Following in someone else's footsteps

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gabrieli
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Following in someone else's footsteps

Post by gabrieli »

I'll say many thanks to bart1805 for his great work with his (or your, if you are reading this, Bart) PST, DS module.

My hopes for my large ERF + c9.25 are that I can set it up to work at 4600mm and produce higher contrast limb images than what I've caught so far with a single stack PST etalon and single stack Quark. A DS setup with A PST + Quark does produce higher contrast images but the image is a bit dark.

So, I decided to take advantage of the promising looking trials by bart1805 and play with a double stacked PST arrangement to improve the brightness.
I ordered a PST coupler from PreciseParts in Miami and it was shipped within a week of placing the order. I fits perfectly.

Before I try the DS arrangement, I'm going to test the newer PST in SS mode to see whether it's one of those rare, accidental, narrow bandwidth models.

Unfortunately, given the weather here , I may not be able to do this for a while but I will update my attempts as they happen.

The setup follows that used by bart1805. I know that the collimating/refocussing lenses will have to be left on or removed depending on where the module is placed in the optical train. The circular polarizer is inside the adapter but, with its ring, was too wide to fit properly without interfering with the threads. I took the polarizer out of its mount and installed it that so all the mechanical fittings are not blocked.

The coupler is a bit long (35mm) but part of the etalon housing does protrude into the coupler and I wanted to be sure that there would be enough room for the polarizing filter inside the coupler and to allow tilting it. It shouldn't matter since light coming out of the 1st etalon(on right) will come out parallel for the second etalon.

Lou
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bart1805
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Re: Following in someone else's footsteps

Post by bart1805 »

Hi Lou, how cool, hope it works for you! And please don't credit me for all the work. It is thanks to this forum I tried it (as many have before). Merlin mailed me the drawing of the adapter, somebody else printed it. Gus and Randall advised the circular polariser, etc.
What worked for me is to first find the best position for both the etalons in single stack. Than to position both etalons with the ideal position 180 degrees apart. And then the trying starts.
There are still al lot of things I want to try. For example what is the best position for the polariser. And to really compare a good SS and a good DS image. But one thing is for sure: no more double limb effect. Keep us posted about your results, hope to learn a lot of your adventures.
Don't know if I told it here, but AOK Swiss made me another adapter. It has got a second threaded ring to fix the back in any position I want it. That way I can try what really is the best position. I will post a picture later on. Just have to think about a way I can turn the polariser more easily.
Good luck, Bart.


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Re: Following in someone else's footsteps

Post by bart1805 »

Hi Lou,
Here it is:
From right to left:
- 35nm Bader
- nosepiece
- etalon
- 3D printed adapter
- adapter AOK Swiss with the threaded ring
- etalon
- JMI focusser

Polariser is hidden in the AOK adapter. Still have to use the 3D printed adapter because the AOK adapter is about 1 cm to short. My fault, forgot that inside the adapter I had to put the polariser....
Bart.

Image20170926_003226_resized by bart moors, on Flickr


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Re: Following in someone else's footsteps

Post by marktownley »

Cool mods guys!


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Re: Following in someone else's footsteps

Post by Merlin66 »

Bart, et al,
I'm very pleased to see and hear the success you're having with the DS PST etalons.
As I've mentioned I'd didn't have the same level of success with my earlier trials.
It looks like the CP is a mandatory element....
Hope to see more of these in the future.
Well done.


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Derek Klepp
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Re: Following in someone else's footsteps

Post by Derek Klepp »

Good luck Lou.


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