SolarChat!

DanielD wrote: ↑Tue Jan 18, 2022 9:16 pm In Layman's terms the collimator is mounted in front of the etalon chamber and then the OTA is shortened to be able to reach focus?

Yes

Hi Marty,

That's a really nice modification and clear and concise write-up! I have a CR-6 refractor, similar to the one you are using. I have been mulling over selling my SM 90 and getting a Lunt Modular 80 double-stack. Do you know if the etalon housing for the 80 would fit into a 2" focuser? Do you think with double stacking, there will be too much weight hanging on the focuser (I upgraded to a Moonlite)? Thanks and clear skies!

James

hopskipson wrote: ↑Sat Jan 22, 2022 8:29 pm Hi Marty,

That's a really nice modification and clear and concise write-up! I have a CR-6 refractor, similar to the one you are using. I have been mulling over selling my SM 90 and getting a Lunt Modular 80 double-stack. Do you know if the etalon housing for the 80 would fit into a 2" focuser? Do you think with double stacking, there will be too much weight hanging on the focuser (I upgraded to a Moonlite)? Thanks and clear skies!

James

Mapleridge used a CR6 lunt 80 mod until he changed scopes

viewtopic.php?t=25185

viewtopic.php?t=32743

James...

I used the DSII external etalon in my mod, and it is much larger than a 2" focuser...I can get the dimension if needed. I is also quite heavy so I would not think it would be a good plan to adapt it into a focuser. This one is best fixed to the scope and put the focuser after it. I have the 2" and 2.5" Moonlites and wouldn't try the 80mm etalon mounted in either of them. The 50mm is maybe more suitable, but I would still be concerned about the stress on the focuser with the need to turn the pressure knob.

The primary etalon in the LS80T scope can be un-screwed from the solar scope as well but it needs a fine thread machined or sourced form other adapters in order to adapt it to a mod...and it weighs more than the DS unit. The second link that was posted shows the latest revision...the same basic setup was used to fit the DSII onto 3 OTAs...Celestron C102, Celestron CR-150 and now used on the Orion EON 130mm OTA.

PM me if you have any specific questions.

Brian

MapleRidge wrote: ↑Tue Jan 11, 2022 11:43 pm One question...with the pressure tuned assembly mounted in the focuser, how well does it handle tuning (as in stress on the focuser tube with the twisting actions to make tuning adjustments)? I expect in warmer climes the twisting motion shouldn't be too stressful, but I'd be afraid of damaging the focuser in the cold.

I'm in Florida, fairly warm here. I've not had any issues with twisting down the pressure tuner. My focuser is not special, its a linear bearing GSO but it handles the stress no problem with all this weight too. I can't speak for cold places and how it would behave!

Very best,

DanielD wrote: ↑Tue Jan 18, 2022 9:16 pm In Layman's terms the collimator is mounted in front of the etalon chamber and then the OTA is shortened to be able to reach focus?

Correct! I measured where the collimator needed to be relative to the objective so that it was positioned in a specific light cone. I had to shorten this OTA for this particular setup. Other scopes with different setups would need different distances for everything. This is the same as you'll find with a PST mod or Lunt 50 mod, or any air spaced etalon using a collimator lens for modding.

Very best,

hopskipson wrote: ↑Sat Jan 22, 2022 8:29 pm Do you know if the etalon housing for the 80 would fit into a 2" focuser? Do you think with double stacking, there will be too much weight hanging on the focuser (I upgraded to a Moonlite)? Thanks and clear skies!

James

The Lunt 80 etalons are pretty big, it would be a tight squeeze with 2" focusers. You'd be better off with the next size up focuser like those 2.7" or 3.X" focusers for something larger like that. Not just weight but clear diameter comes into play with the light cone, especially if you have to shorten an OTA for these collimators. The other option is to remove the collimators and use a telecentric system, but it's not great and requires really long focal-ratios to even get back to what it was doing with the collimators (see Christian's calcs and graphs; not a lot of compelling data shows using telecentric with air spaced is worth while to me).

Very best,

Sorry for the delay, I have had major issues connecting to SolarChat. Accessing the site seems to take ages. It's like the server was changed to something lesser, or maybe my routing to the site has drastically changed and now hopes around the world a few times first. But something changed and its incredibly slow to load for me now.

++++++++++++++++++++++++++++++++++++

Some more results from back in December:



Very best,

Thanks for the updates Marty. The results speak for themselves, it's a very effective mod.

Sorry to hear you were having access issues. Nothing has changed behind the scenes here but I think I will give the cache a purge just for good measure.

MalVeauX welcome back!
Please tell me when you planing create Lunt60 mod with Celestron 8hd?
Im waiting=)))

OlegLviv wrote: ↑Sun Feb 13, 2022 1:34 pm MalVeauX welcome back!
Please tell me when you planing create Lunt60 mod with Celestron 8hd?
Im waiting=)))

It already works with that, SCT are much easier since you can move the primary mirror. Refractors are harder due to needing to place the collimator at specific location in the light cone. This mod works natively right away with SCT due to that primary mirror moving and should work with Mak too. I don't advise Newtonian unless it's long focal-ratio and even then its just harder to setup and balance. SCT and refractor are just easier frankly for this stuff. I will get some examples of it working and try for some ok data in sub-angstrom seeing when I can.

Very best,

MalVeauX wrote: ↑Sun Feb 20, 2022 1:24 am

OlegLviv wrote: ↑Sun Feb 13, 2022 1:34 pm MalVeauX welcome back!
Please tell me when you planing create Lunt60 mod with Celestron 8hd?
Im waiting=)))

It already works with that, SCT are much easier since you can move the primary mirror. Refractors are harder due to needing to place the collimator at specific location in the light cone. This mod works natively right away with SCT due to that primary mirror moving and should work with Mak too. I don't advise Newtonian unless it's long focal-ratio and even then its just harder to setup and balance. SCT and refractor are just easier frankly for this stuff. I will get some examples of it working and try for some ok data in sub-angstrom seeing when I can.

Very best,

Thank you very much! Soon will be arrive my C8 HD and Televue Powermate 4x for Lunt60 mod.

Best Regards

OlegLviv wrote: ↑Mon Feb 21, 2022 6:44 am

MalVeauX wrote: ↑Sun Feb 20, 2022 1:24 am

OlegLviv wrote: ↑Sun Feb 13, 2022 1:34 pm MalVeauX welcome back!
Please tell me when you planing create Lunt60 mod with Celestron 8hd?
Im waiting=)))

It already works with that, SCT are much easier since you can move the primary mirror. Refractors are harder due to needing to place the collimator at specific location in the light cone. This mod works natively right away with SCT due to that primary mirror moving and should work with Mak too. I don't advise Newtonian unless it's long focal-ratio and even then its just harder to setup and balance. SCT and refractor are just easier frankly for this stuff. I will get some examples of it working and try for some ok data in sub-angstrom seeing when I can.

Very best,

Thank you very much! Soon will be arrive my C8 HD and Televue Powermate 4x for Lunt60 mod.

Best Regards

Fascinating work all.
I wonder does anyone have a step by step instruction to make Combination or Franken-solarscopes, as I find it hard to work out from the beginning first principles to making all the adaptors and stuff fit together, without getting blinded by the Sun's photons. It is also harder without the search function on this forum.

Many thanks.
Magnus

A couple of days ago I stacked my 127 f9 telescope with Lunt LS60T Ha serial number 20111xxx, and noticed that there is a built-in 2x barlow lens in front of the etalon and the telescope itself is not f8.3 its f4.1.

Why they did so I do not know without a 60mm object 250mm focal length and f4?

After testing, to be honest, I was not very happy now, I don't know if the 60mm standard Lunt has 35mm or only 20mm?

From the defects, I started the glare on the sides, the sweet spot remained the same as in pst mod 2!

Maybe when I buy a full-aperture ERF glare will disappear?

What is the difference between your Lunt LS60MT and my LS 60T HA?

with 2.5 telewue we have F44 1140*2*2.5X= 5700MM
with 3x telewue we have F54 1140*2*3X=6700MM
with 5x telewue we have F90 (1140*2*5X)=11200MM

My setup:
Refractor 127/1140 f9
Lunt LS60T Ha
Front ring M50X1 M48X0.75
Baader Ha 35nm 2.0
Apollo Max 432mm

OlegLviv wrote: ↑Tue May 03, 2022 6:39 am After testing, to be honest, I was not very happy now, I don't know if the 60mm standard Lunt has 35mm or only 20mm?

From the defects, I started the glare on the sides, the sweet spot remained the same as in pst mod 2!

Maybe when I buy a full-aperture ERF glare will disappear?

What is the difference between your Lunt LS60MT and my LS 60T HA?

Hi,

The older Lunt and newer Lunt are the same other than the OTA (70mm F6 ED on the new one, internally masks the aperture to 60mm F7). The chambers, etalon, etc, are all the same. Even the threaded nose with the red ERF is the same. The only difference is the older one threads into an OTA and the modular one inserts and secures with thumb bolts. There is no barlow in there; you can check by measuring the focal length of the objective and verifying with the disc image at focus. The lens in front of the etalon is just a collimator lens.

Your issues are from placement. The collimator lens needs to be at -264mm back focus. Don't use focal ratio to place the colliator, use a measured back focus value. The glare will not be fixed with an ERF, it's glaring because its not in the correct position. The sweet spot will be way larger than a PST when you get the collimator in the correct place (you can see my results above; it's a 35~38mm clear aperture etalon, the PST is 20mm clear aperture, you will have a larger sweet spot with the Lunt 60 etalon if properly placed).

Did you shorten your 127mm F9 telescope so that you could insert the collimator to -264mm of back focus?

Very best,

Honestly, I shortened this telescope to PST MOD 2 and cut a little pipe, but to cut a lot I put in front of the standard Baader 1.25x GPC and I was able to focus and shoot normally!

Now I didn't cut anything, I just made a ring to attach the lunt to it and that's it.
I thought that the distance for PST MOD2 and for Lunt 60 is the same and did not cut or measure anything.

My friend measured everything and says that the lens has a focus of 250mm f4 and not 500mm f8.3 my telescope on the passport write 60/500 mm f8.3

If you say that there is no 2x Barlow lens in this LS60T Ha model, that's fine.

On photo without lens barlow only camera and BF15.We see vignetting and a sweet spot.

A year ago we did 220mm back focus for PST MOD2, now we didn't cut the 264mm telescope and just connected it to the telescope.

I understand that you need to cut off the telescope so that the native focus is in 0 position and focus on the lunt focus and find a distance of 264mm?

OlegLviv wrote: ↑Tue May 03, 2022 1:33 pm Now I didn't cut anything, I just made a ring to attach the lunt to it and that's it.
I thought that the distance for PST MOD2 and for Lunt 60 is the same and did not cut or measure anything.

If you say that there is no 2x Barlow lens in this LS60T Ha model, that's fine.

On photo without lens barlow only camera and BF15.We see vignetting and a sweet spot.

A year ago we did 220mm back focus for PST MOD2, now we didn't cut the 264mm telescope and just connected it to the telescope.

I understand that you need to cut off the telescope so that the native focus is in 0 position and focus on the lunt focus and find a distance of 264mm?

Hi,

Yea, that's the issue, it's too far away from the position the collimating lens needs to be in. It's not the same as a PST at all (which needs -200mm back focus to place the collimator lens). Try to let go of focal-ratio as it's not what is used for any of these collimator lenses, they use focal lengths. Lots of these designs internally mask a larger aperture, so the focal-ratio is deceptive anyways.

You don't have to take my word for it; just take the objective of your Lunt 60 and with nothing else in the OTA, just the lens, see where the disc comes to focus--that's its focal length. Then measure from that plane of focus to where the collimator lens sits inside the OTA. That backfocus distance is where the collimator needs to be in any OTA, so you can scale it up to any larger aperture, but that back focus distance will be constant. Do not use focal ratio for that, use the exact back focus distance. My Lunt measured at -264mm as mentioned. The older Lunt models likely are using the same internal hardware and the only difference is the OTA (the newer one being a 70mm F6 ED frac, bigger than the older Lunt achromatic doublet OTA).

Again refer to my first few posts that show the method to determine where the collimator must be.

Very best,

Good evening I am from Ukraine!
My friend measured everything today and said that there is a lens that increases the focal length according to his calculations 1.88x.
Set the distance on the collimator. And saw that the difference between the sweet spot Coronado PST and Lunt 60 almost did not change.
We will make that the center of a sweet spot was as much as possible on the center and it is necessary to increase it as much as possible.
What can you say?
What's wrong with my Lunt?
It turns out that we have not only different Ota but also different middle of the telescope.

Hi,

I highly doubt the inside of the 60's are different and the only difference is the OTA. The collimator lens may have a slight magnification to it. But it doesn't matter. All that matters is where the collimator sits in terms of its distance from the focal plane. It's super obvious when you track the collimator and etalon from too far away from that point (-264mm +/- 1~2mm) as it goes from poor performance to obvious high contrast performance as its placed correctly.

Yours wasn't working because you had it too far back. It needs to be at -264mm of back focus. It's truly that simple. Nothing is wrong with your system other than its placement.

Very best,

I own an identical LUNT LS60THa and confirm that it is completely atypical and cannot be used for a mod with a different OTA. The single-lens objective is compensated by a collimation lens and even if it is used, for example, by the OTA 80/F4, the image quality is not good.
The only way is to remove the collimation and output lens of the etalon and replace them with lenses that do not compensate for single-lens objective aberration.

Hrm,

I wonder what kind of compensation a collimating lens set would need for a singlet vs anything else?

Also the Lunt 50 is the same thing as the older Lunt 60 with respect to this, and it mods into larger systems quite fine. So I'm betting it's just getting the collimator of the Lunt 60, regardless of the older version in the singlet, into the appropriate position.

Very best,

Did the double stack version succeed?

The problem with the LS60 is that the collimation lens also works as a Barlow 1.89 x and the objective is F4.2. It is difficult to find a larger diameter with a similar parameters and, above all, the same aberration, so that the etalon can be used without changing lenses.

pupak wrote: ↑Tue Jul 26, 2022 5:15 am The problem with the LS60 is that the collimation lens also works as a Barlow 1.89 x and the objective is F4.2. It is difficult to find a larger diameter with a similar parameters and, above all, the same aberration, so that the etalon can be used without changing lenses.

Is it definitely a singlet in your lens cell - have you take it out and checked?

Yes, it's a 266mm focal length singlet. I am not considering a modification yet, because the telescope draws very well and the etalon is of very high quality.

Hello friends am not alone=)
Yes yes single lens that I sad collimation lens also works as a Barlow 1.89 x and the objective is F4.2
Can Do It this modification!
After two months of work, such a miracle turned out!
In my mind its very good modification with my 127/9 refractor!
Better PST 2 modification!
Such a larger sweet spot in the 35mm standard than in the PST 20mm
I will show a comparison later

Refractor Achromat 127/F9 + Lunt 60mm + Coronado BF15
Camera:Apollo MAX M 432
Barlow Lens: Televue Powermate 2.5x/Televue Powermate 4X
Baader UV/IR CUT + Astronomik 6nm Ha

A few photos my stack modification!

Such a larger sweet spot in the 35mm standard than in the PST 20mm

Hi Oleg,
many thanks for the samples. The photos are very nice. Am I to take it that you used the LS60THa with that collimating lens for a simple 60/F4.2 objective and got such beautiful results?
Can you share the exact setting of the etalon position in relation to the focal point your 127/F9 ?
This is a very important value and your result is really a small miracle.

mami813 wrote: ↑Tue Jul 26, 2022 2:07 am Did the double stack version succeed?

Hi,

Yes, the first iteration with a Siebert Optic telecentric worked, however it had a sweet spot so it was determined that it was not a true telecentric. I replaced it with a Baader TZ4 4x telecentric and the sweet spot was gone and it worked very well. I also had to change the location of the ITF and blocking filter, for vignette reducing purposes. It is no longer near the camera and is instead before the telecentric. This system is a collimated system with air spaced etalon followed by a telecentric system with air spaced etalon (I used my pre-meade PST etalon which is excellent contrast). Together when tuned, they do quite well in this configuration on the 150mm refractor with no electronics needed to tune. This also works on my Lunt 60 stock instrument as a double stack as well for full discs.


Here's the real world view in FireCapture, the double limb gone and a nice wide FOV:


Here's the same imaging train back in the stock Lunt 60 OTA, as it's totally modular and reversible and can be used in either system. It just inserts. The spacing and focus is the same.


Here are my latest double stack results with this system (some of these are mosaics, huge):






















And the full discs (mosaics, but only 3~4 slices to make them, easy). Same imaging train, same camera, etc as above. Just in the Lunt 60 OTA as seen in the image above.






Very best,

pupak wrote: ↑Tue Jul 26, 2022 5:10 pm Hi Oleg,
many thanks for the samples. The photos are very nice. Am I to take it that you used the LS60THa with that collimating lens for a simple 60/F4.2 objective and got such beautiful results?
Can you share the exact setting of the etalon position in relation to the focal point your 127/F9 ?
This is a very important value and your result is really a small miracle.

Yes I use the LS60THa with that collimating lens for a simple 60/F4.2 .
The collimator lens needs to be at -264mm back focus. Don't use focal ratio to place the colliator, use a measured back focus value.
MalVeauX told me.

I tried this etalon with -264mm back focus on AR90/F10 and the results were unusable. You are a lucky man.

pupak wrote: ↑Tue Jul 26, 2022 6:21 pm I tried this etalon with -264mm back focus on AR90/F10 and the results were unusable. You are a lucky man.

Man wats wrong you have Lunt 80mm Duble stack with 150mm refractor you are lucky =))))

pupak wrote: ↑Tue Jul 26, 2022 6:21 pm I tried this etalon with -264mm back focus on AR90/F10 and the results were unusable. You are a lucky man.

Hi,

So the collimator in the previous Lunt 60 LS60THA vs the latest modular Lunt 60 LS60MT are different, I've had two people try to use their older Lunt and found the positioning to not work. The focal length of the singlet is different, but also the collimator is also differently positioned.

Finding the correct position for the collimator is the same process. Take the etalon chamber out of the singlet based OTA of the LS60THA and point the lens at the sun. Using a black piece of metal and a measuring instrument, find where the disc is at focus behind the lens. It should be equal the lens's actual focal length. Note that position. Measure from that point back into the light cone to the location where the collimator lens would be if it were reinserted into the OTA. That back focus distance is constant and that's where the collimator needs to be on any other lens and OTA. On the LS60MT it's around -264mm. The LS60THA is probably different, but again, measured the same way.

Very best,

pupak wrote: ↑Tue Jul 26, 2022 6:21 pm I tried this etalon with -264mm back focus on AR90/F10 and the results were unusable. You are a lucky man.

Sorry for not correct answer my friend told me how we are doing (-264mm back focus without 1.86 lens barlow which is not MalVeauX on his telescope)
You and I have 1.86 lens and the distance will be different than have MalVeauX Lunt 60.
You can see the correct distance on my drawing.

I tried both variants. Back focus -264 and then focus location identical to your image. Neither option yielded a usable result.
Probably 90/F10 is already beyond the limit of usability for collimation at F4.2.

pupak wrote: ↑Wed Jul 27, 2022 5:49 am I tried both variants. Back focus -264 and then focus location identical to your image. Neither option yielded a usable result.
Probably 90/F10 is already beyond the limit of usability for collimation at F4.2.

Ohhh you can see your result us? Your sweet spot!

The sweet spot didn't happen. I couldn't even focus.

pupak wrote: ↑Wed Jul 27, 2022 7:48 am The sweet spot didn't happen. I couldn't even focus.

Perhaps you need to install a 30mm or 50mm or 80mm extension adapter or shorten the telescope, I cut mine OTA minus 70MM+-

Fascinating article and result.

Way beyond my capability but nonetheless impressive!

OlegLviv wrote: ↑Wed Jul 27, 2022 3:07 am

pupak wrote: ↑Tue Jul 26, 2022 6:21 pm I tried this etalon with -264mm back focus on AR90/F10 and the results were unusable. You are a lucky man.

Sorry for not correct answer my friend told me how we are doing (-264mm back focus without 1.86 lens barlow which is not MalVeauX on his telescope)
You and I have 1.86 lens and the distance will be different than have MalVeauX Lunt 60.
You can see the correct distance on my drawing.

Hi Oleg, thank you very much for the important information. Can I just simply understand that you only fit the distance from etalon to focus plane(148mm) to the new scope and become successful?

Best

Su

Thanks you marty for this post.

i did get this to work with a Meade Messier AR152L/1200.

Still have some tilt problems but it worka great.

haveing a lot of fun with this.

Dominik

Nice hear you!