PST Mod Complete

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seti_v2
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PST Mod Complete

Post by seti_v2 » Sun Mar 15, 2015 3:30 pm

Used Orion 120mm f5 scope. Changed the front collimating lens in the pst etalon assembly to -100fl. zhumell sct focuser and celestron diagonal to attach the pst itf and blocking filter. Also Rosco UV/IR 5.25" and Rosco flame red 5.25" dichroic filters used before the objective for an ERF.



Seeing was absolutely atrocious, worst i've ever seen. Just had to try to see if the setup all worked. I was able to tune and focus. Sorry the images are terrible but they are just proof of concept images. Can't wait for good seeing now.
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Frank

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Re: PST Mod Complete

Post by marktownley » Sun Mar 15, 2015 3:58 pm

Looking a good start! When the weather allows try rotating the etalon assembly you will find there is an optimum position for it relative to the optical axis.
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Re: PST Mod Complete

Post by seti_v2 » Sun Mar 15, 2015 4:05 pm

I didnt even think of that. Great suggestion! Im sure that the lenses in the etalon assembly arent perfectfully orthogonal. I will have to do that for sure!
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Re: PST Mod Complete

Post by marktownley » Sun Mar 15, 2015 4:07 pm

Another tip to improve things in terms of squaring up, try and get an adapter to allow you to connect the male m56 thread on the end of the skywatchers focuser to the female sct thread in the secondary focuser.
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Re: PST Mod Complete

Post by swisswalter » Mon Mar 16, 2015 5:12 am

Hi Steve

a good start. Now starts the real modding job
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Re: PST Mod Complete

Post by bandazar » Wed Mar 18, 2015 11:52 am

Thanks.. did not know about the rotating trick for the PST mod. It helped a little. Still don't like the banding/sweet spot issue of the pst mod. But for right now it will do until I can afford something more expensive.

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Re: PST Mod Complete

Post by swisswalter » Wed Mar 18, 2015 4:17 pm

Hi Bandazar

more expensive may not mean "more" better ;)
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Re: PST Mod Complete

Post by marktownley » Wed Mar 18, 2015 8:21 pm

we can improve the results from this setup a bit more yet: Are you using a barlow lens on the nose of the camera? This will reduce the size of the sweetspot. The image above is offband, which, to me, suggests excessive tilt somewhere in the system - probably focuser or connecting joints between the various components...
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Re: PST Mod Complete

Post by seti_v2 » Wed Mar 18, 2015 8:30 pm

I am not using a barlow. If it will help than I will definitely put one on. I did find some excessive tilt in the focuser to etalon nosepiece and have corrected that. It was tilted about 3ish degrees. I also need to tweak the etalon position I think a little.

But unfortunately I have about 5 days of rain ahead of me so here's looking for fun in the sun next week!
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Re: PST Mod Complete

Post by marktownley » Wed Mar 18, 2015 9:07 pm

You definitely need to be using a barlow! All excessive tilt needs to be reduced to zero for best results...
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Re: PST Mod Complete

Post by MapleRidge » Thu Mar 19, 2015 12:05 pm

Congrats on the new mod and first light.

These mods work very well...just need some fine tuning now. Look forward to seeing more results.

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Re: PST Mod Complete

Post by seti_v2 » Fri Mar 20, 2015 1:40 am

My etalon is placed too far inside focus. My diagonal takes up too much back focus. Does anyone know what the thread size is on the PST blocking filter? I need to figure out how to place them inline instead of threaded on the diagonal.

Even so here are some of the images I got today. I think this is a good start either way!
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sun_153054_g3_ap119 colorize.jpg
sun_152003_g3_ap25 colorize.jpg
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sun_155026_g3_ap187 colorize.jpg
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Re: PST Mod Complete

Post by swisswalter » Fri Mar 20, 2015 5:16 am

Hi Frank

that is a good start. to reach the -200 mm you can always add a 2" extension tube. I cant help on the threads of the blockingfilter housing
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Re: PST Mod Complete

Post by Merlin66 » Fri Mar 20, 2015 5:21 am

I think from memory it's a M35 thread.
Good images there, but I don't know if it's the stacking/ processing or optics somewhere, but there seems to be some astigmatism - looks for the extended linear features...those are artifacts.
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Re: PST Mod Complete

Post by seti_v2 » Fri Mar 20, 2015 1:11 pm

Just measured the thread. I got M33x0.75 if anyone is curious. I'll have an adapter made up to get the filters inline and ditch the diagonal. It is a really cheap diagonal and may be a cheap prism instead of a dielectric mirror. That may be adding astigma as well.

Keep your fingers crossed!
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Re: PST Mod Complete

Post by swisswalter » Fri Mar 20, 2015 3:32 pm

Hi Frank

I will, good luck
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Re: PST Mod Complete

Post by seti_v2 » Fri Mar 20, 2015 11:42 pm

Well i bored out a 2 to 1.25 inch adapter to fit the itf and blocking filter. So everything is inline now. And i checked and my diagonal is definently a prism and may have been adding a little astigmatism.

Now i just need clear skies and i should be set!
Frank

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Re: PST Mod Complete

Post by seti_v2 » Wed Apr 01, 2015 1:35 pm

Got rid of the diagonal and got the itf and blocking filter inline. Brief sun and poor seeing but my imaging is getting better.
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Re: PST Mod Complete

Post by swisswalter » Thu Apr 02, 2015 4:26 am

Hi Frank

you move in the right direction
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

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