Diffraction Spike Focusing with DSI

[Marko of Oz (Mark)]

Found a good, simple read by Mark Sibole on making and using a focusing aid. Although the discussion centers around the Meade DSI line of cameras and their software, Envisage, I think it would apply to other situations also. Here is the Link

This is pretty much a simple Hartman Mask I think, but hey, simple is good right?

I haven't tried it yet but I made up my diffraction spike mask last night since it was cloudy, again.... I improvised the materials and just used the side of a cardboard box and with the assistance of a compass, ruler, set square, electrical tape and a sharp knife. See picture.

[Zenton (Rodney)]

Hi,

How did the mask go. Did you get good diffraction spikes. I have been using a mask that has 3 equally spaced triangles. I only get small diffraction spikes but used the merging of the 3 images for the main focusing. I was wondering if cross design was better.

[iceman (Mike)]

Paul wrote an article a few years ago now, about Creating a Hartman Mask.

I used to use one for planetary imaging but now find that I can get the best results by focusing on a moon (if available). I also find it much easier to get focus right at fast frame rates (eg: 30fps) so a brightish object is needed.

[Marko of Oz (Mark)]

Get nice spikes with bright stars, alas that doesn't really help me without Goto. I can get good focus on a nice bright star but then trying to line up a dimmer dso with just the finder scope is to much of a hair pulling experience.