Where's the astronomy?

I know, too much electronics mumbo-jumbo.  Where's the astronomy?  Well, it's been pretty cloudy and this weekend it's raining, so no observing.  I've been doing more research though, and I'm leaning more towards the Apertura AD10 now.  I'm going to go to OPT this weekend to take a look at scopes again.  They don't carry the Apertura line, but they do carry the Orion scopes.  At least I'll be able to judge the physical size and hopefully they will let me pick up the tube of the 10" so I can check what the weight feels like for moving it around.

I've also been playing around with processing of the images I've take so far using the barn door tracker.  Nothing worth posting yet, but I can see that I have at least one decent image of Andromeda from my 55mm lens which might be presentable with some work. I'll post it when I have something.

First Arduino based stepper control for my barn door tracker

I've put together my first prototype for stepper motor control of my barn door tracker.  I used an Arduino Nano V3 compatible and one of the little 5V 28BYJ-48 stepper motors from eBay.  A pair of the stepper motors with driver boards cost about $5.  For the motor's gear I used a 16 tooth 32 pitch pinion gear for an RC truck.  It has the correct 5mm bore.

Yes, I know the circuit looks like a bit of a rat's nest at the moment, but I included several features that I think will be useful.  Once I have it all worked out and put on a PCB, it should (hopefully) be much neater.  I've got a pot for adjusting the speed, a start stop button, a switch to set speed to normal or high, a button to reverse direction, and a magnetic reed switch which I plan to use as an emergency stop when it reaches the end of the threaded rod if I forget to stop it in time.  There are also a couple of LEDs to indicate running and high speed.  I'm thinking of using high speed and reversing to try to do drift alignment.

I'm using a breadboard power supply to provide the 5V for the motor and a 9V 1.5A wall wart power supply to power it all.

For rough alignment I hold a green laser pointer against the wood strip parallel to the hinge line, but I'd like be able to align it better, so hopefully drift alignment will work.

I had a clear night a few days ago and tried out the setup.  The controls worked well and the concept proved good, but I don't think this is the right motor for the setup either.  Whether I took a 5 second exposure or 1 minute, the stars trailed the same amount.  I think there is either too much vibration or the low resolution of the motor doesn't give smooth enough steps.  It could also be slop in the gear train.  This motor only gives 32 steps per revolution, with the gearing of 64:16, that gives 128 steps per minute to turn the big gear one revolution.  If I put my finger on top of the gear, I can feel the vibration as it takes steps.  What do you expect for something so cheap?

I've ordered a SM-42BYG011-25 stepper and EasyDriver from SparkFun. This motor uses 200 steps per revolution and the EasyDriver can do 8 step microstepping (each step is broken into 8 microsteps).  That means this combination can give 1600 microsteps per revolution of the motor.  With the 4:1 gear ratio, that will give me 6400 steps per revolution of the main gear.  Should be much smoother.  Hopefully that will arrive in the next couple of days.

Arduino starter kit

A little while ago I picked up an Arduino Uno starter kit from CuteDigi, just to play with.

This kit includes an authentic Uno R3 board (not a clone or compatible), small breadboard, jumper wires, USB cable, and a a bunch of components for playing around with circuits.  Along with tutorials on the Arduino website, Adafruit, and others, learning to program the Arduino is pretty straightforward.

I plan to use an Arduino to control a stepper motor to run my barn door tracker.

Which scope!?!?!?!?!

I mentioned before that my son has a PowerSeeker 70AZ telescope.  It's ok as a very basic beginner scope, but I'd like something better.  The mount and tripod are pretty shaky and I don't like the chromatic aberration (CA).  I also find the viewing position uncomfortable, needing to lean down pretty low when viewing something high in the sky.  So I'm trying to decide on which scope I'd like to get.  There are several in the $500 price range I'm looking at, including the Celestron Omni XLT 150 reflector, Omnit XLT 127 SCT, NexStar 4SE, 10" dobsonian, and a few others.  I think, after reviewing the pros and cons I've read online, and seeing them at OPT, I've narrowed it down to the Omni XLT 150 or a 10" dob.  I've tried binoculars, but I don't find them comfortable, and having only a single magnification is limiting in my opinion.

The only one I've had an opportunity to use is a 10" dob at a local star party held by the San Diego Astronomy Association.  It was an Orion 10" dob and the views were beautiful!  Before trying it, I didn't know if I'd like a dob since the scope I used to have (a C4.5) was on an equatorial mount and offered convenient tracking.  A few minutes of use of the dob at the star party changed my mind though.  It was very easy to manually track.

If I go with the 10" dob, I'll be going with the Apertura AD10 instead, as it comes with some extra features for about $100 less than the Orion.  The 10" dob definitely is the winner as far as optical performance over the XLT 150.  It gathers much more light and will show many more details in my light polluted back yard.

There are a couple issues I'm still debating before deciding which to get.

1. Portability - the XLT 150 wins over the AD10.  The XLT 150 can break down and be stored and carried in a bag, which would be great when going camping with the family or scouts.  A 10" dob has a big tube (about 12-14" diameter and 48.5" long) as well as a large base that doesn't break down.  Moving from the house to the backyard shouldn't be an issue for either one though, which is where I'll be using it the most.
2. Tracking for visual observing and astrophotography - the XLT 150 is on an equatorial mount, so after adding a polar alignment scope and drive motors, tracking could be quite good.  I could even add a DIY autoguider in the future.  The AD10, being a dob, is basically a manual alt-az mount.  There are some options though.  I could build an equatorial platform.  Who knows, sometime in the future I could even build a split ring mount for it.

Despite these issues, I'm leaning toward the AD10.  The much larger aperture is a huge selling point and the tracking issue can be overcome.  

I need to drop by OPT and another star party or two before I decide.  Who knows, something else might come up.

Astrophotography gear

I've read a bunch of sites on the web about astrophotography.  I don't understand much about processing the images yet, that will take time to play around with.  I don't have any images worth sharing yet, but the basic process is to take several exposures, call lights or subs.  Using free software called DeepSkyStacker you can combine all of the subs, along with dark, bias, and flat frames (all described on their site) to get a much more detailed image and remove a lot of the noise.  There are several packages to process the image after that.  A lot of people use Photoshop, but I'm cheap, so I'm going to try to use GIMP.  I found an experimental release of version 2.9, which allows processing 16 bit images at http://www.partha.com/.  

While I do that, I'm also trying to develop a good way to take the pictures.

The camera I'm using is a Canon T3i.

Using the 18-55mm kit lens that came with it gives some nice wide views.  At 55mm it can fit the "W" of Cassiopeia, and then some.  To get a bit tighter, I picked up a used Bushnell 135mm f2.8 lens on eBay for about $7 (yes $7).

This lens uses a M42 threaded mount, so I also picked up an inexpensive mount adapter.  The nice thing about a fixed prime lens is that the aperture opens much larger than most zoom lenses.  The f2.8 is much wider than the f5.6 that my kit lens can do at 55mm.  This lets in much more light.  I haven't had much chance to use this lens yet, but in some experiments it appear the lower half of Orion would fit in the frame.

I may get another longer lens later on, but for now, this will be my setup.

I'm not interested in doing star trail photos, so a tracking mount of some sort is needed.  Searching the net, I learned about barn door trackers, which are simple DIY mounts.  So I built one matching Gary Seronik's design.  Here's what mine looks like.

 An inexpensive ball head from eBay is used to mount the camera.  I found the same 4rpm DC motor, but I wouldn't recommend it, as I'll mention below.  I built the voltage control circuit described on Gary's page.  For gears, I found appropriate ones at ServoCity.  It all runs off a 9V battery.

Why don't I recommend this motor?  I found that it has a lot of play in the shaft and I can't seem to get a steady tracking rate.  From one exposure to the next some with have no trails, some short trails, and some longer trails.  It also eats up a 9V battery really fast.

So my next thought was to try a stepper motor and control it via an Arduino microcontroller.  More on that when I get it working.

Starting My Astronomy Blog

I intend to document my journey back into amateur astronomy.  I don't know if anyone else will find anything of use in my ramblings, but who knows.

Several years ago I owned a Celestron C4.5 reflector on an equatorial mount and greatly enjoyed using it in my parent's back yard.  It was a great little scope, but over time other interests took over and eventually I decided to sell it.  Fast forward a few years and my son, 8 at the time, became a science fanatic.  His main interest at the time was astronomy.  His interest has sparked my own interest as well.  He received a Celestron PowerSeeker 70AZ refractor as a gift and we have had a lot of fun using it together.

We also picked up a DSLR a while ago, so I have begun playing around with astrophotography.  I can't spend a lot on equipment for a tracking mount, so I'm looking into a DIY solution.  More to come on that.