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Double stacking is where the magic is

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#1 GOLGO13

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Posted 06 May 2021 - 09:14 AM

I got my 50mm double stack for the 50mm Lunt. Big difference! I mean, the view before double stacking is not bad. But I'd say an increase of 30-40% (or more) with the double stack. That's why I wanted to ensure I double stack and had to go with the 50 in order to do so.

 

It's a heavy little sucker, but it actually makes the balance a bit better on the mount.

 

This setup appears to work quite a bit better than the previous setup I had in terms of usage. I had a Coronado double stack with two Etalons married together. And two tilt tuners (one on each). There were a lot more ghost suns to deal with. But it still worked OK. Just seems like this one is a bit better. Maybe because of the one being internal pressure tuned and the other being the external.

 

Below was my old setup:

 

Coronado doublestack

 


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#2 GOLGO13

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Posted 06 May 2021 - 09:18 AM

Here's the new setup with the double stack on it.

 

lunt50 double

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#3 afrancis

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Posted 06 May 2021 - 09:53 AM

Most likely user error but this morning's experience was quite opposite. I've only had the 50 for a few weeks and just received the DS. Had it out this morning and in SS mode I could see one tiny prom. When I added the DS the image darkened quite a bit and the prom disappeared. Ran the DS tuner through the limits but nothing. I eventually removed the DS and the image brightened and the prom popped back into view. This is new to me, when you add the DS do you have to readjust the pressure tuner also?



#4 GOLGO13

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Posted 06 May 2021 - 10:05 AM

Al,

 

Check your DS unit (doesn't have to be attached) and run the tuner up and down a bit. Look to see if the gap gets larger close to where the tuner is. 

 

As that tilts the etalon it should brighten up a bit. It's probably not going to be as bright as single, but it should be quite nice.

 

Possibly it just wasn't opening up as expected. 

 

For your question, I believe you first set it up to optimal settings for single stack, then add the double stack (rebalance the scope on the mount obviously). Then adjust the tilt of the etalon using the tilt tuner. 

 

Just check the DS etalon visually looking at it to ensure the tilting is occurring.



#5 rigel123

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Posted 06 May 2021 - 10:06 AM

Most likely user error but this morning's experience was quite opposite. I've only had the 50 for a few weeks and just received the DS. Had it out this morning and in SS mode I could see one tiny prom. When I added the DS the image darkened quite a bit and the prom disappeared. Ran the DS tuner through the limits but nothing. I eventually removed the DS and the image brightened and the prom popped back into view. This is new to me, when you add the DS do you have to readjust the pressure tuner also?

You should tune your scope as best you can in SS mode first.  Could you see any of the filaments on the disk as well as that small prom in SS mode?  If not, then you probably were not on band.  They may have been faint but should have been visible in SS mode if you were on band.  Then you add your DS unit and simply use the tilt tuner to just move the "ghost" image off of the real image.  If you don't see a "ghost" image when adding your DS unit you are most likely not on band in SS mode and may be why the prom was much brighter.  It will dim but it should still be visible after adding your DS unit.



#6 BYoesle

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Posted 06 May 2021 - 10:13 AM

This setup appears to work quite a bit better than the previous setup I had in terms of usage. I had a Coronado double stack with two Etalons married together. And two tilt tuners (one on each). There were a lot more ghost suns to deal with. But it still worked OK. Just seems like this one is a bit better. Maybe because of the one being internal pressure tuned and the other being the external.

 

Well, one-off comparisons are difficult to make hard and fast rules about. First thing I note is the Coronado's appear to be 40 mm, and a 10 mm diameter increase at this aperture is significant. Having an internal pressure tuned etalon makes adjustments significantly easier. And lastly, if these were Meade Coronado etalons - well lets just say there is a considerable level of performance variance that can take place compared to the original Tucson and Isle of Mann Coronado filters.

 

I've only had the 50 for a few weeks and just received the DS. Had it out this morning and in SS mode I could see one tiny prom. When I added the DS the image darkened quite a bit and the prom disappeared. Ran the DS tuner through the limits but nothing. I eventually removed the DS and the image brightened and the prom popped back into view. This is new to me, when you add the DS do you have to readjust the pressure tuner also?

 

No you do not have to readjust the pressure tuning to double stack - provided you are on-band to begin with the PT etalon. Double stacking will always decrease the level of transmission of the filter system, making faint prominences even fainter. The transmission is the product of both of the filters transmissions. If both etalons had an 80% transmission, the cumulative transmission is 0.8 x 0.8 = 0.64 > 64%. The removal of parasitic continuum from the Sun's disc is why you double stack - and results in much greater detail from improved contrast.

 

double stacking non-norm reve graph.jpg

Click for larger.

 

So for prominences, single stacking is sometimes preferable, but for disc details, double stacking is the way to go. There are ways to improve the brightness of double stacked views, and have the best of both worlds. PM me if you are interested.

 


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#7 afrancis

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Posted 06 May 2021 - 10:20 AM

Al,

 

Check your DS unit (doesn't have to be attached) and run the tuner up and down a bit. Look to see if the gap gets larger close to where the tuner is. 

 

As that tilts the etalon it should brighten up a bit. It's probably not going to be as bright as single, but it should be quite nice.

 

Possibly it just wasn't opening up as expected. 

 

For your question, I believe you first set it up to optimal settings for single stack, then add the double stack (rebalance the scope on the mount obviously). Then adjust the tilt of the etalon using the tilt tuner. 

 

Just check the DS etalon visually looking at it to ensure the tilting is occurring.

Yes, the tilt appears to work correctly. And as you and Warren pointed out, I tuned in SS mode first and although I could see the prom, perhaps I was not on band? I don't recall seeing a ghost image when I added the DS. It will probably be next week until I have an opportunity to give it another try. Thanks guys for the help! 



#8 GOLGO13

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Posted 06 May 2021 - 10:20 AM

Well, one-off comparisons are difficult to make hard and fast rules about. First thing I note is the Coronado's appear to be 40 mm, and a 10 mm diameter increase at this aperture is significant. Having an internal pressure tuned etalon makes adjustments significantly easier. And lastly, if these were Meade Coronado etalons - well lets just say there is a considerable level of performance variance that can take place compared to the original Tucson and Isle of Mann Coronado filters.

Yes. It was the 40mm. The Coronado etalons were likely not Meade as they were pretty old. Not saying the performance was bad on the Coronado, more that the usage of setting up the tilt seems better with the new scope. Seemed like the ghost suns in the old setup was quite a bit more pronounced. It's been a year or so since I used that old setup, so it's all from memory.

 

That old setup was still good, but so far this one does seem better. To be expected somewhat, just an observation.



#9 GOLGO13

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Posted 06 May 2021 - 10:30 AM

Yes, the tilt appears to work correctly. And as you and Warren pointed out, I tuned in SS mode first and although I could see the prom, perhaps I was not on band? I don't recall seeing a ghost image when I added the DS. It will probably be next week until I have an opportunity to give it another try. Thanks guys for the help! 

I've found with the pressure tuner, I'm pretty close to all the way inward with the pressure tuner for getting on band. I think others have said to push it all the way in, then back off until it looks best. The details on the sun's surface should show up a bit. It takes a little bit of time to get used to the whole system.

 

Then after that's all good, add the double stack and adjust the tilt. That takes some getting used to also. 

 

But once you get it all figured out it can show good stuff. 

 

Precise focusing can be important also.


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#10 GOLGO13

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Posted 06 May 2021 - 10:39 AM

I should also mention there will be a sweet spot for where the details looks best. Try moving the sun around a bit to see if details pop in and out. 

 

I find this is often easiest to find using a very low power eyepiece (say 24mm). Mine appears to be mostly in the middle of the view. 


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#11 alvacouch

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Posted 07 May 2021 - 05:47 AM

I also just received the Lunt 50 DS unit after observing single-stacked for 6 months.  I have so far been following the instructions in the simple Lunt manual, which include removing the DS, tuning for details, and then putting it back on and tuning it. 

 

A newbie question: how to avoid removing the DS unit when tuning?  What are peoples' experiences with this? Does returning the DS to parallel allow enough leeway to tune the pressure tuner? 

 

(One of the first things I did to the DS unit after I received it was to mess up the tuning thumbscrew by trying to tilt too much and having it unscrew completely so it didn't tilt at all. A call to Faye at Lunt gave me the info to get it tilting again.)



#12 rigel123

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Posted 07 May 2021 - 05:56 AM

I also just received the Lunt 50 DS unit after observing single-stacked for 6 months.  I have so far been following the instructions in the simple Lunt manual, which include removing the DS, tuning for details, and then putting it back on and tuning it. 
 
A newbie question: how to avoid removing the DS unit when tuning?  What are peoples' experiences with this? Does returning the DS to parallel allow enough leeway to tune the pressure tuner? 
 
(One of the first things I did to the DS unit after I received it was to mess up the tuning thumbscrew by trying to tilt too much and having it unscrew completely so it didn't tilt at all. A call to Faye at Lunt gave me the info to get it tilting again.)


Having had nothing but a totally tilt tuned Lunt for 9 years, the nice thing is once you set the tuning it stays that way unless you accidentally turn that wheel. I would think once you have your DS unit set, you could simply leave it on and use your pressure tuner to tune for your best view.

#13 chemman

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Posted 07 May 2021 - 06:22 AM

I have 2 pressure tuners on my Lunt and typically they are pretty well tuned from my previous observing.  If I bottom out without great detail I unscrew and let ambient air in and screw mostly to the bottom and begin backing it out until details start to pop.  I usually start messing with them and find my way back to where I started, on the first etalon in the image train one 1.5 turns from fully in and the second etalon in the image train about 2.25 turns out from fully in.  Any futher in an the image becomes significantly darker it seems.  Out futher and the proms fade and surface details fade.  I find that moving a prom to the sweet spot and tuning for best brightness of the prom there improves the entire field of view, I can then focus my attention to the feature I am concentrating on, tweaking the tuning slightly to bring out the most detail and depth.  

 

I almost never unstack.  Always more detail with a double stack for me.  

 

Chuck


Edited by chemman, 07 May 2021 - 06:27 AM.

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#14 alvacouch

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Posted 07 May 2021 - 09:29 AM

Having had nothing but a totally tilt tuned Lunt for 9 years, the nice thing is once you set the tuning it stays that way unless you accidentally turn that wheel. I would think once you have your DS unit set, you could simply leave it on and use your pressure tuner to tune for your best view.

Today I tried the suggestion of leaving the DS tuned and tuning the pressure separately. This really works well and even brings out details that can't be brought out by tuning the pressure first. Many thanks for the advice!


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#15 GOLGO13

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Posted 04 June 2021 - 01:31 PM

Still amazed by the difference in double stacking. I remember getting a boost when I double stacked my PST and double stacked using two 40mm coranados. But I didn't remember it being as big a boost as I'm seeing with the Lunt 50. My guess is I probably needed the blocking filters replaced on that PST and the diagonal...I mean, it worked OK but just seems like a big difference here.

 

I highly suggest double stacking if you can. I'm glad I did.




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