Spider free mount for secondary mirror

  • Thread starter vincentm
  • Start date
  • #1
321
3
Is there any kits i can purchase? I'd like to avoid diffraction as much as possible.
 

Answers and Replies

  • #2
mgb_phys
Science Advisor
Homework Helper
7,774
13
The only alternative (except possibly magnetic leviation) would be to stick it on a sheet of plane glass.
 
  • #3
321
3
The only alternative (except possibly magnetic leviation) would be to stick it on a sheet of plane glass.
See, that's what i'd like to do, but where would i be able to purchase the rings to keep it in place?
 
  • #4
turbo
Gold Member
3,077
46
Your best bet is to look into a spider with smoothly curved arms. If you fastened a secondary to an optical flat, you would introduce two more air-glass surfaces and decrease the contrast of your scope. Curve-arm spiders have been in use for many years.
 
  • #5
321
3
Your best bet is to look into a spider with smoothly curved arms. If you fastened a secondary to an optical flat, you would introduce two more air-glass surfaces and decrease the contrast of your scope. Curve-arm spiders have been in use for many years.
Ok, that makes sense turbo, I've purchased all the parts in order to make mine curved (hack saw blades via the scopemaking.net guide), i was just curious about pursuing this route.
 
  • #6
tony873004
Science Advisor
Gold Member
1,751
143
What's the advantage of using a curved spider arm over a straight one?
 
  • #7
mgb_phys
Science Advisor
Homework Helper
7,774
13
What's the advantage of using a curved spider arm over a straight one?
The difraction spikes instead of being distinct crosses around each star will be smeared out. Since each point in the spider will create a weaker diffraction spike at a different rotation angle.

Overall it's poorer signal to noise, but it looks clearer for naked eye observations.
 
  • #8
Redbelly98
Staff Emeritus
Science Advisor
Homework Helper
Insights Author
12,116
152
Curved arms would spread the diffracted light through different angles (i.e. a larger area), making it fainter. A straight edge "bends" the light in one direction only, hence the bright, directional diffraction spikes that are common with straight-edge spiders.
 
  • #9
2
0
The only alternative (except possibly magnetic leviation) would be to stick it on a sheet of plane glass.
Or sell your current telescope and buy a Catadioptric telescope which has a weak, correcting front lens on which the secondary is mounted.
 
  • #10
Chronos
Science Advisor
Gold Member
11,408
741
I've been intrigued by off axis mirror designs for a number of years. They are capable of views rivaling, or even surpassing the finest refractors. Unfortunately they are difficult to make and have existed only among the ranks of the most ambitious and gifted amateur telescope makers until fairly recently Some commercial models are now available - e.g., http://users.erols.com/dgmoptics/indexwelcome
 

Related Threads on Spider free mount for secondary mirror

Replies
1
Views
803
  • Last Post
Replies
2
Views
3K
Replies
2
Views
3K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
3
Views
4K
Replies
2
Views
4K
Replies
4
Views
1K
Replies
3
Views
6K
Replies
1
Views
5K
Replies
8
Views
5K
Top