pst mod experimentation

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bandazar
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pst mod experimentation

Post by bandazar » Sat Mar 07, 2015 1:02 pm

Not sure why, after having tried the PST mod that I bought from someone on here, it appears my smallest scope that I have shows the best images.
The best combination I have produces images similar to that of a coronado 90mm II front unit with bf15... although the pst unit does have some banding sweetspot issues. But it is not terrible.
What I'm using is a 90mm f5.6 apogee achro with native focuser removed. I put in a helical focuser, then a 1.7 baader gpc, then the pst etalon unit, then afterwards a 2" barrel, then the bf15, then a 1.25 extension tube, then a .5 atik reducer, then an eyepiece.
The image is small, and if I move the eypiece further from the atik .5 reducer it gets smaller, but the image gets better of course.
Compare this with a 120ed skywatcher f7.5 apo, where I made front adaptor for my front ERF which measures about 96mm. Since the skywatcher apo has a focal length of 950mm, this is roughly close to f10. I put in the eyepiece, and although I do see h-alpha features, I get sort of a tiny sweetspot effect, where the best image is a very small area.
I tried without the front ERF as well, very early in the morning to avoid heat damage in both the 150mm f/5 achro that I have and the 120mm apo full aperture, and got worse results.

Maybe it has something to do with where the pst is in the lightpath of the scope. I'm not about to cut my tubes to find out though.

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swisswalter
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Re: pst mod experimentation

Post by swisswalter » Sat Mar 07, 2015 4:11 pm

Hi Steven

welcome to that wonderful site. Have fun in the SUN.

You'll get soon tons of good ideas how to improve your mod(s). Did you order a script from ken ? It is almost a must ;)
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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from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

bandazar
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Re: pst mod experimentation

Post by bandazar » Thu Mar 12, 2015 1:39 pm

Okay, I have put the pst on the inside of the focuser of my 120mm apo and 150mm achro and the pinhole effect has disappeared. But still the image is nowhere as good as my 90mm achro solution.
So positioning is important, but not sure why the image is still bad. Even when putting a 96mm erf in front of the 120mm skywatcher apo with a homemade aperture mask to produce an f/10, the image was still not as good as the f/10 produced in the 90mm f5.6 apogee achro with 1.7 baader gpc in front (to produce an equivalent f/10).

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Re: pst mod experimentation

Post by marktownley » Thu Mar 12, 2015 4:02 pm

When you sat not as good, in what way? Can you post a picture of the scopes with the etalon unit etc in place so we can get a better idea of what is going on?
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Re: pst mod experimentation

Post by bandazar » Thu Mar 12, 2015 4:53 pm

The detail was just not as great. Especially the surface detail. Maybe things were not quite as square because I used black duct tape to attach the etalon to the tube.
I'll maybe post pictures later. Though I just may sell my setup and go for something larger eventually.. not 100% sure yet.

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swisswalter
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Re: pst mod experimentation

Post by swisswalter » Thu Mar 12, 2015 7:33 pm

Hey Hey hey

we like to help you very much, but if you are on the way to sell the setup, it is not much fun to discuss your problems
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

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

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Re: pst mod experimentation

Post by bandazar » Thu Mar 12, 2015 9:51 pm

Here are some pictures of what I got. Maybe I won't sell for right now. I want to get a good at least 150mm solar setup. But have not decided which way to go. I don't like the banding/sweetspot of the pst mod to be honest and don't like the electronic system by the daystar system. Nor did I like the weight or cost of the lunt 152mm...
so for right now I will wait until something good comes along.
Attachments
PIC_0003.JPG
the skywatcher 120ed apo I used for testing at f/10 with the pst mod. Used the same front erf that I used with the achro. I used both with and without the ERF to be honest..
PIC_0002.JPG
front erf
PIC_0001.JPG
The achro, duct tape keeps the front filter in place. BF15 with 1.7 gpc with pst mod

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swisswalter
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Re: pst mod experimentation

Post by swisswalter » Fri Mar 13, 2015 5:21 am

Hi Steven

the ERF can't be the culprit, even if it is looked at place with a duct tape
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

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

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Re: pst mod experimentation

Post by marktownley » Fri Mar 13, 2015 6:45 am

bandazar wrote: Compare this with a 120ed skywatcher f7.5 apo, where I made front adaptor for my front ERF which measures about 96mm. Since the skywatcher apo has a focal length of 950mm, this is roughly close to f10. I put in the eyepiece, and although I do see h-alpha features, I get sort of a tiny sweetspot effect, where the best image is a very small area.
I tried without the front ERF as well, very early in the morning to avoid heat damage in both the 150mm f/5 achro that I have and the 120mm apo full aperture, and got worse results.

Maybe it has something to do with where the pst is in the lightpath of the scope. I'm not about to cut my tubes to find out though.
Are you still using the glasspath corrector with the larger scopes?
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

bandazar
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Re: pst mod experimentation

Post by bandazar » Fri Mar 13, 2015 7:40 am

with the 150mm xlt omni r, yes, I use the glasspath corrector. With the 120ed skywatcher no.
The issue with the omni is that with the .5 atik reducer, the image becomes as small as the PST unit or even a little smaller. basically I have to find a lot of extension tubes I suspect to get a good image size to determine whether or not the image is good. The focuser on the 150mm xlt is also much shorter than the 120ed so that I can only move it so much. It does not help that duct tape also interferes with movement.

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Re: pst mod experimentation

Post by marktownley » Fri Mar 13, 2015 9:21 am

Simples, don't use the 0.5x reducer, you won't successfully get it to work with a PST mod it will just accentuate the sweet spot. With the other scopes if you cannot get the etalon in the position it needs to be you will not get a good image.
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

bandazar
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Re: pst mod experimentation

Post by bandazar » Fri Mar 13, 2015 1:30 pm

If I had the extension tubes to do that, I would not have used the .5 atik reducer. But I just might switch out the focuser in the 120ed with the one in the 150 omni xlt to see if that gives me enough travel along with what extention tubes I have to reach focus. If not, then I'll just have to order more extension tubes..

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