old Televue 2.5x barlow

[dhkaiser]

I have a 20yr old Televue 2.5x barlow and am wondering if it is suitable for imaging with my Lunt 60mm and ASI 178?

[marktownley]

Hi Dan.

The 178 has 2.4um pixels, that's more suited to f10, so, I would say is not ideal. That doesn't mean you can't try, but because of the long focal ratio you will be using you will be oversampling. Exposure time will be longer, contrast lower and signal to noise ratio worse, you won't get increased resolution out of the system just increased image size. Can you do 2x2 binning with the 178, that would put you in the right ball park...

Mark

[PDB]

Mark,

don't you mean oversampling? The signal in this case is spread over more pixels.

Yes the 178 can perfectly bin 2x2 (even 3x3 and 4x4). It is a software bin in the driver (there is a possibilty of sort of hardware bin but somewhere I read it is not advised to use that. CMOS do no really bin like CCD cameras). The "binning" can also be done by resampling in post, woul probably be similar, but since the driver seems to add the signal of the pixels, the cam needs shorter exposures in bin 2x2. Can be good for H-Alfa.

Paul

[marktownley]

Mark,

don't you mean oversampling? The signal in this case is spread over more pixels.

Paul

I do, you're right Paul, that was me typing too quick first thing in the morning

Corrected now!

[dhkaiser]

Thanks Paul and Mark. I believe I can 2x2 bin in Firecapture, I'll give it a try.

[PDB]

Yes can be done. Now I remember what was the problem with hardware bin. It is done on chip, but then the ADC will be set in 12bit mode instead of 14bit.

Regards,

Paul