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Old 14-11-2013, 07:57 AM
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pvelez (Pete)
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Diagnosis - shutter or electronics?

Here is a challenge for armchair doctors/camera experts.

Consider the attached screenshot. This is a 30 second image taken with a STX16803. I took 6 images at 30s last night - 3 of them looked like this while the remaining 3 had the full field of the camera. They were alternating ie dodgy, goood, dodgy etc.

Do I have problems with the electronics of the camera so it isn't reading the sensor properly? Or is the shutter playing up?

I didn't have the opportunity to take the camera off the scope last night but will do so later today. I'd be interested to hear if anyone else has seen this.

Pete
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Old 14-11-2013, 09:01 AM
rally
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Looks electromechanical to me

Best guess
Something has happened to the shutter mechanism.
Either the mechanism is getting stuck or possibly the sensor is in error
Could be friction or misalignment - the motor cant quite turn the shutter every time, or there is something stopping or interfering
Does this occur with every filter position ?

Rally
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Old 14-11-2013, 09:04 AM
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Merlin66 (Ken)
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Don't know if it's similar, but I had something similar happen with my ATiK...never got to the root of the problem but disconnecting all the USN connections, power connections re-boot computer and then re-attaching everything brought it good.

Could be a buffer issue during download???
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Old 14-11-2013, 09:05 AM
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Thanks Rally

I'm inclined to agree. Misalignment of the shutter is the likely culprit

The filter wheel is well away from the shutter - they are separate units so I don't think it is that.

Pete
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Old 14-11-2013, 09:07 AM
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pvelez (Pete)
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Quote:
Originally Posted by Merlin66 View Post
Don't know if it's similar, but I had something similar happen with my ATiK...never got to the root of the problem but disconnecting all the USN connections, power connections re-boot computer and then re-attaching everything brought it good.

Could be a buffer issue during download???
Thats an interesting thought Ken - I have sent an email off to SBIG to see if they have any thoughts.

The fact that the darkened parts of the frame culr up at the edges points to the shutter to me as a read out issue would be unifrom across the chip - I think!

Pete
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Old 14-11-2013, 09:24 AM
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Merlin66 (Ken)
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Pete,
Hmmm
If it were a mechanical issue - why doesn't it affect every frame - rather than 1/2???
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Old 14-11-2013, 09:47 AM
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Quote:
Originally Posted by Merlin66 View Post
Pete,
Hmmm
If it were a mechanical issue - why doesn't it affect every frame - rather than 1/2???
If the shutter is the same as my ST10 then it is a wheel with 2 holes in it that rotates in front of the CCD. It may be sticking at 1 point only thus only happening every 2nd exposure.
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Old 14-11-2013, 11:53 AM
rally
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It may not affect every frame because (potentially) the mechanicals are sticking - either due to friction or interference or misalignmen tof bearings or shafts

Steppers simply get pulses and they step - if they are jammed or under too high a load then the pulse may not have any effect or may have a partial effect.
The stepper motor that drives it may just pulse so many times and assume its fully rotated without checking its position or maybe there is a problem with the sensing - I am not familiar with that camera or its design.

The repetition here could be that it requires two attempts to drive the shutter to complete one successful shutter cycle - its just a guess !
Or maybe if its a rotating double shutter wheel, then it may be that there are two sides (cutouts) to the shutter and one side doesnt jam as it turns but the other side does.
(edit - oops, sorry I see Terry already said that)

It does seem surprising that there is no error reported or verification by the system that the shutter ius doing what its supposed to do - but it may just assume that its always doing exactly what its supposed to do without checking - since fast exposures are just that - fast.

But to have something that jams occasionally in a tight spot but not always is not unusual in delicate instruments when there is interference

Pete
Have you dismantled the camera recently or done anything to it ?
Or dropped anything into it ?

Rally
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Old 14-11-2013, 08:46 PM
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The good news is that this is a shutter rather than an electronics issue - at least the read out part.

The other news is that its still playing up. It looks to me as if the sensor is not registering where the shutter is.

I'm in touch with SBIG - I am sure they will have a suitable fix.

Pete
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Old 17-11-2013, 11:53 AM
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Solved - I think (don't want to jinx it)

The wire that operated the rollers in the shutter was snagging on the chamber window. I adjusted the roller attached to the motor (which was out of alignment enough to throw it all out) and it runs smoothly.

Now for the rain to stop!

Thanks to David at SBIG and Peter Ward who have been most helpful.

Pete
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Old 17-11-2013, 01:39 PM
SpaceNoob (Chris)
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Quote:
Originally Posted by pvelez View Post
Solved - I think (don't want to jinx it)

The wire that operated the rollers in the shutter was snagging on the chamber window. I adjusted the roller attached to the motor (which was out of alignment enough to throw it all out) and it runs smoothly.

Now for the rain to stop!

Thanks to David at SBIG and Peter Ward who have been most helpful.

Pete
Great news Peter, 2 issues seem to be sorted out for you now with both the EFA and the Camera, looking forward to seeing some good results come from your setup... Rain could be my fault, I have a shiny new cdk sitting here, once it arrived the sky has either been full of smoke or clouds......
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