Appenzellersonne, "small" scope modification

[swisswalter]

Hi all

first I ask for forgiveness for the bad weather ahead in Europe. I guess it'll take 6 weeks until the weather god has calmed down again.

My newest plans are moding this scope to a Ha-gun (150/3000, some 50 years old)

First inspection in the living room after a 500 miles drive to pic it up





Well there is need of some modifications or does anybody know of a 1,3 " focuser to hold this eyepiece ?






this special focuser locking needs fixing as well (fiberboard, stone, felt and chipboard)







the special feature of that scope is the length of the focuser, 1000 mm inward travel



I'm back in 4 weeks, hopefully, for the first light

[marktownley]

Oh wow! thats fantastic! B)

That must have cost you a fair few pairs of shoes walter, my wife thinks my 127mm frac is huge... This one is a beast! :

[swisswalter]

Hi Mark

thank you very much for your fast feed back. Yes, expensive in point of pairs of shoes. The deal was 1 week wellness holiday in a spa against the scope

[marktownley]

lol, I know what you mean. My PST mod cost me a weeks holiday somewhere (hasn't decided where yet) at the start of June in the UK, I might not have mentioned it's the same week as the transit of Venus though I can forsee a cottage somewhere with a sea view to the north east... :whistle:

[Merlin66]

Whooo
I thought my "Big Yin" 150/1200 was BIG......
I think the answer would be to do a re-build of the rear section and end up with an adaptor plate which would take a TS 2" Crayford...
What do you have in mind for this?? The ultimate PST mod???
At a base of f20 this could be very interesting!!!
With one of Cata's "new" E-ERF? (E for Economy!)

[swisswalter]

Hi Ken

thank you very much. I'm so excited that I can't wait to have first light.

Yes I will have let done an adoption of the focuser to a 2" crayford 1:10. I'll use my 150 mm D-ERF I already have.

Me too I wonder what f/20 is showing with this tiny PST etalon. Maybe a disappointment or a big move forward or as usual in life, something in between.

[swisswalter]

Hi Mark

you are a fox north east view :whistle: I won't reveal your secret

[Merlin66]

Hmmm
Interesting....
With the 150 D-ERF it will still function as a f20 system, but...
The size of the solar disk at the etalon will be 30mm (3000/100) plus the 200/10=20mm this is obviously much larger than the etalon so there will be significant vignetting.
Infact, at f20 it may be worth while considering the removal of the front and rear etalon lens and use the "bare" etalon in a f20 beam.....

[swisswalter]

Hi Ken

thank you very much for that hint. I have not thought about that. Yes that will be mod phase 3, as soon as I have seen that mod 2 is working. I'll come back to that issue when I have to remove the mini ERF and the front and back lens.

I have still another option. A spare LUNT LS50 for mods

What would you be doing, granted the scope works at all, which has not yet been profen

[Photonist]

Wow, Walter. That’s serious modding. The Lunt LS50 option would be very interesting.

Viljo

[peter drew]

Amazing telescope Walter. Does it actually say 3000mm FL on it, I ask this as telescopes of this design often include erecting systems which extend the focus position, the native focal length of the could be shorter than F20.

[swisswalter]

Hi Chaps

thank you very much for your input.

The FL is nativ 3000 mm , I measured it, no lenses between objektif and ocular at all.

It has a very special desing. You can shorten it down to 2000 mm and so it fits in almost any car.

Yes Cai Uso deflection could be a big problem, on the other hand I have already a solution to it, if I'll get into problems. I'll construct something like a bridge stiffening with wires

I'll shoot pics of the lens and present them here, but only if the first light is reasonably good, otherwise it just was a miss buy

[depes]

My God... :S

You are incretible...Walter.. :blink:

[JohnM]

it may be worth while considering the removal of the front and rear etalon lens and use the "bare" etalon in a f20 beam.....

What happens if those lenses are removed? How does that affect focusing?
I'm curious now.

[colinsk]

This would be a great scope for a custom telecentric and the LS50 etalon!

[swisswalter]

Hi Peter, John and Colin

thank you very much.

Colin, would you show us in a little drawing how you see the setup. Has it to be a custom made telecentric, would a Baader TZ4 not work?

[Merlin66]

John,
A bare etalon at f25 or so has been used in prior mods. I haven't seen any images from such a system. Based on previous discussion (check out the telecentric threads)it would be marginal at f20....
Other than the etalon filtering effects, the other other thing would be an reduction in the back distance due to the amount of glass "in the converging beam" (similar to the effect of a filter in a "normal" telescope. This is approx 1/3 the thickness; if the total etalon plates are say 15mm thick this would give a 5mm reduction.
The bare etalon, in the 150/3000 scope would be placed close to focus to minimise vignetting.

[Derek Klepp]

Brilliant aquisition Walter.Most Daystar filters focus at F20+ have you got one of those floating around. I don't know much about this mod stuff but that scope looks promising.

[swisswalter]

Hi Ken, Hi Derek

thank you very much.

@Derek I used to have a Daystar, then sold it, because it makes more fun with the PST mod's. Now I have another Daystar filter, possibly broken (blind chicken thread), but I have yet to test it.

It all takes some time

[swisswalter]

Hi Apollo

thank you very much. I'll have a read later

[MapleRidge]

Hi Walter

That is quite a scope...that will take quite a mount...that might take a month at the spa

Hope your plans to mod it go well.

Brian

[swisswalter]

Hi Brian

thank you very much. Yes 1 month of spa or 100 pair of shoes

I'm on the way fixing little things on the scope. I'm expecting the focuser adapter arriving in 3 weeks (honestly, I can't wait, it hurts)

[swisswalter]

Hi all

it took a long time to get all the parts in the right condition, some of them had to be returned 3 times to the vendor until they matched the specs

today was the first setup and the first light:





notice the counter weight hmy: :woohoo:







the first pic (note seeing very horrible)






Now I have to work on a decent solution for the balance on the mount and alter the last aperture (too much scattered light, straiglight) . Later on maybe I mount a motorfocus.

I found it very difficult to find focus, there was so much way in betweeen some focus and less focus, with my f/10 systems there is no question about focused or not focused, maybe you have a hint

Attached files

[Merlin66]

Walter,
I have the same issues focusing the spectroscopes...
The depth of focus (for 1/4 wave accuracy) is somewhere around:
delta f = 1.6 F^2 lambda
where F is the focal ratio and lambda the wavelength.
i.e. for a f10 system at green light this is around 0.22mm, so with your "new" friend it will be much more.....

[swisswalter]

Hi Ken

thank you very much. That is a very good explanation, which I as a chemist can understand. I am going into it the day after tomorrow. I'm still hoping for that cloud gap in the morning of the 6th

[colinsk]

Walter,
I have the same issues focusing the spectroscopes...
The depth of focus (for 1/4 wave accuracy) is somewhere around:
delta f = 1.6 F^2 lambda
where F is the focal ratio and lambda the wavelength.
i.e. for a f10 system at green light this is around 0.22mm, so with your "new" friend it will be much more.....

I thought that long focal ratio scopes were more forgiving to focus error? That is at least what my DOS ray tracing software says.

[Merlin66]

Yes,
that's correct. It varies as the square of the f ratio.
eg At f4 it's 0.035mm, at f8 it's 0.141mm and f10 gives 0.22mm

[colinsk]

Ah, thank you Ken. :thanx:

[sullij1]

Wow! Simply amazing!

[swisswalter]

Hi Joe

thank you very much

[swisswalter]

Hi Ken

pic 09244, close up of the focuser, is the PST mod