All Sky Camera Revisited

[Gina]

Following on from my Blog - Gina's Ultimate All Sky Camera - and the catastrophe in which the lens and USB port of the ASI120MC-S camera were destroyed, I now need to rethink the whole ASC.  The lens is/was the Fujinon fisheye 1.4mm FL f1.8.  This is an excellent model of lens though with a problem of no provision for focussing other than unscrewing the mounting a bit.  There is also no aperture control.  I've done some searching for fisheye lenses and some cost hundreds of pounds.  A replacement for the Fujinon would cost £65.  I can see why commercial ASCs cost so much.  Hence I'm open for any suggestions, please.

[vlaiv]

How about one of these two?

https://www.firstlightoptics.com/zwo-accessories/zwo-replacement-150-degree-wide-angle-lens-for-zwo-asi-cameras.html

https://www.firstlightoptics.com/zwo-accessories/zwo-cs-lens-2-8mm-12mm-f1-4.html

Or this one:

https://www.teleskop-express.de/shop/product_info.php/info/p10246_ZWO-CCTV-Lens-2-5mm-170-Degree---for-ASI-Cameras-without-cooling.html

[Gina]

Focal length is too long - they don't cover the whole sky.  I have the 150° lens already - came with the ASI 120MC-S camera.  I have a good clear site and apart from N-NW have views mostly down to horizontal.

Edited February 28, 2019 by Gina

[Stu]

Is this any good Gina? I found this website via ABS recently and they have some interesting stuff, including domes and circular dew preventing heaters. Will probably buy a few bits from here at some point.

https://www.dewcontrol.com/155mm_All_Sky_Camera_lens/p3099125_19122279.aspx

[Gina]

Looks interesting though I'm rather surprised if a 1.55mm lens gives 180° sky coverage with the ASI 120 when my 1.4mm lens didn't quite.  I like that it has focussing though.  The ASC image above was with the ASI 185MC camera which has a bigger image sensor.

[Gina]

I've dug out my Fujinon zoom lens which is a 1/3" lens rather than the Fujinon DF1.4HB-L1 1/2" lens and easily covers the whole sky.  The problem with it is poor resolution near the edge of the image.  I'll try it - the ASI 120 is lower resolution than the ASI 178 I tried it with before.

[Gina]

Some good news - the ASI 120MC-S camera works ?  The bare pins on the USB3 port are making contact with a USB2 plug.

[JamesF]

Might be possible to remove the old USB3 socket and replace it then?

James

[Gina]

Yes.  Or I could solder wires onto the pins.  Or it might just see if it's alright with just a USB plug as it's working at present on the table.

[Gina]

I see two options for an ASC for nighttime use - a moderate priced one with the Fujinon zoom lens and ASI 120MC-S or a high priced version with the Fujinon DF1.4HB-L1 fisheye lens and ASI 385MC.  I was using a similar setup with the ASI 185MC, now superseded.  The higher priced rig would cost well over £400 and I can't afford that (unless I were to sell astro gear).

A disadvantage of the ASI 120 is that the minimum exposure is 64µs whereas the more expensive camera are 32µs which is just workable for daylight.  However, the zoom lens has a crude aperture control with just two leaves forming a diamond aperture when not fully open.  It also closes completely.  So overall, it seems the zoom lens is the one to go for ATM.  If my finances improve I might go for the high cost setup later.

[Gina]

So much for my "Ultimate" ASC.  More like "Economy" now!!  With a totally different design.

[Gina]

A top end ASC for nighttime might employ a Fujinon DF1.4HB-L1 fisheye lens and ASI 385MC-Cool with provision for taking the air supply through an air duct from inside the observatory.  The "Cool" version of these cameras adds another £300 to the cost - overall, not much change from £800 depending the cost of other parts.

[michaelmorris]

If you're after a very fast lens with a controllable iris, you could have a look at discontinued Computar CCTV lens such as the 2.6mm HG2610AFCS or 2.0mm TG2010AFCS or TG2010FCS-L.  These quality f1.0 lenses are amazing, but nowadays rarer than a rare thing on EBay.

[Gina]

I doubt these lenses have a short enough focal length to cover the whole sky.

[Gina]

Here's a photo of the Fujinon zoom lens.  I would like to control two functions - focus and aperture.  I can sort out the mechanics to drive the focus pin with a stepper motor but the aperture would only need two positions I think - fully open and about half closed.  I guess a stepper motor could be used for this but under conditions of power loss the actual position can become uncertain.  Another possibility may be a servo motor but the "9g micro servers" I've tried in the past have been very unreliable so I would need to find something better.  I shall also need to check if I can control one of these with the Raspberry Pi and INDI driver.  I'll have a read of my Raspberry Pi handbooks.

Edited February 28, 2019 by Gina

[Gina]

Seems the RPi can handle servo motors alright just using PWM and I see no reason why I can't write an INDI driver to control it (or rather modify one I've already got). 

These servo motors look suitable :- MoPei 2Pcs MG996R Servo Metal Gear Digital Servo for Helicopter JR RC Car Boat Motos  I might be able to use one for focussing too.

[Gina]

Here's a daytime image but clouds are not best for assessing focus that will have to wait for a clear night sky.  This is with an exposure of 64µs and the aperture control around half way.  I have adjusted the focus by hand with the rig pointing out of the window.  I can see the chromatic distortion around the edge of the image that I remember with this lens.  Stars show as separate RGB pixels around the edge.  This didn't happen with the other lens but they are several hundred pounds new and even £65 used.  Being an OAP I have to go with the "Economy" version! ?

[Gina]

Having said I can only afford the "Economy" version, I'm thinking I'm not going to be satisfied with second best but I'll test what I've got.  I might buy one of the used Fujinon DF1.4HB-L1 fisheye lenses though there might be a more suitable lens.  I might go for the ASI 178MC camera rather than the ASI 385MC for it's larger sensor (assuming the DF1.4HB-L1 lens).  I already have the mono version that I could try pro tem.

Edited February 28, 2019 by Gina

[Gina]

The weather forecast is certainly not promising for the next 5 days - rain, rain and more rain.  This is one of those times I'm hoping they're wrong!

[Gina]

Not actually raining this morning though overcast and damp.  Been out searching for that front lens element but nothing!  Even searched the pond, though I guess my hand moving the water might move the lens away from my hand.  I could only search for a couple of minutes as the water was very cold.

The reason for bothering to search is that I think there's a small chance that the lens element may be undamaged - just popped out as the damage to the lens casing barely reaches where the lens element was.

Edited March 1, 2019 by Gina

[Gina]

Back to the "Economy" version...  I have found RPi GPIO lines for PWM0 and PWM1 which I assume will drive two small server motors using a 1K resistor to protect the RPi.  Then I went on to see if I could find out how to drive servos via PWM with INDI and drew a blank.  I'm sure this is quite simple but Google couldn't find it.  @RadekK maybe you have the answer as an INDI expert, please.  Now I'll go back to the WiFi problem...

[Gina]

Since I'm currently stymied with the WiFi problem, I've connected by cable, set everything up with KStars etc., focused the image and put the bare camera plus lens rig up on the pole outside the living room window, hung on the house guttering (yes, it is secure!).  Lots of clear blue sky ATM.

[davidowenrogers]

Hello Gina,

I built an ASC using the 120MC and one of these Arecont Vision lenses

ARMPL155

1

CS-Mount 1.55mm Fixed Focal Megapixel Lens

Purchased from B&H Photo.

The dome has been the tricky bit as the slightest imperfection ruins the effect.

My neighbour was also very unhappy that I'd put a camera near his property. Less so once he saw the video.

 

 

 

Edited March 1, 2019 by davidowenrogers

[Gina]

Nice video ?

 

Edited March 1, 2019 by Gina

[davidowenrogers]

It's a large file!