February 20, 2011

New Scope!

A few weeks ago I saw advertised locally a Discovery Telescopes 15" f/5 dobsonian. I have always been a bit sad not to see here in Houston the kind of used market that exists in the northeast US or in California. Each time a good-sized dob has come up here, it has been out of my price range (too fancy a scope, or too many accessories). But good things come to those who wait. This time it was just the scope, and the price was doable! When I saw the ad, I was sitting at the table in the kitchen running an imaging session in the backyard. I almost did not think. I just fired off a reply: "How can I pass this up? Is it still available?" Then, lest that one wasn't clear enough, I sent another: "The truth is, I will gladly take the scope off your hands. I can pick it up tomorrow or Saturday." I heard back the next morning, then drove the Suburban in to work instead of my small car.

Wow! This scope is big! It's very nicely thought out. The movements are very smooth, and the box seems sturdy and holds the scope well. The handles and wheels are very convenient. The focuser is nice. The Telrad is aimed aright. When I found that the Telrad batteries had juice left, I figured the scope had been cared for. In fact, it is in excellent condition, a testament to the care of its first and only other owner.

The optics appear first-rate! I was going to wheel it out right when I got home, but I found I couldn't get it out the back door! Whoops! (I had no idea the back door was too narrow. Now I have to figure some other way to get it into the backyard: around the side, probably, but I'll have to change the landscaping.) The next night I asked one of my daughters to carry the lighter end out.

Wow! First up was Luna, for the kids. Everyone came to have a look through Dad's new scope. The moon was high overhead, so everyone had to stand on something to reach the eyepiece. The moon was stunning. It's the view just as you approach the orb for a landing!

Next was M42. My daughter asked, "What's all that green glowing stuff?" I though I saw green and brown, and perhaps blue and pink, but I am biased by seeing too many published images. I will say, though, that I could see the E and F stars of the Trapezium with wide space between them and the other stars. It's a view I won't forget. I'm anxious to go back with a better eyepiece and more time and see what else I can tease out.

It was time to invite my neighbor (who keeps his lights off for me, thank you) to share the happiness, so I went next door and asked if he wanted to see. For the next half-hour we scanned through the real estate south of Orion. My favorite here is NGC 2362. It is awesome in the big scope! My first visual on this cluster was in 1994 through 80mm binoculars. It was so small, but very nice. Through the big scope, the cluster is stunning. The contrast between the central star and all her attendants is just enhanced. We also looked at M41, Sigma Orionis, and Rigel. Then family duties called, my neighbor helped me carry the scope in, and I wheeled it back to its storage area.

What a great first light! Figures it would cloud up after that and stay cloudy. The forecast today shows nothing but clouds for a week. It's ok, though. The memory will carry through. I look forward to many happy hours and years with this fine instrument.

February 13, 2011

IC 2162 (2-11-2011) (with a defect)

This nebula in the constellation Orion is one of those places in our galaxy where stars are forming from gas and dust clouds. Energy from those young stars is caught up by gas molecules in the clouds and then is released in the form of light. The gas around the stars literally glows. Much of the gas is hydrogen.

Light at a wavelength of 656.28 nm is emitted by a hydrogen atom when the electron in the atom moves from one energy level (the third) down one (to the second). This kind of radiation is called H-alpha. What we call an H-alpha filter is a piece of glass with coatings on it that let just a few wavelengths of light through. In daylight, the filter looks like a mirror. The swath of spectrum the H-alpha filter lets through is just a few nanometers wide and is centered on the 656.28nm wavelength, to the exclusion of all others. Nearly all light pollution is excluded, as a result. So the filter allows one to take fairly detailed images of objects deep in space even from suburban backyards. This image is 12x10' through the 10" newt, Baader MPCC, and 12nm Astronomik H-alpha filter, with the Atik 16.

After looking at this image for some time, and examining others' images of this object, I've concluded that the red on the right side of the image is spurious, a system artifact. The off-axis guider had loosened slightly, so that side of the camera was slightly further away from the primary mirror than the rest of the system. The effect was to introduce noise in that half of the image. I have noticed this also in another image I took later that session. I may be able to extract the noise through processing, but I haven't had time to work on it yet. I'm keeping the image up, either way, but please note that fact.

Horsehead Nebula (2-11-2011) & the 10" Newt

This image is the product of everything working right for an hour before the nebula ducked behind my neighbor's tree. This is 6x10' through the 10" Newt, with the Atik 16 through a Baader MPCC and Astronomik 12nm Ha [+NII] filter. The scope was autoguided off-axis.

The scope was working here the way I hope it will always work. The off-axis mirror is in front of the Ha filter but behind the Baader MPCC. The scope was collimated well. I think I have the scope balanced well on the mount. The FT focuser works like a charm. Everything was operated from inside the house using a long USB extender and wireless controls for the focuser.

February 12, 2011

Abell 21 or PK 205+14.1 or Sharpless 2-274 or the Medusa Nebula (2-7-2011)

This planetary nebula is about 1,500 light years away in the constellation Gemini. It's older than many planetaries and is colliding with interstellar matter. That gives it the dramatic look. My favorite image of this critter is Bob Franke's.

This image is 36x7' (4.2 hours) through an Astronomik 12nm Ha [+NII] filter with the Atik 16 and Orion 120mm + WO 0.8x II ff/fr = f/4 achromat.

Here's a colorized version.

February 6, 2011

Abell 31 or PK219+31.1, OIII Added

With OIII added, Abell 31 looks something like this. The OIII is very faint. Even with 18x7' (126 minutes) of exposure through the Atik 16, stacked, the OIII was very dim. I stretched the data as much as I could. The Atik 16 is not nearly as sensitive to OIII as it is to Ha. Here is a version with less brightness:

IC 443, the Jellyfish Nebula (2-4-2011)

This nebula is the remnant of a supernova. The nebula and the neutron star that is left after the supernova occurred (neutron star not pictured here) are located about 5,000 light years away in the constellation Gemini. The nebula is well-studied, and some facts about it are reported here with a nice image of the area. The Wikipedia entry for IC 443 is interesting and appears (as of this posting) to be well-documented. This image is 23x7' with the Atik 16.

Abell 13 or PK 204-8.1 (2-4-2011)

This interesting planetary nebula in Orion shines brightest by far in Ha [or NII]. This is 10x7' through an Astronomik Ha [+NII] filter.

February 5, 2011

Abell 33 or PK 238+34.1 (2-4-2011)

Abell 33 is a fine planetary nebula in the constellation Hydra. This is just 9x7' through an Astronomik 12nm OIII filter with the Atik 16 and 120mm achromat + WO 0.8x II ff/fr = astrograph.