Any thoughts on a Borg 90FL?

[Elp]

Just poking around the slumbering upgrade tree. It won't be for a long while yet.

Anyone got experience with the above, the 90mm will be an aperture increase to my current 60mm whilst still being light enough to use on my azgti. I can also use my existing 2 inch reducer with it to make it F3.6 and 325mm focal length.

[Adam J]

1 hour ago, Elp said:

Just poking around the slumbering upgrade tree. It won't be for a long while yet.

Anyone got experience with the above, the 90mm will be an aperture increase to my current 60mm whilst still being light enough to use on my azgti. I can also use my existing 2 inch reducer with it to make it F3.6 and 325mm focal length.

As your using it at F3.6 i would say that you should expect an amount of CA when imaging with the 90FL. For good correction you need to run it at native focal length.

Adam

[Elp]

I already use said reducer at F3.8, the main issue is trying to reduce elongated stars as it's a heavy reducer (apex 0.65x), I don't think it will ever be perfect, I could always use a less harsh or just a 2 inch field flattener at native FL. I wanted to know more about the scope as it's fluorite glass, and it's lightweight, and for a 90mm it's still very compact.

[Adam J]

2 minutes ago, Elp said:

I already use said reducer at F3.8, the main issue is trying to reduce elongated stars as it's a heavy reducer (apex 0.65x), I don't think it will ever be perfect, I could always use a less harsh or just a 2 inch field flattener at native FL. I wanted to know more about the scope as it's fluorite glass, and it's lightweight, and for a 90mm it's still very compact.

Yes but with the 90FL it causes CA and with your current scope it will not.

Yes its about as light weight and compact a 90mm as you are going to find. But it would not be my choice as a imaging scope. Florite is better than FPL-53 for sure, but its still a doublet, so in the end its going to perform better than something a 80mm F6 doublet, but not massively better.

I wont say dont go for it, I am just saything that you cant expect perfrect correction from a 90mm doublet at F3.8 even a florite one.

Adam

 

[Mr Spock]

If you want a 90mm have a look at this thread. The posted images say it all.

 

[Elp]

Actually seems quite decent.

[Adam J]

On 29/12/2022 at 08:28, Mr Spock said:

If you want a 90mm have a look at this thread. The posted images say it all.

 

Dont think that meets OPs requirement of being light weight though? The AZGTI would definetly die with that on it.

Adam

Edited December 30, 2022 by Adam J

[Oldfort]

There's a detailed review from Roger Vine here:

http://www.scopeviews.co.uk/Borg90FL.htm

[Elp]

43 minutes ago, Oldfort said:

There's a detailed review from Roger Vine here:

http://www.scopeviews.co.uk/Borg90FL.htm

Thanks, I've seen it. Just about the only review I've found which is odd.