From: "milton_aupperle" <milton@outcastsoft.com>

Date: January 21, 2010 11:49:36 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: New Images

Hi Alan;

Thanks for the Astro-Physics link and the compliment. M46 is one of my favorites too, but is really tough to image here, as it only get 21° above the horizon. The previous night I started to shoot M46 at 1:30 am under much better skies (some of the best I've seen in months), but just as I finished the luma images it clouded over and I didn't get the RGB.

A Quick search on the Astro-Physics found several possible explanations, including the Type 1 Astrodon filters I bought or possibly the clear glass cover plate over my CCD. I have had real suspicions about the CCD glass cover plate since the red response I get from the camera ss very weak. I have to use 2x the exposure time of the Red channel to balance the G and B colors out with a G2 star, and that is at odds with what the CCD spectral response should be.

PS:

Turbulence was very low last night, so I got the C8 collimated very well (it was off considerably) using Aldebaran and the 2.5x barlow. Then I shot about 16 gigs of moon video at 5 meter focal lengths just 2 hours after sunset. It was close to the sides of this building and directly over a populated area, so heat turbulence was bad and I got nothing good enough to warrant showing.

Mars was just rising and was 10° above the horizon when I had a quick look at it with the Grasshopper mono camera. Even at that low elevation, I could make out the polar cap using the Luma filter, so I was waiting another 2 hours until it got above 35° to start imaging. But an ice fog rolled in at 9 pm and by 9:30 you couldn't see 10 meters, let alone Mars.

TTYL..

Milton Aupperle

--- In Astro_IIDC@yahoogroups.com, Alan Friedman <alan@...> wrote:

HI Milton,

Thanks for sharing your new images. I especially like your capture of M46 - have always enjoyed this object visually with the ghostly planetary nebula haunting the field. 

There was a thread in the Astro-Physics Yahoo group about a problem with reflection around bright stars - I think the cause was being associated with certain RGB filter brands, but I didn't follow the discussion very closely... might be worth a look. I seem to recollect that some deep sky folks have been switching to Baader's RGB filter set for this reason.

best wishes,

Alan

On Jan 20, 2010, at 4:03 PM, milton_aupperle wrote:

Hi Folks;

I've posted some first draft DSO images that I captured on the Nights of January 16 and 18, the only clear nights I've had in nearly a month. It was a balmy -4 to -8°C those nights, so I only needed to wear a heavy sweater when outside and didn't need to use heating pads to keep the scope or laptop from freezing up. I used the C8 @ 1150 mm, LRGB Astrodon filters, a Hutech IDAS LPR, the Grasshopper PGR camera (cooled to -20°) and a monochrome PGR Camera with the Celestron OAG for guiding. I shot Lumas at 1x1 and then binned all the RGB shots 2x2 when capturing. That reduces my RGB exposure times by a factor of 4 times, so instead of needing 24 minutes per Red image, I can shoot 6 minutes. I can go after 3 or 4 targets in a single night now as it's dark here at 6:30 pm and doesn't start getting light until 6:00 am.

Turbulence was low (+/-3 arc seconds) on Jan 16 and moderate (+/-8 arc seconds) on Jan 18.

I've discovered that I have a really bad reflections happening when I have bright (i.e. Mag 4 stars) stars in the FOV for long (15 minute) exposures, as shown in the Running Man "NGC1973" or the IC417 images. It's most pronounced with the Green filter, but happens for all LRGB images. I'm not sure what is causing it, but it looks like the light is bouncing off one or more of the glass surfaces multiple times and then becomes out of focus, which is why we have the collimation rings. It could be off the glass plate over the CCD on the camera, the LRGB filter, the LPR or maybe even the Focal reducer.

In any case here are the images..

Auriga reflection nebula (need a lot more exposure time under less light polluted skies):

http://groups.yahoo.com/group/Astro_IIDC/files/DSO/IC417_LRGB_20100116.jpg 

Running Man nebula in Orion (haloed stars):

http://groups.yahoo.com/group/Astro_IIDC/files/DSO/NGC1973_LRGB_20100116.jpg 

Messier 38 open cluster in Auriga:

http://groups.yahoo.com/group/Astro_IIDC/files/DSO/M38_20100118.jpg 

IC 434 the Horse Head nebula in Orion

http://groups.yahoo.com/group/Astro_IIDC/files/DSO/HorseHead_20100118.jpg

M46 an Open Cluster and NGC 2438 a ring planetary nebula that only gets 20° above the horizon up here:

http://groups.yahoo.com/group/Astro_IIDC/files/DSO/M46_20100119.jpg 

TTYL..

Milton Aupperle