Gene Baraff
sage
Reged: 03/22/09
Posts: 246
Loc: Berkeley Heights, N.J.
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What is the difference between the H(alpha) Coronado Filters used to Double-Stack the PST, the SolarMax 40 Solar Telescope, and an SM 40 Solar Filter?
Thanks in advance.
Gene Baraff
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brianb11213
Carpal Tunnel
Reged: 02/25/09
Posts: 2113
Loc: 55.215N 6.554W
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The double stacking component doesn't need an energy rejection filter as that is already provided by the primary etalon. Other than that .... ? is there a need to have the tilt different to the primary (i.e. tuned to a slightly different centre band) in order not to get reflections between the etalons?
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Gene Baraff
sage
Reged: 03/22/09
Posts: 246
Loc: Berkeley Heights, N.J.
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Quote:
What is the difference between the H(alpha) Coronado Filters used to Double-Stack the PST, the SolarMax 40 Solar Telescope, and an SM 40 Solar Filter?
Thanks in advance.
Gene Baraff
Let me rephrase:
I meant to say: The differences between Coronado Filters used to Double-Stack the PST, to Double-Stack the SolarMax 40 Solar Telsecope, and to Double-Stack an SM 40 Solar Filter.
The differences (if any) could be mechanical (e.g., the size of the thread the filter screws into) as well as optical.
Thanks for the reply already given and thanks in advance for replies yet to come.
Gene Baraff
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BYoesle
Pooh-Bah
Reged: 06/12/04
Posts: 1115
Loc: Goldendale, WA USA
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The SM40 telescope uses and SM40 front etalon, and is double stacked with another SM40 etalon (plus TMax tilt/tuner and an adapter ring).
I believe the doulble stacking filter for the PST is another SM40 etalon (which has an ERF and TMax, but doesn't require an adapter ring). The only difference I recall at one time between a PST DS etalon and an SM40 DS etalon was the price...
--------------------
Bob Yoesle 
You are a child of the universe,
no less than the trees and the stars...
And whether or not it is clear to you,
no doubt the universe is unfolding as it should.
Desiderata
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Fish
sage
Reged: 10/13/07
Posts: 470
Loc: Norridgewock, ME
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Good evening,
AFAIK there is no fundamental difference among the (3) filters mentioned. For best performance, however, if an SM40 is being used with a second SM40 the two should be tested as a pair to ensure they work together as expected. Small differences in manufacturing, although within design tolerances, can result in less than desired performance when coupled to another unit.
This does not apply to adding an SM40 to a PST as the internal etalon is typically of a wider bandpass. As for the price difference? Only Meade knows . . .
Regards, Marc
--------------------
Goseck Observatory
Kunming 152 f/5.9 & Baader Wedge
Orion ED80 & LS75FHa2/B1200
Meade 102ED & LS18CaKMDd2
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Gene Baraff
sage
Reged: 03/22/09
Posts: 246
Loc: Berkeley Heights, N.J.
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Could anybody measure the external male thread diameter on the Coronado SM40 they use to double-stack their PST?
Could anybody measure the external male thread diameter on the Coronado SM40 they use to double-stack their Coronado SolarMax 40 solar scope?
The answers would go a long way to helping me sort this out.
Thanks.
Gene Baraff
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marktownley
Carpal Tunnel
Reged: 08/19/08
Posts: 2266
Loc: West Midlands, UK
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I know when I went up to visit Robert Arnold in may we tried to use his SM40 filter to double stack on my SM40 scope. It wouldn't screw directly on and some other 'adapter' was quite clearly needed.
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robert_arnold
Pooh-Bah
Reged: 11/08/05
Posts: 1415
Loc: Isle of Skye, Scotland
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The SM40 standard filter with T max tuner that Mark mentions above fits on a PST directly (but not onto the SM40 scope as he says). If that helps you?
--------------------
ED80 ED100 Helios-120+105-ERF PST SM40 DMK31AF03 CaK-B600 LS75F/B1200
www.robertarnold.co.uk
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Gene Baraff
sage
Reged: 03/22/09
Posts: 246
Loc: Berkeley Heights, N.J.
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Quote:
The SM40 standard filter with T max tuner that Mark mentions above fits on a PST directly (but not onto the SM40 scope as he says). If that helps you?
Yes it does. Thank you. A pattern is starting to develop, but I'm stilll hoping for the two measurements i asked for.
Gene
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robert_arnold
Pooh-Bah
Reged: 11/08/05
Posts: 1415
Loc: Isle of Skye, Scotland
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Ok Gene! I found the dial guage. 54.5mm ID on the front of the SM40 and 51.8mm OD on the back end of the T max tuner.
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ED80 ED100 Helios-120+105-ERF PST SM40 DMK31AF03 CaK-B600 LS75F/B1200
www.robertarnold.co.uk
Edited by robert_arnold (10/25/09 03:18 PM)
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robert_arnold
Pooh-Bah
Reged: 11/08/05
Posts: 1415
Loc: Isle of Skye, Scotland
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I think 1mm pitch
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Gene Baraff
sage
Reged: 03/22/09
Posts: 246
Loc: Berkeley Heights, N.J.
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Quote:
I think 1mm pitch
Thanks.
Can you give me the diameter? I need that as well.
But tell me also, the measurement you gave - which Coronado product dues that double stack on?
Maybe I'm being stupid, but I suspect that the various units have different thread specs. In fact, you said, right after Mark Townley's post - that for sure, the units were not all interchangable.
Sorry to be a nuisance, but somewhere among you forum members, there IS the answer I need.
gene
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robert_arnold
Pooh-Bah
Reged: 11/08/05
Posts: 1415
Loc: Isle of Skye, Scotland
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Not a nuisance... I can sympathise with trying to sort things out and make things fit. I spend quite a lot of time on that. I posted my diameter measurements before the pitch message.
It is a standard SM40 filter and tuner ring which fits directly onto a PST front end.
Good luck
Robert
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ED80 ED100 Helios-120+105-ERF PST SM40 DMK31AF03 CaK-B600 LS75F/B1200
www.robertarnold.co.uk
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marktownley
Carpal Tunnel
Reged: 08/19/08
Posts: 2266
Loc: West Midlands, UK
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Out of curiousity I unscrewed the etalon off my SM40 to see if it would screw into the objective end of my CaK PST - assuming it is the same for the CaK PST as the Ha PST. It does screw directly in but without the tilt wheel mechanism.
Does this mean if I bought a SS PST I would be able to DS it by using the etalon off my SM40? Or does it have to have to have the tilter on it to move relections out of the fov - if this is applicable with the PST...
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Gene Baraff
sage
Reged: 03/22/09
Posts: 246
Loc: Berkeley Heights, N.J.
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Quote:
Out of curiousity I unscrewed the etalon off my SM40 to see if it would screw into the objective end of my CaK PST - assuming it is the same for the CaK PST as the Ha PST. It does screw directly in but without the tilt wheel mechanism.
Does this mean if I bought a SS PST I would be able to DS it by using the etalon off my SM40? Or does it have to have to have the tilter on it to move relections out of the fov - if this is applicable with the PST...
It's hard for me to imagine use of any of the SM filters without the tilt wheel mechanism. (Speaking with no experience on this point.)
Aside from the matter of getting the unwanted reflection out of the field of view, there is the issue of tuning to the correct pass band.
If there is someone out there who REALLY knows, his opinion on this point would be very welcome here.
Gene Baraff
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BYoesle
Pooh-Bah
Reged: 06/12/04
Posts: 1115
Loc: Goldendale, WA USA
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When double stacking a telescope with an internal etalon (PST, etc.), any front mounted etalon will achieve the purpose of double stacking. Indeed, a rear mounted etalon could be used as well (at the proper f-ratio using a telecentric), such as a DayStar or Solar Spectrum filter.
Quote:
Does this mean if I bought a SS PST I would be able to DS it by using the etalon off my SM40? Or does it have to have to have the tilter on it to move relections out of the fov
When DSing by a second etalon up front, a tilt mechanism is required (only) to remove the internal reflections it generates -- generally in any DSing scenario the actual final tuning of the system is achieved with the etalon that has the more precise passband or tuning mechanism.
Quote:
Aside from the matter of getting the unwanted reflection out of the field of view, there is the issue of tuning to the correct pass band.
When using two front mounted etalons for DSing, one should evaluate which of the two etalons requires the least amount of tilt to be on-band. This is the "primary" etalon, and should be mounted next to the objective. The other etalon becomes the "secondary" etalon which is attached with the appropriate adapter to the primary etalon.
When placed on the primary etalon, the pre-tuned secondary etalon should be rotated to the position that places the internal reflections as far as possible off-center, so that minimal tilting will then remove them completely from the field of view. This keeps the tilting to a minimum from the ideal on-band position for the secondary etalon.
This is essentially the "matching" process used by the manufacturer. The final fine-adjustment or on-band tuning is then acheived by tilting only the primary etalon and leaving the secondary etalon tuner alone...
--------------------
Bob Yoesle
You are a child of the universe,
no less than the trees and the stars...
And whether or not it is clear to you,
no doubt the universe is unfolding as it should.
Desiderata
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brianb11213
Carpal Tunnel
Reged: 02/25/09
Posts: 2113
Loc: 55.215N 6.554W
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Quote:
I suspect that the various units have different thread specs.
More than likely ....
FWIW the PST front end thread is a standard camera lens 52mm fitting (52mm dia x 0.75mm pitch). Sorry but I don't have sight of or access to the others.
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Gene Baraff
sage
Reged: 03/22/09
Posts: 246
Loc: Berkeley Heights, N.J.
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I've tabulated all the answers given here so far, plus three other pieces of data from other sources.
The only measurement that is NOT in my list is the thread size on the front of the SM 40 Solar Scope. In order to get wider attention to this question, I'll start a new thread on this forum - one that asks that question out and out.
Thank you all again for your help.
Gene Baraff
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RikkiHocking
Vendor - Lunt Solar Systems
Reged: 02/15/08
Posts: 32
Loc: Tucson, AZ
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Its been awhile but when I worked for Coronado the specs for the SM40, PSM40 and DS-SM40 were the same. There was no mechanical difference between them.
Thanks,
Rikki Hocking
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Gene Baraff
sage
Reged: 03/22/09
Posts: 246
Loc: Berkeley Heights, N.J.
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Quote:
Its been awhile but when I worked for Coronado the specs for the SM40, PSM40 and DS-SM40 were the same. There was no mechanical difference between them.
Thanks,
Rikki Hocking
Thanks for the reply, Rikki.
Never expected you to turn up here.
Your having worked for Coronado and now being (almost?) the chief contact with the same people under a different name - reminds me of a friend whose grandfather many years ago lived in Poland, Hungary, and Czechoslovakia without ever having moved from one house to another. 
Thanks again.
Gene
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