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Help with Double stacking a Quantum SE 0.6 A and Coronado PST

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#1 gicashut

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Posted 24 January 2023 - 10:03 PM

Hello,

I need help with making the double stack work, I am using a AR152 - Explore Scientific with Moonlite Focuser and M68 to 2" visual back, I am using a Apollo Max 432 camera and a ZWO 174.

I can't achieve focus, I added the PST in front of the camera and I got close to focus but it was like looking through a keyhole, only 10% of the image was working, I have tried to move into the focuser and in front of the Quantum and nothing,

I am trying this setup tomorrow. I am also using a Altair ERF filter in front for energy rejection.

Suggestions welcomed smile.gif

Attached Thumbnails

  • imaging-train.jpg

Edited by gicashut, 24 January 2023 - 10:03 PM.


#2 JerryStellar

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Posted 24 January 2023 - 10:40 PM

good luck… keep digging in our forums. It has been awhile but I do remember finding some help there. Below is one of the few YouTube videos I found. The gentleman in this video describes in detail how he achieved focus. It is old but still has relevant backfocus discussion. 

 I to own a PST… I bought it a few months ago to catch some upcoming sun activity…I did not research the scopes ability with astrophotography before doing so lol. 

  Obtaining enough focuser racking distance to reach the focal plane is a major hurdle with PST’s. The few posts I found were successful using a Mini ASI120…most cameras need more racking distances… 

  Good luck. I’ll follow along because I am also still in a quandary myself!

 

jerry 

 

https://www.google.c...SpSC6e87u7sNrJ1



#3 hopskipson

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Posted 24 January 2023 - 10:52 PM

If I had to guess I think the diagonal is making your imaging train too long. Not sure if it’s okay to discuss the pst mod here.

#4 gstrumol

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Posted 24 January 2023 - 11:15 PM

That has got to be some Borg-like assimilation, because I have a PST and I can't recognize a single bit of it in that picture! Must not be in the frame ...



#5 gicashut

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Posted 24 January 2023 - 11:40 PM

That has got to be some Borg-like assimilation, because I have a PST and I can't recognize a single bit of it in that picture! Must not be in the frame ...

the PST is the first etalon on the right, it's the PST etalon removed from the scope:)



#6 gicashut

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Posted 24 January 2023 - 11:41 PM

good luck… keep digging in our forums. It has been awhile but I do remember finding some help there. Below is one of the few YouTube videos I found. The gentleman in this video describes in detail how he achieved focus. It is old but still has relevant backfocus discussion. 

 I to own a PST… I bought it a few months ago to catch some upcoming sun activity…I did not research the scopes ability with astrophotography before doing so lol. 

  Obtaining enough focuser racking distance to reach the focal plane is a major hurdle with PST’s. The few posts I found were successful using a Mini ASI120…most cameras need more racking distances… 

  Good luck. I’ll follow along because I am also still in a quandary myself!

 

jerry 

 

https://www.google.c...SpSC6e87u7sNrJ1

It's easy enough to image with the PST, i just want to create a double stack, here's my old double stack, Coronado 90 and Quark Gemini, this is my video:)

 

https://www.youtube....h?v=FXYzZppEHhg



#7 ch-viladrich

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Posted 25 January 2023 - 04:39 AM

Just to make sure : have you removed the collimating lenses of the PST or not ?


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#8 gicashut

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Posted 25 January 2023 - 11:20 AM

do I need to remove the front collimation lens and push that forward into the tube? to get focus? by 100mm or so?

#9 gicashut

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Posted 25 January 2023 - 11:20 AM

i’ve removed the pst with the collimation lenses attached

#10 gicashut

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Posted 25 January 2023 - 11:44 AM

Just to make sure : have you removed the collimating lenses of the PST or not ?

i have I am testing with the front collimation lens away from the etalon (I bought the extension tube from lacerta) here's the most recent image

 

https://drive.google...R-B?usp=sharing



#11 ch-viladrich

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Posted 25 January 2023 - 01:00 PM

Could you give us a little more details on the setup ?

 

Do you have a Barlow lens (or better a telecentric lens) somewhere to reach the f/30 required your DayStar 0.6 A ?

 

Basically, the setup should be : telecentric lens (f/28 to f/35), then DayStar and PST etalon (you can also have the PST etalon in front of the DayStar etalon). For this, you have to remove the divergent collimating lens in front of the PST etalon, as well as the convergent imaging lens after the PST etalon. So, both the DayStar and the PST etalons will be in a telecentric beam.



#12 gicashut

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Posted 25 January 2023 - 10:56 PM

Could you give us a little more details on the setup ?

 

Do you have a Barlow lens (or better a telecentric lens) somewhere to reach the f/30 required your DayStar 0.6 A ?

 

Basically, the setup should be : telecentric lens (f/28 to f/35), then DayStar and PST etalon (you can also have the PST etalon in front of the DayStar etalon). For this, you have to remove the divergent collimating lens in front of the PST etalon, as well as the convergent imaging lens after the PST etalon. So, both the DayStar and the PST etalons will be in a telecentric beam.

I use a Powermate 4x, AR152

 

I will remove both lenses and see what happens.



#13 MalVeauX

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Posted 26 January 2023 - 07:40 AM

Hi,

 

Spacing can matter; your powermate is a pseudo-telecentric, I'm not sure what the registration distances are but a true telecentric will have specific placement needs on both ends typically. One thing to start is you probably need to get that diagonal out of there, it's not helping and it's just adding around 100~110mm of distance to the imaging train that isn't needed. Your imaging train with those etalons, no matter what they are, should be the energy rejection system pre-filtering -> telecentric amplifier -> etalon 1 -> *** -> etalon 2 -> *** -> Camera (no reducer with your IMX432). The *** are place holders for where you could put a blocking filter, but your blocking filter is built into your Quantum's stack, so it is effectively in the first *** position anyways. But again you need to get the distances right. Odds are, you probably just have the camera too far away for focus due to the diagonal.

 

Very best,



#14 Dennissloan

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Posted 26 January 2023 - 10:03 AM

Greetings
My DS arrangement is using either Coronado 90 or 60 etalon serving as the ERF , 2x Powermate , scope and Daystar.3AQPE . The system works great . Due to my seeing conditions, the pre-Meade Coronado 60 is used most often.

#15 gicashut

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Posted 28 January 2023 - 10:54 PM

I am gonna use a Lunt 40mm etalon and double stack that with my Daystar, probably use with my 90mm refractor and 4x powermate more, the seeing I need for a 152mm is pretty rare. The PST etalon just doesn't work at all, not sure why, even with my smaller 90mm refractor




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