Best place to get a Sony A7s modded

[Max N]

I have a Sony A7s, and have been thinking about getting it modded to increase Ha sensitivity. Where would be the best place to get this done? I'm in the UK.

I believe the recommended mod for astro is to just remove the first filter and leave the second in place? Do I need a replacement filter?

Thanks

[davew]

I've not had the mod done myself but have seen a couple. Put a 50mm f1.8 lens on and you can see nebulosity in Cygnus live !

My first port of call would be - http://cheapastrophotography.vpweb.co.uk/default.html  He doesn't mention the Sony but it's worth a try.

My second would be - http://www.jtwastronomy.com/products/modified_sony_a7s.html  I assume they will do customer cameras but they only mention new as far as I can see.

The mod for this camera seems to be just the OWB / low pass filter removal and chip adjust. I haven't heard of any replacement glass mods.

Dave.

[Max N]

Thanks Dave, I'll check them out. The main reason for getting the mod done would be to try narrowband. I may just try narrowband without the mod first and see how I get on.

[davew]

I can see where you're coming from.

One of the imagers who gets the most out of this camera is Mark Shelley so take a look here - http://www.markshelley.co.uk/Astronomy/

He modded it within days of buying it ! He has also identified a few problems but which camera doesn't have problems ?

I'm assuming you've read this before from Ian Norman but in case you haven't - https://www.lonelyspeck.com/category/gear/

Good luck,

Dave.

[Max N]

I agree, Mark Shelley's work on this camera has been epic and very helpful. I've been using the Sony for a few years, but I don't get the chance to get the 'scope out as often as I would like.

My images have never been affected by any of the issues Mark has identified, but I am imaging at 2032 F/L so stars are probably too big to trigger the star-eater. Plus my firmware has not been updated, so I can avoid it by using 30s subs. Another reason I don't see any of the issues may be that my processing techniques are less advanced than his. I do plan to start using his other work-arounds (higher ISO to get the histogram more central) since it can't do any harm.

Cheers

Max

[ronin]

13 hours ago, Max N said:

Thanks Dave, I'll check them out. The main reason for getting the mod done would be to try narrowband. I may just try narrowband without the mod first and see how I get on.

For narrowband would you not also need to have the bayer mask removed in order to make it mono and use all the pixels ? That would also mean unusable for "normal" photography. Narrow band implies a mono camera, otherwise the extra Ha that lands on a Green or Blue pixel is lost and generally half are Green and a quarter are Blue, so 3/4 of the pixels could be unusued.

Thoughts were that by the time you got the filter removed and then if you had the bayer mask removed  the cost would be getting to around a ZWO camera that is designed for the purpose. And if you use it for such you would still have the A7 for normal photography.

Try narrowband with an OIII filter and see how much of the chip is used, but I would expect a very "course" result in terms of resolution.

[Max N]

Hi Ronin, I get what you're saying, but actually people are getting some nice results using the A7s with narrowband filters, without having the Bayer removed. Also, people often forget to factor in that the Sony has a full-frame sensor. I just had a look at the ZWO ASI 1600MM-PRO which is £1288 at FLO. The sensor is roughly 1/4 the size of the A7s, and I'm imaging with an Edge 8 HD which fully illuminates the Sony. If I used the ZWO, because of the smaller sensor, only 1/4 of the photons would even hit the sensor compared to the Sony! OIII is green I think, so I'd actually capture twice as many OIII photons with the Sony with the Bayer in place as with the monochrome ZWO, because of the 4/3 sensor on the ZWO. If you factor in the increased sensitivity (lower noise at high ISO) of the Sony, I think it wins out. Plus I can frame bigger targets with the Sony, whereas with the ZWO I'd only be able to frame 1/4 of the field that I can with the Sony. At 2032mm f/l, the Sony allows me to frame a lot of targets that just wouldn't work with the ZWO.

I know that a lot of people do image with the Edge 8 with smaller sensors, but I can't see the point of paying for 8" of aperture and well-corrected optics, then throwing away 3/4 of the photons by using a 4/3 sensor? So if I was going to buy a monochrome sensor it would have to be full-frame, but how expensive? Atik 11000 is £5K! So I think the Sony with the Bayer removed would actually be comparable with the Atik 11000, which makes it more attractive. But I don't know if its possible to de-Bayer the sensor in the A7s....

I agree that the effective resolution would be lower with the Sony, but even if I drop down from 12 MP to 3 MP, the image would fill my 27" iMac screen at 1:1. I think that seeing will be more of a limit than the resolution?

 

[Max N]

Just reviving this topic as I have managed to save up the funds to get the camera converted, but I need a bit of advice before I proceed.

I have found several places in the UK which offer to convert the A7s, but they all specialise in infrared photography rather than astro. They generally offer a choice of full spectrum modification with the sony UV/IR filter removed and not replaced, or the fitting of a replacement filter.

So what I need to know is, what are the pros & cons of leaving the sensor 'naked' (vs fitting a replacement filter)?

• Will the sensor be more vulnerable to scratching etc?
• Will I have issues focussing at infinity with camera lenses?

If I go for a replacement filer, what glass is recommended, and where can the glass be sourced?

One of the companies offers B270 glass as a replacement. B270 has a nice linear transmittance curve with a bit of UV cut, so looks a good choice, except that its broadband transmittance is about 92%, so I'll be 'losing' 8% of the photons, which seems a shame. Is there a better alternative? Here is the curve for B270...

Here is a link to a global list of such companies in case it is useful to anybody...

https://robertreiser.photography/infrared-camera-conversion-service/

[Max N]

Oops, the B270 curve disappeared, let's see if this works