Cheap 100mm Ha scope??

[Merlin66 (Ken)]

Definately 100% safe.
I have a choice of the ERF combo (see separate thread) or a Baader C-ERF.
I'll trial them back to back, see what the differences are, if any.
The other thought is to play around with a double stacked SM40/ PST etalon see if it can be done! THis has the potential of giving <0.5A with a 90mm aperture!!
I've made the "tube" length adjustable to accommodate the necessary barlow lens (to give a collimated beam through the SM40) and a 40mm f10 imaging section ( for the SM40 on it's own!) Let's see.....

[Merlin66 (Ken)]

YES!!! YES!!! OMG!!! YES!!!
First light with the EC90 at 5:48pm ( British time, its still daylight until about 8pm!) today!!!!!
It was ALL ( and more!) that it was designed to be.......
Only visual, need to screw a couple of strips on the sides to fit the HEQ5Pro mounting.....
The view through the BF10 is MUCH better than the BF5 ex-PST.....
With the 90mm f10 ( placing the PST etalon at 700mm) the field in the BF10 with a 21mm plossl is about 60% of the solar disk.
For the first time the "granulation" just jumps out, clear and tight!!!
The filament on todays photos just can't be missed; brightening around the spots... everything looks absolutely great ( wait a moment I'm about to wet myself!!!!!!!!!!!!!!!.... Ahhhh that's better!)
A quick tweek of the etalon and here we have the proms.... MUCH MUCH clearer than the PST and the SM40, God there's SO much detail!!!!!!!!!!!!
OK OK this thing works!!!!
A $50 lens from Surplus Shed, a couple of $$$ of customwood, $12 ( and two days!) on the paint and the $4 Wratten 25 and the $180 Uv-IR ( ERF COmbo) plus obviousy the etalon from the PST and (unfortunetly) the BF10 from the SM40 kit. It would have been MUCH cheaper if the BF5 gave better results..... I'll try it again tomorrow ( after a bit of viewing with the BF10!!!)
I can HONESTLY say if you've got a PST you ain't seen nothin yet until you put the etalon behind a safe ERF and larger aperture!!!!!
I'm happy it worked out soooooooo well.
Tomorrow's another day............

[Roger Davis]

Hi Ken, I have been following your construction with eagerness and am now very tempted to buy the last remaining PST on the shelf just to vandalise it for the Etalon. I have a nice 105mm f/12 lens and an old 120mm refractor tube with no optics sitting at home which now may have a new purpose in life. Here's to ATM!

[Merlin66 (Ken)]

First time in a long time that I've actually got excited about using a telescope; that's got to say something about the EC90!!!!!
It is possible to do this conversion without trashing the PST, so if things don't work out for you, the PST can be re-assembled and re-used.
So far the real key issues are:
1. A safe ERF (A Baader C-ERF or a Wratten#25+UV/IR combo)
2. Able to place the PST etalon 200mm inside prime focus.
3. Getting a good blocking filter to work with your system. The PST double BF at the eyepiece, seems to work OK, BUT I'd say, at the moment, the BF10 or maybe even a BF15 would work even better.
It's not a difficult conversion to do, and the improved resolution and contrast will blow your socks off!!
I think as we move towards the next solarmax you'll see more and more conversions.