Posts Made By: Steve House

Greetings all,

I just acquired a 17mm Televue Plossl eyepiece as a part of a larger deal, and am wondering about it. The current Televue line doesn't include the 17mm. Can anyone tell me the history of this eyepiece? How does it compare to the current line that includes the 15mm and the 20mm? Why was it discontinued? Many thanks!

-Steve House, St. Charles, MO

Greetings all,

Didn't TeleVue use to make a 1.25" Paracorr, or am I dreaming it?

-Steve House

Hi All,
I'm wondering if some of you might try your hand at processing this recent raw stacked image of Saturn. This is from my second round, and I think I'm sneakin' up on it. I would love to know if you are able to get more detail than I was from this image.

Thanks!

Steve

Greetings All,

I would like some advice. The desire for "more light" has taken over, and I want to build a 24" Dob. I ground and polished two 20.5" pyrex mirrors about 12 years ago, but never had the proficiency to bring them to the state of near-perfection needed to be completely satisfying. (You know- the "hill-in-the-hole-in-the-hill" problem, with a TDE to boot.)

The other situation is that I am not independently wealthy and am always looking for the financial short-cut.

My question: In your opinion, would I be financially better off to secure good glass and grind and polish a 24" mirror, and then send it off to someone for figuring, OR just pay for the mirror outright and be done with it?

I guess part of this question concerns the cost difference between figuring an existing mirror and a new mirror.

Your comments are most welcome.

-Steve House, St. Charles, MO

Friends, I'm new to understanding the Losmandy mount system. I'm hoping to find out how the mount dovetail system may be adapted for use with non-commercial homebuilt telescopes. Which dovetail would you use, for example, with a 10" newtonian? What rings fit that dovetail?

I would love to see examples of non-standard telescopes used with this system. Thanks!

Greetings, Can anyone tell me if the Coulter 13.1" mirrors made in the '80s were ever 3/4" plate glass? I recently purchased one on (fill in gap) and it wasn't the Pyrex I was expecting. Your help is much appreciated.

Thanks!

Hi all,

I'm finishing a 10" f/8 and before I send this mirror for recoating, I want to make sure it doesn't need any refiguring work.

Basically, I bought a "pig in a poke" off Ebay four years ago. It appears to be an old Cave 10", judging by the type of full-thickness molded pyrex and the mirror mount it came with. (Paid about $125 for both as I recall.) The coating was bad, of course.

Last night the images showed a very small amount of astigmatism on star images. The moons of Jupiter were tiny crosses. I'm using a 1.3"ma Protostar secondary (new)with their curved spider, in their "Blacklite" tubing (great stuff!).

Not having a laser collimator, I used a simple cheshire crosshair collimator, and everything lines up.

So, what are the possible sources of astigmatism in this system? I'm really hoping to prove the mirror good, but want the brutal truth.

Tonight I will try again, and rotate the mirror in its cell to see if the "crosses" rotate. (Not easy with this Univ. Optics mirror mount.)

Many thanks!
Steve House, St. Charles, MO

Good People,

While breaking in my new mirror machine, I overshot the sag on a standard 6" pyrex blank. Actually, I was going for f/4.25 and reached f/2.7 much more quickly than I expected. (I wasn't paying the attention I should have been.)

Anyway, instead of TOT to bring it back for a short-focus Newt., I'm considering a Gregorian scope with a Nasmyth focus. I've never built one before.

I would appreciate the wisdom of this group.

1. How difficult is it to figure a small concave secondary? Are there any special considerations?

2. Are there any issues regarding stray light in a Nasmyth focus, especially when using a concave secondary that doesn't mask incoming light as well as a convex secondary (being farther away)?

3. If the figure of the primary is a standard parabola, would the Gregorian secondary also be a parabola? What design would use a spherical secondary? Seems that would be easiest since it is relatively small.

4. It would seem fairly straight-forward. A curved spider for the secondary and a simple single-vane stalk for the tertiary flat. Any thoughts?

5. Would you have any online sources to recommend for design and parameters? I have Texereau, but my intuitive/subjective mind has a little trouble completely understanding him. Maybe something is lost in the translation. 8O

I hope I'm not just playing with a paper telescope here, but that would of course be my first step. I'm hoping some of you have attempted this before.

Many thanks!
Steve House

Hi all,
Its been a while since I've needed to buy a fine secondary. I need advice as to what vendors sell above average secondarys. In particular, I will be wanting to buy a 2.3-2.5" ma secondary that is at least 1/15th wave, and with superior coatings. I'd like to get a 96% or better reflectivity, and a SiO2 overcoat. I'm not too particular about the substrate. Pyrex would do, I think.

Your advice would be welcomed! Thanks.
Steve House

Greetings to all,
I just bought this old EQ mount. I'm wondering if anyone can identify what company produced this, and when. Your help is appreciated!

Steve