Image of the day

Captured by
Douglas Rollain

LBN 576 - The Garlic Nebula

About Astromart

My Account

New to Astromart?

Register an account...

Need Help?

Posts Made By: Alan French

April 28, 2006 11:56 PM Forum: Deep Sky Observing

Orbital Elements

Posted By Alan French
I've been using the elements here.....

http://neo.jpl.nasa.gov/ca/

They have everything you need - including TP in Julian.

Clear skies, Alan

April 29, 2006 08:01 PM Forum: Solar System Observing

April New Moon Spotting Contest

Posted By Alan French
I spotted the Moon with the unaided eye at 8:15 EDT on Friday.

Clear skies, Alan

May 8, 2006 12:47 PM Forum: Equipment Talk

Rifle scopes as finders

Posted By Alan French
Bob Polcyn said:

Hi all --

There are a lot of riflescopes out there with low to high price tags. Some have illuminated reticles. Are they practical for astro use?

Bob Polcyn

Bob,

You can certainly use a rifle scope. I left the finder to one of our scopes home by mistake once when we went up to camp. I adapted a rifle scope for use as a finder rather than drive three hours home and three hours back. The field and aperture was a bit limited, but the large amount of eye relief and correct image was nice.

Clear skies, Alan

May 9, 2006 08:35 PM Forum: Refractors

Help on a first Refractor

Posted By Alan French
Louis Griffin said:

Hi - I was hoping for some help regarding my first refractor, I have a 20" Starspitter Dob but I am looking for a quicker setup and some very nice wide field views as well as Lunar/Planetary work - I have been thinking of 3 scopes - the Williams Optics 80 ZSFD and the Orion ED 80 & 100 is there alot of difference between them?

If you want to use it for lunar and planetary work, then you would be better off with the larger aperture. I think small refractors really shine in about the 90 to 100mm range, where they have short enough focal lengths for wide fields, and enough aperture to do a respectable job on the Moon and planets.

Clear skies, Alan

May 15, 2006 04:38 PM Forum: Solar System Observing

Moon Filter??

Posted By Alan French
The Moon can certainly seem bright, but I have never been a fan of Moon filters. The Moon has very bright whites and extremely black shadows, and any filter(neutral denity or variable polarizing) I have tried seems to muddy the whites and turn the blacks grayish.

If you devote time to observing the Moon without a filter, you will get used to the brightness and it will cease being such an issue.

I highly recommend getting a copy of Harold Hill's "A Portfolio of Lunar Drawings."

Clear skies, Alan

May 16, 2006 03:03 PM Forum: Telescope Making

Perplexing Refractor

Posted By Alan French
I am puzzled by your comment "the view is as it should be {backwards and reversed}." How are you viewing through it before you put an eyepiece in?

Also, how did you measure the focal length? I'd suggest stopping the lens down to an inch or two and measuring the focal length by imaging the Sun or Moon on a white surface.

Clear skies, Alan

May 17, 2006 03:09 AM Forum: Astro-Physics

Do,and can,Photons reverse?

Posted By Alan French
jon roewer said:

When he gets time, perhaps Rolando will comment.

-------------
http://www.rochester.edu/news/show.php?id=2544

jon

Photons get odder and odder. Folks with an interest in such things should read - if they haven't - "QED: The Strange Theory of Light and Matter," by Richard P. Feynman.

Clear skies, Alan

May 18, 2006 06:44 PM Forum: Equipment Talk

Carry-on vs checking on airplane

Posted By Alan French
Craig Smith said:

I have some back problems and need to sell my LX200 and get something lighter. I've thought it would be nice to have something I could take on plane trips anyway, so at this point I'm leaning towards the small carry-on-able refractors or maybe a mak. But I'm wondering if it would be worth getting something a little bigger and checking it. Reasons I can think of for sticking with a carry-on are:

1) Damage. But I would think there would be relatively little risk with refractors, and even mirror scopes are shipped regularly through means that may treat them worse than airlines.

2) Theft. More important if the scope is not replaceable. Not sure what airline reimbursement limits are.

Is checking it really that bad of an idea?

We have taken an AP Traveler to WSP eight times now. The OTA has always gone as carry-on. The head for the 400 mount has gone in a large King Pelican case. This was an early mount with slow motions. On one trip the mount arrived at WSP damaged. The case looked fine, and I could only assume it had been dropped a rather large distance and the momentum of the mount bent some knobs.

Fortunately, we are now able to send things down with some friends. I would not trust the airlines with anything I valued. I've seen them out there loading and unloading stuff - and they are often far from careful.

Clear skies, Alan

May 20, 2006 07:47 PM Forum: Telescope Making

Optics question

Posted By Alan French
Based on "Mirror Support: 3 or 9 Points?" Sky & Telescope, Sep 94, pp. 84-87.....

A 14.5" mirror 1.6 inches thick would sag 1/59 wave.
A 16" mirror 1.6 inches thick would sag 1/40 wave.

I don't think I'd worry about the difference.

Clear skies, Alan

May 21, 2006 11:56 PM Forum: Equipment Talk

What's your cheapest cheesiest scope?

Posted By Alan French
I have a little Gilbert reflector downstairs. A friend at work gave it to me when he was cleaning out the house.

Clear skies, Alan

Funding Member

Sponsors


View all sponsors

Search