ZWO ASI 120 guiding camera

[hjw]

Hi all,

I just had an unexpected income of 450$ and thought that now is as good a time as any to invest in some guiding gear. I have ordered the SW 80mm f/5 guide scope and have settled on the camera from the title. Here is my question: I know from reading B/W is better but by how much? If I can get the color version to guide almost as good I could give planetary imaging a try. I am not serious enough with it to warrant the B/W camera AND filters. Deep down I know I should go mono but I am looking for some conformation.

Thanks

HJ

[rwg]

Hi HJ,

in my opinion the difference between the mono and colour versions for guiding will be so tiny as to be almost nothing. I would suggest getting the USB3 capable 120MC-S version if you can afford the extra, even if you don't have a PC with USB3 ports. I find that with one of my laptops the 120MC can only manage about 20fps without getting dropped frames while the 120MC-S manages 30 quite happily (this is on USB 2 ports). On another PC both work fine, so it is just something about particular USB controllers - some work better than others... Anyway, if it's only a little extra I would advise the MC-S version.

cheers,

Robin

[glowingturnip]

i've guided with the colour ASI (and the colour QHY) with no problems at all

[hjw]

Thanks Robin,

The news that there is not much difference between color and mono is great. But now I have the next question: what do I need the high frame rate for? The "movie" is chopped up into individual frames anyway for stacking. What is the advantage of 30fps over 20fps if 1 minute exposure at 20 fps gives me already 1000+ frames? How may fps would I need for guiding anyway - I always thought it was a 1 per second.

One answer to my post and I understand how little I know ... Alas!

Thanks

HJ

[rwg]

For guiding you only really need about 1 frame per second... But you did mention planetary imaging too, where a decent frame rate is a great help - you want to keep the exposures short to freeze atmospheric turbulence and gather lots of frames so you can afford to throw away the poor ones.

cheers,

Robin

[hjw]

For guiding you only really need about 1 frame per second... But you did mention planetary imaging too, where a decent frame rate is a great help - you want to keep the exposures short to freeze atmospheric turbulence and gather lots of frames so you can afford to throw away the poor ones.

cheers,

Robin

Thanks again!

OK, I've come from a 120MM to a 120MC-S. I see your point of getting as much frames as possible (and I do have a laptop with USB3 so I could potentially get 60FPS). So please indulge my curiosity one more time and I promise I will shut up... The difference in FPS between the 120MC and the 120MC-S is the transfer rate between the camera and the computer (I think) but the actual exposure time would be governed by the brightness of the object and by the optical train and would be the same for both cameras. Is this line of thought correct?

Cheers

HJ

[rwg]

Yes, absolutely right - if you set an exposure of 30ms to expose (say) Saturn correctly, then you will not get more than about 30fps. If you set 20ms for Jupiter then you might get up to 50fps on USB3, etc.

cheers,

Robin

[hjw]

Thanks Robin and Stuart,

as usual, I am glad I asked here first before proceeding with the purchase. And now I will have to wait for the clouds to clear. We haven't had a starry night in Melbourne for 4 weeks!

Cheers

HJ