Grading seeing without a DIMM? - Forums

Topic starter

Frequent contributor

6 days ago

Is there a way to quantify see without using a DIMM? I’m thinking of something like measuring the FWHM with a short stack of very short exposures (500ms) or somehow using the data that PHD2 generates. I’m really not looking for an absolute measurement as you would get with a DIMM but just a general record of conditions from night to night.

Well Written Engaging

Dave Erickson

6 days ago · Edited: 6 days ago

There are several other methods. One i have used for years is a SBIG, now Diffraction Limited, Seeing monitor. It uses a small telescope pointed at polaris. With a camera operating in TDI mode. The FWHM of the star is resorded and seeing is calcuated then graphed at a selected interval. While not 100% as accurate as a DMM system it does provide a reliable relative measure of seeing conditions...Dave

An old graph from my website, taken during my site survey...

Helpful

Tony Gondola

Topic starter

Frequent contributor

6 days ago

That’s a great way to do it but it’s a much too expensive a solution for me. That said, it seems to be a good approach and it would be fairly easy to DIY. I wonder if something like SharpCap’s seeing monitor might be a good solution on the software end?

Dave Erickson

6 days ago · Edited: 6 days ago

Tony Gondola:
That’s a great way to do it but it’s a much too expensive a solution for me. That said, it seems to be a good approach and it would be fairly easy to DIY. I wonder if something like SharpCap’s seeing monitor might be a good solution on the software end?

I picked both of mine up used on Astromart for a good price, if you can get or write the software its an easy DYI project. Below is an image of one made from non functional parts purchased on Astromart. I added an SQM meter under the seeing telescpe...

I had it on the dome last year but pulled it off due to fires that threatened the facility...

Image of the completed Seeing SQM system ready to mount...