#21  
Old 01-10-2024, 03:39 PM
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Merlin66 (Ken)
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Bojan,
On the Christian Buil webpage, he shows his prism mounted to the FRONT of the SA100 (held in place with a couple of dabs of hot melt. (I'll find the link an post it)
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  #22  
Old 01-10-2024, 03:43 PM
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Here's the original page:
http://www.astrosurf.com/aras/staran.../userguide.htm
Also an interesting read on Cloudy Nights
https://www.cloudynights.com/topic/7...configuration/
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Old 01-10-2024, 04:17 PM
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Hi Ken,

Yes, I know about the order prism-grating.
However, I was wandering how to increase dispersion on the setup (earlier w/o Tilter) by increasing the distance of grating from sensor, and found a discussion somewhere (when I find it again, I will post it here) that the order can be reversed (by mirroring the whole assembly), and indeed I tested this by making mistake (just reversing the order), see here: https://www.iceinspace.com.au/forum/...6&postcount=19


My first results with this setup were on Sat night, Nova Sco.


I am also thinking about slightly different setup, like on the attached image.
Basically, I want to convert f/10 beam to parallel, to avoid coma.
This will be my next project..
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Last edited by bojan; 01-10-2024 at 04:49 PM.
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  #24  
Old 01-10-2024, 04:52 PM
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Providing a parallel beam to the grating is a very common solution.
As you show, a Barlow can be used, positioned at its focal length from the telescope focus. Fitting the grating to the front of a camera lens and using a DSLR for imaging has been very successful.
(If you use a positive collimating lens you can then think about adding an entrance slit for even better results.)
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Old 04-10-2024, 07:40 AM
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Quote:
Originally Posted by Merlin66 View Post
..(If you use a positive collimating lens you can then think about adding an entrance slit for even better results.)
Yep.. I am considering that for the future

I have an old Panagor slide duplicator. the mechanic is ideal for that sort of thing... (coronagraph as well), see attached sketch attached).
It has standard M42x0.75 mm threads, so it is easy to change configuration.

Also, I 3D-printed inserts to hold various lenses..

The only disadvantage is length (~300 mm).. but I can live with that :-)
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Old 04-10-2024, 07:55 AM
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I also have one of those old slide copiers! Never thought of using it.
I did use a Chinese eyepiece projection tube with an eyepiece etc.
In you drawing, I can't see the imaging lens behind the grating. Am I missing something?
(See: "Astronomical Spectroscopy for Amateurs". p184-193 for grating/ slit ideas)
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Old 04-10-2024, 08:13 AM
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Quote:
Originally Posted by Merlin66 View Post
..
In you drawing, I can't see the imaging lens behind the grating. Am I missing something?
(See: "Astronomical Spectroscopy for Amateurs". p184-193 for grating/ slit ideas)
No, you are not :-)
This is my older drawing, imaging lens can be added after prism.
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