Hartman Masks Compared

[darrellx]

Hi All

I finally decided to do something about the focusing issue with my two scopes. A fair amount of the time, I am able to jag a reasonable focus, but it annoys me when I take a series of pics then realise after I download them to my laptop that they are out of focus. So I have made some Hartman Masks and thought I would share with you my experience.

I have two scopes - a 200mm Skywatcher reflector and a 90mm Megrez.

Having read what I could about Hartman and Bartinov Masks, I decided to go for the Hartman since it seemed easier to make. All up, I made 4. 2 for the 200mm and 2 for the 90mm. I made 2 for each to compare one with the round holes and one with the triangular holes.

Given the lousy weather on the Gold Coast for the last 2 weeks, tonight was my first chance to try them.

I am rather impressed on how they worked. Exactly as the articles said.
I did find it marginally easier to use them on the 200mm. The view was noticable brighter compared to the view in the 90mm. No surprise there I suppose.

On the issue of the round holes and the triangular holes I could see no difference. In this regard both worked exactly the same.

All up, it was well worth the few hours to make them.

Darrell

[RobF]

Thanks for the report Darrell. I'd hummed and harred about making a Bhatinov, but reckon a Hartman probably more in line with my meager skills

:P

[StardaddyEd]

I have tried both the Hartman mask and the B-mask. There is no comparison between the two. While the H-mask is easier to make the b-mask is MUCH easier to get an exact focus. It is also independent of seeing so it is much easier to use.

My advice is to take the time to make the B-mask and you will be much happier in the long run!

Ed

[bloodhound31]

I agree, I have made and used both. The Hartmans I made at home are simple and effective.

The Bahtinov I photocopied onto a clear transparency to trial it, then a local Laser Cutter to make in metal.

The Bahtinov is BY FAR, much more precise and so fast!:thumbsup:

Baz.

[Geoff45]

Bahtinov wins every time. I printed my original on a sheet of paper, glued it to a thicker bit of cardboard, then cut it out with a ruler and stanley knife--pretty low skill level required. I have now ordered a metal one. You just send the file to a laser cutting firm and pay the money.
The triangular hole hartmann is better than the round hole one, since you get to see good diffraction spikes in focus, but still not as good as the bahtinov.