DIY all-sky cam?

[allcart]

Very well spotted Gina.

[Gina]

One thing I'm not quite happy with in all the ideas expressed so far is that they are not "fail safe".   Not too concerning if using a webcam but an expensive CCD camera is another matter.  Power is needed to run the camera, even if it's only obtained from the USB so I'm thinking of a simple control circuit that would hold the shutter open when powered and return to closed (safe) position with a spring.

Think I'll have to make up a simple test rig maybe with a magnet and coil.  Bit of light relief

[allcart]

Here is my incarnation of a meteor cam. I bought one of these cctv video cams from Rfconcepts. http://rfconcepts.co.uk/camera-wdr-58ep-2686.html

Very sensitive cctv cam with remote operation and coupled with a Computar 2.3mm f1.4 lens gives a fov of around 110deg.

I constructed a housing from 4" drain pipe and used a pipe coupler to attach the dome to. This coupler slips off to allow access to the lens for adjustments.

The housing is held with a 4" tube ring attached to a U shaped bracket. The bracket bolts onto a 24' mast that extends above the roof level to avoid reflections from my garden streetlight. The mast can be rotated from ground level, but tilt adjustment is done from a stepladder on the shed roof.

Since the initial build, I have replaced the dome with a flat glass plate as this reduces unwanted reflections even better than the dome. For a 180deg view the dome would be needed or vignetting would occur.

I have also painted the inside of the grey  pipe coupler black and even the edge of the glass plate to eliminate reflections.

results.

http://tinyurl.com/p6f7p8k

opens in new tab http://tinyurl.com/pmyrf88

Next step is a dew heater.

[tekkydave]

Don't forget to gear it down 2:1 to give a 24 hour rotation period.  Unless you've got an extremely rare 24 hour analogue clock, of course

I hadn't thought of that. That's why scientists do peer review

[Gina]

I've been giving the shutter some thought.  As I see it the shutter could be pivoted horizontally or vertically.  In some ways turning the shutter horizontally (vertical axle) may be easier but OTOH with the shutter moving out of the way vertically (axle horizontal) it could be returned to the closed position by a weight and gravity.  Thinking continuing...

[Gina]

Another idea.

[Gina]

Weight and actuating lever added.

[Horwig]

Gina, I think there's a lot going for your idea of using an analogue voltmeter movement, powered by a photo voltaic cell. Especially if it could be fitted between the lens and the sensor, a 6mm sq piece of metal foil should be sufficient, and light enough for a sensitive meter movement.

All we need to do is close the shutter when we have strong sunlight. Sun through cloud will do the sensor no harm. So as long as we get a good voltage from the cell, and use an appropriate movement I see no problems.

Huw

[garethmob]

just another idea but coulnt it be controled by somthing like an arduino.  programed with the set time of sun rise and sun set every day (dosent it increase and decrese by an exact set figure every year to balance it out?) 

as a backup it only removes it if there is power, if there is no power it springs shut. 

[yesyes]

An Arduino might be a bit overkill for this. But if I was to use one, instead of having it calculate the sunrise and sunset times (they don't change in a linear way) I would just connect a cheap LDR to it that would tell the Arduino when it gets dark.

[Gina]

Linkage added.

[Gina]

Gina, I think there's a lot going for your idea of using an analogue voltmeter movement, powered by a photo voltaic cell. Especially if it could be fitted between the lens and the sensor, a 6mm sq piece of metal foil should be sufficient, and light enough for a sensitive meter movement.

All we need to do is close the shutter when we have strong sunlight. Sun through cloud will do the sensor no harm. So as long as we get a good voltage from the cell, and use an appropriate movement I see no problems.

Huw

It has the benefit of simplicity   I agree that it should be pretty reliable.  I think it may be a problem fitting it between lens and sensor as the back focus is so small.  It might be worth stripping down a QHY5 - might look at that, but a test first may it clear that the QHY5 is rubbish

I have ordered the Fujinon fisheye lens - I calculated that I could afford just under 120 quid   It's clearly worth going for the shorter FL and wider aperture.  Also, if it will work with the QHY5 it'll save using a Lodestar.

[Gina]

just another idea but coulnt it be controled by somthing like an arduino.  programed with the set time of sun rise and sun set every day (dosent it increase and decrese by an exact set figure every year to balance it out?) 

as a backup it only removes it if there is power, if there is no power it springs shut. 

An Arduino might be a bit overkill for this. But if I was to use one, instead of having it calculate the sunrise and sunset times (they don't change in a linear way) I would just connect a cheap LDR to it that would tell the Arduino when it gets dark.

Naturally, I thought of an Arduino but agree with Chris - overkill.  LDR, phototransistor, photovoltaic cell are all possibilities.

[Gina]

I have a nasty feeling that I've thrown my old meters out but I'll have a rummage in the shed   I've also been boning up on my "A" level physics re. magnets, coils, solenoids, motors etc.

[tekkydave]

How about cannibalising this for parts http://www.ebay.co.uk/itm/Solar-Powered-Rotating-Jewellery-Mobile-Phone-Ring-Bracelet-Watch-Display-Stand-/121171081540?pt=UK_Home_Garden_Night_Lights_Fairy_Lights&hash=item1c365bf944

[Horwig]

Gina, My qhy5 is semi stripped down already, I'd mangled the usb socket, so it's hardwired to the usb cable. The board could be mounted by a single bolt through the hole in it that supports the brass spacer. My lathe skills are not good enough to produce a c thread, so have bought a T to C adaptor, which will now be mounted in the center of an ali disk which will make up the new face plate. This will hopefully allow space by the side of the board for a stripped down meter movement.

You'll just have to imagine it, I can't use sketchup

Have just ordered one of these:

http://www.ebay.co.uk/itm/190836750754?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

worth the four pounds thirty seven I reckon.

The plan is then to use the 5v from the usb, with an ldr and a couple of transistors to make a light dependant switch to control the meter. The meter will cover the sensor when off, and the switch will power the meter when the light drops, so giving me a level of fail safe.

Will keep you informed as it happens, but won't be soon, delivery time is up to a month.

H

[Gina]

Gina, My qhy5 is semi stripped down already, I'd mangled the usb socket, so it's hardwired to the usb cable. The board could be mounted by a single bolt through the hole in it that supports the brass spacer. My lathe skills are not good enough to produce a c thread, so have bought a T to C adaptor, which will now be mounted in the center of an ali disk which will make up the new face plate. This will hopefully allow space by the side of the board for a stripped down meter movement.

You'll just have to imagine it, I can't use sketchup

Have just ordered one of these:

http://www.ebay.co.uk/itm/190836750754?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

worth the four pounds thirty seven I reckon.

The plan is then to use the 5v from the usb, with an ldr and a couple of transistors to make a light dependant switch to control the meter. The meter will cover the sensor when off, and the switch will power the meter when the light drops, so giving me a level of fail safe.

Will keep you informed as it happens, but won't be soon, delivery time is up to a month.

H

Interesting   I'll look forward to read all about your efforts

I shall wait until I get the lens then I can try the cameras.  It'll be handy if the QHY5 give a good enough S/N ratio.

[Horwig]

 It'll be handy if the QHY5 give a good enough S/N ratio.

I've already used the qhy5 in anger for an imaging session, and it worked fine as a tool to warn of incoming cloud. It will never give pristine images of the night sky, but within its limitations, and with darks, it was usable.

I am "fortunate" in that, even though I have nice dark skies, there is a reasonable town about two miles to my east which gives me the "benefit" that clouds are nicely illuminated with low pressure sodium lights. Hence, I'm not looking for the lack of stars, rather, big fat grey patches which signify cloud.

Paying work which I was going to do tomorrow has disappeared, so will start to do some metal bashing for this instead.

H

[JamesF]

My lathe skills are not good enough to produce a c thread, so have bought a T to C adaptor

To be honest it may be far easier than you imagine depending on the material you're working with.  The first threads I ever turned on a lathe were in a fairly large chunk of aluminium I'd machined to replace the SCT mounting plate that formed part of an external SCT focuser.  The SCT uses a 2" thread and I wanted an internal 50mm thread so the focuser would fit the tube of my PST.  Once I'd set the leadscrew gearing correctly I turned the chuck by hand and made as many passes as were required to get the right depth of thread.  It all worked beautifully first time.  Turning the chuck by hand means you can take things at whatever speed suits you and check it's all working ok as you go along which makes the entire process quite relaxed.  Well worth a go if you have the need again.

James

[Horwig]

This is puting the cart before the horse, since the meter hasn't arrived, and I  don't have a drawing for it, but what the hell, I've started.

This is the stripped out QHY5 on its new face plate. I'm hoping there's room for the meter by the side of the pcb, if not, I can move the whole assembly off center.

It looks as if there is just enough room for the shutter mechanism between the sensor and the face plate.

Huw

[Gina]

Looking good

Does the case of the QHY5 separate by unscrewing it?  The aren't any little screws holding it together so I presume it unscrews just benind the mounting flange.

[Horwig]

Yes, the front screw off, the board just sits in the case, the usb and st4 connector locate it, and there are two spacers that hold it tight against the front face.

H

[Gina]

Thanks Huw

[JamesF]

I found mine very stiff to unscrew when I wanted to take it apart to clean the sensor, but if you look closely at the edge near the front of the camera body you can see the join where the two pieces of the case fit together.

James

[Gina]

I found mine very stiff to unscrew when I wanted to take it apart to clean the sensor, but if you look closely at the edge near the front of the camera body you can see the join where the two pieces of the case fit together.

James

Yes, I noticed the join.  I have had a half-hearted try undoing it but not succeeded yet.