#1  
Old 29-10-2019, 05:58 AM
poider (Peter)
Registered User

poider is offline
 
Join Date: Apr 2012
Location: Adelaide, Australia
Posts: 224
Bahtinov mask

Just a quick question on bahtinov masks if I get one for my camera lenses does it matter for varying focal lengths, should i make one for each length?
Reply With Quote
  #2  
Old 29-10-2019, 01:53 PM
xelasnave's Avatar
xelasnave
Gravity does not Suck

xelasnave is offline
 
Join Date: Mar 2005
Location: Tabulam
Posts: 16,866
I have tried mine used for the 80mm on the 115 mm a d it seemed ok..the only reason I did not use it for a full session was the distance from the lappy to the scope meant I had to walk from one to the other for each adjustment..so I blew up a bright star a d stood at the scope to adjust...I suspect it should work on different FLs at this stage.
Alex
Reply With Quote
  #3  
Old 29-10-2019, 04:41 PM
poider (Peter)
Registered User

poider is offline
 
Join Date: Apr 2012
Location: Adelaide, Australia
Posts: 224
Thank you Alex, I don't use a laptop... yet
Reply With Quote
  #4  
Old 29-10-2019, 07:17 PM
poider (Peter)
Registered User

poider is offline
 
Join Date: Apr 2012
Location: Adelaide, Australia
Posts: 224
Do I need a laptop to use a bahtinov mask?
Reply With Quote
  #5  
Old 29-10-2019, 08:11 PM
iborg's Avatar
iborg (Philip)
Registered User

iborg is offline
 
Join Date: Feb 2015
Location: Lynbrook, Australia
Posts: 611
Hi

I think a laptop can help, because it makes for a larger image, but, so long as you can the three spikes well enough you should be fine.

Philip
Reply With Quote
  #6  
Old 29-10-2019, 08:11 PM
Imme (Jon)
Registered User

Imme is offline
 
Join Date: Aug 2017
Location: Kyneton
Posts: 840
No to the laptop....as long as you can see the picture on camera screen
Reply With Quote
  #7  
Old 29-10-2019, 08:31 PM
Sunfish's Avatar
Sunfish (Ray)
Registered User

Sunfish is offline
 
Join Date: Mar 2018
Location: Wollongong
Posts: 1,909
Depends on the scope. My c8 is easy to use a Bahtinov mask cut from sheet plastic to a pattern created by the generator available online with 5mm bars.

Live view on a DSLR on a bright star shows a pattern easily.

The 100mm refractor is a bit harder and requires a very bright star , full zoomed in live view and a very fine Bahtinov mask to be able see the diffraction pattern.
Reply With Quote
  #8  
Old 29-10-2019, 08:33 PM
Dennis
Dazzled by the Cosmos.

Dennis is offline
 
Join Date: May 2005
Location: Brisbane
Posts: 11,704
My experience has been that I have struggled to get a reliable focus on lenses smaller than 100mm focal length, even when using the x10 magnified Live View on the rear LCD.

The diffraction spikes were just too small to interpret with any confidence. This was using a Bahtinov Mask designed for a 102 mm aperture instrument.

Cheers

Dennis
Reply With Quote
  #9  
Old 29-10-2019, 08:45 PM
poider (Peter)
Registered User

poider is offline
 
Join Date: Apr 2012
Location: Adelaide, Australia
Posts: 224
Thank you all I have seen the mask generator, I use a 10 - 20mm lens, a 50mm lens, a 18-300mm lens and a 150-500mm lens, mainly the 150 to 500mm so if I generated a mask what would the focal length be that I would generate it to?
Reply With Quote
  #10  
Old 30-10-2019, 01:22 PM
Sunfish's Avatar
Sunfish (Ray)
Registered User

Sunfish is offline
 
Join Date: Mar 2018
Location: Wollongong
Posts: 1,909
You might try my fishing line model which works very well on 100mm F8 lense. As shown in the attached image. Also see a version made by the Avertons which is the same thing fine tuned and they provide a dxf file. I will se if I can find a PDF.

http://www.iceinspace.com.au/forum/s...7&postcount=27

With a refractor the bars and spacing needs to be as fine as you can, 1 mm bars or fishing line is ideal. I posted a dxf in that thread.

When I say 100mm that is the diameter of my old manual NIKON F8 800mm lense and also my ancient Pentax 67 f4 400mm. Have not tried a smaller diameter lense but maybe your 500 is big enough. I think live view full zoom focus is good enough for shorter focal length wide field work. I think my live view zoom is 10x
Attached Thumbnails
Click for full-size image (16CECFDF-F4C0-4C2F-8E1B-AFE77DC4270D.jpg)
187.3 KB109 views
Click for full-size image (85B7E008-E155-42FB-A62B-0F389EA2D3B1.jpg)
185.7 KB135 views

Last edited by RB; 30-10-2019 at 03:58 PM.
Reply With Quote
  #11  
Old 19-11-2019, 09:12 PM
BadSean (Sean)
Registered User

BadSean is offline
 
Join Date: Mar 2019
Location: Perth
Posts: 5
Quote:
Originally Posted by Sunfish View Post
You might try my fishing line model which works very well on 100mm F8 lense. As shown in the attached image. Also see a version made by the Avertons which is the same thing fine tuned and they provide a dxf file. I will se if I can find a PDF.

http://www.iceinspace.com.au/forum/s...7&postcount=27

With a refractor the bars and spacing needs to be as fine as you can, 1 mm bars or fishing line is ideal. I posted a dxf in that thread.
That is a VERY neat solution.

I've found that chunky line bahtinov masks didn't make things as easy to focus as I would have liked when using a camera lens (the panasonic leica 100-400mm, and olympus 40-150 f2.8) with live view between 5x and 14x.

I'm going to try the fishing line mask for my camera lenses. Hopefully I get better results.

If the mask I have sent to print for my RC8 doesn't work out, I will definitely be trying out your fishing line method for that too.
Reply With Quote
  #12  
Old 16-12-2019, 05:07 PM
poider (Peter)
Registered User

poider is offline
 
Join Date: Apr 2012
Location: Adelaide, Australia
Posts: 224
Quote:
Originally Posted by BadSean View Post
That is a VERY neat solution.

I've found that chunky line bahtinov masks didn't make things as easy to focus as I would have liked when using a camera lens (the panasonic leica 100-400mm, and olympus 40-150 f2.8) with live view between 5x and 14x.

I'm going to try the fishing line mask for my camera lenses. Hopefully I get better results.

If the mask I have sent to print for my RC8 doesn't work out, I will definitely be trying out your fishing line method for that too.
Are you happy with the 4/3 system for astro, i have a 1.5 crop nikon and a 4/3 olympus em10 mark 3, havent done much with the oly yet but will eventually
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 11:43 AM.

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