
Revolutionary new way of focusing! No less!
#151
Posted 05 September 2008 - 02:21 PM
I did discover that while a Dremmel will cut through foam board very easily, it's also almost impossible to control.
- Gus
#152
Posted 05 September 2008 - 02:34 PM
Options options. Mostly because it seems the gap size really isn't that important.
#153
Posted 05 September 2008 - 02:38 PM
I did discover that while a Dremmel will cut through foam board very easily, it's also almost impossible to control.
- Gus
A Dremmel is WAY overkill for foam board. I can just picture the foam flying everywhere! The easiest way to cut foam board is with a razor blade. My ex-wife does quilting and for fabric they have a rotary cutter. Basically a circular razor blade you can run along a straight edge. Makes perfectly straight cuts on fabric and foam board. I used hers to make my light box out of foam board. The only tricky part would be the ends of the cuts. Perhaps you could cut it to within an 1/8th of an inch and finish the cut with a utility razor blade.
Lots of great ideas! I may be looking for my next generation using foam board. Hmmmm.
#154
Posted 05 September 2008 - 02:58 PM
I'll let you know how it goes, I have everything set up and ready to go, and my clear sky clock looks perfect!
Jim
#155
Posted 05 September 2008 - 03:01 PM
That way you wouldn't need to make any cuts. Just print it out and tape it to the end of the scope. Would the clear plastic cause any problems?
#156
Posted 05 September 2008 - 03:09 PM
Does anyone think that you can print this out on that clear transparency paper
Back a few pages, I posted that I tried this approach. You can see the spike pattern, but it's distorted a bit. When I added the CCD imager to it, it was unusable. However, I was just hand-holding it. If it's mounted in a rigid frame it may work better. Unless the optical quality of the material is better than what I used, you really need to cut out the clear parts.
#157
Posted 05 September 2008 - 03:21 PM
#158
Posted 05 September 2008 - 03:25 PM
I know all the masks I've made over the years worked best with smooth sharp edges for any of the hole patterns I've tried.
#159
Posted 05 September 2008 - 03:51 PM
As you can see it is a quick and dirty prototype so I’m really pushing the limit on tolerances required to achieve successful focus. I’ll be reporting back on my "first light" results as we are expecting some pretty good local weather this weekend. Seriously though, many thanks to Pavel for the idea, Dennis for the news and Adam for the scalable vector drawing. This has really been a thoughtful thread and I’ve learned a lot from you guys so “thanks†to you as well.
Ron
#160
Posted 05 September 2008 - 04:07 PM

I imagine a frame from foam board would be rigid enough to allow enough tension on the wires to keep them straight.
#161
Posted 05 September 2008 - 07:26 PM
The circular area is 208mm in diameter, slightly larger than my aperture, and the slats / bars are 3mm each (since S is 5-6.7mm for me). The entire thing is made out of foam board in a 9.25" square, since my outside diameter is 9.25". I have some vague plan of gluing tabs on the edges to keep it in place.
I didn't see any point in making a circle to match my central obstruction.

- Gus
#162
Posted 05 September 2008 - 08:08 PM
You could always shoot some black spray paint over it.
#163
Posted 05 September 2008 - 08:23 PM
In retrospect, it might be smarter to reverse that, so the parts to be cut out are black and the remainder is white.

#164
Posted 05 September 2008 - 09:10 PM
I printed it out and laminated it then cut it out.
This was just a test to see how well it would work.
Focus is very easy with it and it worked very very good.
Eventually when it wears out Ill redo it in plastic.
Thanks for starting this topic.
Regards
Mark
#165
Posted 05 September 2008 - 09:10 PM
The refractor template works perfectly, took about 20 seconds to focus! Thanks for the template.
Jim
#166
Posted 05 September 2008 - 09:45 PM
Adam,
The refractor template works perfectly, took about 20 seconds to focus! Thanks for the template.
Jim
AWESOME! Thanks for the feedback Jim. Glad it worked out for you.
#167
Posted 05 September 2008 - 09:53 PM
Ron
#168
Posted 05 September 2008 - 09:56 PM
Ron
#169
Posted 05 September 2008 - 10:10 PM
I just received my two masks from the cutters and they are beautiful! I had come up with the refractor modification after I had placed my order so there was no changing. I had them cut some tabs for me as well which I am in the process of bonding. Here are a couple of pictures.
The little paper mask was my demo to see just how well focusing would turn out as I mentioned in a previous post.
#171
Posted 05 September 2008 - 10:41 PM
P.S. - pretty close on that movie title - China Syndrome. And I'll only let folk use the mask for dipping beans out of the pot - darn, I wonder how that would work. Gotta go and file that paperwork to protect my rights to the Chinet Focus Mask and Bean Strainer. Now that's cool.
Have a great weekend.
Ron
#172
Posted 06 September 2008 - 12:23 AM
Focus is to easy with it.
Regards
Mark
http://astronomy.qte...1-SiiHaOiii.jpg
#173
Posted 06 September 2008 - 12:39 AM
Joe.
#174
Posted 06 September 2008 - 07:20 AM
It must be something about Southeast Texas, we see something that looks good and we just have to try it for ourselves, I have to admit, your reverse engineering with the highly technical Chinette plate was genious! Glad it worked, and as Adam said, watch out for the BBQ
Jim
#175
Posted 06 September 2008 - 08:26 AM
924mm ~= 4-6mm
2800mm ~= 14-18mm
5600mm ~= 28-37mm
I need 3 different masks right? I don't understand the angle relationship--do the 3 need different angles as well?
Anyone starting to get an idea of how far off your focal length can be before problems start?
Brian