can i use my old manual M42 secrew lenses on Sony A77 or A99?

I can't be certain, but I suspect you'd get Aperture Priority and Manual metering when stopped down - that's certainly what happens with Canon and Pentax (although not Nikon).

You should ask Sony, though. Some Sony models have a, 'Shoot without lens,' option (the camera can't see an M42 lens because there are no on-board electronics) which has to be used.

It looks like there is an adapter available.

http://www.bhphotovideo.com/c/product/774454-REG/D...

The old M42 screw thread is pretty narrow, so it is not technically difficult to make an adapter that fits within the DSLR camera bodies' mounts.

There would be no electronic interaction, so you would use manual exposure mode to set your speed, the aperture ring on the lens to set the aperture, and manual focus. There is no metering, so you could start with the sunny 16 rule, and do some trial and error bracketing from there.

If you can an M42 to Sony/Minolta adapter then maybe you can use the old lenses with the camera in manual mode. I'm not sure if the lightmeter will work too. There's a chance you will be left to your own.

If I can use my old Tamron 500mm mirror lens with a T mount then you can do the same with any lens with an adaptor. It will only work in Aperture Priority or Manual and there is no AF. Focus Peaking helps with the focus.

Sometimes it works quite nicely.

http://www.pbase.com/johnfr/image/149067403

Sony A77 Manual

that is an interesting question and I hope you will find some valuable answers

Yes it might be correct