Guiding with Binning option 2x2

[Guest]

Hi all,

I have bought a new guide camera, which has the same chip as the Loadstar, I have read that it works best binned 2x2, the pixel size of the camera is approx 8.4 microns square, so am I right in thinking that by binning the pixel size becomes 16.8 microns square??

If so won't that throw out my current imaging and guiding as currently I guide at 3.5 are seconds per pixel and image at 1 arc second per pixel so this is ok, and inside the 4 to 1 rule, but with the binning mode I will be guiding much more arc seconds per pixel.

I have PHD set at 0.15 pixel movement before a guide command is sent, so by the time it has moved 0.15 of the new pixel size it will have moved about 4 pixels on my imaging camera and will get elongated stars

Hope that makes sense to some expert out there

Olly

[glappkaeft]

Hi all,

I have bought a new guide camera, which has the same chip as the Loadstar, I have read that it works best binned 2x2, the pixel size of the camera is approx 8.4 microns square, so am I right in thinking that by binning the pixel size becomes 16.8 microns square??

True on both accounts.

If so won't that throw out my current imaging and guiding as currently I guide at 3.5 are seconds per pixel and image at 1 arc second per pixel so this is ok, and inside the 4 to 1 rule, but with the binning mode I will be guiding much more arc seconds per pixel.

Yes it will. You'll be guiding at 8.8 arcsec/px if you bin 2x2. I have no idea how well the 4 to 1 rule works but even at 1x1 you will be guiding with 4.4 arcsec/px.

[Guest]

True on both accounts.Yes it will. You'll be guiding at 8.8 arcsec/px if you bin 2x2. I have no idea how well the 4 to 1 rule works but even at 1x1 you will be guiding with 4.4 arcsec/px.

So is that not good then?

Problem is I am imaging with a canon DSLR with 5.7 micron pixels on an SCT with reducer @ 1260mm focal length

And guiding with an ST80 400mm focal length and a guide camera with 8.4 micron pixels

So if my maths is correct

5.7 x 206 / 1260 = 0.93 arcsec/px. Imaging

8.4 x 206 / 400 = 4.32 arcsec/px. Guiding

And binned 2x2

16.8 x 206 / 400 = 8.65 arcsec/px. Guiding

So do I need a guide camera with much smaller pixels then?

Is that the answer for my set up

Olly

[glappkaeft]

Doubt it it work well at 2x2 but it might work at 1x1. This is the kind of thing that needs to be tested since it depends on so many variables with software settings and the mechanics of the mount. While I regularly use a Lodestar I have no experience with your mount. I'm also no PHD expert, except a short period around 2011 I have never used it myself.

[Guest]

Doubt it it work well at 2x2 but it might work at 1x1. This is the kind of thing that needs to be tested since it depends on so many variables with software settings and the mechanics of the mount. While I regularly use a Lodestar I have no experience with your mount. I'm also no PHD expert, except a short period around 2011 I have never used it myself.

So do,you bin your loadstar or not, as I was told it was better to do so because they are interlaced chips so the binning helps with the short exposures needed for guiding

Olly

[glappkaeft]

Yes, we do bin 2x2. We pretty much need to bin 2x2 (+ a 0.5x focal reducer for the Lodestar) since we use an off axis guider with an 3.6 meter focal length 16" RC and image using 1 arcsec/px. However the Lodestar still works at 1x1 and some time ago we ran it at 1x1 for a while since the computer tended to crash if we didn't for some reason (IIRC the problem disappeared after a we reinstalled everything).