Author: mojo

I set up the AP180 last night and was able to capture comet NEOWISE as it passed through Ursa Major.

This video is fifty frames covering about 27 minutes, from 9:11 p.m. to 9:38 p.m. on July 19, 2020.
Each frame is a 10-second exposure.

We had several great clear nights in Monrovia. I had a night where everything clicked. If I hadn’t napped a bit, I might have gotten two or three more Messier objects.

I think now I know the most difficult part of urban astrophotography — at least with the camera I use: Finding suitable guide stars!

I can position quickly and easily to center my target object in the frame, and have no guide stars in the guide camera suitable for guiding. When the available guide stars are all fainter than the sky glow, PHD2 will lock onto any random signal it thinks is a star, then spend the entire exposure hunting for it.

I’ve learned to do the hunting myself before a shot. I can pan in a spiral around the object and watch for a suitably bright guide star to show up. As a result, many of my objects in these two nights of imaging are not quite framed the way I’d hoped.

Now my planning is going to be tougher. I may not be able to fill in many of the missing targets I didn’t catch this month until almost next year.

All of these images are 30 minutes of data, using six 5-minute subexposures. The telescope is an f/9 180mm Astro-Physics Starfire AP180EDT, mounted on an AP1100GTO mount. The camera is an SBIG ST-4000XCM one-shot color CCD.

Click on any of the pictures to link to the full resolution version, mostly twice the size (and half the sharpness).

From the evening of May 24:

My best image of that night was this one of M5. It could just be the excellent signal-to-noise ratio, but it’s possible that a fog layer was reducing the sky glow from Los Angeles.

The next night, May 25, I had more trouble finding guide stars.

I shot M61 because it was next in my list, but Jane recalled seeing that it had an active supernova. It’s there in the image. I’ll let you discover which star is the supernova.

Last night (Saturday, May 23, 2020) was a beautiful dark clear night in Monrovia. Tonight is forecast to be even better and warmer. I can’t resist! When will I sleep?

By the end of evening twilight, I was aligned, focused, calibrated, synced, and ready to image.

I’ve been cherry picking Messier objects that were near their highest altitude for the evening. There’s a trio of galaxies near each other in Leo, M95, M96, and M105. I thought I’d start with these.

This is where I discovered the real weakness of urban astrophotography. For M95 and M96, I could not find a guide star anywhere nearby. I took a couple of images only to have the guiding software (PHD2) hunting around and guiding on what it thought were stars. The results were all squiggly lines. So I mostly gave up on those two for tonight.

I had better luck with M105, and got a nice image of it with two nearby NGC objects.

But wait, there’s an interesting detail. You might not see it if you’re in a bright room, or with a bright background. You might click on the image for the full resolution version.

Do you see that odd circle in the background, left center?

That’s nothing mystical, it’s just caused by a mote of dust on the imaging glass of my camera. The mote is “out of focus” so it appears as a shaded circle. I correct for those by taking a series of flat images at the end of the night. I point the telescope at the zenith and put a light panel on top of the scope. I calibrate the timing so it generates a flat grey image around 50% of the camera’s dynamic range. (I’ll take a picture of that process tonight to show you.)

Here’s the flat from last night’s imaging run, stretched in contrast so the differences show a little more:

I didn’t shoot flats for years because I couldn’t figure out how to get a neutral grey image target in the field, and calibrate it for a 50% image. Now that’s handled by my light panel and software that calculates the right image duration.

You can see the dark circle on the flat that matches up with the circle in the background of the M105 image. That leaves a mystery — why didn’t the flat correct for the dust mote, like it usually does?

As a test, I recalibrated the image without the flat, and the circle was still there, but it didn’t have the “3D” look to it from the calibrated image.

You can see the same problem in two other images from last night:

Look, there it is again — that dust mote circle in the left center of the image.

And yet again, there’s the circle just to the left of M109.

Now here’s the last image from last night. Under the circumstances, I thought this was a beautiful shot of M63 the “Sunflower” galaxy.

Wait, where did the dust circle go? It’s not there! The flat worked perfectly for my M63 image.

That mystery dust circle was a puzzle as I was processing the images in the wee hours of Sunday. When I saw this last one, I understood what happened. Can you guess?

I always shoot my flats at the end of the evening. It’s that one dreaded task I have to do before packing up the gear in the wee hours. It has to be done while it’s still dark.

The flat worked perfectly for my last image. It could only mean one thing:

The dust mote that made the circle shifted position during all the telescope movements during the evening.

During the early evening exposures, it was in a slightly different spot on the glass cover than it was during the last image. You can see the effect — the flat compensation shows extra bright on one side, and extra dark on the other. That’s what gives it the “3D” raised, or depressed, effect.

The previous post mentions how I started trying out photographing Messier objects from my home in Monrovia, using my Astro-Physics Traveler 105mm f/6 refractor. The results were encouraging enough that I had to bring out the giant AP180EDT and see how that would go.

This is not a one-person telescope. It really takes two to lift it into the mount rings, and dismount it after the session. I’m heavily dependent on Jane for the setup and (most importantly) the takedown. It turns out she’s a full supporter of the project, and offered to help me take down even when it would mean waking her at 2:30 or 3:00 a.m. That’s true love!

While we’ve had the telescope for about twenty years, the original mount has been replaced with an AP1100GTO. That should make it an astrophotography demon. Without the ability to “goto” an object, this project would be all but impossible in the city sky glow.

My experience with the equipment consists of about two evenings testing, and one evening of actual observing, so there was a lot of tinkering, calibrating, and adjusting. I was fixing and tuning the hardware, and learning the software. I spent hours doing fine polar alignments, recording “bad pixel” maps for the guider, diagnosing guiding errors, and such.

That said, I still managed to capture what I consider stunning images for such a bright location. I’ve been logging two more Messier objects each evening, and with several good clear moonless nights in a row, I haven’t been able to resist.

I’ll just put all the comments in the captions. If you click on any of the images it will link to the highest resolution version, with every wart visible. 🙂

Tech details:

• Telescope 180mm f/9 refractor
• Mount AP 1100GTO
• Camera SBIG ST-4000XCM CCD one-shot color (Bayer matrix)

All of the images here were made by collecting 30 minutes of light, as six 5-minute exposures. The images were processed with CCDStack2.

Normally I wouldn’t even have considered trying this project. I’m known for hauling my telescopes to a dark sky site in the desert to do deep sky astronomy — visual or photographic.

But here we all are, staying home for the duration.

I have a spot about 50 yards from my front door. It’s a bridge over Sawpit Wash, partially paved, partially gravel. It has really good horizons, and no serious outdoor lighting nearby. When Jane and I first moved in we thought it might be our home astronomy site. We’ve done a little planet observing there. She famously counted meteors from there.

I thought maybe I could at least image a few bright open clusters, maybe a bright galaxy here and there.

I started with the Traveler, a 105mm f/6 refractor, and looked for targets that would be high overhead, into the darkest part of the sky. Leo was high, and the trio of galaxies including M65 and M66 looked promising. The results were encouraging.

The results were so promising, I thought I’d try my favorite globular cluster, M3.

M3 and I have history. It was one of the first deep sky objects I attempted to observe visually from home in Campbell, CA, deep in the San Jose light dome. I was observing from my street corner almost directly under a street light, with a Celestron 8-inch SCT. I spent about two hours hunting, and finally found a barely visible fuzzball in the eyepiece. I was ecstatic!

Now here it is from the Los Angeles light dome with a good astrophotography camera.

I had great fun with the Traveler over the next few clear nights. I think it’ll be a fun challenge to see if I can photograph all of the Messier objects from Sawpit Wash. I’ve started picking them off two or three in an evening.

Here’s my capture of a favorite pair of galaxies in Ursa major, lovely spiral M81 and turbulent M82.

If I could grab all the Messiers two at a time, this would be easier. Here’s M108 and M97 the owl. In this one you can see the effects of the sky glow gradient from city lights:

The city lights affect everything about this astrophotography. What’s really surprising is how effective the photos can be, even so.

After several evenings with the 4-inch telescope, I was really itching to spend some quality time with our AP180EDT refractor. That’ll be the next blog post.

This is the first new blog post from me in four years, and long overdue.

Why blog now?

I enjoy writing and reporting about stuff in my life: astronomy, travel, bridge, wine, photography, network systems.

And Facebook is Dead To Me.

Since my last post, Jane and I have both retired, I opened and closed a weekly bridge club, we cruised half the globe on Seabourn and Crystal (teaching and directing bridge games along the way), purchased a Tesla Model S and drove it to the bridge nationals in Memphis and Las Vegas, and acquired a new telescope mount.

Now I’m in the preparatory stages of opening a new full-time bridge club in Pasadena.

I’ll be working again soon, and working hard. I think I’m going to love it, but with that sense that I need to take advantage of this slow time to do things I won’t get to do as often.

I’ll be building a new website (Drupal 8) for the Pasadena Bridge Club soon. I have bridgemojo.com for posting bridge feature articles, and I’ll plan to continue that.

Our poor WordPress sites have gotten very little love. I’m sure Jane would appreciate a facelift as much as I would. At the very least, I should move them to a new server with a current version of PHP. (I see I really need to add SSL certificates, too.)

I need to build a new mail server and develop the habits of keeping it patched and current. The old one is like a pair of comfy shoes that feels so comfortable even while I know the soles are starting to get holes and they need to be thrown out.

The Pasadena Bridge Club is going to test all of my skills to build and maintain a comfortable, attractive, high-tech (without looking it), full-time bridge club. I should be documenting the process. (How do I support multiple computer screens in different rooms? Working on that.)

During our travels, we did “research” visiting bridge clubs large and small scattered around the world: Spain, Oxford, London, New York, and all around Southern California. I should write trip reports.

I’m going to start with an astronomy observing report. It was my first all-night excursion in about a year, taken while Jane is enjoying traveling in Europe with her sister. Optimistic that we’d be able to do some mid-week observing this year, we signed up for two observing pads at GMARS, the observing site of the Riverside Astronomical Society.

I had a great shakedown night, dusting off the cobwebs of a year’s disuse (and all of the associated software upgrades). I’ll post photos, an observing report, and an update on the new tools I adopted for doing astrophotography in upcoming posts.

Saving that for later … right now I have a bridge game to play in.

Thanks for lending an ear …

— Mojo