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steppenwolf

DIY All Sky Camera

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The ASI185 has image sensor of 7.3mm x 4.6mm - I make that 8.6mm diagonal by Pythagorus.  1/3" = 25.4/3 = 8.47mm so this is a 1/3" sensor.  To get the whole FOV on the sensor means a FOV diameter of <4.6mm which is less the 1/5".

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10 minutes ago, ChrisLX200 said:

Apologies - I just checked my lens and it is indeed 1.25mm f/l

ChrisH

 

Oh, and I think they are f/2 - you're talking mega-bucks for a fast fish-eye.

Well, the ZWO lens that came with the ASI185MC camers says it's 2.5mm FL and f 1.2 - now that's fast! :)

Lens 01.jpg

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I must have one of those lying around somewhere - I recall a lens came with the ASI178MM!

ChrisH

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1 hour ago, steppenwolf said:

The dome must indeed affect the focus but I'm not sure that a flat glass would help even with the 150° as the further away you get from the centre axis, the greater the distance the light will have to pass through the glass.

Better throw away all of my 'optically flat' camera filters then :icon_biggrin:

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Flat glass is fine if the light cone is narrow but as it gets wider the refraction effect increases until this becomes ridiculous approaching 90° off axis :D

Edited by Gina
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Better throw away all of my 'optically flat' camera filters then :icon_biggrin:

I don't think that will be necessary as I think you'll find that the 'light cone' will be rather different between the two scenarios although the principle still applies :icon_biggrin:

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3 hours ago, Gina said:

Flat glass is fine if the light cone is narrow but as it gets wider the refraction effect increases until this becomes ridiculous approaching 90° off axis :D

Actually if you look do the standard coin in a pool experiment, its apparent depth does not change depending on the angle you look at it, so although the angle the light is refracted at increases, it happens consistently with moving the focal point by the same amount whatever the angel of incidence (and yes I did have to google this to check).

You can use real vs apparent depth to work out refractive index, and this would not work if apparent depth changed with the angle you look at.

I have a webcam with a semi-fisheye that has about 120-130 degrees FOV. It happily can see though a 40-cm disc about 5mm in front of the lens without vignetting. Tilting the sheet by up to 45 degrees makes no noticeable effect on the image. I am sure a flat glass plate at an angle of, say 5-10 degrees to allow rain to drain off would work fine.

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Interesting point :)  I wonder if the very thin UV filter from a DSLR sensor could be used as a window for an ASC.  I don't need quite 180° FOV as there's rising ground, trees and house to the NW.  Mind you, the thin acrylic dome I'm presently using seems to have little affect on focus and stars are sharp all over with the lens at the centre of the dome's curvature.  My biggest problem ATM is dodgy USB connection and I want the processor in the box with the camera and lens and I plan to use a Raspberry Pi 3.

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Well, there's an interesting turn of knowledge and proof positive I guess that thought experiments such as those carried out by Galileo need to be backed up by physical experiments! However, correct me if I am wrong but this does not help with the 180° scenario?

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2 hours ago, steppenwolf said:

Well, there's an interesting turn of knowledge and proof positive I guess that thought experiments such as those carried out by Galileo need to be backed up by physical experiments! However, correct me if I am wrong but this does not help with the 180° scenario?

No, I think 150 degrees is probably close to the practical limit. At 180 degreees you would need a sheet of glass of infinite size...

 

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@steppenwolf Steve, Do you have a step by step guide on how to do this and what you used? And lastly would a numpty be able to make it? :D 

Edited by swag72

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On 18/07/2016 at 00:03, Stub Mandrel said:

No, I think 150 degrees is probably close to the practical limit. At 180 degreees you would need a sheet of glass of infinite size...

I get a fraction over 180° from my lens.

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Hi All,

You have all got me thinking about making an all weather camera and over the last few months I have been acquiring various CCTV lenses as below: -

CCTV_Lenses.jpg.b1f27dd6d3e75804a4a513543a16313a.jpg

The lenses are Fujinon Fisheye 1:1.8/1.44mm DF1.4HB-L1, a CCTV Lens 2.1mm 1/3" and a IR CCTV Lens 25mm F1.2 1/3"

Now I wrongly assumed that these would screw into my QHY5 colour camera, but I was wrong.

So my questions are can I buy an adapter so that they wills crew in (I don't have a 3 D printer) and if so which lens would be better.

I had to wait until the Fujinon lens arrived today so that I could determine which clear dome and box to purchase, maybe it might be time to have a play with a Raspberry PI and see how that can control it.

Due to the maximum length of a USB cable I can't run it from the middle of the garden to my study, so will probably be limited to when I am imaging.

Can anyone give me any pointers?

BTW All of you are guilty of spending my money and should come with a Government Health Warning to my sanity and pocket :-)

Edited by Jkulin

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22 hours ago, Gina said:

I get a fraction over 180° from my lens.

I was posting about using a flat sheet for the top of the enclosure instead of a dome. You can't get a 180-degree field of view from a lens behind a flat sheet of glass of finite size, even discounting total internal reflection.

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On 2/13/2018 at 17:54, Jkulin said:

Hi All,

You have all got me thinking about making an all weather camera and over the last few months I have been acquiring various CCTV lenses as below: -

CCTV_Lenses.jpg.b1f27dd6d3e75804a4a513543a16313a.jpg

The lenses are Fujinon Fisheye 1:1.8/1.44mm DF1.4HB-L1, a CCTV Lens 2.1mm 1/3" and a IR CCTV Lens 25mm F1.2 1/3"

Now I wrongly assumed that these would screw into my QHY5 colour camera, but I was wrong.

So my questions are can I buy an adapter so that they wills crew in (I don't have a 3 D printer) and if so which lens would be better.

I had to wait until the Fujinon lens arrived today so that I could determine which clear dome and box to purchase, maybe it might be time to have a play with a Raspberry PI and see how that can control it.

Due to the maximum length of a USB cable I can't run it from the middle of the garden to my study, so will probably be limited to when I am imaging.

Can anyone give me any pointers?

BTW All of you are guilty of spending my money and should come with a Government Health Warning to my sanity and pocket :-)

@Gina, Hope you don't mind my asking Gina but no one seems to have advised and you seem to be the guru with the all sky weather items :-), can I buy a converter so that I can screw one of these lenses onto the front of my QHY5 camera?

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13 hours ago, Jkulin said:

So my questions are can I buy an adapter so that they will screw in

In short, yes.

The Touptek and ZWO cameras I have both came with 1 1/4" to c-mount adaptors

Be careful not to screw in so far the lens hits the sensor and breaks it.

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Just now, Stub Mandrel said:

In short, yes.

The Touptek and ZWO cameras I have both came with 1 1/4" to c-mount adaptors

Be careful not to screw in so far the lens hits the sensor and breaks it.

Thanks for that, so I just need to find 1 1/4" to C Mount adapters?

Have you got any links as not finding the adapters easily, thanks

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I was slightly wrong!

The Touptek is threaded ~31mm and comes with a C/CS adaptor with a window in it.

The ZWO comes with a T-mount to C/CS adaptor.

As far as I can see the QHY5-L comes with an almost identical adaptor to the touptek, also with 'C' on the side. Is this black extension piece missing from your camera?

 

 

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Hi Neil,

Just checked all of the original boxes for my 3 QHY Cameras and none of them came with a converter, I'll give Bernard at Modern Astronomy a call where I bought them from and see what his thoughts are.

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Sorry just posted this on another thread: -

16 minutes ago, Jkulin said:

Thanks everyone for their help, seems like I am eating humble pie again :-(

The parfocal ring was locked in the precise place that the CS adapter joined the camera, so it looked like it ddn't have a join, as soon as I removed the parfocal ring I could see that the adapter was made up in two parts, unscrewed it and the lens screwed on as it should, sorry to have wasted anyone's time.

Walks away with egg all over his face....:-(

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In case anyone wants to know, a 5mm cs adaptor fits, but is not deep enough.

The measured distance to get focus for the zwo 290 and 120 (so probably others too) is nearer 6.4mm.

So a 5mm thick cs mount adaptor is around £3 on ebay but another 1.4mm needs to be found for focus with the Fujinon lens.

Either use washers as spacers or get something made.

I think the adaptors come in 5mm, 10mm, 15mm and 20mm.

https://m.ebay.co.uk/itm/UK-FAST-SHIP-C-CS-Mount-Lens-Adapter-Ring-Extension-Tube-For-CCTV-Camera-5mm/272950505030?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

 

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