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Lunt 50 with Zwo 120MC Issue

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#1 volentj

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Posted 06 August 2022 - 03:35 PM

Hi,   I am trying to image with my Lunt 50 and a ZWO 120MC.  I attached my surface detail image done in sharp cap.  The issue I am having is that the detail is on one side or the other depending how I tune my lunt 50.  Is this a scope's etalon issue or a zwo 120MC issue?  I was also wondering what  exposure ms and gain should I use for surface detail vs prominences.  I was using 0 gain 10 ms for detail and 10ms 30 gain for prominences. Thanks

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Edited by volentj, 06 August 2022 - 04:12 PM.


#2 Helen P

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Posted 06 August 2022 - 05:11 PM

I think your tuning is off.....; 

i'd first experimennt with your tuning before making any conclusions that there might be problem with the filter.

Also try and tune visual and see that yoçu can get ti right then or have the same issue.

The fact that you say that with differnt tunings one or the other side of the disk is well tuned seems to me yuo have to find the rioght tuning "in between"

Might be a sweet spot issue, but then you'd not have the phenomen you describe here.


Edited by Helen P, 06 August 2022 - 05:16 PM.


#3 MalVeauX

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Posted 06 August 2022 - 07:13 PM

Hi,

 

The issue is your tuning. It's a delicate process. Try doing it visually so that the whole disc is visible on band then put your camera on and move the disc around via slewing until the disc is in the center of the jacquinot spot (sweet spot) of on-band.

 

Very best,



#4 volentj

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Posted 07 August 2022 - 04:49 PM

I tried today fine tuning the scope and the blank spot just goes in the middle if I tune it to see all the edges.  The scope gets great views on prominence but not so great on detail.  I am good with that for the price.  I am looking for get a day star Quark Chromosphere this year and will hold of on imaging until then.  Thanks for your advice.



#5 Helen P

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Posted 08 August 2022 - 08:42 AM

I tried today fine tuning the scope and the blank spot just goes in the middle if I tune it to see all the edges.  The scope gets great views on prominence but not so great on detail.  I am good with that for the price.  I am looking for get a day star Quark Chromosphere this year and will hold of on imaging until then.  Thanks for your advice.

still sounds liek the tunign  is still a bit off...... it takes some time to practice. I know that if I detune a bit, I get the result that you describe here.

If you cannot resolve it I suggest that you contact the seller as this should not happen in the Lunt 50 and points to some fault in the system itself.
 

Questio: do you havr the smae problem visually ,

 

Since you are working with a color camera, it might also be due to that. I have no idea why, but I first experimtened photgraphy with a color camera I lent on the Lunt and also had the same wierd "bright spot " effect in that.

 

ofc I had far less experience with tuning and focusing back then so.....


Edited by Helen P, 08 August 2022 - 08:47 AM.


#6 Helen P

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Posted 08 August 2022 - 08:50 AM

As for the exposure:

 

When well tuned you can easily get both prominences and surface detail in one shot.

looking at your screen in In asicap you have to optimise for surface detail, but later on when working on the image you can bring out the proms as well.

I usually use 12-15  ms exposure, 0 gain, but with a 120MM


Edited by Helen P, 08 August 2022 - 08:51 AM.


#7 hopskipson

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Posted 08 August 2022 - 04:12 PM

I tried today fine tuning the scope and the blank spot just goes in the middle if I tune it to see all the edges. The scope gets great views on prominence but not so great on detail. I am good with that for the price. I am looking for get a day star Quark Chromosphere this year and will hold of on imaging until then. Thanks for your advice.


If you are getting the blank spot in the middle try lowering the exposure setting for the camera. This will help getting all the surface features on the disk. You can then process the images to bring out the proms.

#8 wxcloud

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Posted 09 August 2022 - 12:19 PM

I see the same in my LUNT LS 50tha. Can notice it visually also. It's really noticable with the camera. Almost to the point I don't image with it now. Visually I can kind of move the disc around to get around things a little bit. Not sure if it's a blocking filter, etalon, "sweet spot" or sensor size vs blocking filter size line up mismatch or just the nature of the beast. Am disappointed however.

I've read about the 50mm Lunt sweet spots before here and there. It's really given me pause about a potential upgrade. Also read the 50mm is really not meant for imaging. Visually as mentioned it can be kind of more easily delt with.

#9 Pictor

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Posted Yesterday, 08:18 PM

For starters, try a mono camera if you have one.  You're not going to get a color image with Ha.  

 

As for tuning, try focusing and framing as you normally do.  Then watch your histogram as you tune the pressure on the etalon.  You'll see the histogram shift to the left and eventually stop and move back to the right.  That's the point you're looking for in tuning.  

 

Edit to add: You may be oversampled a bit with that camera too.  

 

Photo taken with ASI178MM and LS50THa

2021-08-14-2008_0-CapObj_lapl5_ap23429_wavelet-PS_Small.jpg

Edited by Pictor, Yesterday, 08:26 PM.

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