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152mm PST Stage 2 Mod has Begun

Posted: Thu Oct 04, 2018 12:57 am
by Starry Jack
You all have inspired me once again and I have begun my 152mm Stage 2 mod. I am converting my 100mm PST Stage 1 into the new scope.

I have opted to go at this piece at a time while still getting value all the while and use of the scope.

I have removed the PST Black Box from the Stage 1 and created the assembly below. Yes... I am using every single adapter in my 20 year stockpile and am holding the thing together at the moment with green masking tape. I have also cannibalized the old gold tube to use as new nosepiece. The trick is to get the Baader Glasspath 1:1.7 in front of the etalon, but I will worry about that when it arrives.


-Only use one scope for both Solar and DSO; this makes the use of my single mount (CGM-DX) the only mount I need.

-Build useable telescopes as money allows, but each step adding value over the prior version

1) Make the Stage 2 Mod out of my current PST 100mm f10 refractor; this allows me to lighten the PST and to test the Stage 2 mod in a known f10 scope. I can also more safely piggy-back both the 152mm and the 100mm on the same mount

2) Add the 1:1.7 Baader Glasspath to the Stage 2 mod and then use the 152mm Explore Scientific; I have a 100mm Lunt ERF which I'll have to use for now. It is only 1/4 Wave and internal, but it should still offer improvement over the 100mm f10 Stage 1

3) Acquire one of Val's Aries tri-band D-ERFs; then I can sell the Lunt 100mm ERF and have a truly convertible Day/Night scope

4) Get a bigger blocking filter. I'll need to use the standard PST BF5 until money is ready.

Does this series of goals and steps make sense?

I hope to test the Stage 2 mod in the 100mm F10 system tomorrow and order the Baader Glasspath 1:1.7 tonight.



Re: 152mm PST Stage 2 Mod has Begun

Posted: Thu Oct 04, 2018 12:58 am
by Starry Jack
FYI the 152mm is f6.5.

Re: 152mm PST Stage 2 Mod has Begun

Posted: Thu Oct 04, 2018 5:08 pm
by marktownley
Keep us updated!

Re: 152mm PST Stage 2 Mod has Begun

Posted: Tue Oct 09, 2018 10:39 pm
by Starry Jack
Thank you for the links. I'm diving into them as we speak. My 1:1.7 Glasspath did arrive today. I'll try and calculate the best spot to put the Glasspath in the nosepiece in front of the etalon. The math perplexes me a bit so I may make it a variable placement mechanism.

If anybody has an idea of where to place the Glasspath in this f6.5 system, I'm all ears.


Re: 152mm PST Stage 2 Mod has Begun

Posted: Thu Oct 11, 2018 3:12 am
by Starry Jack
Good news on the prototype. My clutter of extension tubes for the Stage 2 mod was too unwieldy for good testing so I went back to putting my Stage 1 mod into the 152mm. I used my Lunt 100mm ERF externally so I made a cardboard cell to hold the 100mm ERF and masked the 152 objective down to 100mm. I also put the 1:1.7 Glasspath right in front of the etalon.

The good news is that I was able to achieve focus without cutting the 152mm OTA. That was very exciting to me. That said, I think I did not center the Glasspath well because there is circular vignetting on one side of the solar image which is crescent shaped. Also, when I use a 2x Barlow the focus is very, very soft. Focus is pretty sharp when I don't use the Barlow.

Next step is I have made a cardboard internal cell holder and will place the 100mm ERF internally against a baffling ring. This will let me test the prototype full 152mm. I will also try and recenter the Glasspath. The downside is there will be internal air currents due to the eat dissipation from the internal placement of the ERF.


Re: 152mm PST Stage 2 Mod has Begun

Posted: Thu Oct 11, 2018 10:39 pm
by Starry Jack
More good news! The internal mounted ERF also works well and reaches focus with and with out an ext3rnal Barlow on the camera. The Barlow is still super soft focus but the non Barlow image in the 152 is superior to the 100mm. Nothing looks like what you pros shoot but we are making great strides.


Re: 152mm PST Stage 2 Mod has Begun

Posted: Sat Oct 13, 2018 1:05 pm
by MalVeauX
Sounds cool Jack!

How about some images of your cardboard cells and where you internally placed the ERF?

Very best,

Re: 152mm PST Stage 2 Mod has Begun

Posted: Sat Oct 13, 2018 1:17 pm
by Starry Jack
Here is the external cell. Blocks lick it in to place. The old 100mm is riding on top.

I then cut up this cell to 150mm and placed it on the third bafffle about 12 inches into the OTA (No photos).

The good news is my DERF from Val should be shipped next week then I will have a superior piece of glass, filtration and external mount. Much of my work is based on rapid prototype to see if the concept works then I clean it up later.