Lunt LS60MT operation (not really a modification)

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Lunt LS60MT operation (not really a modification)

Post by SimonM »

I have an LS60MT SS internal etalon and also a LS60FHa DS front etalon. The same LS60FHa and a B600/B1200 blocking filter/diagonal is sold as a package for converting nighttime scopes.

I want to evaluate the two etalons in SS mode - is that possible? As supplied the internal SS and (slight mod/reconfiguration) with front DS in a SS configuration e.g. without the internal etalon. By switching the 6 grub screws for 6 supplied finger screws, I can break the scope down into parts e.g. OTA, etalon and focuser, as Lunt intended. So...

If I take off the etalon and reassemble the scope e.g. blocking filter, focuser and OTA, what is to stop me from adding the front external etalon at the front? There is plenty of travel in the blocking filter/diagonal to make up for the removal of the internal etalon - that's exactly what would be done when switching to a Herschel Wedge.

Unless I missed something, there should be no reason the LS60FHa, can't be used as a SS with my B1200 blocking filter - no adapters required with my scope.

Simon
Last edited by SimonM on Thu Oct 28, 2021 11:11 am, edited 2 times in total.


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Re: Lunt LS60MT operation (not really a modification)

Post by EGRAY_OBSERVATORY »

Hello again Simon, I have just long-replied to your other post elsewhere on Solarchat.

I can't see any benefit in changing around the Etalons for your scope - even if that was possible.
I'm sure Lunt will be aware of any change of use of your acquisition and they should be consulted firstly...

Lunt direct would be the best source of accurate -information about that possibility if it were needed.

There maybe technical issues and any Lunt advice would be the best and safest - to be gained.
Besides if any damage could be caused by your idea, would not likely be covered by any guarantee...

As said in my other reply, it does take a little-time to get used to using and getting the best out of your SS and DS combination,
which I know only too-well from over ten-years experience...

Cheers
Terry


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Re: Lunt LS60MT operation (not really a modification)

Post by MalVeauX »

HI,

Yes you can evaluate both etalons.

Primary etalon that is internal, you can of course evaluate it alone (remove DS unit).

For the DS etalon, it's also a primary etalon, it's just being used as a DS module. Remove the internal etalon. Put the focuser back on the OTA without the etalon. Thread the DS etalon on the front of the OTA. Insert your blocking filter like normal. You have a single stack front mounted 60mm F7 scope ready to go. Evaluate it.

Then reassemble with both etalons if you wish for the intended double stack use.

Very best,


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Re: Lunt LS60MT operation (not really a modification)

Post by SimonM »

EGRAY_OBSERVATORY wrote: Mon Oct 25, 2021 11:15 pm I can't see any benefit in changing around the Etalons for your scope - even if that was possible.
Thanks for this and other helpful advice/info earlier. As Marty says, it is possible to use both etalons in an SS configuration.

Lunt sell a "combo" of blocking filter/diagonal (B600/B1200) and front mounted etalon (LS60FHa) to use with any scope (up to 1080mm FL for the B1200). With the LS60MT, you receive an assembled scope: blocking filter/diagonal (B1200), focuser (R&P), etalon assembly (with PT knob) and OTA (70mm ED objective). The LS60MT is modular so the etalon assembly is designed to be easily removed.
EGRAY_OBSERVATORY wrote: Mon Oct 25, 2021 11:15 pm I'm sure Lunt will be aware of any change of use of your acquisition and they should be consulted first.
I understand your concerns, but the two designs are slightly different. To help with the removal, the grub screws holding one component to the next can be replaced with (supplied) thumbscrews and for quick disassembly.

The reason I want to evaluate both etalons, individually as SS and not simply use the scope SS and then add DS, is that at the moment I want to use it at every opportunity, but with limited experience. I want to be sure that the LS60FHa is working correctly and I would expect the performance of both etalons to be more similar, than different, when used in an SS configuration. I'm also not ready to replace the EP with a camera, but that is a longer term goal.

It would also be educational (for me) to know the "bite point" where this particular tilt tuner starts to shift from the RED side to BLUE side, like on the PT knob where dialling in a certain amount of travel is required.
EGRAY_OBSERVATORY wrote: Mon Oct 25, 2021 11:15 pm As said in my other reply, it does take a little-time to get used to using and getting the best out of your SS and DS combination,
which I know only too-well from over ten-years experience...
I don't think I can compare 10 years of experience of the products with just a handful of hours. I'm sure I won't be the first user to try a DS and find that it's more a step backwards than forwards, or to question the products suitablity. There are just too many (incorrectly) variables to get right: two etalons, focus, seeing, dark adaption etc.
MalVeauX wrote: Tue Oct 26, 2021 3:22 am Yes you can evaluate both etalons.

Primary etalon that is internal, you can of course evaluate it alone (remove DS unit).

For the DS etalon, it's also a primary etalon, it's just being used as a DS module. Remove the internal etalon. Put the focuser back on the OTA without the etalon. Thread the DS etalon on the front of the OTA. Insert your blocking filter like normal. You have a single stack front mounted 60mm F7 scope ready to go. Evaluate it.
Good to know - thanks, as I do want to evaluate both etalons standalone in an SS configuration. With the LS60MT, there is no restriction/reason not to try it in an SS configuration.

Simon
Last edited by SimonM on Thu Oct 28, 2021 11:42 am, edited 1 time in total.


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Re: Lunt LS60MT operation (not really a modification)

Post by EGRAY_OBSERVATORY »

Ok Simon, with that knowledge, then I would suggest that if you get used to (when the clouds allow) the already SS and then start some imaging trials through that one, which of course you can publish here on this post or even on the SolarChat page, ready for better comparisons to the change-over of the two Etalons - would actually be better for you to make the comparisons, rather than thru an EP. Eye-adaption thru EP's needs to be the same for each Etalon trialled...

Of course where possible, identical weather conditions would be required as well, otherwise you could well be misled...

Terry


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Re: Lunt LS60MT operation (not really a modification)

Post by SimonM »

EGRAY_OBSERVATORY wrote: Tue Oct 26, 2021 10:41 pm Ok Simon, with that knowledge, then I would suggest that if you get used to (when the clouds allow) the SS and then start some imaging trials through that one, ready for better comparisons to the change-over of the two Etalons - would actually be better for you to make the comparisons, rather than through an EP.
I emailed Lunt and they replied saying that it was indeed safe to use the LS60MT with the B1200 blocking filter and the external LS60FHa in an SS configuration for H-Alpha. They also had a suggestion to adjust the two screws on the bottom of the LS60FHa by a small amount. Also, because of my (lack of) altitude, the adjustment of the tilt wheel may be closer to the initial end point (not canted over too much) when "on band".

I get your point that each SS (internal vs external) will require a different eye-adaption, but it should be simpler to establish that they are both operating as designed when used in an SS configuration more easily than trying to get DS (internal + external) up and running - today the conditions are "identical" e.g. cloud vs cloud. :band

Later on, I will be able to further evaluate the DS configuration where the image will be significantly darker and when conditions allow. What I'm trying to achieve is not unlike how this might be done in Production where the etalons are first evaluated in an SS configuration and only later tested together e.g. final checks "under the Sun" in SS (and only sometimes together in DS, depending upon the order)?

By using each etalon in an SS configuration, I can verify more easily that they are working correctly and also get to know the point at which each etalon comes "on band" e.g. the approximate setting of the PT knob and also the tilt wheel setting.

Simon
Last edited by SimonM on Thu Oct 28, 2021 10:46 am, edited 1 time in total.


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Re: Lunt LS60MT operation (not really a modification)

Post by EGRAY_OBSERVATORY »

Very complex reply Simon and the only recommendation has already been said, that use the SolarScope in the SS format until completely used to how it works and the EP viewing followed by PC-screen views, as time is getting short for northern-hemisphere operations, as well as not so nice in the open either (assuming you are in the northern-hemisphere).. :bow

Experimenting with expensive equipment - just to find something that may well not be there or important, is not the way forward. :bow

Most of us enjoy looking through and/or imaging and processing the results for others to look at and also enjoy, rather than spending a lot of money on gear to experiment with, where, as new from Lunt, will almost certainly perform as advertised by a company that has been around for many years and has previous proven SolarScope knowledge and manufacturing techniques too... :bow

Enjoy and show us some images for everybody-else to make their comments, which will give you a better idea of its' performance... :bow

Terry :movie


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Re: Lunt LS60MT operation (not really a modification)

Post by SimonM »

I'm aiming for a simple go/no go visual test this week to show in the SS format that all is basically well e.g. the numerous carriers involved didn't break it en-route. Lunt produces a good product, has good packaging, excellent Customer Service, but they absolve themselves from shipping damage e.g. a de-contacted etalon is the Customer's problem.

I have used the scope SS with the PT knob - it responds although there is a steep learning curve (for me). Now it's the turn of the tilt etalon with SS - which both Marty and Lunt said was OK to try. Checking it is basically OK visually in the simplest way possible, is the only option (for me).

Both DS and imaging with it are something I want to avoid for now until I get more experience. A quick go with DS was inconclusive as there is a lot of things to get right but I knew from the offset that was going to be how it goes. Of course, you still have to try it!

The weather (I'm in Hampshire, UK) has been fairly favourable and I use every opportunity to get outside with it - three days in the first week. Ignoring a botched attempt at DS, the SS with PT was getting there - third time lucky. Next is SS with tilt.

When I do get some images I will post the raw images (data) as well as my attempts at processing them may not be that good.

Simon


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Re: Lunt LS60MT operation (not really a modification)

Post by EGRAY_OBSERVATORY »

So then Simon, if you have a telephone with a camera, and/or a small or larger camera, just try putting it to the EP and taking what are called Afocal images and post them here for further advice. No need to go to the full-lengths at processing as long as the images do not exceed 2-Mbytes per image and in JPEG format. Different EP's or changing the 8-24 EP - will likely produce better images than some.

https://en.wikipedia.org/wiki/Afocal_photography tells about this method and I have done that with some giant telescopes at Herstmonceux Observatory and my own telescopes...

Practice, practice, practice with SS is the way forward initially.

if there were any shipping damage, this will normally be seen on the packaging (except Customs might need to make a "sniffer" hole) and the item(s) should have been insured against such damage...

Unfortunately, there are many who want to advise far-more technical-stuff than is really necessary at first-lights and just enjoy looking through your purchase to learn yourself the way forward...

Terry


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Re: Lunt LS60MT operation (not really a modification)

Post by SimonM »

This morning I was able to try the LS60MT SS with the front mounted LS60FHa e.g. without the internal etalon module. The sky was a bit hazy but the conclusion is that focusing in the edge of the Sun was only effective around 3/4 of the diameter. I tried varying the angle of the front etalon and also the angle of the diagonal to see if there was an obvious alignment issue - nothing obvious. With SS and the internal etalon e.g a normal LS60MT getting focus is much easier.

I did try to use my QHY5III178 camera to record the focus. I have emailed Lunt some questions and a picture of the etalon. I get a better and crisper view of sunspots with a Baader Wedge, albeit it with a 100mm scope where at least for this, the image is detailed and focus around the edge of the Sun is also crisp. There will be something obviously wrong but for now I don't know what it is.

Knowing what I know now, it doesn't come as a big surprise that adding DS to the existing SS previously didn't bring out any additional detail. I only had a dimmer view of what I could already see and it killed the prominences but added nothing new.

The conclusion is that being able to use the scope SS with a 2nd etalon before trying DS is extremely beneficial in isolating problems.

Simon


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Re: Lunt LS60MT operation (not really a modification)

Post by EGRAY_OBSERVATORY »

I'll have to leave you with whatever as what you have just said is perfectly normal..

I can't keep repeating the obvious - sorry

Terry


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Re: Lunt LS60MT operation (not really a modification)

Post by Highbury Mark »

It’s possible you might have a problem with your double stack filter Simon. I hope not, but there’s always the possibility that etalons can be damaged in transit. Although it’s important to spend some time tuning the single stack filter first, you should see a significant improvement in surface detail when you add the second filter and turn the DS tuning dial. With the Lunt 60, there’s a noticeable dimming when double stacked but not dramatic - the Sun should still be more than bright enough. Also - single stack views through the external 60mm filter should be at least as good as those through the smaller internal filter. Hope I’m wrong but you should be seeing more immediate results.


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Re: Lunt LS60MT operation (not really a modification)

Post by SimonM »

Highbury Mark wrote: Sun Oct 31, 2021 7:23 pm It’s possible you might have a problem with your double stack filter Simon. I hope not, but there’s always the possibility that etalons can be damaged in transit. Although it’s important to spend some time tuning the single stack filter first, you should see a significant improvement in surface detail when you add the second filter and turn the DS tuning dial.
Hi Mark,

The double stack (DS) filter does have a problem and the top edge of the etalon is visibly damaged in transit. I have sent it back to Tucson for repair and they received it back almost a week ago. The kind folks at Lunt say that they will be able to make a start around mid/late January when they again will be making a batch of these particular etalons.

Simon


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Re: Lunt LS60MT operation (not really a modification)

Post by EGRAY_OBSERVATORY »

God news on the return to Lunt for repairs then.

Terry


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Re: Lunt LS60MT operation (not really a modification)

Post by EGRAY_OBSERVATORY »

I don't know what happened with my reply, but I did not type the wording "[no religion please] "

Terry


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Re: Lunt LS60MT operation (not really a modification)

Post by EGRAY_OBSERVATORY »

Good news on the return to Lunt for repairs then.

Terry


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Re: Lunt LS60MT operation (not really a modification)

Post by marktownley »

EGRAY_OBSERVATORY wrote: Tue Dec 14, 2021 12:32 am I don't know what happened with my reply, but I did not type the wording "[no religion please] "

Terry
You had one 'o' too few in the word 'good' Terry ;)


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Re: Lunt LS60MT operation (not really a modification)

Post by EGRAY_OBSERVATORY »

Ooooh Aaaaah Mark, it's "good" to know that someone up there is checking my spelling then :lol:

Thanks vm
Terry


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Re: Lunt LS60MT operation (not really a modification)

Post by Bob Yoesle »

The sky was a bit hazy but the conclusion is that focusing in the edge of the Sun was only effective around 3/4 of the diameter. I tried varying the angle of the front etalon and also the angle of the diagonal to see if there was an obvious alignment issue - nothing obvious. With SS and the internal etalon e.g a normal LS60MT getting focus is much easier.

I did try to use my QHY5III178 camera to record the focus. I have emailed Lunt some questions and a picture of the etalon. I get a better and crisper view of sunspots with a Baader Wedge, albeit it with a 100mm scope where at least for this, the image is detailed and focus around the edge of the Sun is also crisp. There will be something obviously wrong but for now I don't know what it is.

The double stack (DS) filter does have a problem and the top edge of the etalon is visibly damaged in transit. I have sent it back to Tucson for repair and they received it back almost a week ago. The kind folks at Lunt say that they will be able to make a start around mid/late January when they again will be making a batch of these particular etalons.
HI Simon, sounds like you have a de-contacted etalon from your description. The image(s) will be of the photosphere, and there are multiple similar off-band images smearing off the one side. This was caused aby a mechanical jolt that was strong enough to overcome the molecular forces binding the etalon plates together via one (or more) of the spacers that are in direct contact on either side with the etalon plates and maintain the gap spacing. The etalon gap is no longer capable of being on-band, and the etalon plates are tilted with respect to each other, creating an infinite series of lateral reflections of decreasing brightness.


SM90II sm.jpg
SM90II sm.jpg (390.82 KiB) Viewed 3708 times
Decontacted etalon.jpg
Decontacted etalon.jpg (120 KiB) Viewed 3716 times


The etalon should have been packed well enough to handle routine shipping events, and sounds like if you can see actual physical damage it was significantly mishandled at some point.


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Re: Lunt LS60MT operation (not really a modification)

Post by SimonM »

Bob Yoesle wrote: Tue Dec 14, 2021 4:36 pm HI Simon, sounds like you have a de-contacted etalon from your description. The image(s) will be of the photosphere, and there are multiple similar off-band images smearing off the one side. This was caused by a mechanical jolt that was strong enough to overcome the molecular forces binding the etalon plates together via one (or more) of the spacers that are in direct contact on either side with the etalon plates and maintain the gap spacing.
Hi Bob, the explanation is a bit simpler. If you take the front mounted etalon and unscrew the red top from the black base (like removing a camera filter) you can see the etalon assembly has a hinge on one side and a screw thread lift-arrangement on the other side. When the tilt wheel is rotated it rotates a thread and should lift the etalon by only a small amount. I initially contacted the folks at Lunt because there didn't seem to be any limit to the amount of rotation e.g. five turns of the wheel vs an infinite number. The red housing was supplied ever so slightly loose and when removing the etalon from the main scope the red housing could turn slightly - the effect was a grittiness and its actually powdered glass that gets into the threads.

I did press down on the cage assembly (not directly on the etalon) and simultaneously rotate the tilt wheel and it just (too late) popped back into place. I noticed that the side of the etalon was covered in (what I thought was silicone adhesive) - it was the crumbled edge of the glass on the side opposite the hinge. A simple analogy is if you take a door on its hinges and remove the locking mechanism on the other side, it is free to swing e.g. into the entrance lobby and damage anything in its way. It is this that has damaged the front facing edge of the etalon in transit. The etalon is transported in a flight case with a minimum of one inch of foam on all sides. This box is suspended in foam end pieces that keep it an inch from the outer carton which is double boxed for protection. The Retailer had also packaged the Lunt boxes in an outer carton with an additional two inches of polystyrene "peanuts" for additional protection.

The advantage of the LS60MT is the ease of being able to convert it to a front mounted etalon simply by removing the internal etalon assembly. The original post was to establish if using the blocking filter with only the front mounted etalon was safe - as confirmed by Lunt. As a single stack etalon I was able to get a dark red disc of the Sun and two separate faint images of the Sun. This is described in the manual. The two additional images are so far removed that you have to look for them and bring them into the FOV.

The image you show makes a lot of sense because with a de-contacted etalon there will be an infinite number of reflections and not the two additional images and a main image that I could see. My issue with the Sun's disc was that it wasn't only sharply in focus around only 3/4 of the diameter. I didn't try it, but if you "stopped" the etalon down e.g. with a 30-40mm disc then it would probably have the potential to still function successfully. As it is, the scatter from the damaged area is sufficient to affect the image across a wider area, than you might at first think.

When looking into the etalon from the back with the cover (and red filter) removed, you have a perfectly uniform cyan surface from behind and a gold surface from the top. Looking through, you wouldn't easily see that there are additional internal surfaces and it is difficult to find the separating pads except by illuminating from an oblique angle. For my etalon, it is easy to show that it hasn't de-contacted and Lunt confirmed that this appears to be the case. There is also no damage to the housing e.g. it hasn't been dropped/knocked in use - so these parts have the potential to be reused. My understanding is however, that is will be a completely new double stack, retaining only the serial number previously used.

Simon


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