ASI290MM-C Very strange effect when power is on

aleksandrrr

Hello!

I see a very strange effect. When I switch on power for cooler, stars becoming inflated and elliptic. See attached image for example (no, it is not a tracking or collimation problem. Stars are very accurate if camera runs in non-cooling mode, but when I plug in power cord and restart, stars becoming elliptic-shaped again. It is clearly visible in live preview with short exposure). In result, I cannot use cooling because it ruins resolution of the image!

aleksandrrr

Capture software is not important. Effect is the same in any program (FC, SharpCap...).

Sam@ZWO

do you think is it because of the fan?

aleksandrrr

When I focus on bright star with short exposure (50 ms), I see ellipse instead of diffraction rings. But if I switch power off and restart camera, I see no such problem.

I have no ideas, what is it. You think it may be an effect of high-frequency fan vibration? Can I plug off fan cord in the camera manually or it may cause a damage to electric circuits of cooler because of overheating? Of course, cooler cannot be very effective without fan...

aleksandrrr

Yes, I can confirm. Fan vibration is cause of the problem :(

I compared live views with and without power supply.

Sam@ZWO

maybe you can loose the 4 screws of fan and check if it's better?

aleksandrrr

OK, I think I will remove screws completely and will do some "soft" connection.

However, in this case I must admit that default fan connection is not perfect. May be you must redesign it in future cameras, otherwise this effect will occur with high probability at many users...

Sam@ZWO

the fan is maglev and very quiet actually

I never see one fan from other astronomy cameras as quiet as ours

so I suspect just one installation issue which fix too tight?

aleksandrrr

You right, maglev works quiet because it practically has no friction in bearing, but magnetic centring does not eliminate vibration, which is easily transfered to the stator of the fan even though there is no direct mechanical contact.

So, it is not very important, which type of fan to use. Any fan will produce some vibration which must be damped

Sam@ZWO

Aleksandrrr wrote:
You right, maglev works quiet because it practically has no friction in bearing, but magnetic centring does not eliminate vibration, which is easily transfered to the stator of the fan even though there is no direct mechanical contact.

So, it is not very important, which type of fan to use. Any fan will produce some vibration which must be damped

how is it after you adjust the fix screws

aleksandrrr

It has not changed anything. It is predictable, because connection remains very rigid.

I made a soft connection through foam rubber (without screws), but I cannot check results in next two weeks.

Sam@ZWO

Aleksandrrr wrote:
It has not changed anything. It is predictable, because connection remains very rigid.

I made a soft connection through foam rubber (without screws), but I cannot check results in next two weeks.

OK, I am waiting for your good news

you are the second one report this issue

the first one use SCT too