Gina's DIY All Sky Cam - Complete Redesign

[Gina]

Very interesting - thanks folks   Yes, a telescope would collect a lot more light than a fisheye lens though it would be spread out more.

One point about the ZWO ASI120MM and ASI120MC is that they include a fisheye lens for use as an all sky cam with no warning about the sun.  I think that means they are tolerant of daytime full sunshine.  If I were to buy one of these I would try it as an all sky cam with it's 150 degree lens left out in the sun and if any damage occurred I could send it back as unsuitable for specified use (or whatever the legal phrase is ).  There are three reviews on their website that all mention use as all sky cam and no mention of the sun.

I conclude that the ZWO ASI120 cameras are safe in the sun.  The same conclusion that I came to before.  As for the QHY5 though - do I risk it?  Still don't know - a replacement camera would cost serious money in my current financial situation.

[JamesF]

The Moonglow ASC and the Orion Starshoot ASC also appear to have nothing to protect the sensor from the Sun.  Both suggest the cameras can be used for daytime imaging.

James

[JamesF]

If you look here: http://www.astrosurf.com/re/all_sky_camera.html

Click on the various links labelled QHY5.  There's clearly no shutter or anything similar in that camera.

James

[brown_rb]

I dont understand why you dont consider using a RC servo motor to control the shutter, the foil could easily attach to it and you would not have issues related to position or return spring strength etc? You would have precise positioning and not have to worry about extra components to get the exact current required.

[Gina]

I see what you mean James   Looks like I have wasted a lot of time and effort on an unnecessary part of the project - oh well...

[Gina]

I dont understand why you dont consider using a RC servo motor to control the shutter, the foil could easily attach to it and you would not have issues related to position or return spring strength etc? You would have precise positioning and not have to worry about extra components to get the exact current required.

I have done - the meter movement is simpler and failsafe.

[Horwig]

OK, if we don't use a shutter, I wonder if there's enough power from the usb to run the dew heater. Then no 12v feed, much simpler

H

[Gina]

Maximum power from the USB is 0.5A at 5v some of which is needed for the camera.  Anyone know how much current the QHY5 takes?

[Gina]

I wonder where I put the original casing for my QHY5

[JamesF]

OK, if we don't use a shutter, I wonder if there's enough power from the usb to run the dew heater. Then no 12v feed, much simpler

H

USB devices have to negotiate how much power they're allowed to draw.  I'm not sure you can have the camera say, for example, "I need 250mA" and then draw 500mA.

James

[JamesF]

Maximum power from the USB is 0.5A at 5v some of which is needed for the camera.  Anyone know how much current the QHY5 takes?

I can probably find out how much it wants if I plug mine in.  I'll just find it.

James

[Kropster]

+1 for the solar cell idea.

Simple and efficient.

[Horwig]

Well, in that case, I have the wall wart, I have the nichrome wire, might as well stick with the 12v

H

[JamesF]

I can probably find out how much it wants if I plug mine in.  I'll just find it.

James

It says:

  Configuration Descriptor:    bLength                 9    bDescriptorType         2    wTotalLength           32    bNumInterfaces          1    bConfigurationValue     1    iConfiguration          0     bmAttributes         0x80      (Bus Powered)    MaxPower              100mA

So allegedly 100mA then.  If the PC knows it is required to supply 100mA I'm really not sure it's a good idea to draw more.  That may have unintended consquences.  I believe there are devices that basically just place a load across the power terminals for USB, but as far as I'm aware that's outside the USB spec. and I'd not personally do it on something I wanted to stay working.

James

[Gina]

I plan to use a servo motor for remote focussing and that needs a 5v supply.  Could run the dew heater off that and use an old PC PSU.  OTOH if I mount the ASC on my observatory, I have a 12v battery backed up supply.  I can hear people ask "In that case why were you worrying about power outages?"  Senior moment?

[Horwig]

Gina, does it really need complicated remote focusing? will focus drift, or will it be a fit and forget focus system.

Is there not a way of using a simple mechanical focus system?

Just a thought

H

[JamesF]

Yes, perhaps it would be worth finding focus, then trying it out for a while to see if focus does drift?

James

[Gina]

I'm having second thoughts about remote focussing and thinking of maybe a shaft running through a grommet as a gland to seal it and a knob on the outside.  It doesn't need to be in it's high inaccessible position for focussing.

[Gina]

Reluctantly I've removed the meter movement from the lens to camera box.  If a shutter isn't necessary it would be a bit daft to continue with that system even though it's nearly done   Rather annoying but that's the nature of things...

[JamesF]

Have a look at this thread too, Gina: http://stargazerslounge.com/topic/240630-another-diy-all-sky-camera/

The QHY5-II has the same sensor as the QHY5.

James

[Ajohn]

The need for the shutter depends on the lens - just as it does when a magnifying glass is used to set fire to something. I would be cautious personally.

John

-

[Gina]

I can soon alter the black lens to camera box to take the meter movement if I change my mind again   The box I'm planning to use will have enough room.

[Gina]

New lens to camera box with mounting lugs added.  I shall be mounting the ASC in a waterproof junction box with dome and mounting tube glued into the top.

[Gina]

Box and dome.

[Horwig]

I'm bowing out of the all sky market for a while, I think my qhy5 is bust, pc doesn't recognise it any more. That's what I get for removing the usb socket and hard wiring to the board...

Huw