An All Sky lens question.....

[swag72]

Looking into making my own All Sky camera - Bern at MA has two 180 degree lens'. One is a 1/3" CS mount and the other is a 1/2" CS mount - I'd rather prefer the second one, but I want to use a ZWO ASI120MM camera (or similar) for the All Sky camera. Can I use the 1/2" with the ZWO ASI120MM? If not - Can anyone point me to a suitable camera that i can use it with? Preferably not a QHY5 as I'd like something with a flatter base and less cylindrical.

[Macavity]

As a "lateral" thought, do you want it to provide images or just to monitor?
If the latter, there are also e.g. VIDEO cameras for a computerless system.

[swag72]

3 minutes ago, Macavity said:

As a "lateral" thought, do you want it to provide images or just to monitor?
If the latter, there are also e.g. VIDEO cameras for a computerless system.

I just want to monitor - But have good images to do so! I currently have a Malincam, but the lens is not a 180 degree one and also I have to use a converter to get from the AV output to USB and it is causing my PC's issues -(every one..... so I assume it's the converter) The pictures on the Malincam as well are OK, but I would like better.

[RayD]

As you know the fitting on the 120mm is T2, so you would need an adaptor, and as the sensor is quite close to the front I think this will need to be a very shallow one.

This is one I made in an old CCTV camera housing, and you can see how close the lens is to the camera base.  I'm not sure if the stock lens, which I used and works really well, can be unscrewed enabling that adaptor to be used?

120mm makes a great ASC, really pleased with mine.

[swag72]

4 minutes ago, RayD said:

As you know the fitting on the 120mm is T2, so you would need an adaptor, and as the sensor is quite close to the front I think this will need to be a very shallow one.

This is one I made in an old CCTV camera housing, and you can see how close the lens is to the camera base.  I'm not sure if the stock lens, which I used and works really well, can be unscrewed enabling that adaptor to be used?

 

I thought that I read that the ZWO ASI120 was a CS mount or something? 

This CS lens is supposed to fit it? 

That's me totally confused then - Looks like a purchase is more in order then if I can't even get this bit right 

[RayD]

7 minutes ago, swag72 said:

I thought that I read that the ZWO ASI120 was a C mount or something? 

Yes sorry not well explained.  I've just tried and the stock lens just unscrews from the T2 adaptor so yes a CS mount lens is fine.

[RayD]

Below pics show the camera body in red with the T2 connection, and then with the lens removed which leaves the adaptor in place with the CS connection.

 

[swag72]

OK so either lens will fit ........... So can anyone say what the difference is? Is one for a different sensor?

[RayD]

21 minutes ago, swag72 said:

OK so either lens will fit ........... So can anyone say what the difference is? Is one for a different sensor?

Just that.  Here's some useful info explaining the difference.

[RayD]

I think if you go for the bigger one it just gives you more scope for using it on other cameras if you choose, such as a Lodestar.

[Gina]

If you want to cover the whole sky you'll want a very short focal length lens (eg. 1.2mm) and a fairly large image sensor.

[RayD]

The SX Oculus is 1.55mm @ 180 degrees, but that uses an Ultrastar camera.  Not sure what size sensor that is.  I have the 150 degree (2.5mm) and it's great for me, with views starting at just about roof height on the surrounding bungalows.

[Gina]

Ah yes, it's so much easier if you don't want 180 degrees all round.

[RayD]

3 minutes ago, Gina said:

Ah yes, it's so much easier if you don't want 180 degrees all round.

Yes I did speak with Terry at SX, and he said by far the most popular version is the 150 degree if using it just to monitor sky conditions, so I went with that.

[swag72]

That second lens link is 1.55mm..... so that should work fine with one of the ZWO offerings?

[RayD]

Either one will work as the 120mm is a 1/3" sensor. 

[RayD]

As Gina notes, with the fairly small sensor on the 120mm you may not get the full 180 degrees, but it will still be pretty wide.  The Ultrastar used in the Oculus has a pretty big sensor by comparison (almost twice the size) so the overall coverage is excellent and comfortably displays the full 180 degrees @1.55mm.

Edit:  Out of the two I would have thought the first one (1.25mm) will work better for you using a 120mm as it is for a 1/3" sensor camera, so will most likely offer a wider FOV.

I've not tried a 180 degree lens with the 120MM but someone else may have to offer advice on the expected FOV.

[swag72]

3 hours ago, RayD said:

As Gina notes, with the fairly small sensor on the 120mm you may not get the full 180 degrees, but it will still be pretty wide.  The Ultrastar used in the Oculus has a pretty big sensor by comparison (almost twice the size) so the overall coverage is excellent and comfortably displays the full 180 degrees @1.55mm.

Edit:  Out of the two I would have thought the first one (1.25mm) will work better for you using a 120mm as it is for a 1/3" sensor camera, so will most likely offer a wider FOV.

I've not tried a 180 degree lens with the 120MM but someone else may have to offer advice on the expected FOV.

Thanks Ray - Hopefully someone building their own All Sky may have some insight of the sensors and these lens'

[RayD]

4 minutes ago, swag72 said:

Thanks Ray - Hopefully someone building their own All Sky may have some insight of the sensors and these lens'

Yes hopefully.  Theory is fine, but nothing like seeing it in practice.

The first one at 1.25mm is matched better to the ASI sensor for sure (from memory I think it actually uses the same 1/3" sensor as the QHY).  The second one will need the bigger sensor to give the bigger FOV.