making my first fast mirror

See sub forums to discuss "Do it yourself" projects.
Post Reply
User avatar
BABOafrica Kenya
Local Group Ambassador
Articles: 0
Offline
Posts: 2757
Joined: Tue May 07, 2019 2:41 pm
4
Location: Kenya
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

making my first fast mirror

#1

Post by BABOafrica »


I've made several mirrors over the years: 1 x 8" / 3 x 10" / 2 x 12.5". They were all slow mirrors (f/6+).

I was visiting my family in Washington DC over Thanksgiving and one of my sisters asked me what I do for a hobby. After listening for a few minutes, she decided to check ebay on her phone and bought me an 8" full-thickness Pyrex blank that was on auction that day.

I do enjoy mirror-making...

The blank has not arrived in the mail yet. So I'm trying to decide what to do. I'm leaning towards doing a fast mirror this time around, something in the range of an f/3 to f/4 mirror.

I like the idea of having a short tube, mainly because my storage space is more limited than it used to be and my ability to carry stuff around is also more limited. Gone are the days when I enjoyed wheeling out my 17.5" Dob. Also I want something I can mount on my Atlas EQ-G.

My one doubt is that the coma on an f/3 8in parabolic will be a serious issue. I have never observed or done any AP with that kind of OTA.

Any comments on that would be welcome.

BABO
"In lumine tuo videbimus lumen."

Scopes: Stellarvue SV80 Raptor Carbon Fiber ED Doublet / Celestron SCT C8
Williams Optics 66mm APO / DIY 8" f/4 Newtonian astrograph / Nikon 180mm f/2.8
Mounts: Orion Atlas EQ-G / Celestron AVX / DIY mini-equatorial
Cameras: QHY163m / Fujifilm X-A1 (modded) / Fuji X-A2 (not modded) / Orion StarShoot Auto Guider
Filters: ZWO 7nm NB set / ZWO LRGB set / ZWO Dual Band / Astronomics UHC
User avatar
Jones
Mars Ambassador
Articles: 0
Offline
Posts: 179
Joined: Tue Jun 23, 2020 12:21 am
3
Location: Arizona
Status:
Offline

Re: making my first fast mirror

#2

Post by Jones »


How's your wallet? You will need a coma corrector.
Arizona- where the sky's are not cloudy all night.

Triple lensed fracs are so yummy when looking at planets.
User avatar
BABOafrica Kenya
Local Group Ambassador
Articles: 0
Offline
Posts: 2757
Joined: Tue May 07, 2019 2:41 pm
4
Location: Kenya
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Re: making my first fast mirror

#3

Post by BABOafrica »


Yeah...
"In lumine tuo videbimus lumen."

Scopes: Stellarvue SV80 Raptor Carbon Fiber ED Doublet / Celestron SCT C8
Williams Optics 66mm APO / DIY 8" f/4 Newtonian astrograph / Nikon 180mm f/2.8
Mounts: Orion Atlas EQ-G / Celestron AVX / DIY mini-equatorial
Cameras: QHY163m / Fujifilm X-A1 (modded) / Fuji X-A2 (not modded) / Orion StarShoot Auto Guider
Filters: ZWO 7nm NB set / ZWO LRGB set / ZWO Dual Band / Astronomics UHC
User avatar
Graeme1858 Great Britain
Co-Administrator
Co-Administrator
Articles: 1
Offline
Posts: 7217
Joined: Mon Jun 24, 2019 7:16 pm
4
Location: North Kent, UK
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

I Broke The Forum.

Re: making my first fast mirror

#4

Post by Graeme1858 »


BABOafrica wrote: Wed Dec 09, 2020 12:19 pm The blank has not arrived in the mail yet. So I'm trying to decide what to do. I'm leaning towards doing a fast mirror this time around, something in the range of an f/3 to f/4 mirror.

Sounds like an interesting project Babo!

What do you use to grind the mirror?

Looking forward to watching this thread grow.

Regards

Graeme
______________________________________________
Celestron 9.25 f10 SCT, f6.3FR, CGX mount.
ASI1600MM Pro, ASI294MC Pro, ASI224MC
ZWO EFW, ZWO OAG, ASI220MM Mini.
APM 11x70 ED APO Binoculars.

https://www.averywayobservatory.co.uk/
User avatar
BABOafrica Kenya
Local Group Ambassador
Articles: 0
Offline
Posts: 2757
Joined: Tue May 07, 2019 2:41 pm
4
Location: Kenya
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Re: making my first fast mirror

#5

Post by BABOafrica »


Graeme1858 wrote: Sun Dec 13, 2020 9:21 am
What do you use to grind the mirror?

Graeme
I'm planning on a rather conventional procedure. I'll start with #80 SiC grit for rough grinding and eventually finish up with AlO for the fine grinding. Then I will polish with CeO.

BABO
"In lumine tuo videbimus lumen."

Scopes: Stellarvue SV80 Raptor Carbon Fiber ED Doublet / Celestron SCT C8
Williams Optics 66mm APO / DIY 8" f/4 Newtonian astrograph / Nikon 180mm f/2.8
Mounts: Orion Atlas EQ-G / Celestron AVX / DIY mini-equatorial
Cameras: QHY163m / Fujifilm X-A1 (modded) / Fuji X-A2 (not modded) / Orion StarShoot Auto Guider
Filters: ZWO 7nm NB set / ZWO LRGB set / ZWO Dual Band / Astronomics UHC
User avatar
BABOafrica Kenya
Local Group Ambassador
Articles: 0
Offline
Posts: 2757
Joined: Tue May 07, 2019 2:41 pm
4
Location: Kenya
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Re: making my first fast mirror

#6

Post by BABOafrica »


I got the mirror and started working on it. Here are the pictures...

The (wet) mirror at the beginning (it arrived in the mail already partially ground):

BABO 8in Pyrex 01 - beginning r.grind.jpg


The back of the mirror, showing that it's real PYREX (BTW, the back has a raised edge for some reason...):

BABO 8in Pyrex 02 - back.jpg

The thickness of the mirror blank:

BABO 8in Pyrex 03 - edge.jpg

After finishing the rough grinding (using a sequence of #80 - #120 - #220 SiC grits):

BABO 8in Pyrex 04 - #220 r.grind.jpg


I'm well into the fine grinding now. I should start polishing one of these days...

BABO
"In lumine tuo videbimus lumen."

Scopes: Stellarvue SV80 Raptor Carbon Fiber ED Doublet / Celestron SCT C8
Williams Optics 66mm APO / DIY 8" f/4 Newtonian astrograph / Nikon 180mm f/2.8
Mounts: Orion Atlas EQ-G / Celestron AVX / DIY mini-equatorial
Cameras: QHY163m / Fujifilm X-A1 (modded) / Fuji X-A2 (not modded) / Orion StarShoot Auto Guider
Filters: ZWO 7nm NB set / ZWO LRGB set / ZWO Dual Band / Astronomics UHC
Post Reply

Create an account or sign in to join the discussion

You need to be a member in order to post a reply

Create an account

Not a member? register to join our community
Members can start their own topics & subscribe to topics
It’s free and only takes a minute

Register

Sign in

Return to “The DIY corner”