….😮😮

 

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1 hour ago, Stuart1971 said:

Well I got one of those laser pens you linked to, and was supposed to be a class II 1mw laser, and the one that has arrived is a class III 5mw laser, so am a bit loathed to point this at my sensor….😮😮

 

That's the hazard of buying the cheap pens off ebay, I'm afraid. I bought them from two different sellers and one was class 2 and one was class 3. You can go for a refund but I didn't bother as it wasn't worth the hassle for the price.

I doubt a 5mW will cause any problems but not sure if I would want to risk it on an expensive camera. 🤔

Alan

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43 minutes ago, symmetal said:

That's the hazard of buying the cheap pens off ebay, I'm afraid. I bought them from two different sellers and one was class 2 and one was class 3. You can go for a refund but I didn't bother as it wasn't worth the hassle for the price.

I doubt a 5mW will cause any problems but not sure if I would want to risk it on an expensive camera. 🤔

Alan

I too think a genuine 5mW laser would not damage a sensor or your eyes as they are still deemed (eye safe) but you have no actual guarantee that these lasers are indeed 5mW or what the output spectrum is, could be anything.

Alan

Edited by Alien 13
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Considering sensors in all-sky cameras can have the full sun focused on a group of pixels for around an hour without apparent long term damage, it seems doubtful that a 5mW laser would be a problem to the sensor itself. The main issue I think would be looking at the results on the paper as it will be a bit too bright to study closely. With the 1mW laser I find it hard to focus properly on the reflected spot, and have to use a kind of averted vision to assess it accurately. A 5mW would be rather uncomfortable to assess I suspect without sunglasses or something.

Alan

 

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On 15/09/2021 at 00:09, symmetal said:

Made my version of the jig and it's a great success. 😊

Cut up an odd piece of 18mm ply for the box and 3D printed a camera holder to fit a 2" nosepiece, or if you're lucky a 2" diameter 48mm extension spacer as the one on my FLT98/ASI6200MM was exactly 2" outside diameter. Also made a 3D holder for the laser pen angled at 10 degrees. I tried one at 13 degrees but it was more critical in laser placement and the 10 degree one worked fine. A clothes peg makes a handy on/off lock. 😀

Here it is with the 6200, filter wheel, tilt adjuster and a 16.5mm long 48mm spacer fitting nicely in the 3D printed adapter. The filter wheel unbalancing it had no effect on laser pointing. 🙂 The 3D adapter centre hole is 51.00mm across. I did make one with 50.90mm diameter but it was rather too stiff to turn.

Box.jpg.b18ad3bdbcdbbbb2499a208b2446c8bc.jpg

Adapter.jpg.e8f50f3a8806d8f57e589f8487e27eab.jpg

6200.jpg.0c6463b3735b991b0d87fce81061aa9f.jpg

Here's two initial images with the camera rotated around 180 degrees between them. As you can see it was way off. There were 3 laser dots near the centre. One appears to be aligned with the pixel grid, the opposite one was much brighter, with a faint dot between them. I assumed the brightest one was the sensor cover but it didn't matter in reality as when the tilt was adjusted to optimum, all three dots stayed in the same place while the camera was rotated. I needed to put a lot of tilt adjustment with a gap on one side around 0.5mm 😲 as can be seen on the picture.

The filter being in the path didn't seem to affect it and reflections from it weren't visible. 

Before.jpg.b1879dd1376ac0a80fef16210bf2d183.jpg

69979752_Before180.jpg.e6b47d753b0903fe35d59c35de09634a.jpg

864832072_GerdNeumann.jpg.16aca2f6aa5a3ffe91addeee2d20278d.jpg

It was clear this evening so went for a test image and have never had the left side stars so good. The far right hand side shows rather bad coma 🙁 but the star centres are sharp. Not bad for a full frame sensor. The coma was there before adjustment, but didn't appear so bad as the stars were more out of focus. The CCDI images look good and corners pretty similar with zero tilt reported, (first time ever). CCDI seems to ignore coma and just use the star centre for the test.

1838371109_CCDICurvature.jpg.22d790e5f5b569cac8033884b8565d58.jpg

1400288660_CCDI3D.jpg.6e50d2c20de8396b4ecd664cd7cdb711.jpg

Here's the corner crops of the test image. If not for the coma I'd be very happy but I don't have to keep fiddling with the tilt anymore as I know it's optimum. 😀 I tried another image rotated 90 degrees and it was very similar.

1998777717_01tiltjigcornertest.thumb.jpg.10966fe2ba56b93dc0bfc76bc43db6ef.jpg

I'll have to live with the coma but it's only on the far right, and binned 2x2 it won't look so bad. Wonder if Es Reid can align the scope to improve it, as I did buy the FLT98 from FLO. 😁

Alan

Hello,

I got a new better laser for my testing so I re did it, and got it pretty much perfect, but I noticed in your images about of your laser reflections, that’s you have the same three dots as I did, when I had a filter fitted, only had two after I removed the filter, also I did some testes to find out exactly which was the correct dot to use for adjustment, and so I added two more reflective surfaces into the image train, and each one added another dot closer the laser base, so it turns out that the dot furthest away from the laser will always be the sensor cover slip, and so the correct one to use…the more surfaces added further from the sensor, adds more dots closer to the laser base

So you may well have gotten the wrong one in your case, but as you say it didn’t matter as they all did not move anyway, in my case even with the cover slip dot static, the sensor window dot still moved slightly…

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@Stuart1971 Glad you got the adjustment working well now Stuart. Now for the image test to confirm it. 😉

I wasn't thinking too much about the reflection position in relation to the laser at the time, and chose a likely candidate which actually worked out fine for me. 😃 As you've noticed on yours, the protect window is not truly parallel to the sensor, which doesn't matter at all. As the protect window usually sits in a silicone moulded frame which squashes as the front cover is tightened to hopefully make it airtight, it's pure luck as to whether it ends up parallel.

As you say, it's most likely the furthest dot from the laser will be the cover slip, though this does rely on the surfaces in front of it being roughly parallel to the sensor in the first place, which should hopefully be the case. 😊

Alan

 

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  • 1 month later...

I've only just come across this thread & I have to say it's very informative as I have tilt issues myself & when using the RASA it shows up a lot more. I've got a tilt adapter so I'll be doing the same with the 26C I own, by looking at everyone's pictures I'm sure I can knock up something. 
 

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  • 2 weeks later...

I decided I needed a filter wheel, and in adding this to the imaging train, I no longer have access to the tilt adjustment screws on the camera faceplate.  On testing the kit last night, it's got a lot of tilt across the long axis of the chip - right side stats ouf of focus, so I need this to be corrected.

I came across these items.  They are made of PTEG and have a small raised bit that it either 0.1mm 0.2mm or 0.3mm high, and would be handy enough used on the chip tilt rig instread of the faceplate.

Has anyone used them, and does anyone see any reason why I couldnt 3d print them in PTEG myself? I was going to order them but FLO is out of stock for 15-20 days, so likely the other side of Xmas.  I have a 0.25mm nozzle that should give me a layer height of less than 0.1mm.  

 

Any advice welcome.

 

Astrodymium Rotating Tilt Adjusters Astrodymium Rotating Tilt Adjusters for M48 Threads | First Light Optics

 

 

Astrodymium Rotating Tilt Adjusters for Select Threads

Astrodymium Rotating Tilt Adjusters for Select Threads

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2 hours ago, tooth_dr said:

I decided I needed a filter wheel, and in adding this to the imaging train, I no longer have access to the tilt adjustment screws on the camera faceplate.  On testing the kit last night, it's got a lot of tilt across the long axis of the chip - right side stats ouf of focus, so I need this to be corrected.

I came across these items.  They are made of PTEG and have a small raised bit that it either 0.1mm 0.2mm or 0.3mm high, and would be handy enough used on the chip tilt rig instread of the faceplate.

Has anyone used them, and does anyone see any reason why I couldnt 3d print them in PTEG myself? I was going to order them but FLO is out of stock for 15-20 days, so likely the other side of Xmas.  I have a 0.25mm nozzle that should give me a layer height of less than 0.1mm.  

 

Any advice welcome.

 

Astrodymium Rotating Tilt Adjusters Astrodymium Rotating Tilt Adjusters for M48 Threads | First Light Optics

 

 

Astrodymium Rotating Tilt Adjusters for Select Threads

Astrodymium Rotating Tilt Adjusters for Select Threads

Hi Adam, 

yea I have them, and tries but did not get on with them, also they add 0.4mm plus the extra tilt amount…so the backspacing was 0.5, 0.6 or 0.7mm which was too much for me as I needed a tilt adjustment on 0.2mm. They also can move when you tighten up spacers that have these between….

I have since bought some copper shim at 0.2mm and put it in the correct position between two of the spacers on my QHY camera and it works really well indeed…simple to do too…

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Correction to my first post, the shim is actually 0.1mm and had to fold a piece in half to get the 0.2 as shown in second image…👍🏻 this was enough to move the laser dot on my tilt jig back to the centre of the circle it was making, which was approx 5mm diameter…

Edited by Stuart1971
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I have used aluminium foil folded few times (squeezed in vise between flat surfaces) and placed between spacers in the optical train to correct tilt. I also once tried kapton tape (3 or 4 layers as I remember) once and that also worked okay. 

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