Hello and greetings from Italy. I0ve really appreciated this forum and whanto just say thnk you to all of you.
I would modified a coronado PST into a new Frankscope using my Maksutov 102. Of course I have a pst and and ERF filter of 75mm.
I have just few question for you guys:
1. First of all... is it possibile to use a Mak 102 for a scolar scope? No danger to the mirrors or other problems may occur?
2. If 1 is GO, than I'm guessing about the focus point. As I note the focus point of the mak is just on the back of the OTA and then I just need an daptor to fit into the threads of the etalon housing. I'm going to have a 3d stamp of it.
3. If 2 is Go connect the etalon, connected to the Ota, to a diagonal with the BF of the pst. How much the adaptor tube shoud be long? Missing answer...
Thank you very much for your help, clear skies night and day!
Luca
PST and Mak 102
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MalVeauX
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Re: PST and Mak 102
Hi,
1) Yes its possible, however you would need to use a full aperture energy rejection filter with it, and this is very costly even at 102mm. If you have a Baader 75mm ERF you could use that but you will obviously lose a lot of aperture doing this. Quite frankly at 4" aperture, I would say don't bother using a Mak or SCT and instead use a 4" achromatic doublet refractor, they're inexpensive, do not need full aperture ERF and are much easier to do all of this with. Mirror based optics will need full aperture ERF and it just gets very expensive and that's not worth it at all with small apertures where refractors can readily deal with this for much less cost without it.
2) Bringing a Mak to focus moves the primary mirror, how it will focus is entirely based on what you're configuring in the imaging train. If you sorted out the energy rejection needs, yes, you just create a module and insert it and move your mirror until it reaches focus. But this is the least of your concerns until you sort out the energy rejection needs regrading the mirror based optic first.
3) This depends on how you set it up. There's two ways to do a PST mod. One is to use the PST etalon and its native collimating lenses which are good for F10. The other way is to get rid of the collimating lenses entirely and put the PST etalon in a long focal-ratio telecentric light cone via a 4x telecentric amplifier (like Baader 4x). The collimated version will have a sweet spot that is small. The telecentric version will not have a sweet spot. It's more ideal, costs more to setup, and could be worth it if you had a very good PST etalon to do this with.
I would not bother trying to make a small Mak work for H-alpha with PST modding. Use a refractor at these small apertures. At 8 inches or bigger, then it would make more sense to try to do it and would need a big full aperture ERF to make this worth while. But at small apertures, its just not worth the expensive to get a small aperture Mak to do this.
You also need a very good PST etalon to even bother doing all this. Most of them are bad. A few are quite good. But you have to get one that is really good to make this worth while before bothering doing anything else really. And you still have to figure out how far you want to go with it to get the most out of it (such as telecentric pathway).
Also, you don't have to use PST. There are other air spaced etalon options that are easy to mod. Lunt 50 is another easy one. You still have the full aperture ERF needs if considering using a Mak/SCT/Newt. I would not bother with these, again, at this small aperture. Just use a refractor.
Very best,
1) Yes its possible, however you would need to use a full aperture energy rejection filter with it, and this is very costly even at 102mm. If you have a Baader 75mm ERF you could use that but you will obviously lose a lot of aperture doing this. Quite frankly at 4" aperture, I would say don't bother using a Mak or SCT and instead use a 4" achromatic doublet refractor, they're inexpensive, do not need full aperture ERF and are much easier to do all of this with. Mirror based optics will need full aperture ERF and it just gets very expensive and that's not worth it at all with small apertures where refractors can readily deal with this for much less cost without it.
2) Bringing a Mak to focus moves the primary mirror, how it will focus is entirely based on what you're configuring in the imaging train. If you sorted out the energy rejection needs, yes, you just create a module and insert it and move your mirror until it reaches focus. But this is the least of your concerns until you sort out the energy rejection needs regrading the mirror based optic first.
3) This depends on how you set it up. There's two ways to do a PST mod. One is to use the PST etalon and its native collimating lenses which are good for F10. The other way is to get rid of the collimating lenses entirely and put the PST etalon in a long focal-ratio telecentric light cone via a 4x telecentric amplifier (like Baader 4x). The collimated version will have a sweet spot that is small. The telecentric version will not have a sweet spot. It's more ideal, costs more to setup, and could be worth it if you had a very good PST etalon to do this with.
I would not bother trying to make a small Mak work for H-alpha with PST modding. Use a refractor at these small apertures. At 8 inches or bigger, then it would make more sense to try to do it and would need a big full aperture ERF to make this worth while. But at small apertures, its just not worth the expensive to get a small aperture Mak to do this.
You also need a very good PST etalon to even bother doing all this. Most of them are bad. A few are quite good. But you have to get one that is really good to make this worth while before bothering doing anything else really. And you still have to figure out how far you want to go with it to get the most out of it (such as telecentric pathway).
Also, you don't have to use PST. There are other air spaced etalon options that are easy to mod. Lunt 50 is another easy one. You still have the full aperture ERF needs if considering using a Mak/SCT/Newt. I would not bother with these, again, at this small aperture. Just use a refractor.
Very best,
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marktownley
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Re: PST and Mak 102
Personally, i'd ditch the Mak and get a frac...
http://brierleyhillsolar.blogspot.co.uk/
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