From: Milton Aupperle <milton@outcastsoft.com>

Date: January 27, 2010 10:03:16 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Final DSO images

Hi Alberto and Alan;

Thanks for the kind words.

Alberto, The biggest change is that I moved pretty much out of Calgary, and am on the south edge of the city. I'm also down on the ground when I'm imaging, so it's no more shooting from a balcony where if large vehicles or construction was shifting about, you could see the images shift in response. There is nothing but bare fields to the east or south of me right now, so I I don't get affected by the local heat rising from commercial or residential building which really affects turbulence. And it's about 1.5 to 2 magnitudes darker than where I was living last year, which really helps for the faint DSO targets.

But I still have to use a Light Pollution Reduction (LPR) filter here if I go over about 10 minute exposures. On clear nights the sky background here is 1,000 to 1,500 ADU per minute of exposure for the Luma with the Grasshopper Camera. So if I do a 20 minute exposures, the sky background has a value of  20,000 to 30,000 out of 65,535 in the image. That basically hides any faint subtle DSO objects in the background.

If I use the Hutech IDAS LPR filter it's about 400 to 700 ADU per minute of exposures for the Luma and for a 20 minute exposures the sky background has a value of  8,000 to 14,000 out of 65,535 in the image. So that helps a lot in reducing the sky glow without obliterating the objects. The sky background here is still as bright as if you have a perpetually first quarter moon perched in the sky though.

The other thing I did was to replace the cheap original bearing for the RA axis and worm gear on my HEQ5 mount last fall, and then re-tune the gear mesh. The mount turns a lot smoother and is far less likely to bind now. This has basically eliminated a 3 to 5 arc second spike I was getting at about 5 second increments (i.e 5, 10, 15 or 20 seconds it might happen), that I could not guide out.

TTYL..

Milton Aupperle

On 27-Jan-10, at 1:52 AM, albe albo wrote:

Uhuh....

very nice work Milton.

I don't know M46 and its problems (i never attempted it) but i know the Horsehead and the Running Man and they are rendered very well, soft, clean and well guided.

It seems that, generally speaking, the year 2009 marked a big step ahead in your DSO  or am I wrong?

In addition to your personal skilling, did you change some technical equipment?

If i watch M1 for example, the change is really huge and I think that on January 2009 you were enough skilled too! 

Cheers

TTYL

Alberto