SolarChat!

I removed all the lenses from the etalon. You need the telecentric x this system I designed.

Thanks, but I don't understand it completely. Normally you would say that you need to put the first etalon minus 20 cm of the focal point of a F10 scope.
But if you change the front lense of the etalon with another concave lens you can get away with something else.

Then I repeat I do not use any lens. The original lenses have been removed and 4. in their place use a 5x telecentric made specifically for my focus.

You could change the lens but still the result would not be good because the beam would not reach the correct inclination of the original collimated beam.

That is cool! I allways thought it was necessary, but apparently it is not.
I am sorry, one other question. Can you just use the scope now as a F30?

Yes

Thanks!

Bart,
The majic 200mm was based on the standard front barlow lens giving a parallel collimated beam to the etalon, and the rear lens re-imaging to the focus.
If both lenses are removed, then you have a degree of freedom....for optimum performance the etalon needs to be in a beam >f25, close to f30 is good.
This can be achieved with a telecentric barlow ie the x4 with an f7.5 scope and then select the re-focusing lens to suit your requirements....

Aha. So I am mixing things up... So instead of a collimated beam through the etalon you aim at f25 - f30. But then you have to remove both lenses. Like that?

Yeah, a perfectly parallel and collimated would be ideal, but around f30 works well. The rear lens could be retained to bring the final focus 200mm behind the etalon, or replaced with one to suit your system.

Thanks Merlin. Now I also understand why all the sct owners are talking about f30...... steep learning curve. (-;

Hi Galosimo and Merlin,
Could one of you tell me why it is useful to place the blocking filter before the etalons?
Thanks, Bart.

My is before the telecentric so I collect the beam before, when it is smaller and i just need a BF15

Bart,
The ERF is generally mounted in front of the etalon.
The blocking filter is mounted behind the etalon. I've never seen an application were the blocking filter was mounted before the etalon......

The important thing is that it works. Experiments serve this.

That is what I thought Merlin. But Galosimo has put it before the telecentric and it works. If I look at the Beloptik site he seems to do the same: http://beloptik.de/de/left/h-alpha-system-2/

Blocker is infront of the telecentric in my Daystar setup...

Hmmmm
OK.
IF the blocking filter is larger than the etalon, then I see it could be mounted in front of the etalon.
All the blocking filters I have experience with have always been smaller than the etalon.

My experience with PST and the "standard" mods is beginning to show my limitations.

Yeah the Quarks have their BF in front ... Totally Weird imho !! but obviously works well and reflects most of the IR.

Is this not the PST Mod Holy Grail ... the DS Mod ... Respect if ever it was due.

Brian

My bf is smaller than the etalon BF = 15mm, etalon 20mm. The doublestuck as I set up with telecentrica works fine.