Ad Astra Observatory

Art Morton wrote:
>
> On Jun 9, 2008, at 9:13 AM, Jimbo S. Harris wrote:

>
>> Art Morton wrote:
>>> I also have to find out how to handle that darn bright star.
>> I hate to suggest this, but maybe adding some diffraction spikes
>> would throw enough light out of the star and into the spikes that it
>> would help your blooming problem? Just a thought. Diffraction spikes
>> affect “point” sources more than extended sources, so I’d expect the

>> nebula would still show up well.
>
> Very funny.
I’m not kidding. The diffraction spikes throw light out of the Airy disc
and into the spikes. So that means that light is getting thrown out of
the central pixels of the star and out into pixels nearby. It might be
enough to let you image for a little longer before you get a bloom.

I go back to my photo of the same object, shot with a refractor:

http://www.jimbo.net/astro/wp-content/uploads/2006/08/20060818_NGC6960_10×2min.jpg

Yes, I have a anti-blooming gate camera. But the light is spread out
over lots more area than the center of the star, so it might help your
blooming problem on this object.
Just a thought.

>>> Most of the time, I auto guide, but if there are not a lot of
>>> stars in the field, I have NOT guided and gotten good results up to

>>> 600 sec with a good alignment. There is not drift and you have
>>> seen the 0.00 corrections. I am impressed with the thought and the
>>> math that went into this too.
>>>
>> I need to get this part figured out. I think my polar alignment is off.
> I think so too, but just a little. The pointing model does not
> correct anything with the polar alignment. It will however allow you

> to find things and put them in the center of the eye piece when the
> polar alignment is not real good.
Yep, that seems to be my experience. I wish there was a way to run the
mount in “manual” mode. All the new doodads and geegaws are confusing me. (:
>> I need to do my “CCD alignment” routine again. One problem that I’m

>> having is that I have no earthly idea how to get the Gemini to go at
>> 2x sidereal. I’ve sent James Bielaga an email asking him how to get
>> that done. Without getting the drive to turn off in one direction,
>> the alignment routine will not be as accurate.
> Yea, I have not been able to do that. Unplugging the cable makes the
> Gemini cranky.

James says that there should be some setting in the “slew” speeds that
will get this done. I’m just not sure what the speed numbers are
referring to (ie, if I’m looking for 2x, do I set it to 1, 2, 100,
200?). He’s getting back to me on that.
>> my polar alignment scope still says that Polaris is in the wrong

>> spot. I’m not sure what to make of that.
> I do not use my polar scope for perfect alignment, just to get some
> where close. Once I am close I use the software tools to get the
> alignment I need to image unguided. My polar scope does not have a
> very precise fit. There is plenty of slop, so I know that I can only
> get close with it, but not right on.

Have you ever looked through the polar scope *after* you’ve done a good
drift alignment, to see how far off it is?
> The only other thing I can think of is to make sure that the Gemini
> Base is level.
The bubbles say it’s level. It’s possible that the bubbles are misaligned.

J