This is a simple article about astrometry and imaging. Astrometry involves precise measurements of positions and movements of stars and other celestial bodies. Astrophotographers can take an image of the sky without the known celestial coordinates, and using various sites, or data can determine the position and coordinates of the objects in the image.
Many astronomical telescope control programs use astrometry data to position a telescope in a precise location. Some will even model the mount to aid in more precise position when skewing the telescope. (Ktars/Ekos does both of these functions.)
Below is an example of uploading an image to an astrometry site (nova.astrometry.net/upload) to determine the precise location.
Select an image to upload:
After upload, the image will be submitted and processed. Once completed you will see the screen below (if successful):
Next, press the “Go to results page” , it will bring you to imaging solutions page as shown below:
If you select the “view in WorldWide Telescope”, you will be transfered to the World Wide Telescope and there you can explore your image in detail.
I made an Arduino Focuser for my William Optics ZS 73 (see my original Orion Astrograph version). The focuser is basically the same as the Orion Astrograph focuser except for the bracket and layout. The bracket is the same except it does not have the tabs in the Orion version. Also, it attaches to the dove tail. I removed the fine focusing knob and attached another belt sprocket.
I started out taking astronomical images back in the mid 1990’s using CCD imaging. This was when CCD cameras were very expensive and not very practical for the amateur astronomers. I found a book about making your own CCD camera, The Cookbook Camera by Richard Berry. I built several of these camera CB-245 and modified the cooling system. The cookbook CCD resolution was 378×242 pixels (my current camera has 3097×2080).
Andromeda Galaxy – M31 (Old Cookbook Camera Image)
By the mid 2000’s they became obsolete. I then purchased a Meade DSI pro camera and continued imaging.
Andromeda Galaxy – M31 (Meade DSI Pro CCD)
Fast forward to the present, I got back into the hobby and found that the prices have come down quite a bit. I purchased a ZWO asi 178MMC camera which is cooled and the price point was which I could afford. I’ve been re-learning and purchasing new equipment.
I have finally got a number of “good” images that is a vast improvement from my old Cookbook days and Meade DSI Pro cameras. It’s been some learning curves with the equipment and software. I will be writing some useful articles about using Linux with Indi Library Drivers and my setup. I will cover the lessons that I have learned during this process.
I wanted to make a focuser for my Orion Astrograph 8 inch reflector using an existing Indi Library driver for Kstars/Ekos. It had to be simple and I wanted to avoid writing a new driver for Indi Library. During my research, I found some documentation for JMI Smart Focuser that explains the command set. This seemed like an easy solution using an Arduino and a stepper motor. I then reviewed the Indi Library source code to find out what calls the JMI Smart Focuser driver is making to the focuser. Seeing that the Smart Focuser driver was making minimal commands to the JMI Focouser, I decided to create my own simple focuser using the Arduino Nano.
Arduino Focuser
First Version
My first version that I built used a separate Focuser controller which plugged into the remote stepper motor assembly. This used an LED display and had a hand controller and powered by a separate 12V power supply. I found that I never really utilized the display focus buttons, so I simplified the focuser design.
First VersionFirst Version
Second Version (Simplified Version)
The minimal Arduino Focuser uses a Nano Arduino and is powered by the USB connection. There are no other external connections. It plugs directly into my Indi server’s powered hub. (I have also powered it from my ZWO asi178mmc camera using its built-in USB hub).
Protoboard (for mounting the Arduio Nano and Stepper controller)
Aluminum GT2 Timing Belt Pulley, 16 Teeth Bore 5mm with 6mm
MXL Belt 76MXL/B95MXL 6mm Width 2.032mm Pitch
RMP .063 3003 H14 Aluminum Sheet, 12″ x 12″
All above parts are available online via Amazon.com when this article was published.
Below is the layout of the simplified focuser that includes the electronic parts layout and wiring:
Focuser II – Completed ModuleFocuser II – Backside
Bracket Assembly
Below shows the Mounting Bracket for the focuser board and stepper motor. Note, you will need to add the mounting holes of the stepper assembly and oblong these holes for adjustment purposes. The MXL belt is perfect for the Orion Astrograph focuser and will slide on and off the fine adjustment knob. Here is a pdf file of the assembly: Focuser.pdf
You should be able to print out the file and make a direct template. All units are in millimeters.
Schematic
I have included both schematics for the first versions and the simplified version.
First Version Schematic DiagramSimplified Focuser Version Schematic Diagram
Arduino Code
The Arduino code (Version 0.60) is provided in a zip file. It has been complied using Arduino IDE 1.8.5. I have included the stepper accelerator library in the zip file that I used for this version. For more information regarding the stepper accelerator library, follow this link: Accel Stepper Library
The code supports both versions and by default the displays are commented out for the simplified version. Here is the zip file: Arduino Focuser V0.6 zip
I have been active in Amateur Radio on and off for over 43 years. Things have changed quite a bit since I started. I remember the days before the Internet where I would listen for hours to other ham radio operators talking about their projects, describing various circuits and enjoying other ham’s conversations.
I was always learning something and getting involved with interesting conversations. Today it’s different. You don’t have as much on the technical side. Some conversations make me cringe, either too political or religious, or just plain bad behavior. There are always weekend contest which interfere with my enjoyment of the hobby. I am not very interested in participating in contests and have found that contesters are getting more rude through the years with no concern other than making a contest contact.
The digital modes seem like the are now driven by total automation. I used to enjoy the low powered modes that kept the bandwidth small. It seems like FT8 has taken over most of the digital modes now. In my opinion, FT8 is a joke with people running higher and higher power to make contacts; where is the fun in that?
I still enjoy a CW conversation now and then, but when your noise level is at S9 due to all the lousy electronics in your neighborhood, and the band conditions are terrible, it’s a bit turn off.
So it’s time to shift hobbies and if anyone knows me, they know I have plenty. I’ll be sharing some astronomy projects as well as my learning process regarding astro imaging. I’ve done CCD imaging back in the mid 90’s with a Cookbook Camera. But, the current technology is amazing.
It’s that time of year where I like to take out the telescope. Bugs are dying off, less humidity, and nights are longer. I have a pedestal mount that I attached during these months. I hopefully will build a simple enclosure to help expedite the setup time. The scope is remotely controlled and I used a CCD imager as my eyes. Even though this scope is up in age, it works well and guides well. I’ll upload some of my astronomy projects as time permits.
The Heathkit SB-200 amplifier has been around for years and many are still in use.
I rebuilt my Heathkit SB-200 that I obtain from e-bay. This one was in bad shape but the price was right. It was dropped, bad tubes, and definitely been used. I slowly rebuilt the amp and got it fully functional. Initially I rebuilt the power supply using Harbach Electronics PM-200 Replacement Power Supply Module. Refer to their website.
I came across a web site, http://www.xs4all.nl/~pa0fri/Linairs/SB200/sb200eng.htm, which PA0FRI explains in detail on how to modify the sb200. I went ahead and modified my SB-200 according to his website and followed most of his recommendations. The following items are what I wanted to accomplish with these modifications:
Tube Protection. Fuse the high voltage to reduce catastrophic failures.
Soft Start to limit the primary in-rush of current and slow the rise of anode voltage. This protects the filaments and rectifier diodes and permits the use of a lower current primary fuse.
Stability
Change amplifier key to support modern radios.
Reduced filament voltage. On my SB-200, I had almost 7 Volts on the Filaments. I ended up using a loop of 18 gauge Teflon wire to drop the voltage until the filament voltage was in an acceptable range.
ALC Adjustments is now easily adjusted. This is nice when I use it with my Drake transmitter which I can easily overdrive. The amplifier is very stable and is well protected.
Faster QSK Operation. I wanted a faster transmit/receive transition, by updating the input and output relays did the trick.
SB-200 Modified, Schematic Diagram
These modifications are based upon PA0FRI’s modifications. I give him all the credit. I am impressed with the stability of the amp and have not had any issues. Please refer to his website: http://www.xs4all.nl/~pa0fri/Linairs/SB200/sb200eng.htm,
The modified SB-200 schematic diagram is shown below. This uses a “Key-All” circuit board for keying the amplifier. This board may still be available from Jackson Press. I also incorporated a “soft-start” from Harbach Electronics.
Here is the meter switch wafer detail. This needs to be modified per the schematic above.
Input/antenna relay uses a reed relay for the input and a VAC relay for the output side. I had to had a 24V power supply for these relays since the original used 117V.
