APT + Stellarium Imaging Workflow

I came across an excellent video last week by Matt's Astrophotograpy. Matt's setup and choices for software are much like mine but his experience is vastly greater so I took a lot of notes.

I'm going to post those notes here and alter them as I do more imaging.

Software

Please consult each software's documentation to determine how it is to be configured.

Imaging Control: Astro Photography Tool

Once upon a time I used ImagesPlus camera control, then moved to BYEOS when I switched to a DSLR. My first impression of APT was that it was a mare's nest of capabilities and was too tangled to tame. I tried to like SGP, but the way it functioned seemed counter intuitive. I found NINA interesting but had to give it up when I found it didn't support my SBIG CCD or the QSI I was hoping to buy. Maybe by the time I buy that QSI it will be supported. So I sat down and started learning APT!

Be sure to install version 3.84 or later so you get ASTAP support (see next section).

Plate Solving:

I think you really only need to install ASTAP and its G17 star database. ASTAP seems superior for both near and blind solving compared to the old standards, PS2 and ASPS. And please don't tell me about AstroTortilla. Not to diminish the role it had in bringing plate solving to the masses, I always found it to be slow and unreliable.

Guiding: PHD2

Obviously.

Planetarium: Stellarium

This is a personal preference thing. I like Stellarium; it's pretty and it does what I need. This workflow will make use of Stellarium.

You may want to install version 20.1 instead of 20.2, as the latter requires you to manually connect to the mount.

Stellarium tip: The config.ini file lets you configure Stellarium's defaults. Here are two examples...

Turn off full screen mode, look in the [video] block, and set fullscreen = false

Turn off daytime sky brightness, look in the [landscape] block and set flag_atmosphere = false.

Slewing/Parking/PEC:

Slewing in RA is needed for Polemaster, which will want you to slew your mount several times. This can be done conveniently from within an ASCOM control panel or by using a hand control.

If you would rather slew entirely from within APT, do this:

Start with the mount at counterweight down (CWD) orientation and the RA axis pointed at Polaris. Connect APT to the mount. Copy the values of current RA & Dec to the GoTo fields. To do the requested rotation, usually just subtract one hour from the RA and click the GoTo button. (If the stars turn in the opposite sense of the PoleMaster display arrow, add instead of subtract.) Repeat for the second rotation.

To return to the start orientation, undo the RA changes in one step. DO NOT use the APT park button!

Setup & Initializing

Assemble

Start by assembling the components of your imaging system. This includes making all the data and power cable connections.

If your system is portable, this means rough-aligning your mount to north and balancing it for imaging.

When ready, power it all up: Laptop, Gemini II, imaging camera, dew heaters.

Make the data connection to your laptop. (In my case the data connection must be made after power-up because it could damage the SBIG camera if made too soon.)

Start APT and optional Camera Cooling

Steps marked with an asterisk are required even if not using the cooling aid.

*Launch APT
*APT/Camera / Connect
APT/Camera /Cooling Aid. Check settings and start.
*APT: Tools / ATP Settings / Main. Set image destination folder (optional)

Polar Align

(I use a PoleMaster for polar aligning. I agree with Matt 100%: PoleMaster is the way to do polar alignment.)

 

APT/Gear: Connect Scope (This launches an instance of the GeminiTelescope ASCOM driver.)

Attach PoleMaster to mount, connect USB
Launch PoleMaster software, and connect

Perform slews using one of these methods

ASCOM controller

1. Find the Gemini ASCOM driver icon in the Windows tray area. Right click and choose Show Hand Controller
2. Confirm Speed is "S" and that PEC is checked.
3. Use the hand control RA buttons to perform slews
4. When finished use the tray icon menu to close the hand controller. DO NOT minimize it!

APT

Use the add/subtract RA method described earlier

Disconnect and Remove PoleMaster

Sync

Launch Stellarium

Stellarium: If using version 20.2, manually connect the mount (use the telescope control plugin)

Stellarium: left click a suitable sync star, then use CTRL-1 to go to it

APT/Gear: Open Pointcraft

APT/Camera. Verify that exposure time is appropriate (I use 10s with my ccd and L filter)

APT: Shoot
APT/Pointcraft: "<< Scope Pos" to populate approx. position fields
APT/Pointcraft: Solve
APT/Pointcraft: (assuming solve is successful) Sync
Stellarium: Should now show true position of scope. Use CTRL-1 to center star in FOV
APT: Shoot new image to confirm star is now reasonably centered. If it is not, use Pointcraft Aim as described later and then Sync again

Focus

Please refer to APT documentation to learn how to best use the focus aids. I use a Bahtinov mask whenever possible.

APT/Gear/Filter Wheel/Go To Filter: Select filter to focus
APT/Camera/Bulb Seconds: Set appropriate exposure time

Attach Bahtinov mask
Shoot single images or use Live View. If Live View is used, possibly disable Live View Automation (APT:Tools/APT Settings/Main/Live View Automation) to prevent binning
APT/Tools/Bahtinov Aid: Make sure focal length, aperture, and pixel size are correct; turn on Cross mode

Drag Aid window so that focus star is at crosshairs

Recalc as needed if not in Live View mode
Adjust focus until satisfied with focus
Close Bahtinov aid
Remove Bahtinov mask!

Acquire

Obtain and Compose Target

Obtain a Target Object

    Find target in Stellarium, CTRL-1 to it
    APT Pointcraft:  <<Scope Pos
    APT Shoot image
    APT Pointcraft Solve
    APT Pointcraft Aim, click on image to refine center if desired
    APT Pointcraft GoTo++
    When completed you are good to go.

   
Go To Specified Coordinates

    APT Gear Enter coordinates into Center FOV boxes
    APT Pointcraft GoTo++
    When completed you are good to go.

Resume an Old Session

    Find target in Stellarium, CTRL-1 to it
    Open image from previous session
    APT Pointcraft Solve
    APT Pointcraft << Solved
    APT Pointcraft GoTo++
    When completed you are good to go.

Autoguiding

Launch PHD2
Toolbar Connect Icon or simply CTRL-C, connect guide camera and mount
Main Menu/Tools/auto-select star or simply ALT-S
Click SHIFT-toolbar Guide button to calibrate
Let PHD settle

APT/Gear/Guide to connect to PHD2 and configure optional dithering

Acquisition

APT/Camera Select Imaging Plan

APT/Camera Start

Shutdown

APT/Camera/Warming Aid: Warm the camera slowly (optional)

APT/Gear/SHIFT-Guide to disconnect from PHD2

PHD2/Toolbar/Stop button

PHD2/Toolbar/Connections disconnect all

Close PHD2

Find the Gemini ASCOM driver icon in the Windows tray area. Right click and choose Show Hand Controller

ASCOM Hand Control/Park (optional)

APT/Gear/Disconnect Scope

Tray ASCOM icon/Right click, Exit

When warming is complete, APT/Camera/Disconnect

close APT

close Stellarium

Turn off Laptop

Turn off Gemini II

Disconnect USB cables from any devices that may be harmed (Applies to my SBIG ST-8300M)

Disconnect all from power supply

The Lust for Power, Part 1

Okay, maybe not so much lust as desire.

For the last five years or so my dark sky imaging has relied on two deep cycle batteries. One of the batteries had been allowed to discharge to nearly dead but with regular recharging seems to have recovered, although there's no doubt it lost some of its life.

These are group 27 unsealed lead acid batteries that weigh about 55 pounds each. With that weight you might expect them to have good amp hour (Ah) ratings. What are their capacities in Ah? They're labeled with two RC values: 200 for a non-standard 23A drain rate, and 175 for the standard 25A rate. The higher drain rate translates to a capacity of 73Ah and as expected the slightly lower drain of 23A gives a capacity of 76.7Ah. My expected drain rate of 6.5 amps is much lower and should suggest a larger yet AH value. Another practice is to take the Ah to be half the RC; for my batteries this would be 87.5Ah.

The upshot of all that uncertainty--and battery capacity is notoriously difficult to quantify--is that I'll assume the batteries started their lives with an AH value around 80. What it is now I can't say, other than it's less.

Even that conclusion has to be questioned, for some of those amp hours are coming when the voltage is well below 12V. Will everything keep working at 11 volts? SBIG says my CCD will work even at 10V. Kendrick controllers basically turn off when the voltage drops below 11.6V. (They're quite adamant about this and have refused pleas to disable the low voltage cut-off.) The CGEM's ability to handle low voltage is questionable, though; there are reports that it will begin to fail when the voltage goes below 12V.  So even if my batteries are able to produce 80Ah, they're not all usable.

Time for some "ground truth." How have the batteries performed in the past? Probably their biggest single star party workout came at the 2014 Nebraska Star Party where I imaged for seven and one half hours at an hourly drain of about 6A (see below). This probably says more about the lack of clear sky time than it does about the batteries.

Hauling batteries like this on long road trips is a bit of work, and does present a small risk that the batteries could leak acid. So far I've never tipped them over, but an unpleasant accident almost seems inevitable. So it may be time to replace them, and what follows is my exploration of the options.

Power Requirements

Some dark sky star parties are three nights, others are four, and all of them that I attend are during the summer or early fall. A typical summer night is completely dark for only about five hours; by the equinox this stretches to nine hours. Rather than estimate a nightly power need, an hourly power consumption is probably more sensible to use. ADDED: I was able to actually measure some of the values, and those are added in [red].

• CGEM Mount: During fast slews it can require 1.5A [1.4A], but when tracking it's more like half of that. Let's assume a 0.75A [0.35A]demand while imaging.
• SBIG ST-8300M CCD Camera: The spec sheet says the camera draws 3A at 100% cooling. A more typical cooling load is 60% of this, so I'll assume a steady 2A draw.
• DSLR instead of CCD? probably more like half an amp. [With the display off, my Canon T2i, draws 0.13A while idle,  0.19A while imaging. The 12VDC-to-7.4VDC converter is 0.03A of those values.] 
• Laptop: My old Gateway's AC power adapters says it runs at a maximum output of 3.4A @ 19V, so at 12V that's more like 5.4A. This agrees with my 12DC adapter's spec sticker that says it permits up to 5.6A. That's the load when it's running and charging the battery. A more realistic load is closer to half that, so I'll say 3A to be on the high side and include losses in the 12VDC to 19VDC adapter. [While charging it draws 5.6A, and 2.1A when fully charged. These values don't take into account computational demand of autoguiding.  Included in these values is 0.12A for the 12VDC-to-19VDC converter. Plugging in the Orion StarShoot Autoguider adds about 0.5A. Dimming the display to its minimum cuts half an amp from the draw.]
• Dew Prevention: I use Kendrick dew prevention, and the power need varies greatly with the telescope objective diameter. At 100% power the strip I use for the guide scope draws 0.3A, for the 4" scope 0.9A, and for the 9.25" scope, 2A.  So my range is 1.2 to 2.3A. Because I almost always use a power setting half this, I'll take the dew demand as .5 to 1A [The low setting actually ranges from 0.17A (6" strap) to 0.97A (28" strap)]

How does this add up?

1. The maximum is imaging with the C9.25 on a dewy night with autoguiding: 6.75A [6.0A]
2. Small scope on a dewy night with autoguiding, 6.25A [5.2A]
3. On a dewless night both drop to about 5.75A [5.0A].
4. DSLR + lens, no guiding? 4.3A [0.7A].
5. There are more combinations, but let's stop here.

The reality is that I seldom image more than a few hours a night. If we cap the maximum number of hours at four per night, the nightly power need for Case 2 above is about 26AH [21Ah], so a four-night party would need 104AH [83Ah] if it was clear every night.

At the other extreme is using a DSLR and using the laptop only for focusing. This would require only 21AH [11Ah]!


Next time in Part 2, can I use batteries to meet my imaging needs?

Dew controller and image noise

Well over a year ago I began noticing bands of noise on my images. Here's an example:

Stretched Light Frame showing noise band

And here's a patch of it at full scale (look just below the nebulosity). The appearance of the band will vary from frame to frame, but it's always a horizontal strip of hash. Longer exposures have more bands. Here's what it looks like at full scale:

Noise band at full scale

When that band covers your target, it overlays a great deal of noise that is difficult to remove. ImagesPlus noise removal reduces it, but you can be left with a light band.

I could not figure out what the source was. At first I thought it might be AC line noise (I was running using AC power). Moving to battery power didn't get rid of it. Bad cables to the CCD were suggested by others, but lots of cable swapping didn't fix it. Maybe it was the CCD camera itself? Online searches didn't suggest the camera had any problems like that. I did see some implications of interference from other devices being powered by shared batteries, so I isolated the CCD. The noise remained.

This was an intermittent problem, however. I didn't tumble to the cause until last week at Jeffers, while I was imaging M20/21. Almost every frame was noisy. For some reason I turned off the dew controller, and like magic the noise was gone. I imaged M17 the next night with no dew control (it wasn't needed) and every frame was free of the noise.

A more directed online search led me to a comment about the controller I use, the Model VI:

The Culprit: Kendrick Model VI

I immediately launched into more research and was happy to learn that Kendrick made an RFI-free controller that was in my budget range, the Standard Dual-Channel Controller (SDCC). $114 and shipped free from Astronomics.

The Solution: Kendrick Standard Dual-Channel Controller

A night of imaging with the SDCC keeping everything dry produced images that were all RFI noise-free.

If you're imaging and seeing a lot of horizontal noise bands, it may be your dew controller.