Concave lens on the front

[Nate]

I have a question that shows google is not all knowing, and thought I'd ask here.

I purchased a Sionyx Aurora Pro Night Vision Camera and it's performing pretty well for my Satellite watching needs(videos on Youtube don't show it justice). The focus stop for infinity I believe stops before the actual sharpest point. 

 

When I place the rear element of the EL Nikkor 80mm or a too short focal distance concave lens (90mm, too short to use alone) with a same size convex on the front, it acts like near sited corrector glasses for a person. Near sited sighted corrector glasses increase the focal length in the eye.

 

So now, with the lens or lenses on the front of the Aurora, I have close focus and past infinity focus. This should work right? Or am I just focusing an almost infinity object in and out of focus.

 

Sorry if I lost anyone reading this, it's just hard to tell with that camera because it outputs only 1280x720 pics or video, and the digital zoom doesn't help much, and the stock lens is wider than eye site. Here's a video I made of a very dim Starlink pass with the stock camera, It's quite busy up there. Thanks for any help. 

 

[Nate]

I made a comparison video showing the lens on the front goes past infinity focus and back, but it really doesn't look any sharper. It might be the high cropped in videos with a lower resolution sensor with huge pixels and a wide angle lens.

Maybe it reaches infinity focus stock and I just see it with the low resolution of being cropped.

 

 

[Andrea B.]

There are really a LOT of satellites up there. That was a fascinating video!

*****

 

I'm not quite sure of your question. You are placing an extra convex element in front of your Aurora Pro in order in order to attain focus past the Aurora's infinity stop (which stops too soon). And you want to know if that is going to help the focus problem at infinity? 

 

Did I get it right? If not, let's try again. 

 

Before directing this question to Birna or Stefano or Enrico or anyone else who might answer it, I was wondering if perhaps your particular Aurora Pro might simply be off in some way and you might need to exchange it? Sometimes we get a copy of a lens which not quite within the proper specifications. An element can be decentered or whatnot. 

 

1280x720 should be enough to get sharp, in-focus videos or photos. OTOH, I know nothing at all about night vision optics!

 

 

 

[Andy Perrin]

If the circle of confusion (when focussed at infinity) is already smaller than a pixel, you can’t make it sharper by focussing it better because the pixel size is the limiting factor. I’m confused about whether that is the case here or not though. 

[Nate]

11 hours ago, Andrea B. said:

You are placing an extra convex element in front of your Aurora Pro in order in order to attain focus past the Aurora's infinity stop (which stops too soon).

It's actually just a concave(-400mm FL) new lenses to test showed up. Yes I wanted to see if just putting it on the front corrects it not reaching infinity.

I think @Andy Perrin might be right though, looking at all the stock footage on youtube of other peoples sky, all their stars look out of focus too, but might just be it can't get pinpoint dots of light.

I did put a 7x42mm monocular on the front, and magnification made the focus better, but the less light gathering and the coma on the edges made it un usable to me.

 

What's interesting though, I put a 37mm concave(-90mm FL) on the front of my Focotar 50mm that before for sure didn't reach infinity on a helicoid on my mirrored cameras did now with the concave on the front, making me believe it works now.

 

I believe getting a different unit would yield the same results for the Sionyx. So in the future I'll probably do a lens mod so I can interchange lenses. The fear of flat ribbon cables is holding me back atm.

 

[Andrea B.]

Also, it’s infrared light at night, so diffraction begins at wider apertures than it does for visible light. Probably a combination of factors -small sensor, longer wavelengths? And then the camera is trying to see through a *LOT* of atmosphere.

[lonesome_dave]

I've had one of these cameras for a while now.

I have to agree with everyone that it is mainly an issue of a really low resolution sensor (< 1 Megapixel). My night videos don't look any sharper but I don't think focus is the problem. According to Sionyx the sensor in this camera has extra-large pixels to gather more light and I think that may further complicate image sharpness.

 

Nate, I too have seen the videos on taking the Sionyx apart to reveal a removable C-mount lens and haven't been willing to go that far. If you haven't already though you should consider removing the front lens protector to gain access to the existing lens which sports a 30.5MM filter thread that enables a few more options. You need to twist while pressing inward until the cover clicks over, then pry it off with your fingernails. It can be put back on. (I hope.)

 

Aside from the NV capabilities that camera has superb IR sensitivity. I'll do a post on that before too long.

[Nate]

@lonesome_daveSo far all I've done is take off the front clear cover and bought some 3D printed upgrades. The lens hood has a 37mm thread that I've been putting the RM100 on for some daytime use.

I  appreciate your thoughts on the sensor and image sharpness and believe it to be correct. I use mine with a 940nm torch and can see a couple hundred yards easily.

Here's the upgrades, I think they're valuable for the units https://www.ebay.com/itm/324584042693?var=513773318339 and the IR torch holder

https://www.etsy.com/listing/911659166/irtalon-illuminator-mount-for-sioynx 

 

[Nate]

I agree @Andrea B.I think the unit would perform better with the option to change the front lens if needed. I'm discovering for what it is, it's pretty cool. I can use this if I don't want to use my helmet mounted one.

[lonesome_dave]

Yeah the Sionyx camera is cool for what it was designed for. I don't think it's worth tearing it apart to put on a better lens. The low pixel count and large pixel size will always limit the image quality by way of what Andy said.