ASI178MM + long focal -> guiding?

oldskyeyes

Hi,

They do have an ST4 port so can they be used for guiding?

If you are binning the ASI178MM could it also be used as OAG camera on f/7 C11

Would 3x3 (3*2.4=7.2µm) binning work?

This way I could give it a dual use.

Thanks

riklaunim

You can bin2 for guiding (2x SNR, not 4x though) but likely even at bin1 it should easily capture stars due to very low read noise. Bin3 is not available.

oldskyeyes

Two thing:

1) Why can't it bin 3x3 or 4x4 it is done in software just like the 2x2 so what's the problem?

(I assume the laptop gets a 1x1 14bit over USB and the laptop makes it 2x2? although even in firmware I don't see the problem)

2) I think guiding with 1x1 is very optimistic, on an other forum someone said it didn't work, he didn't try 2x2 though.

riklaunim

Ah, depends on app. Like FireCapture can't do more than bin2.

I'm using ASI120MM for guiding and with a finder-guide-scope it has a lot of guide stars to pick from. If it was an OAG it would be way way harder.

oldskyeyes

So for OAG a C11 with USB3 camera which sensor do you think is the best choice.

Does the size of the sensor matter for OAG? (does it only project a bit in the center?)

riklaunim

OAG can take a big advantage of bigger sensor as it's harder to get a star in the OAG field of view.

firstc8

OldSkyEyes wrote:
So for OAG a C11 with USB3 camera which sensor do you think is the best choice.

Does the size of the sensor matter for OAG? (does it only project a bit in the center?)

At such long FL, OAG will be very helpful. Get the most sensitive, lowest noise mono camera you can buy.

I have been using ASI224MC with good results, but only because I happen to have one around. You should be able to find a dedicated guide cam that is ideal for OAG.

I use C8 at prime focus (my Celestron OAG is designed for use at prime focus only), have only been working with M1 so far. Yes can only find no more than three guide stars at any given time, but the good part is you only need one star to guide.

There is no question OAG guide accuracy beats a guidescope by a mile, of course we are talking about SCT at long FL.

oldskyeyes

That's a good reference with your C8.

This max. 3 guide stars was this with f/10 or f/7?

You do use a color version so I don't know yet with which factor I can increase the sensitivity but I guess it would be at least 1 magnitude more sensitive (based on the spectrum filter) . Which should results result in 3x extra stars, or about 3+9 guiding stars)

firstc8

OldSkyEyes wrote:
That's a good reference with your C8.

This max. 3 guide stars was this with f/10 or f/7?

You do use a color version so I don't know yet with which factor I can increase the sensitivity but I guess it would be at least 1 magnitude more sensitive (based on the spectrum filter) . Which should results result in 3x extra stars, or about 3+9 guiding stars)

Prime focus F10. At your F7 with C11 my guess is it is equivalent to my C8 at F10.

Hopefully you don't use the Celestron OAG, it is designed for F10. With the reducer the light circle is smaller, you need an OAG that can extend the prism in further.

Depending on your mount quality, my AVX mount is the lowest budget goto mount out there, it requires 0.5s or less exposure in PHD to handle the bad periodic error. Seeing condition must be good enough to do 0.5s or less. If seeing is not good enough to support short exposure, I probably won't image with C8 at F10 anyway.

With a better mount exposure time should be able to increase. The longer exposure, the more stable your guide stars.

Sam@ZWO

our newest ASCOM driver support 3x3bin and 4x4bin of ASI178

so you can use the ASCOM driver for guiding

oldskyeyes

Sam wrote:
our newest ASCOM driver support 3x3bin and 4x4bin of ASI178

so you can use the ASCOM driver for guiding

The internal ADC is 14bit correct?

So is that enough for 4x4 (16 or 4 bit), since it is software binning the step size is important otherwise the information you want to get is more or less rounded away during ADC?

Do you have test data?