I will respond per quoted comment,
First, my apologies if you find some of my comments offending, I feel clarity in pricing for services in posts regarding parts or services is important in order to avoid misinterpretation and confusion. I am blunt; I have alluded to that in the past. I will also continue to be blunt if I see posts that have the "appearance" of being deceiving. This is my nature.>>>RE: My point here is that ERFs are going to be an expensive endeavor regardless of location and that if anybody is determined to make their own they will find that out. Local vendors in many places are capable of providing the coating and polishing services but cost will often be prohibitive on a "one off" basis. If there is an interest from people from the same geographic region, they can band together to bring cost down. There is no cheap alternative for large ERF. It looks like Lunt is working on it but sell out as quickly as they can produce them. Yes, sourcing is tough. Other alternatives have been presented on the forum.>>>RE: Very good, glad you feel that way.>>>RE: Please continue to share your advanced knowledge and please post links to the source of the telecentric. I am certain many will be interested. Nobody should "shut up" but hopefully and in the interest of honesty, anybody who is offering services will post links or estimates of cost such that members can make informed decisions on purchases and services. Money is tight worldwide. From my experience here on Solar Chat, this is the expected norm and sharing of sources and pricing has proved very useful even for me.<<<<
There is no 'advanced knowledge' on this side of the screen. I'm owning a business but I'm handling mechanics, design and assembly (I'm engineer). You can read some other posts of mine and you will understand easy that's the case.
Optical stuff is another story and I have two opticians that can help designing Telecentrics for a special FL. It's a Zemax thing that doesn't take too much time. After this, the optics are manufactured in an optical factory, where they have tons of calibers for all sort of radii. They are not my usual collaborators, just some acquaintances. I made there a lot of things (prisms, wedges, beamsplitters, lenses) because the quality is high...I can not say here for who they are producing usually, but reading this you might understand.
My Herschel is made using a prism made there, my beamsplitter is made there (for the double pass h-alpha), the Telecentric is made there...and so on.
Hopefully this clarifies some things for you and others.
I wish you the best of luck in finding adequate solutions for your needs
!@colinsk
you said this : Since I am only a visual observer I don't need a really flat field but I also don't want to introduce new abberations with the telecentric.
May I ask, what other aberrations can be induced in the final image since Telecentric is designed in optical software for best results possible on a predefined diameter and you are using it in a narrowband monochromatic environment? As mentioned above, I'm not specialist in optics so more knowledge over this, is always welcomed.
Thank You!
Catalin
