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Solar convert!

The_PSY3NTIST

By The_PSY3NTIST
in Observing - Solar

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The_PSY3NTIST

The_PSY3NTIST

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A very kind friend let me borrow his old PST today and although it has the rust problem on the objective it blew me away! Thinking of selling up and converting the Evostar 102mm into a HA solar scope. I've seen some kits online but its all new to me so was wondering if anyone could point me in the right direction and offer some advice on what it entails please :) I have been missing out :p

Thanks

David

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The_PSY3NTIST

The_PSY3NTIST

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Thanks :) I'll pm you my email address.

I'm finding it very addictive!! I've booked a day off work tomorrow to have an imaging day :) hopefully my little trusty neximage (although colour) will give me my first ha image. I tried with the dslr but just couldn't get focus. Was like the camera needed to be a few millimetres closer.

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Merlin66

Merlin66

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David,

The Stage 1 mod replaces the whole of the front end of the PST (objective and gold tube).

Note: The final focus position in a Stage 1 mod is exactly the same as the original PST - if you can't focus your camera in the PST, it still will not focus after a Stage 1 mod.

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The_PSY3NTIST

The_PSY3NTIST

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So I bought the pst. Just need an erf now.. 375 euros :s (the missis isn't going to be happy) does anyone know anyone that has done the stage 1 mod to an Evostar 102mm? Would be good to get some guidance on measurements before I hack my refractor up wrong. Don't want to mess it up lol.

Can't wait to get it done :)

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Merlin66

Merlin66

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The key is to position the etalon at the "majic" 200mm inside the prime focus of the donor OTA. This usually means replacing the focuser with a spacer or cutting the OTA.

Remember a Stage 1 mod will NOT improve/ change the final focus position relative to the black box, and will always, due to the etalon acting as an aperture stop, give you an f10 system. ie 102/800 would end up 80mm f10

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The_PSY3NTIST

The_PSY3NTIST

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Great info. I have sourced a new objective for the pst from the new version (blue objective) could I use this on the older pst until I raise the funds for a d-erf for the stage 1 mod. There are no extra filters in the light path that I need to know of is there? It's at a good price to make a temporary fix if it is a straight interchange.

Thanks again.. I'm obviously in the right place! :)

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Merlin66

Merlin66

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David,

CAUTION!

The old "gold" PST objective had a built-in ERF coating, the later "blue" objective HAS NO ERF coating.

To use this blue objective you need to add an ERF element before the small blocking filter in the eyepiece holder.

We have been unable, as yet, to source suitable "mini-erf's"......

An up front Baader D-ERF is the way to go.

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The_PSY3NTIST

The_PSY3NTIST

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Thanks merlin. Where is the energy rejection in the new pst? Is the etalon different in the two pst's? The other option I have is a full new pst missing the etalon. Could I put the etalon from the older pst in the new one? Sorry for all the questions and thank you for all your help. Greatly appreciated :)

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The_PSY3NTIST

The_PSY3NTIST

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So everything is there minus the etalon :) should give me a good as new pst to play with till I can afford to go straight in for the stage 2 mod. In the mean time I can get the 5mm bf mounted in a diagonal from my old one too so I can get the d-erf first and do the mod then save up for a bf10 or bf15.

Thank you so much for all your advice!

David

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The_PSY3NTIST

The_PSY3NTIST

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So new pst came today :) down side is I can't get the old one apart lol. Going to have to be a vice job at work I think, managed to turn it about 1/2 inch then it locked up again. Think I underestimated all the locktite fuss. I'm dreading trying to get the etalon off the gold tube!

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The_PSY3NTIST

The_PSY3NTIST

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Took it to work today where I have a vice available and strap wrenches, Still struggled! The gold tube came off first leaving it very awkward to get in and remove the etalon from the black box. After about half hour and a few choice words that cannot be repeated on here the locktite was finally defeated :) The new pst is now assembled and looks brand new ( it almost is as the person I bought it off just stole the etalon for his stage 2 mod so the parts I got were never used :) )

I still have slight underlying concern about the blocking in the pst. If anyone is positive that the etalons are exactly the same in terms off filtering on the old and new please shout up :)

What makes the new one clear view as apposed to the old one that is not?

Thank you so much for everyone's help and guidance :)

yjuze9y5.jpg

Also one last thing. Does this look right? Looks like the blocking filter is backwards to to me? Probably not lol but does the blocking filter look like a mirror in the new pst's? The old one just looks red. Here's a photo?

Many thanks

6uhepesu.jpg

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allcart

allcart

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To my knowledge the etalons are the same. If you have put your etalon in the new pst, and the new pst already has a blue lens then you are good to go. As merlin66 explained, the old gold lens pst has an erf coating on the lens that when rusty will cloud the image. The blocking filter will also have a slightly different arrangement.

On the newer blue lens pst's the erf is built into the blocking filter, thats why they look different. Providing you are using the newer blue lens version you are ok. You cannot just swap a rusty gold lens in an old pst for a blue lens without adding another erf up front.

Merlin66 will hopefully confirm this .

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The_PSY3NTIST

The_PSY3NTIST

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Yes I have swapped everything over :) just wondered if anyone could look in their new pst and see if they have the same as the last image I posted. The side you can see when it is fully assembled looks poor with a blob of silicone. Just looks like it should be facing the mini erf

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