All sky lens

[gentlebear76]

Hi all,

As many others I'm also building an all sky camera - I'm very original ? I'm using a ZWO ASI178MM as my camera with a Fujinon fish eye  1:1.8/1.4mm lens which is more or less the same as most others are using. I am, however, a bit annoyed with the large amount of "dead space" in the image, as the lens only gives me an image that covers only about half the sensor space. I guess that is limited by the lens and its specs so I'm wondering if someone can recommend a differenc lens that covers more of the sensor, but still offers the same sensitivity as the Fujinon. I don't mind loosing some of the sky on the vertical part of the image if I can get more horizontally - I'm greedy ?  Any suggestions?

Clear skies,

Michael

[Dr_Ju_ju]

Have you tried it outside & how much Sky is then visible & cut off by the surrounding houses\vegetation etc ??

[gentlebear76]

I have tried it outside (had to dig a bit to find an image :-) ) and quite a bit of outer part of the actual image is whatever is on the horizon so I loose a lot there as well. I'm planning to move it up higher, so I'll get less/none of the lights but still. 

Michael

[Gina]

Is north at the top?  Having it higher up will help get less of the house roof in the image and more of the sky.  I see from your image that you could certainly do with either a bigger coverage by the lens or alternatively, less coverage by the camera sensor.  I was using an ASI178MM but changed to an ASI185MC as I wanted colour and I already had the ASI185MC.  The 185 has a smaller sensor but not by much.  Incidentally the 185 series has been replaced by the 385 series with twice the sensitivity.  I don't know of another lens that gives anything like the performance of the Fujinon you and I are using but there are other ZWO astro cameras with smaller image sensors (cheaper too).

[gentlebear76]

North is right., east at the top. If I want I can put it up at the top of the roof towards east. The street is sloping downwards that way so it'll help me get over the height of the street lights. It does, however, mean that I have to dance around on a ladder 6 meters above the ground with a large unbalanced box. I may look at making some sort of pole elsewhere where I can mount it a bit more permanently. We'll see. I hadn't considered the sensor size. I just had a DOH moment ? I can't afford a new camera so I may just have to learn to live with it. Now, if they just made elliptical fish eye lenses ? 

Michael

[Chriske]

I presume all this is done with a camera and a fisheye-lens.
Would it be possible to just use a lens and a sensor connected to a computer(or other) to do exactly the same. In fact my question is do you really need a 'state of the art' camera to make this kind of images..?

[gentlebear76]

I would think any sensor and fish eye lens combination will give you an image similar to this. Of course there is resolution, sensitivity and lens quality to consider as well but I used a QHY5-II and the fish eye lens it came with for similar images for a while. That's a 250€ camera. The above image was taken with a ZWO ASI178MM hooked up to a raspberry pi running software I wrote myself. I havn't tried with a raspberry pi standard camera or a pi noir but I don't see why they shouldn't work. 

[Gina]

The Pi camera may be too small but I'll check.  The Fujinon has a half inch size image.  One thing you can do is use ROI (Range Of Interest) to use less of the sensor but the only benefit is quicker download.  I tried a QHY5-II but found it very noisy.  The ASI178MM has a sensor 7.4mm x 5mm and I reckon something about half the size in each dimension is what would suit.  Just looked up the size of the RPi camera v2 and the sensor size s 3.68 x 2.76 mm so that should be fine.  What I don't know is how sensitive the RPi camera is and what the noise is like.  Worth a try I would say.  The ZWO ASI120MM should be a lot more sensitive than the RPi camera as it's designed for astro use but costs a lot more, of course.  It has a bit larger sensor (3.6mm sensor Y dimension).  The colour version is slightly cheaper.  Colour cameras are less sensitive (as I expect you know).

[Dr_Ju_ju]

If you want to go down the Pi3 route, Design Spark\RS components have released new camera modules (https://uk.rs-online.com/web/p/video-modules/1675922/) with interchangeable lenses including a 220 degree (https://uk.rs-online.com/web/p/video-modules/1633898/)

[Gina]

That would be great for a daytime ASC.  It would also make a good daytime surveillance camera.