Stargazers Lounge Uses Cookies
Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.
-
Recently Browsing 0 members
No registered users viewing this page.
-
Similar Content
-
By jamesj01
Hi everyone - juts purchased my first telescope and am asking for advice on what is best to be seen through this telescope as a starter - have already seen the moon and some distant stars and am comfortable with using all of the eye pieces included. What would anyone recommend?
-
By JMH
Good morning and thank you in advance for your advice and patience! I am looking to purchase my first telescope, budget around £200. I am overwhelmed by the choice, but am looking for certain things:
Quite lightweight / easily portable
Smartphone adapter for taking iPhone pictures
Specifically interested in looking at planets, ISS, galaxies as well as the moon
Must be on a tripod and not table-top
I would be grateful for your expertise. I am in the UK (Suffolk) if that makes a difference! I look forward to learning A LOT here
-
By Michele Scotti
Hi everybody - I'm humbled that some of you are following the thread on the 800mm telescope. I thought it was worth starting a sub-topic specifically related to the mirror making.
So as the works on the mount got halted by the lockdown we had some time to virtually meet-up and discuss the optics for this project.
The onset was pretty straightforward with an 'if we are doing this we are making the mirror'. And that sorts out the make vs buy, I suppose.
As of now, the only two things decided so far are the diameter -at 800mm- and the f/3.3 - of course we can accommodate some variance.
Some aspects of the making are pretty unchartered territories for our club so I'd like to seek some good advice from anybody in terms of direct experience or rather point us at some resources/threads.
Back-ground: to make it short, our senior member had three 500mm f/5 done years ago. He did of course faster optics up to f/3 among many other mirrors - I actually never asked him how many, uh! He has always worked with full tool and has no experience with slumped glass. Btw we do have some experience in slumping glass but -weirdly enough- not in machining.
During our initial discussions we boiled the scenarios down to 3:
float glass, 35/40mm thickness considering 15mm of sagitta. This is a thermal challenge with its big outward mass, it's going to make the machining more of a challenge and the stabilization time longer float glass, 25mm (which seems more of a commercially available), slumped. Trading the thermal challenge with the slumping borosilicate, 25mm, slumped. Tbh this is just a better version of the previous point at a cost that is not prohibitive
What are the sources of glass in Europe for thickness over the bog standard 25mm?
Disclaimer: this is surely an ambitious endeavor and by no means we are underestimating that. Not only the bigger diameter is a step-up; the fast optics is a challenge too.
To start with we have some questions about slumped glass. It looks like an attractive, modern approach to mirrors that exceed a given diameter. I think I saw already some threads specifically about the slumping itself - that's golden.
However it's the grinding/finishing/parabolizing that is puzzling us. Are there specific techniques or is it the same as the flat back glass?
Also, how do you support the mirror? Would a support that replicates the telescope mirror cage be appropriate - a 27-point in our case? Or is it a matter to build a concave support that holds the back of the mirror? How accurate/solid should that support be?
Any experience out there??
I reckon that's enough as a start - thanks everybody in advance for your contribution.
Stay safe! Michele
-
By avodcap7
I have a celesctron nexstar 8SE OTA, to which I attach my focal reducer (0.63x by celestron), the a T-Adapter-SC, a t-ring and then my dslr. Does the T-Adapter affect the performance or use of the focal reducer?
Emilis
-
By Corpze
So, I have been testing three different kind of lasers, each one is supposed to be the "best" in each category or what you want to call it, the hotech and HG is almost the same, but whit the difference in how you lock it down.
The Catseye is very different in how it works.
I made a Youtube video of my thoughts
https://youtu.be/ERF33hNVieQ
What do you think? which one do you use?
Regards, Daniel
-