Mirrors: Skywatcher 20" vs Hubble Optics 20"

[davidem27]

Good morning y'all!

I decided to make the big step: upgrade my 16 to a 20 inches, self made.

I'm trying to set a stable-but-portable scope and I was looking for a lightweight mirror in worldwide markets.

My eyes dropped onto these two mirrors: weights are really lighter than other Pyrex standard mirrors.


The next questions are

- What is their real optical quality?
- How much the coating is good in these two type of glasses?
- Is it durable through the years?
- Has the parabolized surface made without rugosity, considering they are industrial made mirrors?

I think these questions could be only answered by owners that had (hardly) tested and measured these optics alongside with precise benchmarks, and also have posted mirrors for many years.

I would be glad to discuss with you about mentioned issues.


Davide

[Ivan Maly]

The Skywatcher quality control on these is "1/4 wave". See my last blog post for some pretty fine detail in M81 that I caught with mine on a cold but very stable night. I've only looked through an 18" Hubble at low-medium power; not much of a test. Good luck with your project.

[davidem27]

Thanks for fast replying Ivan!
Your HII observations about M81 are very interesting.

What is your favourite magnification, using Stargate dobson?
Do you observe at 250-300x?
How does the mirror works at these powers?

[Ivan Maly]

I have just got the scope for Christmas and made one short dark sky run to use the rare winter clearing. 250x looked perfectly fine. I plan to use higher magnifications often and report on it in the coming months.

[davidem27]

My ears are fully opened :D

Thanks again Ivan.