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RICHARD COFER

VdB 141 Ghost Nebula

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Posts Made By: Roland Christen

October 29, 2004 04:32 PM Forum: CCD Imaging and Processing/Solar System

Saturn with ST10XE

Posted By Roland Christen
Thanks all for your kind comments.

Planet mode on the ST10 is where you limit the exposure to a small number of pixels around the planet itself. This allows rapid download so you can do one exposure every second or so.

Roland Christen

October 29, 2004 07:17 PM Forum: Equipment Talk

5" or 6" APO question

Posted By Roland Christen
Depends on what you consider a 5" and 6" size. If you go from a 130mm to a 150mm, then the difference is 15% in resolution and 33% in brightness. If you go from a 125mm to a 160mm, then the difference is 28% resolution and 64% difference in brightness.

Roland Christen

November 12, 2004 11:11 PM Forum: Astro-Physics

Help me with the paint scheme

Posted By Roland Christen
Idea #2

November 13, 2004 04:24 PM Forum: CCD Imaging and Processing/Solar System

AO7 Users... A question

Posted By Roland Christen
It won't do anything about bad seeing if the seeing is such that the stars are bloaty. It will improve star diameters when the seeing is wandering quickly which cannot be followed by your guider. It will also help if your mount is poor quality and not steady in a wind, or the drive gear is erratic.

Best results are achieved when the AO7 is set up to make 10 corrections or more per second. For that to work, you will need to find a bright guide star that can register above the noise with .1 second or shorter exposures. This is not always easy, especially in star poor regions of the sky, or if your scope is less than 10" aperture.

The AO7 works best in situations where you have a very large scope mounted on a marginal mounting where normal guiding produces large errors due to vibration or wind or poor tracking.

Roland Christen

November 15, 2004 05:49 PM Forum: CCD Imaging and Processing/Solar System

M31 From New Observatory

Posted By Roland Christen
Why the diffraction spikes? They are very distracting to me. Otherwise great shot.

Roland Christen

November 17, 2004 10:20 PM Forum: Refractors

Re: chosing the right refractor

Posted By Roland Christen
Attached image shows 3 different 5 inch achromat lenses with their inherent color error. Only the 5" F16 is diffraction limited for red, green and blue.

All simulations and calculations were done with ATMOS lens design software (about 30 seconds per lens).

Roland Christen

November 18, 2004 12:15 AM Forum: Equipment Talk

That "Sidewalk Test" thingy again, test your skill

Posted By Roland Christen
That #7 is a real bowser!

Roland Christen

November 19, 2004 02:52 PM Forum: CCD Imaging and Processing/Solar System

Somebody on drift polar alignment!!

Posted By Roland Christen
>>My problem is that, when I do this and center a star, this seems to move slowly but noticeably to the east (always at 225X): >>

You do not say what kind of telescope you have, but it is well known among us imagers that SCTs, especially in the larger sizes will have enough differential flexure in their optical tubes so as to produce a slow trailing, even when the mount is tracking perfectly and is perfectly polar aligned.

The evidence that this was happening was discovered by people who had small light weight guiding refractors mounted side by side with the heavier SCT tube assemblies and discovered that a star would stay perfectly still on the crosshairs of the smaller scope, while it moved in the large one.

The problem with Cassegrains is that they don't have the mechanical rigidity of the optical compnents to stay perfectly aligned with their mountings at different orientations in the sky.

Roland Christen

November 20, 2004 06:40 PM Forum: Refractors

Is B58-53 problem glass?

Posted By Roland Christen
>Can anyone tell me what the problem is with this approach? Is Corning B58-53 a problem? Price, availiability, etc. I can post the other files if anyone is interested.>

I have made a number correctors for large achromats, the last one for a 10" F15 Zeiss. The glass does work in this application. It is a relatively soft glass, similar to fluorite, and will break easily if heated or cooled quickly. You may have extreme trouble getting any in good quality levels or even at all, since Corning France is essentially out of business and melts only the most common crowns now. I have a few pieces left and they all show striations and non-homogeneity. There are other ways to accomplish this function without using this troubling glass.

Roland Christen

November 27, 2004 03:20 PM Forum: Astro-Physics

AP "Vaporware" Complaint

Posted By Roland Christen
Sorry that I have to do that. The 600 mount is extremely difficult for us to machine and assemble, and we were basically losing money on every one we made. It is not very easy to adjust in the field if something should go out of wack.

The mount is more than 15 years old now. It definitely has run its course, and there are better ways to make mounts today. We want to take advantage of new thinking and new technology, and to beef up the weak spots in our products.

Thanks for letting me explain.

Rolando

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