Go Back   IceInSpace > Equipment > ATM and DIY Projects

Reply
 
Thread Tools Rating: Thread Rating: 12 votes, 4.92 average.
  #201  
Old 19-03-2015, 08:26 PM
Rac's Avatar
Rac (Raymond)
Registered User

Rac is offline
 
Join Date: Dec 2012
Location: Whangarei, New Zealand
Posts: 120
Quote:
Originally Posted by dave brock View Post
A superb result, Raymond. Well done.
Time to check that Royce 10" for a possible refigure?

Dave
Haha yeah. I did have a look at it with the ronchi screen. It has something funky going on at about 75-80% I'll have to take a pic of it, it looks more like a patch of bad roughness than anything else. It was a few months ago i looked at it. It produces really nice images and views so i can't see me doing anything to it. My next project other than a scope for this mirror is a vacuum chamber.

I had a good compare between the 10" Royce and this 18" mirror tonight. I couldn't really see anything between them other than Jupiter's moons were smaller in the 18", the seeing wasn't that great but i would give the edge for detail to the uncoated 18". I need to make a real scope for it as collimation is inconsistent with my test Dob scope i've made for it.
Reply With Quote
  #202  
Old 20-03-2015, 03:03 PM
sopticals's Avatar
sopticals (Stephen)
Registered User

sopticals is offline
 
Join Date: Jun 2010
Location: Oamaru, New Zealand.
Posts: 206
Smile

Quote:
Originally Posted by dave brock View Post
A superb result, Raymond. Well done.

Dave
+1 Excellent result. Just goes to show that an ATMer can grind, polish, and successfully figure a large aperture mirror to a high degree of accuracy "straight out of the blocks". There is so much help out there on the internet, for anyone who has the determination, and patience, to take on such a project. Again super effort.

Stephen.
Reply With Quote
  #203  
Old 20-03-2015, 04:04 PM
Rac's Avatar
Rac (Raymond)
Registered User

Rac is offline
 
Join Date: Dec 2012
Location: Whangarei, New Zealand
Posts: 120
So Stephen what do you use for diagonal mirrors with such large primary mirrors?
Reply With Quote
  #204  
Old 21-03-2015, 01:04 PM
sopticals's Avatar
sopticals (Stephen)
Registered User

sopticals is offline
 
Join Date: Jun 2010
Location: Oamaru, New Zealand.
Posts: 206
Smile

Hi Raymond,

bit of a quandary really. My 14"f5.1 and 25"f4.7 (Also have 25"f5 and f5.3 mirrors, [need varying amounts of figuring to finish off properly]) use 3.1"ma and 4" ma secondaries sourced from Hubble Optics, (reasonably priced, and work quite well).

For a 33"f4, going to need at least a 6 1/2"ma (for good size fif). Looking around the "net", looks like US$1000 HO to US$1350 Astro Systems + Freight + GST etc, so wouldn't have much change out of NZD$2000, so way out of my budget, (want to build entire scope for less than NZD$2000).

So looking at my options, and seems only to be the one, make it myself. Got plenty of thick glass lying around (still 1/2 ton), included are a number of 12.2"/12.6" diameter blanks 1 3/8"/1 1/2" thickness. So will probably take out three of these, and do the ABC grind for a flat surface, waterjet from one a 7"ma ellipse, and with "net" help, hope to be able to successfully reasonably figure same.

Takes me back to my mid teens when the biggest scope I could locate, and buy in NZ (1961), was a 3" reflector I paid 17pounds 10shillings($35),which cost me a months wages, (farm hand) at the time. Also had a 2 1/2" refractor (used) 22pounds.($44). In those days the moto was, "if you cant get it, then you have to make it". As this was the only option, built my first 5 3/4"/7"(made two mirrors-the second the 7" mirror was really quite good to 50x per inch) EQ mounted Newt from the mirror up. Really things haven't changed that much, "necessity being the mother of invention".
Reply With Quote
  #205  
Old 21-03-2015, 05:01 PM
Rac's Avatar
Rac (Raymond)
Registered User

Rac is offline
 
Join Date: Dec 2012
Location: Whangarei, New Zealand
Posts: 120
Well you could make a sphere out of one of those blanks for testing the flat. I have thought about that myself. I have an old 8" f6 bk7 GSO mirror here that would be good for sacrificing for a secondary.
Reply With Quote
  #206  
Old 26-03-2015, 01:30 PM
boardriderz (Jimmy)
Registered User

boardriderz is offline
 
Join Date: Jun 2012
Location: Brisbane, QLD, Australia
Posts: 22
Any mirror makers active in Brisbane?

Hi guys (and girls)

I just wanted to see if there are any active mirror makers in the Brisbane area. I have been following this and other forums for years and want to get back to my first project, a simple 6 inch mirror, before tackling something a bit more ambitious. Online advice is great, but it is also great to have a few other people to bounce ideas of and of course, as I live in a unit, tools and testing equipment are an issue.

Jimmy
Reply With Quote
  #207  
Old 03-04-2015, 10:54 AM
frankly1's Avatar
frankly1 (Frank)
Registered User

frankly1 is offline
 
Join Date: Oct 2010
Location: Weyba Downs, Qld.
Posts: 34
Hi folks, great work Raymond with that mirror. Seems like we are all at that point of secondary mirror problems. I picked up a coffee table with a 14mm glass top from the tip for $5. It was immediately cut up for 4 diagonals. Like you folk, I also need to now explore flat making...
Reply With Quote
  #208  
Old 03-04-2015, 10:59 AM
frankly1's Avatar
frankly1 (Frank)
Registered User

frankly1 is offline
 
Join Date: Oct 2010
Location: Weyba Downs, Qld.
Posts: 34
Quote:
Originally Posted by boardriderz View Post
Hi guys (and girls)

I just wanted to see if there are any active mirror makers in the Brisbane area. I have been following this and other forums for years and want to get back to my first project, a simple 6 inch mirror, before tackling something a bit more ambitious. Online advice is great, but it is also great to have a few other people to bounce ideas of and of course, as I live in a unit, tools and testing equipment are an issue.

Jimmy
Welcome Jimmy, there is a small Brisbane ATM group although it is having location problems at the moment. I am on the Sunny Coast, but get down to Brisbane now and then to the meeting. More details when the dust settles if you want.
Reply With Quote
  #209  
Old 03-04-2015, 05:46 PM
sopticals's Avatar
sopticals (Stephen)
Registered User

sopticals is offline
 
Join Date: Jun 2010
Location: Oamaru, New Zealand.
Posts: 206
Smile

Quote:
Originally Posted by frankly1 View Post
Hi folks, I picked up a coffee table with a 14mm glass top from the tip for $5. It was immediately cut up for 4 diagonals. Like you folk, I also need to now explore flat making...
Hi Frank,

how did you get the diagonals cut? Were they cut at 45degs? I have been trying to figure out how to cut 7" minor axis diagonals, from 35mm thick plate glass. Would much prefer the 45deg angle cut, rather than waterjet cut on the flat.

Best regards
Stephen
Reply With Quote
  #210  
Old 03-04-2015, 06:51 PM
frankly1's Avatar
frankly1 (Frank)
Registered User

frankly1 is offline
 
Join Date: Oct 2010
Location: Weyba Downs, Qld.
Posts: 34
Quote:
Originally Posted by sopticals View Post
Hi Frank,

how did you get the diagonals cut? Were they cut at 45degs? I have been trying to figure out how to cut 7" minor axis diagonals, from 35mm thick plate glass. Would much prefer the 45deg angle cut, rather than waterjet cut on the flat.

Best regards
Stephen
I have only rough cut them with the trusty angle grinder with diamond blade at this stage to about 145mm on the minor axis so as to have some in the middle that might be flat. I was then planning to cut closer to desired shape when polished, and then hand grind to final shape with the 45 deg. chamfer, hoping not to chip anything. I am very open to suggestions...
cheers Stephan,
Frank
Reply With Quote
  #211  
Old 03-04-2015, 07:04 PM
Rac's Avatar
Rac (Raymond)
Registered User

Rac is offline
 
Join Date: Dec 2012
Location: Whangarei, New Zealand
Posts: 120
What about setting the glass in plaster at 45deg then drilling it with a large round metal tube with silicon carbide and water. You would need a large drill press.
Reply With Quote
  #212  
Old 04-04-2015, 07:57 PM
sopticals's Avatar
sopticals (Stephen)
Registered User

sopticals is offline
 
Join Date: Jun 2010
Location: Oamaru, New Zealand.
Posts: 206
Smile

Quote:
Originally Posted by Rac View Post
What about setting the glass in plaster at 45deg then drilling it with a large round metal tube with silicon carbide and water. You would need a large drill press.
Hi Raymond,

I have been thinking along the same line. I don't have a drill press, but have been looking at the possibility of getting one,(or access to), it would have to be large. Would be a long cut (7"x sq.rt 2),just shy of 10"(+thickness of glass x sq.rt 2), in all approx. 12" deep.
Reply With Quote
  #213  
Old 23-04-2015, 07:43 PM
sopticals's Avatar
sopticals (Stephen)
Registered User

sopticals is offline
 
Join Date: Jun 2010
Location: Oamaru, New Zealand.
Posts: 206
Smile Elliptical

Problem solved. Managed to source a 7.2" minor axis 1/10 wave secondary locally. Very reasonably priced. Will be able to continue with the 33"f4 project and stay within my previous budget.

Stephen.
Attached Thumbnails
Click for full-size image (IMG_2995.JPG)
122.0 KB60 views
Reply With Quote
  #214  
Old 27-04-2015, 05:52 PM
Rac's Avatar
Rac (Raymond)
Registered User

Rac is offline
 
Join Date: Dec 2012
Location: Whangarei, New Zealand
Posts: 120
Nice. That thing is huge.
Reply With Quote
  #215  
Old 01-05-2015, 06:12 PM
Rac's Avatar
Rac (Raymond)
Registered User

Rac is offline
 
Join Date: Dec 2012
Location: Whangarei, New Zealand
Posts: 120
Here's a shot of my 18" f3.3 mirror silvered and in the scope.

Click image for larger version

Name:	IMG_1043small.jpg
Views:	92
Size:	76.7 KB
ID:	181493
Reply With Quote
  #216  
Old 02-05-2015, 12:52 PM
Rac's Avatar
Rac (Raymond)
Registered User

Rac is offline
 
Join Date: Dec 2012
Location: Whangarei, New Zealand
Posts: 120
Here's an image I did of Saturn with it last night just to prove it works

Wasn't the best seeing either.
Click image for larger version

Name:	Saturn1.jpg
Views:	85
Size:	37.4 KB
ID:	181512
Reply With Quote
  #217  
Old 04-05-2015, 06:19 PM
sopticals's Avatar
sopticals (Stephen)
Registered User

sopticals is offline
 
Join Date: Jun 2010
Location: Oamaru, New Zealand.
Posts: 206
Smile Great work

Quote:
Originally Posted by Rac View Post
Here's a shot of my 18" f3.3 mirror silvered and in the scope.

Attachment 181493
Nice job Raymond. Also nice pic of Saturn. Now you need to revise your signature, to include this scope. Again congratulations on finishing a great project. Still got more glass if you want a new project.
Reply With Quote
  #218  
Old 21-05-2015, 07:21 AM
frankly1's Avatar
frankly1 (Frank)
Registered User

frankly1 is offline
 
Join Date: Oct 2010
Location: Weyba Downs, Qld.
Posts: 34
Hi all, thought I would let you know how the 18" of the 19" turned out. Had a problem star testing using Antares, as there seemed to be an optical defect that looked like a little blue star next to it. Turned out it was the Antares partner. I had no idea it was a double!
As for the silvering, it is a bit thin as I can just see through it so probably about 5nm thick, I think you need about 100nm to get a complete film.
On another subject there were terrible star test images showing triangular shaped star rings. This was caused by a wooden curved support for the lower part of the mirror. This has been replaced with a packing tape band to support the mirror and now stars are tack sharp, and Saturn looks like Raymond's pic. (Congrats Raymond, good effort). BTW I found a diag at Bintel suitable for f4.7, so allis well.
Reply With Quote
  #219  
Old 23-05-2015, 11:42 AM
sopticals's Avatar
sopticals (Stephen)
Registered User

sopticals is offline
 
Join Date: Jun 2010
Location: Oamaru, New Zealand.
Posts: 206
Smile

Quote:
Originally Posted by frankly1 View Post
Hi all, thought I would let you know how the 18" of the 19" turned out. BTW I found a diag at Bintel suitable for f4.7, so allis well.
Hi frankly,

Good stuff, you will be pleased with the result. What size is your secondary?

Just acquired another secondary myself, suitable for 48" f3.5. Might be a problem getting a blank that size.
Attached Thumbnails
Click for full-size image (IMG_3010.JPG)
159.6 KB46 views

Last edited by sopticals; 23-05-2015 at 06:42 PM.
Reply With Quote
  #220  
Old 23-05-2015, 04:21 PM
Rac's Avatar
Rac (Raymond)
Registered User

Rac is offline
 
Join Date: Dec 2012
Location: Whangarei, New Zealand
Posts: 120
You could do a 33" f2.5, That would make good use of the 9" secondary.
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 03:55 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Celestron Australia
Advertisement
Meade Australia
Advertisement
NexDome Observatories
Advertisement
SkyWatcher Australia
Advertisement
OzScopes Authorised Dealer
Advertisement
Lunatico Astronomical
Advertisement
Astronomy and Electronics Centre
Advertisement