blocking filter

[Mark-V]

As a newbie looking into  hopefully getting a solar scope at some point in the future can someone explain in fairly simple terms what is the difference  between different blocking filters - what does it mean, and also when it says a solar scope is "double stacked" what does this mean as well please  ?

[Peter Drew]

Hello Mark.

 

Blocking filters, the components that further refine the output of the main etalon are generally graded in metric sizes, so a 5mm blocking filter has an aperture of 5mm, a 10mm has a 10mm aperture and so on. Depending on the focal length of the solar telescope's objective, blocking filters are calculated to give a full solar disc as seen in the eyepiece. "Double stacking" is the practice of using two etalons in tandem, this results in a reduced bandwidth and much increased contrast to the solar details albeit at a noticeably dimmer image.

[Mark-V]

So if finances are limited would it be better to get a scope with a larger blocking filter, or one that was double stacked, or a scope with a larger aperture ?

I suspect to get all 3 would be best  but that is probably way beyond my  finances  !

[Moonshane]

Yes indeed.  double stacked with a large blocking filter and large aperture is best although a compromise will also give excellent results.

E.g I have a pst stage two mod (Google for info) and use this in 100mm and a 60mm f10 scopes with a 5mm blocking filter.  I can see full disk with less resolution in the smaller scope and partial disk at greater resolution in the larger scope.

Ideally I'd like a 10-15mm bf for the larger scope but cannot afford one right now.

[Peter Drew]

I have 5mm, 10mm and 15mm blocking filters for my several PST mods. I've recently reverted to using the 5mm on my 6" F10 telescope. The reason for this is that I want to use binoviewers and to reach focus it needs a 2x Barlow lens screwed on to the front of the binoviewer. The high amplification that this produces, roughly 4x, means that even 40mm eyepieces produce 150x. Happily, the actual field at this magnification is similar to the 15mm BF at 150x and no binoviewer so nothing is lost, the whole field is on band and the two eyed high resoltion image is breathtaking. The 5mm blocking filter was designed for the PST and works very well. 

[Mark-V]

ok - well I  bought one !

in the end went for Coronado SolarMax II 90 Telescope (with BF30)   which came with a free set of cemax eyepieces. I decided I could get   the double stack etalon  adapter at a  (probably much !) later  date if funds ever allow  it

now all I need is the sun !!

[Tonynexevo925]

Congratulations Mark - I guess that's the sun gone for another week or two ???

Good luck and be interested to hear how you get on. 

Regards,

Tony

[Stu]

13 minutes ago, Mark-V said:

ok - well I  bought one !

in the end went for Coronado SolarMax II 90 Telescope (with BF30)   which came with a free set of cemax eyepieces. I decided I could get   the double stack etalon  adapter at a  (probably much !) later  date if funds ever allow  it

now all I need is the sun !!

So funds weren't THAT limited then Mark? ??????

Having looked through one of these, I suspect you won't be disappointed ??