Available external DS etalons??

[Merlin66]

I can't seem to find any Meade/ Coronado external etalons in the US...
The SME-40, SME-60 and SME-90 are still listed in the UK
http://www.meadeuk.com/Coronado-Etalon-Units.html

Lunt do a 50mm/60mm and 100mm
Is that correct???

[marktownley]

Yup, that's correct Ken. I do like the look of the new 90III, but is a lot of money and wouldn't even consider one unless could do a period of protracted testing before purchase.

[pedro]

My experience is that the Coronado Solarmax II (Meade) are not great (as compared to the pre-Meade external etalons). I have tried a few: SME-40, SME-60 and SME-90

No idea if the Solarmax III performs better

Visually they are usually OK, things tend to get worse when we use a CCD or CMOS camera

[Merlin66]

Pedro,
Interesting comment.....
I recently tested a defective SME90 and had major "issues" with the Richview tuning....it ended up going back to Meade (from Australia) twice before effectively being repaired.
I tend to agree, the original Coronado DS filter (I use one on my ED80 set-up) is very good.
Ken

[pedro]

Hi Ken

My SM90II was also serviced twice (Meade Mexico factory and Germany - BelOptik).

It is fine now but I feel that it is somewhat off band (less contrast then pre Meade etalons)

best regards

[RKBerta]

I have an external Coronado (before Meade) 60mm Etalon single stacked used with a TeleVue 85mm APO telescope and both a BF15 and BF30 blocking filter. I was considering upgrading to something larger but thus far I have not been impressed with either Lunt or newer Meade/Coronado offerings in direct comparison. It also works great for photography so think I will just stay with it and my Quark Chromosphere used with either their SS Scout 80mm refractor or the TV 85 or 110mm custom refractors for double stack like performance.

[RKBerta]

I was curious about your posting where you said the catalog was not showing any external Etalons from Coronado. I went to their web site and you are correct. About 1 1/2 months ago they did have a combo 90mm external Etalon with a choice of blocking filters listed. I called to get more info but decided to hold off for a while....see my post above. But at the time they DID still have a package with the 90 and BF filters per my phone conversation. Maybe with the low solar activity they aren't moving so took them out of the catalog until things pick up. You could call to see if they still have stock because when I called they told me they did have it in stock. In my view the external Etalons have given better performance than internal...at least on Coronado and Lunt versions for a given aperture. Maybe when the sun activity picks up they will get more interesting products out.

[MalVeauX]

Hello,

I too am gaining some interest in an external etalon module. I can readily pick up Solarmax 60mm front mounted ones. I'm considering trying to make a modular setup with a small short refractor for multi-wavelength imaging. For HA, maybe a Solarmax 60mm front mounted etalon with whatever adapter it would take to mount it and appropriate blocking filter (10mm probably for me). Take that off and put a Lunt CaK module in the back for Cak. Straight through with a wedge for white light.

What's the best way to get an adapter plate that will accept the front mounted solarmax 60mm etalon and how to fit it to a scope? I was reading they directly thread onto a Televue Pronto, but I don't want to buy a scope if I can just have an adapter/plate made. I was thinking of either using my ED80 or my ST80 for this.

Anyone have plates made for scopes some where?

Very best,

[Bob Yoesle]

Precise Parts in Miami is your ticket Marty:

https://www.preciseparts.com/ppmain//index.html

[MalVeauX]

Precise Parts in Miami is your ticket Marty:

https://www.preciseparts.com/ppmain//index.html

Bingo! hah, so simple. Thanks Bob!

Looks like they can machine an adapter for $150. Pricey for what it is. But, if it's precise, I can't argue with the simplicity and being able to move the etalon to various scopes is a nice thing to have to avoid being stuck with a dedicated scope.

Was thinking the following (may not work, just thinking out loud):

Either ST80 (400mm F5) or ED80 (600mm F7.5) as donor scope.

Solarmax 60mm front mounted HA filter & ERF -> custom adapter to paricular scope -> PST etalon (no collimating lenses) *if* this is possible -> 10mm blocking filter (HA full disc)

Same scope, no adapter/front filter -> 2" Baader Blue CCD IR-block filter (ERF 1) -> Lunt 1200 CAK module (Cak full disc)

Same scope, no adapter/front filter -> 2" Baader Blue CCD IR-block filter (ERF 1) -> Andorver 430nm filter (white light full disc)

That way it's a simple, modular, 3 wavelength full disc refractor with the setup. This will piggy back or side by side with my C8 Edge HD with tri-band ERF that will do the high res work next to it.

Very best,

[Bob Yoesle]

ED 80 might be better for the CaK, but hard to say w/o having accurate data.

You set up sounds like it will be ideal. Two thumbs up!

[bart1805]

"Solarmax 60mm front mounted HA filter & ERF -> custom adapter to paricular scope -> PST etalon (no collimating lenses) *if* this is possible -> 10mm blocking filter (HA full disc)"

I think you do need both the collimating lenses in this set up.

[MalVeauX]

"Solarmax 60mm front mounted HA filter & ERF -> custom adapter to paricular scope -> PST etalon (no collimating lenses) *if* this is possible -> 10mm blocking filter (HA full disc)"

I think you do need both the collimating lenses in this set up.

Well rats, I would hope it wouldn't be needed so I could move it between scopes without having to configure things.

Do you think it would not be ok to use with the Solarmax 60mm etalon front mounted, F10 beam at the end of the scope, used just to shave the skirt profile a little? If that doesn't work, I'm ok with it, I just won't bother and will buy a 2nd etalon for double stacking (if it matters enough). It would be nice if the PST etalon in the back could shave it enough to remove the double limb though!

ED 80 might be better for the CaK, but hard to say w/o having accurate data.

You set up sounds like it will be ideal. Two thumbs up!

Thanks Bob,

The goal is maybe to have the C8 Edge HD with tri-band ERF in a side by side with the 80mm scope (either one). And then be able to use my current PST etalon (without collimating lenses) and Quark as needed between the two (though the Quark would just stay away from the short refractor and only be used with the C8). The Lunt Cak module and Andover 430nm filter could be used between the two scopes without any configuration changes. The main thing being able to eventually double stack the 60mm Solarmax unit somehow (with the PST etalon maybe?). And the other, being able to eventually maybe double stack the lunt Cak with another lunt Cak filter (or PST cak if I find one)?

Very best,

[Merlin66]

Marty,
What you are describing is exactly what I use.....
The SM60 is fitted to an ED80 which has the focuser removed to allow the "PST Stage 2" mod to be fitted as a DS. Then finally a BF15.

I'm still trialling the radial positioning of the PST etalon v's the SM60 to give the best "transmission skirt removal"

I also have a CaK module (Baader Blue ERF plus Omega filters) which can mount in the ED80 (stopped down to 60mm).

Then finally there's the Baader Herschel wedge which can be fitted to the ED80 for white light.

I'll post some images of the set up later,
Ken

[MalVeauX]

Interesting! Curious to see how it looks stacked, and how to focus!

Very best,

[Merlin66]

Originally I set up the PST mod behind the SM60 back in 2010....

PST SM60 double stack.jpg (198.67 KiB) Viewed 6486 times

Later I had a similar set up but using the TS102 Which was interchangeable with the Baader wedge.

TS102_PST 006.JPG (83.68 KiB) Viewed 6486 times

TS102_Baader 003.JPG (68.58 KiB) Viewed 6486 times

This arrangement was then transferred to the ED80 using a further adaptor plate which allowed either the original focuser + wedge or the PST mod to be fitted.

ED80_SM60_PST01.JPG (306.8 KiB) Viewed 6486 times

To assist in the focusing with various cameras the original Borg helical focuser was up graded to a motorised short Lunt Crayford.

100_3467.JPG (262.91 KiB) Viewed 6486 times

[MalVeauX]

Very interesting! I have to see if I can dig up more material on the Solarmax 60mm etalon and how to combine the PST etalon in various ways.

Very best,

[Merlin66]

Marty,
If you need any more info.....just ask. The key I think is to get the optimum positioning (and rotation alignment) of the PST etalon assembly - the -200mm Majic number.

For completeness I also had for a few years 2007> a double stacked SM60 arrangement on the same ED80 - I thought it was great!!!

IMG_1544s.jpg (242.23 KiB) Viewed 6479 times

Once tuned they could be tilted as a "combined" filter unit.......

[MalVeauX]

I assume that's with the F10 collimating lenses?

My curiosity is the PST etalon without collimating lenses, as the 2nd etalon in a series.

Very best,

[Merlin66]

Thinking about it....you could mount the bare PST etalon IN FRONT of the SM60 as a DS, BUT this would limit the effective aperture to 20mm.
No really an interesting option.....

[Merlin66]

Marty,
Yes, the original PST f10 etalon arrangement.
With the external etalon - it's sitting in a collimated beam - the light from the Sun. Behind it the objective of the scope then focuses the light at the f ratio of the scope ie f7.5 for an ED80. If the front etalon is a 60mm aperture this restricts the ratio to 600/60 = f10 which is ideal for the PST mod.
If you wanted to use the bare PST etalon, you would have to have an optical arrangement which presented a f30 (or so) beam to the PST etalon. This would infer using a x3 teleconvertor or similar in front of the PST etalon.
IMHO it would be just as easy to use the original PST set to -200mm as a DS arrangement.

[MalVeauX]

Makes sense to me.

Looks like I'll just have to get a 2nd 60mm solarmax to double stack, if it's warranted.

Very best,

[Merlin66]

marty,
If you find a good pre-Meade external SM60 (not the SM60ii) let me know...I've been chasing one for a couple of years!

[Merlin66]

As I mentioned, tuning the SM60/ PST DS is ongoing....
This shows, under poor seeing the current status.

Sun_110846_l4_ap3912_conv.jpg (112.75 KiB) Viewed 6469 times

[marktownley]

That's a nice image Ken! Try ticking the 'cropped' box on AS3 to get rid of the black and white edges around the edge of the image.