Solar filter question

[NeilW]

Hi,

Can anyone explain why a Coronado SolarMax H-Alpha Filter costs as much, or more than a dedicated solar scope?

Cheers,

[pw]

What aperture/size is the SolarMax filter?
What size solar scope are you comparing it too?
Bandpass of each?

[brian nordstrom]

:) Well for starters there are 2 glass surfaces in the elation that are polished to better than 100th of a wave , and set at something like 1.25 microns + or - 100th of a wave (that's 100th of one millionth of a millimeter ) apart perfectly parallel to one another in 2 dimensions , perfectly reflective thus bouncing the solar light back between each other at 300,000 Km/second , too zoom in on Ha light's frequency ,,, WOAW !, then there is the BF ( blocking filter) , OTA , focuser etc .
These have to be perfect or people loose their eyesight as you are looking at a magnified image of the sun ,,, ouch .:help: .

And safety aint cheep when this is concerned , sorry to say .

Yep us humans are quite smart in some ways .

Brian

[NeilW]

Eg. Solarmax II 60 BF 10 is about $1499 US, and the equivalent Coronado SolarMax II 60 (BF10) scope is around $2k AUD. I know it's not quite comparing apples with apples, but I'm trying to determine whether to better to get a filter for an existing scope or get a dedicated solar scope.

[Merlin66]

Neil,
IMHO the ED80 would make a better solar scope than the Coronado SM60.
I have both.
The ED80 fitted with an up front SM60 filter and a BF10 gives fantastic views of the Ha sun.
(I in fact have two SM60 filters which can be double stacked on the ED80)

[pw]

The base scopes they use for the smaller Coronado and Lunt solar telescope are quite basic. Since they only have to work with a single wavelength they are not highly corrected and have simple objective designs.

[Poita]

I read that the objectives on solar scopes are made to have the correct wavelengths as the focus 'sweet spot' whereas a standard scope lens is made for a different wavelength sweet-spot.
Don't know if it is true, but my Lunt60 was better than the Coronado 60/BF10 combo on the ED80. Could just be the difference between manufacturers.

[Merlin66]

The only thing which is being discussed (on other forums) with solar "tuned" optics is the compensation of possible spherical aberrations between the objective and the internal collimating lens immediately prior to the etalon.
This discussion only applies to Ha scope designs using smaller internal etalons i.e. PST/ Lunt60 and above/ SolarmaxII series, for the others with external etalons a good achromat/ ED/ APO will work very well in the monochromatic Ha wavelength.
I haven't used a Lunt60, so I can't compare, but based on numerous PST mods and being a regular SM60 user, I'm surprised to hear you think it's better than the SM60 external etalon.

[NeilW]

Thanks Ken,

Is the adapter to fit the SM60 to the front of the ED80 purchased with the filter, or is it a separate item? And did you purchase them in Australia?

Regards,

[Merlin66]

Neil,
I bought my first SM60 filter s/h in the UK complete with the adaptor.
The second was bought s/h from Canada, again complete with an adaptor.
You should be able to either get one from the States, or get a local machinist to make one up.....

[NeilW]

Ken, I've just had a look on B&H Photo's site and I can get the 60mm filter, BF-10 blocking filter plus 65-95mm adapter shipped here for around $1,750 AUD. Sounds like a fair thing.

[Merlin66]

Sounds like the right selection.
Geee I paid more than that s/h for my filters a few years ago.....

[Paddy]

I don't know how the Coronado filters compare, but we had a very interesting time at Snake Valley in March comparing Malcolm Barker's Coronado 60 BF 10 solar scope, my lunt LS 50 50mm filter with BF1200 and a double stacked Lunt solar scope. Well the double stacked set up was extraordinary of course, but I couldn't believe the difference between the Lunt filter on my ed 80 compared to the Coronado. I know Malcolm won't mind me saying the Lunt very significantly better than the Coronado scope. Have a look at the Lunt prices (http://luntsolarsystems.com/blog/ls50fha-filter-systems) $1650 US for the LS 50 with B1200. Don't even think about the B 600. It's well worth the money for the bigger blocking filter.

Again, I haven't compared filter to filter, only to the coronado scope.

[Merlin66]

The Coronado Solarmax60 II design is now very similar to the Lunt 60 design...they both have small internal etalons...
No comparison to external etalons.

[NeilW]

All well and good, but getting hold of any of these etalons is a tad harder than I'd expected. Andrews reckon there's about a three month wait on getting them from Lunt, and B&H quote a 6 - 8 week wait on the 60mm Solarmax II filter set. :(:(