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LUNTINADO combo question

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#1 ASTROTRUCK

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Posted 23 April 2013 - 12:34 PM

ok all - it has been discussed in the past but i am still not sure which combo is safe -
i have the 60 etelon & 1500 blocking filter BOTH by mexican meade.

am always concerned that my bf might become a rust issue even though i use plenty of silicate but summer observing is damp - i let the etelon & bf dry out as best as possible but need to pack them away after about 1 hr of drying after a damp session.

so ...not wanting another mexican meade bf ( NOT blaming them for the dampness but for other bf issues )can i then buy a lunt bf to be mixed with the mexicam meade etelon ??

what is the safe luntinodo combo ???

THANKS ALL

#2 Jim Lafferty

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Posted 23 April 2013 - 01:48 PM

The Luntanado combo is a Lunt scope with internal etalon and Lunt blocking filter, doublestacked with an external Coronado etalon (pre or post Mexico). The configuration as I just described is safe. You can see images of this set up on the equipment page of my website.

Jim

#3 Fish

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Posted 23 April 2013 - 07:01 PM

Good evening,

In this era of Lunt / Coronado mixing, the only combination that can cause potential problems is:

An all-Coronado etalon stack with a Lunt blocking filter

This is due to the differences in the designed Free Spectral Range between the two manufacturers and not any deficiencies or quality issues.

Regards, Marc

#4 Bill Cowles

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Posted 23 April 2013 - 08:24 PM

Yep, cracked my Lunt blocking filter. :(

Bill

#5 Bill Cowles

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Posted 23 April 2013 - 08:30 PM

Here is my Lunt 60 and a really old Solarmax 60 filter, works great. Got this idea from you, years ago.

Bill

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#6 Bill Cowles

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Posted 23 April 2013 - 08:37 PM

Since I also had the 50mm Lunt, why not a Tri-Stack Luntinado. :smirk:

Bill

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#7 Spectral Joe

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Posted 24 April 2013 - 10:12 AM

Good evening,

In this era of Lunt / Coronado mixing, the only combination that can cause potential problems is:

An all-Coronado etalon stack with a Lunt blocking filter

This is due to the differences in the designed Free Spectral Range between the two manufacturers and not any deficiencies or quality issues.

Regards, Marc


Please, if you would, describe the problems, and their origin.

#8 brianb11213

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Posted 24 April 2013 - 11:11 AM

Good evening,

In this era of Lunt / Coronado mixing, the only combination that can cause potential problems is:

An all-Coronado etalon stack with a Lunt blocking filter

This is due to the differences in the designed Free Spectral Range between the two manufacturers and not any deficiencies or quality issues.

Regards, Marc


Please, if you would, describe the problems, and their origin.

The issue here is that the etalon transmits a large number of wavelengths - a very tight, narrow wavelength range but repeated many times, like the teeth of a comb. The blocking filter has the job of isolating all but one of these transmission spikes. (And the energy reduction filter has the job of removing wavelengths which are way out of band.)

The Coronado etalons comb filter response has a shorter interval than those made by Lunt. The Lunt blocking filter, having a wider transmission waveband than those made by Coronado, therefore allows considerable "leakage" of transmission spikes from the etalon which are not tuned to hydrogen alpha, thereby reducing contrast very significantly.

Manufacturers make etalons and blocking filters as complementary units ... there should always be one etalon matched to the blocking filter in use. You can however add an extra etalon or etalons to the stack irrespective of the manufacturer.

#9 Aquarist

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Posted 24 April 2013 - 03:40 PM

Excellent explanation above.

#10 ASTROTRUCK

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Posted 24 April 2013 - 04:32 PM

"Manufacturers make etalons and blocking filters as complementary units ... there should always be one etalon matched to the blocking filter in use. You can however add an extra etalon or etalons to the stack irrespective of the manufacturer. " ... brianb



thanks - this suggests that my meade coronado is toast if my meade blocking filter goes bad & would need to wait 8-9 months for another meade blocking filter -
it also takes forever to receive a bf from meade.

at that point rather than waiting 8-9 months for another meade bf -
1) i can order a new lunt system external etelon & bf - THEN i use my meade etelon as a double stack with the meade etelon further from the objective than the lunt etelon. - the lineup being coronado etelon, lunt etelon lunt bf.

2) for external etelons - the stacked etelon further from the objective should be the etelon unmatched to the bf.

correct ??

3) the coronado etelon / lunt bf is a dangerous system as is the reverse lunt etelon & meade bf - i assume correct ??

good reason to care for that bf

thanks all

#11 brianb11213

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Posted 24 April 2013 - 05:19 PM

1) i can order a new lunt system external etelon & bf - THEN i use my meade etelon as a double stack with the meade etelon further from the objective than the lunt etelon. - the lineup being coronado etelon, lunt etelon lunt bf.

Yes ....

2) for external etelons - the stacked etelon further from the objective should be the etelon unmatched to the bf.

correct ??

Doesn't really matter what order the etalons are in. If only one is fitted with an energy reduction filter (ERF - looks like a deep red filter & in fact usually has a passband similar to a Wratten #29), this one should be the one nearest the sun.

3) the coronado etelon / lunt bf is a dangerous system as is the reverse lunt etelon & meade bf - i assume correct ??

Incorrect combination of BF & etalon will result in a "near-white-light" view rather than showing what you'd expect from a hydrogen alpha system but should not be dangerous to the eye PROVIDING that the correct ERF in used in conjunction with the blocking filter.

#12 Spectral Joe

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Posted 24 April 2013 - 07:44 PM

I must admit, in my speed reading the beginning of this thread this morning I had assumed the subject was a Luntanado, in the sense that Jim described. That is the only such combination I have seen, and it makes sense, since it retains all of the essential components. I have written here before (http://www.cloudynig...&Number=5057295) on the Lunt-Coronado combination, and on other occasions as well. I am a big fan of showing things mathematically, and much prefer when numbers are given instead of generalizations. As for Bill's cracked blocking filter, I suspect the absence of an appropriate energy rejection filter is most likely to blame there. Blindly (no pun intended) swapping parts can lead to these sorts of problems. Get the numbers, learn how they relate and stay out of trouble. My favorite Lord Kelvin quote, from 1883:

I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be.

#13 ASTROTRUCK

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Posted 25 April 2013 - 07:34 AM

OK THANKS FOR HELP - extra silicate is the way to go with the damp summers then if necessary order a lunt system & use the meade as the double stack -
just not thrilled with the step of removing the erf but then would replase it with a derf

THANKS AGAIN

#14 BYoesle

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Posted 25 April 2013 - 11:58 AM

When you double stack, you are not only decreasing the FWHM bandpass, you are also significantly suppressing the transmission profile “wings” near the base of the transmission curve -- this is the way double stacking – with either identical of dissimilar etalons – works to eliminate continuum light and improve disk detail and contrast.

I don’t think there are any safety issues with doing a “Luntanado.” Perhaps a little additional background information will clear things up.

First you must understand that the two different etalons might have differing free spectral ranges - FSR’s.

FSR refers to the distance between the adjacent harmonic peaks of the etalon. The farther apart the etalon plates the narrower the bandpass will be (good) but the closer the side-band peaks will be. This would require a narrower bandpass blocking filter to block the side band peaks, which will be much more expensive (bad).

Etalon makers therefore try to balance etalon performance by selecting etalon plate spacings that will offer both good bandpass performance, along with a FSR which will permit use of a reasonably wide blocking filter. But this can vary from one design to another. Company A might have a 10 Angstrom FSR while Company B might have a design FSR of 15 Angstroms. Company A might therefore have a blocking filter with a 10 A bandpass, and Company B might use a 15 A bandpass blocking filter.

If you use company B’s 15 A wide blocking filter with company A’s 10 Angstrom FSR etalon, there is the potential that some of the light from the side harmonics of the etalon may make it through the filter system, degrading the contrast and detail seen. This is especially possible as the blocking filter’s transmission can shift with temperature, and even if narrower than the FSR, temperature drift might still allow a side band harmonic light peak through. This, as Brian states, would introduce continuum light, degrading contrast to a white-light continuum-like view.

This same issue might occur when double stacking two Company A etalons and using a Company B blocking filter. It would not occur the other way around, or when using the same company’s BF and DS etalon combination.

However, using a Company A and a Company B etalon results in the adjacent side band harmonics of each etalon being blocked by the other filter. Theoretically either blocking filter would be fine in this case. A blocking filter is still needed as some of the far-off etalon peaks still line up at their common intervals - in my example every 30 Angstroms. These common harmonics will go to the far IR and UV, and is why at least one ERF (for UV) and a blocking filter with an IR blocking ITF, are still needed...

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#15 marktownley

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Posted 25 April 2013 - 01:30 PM

just not thrilled with the step of removing the erf but then would replase it with a derf


If you're not 100% sure and don't have the understanding of the maths and the method behind solar scope mods don't do it. Go with the commercial route, even if it is more expensive.

#16 ASTROTRUCK

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Posted 25 April 2013 - 06:41 PM

not sure what you mean by the commercial route ??

would prefer the lunt to be with the erf to allow separate use single stack.

do you mean remove the erf from the meade etelon via some commercial company ?? no one here in canada to do this .

not sure of the process you meant.








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