#1  
Old 06-11-2019, 11:58 AM
graham.hobart's Avatar
graham.hobart (Graham stevens)
DeepSkySlacker

graham.hobart is offline
 
Join Date: Nov 2008
Location: hobart, tasmania
Posts: 1,992
spectroscopy

I am resurrecting my SA100 spect grid, with probably a colour ZWO 1200 and I am looking for tips re scopes. This will be a dedicated spect scope sitting on top of a solar scope, so does being an achro matter?
I did the calculator on the r Spec website and a sweet spot for spectra was an 80mm f6.5 skywatcher - but it is rather expensive
looking for cheap and cheerful as I have to buy rings also
Reply With Quote
  #2  
Old 06-11-2019, 12:09 PM
graham.hobart's Avatar
graham.hobart (Graham stevens)
DeepSkySlacker

graham.hobart is offline
 
Join Date: Nov 2008
Location: hobart, tasmania
Posts: 1,992
spect

Does having diffraction spikes as in an RCT affect the spectra?
Reply With Quote
  #3  
Old 06-11-2019, 12:18 PM
bojan's Avatar
bojan
amateur

bojan is offline
 
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 5,950
Quote:
Originally Posted by graham.hobart View Post
Does having diffraction spikes as in an RCT affect the spectra?
Probably not enough to be a problem.
Reply With Quote
  #4  
Old 06-11-2019, 01:35 PM
StuTodd
Registered User

StuTodd is offline
 
Join Date: Dec 2014
Location: Dunedin, New Zealand
Posts: 328
Hi Graham,

You already have DSLR camera gear?

You can use the SA100 as an "objective grating" by drilling a 32mm hole in the centre of a spare lens cap and inserting the SA100 into that, then put the cap onto a 135mm lens. You will get lovely results, be able to take fantastic multi-spectra images AND no need to buy a scope etc.

Piggybacking a DSLR then means you can track, remove the SA100 lens cap and use the lens for widefield etc etc.

As for your question, no, spikes won't make a difference to your spectra.

Last edited by StuTodd; 06-11-2019 at 01:39 PM. Reason: Spellinz
Reply With Quote
  #5  
Old 06-11-2019, 01:50 PM
graham.hobart's Avatar
graham.hobart (Graham stevens)
DeepSkySlacker

graham.hobart is offline
 
Join Date: Nov 2008
Location: hobart, tasmania
Posts: 1,992
spectroscopy

Cheers all, excited to try anything as I don't have the time for multi hour long exposures anymore (or ever actually!!)
Reply With Quote
  #6  
Old 06-11-2019, 02:05 PM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 7,027
Graham,
The SA100 works well in any scope. Preferably f5 or greater.
No issue with spider diffraction.
Poor achromats can give rise to "fishtail" shaped spectral images. (See attached)
As you probably know, a mono camera will give better result.
Any other questions, just ask.

http://www.astronomicalspectroscopy.com/How_to.html
Attached Thumbnails
Click for full-size image (IMG_0164.jpg)
35.0 KB17 views
Reply With Quote
  #7  
Old 06-11-2019, 02:35 PM
graham.hobart's Avatar
graham.hobart (Graham stevens)
DeepSkySlacker

graham.hobart is offline
 
Join Date: Nov 2008
Location: hobart, tasmania
Posts: 1,992
spectroscopy

Thanks Ken, I will ask if need be as I know we have an expert in our midst!!
Cheers. Will try for a better scope and mono then.
graz
Reply With Quote
  #8  
Old 06-11-2019, 04:49 PM
StuTodd
Registered User

StuTodd is offline
 
Join Date: Dec 2014
Location: Dunedin, New Zealand
Posts: 328
All I was trying to put across is that there is no need to buy a telescope just for using the SA100.

Stu
Reply With Quote
  #9  
Old 06-11-2019, 05:14 PM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 7,027
Stu,
No issue, the use of objective gratings is very popular, Uwe has shown some very good and higher resolution results used objective gratings.
The grating is very flexible......spectroscopy 101
It provides the opportunity of gathering Spectral data and practicing Spectral processing.
Check out our webpage for details and other ideas.
Reply With Quote
  #10  
Old 07-11-2019, 06:58 AM
tomfield (Tom)
Field Tested Systems

tomfield is offline
 
Join Date: Sep 2010
Location: Seattle, WA USA
Posts: 5
Quote:
Originally Posted by Merlin66 View Post
Stu,
The use of objective gratings is very popular. Uwe has shown some very good and higher resolution results using objective gratings.
Indeed, Uwe is a great example of someone who has shown what's possible with a Star Analyser.

Here, link, for example, is a recent posting of his, including a pdf with a nice explanation of the science of the objects he's observing.
Reply With Quote
  #11  
Old 07-11-2019, 07:14 AM
bojan's Avatar
bojan
amateur

bojan is offline
 
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 5,950
Linked pdf doc is interesting....
He was using 3 gratings in series, as visible on the image?
Or this is just the way he kept them between uses?


Also, grism arrangement is different, usually there is only one prism (this is my setup)
Attached Thumbnails
Click for full-size image (c_01.jpg)
59.2 KB13 views
Reply With Quote
  #12  
Old 07-11-2019, 08:34 AM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 7,027
Bojan,
I'm pretty sure he only uses one grating at a time but multiple prisms to correct the different dispersions.
Reply With Quote
  #13  
Old 07-11-2019, 09:19 AM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 7,027
https://groups.yahoo.com/neo/groups/...messages/13983

Bojan,
This link gives a better explanation.
Reply With Quote
  #14  
Old 08-11-2019, 05:54 AM
bojan's Avatar
bojan
amateur

bojan is offline
 
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 5,950
Quote:
Originally Posted by Merlin66 View Post
Bojan,
I'm pretty sure he only uses one grating at a time but multiple prisms to correct the different dispersions.
That was my understanding as well..

The use of multple gratings results in very confusing spectra, it is impossible to separate spurious signals from real ones.
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 AM.

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