Posts Made By: Kwang Lee

So, my aluminum tube arrived and there's some kind
of grease-like coating on the interior.

Can anyone suggest a solvent to remove it? And prepare
for the primer?

Thanks,

Kwang

Hello all,

While putting toghether a 8" Newt with a mirror coated
by Clausing (sp?), I noticed that the light from the ceiling revealed some 'pinholes' which are visible from
the bottom of the mirror. Out of curiousity, I shined a flashlight from the bottom of the mirror and about thirty to forty pinholes of light were visible on the coated side.

Is this common in a newly coated mirror? Or is it a sign of some kind of early deterioration of the coating? It was coated about 3 months ago via their "Diamond Brite" coating.

I appreciate any insights on this.

Kwang

Hi-

I'm planning a scope built around a 12.5" mirror.

Does anyone have any idea who makes the lightest
mirror cell for a 12.5 mirror?

For reference, I have a 8" cell from University
and an 8" from Novak. I can tell just by handling
both of them that the Novak is lighter.

Thanks in advance.

Kwang

So, it happened. My 1.83" diag slipped out
of its UniversityOptics holder and crashed
onto my 8" mirror. The diag broke in two pieces.

There's a 1 cm impact crater
near the edge of the mirror, and about six or seven
scratches varying in size from 1 cm to 4 cm long.
All the scratches are thin.

Do I ask the mirror maker to refigure/regrind the mirror?

I'm building my own da*n diag holder so I won't be
able to test the performance until the weekend with
a new diag.

Any advice would be appreciated.

Kwang

Hi all,

has anyone worked with conical blanks to make
either a traditional newt or a cassegrain primary?

If you're grinding/figuring by hand, how do you secure the
blank to the working surface?

Kwang

I picked up an 8" F/5 mirror that was part of a Celestron
newt that was damaged. The mirror is just fine, but it
has some markings on it that I was trying to decipher.
Do these numbers mean anything to any mirror makers out there?

P3
+.22
6/11
R

P.F.
629 jm

T (or 1?) 8
3 m (or w?) "

Refig

They're all written on the back. I was impressed by the thin mirror design.
Is this the same kind as the conical design used for SCT's ?

Another interesting feature is that diameter measures 8 and
1/4" and only about 7 15/16" is actually coated.

OK. This is not definitive by a long shot, but because a recent sale of my MX716 fell through, coupled by the fact that I went crazy and bought a ST7ME, I ended up with both CCD cams.

I realized I had a unique opportunity to test both rigs, so I setup a quick test with my Short Tube 80 aimed at my bookcase. I acquired images and darks through AstroArt 2.0. I let the camera sit idle for 10 minutes before taking any exposures. I chose 1x1 binning for ST7 and Hi-Res 'Fast' mode for the MX. So, after goofin around, I decided on 60 sec darks with 60 sec exposures. I let AA do the dark processing and I exported all images as jpg's. In PS, I didn't do any processing except video de-interlacing (odd fields) as the MX716 image had noticeable banding. (Oh yeah, I resized the final image size.)

General stuff: I knew that the ST7ME was noisier, but I didn't realize HOW much noisier. I think it affects the final image as it seemed to me that the smooth area above Soyinka's book is 'splotchier' in the ST7ME image. Also, the MX716 seems to capture the slight shadow above the book with more finesse. Though I could bring it out in PS by playing with Curves.

When looking at the raw images, I had the impression that the MX716 was picking up more detail and more light from
the scene.

But looking at the dark made by the MX716, it's clear there's some kind of 'amp glow' from the left side. And in a self-guide scenario, the MX716 will require much longer expsoures with Star2000, which will introduce more
gradient issues. Dark subtracting will take care of this.

There's something really nice about having the guide chip and imaging chip in the same camera. Though I didn't realize how large the ST7 head was.

Anyways, now I'm not sure which camera I should keep. What strikes me about this comparison is that there's a big difference between imaging a bookcase and imaging a faint galaxy. So, a big grain (or chunk?) of salt is required for my comparison.

Regards,

Kwang Lee

I was wondering what kind of motions one uses with a mirror polishing machine and I came upon the following webpage:

lerch.no-ip.com/atm/Projects/Polisher/page_01.htm

There are actually a few MPEG files that show the machine in action. (at the bottom of the page)

My question is this: How does the movement of the tool change as you move through your grits? And into final polishing?

Thanks for any insights...

Kwang

about pic of the diagonal mirror in Ad #301168.

Looks like John at Mirrorkits.com is unavailable for a few months.

Does anyone know who else can generate a curve on a mirror blank for a modest fee?

Thanks,

Kwang