NIR Guiding

[NickK]

There's an interesting discussion going on in a different forum. Basically the part I'm relaying here is the use of Near-IR for guiding as it doesn't have so many problems getting through the atmosphere (i.e. less turbulent interference).

The NIR in question is about 700-1000nm wavelengths inline with the blackbody ration of the large number of K type stars.

[pete_l]

Yes, I've seen the company that makes ON-axis guiders. Veeeeery interesting.

It makes me seriously consider buying a flip mirror and replacing the actual mirror with a dichroic one - so the I.R. comes out of one port for guiding and the visual goes through through to the imaging CCD.

I'll just add it to my list of other astro projects .... should get to it in about 2019

[NickK]

I have a mirror flip.. 

I had a look at Thorlabs, the DMSP805 looks like a good part: http://www.thorlabs.de/newgrouppage9.cfm?objectgroup_id=3313

[andrew s]

Yes, I've seen the company that makes ON-axis guiders. Veeeeery interesting.

It makes me seriously consider buying a flip mirror and replacing the actual mirror with a dichroic one - so the I.R. comes out of one port for guiding and the visual goes through through to the imaging CCD.

I'll just add it to my list of other astro projects .... should get to it in about 2019

If you image with the transmitted light you will get distorted images as the dichrocic plate will add aberrations. You should image from the reflected beam.

Regards Andrew

[pyrasanth]

I currently guide with NIR through the back of the beam splitter which is part of the ONAG imaging solution. Since you are guiding in the same field as your target object there is never a lack of guide stars. Nearly all stars radiate in the NIR spectrum and guide cameras are very sensitive to NIR so you get very bright images. The distortion from the beam splitter for the NIR does not matter as packages like PHD don't really care about round stars. I find the guiding through this solution superlative & much easier than an OAG with all its inherent problems. The ONAG is really the very best guiding solution you can currently get when you weigh up the pitfalls of other guiding solutions.