Go Back   IceInSpace > Equipment > ATM and DIY Projects

Reply
 
Thread Tools Rate Thread
  #1  
Old 21-10-2006, 08:46 AM
Dennis
Dazzled by the Cosmos.

Dennis is offline
 
Join Date: May 2005
Location: Brisbane
Posts: 11,704
Solar Filter for C9.25 - Home made

Hello,

Here are some photos of the Baader Solar Film Astrophotography Solar Filter that I have just completed. The design is made up of an OTA mounting ring and a Baader film retaining ring as follows:

OTA mounting ring:
9mm plywood ring; OD=11.5ins, ID=10.5ins.
6mm plywood ring; OD=11.5ins, ID=10.5ins.

These were glued and screwed together to form a 15mm deep ring that fits over the corrector plate cell on the C9.25 OTA.

Baader film retaining ring:
4mm plywood ring; OD=11.5ins, ID=9.25ins (top ring)
4mm plywood ring; OD=11.5ins, ID=9.25ins (bottom ring)

The bottom ring is glued to the assembled 15mm OTA ring. Then, the Baader solar film was then placed on the bottom ring whilst the top ring was then screwed down in 6 places.

On the inside of the OTA mounting ring, I cut x 3 shallow recesses at 120 deg spacing in which I glued thin foam strips to snugly secure the filter on the OTA. I also drilled and tapped x 3 holes for nylon locking bolts so that once fitted, the filter can be firmly locked in place.

Cheers

Dennis
Attached Thumbnails
Click for full-size image (Solar Filter Collage.jpg)
95.4 KB178 views
Reply With Quote
  #2  
Old 21-10-2006, 09:26 AM
[1ponders]'s Avatar
[1ponders] (Paul)
Retired, damn no pension

[1ponders] is offline
 
Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
Jeez Dennis, I was going to post my cardboard and gaffa tape ones but how can I after seeing your work of art


Nice workmanship mate. Now I know you definately have too much time on your hands.
Reply With Quote
  #3  
Old 21-10-2006, 09:30 AM
acropolite's Avatar
acropolite (Phil)
Registered User

acropolite is offline
 
Join Date: Feb 2005
Location: Launceston Tasmania
Posts: 9,019
Excellent idea Dennis, particularly the locking bolts. I was going down the cardboard and stickytape route, but your idea looks better.
Reply With Quote
  #4  
Old 21-10-2006, 09:48 AM
netwolf's Avatar
netwolf
Registered User

netwolf is offline
 
Join Date: Jan 2005
Posts: 2,943
Great work Dennis, I like the nylon threads concept. Did you make the plywood rings yourself? Are the available of the shelf?

Regards
Reply With Quote
  #5  
Old 21-10-2006, 10:05 AM
Dennis
Dazzled by the Cosmos.

Dennis is offline
 
Join Date: May 2005
Location: Brisbane
Posts: 11,704
Hello,

The plywood rings were cut from left over’s from other projects and I used a router to cut the rings. It was quite fiddly and time consuming, clamping the work and cutting the circles, so unless you have the equipment, time and skills, I really wouldn’t bother with a wooden frame.

The cardboard models, if well made, certainly look strong enough and are also more lightweight if balance may be an issue? All I have to do is slide the C9.25 in the dovetail mount to re-balance the ‘scope. With a dob, this may not be so easy?

Solar filters tend to get used infrequently so if handled and stored correctly, there is really no advantage in making a wooden model, unless you have too much time on your hands…

If you build up the reinforcing around three points on the circumference wall of the cardboard model, I'm sure it would be possible to insert some nylon locking screws and provided you don’t tighten them too much, they should provide a good enough safety grip.

Cheers

Dennis
Reply With Quote
  #6  
Old 21-10-2006, 10:24 AM
netwolf's Avatar
netwolf
Registered User

netwolf is offline
 
Join Date: Jan 2005
Posts: 2,943
I think the Nylon thread or some method to keep it tightly on is a must. Becuase the last thing you want is a strong breaze or child to knock it off while viewing the sun.

Regards
Reply With Quote
  #7  
Old 21-10-2006, 10:32 AM
Dennis
Dazzled by the Cosmos.

Dennis is offline
 
Join Date: May 2005
Location: Brisbane
Posts: 11,704
Other options for securing a cardboard ring are:

Using a hole punch, punch a couple of holes in the cardboard ring at 180 degrees and thread some string through the holes and fasten the string to the top and bottom mounting rails (if you have them), or around the OTA.

You could also add (glue/staple) 3 tabs or ears that stick out from the cardboard mounting ring and then tie some string around the OTA that passes over the top of these tabs or ears, thus securing the ring to the OTA.

Cheers

Dennis
Reply With Quote
  #8  
Old 21-10-2006, 10:38 AM
[1ponders]'s Avatar
[1ponders] (Paul)
Retired, damn no pension

[1ponders] is offline
 
Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
Or adhesive velcro tabs.
Reply With Quote
  #9  
Old 21-10-2006, 11:49 AM
netwolf's Avatar
netwolf
Registered User

netwolf is offline
 
Join Date: Jan 2005
Posts: 2,943
What about modifying dust caps to be the cell?
Are extra dust caps available for purchase?
My Dob has a dust cap that plugs in tightly.

Regards
Reply With Quote
  #10  
Old 25-10-2006, 01:32 PM
JimmyH155
Registered User

JimmyH155 is offline
 
Join Date: May 2006
Location: Burpengary
Posts: 619
solar film

I'm planning on using thick rubber bands over the tabs.
Reply With Quote
  #11  
Old 02-10-2011, 05:06 AM
originaltrilogy (Petr)
Registered User

originaltrilogy is offline
 
Join Date: Oct 2011
Location: Bathurst, NSW
Posts: 116
Why does the wrinkliness of the film not make for bad images when looking?
This is a very professional looking job.
Reply With Quote
  #12  
Old 02-10-2011, 07:07 PM
Dennis
Dazzled by the Cosmos.

Dennis is offline
 
Join Date: May 2005
Location: Brisbane
Posts: 11,704
Quote:
Originally Posted by originaltrilogy View Post
Why does the wrinkliness of the film not make for bad images when looking?
This is a very professional looking job.
From memory, the information sheet that came with the Baader Solar Film recommended that the film should not be fitted taut - a looser fitting (not stretched) was preferred and did not affect the optical performance.

Cheers

Dennis

More details here:
http://www.baader-planetarium.com/so...nleitung_e.htm

Last edited by Dennis; 02-10-2011 at 07:12 PM. Reason: Added link to Baader website
Reply With Quote
  #13  
Old 26-10-2011, 03:13 PM
alistairsam's Avatar
alistairsam
Registered User

alistairsam is offline
 
Join Date: Nov 2009
Location: Box Hill North, Vic
Posts: 1,837
Hi
I wanted to make a Mylar solar filter for my 8" F4 reflector ota and wanted to know if it's necessary to have a full aperture filter
If not how do you work out what the size of the aperture should be and why are some of the solar filter apertures off centre?
Does it depend on focal length of the telescope and eyepiece?
Reply With Quote
  #14  
Old 26-10-2011, 06:57 PM
brian nordstrom (As avatar)
Registered User

brian nordstrom is offline
 
Join Date: Apr 2007
Location: Perth WA
Posts: 4,374
Nice job Dennis , 1 question , where did you get the nylon bolts ?

I have never seen these for sale .
I bet the sun looks nice in this .
Awsome mate .
Brian.
Reply With Quote
  #15  
Old 26-10-2011, 07:01 PM
brian nordstrom (As avatar)
Registered User

brian nordstrom is offline
 
Join Date: Apr 2007
Location: Perth WA
Posts: 4,374
Petr , the wrinkles are there to stop the film tearing under expansion as the film heats up , and mate thats the LAST thing you want to happen .

I would not know how ( or why ) the view is so clear with all those wrinkles in it , but mate it works very well .
Brian.
Quote:
Originally Posted by originaltrilogy View Post
Why does the wrinkliness of the film not make for bad images when looking?
This is a very professional looking job.
Reply With Quote
  #16  
Old 26-10-2011, 08:00 PM
Dennis
Dazzled by the Cosmos.

Dennis is offline
 
Join Date: May 2005
Location: Brisbane
Posts: 11,704
Quote:
Originally Posted by brian nordstrom View Post
Nice job Dennis , 1 question , where did you get the nylon bolts ?

I have never seen these for sale .
I bet the sun looks nice in this .
Awsome mate .
Brian.
Hi Brian

I obtained the (nylon) screws from:

http://www.hobbyparts.com.au/store/p...eners/wide/61/

Cheers

Dennis
Reply With Quote
  #17  
Old 26-10-2011, 10:35 PM
originaltrilogy (Petr)
Registered User

originaltrilogy is offline
 
Join Date: Oct 2011
Location: Bathurst, NSW
Posts: 116
Quote:
Originally Posted by brian nordstrom View Post
Petr , the wrinkles are there to stop the film tearing under expansion as the film heats up , and mate thats the LAST thing you want to happen .

I would not know how ( or why ) the view is so clear with all those wrinkles in it , but mate it works very well .
Brian.
I understand it works, but it amazes me. We worry very much about optics and then wrinkly film does not affect image, I don't understand even though is true!
Reply With Quote
  #18  
Old 27-10-2011, 03:28 AM
Merlin66's Avatar
Merlin66 (Ken)
Registered User

Merlin66 is offline
 
Join Date: Oct 2005
Location: Junortoun Vic
Posts: 8,904
The thickness and surface accuracy of the Baader Sheet is sufficient that the wrinkled sheet still performs 100%!!
Dennis,
What sized Baader sheet did you use for the 9.25?? I thought the A4 size was too small????
Reply With Quote
  #19  
Old 27-10-2011, 06:33 AM
Dennis
Dazzled by the Cosmos.

Dennis is offline
 
Join Date: May 2005
Location: Brisbane
Posts: 11,704
There were 2 sizes available when I purchased mine. The one I ordered was:

AstroSolar ™ Photo Film D=3.8 (100x50cm/39x20 inch)

More details here – scroll to the bottom for the sizes.

Cheers

Dennis
Reply With Quote
  #20  
Old 27-10-2011, 09:17 AM
Merlin66's Avatar
Merlin66 (Ken)
Registered User

Merlin66 is offline
 
Join Date: Oct 2005
Location: Junortoun Vic
Posts: 8,904
OK thanks for that!
(BTW the ND3.8 is the photographic version - ND5 for Visual)
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 08:36 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Testar
Advertisement
Bintel
Advertisement