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Lunt Double Stack on the CR-150...comments please

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Lunt Double Stack on the CR-150...comments please

Post by MapleRidge » Thu Aug 22, 2013 8:47 pm

Hi everyone...

I have been wanting to go to a narrower bandpass on the modded scope, but had limited success. I tried the PST etalon behind the DSII module, but was not getting results that warranted more time. I returned form holidays last weekend and decided I would have an adapter machined to fit the primary etalon from the LS80 at the rear of the CR-150, and have the option to mount the DSII module as a true double stack.

First light was yesterday over the noon hour...seeing was poor and I was clouded out part way through the image capture. I have SS and DS images taken along the NW and Western limb...my eastern SS run was clouded out before completing the same FOV as the DS. I have posted a pair of single and double stack images below...trying to get the same general FOV in each.


above is single pass, DS below



above is single pass, DS below


So, based on the pics would anyone care to comment on what, if any bandpass reaction was achieved? The DS look smoother here, but I ran the same sharpening routine on all (short on time today), and I really need to run a session in better seeing as well.

Below is a few pics of the primary etalon mounted in the focuser housing and the DS assembly on the scope:



Thanks,
Brian
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Re: Lunt Double Stack on the CR-150...comments please

Post by marktownley » Thu Aug 22, 2013 9:00 pm

I'm liking those double stack results Brian! They work well 8) More please ;)
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Re: Lunt Double Stack on the CR-150...comments please

Post by swisswalter » Thu Aug 22, 2013 9:12 pm

Hi Brian

great results, great mod
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Re: Lunt Double Stack on the CR-150...comments please

Post by Pablito » Thu Aug 22, 2013 9:37 pm

Great mod. I was thinking about it for a long time but nobody sells DSii module.
Is there just internal ERF or you used front ERF?

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Re: Lunt Double Stack on the CR-150...comments please

Post by MapleRidge » Thu Aug 22, 2013 10:22 pm

Thanks for your encouragement everyone :bow:

To me, the DS images are a bit more contrasty, but I am not seeing the improvement I would have hoped if the bandwidth were truly reduced. I will have to wait for a clear day to do a few more test images.

The DSII modules are scare on the used market :( I've been looking for some time and only ever saw one. You can get a new one through Lunt, but it usually takes time. I believe I less pronounced 'sweet spot' using the primary etalon, but flats are still needed to clean up the vignetting (these posted frames were not flatted).

I did not mention the ERF in this post, but had covered the internal Baader 110mm ERF in a post a month or so back.

Take care,
Brian
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Re: Lunt Double Stack on the CR-150...comments please

Post by Allcart » Thu Aug 22, 2013 10:42 pm

Firstly let me say that I'm surprised that the primary connects straight to the rear of the CR6. When I mount my LS60 behind my scope it is much farther away. I know the optimal distance will not be the same for the two lunts, but nonetheless, I'm quite surprise.
I'm even more surprised that it works so well Brian. :thumbsup:
I don't know what bandpass was achieved, but the DS looks better than the SS. To me, closeups with a DS always look softer and fluffier than the SS, if you know what I mean.

I can see sales of CR6's and Lunt 80's increasing rapidly. That is one helluva good mod.
Allan

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Re: Lunt Double Stack on the CR-150...comments please

Post by RobBower » Thu Aug 22, 2013 10:59 pm

Really great work Brian! Glad to see you decided to do the mod! :hamster:
The results speak for themselves! Its a win win I believe! :bow:
If I can still buy a new one.....Im not afraid to rip this 1 apart!



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Ls60pt/Ls50DS, Lunt 2" HW, PGR Flea3-DMK51

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http://www.flickr.com/photos/98998648@N07/

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Re: Lunt Double Stack on the CR-150...comments please

Post by colmic » Thu Aug 22, 2013 11:16 pm

These are great images, but i'm not impressed by the real improvment of this DS, sorry to tell you that, but in my opinion, you can have better than that. Take a look at my SS and DS stacks

SS Solarmax90 (given for about 0.7A):



And DS Solarmax90 + PST etalon:

Same day (first day i tested it, not well adjusted)):


and well adjusted (a spectroheliograph user told me images reach less than 0.5A):


and close-up at in my opinion the best ajustment:


And finaly, PST with the D-ERF135mm (given to be about 1.0A but i think it's more below that):



I suppose you adjusted well the 2 etalons? Double stack is difficult to adjust.
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Takahashi TSA120 on Vixen Sphinx NexSXD
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Re: Lunt Double Stack on the CR-150...comments please

Post by MapleRidge » Fri Aug 23, 2013 12:27 am

Hi Michel...

Those are great images, and make an excelled reference :bow: I agree that I believe that this system could do more...and this was first light mainly trying to confirm that it would come to focus in single and DS modes. One thing I neglected to mention is that I have a lead in the PT on the DSII module, as it slowly looses pressure causing the band to drift. I have replacement parts from Lunt, but not had time to fix yet. This will have thrown off the tuning. What effective focal length had you used for the close-ups you posted? I will try going more than the 2.5x that I have been using to see if a bit more image scale will help. I'm not sure if this plays a role or not, but the ERF is still installed on the primary etalon...earlier DS arrangements with the LS75FHa in front of the LS80 worked fine...may have some internal reflections :?

Allan...the LS80 primary etalon is a close fit to the Synta flange on the CR-150, but I had to have a flange made to make a proper fit and adapt the etalon's threaded body to the donor scope. The mod looks promising, but it is rather expensive...still far less $$$ than a LS152 + no DS option :ohmy: You could likely do the same with a LS60PT on many scopes around f7 and make a very sharp Ha instrument.

Rob, thanks for you comments. I took the scope apart on Monday after imaging and took the etalon to the machinist to see if he could make the threaded adapter...our discussion about mods on Sunday was still fresh in my mind and I decided to go for it :lol:

Thanks everyone.

Brian
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Re: Lunt Double Stack on the CR-150...comments please

Post by RobBower » Fri Aug 23, 2013 12:46 am

I love ripping stiff apart Brian! :hamster:
I may still do the lunt60 on my meade 127 but ill need you and John to teach me mosaic work! Not likely to shoot full disk at 950mm
If I can still buy a new one.....Im not afraid to rip this 1 apart!



Island Grove Observatory on the south shores of Lake Simcoe

Ls60pt/Ls50DS, Lunt 2" HW, PGR Flea3-DMK51

Meade 127mmED Triplet NEQ6 Pro

127mm PST mod. 950mm Meade Series 5000 Triplet

http://www.flickr.com/photos/98998648@N07/

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Re: Lunt Double Stack on the CR-150...comments please

Post by colmic » Fri Aug 23, 2013 11:30 pm

I usaually shoot with my Televue 1.8x Barlow on my TOA (1000FL) and 4.54µm pixels on the Grasshopper3.

I tested with Powermate 2.5x but not better.
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Takahashi TSA120 on Vixen Sphinx NexSXD
Coronado SM90 Double stack (type I) + BF15
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Re: Lunt Double Stack on the CR-150...comments please

Post by Derek Klepp » Sat Aug 24, 2013 8:40 am

Brian I agree there should be more of a difference between the two.I look foward to your progress here.
Cheere Derek

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Re: Lunt Double Stack on the CR-150...comments please

Post by etatsolarchat » Sun Aug 25, 2013 1:39 am

Well an obvious difference would be the $500 vs $7500 refactor you think :?

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Re: Lunt Double Stack on the CR-150...comments please

Post by MapleRidge » Mon Aug 26, 2013 12:59 am

I agree the optical quality will have an effect, but far more in a broader spectrum filter set up like the WL images. Alexandra's hi-res granulation images are one that comes to mind immediately. With the narrow bandpass in the Ha, the need for expensive APO optics is less critical...lots of examples here form modded scopes using achromats.

My query to Michel about his setup was more to get a handle on the image scale...not to compare the image quality. The overall question I had was if people here could honestly say there was a 'significant' reduction in bandpass...no access to any testing facilities, so an experienced opinion does me a world of good.

I am processing a second run on the DS setup (after some adjustments post first light)...will post when time allows.

Thanks again everyone,
Brian
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Re: Lunt Double Stack on the CR-150...comments please

Post by RobBower » Mon Aug 26, 2013 1:05 am

I see quite a difference. The sharpness of the single stacked is gone in the doubles. And the softer details are much more obvious in the DS images. The rest is seeing and processing!
I think youre in the zone. Just tweaking and good sky will be the answer!

But hey.... What do I know? Lol

Oh yeah my erf is almost here then the mod is done!
Thanks for your help Brian!
If I can still buy a new one.....Im not afraid to rip this 1 apart!



Island Grove Observatory on the south shores of Lake Simcoe

Ls60pt/Ls50DS, Lunt 2" HW, PGR Flea3-DMK51

Meade 127mmED Triplet NEQ6 Pro

127mm PST mod. 950mm Meade Series 5000 Triplet

http://www.flickr.com/photos/98998648@N07/

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Re: Lunt Double Stack on the CR-150...comments please

Post by colmic » Mon Aug 26, 2013 8:49 am

Yes, my answer was not about the optical quality or the quality of my images vs Brian, there is not the goal here and there is no competition :)
My answer was only about the bandpass and the gain with the double stack. And I'm very surprised that the difference is not better. For myself, difference between SS SM90 and DS with PST etalon is enormous!

Ps: i bought all my setup on the second-hand market, TOA, EM200, SM90, PST, must cheaper than $7500 lol!

How many costs all this modification Brian?
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Takahashi TSA120 on Vixen Sphinx NexSXD
Coronado SM90 Double stack (type I) + BF15
Intes Hershel prism
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Re: Lunt Double Stack on the CR-150...comments please

Post by RobBower » Mon Aug 26, 2013 7:07 pm

Michel you got a great deal! Ive seen your set up in images you have posted and seen the images you have taken! You really have got it all there! Great results indeed! :bow:
If I can still buy a new one.....Im not afraid to rip this 1 apart!



Island Grove Observatory on the south shores of Lake Simcoe

Ls60pt/Ls50DS, Lunt 2" HW, PGR Flea3-DMK51

Meade 127mmED Triplet NEQ6 Pro

127mm PST mod. 950mm Meade Series 5000 Triplet

http://www.flickr.com/photos/98998648@N07/

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Re: Lunt Double Stack on the CR-150...comments please - ipload in progress

Post by MapleRidge » Thu Aug 29, 2013 8:11 pm

Hello everyone...

Here is my second go at the Lunt double stack using the pressure tuned etalons. There were taken on Friday (Aug 23rd) during the mid morning here, with better seeing than my first light attempt.

The only comparison between singe and double stack were taken at prime focus.

Examples posted below:
These images cover the eastern limb through the mid disk area:

Single stack above, double stack below:


and these two cover the western portion of the disk:


Single stack above, double stack below:


At prime focus (1200mm), the sweet spot is quite evident, but there is a good increase in contrast in the DS images when examining the filaments and bright faculae in the images.

I added the 2.5x barlow to the DS mode for closer examination of the AR's, filaments, and proms:









The second light session had the primary etalon positioned better (square to optical axis), which I feel has improved the images a bit. The DS mode worked well at 2.5x, but when I ran a longer barlow the exposures became too long for my seeing that day. Still, I'm not un-happy with the setup...just working on the fine tuning.

The camera used was the PGR IC674 chipped Grasshopper Express (Firewire) camera.

I welcome any additional comments and criticisms of the project ;) .

Thanks,
Brian
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Re: Lunt Double Stack on the CR-150...comments please - ipload in progress

Post by marktownley » Thu Aug 29, 2013 8:27 pm

are you using a big chip camera here Brian?
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Re: Lunt Double Stack on the CR-150...comments please

Post by Pablito » Thu Aug 29, 2013 8:40 pm

Did you try to rotate outer etalon?

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Re: Lunt Double Stack on the CR-150...comments please

Post by MapleRidge » Thu Aug 29, 2013 8:56 pm

Hi Mark and Pablito...

Just a quick follow-up on your questions:

The camera is my standard PGR Grasshopper Express with the ICX674 chip (on the larger side). I could have cropped or used a sub-frame, but kept the full FOV for perspective.

Etalon rotation is limited...primary etalon by the threads which mount it to the OTA, and DSII module is set to keep the focuser assembly from interfering with the camera attached to the scope on the side x side plate. I can do a test on this next clear day.

Brian
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Re: Lunt Double Stack on the CR-150...comments please

Post by Valery » Tue Mar 25, 2014 5:55 pm

MapleRidge wrote:Hi Mark and Pablito...

Just a quick follow-up on your questions:

The camera is my standard PGR Grasshopper Express with the ICX674 chip (on the larger side). I could have cropped or used a sub-frame, but kept the full FOV for perspective.

Etalon rotation is limited...primary etalon by the threads which mount it to the OTA, and DSII module is set to keep the focuser assembly from interfering with the camera attached to the scope on the side x side plate. I can do a test on this next clear day.

Brian

Hi Brian,

Thanks for your letter to me. And I spent a few minutes and find this your report you mentioned in the letter.

" I can do a test on this next clear day. "

Can you show us your further results?


Thanks,


Valery.
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Re: Lunt Double Stack on the CR-150...comments please

Post by MapleRidge » Tue Mar 25, 2014 11:06 pm

Hi Valery...

This system is not in use now...I was not able to mount the primary LS80T etalon firm enough in the donor OTA to keep it for flexing and not risking it falling out of the adapter. I could have had a better threaded aluminum adapter made up, I wanted to have the LS80T fully functional and picked up a used Daystar 0.45A filter soon after to give me the narrow bandpass I was after.

The current system only uses the DSII module in the modded scope...it is the only PT element in the pics I sent you.

Let me know if you have any questions,
Brian
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Maple Ridge Observatory

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