Go Back   IceInSpace > Equipment > Equipment Discussions

Reply
 
Thread Tools Rate Thread
  #1  
Old 27-03-2016, 06:16 PM
luka's Avatar
luka
Unregistered User

luka is offline
 
Join Date: Apr 2007
Location: Perth, Australia
Posts: 1,164
Mounting of a special filter

Hi

I may be able to get hold of a special H alpha filter. Originally this was not an astronomical filter and has 50.0mm diameter and transmission FWHM of 0.5nm, i.e. it is extremely narrowband. I believe it is about 6-7mm thick (to be confirmed). It does not have any threads for mounting, just a metal ring on the outer diameter.

Any ideas how to mount such filter? Currently I use ED80 + Hotech SCA flattener + T-ring + DSLR (IR modified).

Also would FWHM of 0.5nn be a problem? I can imagine it would completely kill the light pollution :-)

Thanks
Luka
Reply With Quote
  #2  
Old 27-03-2016, 06:39 PM
glend (Glen)
Registered User

glend is offline
 
Join Date: Jun 2013
Location: Lake Macquarie
Posts: 7,033
It will may also significantly lengthen sub exposure times. Typical Ha filters are about 7nm, extreme narrow gets down to 3nm, wider are around 12nm. Is the filter multi-coated? The thickness will likely affect light path and at least change the focal point.
Reply With Quote
  #3  
Old 27-03-2016, 09:00 PM
luka's Avatar
luka
Unregistered User

luka is offline
 
Join Date: Apr 2007
Location: Perth, Australia
Posts: 1,164
Thank you for a reply Glen.

You may be right about the longer exposure time. I don't have the actual transmission numbers for this filter (yet) but the narrower they are the less transmission they have and more expensive they get. I would be surprised if this one lets more than 50% at its peak.

Multicoating - not sure but I believe so.

Focusing is probably not an issue as there is lots of room either way in my current setup.

I was more concerned about finding a way to physically mount it. I can borrow it to test it but I have to solve the mounting problem first...

I was looking at 2" filter wheels but I can't justify spending $200-$300 for a test... and the filter thickness may be an issue.
Reply With Quote
  #4  
Old 27-03-2016, 10:03 PM
OzEclipse's Avatar
OzEclipse (Joe Cali)
Registered User

OzEclipse is offline
 
Join Date: Jun 2012
Location: Young Hilltops LGA, Australia
Posts: 1,177
Luka
0.5nm is more typical of a solar Ha prominence filter

Joe
Reply With Quote
  #5  
Old 28-03-2016, 09:15 PM
csb's Avatar
csb (Craig)
Registered User

csb is offline
 
Join Date: Apr 2007
Location: Adelaide, Sth Australia
Posts: 909
It would be risky business to use that filter for solar observing.

Also for solar Ha telescope viewing must have an ERF (Energy Rejection Filter).
Reply With Quote
  #6  
Old 28-03-2016, 10:20 PM
luka's Avatar
luka
Unregistered User

luka is offline
 
Join Date: Apr 2007
Location: Perth, Australia
Posts: 1,164
The filter was used in some lab for laser experiments. I would not use it for solar, too risky as already mentioned.
Reply With Quote
Reply

Bookmarks

Tags
filters

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 03:00 AM.

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