150mm PST mod with a replacement collimating lens

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robert
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150mm PST mod with a replacement collimating lens

Post by robert » Sat Feb 14, 2015 5:37 pm

I have had this Celestron 150mm FL1200mm second-hand scope since 2010 and have tried a few things with it. I eventually settled on cutting the tube a bit shorter (5cm I think) and using the PST etalon at approximately 200mm back from the focal plane of the objective.
_2143497.JPG
The 110mm diameter ERF is in the tube at the appropriate point to allow full use of the 150mm objective.
_2143499.JPG
It all worked quite well but people on the forum pointed out that the scope was f8 and the etalon collimating lens was designed for f10. As it seemed to work I just carried on using it until Neo posted his clear and simple instructions for his mod. I decided to copy his idea.
http://solarchat.natca.net/viewtopic.php?f=9&t=14315
The lenses available did not include f -160mm and 25mm diameter which is what was needed but f -150mm is available from Laser 2000 in the UK.
Coated 25mm diameter plano concave f-150mm lens
http://www.laser2000.co.uk/os_product.php?no=5334

It occurred to me that the f10 version was using the light from only part of the objective, the 120mm diameter area on the diagram. To get the resolution benefit of the full aperture it needed this mod. However the hatched annulus would not just be unused light as I first thought, it would find its way into the etalon and be unfocused and degrade the image.
PST mod new lens Model (1).jpg
PST mod new lens Model (1).jpg (189.07 KiB) Viewed 1368 times
I set the whole thing up as carefully as I could starting by re-finding the distance to the focal plane of the objective and placing the new collimating lens (now f7.5 as f8 was not easily available).
_2143495.JPG
The results have been encouraging today and yesterday and I am hoping to get easier close-ups with better resolution. Some decent seeing would help too!.
FL1200mm image today 14th Feb
0214 col14_Feb_2015_102939_g3_b3_ap864.jpg
0214 col14_Feb_2015_102939_g3_b3_ap864.jpg (154.52 KiB) Viewed 1368 times
and FL1920mmwith barlow on the camera nose piece
0214 14_Feb_2015_110928_g3_b3_ap525.jpg
0214 14_Feb_2015_110928_g3_b3_ap525.jpg (185.88 KiB) Viewed 1368 times
I expect it is still far from perfect optically, first of all because the light cone that the etalon uses is now f7.5 which still is not an exact match for the f8 scope and also all the SA problems that were mentioned in the string after Neo's post will also be present. However I am hoping that it will be an improvement.
Any further thoughts would be appreciated, (Thanks Neo :) )
Robert
images and animations http://tinyurl.com/h5bgoso
2018 images https://www.flickr.com/photos/69734017@ ... 1234171714
2017 images http://tinyurl.com/gvk9k3k
ED80. SW200. ES127. Celestron-150mm-PST mod
LS60PT-LS60F-B1200. B600-Cak. PGR-Ch3-IMX265

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marktownley
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Re: 150mm PST mod with a replacement collimating lens

Post by marktownley » Sat Feb 14, 2015 5:59 pm

Excellent! The results speak for themselves Robert. Good to see you having fun in the sun :)
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Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

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robert
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Re: 150mm PST mod with a replacement collimating lens

Post by robert » Sat Feb 14, 2015 6:07 pm

Thanks Mark. I am not sure if I could get good results with good seeing with the old mismatched setup. I am not very scientific about it and don't want to do a direct comparison, too fiddly!
Robert
images and animations http://tinyurl.com/h5bgoso
2018 images https://www.flickr.com/photos/69734017@ ... 1234171714
2017 images http://tinyurl.com/gvk9k3k
ED80. SW200. ES127. Celestron-150mm-PST mod
LS60PT-LS60F-B1200. B600-Cak. PGR-Ch3-IMX265

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solardave
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Re: 150mm PST mod with a replacement collimating lens

Post by solardave » Sat Feb 14, 2015 6:25 pm

Wow nice images Robert good job :bow
tak 102fs solarmax40 ds es ed80 cornado 90mm filter bf10 bf 30 skynyx 2-2 mono camera lunt 2inch wl wedge lunt b1800 cak mod

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swisswalter
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Re: 150mm PST mod with a replacement collimating lens

Post by swisswalter » Sun Feb 15, 2015 6:54 am

Hi Robert

congratulations, the best filaprom pic I have ever seen, very 3D
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 :)

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Re: 150mm PST mod with a replacement collimating lens

Post by Carbon60 » Sun Feb 15, 2015 7:02 am

Very nice result, Robert. Looks like a beautiful golden Koi-carp emerging from the sun!

Stu.
Lunt LS60THa B1200 PTFT
150mm H-alpha Solar telescope with Lunt35 mod
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