Sunday, July 28, 2013

Mach1 GTO from Astro-Physics - Guiding

I spend some time on the PHD parameters to improve guiding. With the default values of PHD, I can get my combined RMS error easily below 1 arcsec. Doesn't sound like much, but with the CGEM that was already a struggle. Good.

After some more optimization, I ended up with graphs like this one:
RMS error: 0.56 arcsec (peak 1.39)

RA RMS error: 0.12 arcsec (peak 0.3) 
DEC RMS error: 0.16 arcsec (peak 1.06)

And very often I got graphs like this one:

Something is clearly wrong with DEC guiding...

I asked on the ap-gto mailing list and received a number of good suggestions:
  • Calibration isn't correct which leads to an overcorrection in DEC
  • Lower aggressiveness, so that PHD does not overcorrect
  • Make sure that the guide stars are not distorted
  • Make sure that the OAG is pushed in as the stars in the outer areas might be too dim
  • One user has the exact same setup that I have - except that he does not use a focal reducer. He sent me his settings:
    RA Aggressiveness: 60
    RA Hysteresis: 10
    Max Dec Duration: 75
    Min Motion: 0.70
    Calibration Steps: 125msec
    Auto/Resist Switching
    Extreme dithering and Settled at < 0.5
    3 - 4 sec guiding exposure.
    I could remove my focal reducer and try these out.
Last night I tried these out:
  • Lowered my calibration step size - now PHD needs 20+ steps for a calibration run
  • Played with aggressiveness
  • Checked if the OAG is still parfocal, pushed the OAG all in
But with the same results. I then updated PHD to the latest version and even installed PHD2 (alpha) to check if this is some PHD bug. But same result.

I then tried out some things:

First, I took an 5 min image of the Eagle Nebula unguided. Here is a magnified version:
The stars are elongated mostly in RA direction.

The same image with PHD guiding - DEC set to auto:
Now the stars are mostly elongated in DEC direction - RA seems to be fixed.

Now with PHD guiding - DEC guiding off:
Very round stars.

The with DEC only North:
Also, very round stars.

So, RA guiding really seems to be good, but the DEC=auto guiding is a problem. Now, in PHD2, there are more possibilities for DEC guiding (identity, resist switch, lowpass, lowpass2, hysteresis). I played with those, but couldn't improve DEC guiding. And then I read in the release notes, that in the current version of PHD2, calibration only works with DEC=auto. So, I had to run all these experiments again. But it got very late again and I went to bed...

I wanted to make sure that my scope is not out of balance. The Mach1 is quite sticky, so balancing isn't easy. So, I removed my OTA from the scope and balanced it on a pencil. I noted that point on the OTA and made sure that this point is in the middle of the dovetail saddle.

Next, I removed the focal reducer, so that I could try out the parameters (above) that I received. Here is the result:

Another idea that came from the ap-gto mailing list was that the DEC gears might be meshed too tightly. This pointed me to checking my cables that are now routed through the mount - maybe they are getting stuck somewhere. I just moved them out of the mount and tried again:

Hmmm, still no luck. Well, the good news is that I can move the cables back inside, but I should take a closer look on the DEC gear...

I followed the instructions on how to remesh the gears. Tried again ... same result :-(

Now, I'm sending an email to tech support at astro physics...

Thursday, July 25, 2013

Mach1 GTO from Astro-Physics - Cabling

One of the main reasons why I bought the Mach1 mount is the ability to move all the cabling inside the mount. And have no dangling cables on the side or such. In total, I need 8(!) cables to run through the mount:
  • 3 USB (filter wheel, ccd, guider)
  • 1 power (ccd)
  • 1 serial (Robofocus)
  • 1 Autoguider (guider)
  • 2 dew shield (main scope, guidescope)
That's a lot of cables - especially considering that they will run through both axis, i.e. partially block the polar alignment scope.

First, I ordered 2 tray holders to put the 4 boxes on: Robofocus, USB hub, Dew Shield Controller, Power distributor. After a little bit of fiddling around, I found a page from astro physics that shows the different possibilities to mount the holder to the pier.

I ended up mounting the dew controller and Robofocus controller on the pier and the power distributor and USB hub on the leg next to it. Routing the cable through the mount wasn't too hard. It's just awesome having them completely out of the way! But they are now in the way of the polar alignment scope! Hmmmm, couldn't really figure out how to avoid that and asked at the ap-gto mailing list. Two good ideas:
  1. Fit a PVC tube around the polar alignment scope to go all the way through the mount
  2. Press the cables to the outside with a sheet of plastic that I roll and then put inside the housing.
First, I needed to find flat USB cables:
  • 1 Mini USB cable - 6 ft
  • 2 A/B USB cable - 5 ft
  • 1 Anderson power cable - 5 ft
And I found them on eBay (A/B, Mini). With some tape, I made sure that all cables are flat next to each other:

Then I took some plastic sheet, rolled it up and moved it inside the polar scope housing:

You can see the cables in the upper left side of the housing.

And with that, I can easily insert the RAPAS and have a completely unobstructed view! Awesome!

Friday, July 19, 2013

Mach1 GTO from Astro-Physics - Night 2

I wanted to focus on polar alignment and setting up my polar alignment scope. I got some good advice on how to use it on the ap-gto mailing list.

So, I started with the Polar Alignment from PEMPro. I could never get it to work with my CGEM scope. But with the Mach1 it wasn't a problem at all. I spent 1.5 hours trying to get polar alignment as accurate as possible. With our seeing conditions (starts flickered a lot) I could not get it below 0.1 arc mins.

Here is a 10 min unguided test shot:

There are some traces, but not a lot. Seems as if the polar alignment went very well.

Then I aligned the polar alignment scope such that Polaris was in the place that was indicated in the AP app. That will allow me to get very good polar alignment in the future just with the polar alignment scope.

And finally, I pointed to scope somewhere (Deneb) and started guiding to see if there is a difference.

Here is the best guiding graph from the best night at GSSP (i.e. near perfect seeing conditions):
RMS Error: 0.69 arcsec
Peak Error: 2.26 arcsec

And here is the guiding graph from tonight - without doing any any adjustments to the PHD parameters:
RMS Error: 0.40 arcsec
Peak Error: 1.15 arcsec

I can't wait what guiding I will get after I spend some time working on those PHD parameters!

Tuesday, July 16, 2013

Mach1 GTO from Astro-Physics - Night 1

And of course, tonight it's NOT clear. Clouds moved in!!! But at least there were enough holes in the sky until 11pm to try some things out:
  • Get outside, rough polar alignment (turn mount on top of eagle pier such that it points to north when I align the eagile legs with our pavement - that will make setup faster!)
    Worked really well.
  • Polar alignment through polar scope
    Worked not so well :-( I have to move the scope all the way to the grass - otherwise Polaris is just below the roof of our house.
  • Polar alignment with 2 star alignment
    Not so successful. I tried to follow the instructions, but couldn't get polar alignment really close. This will probably require more practice.
  • Sync
  • Try some slews
    Not so good - I guess I need to do a better job with polar alignment.
  • Check orthogonality (cone error)
    Couldn't do without a good polar alignment.
  • Use with TheSkyX
    Worked really well.
The mount was pretty loud indeed, but also very fast to slew. And no wobbling or such. I can't wait to use it for real!

New mount: Mach1 GTO from Astro-Physics

After I tried everything this year to make my CGEM work, I finally broke down and bought a new mount. I did some research and it seems as if the Mach1 GTO from Astro-Physics is one of the best portable mounts. I could not get it in the US anymore, but luckily Baader Planetarium in German still had one. It was in their showroom and they gave me 10% off!
Took a few days to get the money transferred (first from our US account to my German account, then from there to Baader). And then it took 2 weeks to ship the mount here (1 week for US customs).
But today, it finally arrived.

I unpacked everything. I read so much about the quality and the finish of Astro-Physics products that I expected only awesomeness. And I wasn't disappointed. The mount itself, the control box, the counterweight bar... everything felt robust and very high quality. The assembly was great - the pieces are all so well made and exact. A few times, I used the wrong size screw or such. And each time, I noticed it immediately: if it doesn't easily and smoothly fits, it's probably the wrong piece. Finally, I had the mount assembled on the Eagle Pier. I attached the impressive control box to the pier. And then connected the cables. For now, I'll route all the cables on the outside. But I really want to move them inside the mount (and with that move all the control boxes from the OTA to the pier). I also installed the polar scope.

Finally, I connected the scope to my laptop. Downloaded and configured the ASCOM driver from the Astro-Physics site. I tried both, the native and the ASCOM driver in TheSkyX - they both seem to work. Asked on the ap-gto mailing list which one to use.

... and then it was WAY past midnight and it got foggy. Time to go to bed.

Things to try out tomorrow night:
  • Get outside, rough polar alignment (turn mount on top of eagle pier such that it points to north when I align the eagile legs with our pavement - that will make setup faster!)
  • Polar alignment through polar scope
  • Polar alignment with Polaris alignment
  • Sync
  • Try some slews
  • Check orthogonality (cone error)
  • Use with TheSkyX

Sunday, July 14, 2013

More CCDAP evaluation: taking images

Back from GSSP, I want to evaluate CCDAutoPilot more. It was VERY handy at GSSP to take dusk flats. Although the problem that it automatically kicks in and starts taking dusk flats is still not fixed, it's still a very comfortable way to take flats.

I now wanted to try taking images. My first challenge was to set a target. There isn't an "add target" or such button on the main screen :-( After reading the manual, I found out that I can select (and center!) a target in TheSkyX and then with the "Get" button get it into CCDAP. That sort of works. It's just weird, that I have to center it (so that it is in the FOV). And then CCDAP labels the object FOVCenter - even in the image name.

Then setting all the parameters (binning, focus...) was very easy. I then started taking images:
  • The precision slew was working - but I think it shows the inaccuracy of the CGEM mount. Here is a sample log output:
    03:46:41 Precision slew try number 1
    03:46:41 Plate solving...
    03:46:41 Telescope RA: 22 37 45.3, Dec: +34 28 46
    03:47:29 C:\Users\Mark\Documents\CCDWare\CCDAutoPilot5\Images\SyncImages\
    03:47:30 Stars: 86, FWHM: 2.7 arc-sec.
    03:47:30 Solved RA: 22 36 57.3, Dec: +34 26 48, PA: 172.0
    03:47:35 Sync'd to RA: 22 37 36.6, Dec: +34 31 03
    03:47:36 Telescope RA: 22 37 36.7, Dec: +34 31 03
    03:47:36 Telescope reports RA: 22 37 36.7, Dec: +34 31 03
    03:47:36 Plate Solve Time: 54.5 sec.
    03:47:36 Pointing error (arcmin): RA 2.0; Dec -1.6
    03:47:36 Telescope connected
    03:47:36 Slewing scope...
    03:47:44 Slewed to RA: 22 37 44.4, Dec: +34 29 28, Jnow
    03:47:44 Mount settling for 3 sec. after slew.
    03:47:49 Telescope tracking on
    03:47:49 Sync'd
    03:47:49 Plate solving...
    03:47:50 Telescope RA: 22 37 45.4, Dec: +34 28 46
    03:48:00 C:\Users\Mark\Documents\CCDWare\CCDAutoPilot5\Images\SyncImages\
    03:48:01 Stars: 76, FWHM: 3.1 arc-sec.
    03:48:01 Solved RA: 22 37 05.5, Dec: +34 24 25, PA: 172.0
    03:48:07 Sync'd to RA: 22 37 44.8, Dec: +34 28 41
    03:48:07 Telescope RA: 22 37 44.9, Dec: +34 28 40
    03:48:07 Telescope reports RA: 22 37 44.9, Dec: +34 28 40
    03:48:07 Plate Solve Time: 17.2 sec.
    03:48:07 Pointing error (arcmin): RA -0.1; Dec 0.8
    03:48:07 Try 1 slew error: 48.1 arc-sec
    03:48:07 Precision slew try number 2
    03:48:08 Telescope connected
    03:48:08 Slewing scope...
    03:48:16 Slewed to RA: 22 37 44.4, Dec: +34 29 28, Jnow
    03:48:16 Mount settling for 3 sec. after slew.
    03:48:22 Telescope tracking on
    03:48:22 Sync'd
    03:48:22 Plate solving...
    03:48:22 Telescope RA: 22 37 45.4, Dec: +34 29 22
    03:48:33 C:\Users\Mark\Documents\CCDWare\CCDAutoPilot5\Images\SyncImages\
    03:48:34 Stars: 87, FWHM: 2.8 arc-sec.
    03:48:34 Solved RA: 22 37 05.4, Dec: +34 25 09, PA: 172.0
    03:48:39 Sync'd to RA: 22 37 44.7, Dec: +34 29 24
    03:48:40 Telescope RA: 22 37 44.8, Dec: +34 29 24
    03:48:40 Telescope reports RA: 22 37 44.8, Dec: +34 29 24
    03:48:40 Plate Solve Time: 18.1 sec.
    03:48:40 Pointing error (arcmin): RA -0.1; Dec 0.1
    03:48:40 Try 2 slew error: 5.8 arc-sec
    It took 3 attempts and 2 minutes to get the error down to 5.8 arc-secs. But at least it worked.
  • Focusing with every new filter didn't work at all. The focus degraded from sequence to sequence. When I analyzed the @Focus2 log files, these are the first focusing graphs that I got:

    The first two are completely useless. The third one makes sense and leads to a correct focus. So, I'll have to work on my @focus2 routine to make it more robust.
    I should try to use the recommended focus range of 4500 to catch the outer, lower areas of the graph. Will do that tonight.
    I worked on the @Focus2 parameters and could create a rock-solid process. It converged and worked all the time. I think the problem is that when @Focus2 is invoked from CCDAP, it does not slew to an appropriate star, but tries to focus where the scope is pointed to. Will need to investigate further.
  • A weird bug(?) I found was that I can't enable tracking through TheSkyX (in the Telescope->Tools menu). Which is annoying, because CCDAP likes to put the scope into parking and then disable tracking...
  • And of course, I have to figure out guiding with CCDAP.
  • The good thing was the automatic meridian flip that CCDAP does.
But if I figure all this out, this will make taking images way easier. So, tonight, I'll work on the @focus2 routine and then try this out again.

Tuesday, July 9, 2013

Golden State Star Party - Night 4

The last night was a success - guiding was great and I took images of the Crescent Nebula and the remaining images for the Bubble nebula.

The day was (yet again) uneventful. We had another BBQ in the evening - people here really know how to make beef.

I also took some images of the the camp and its atmosphere:

The whole experience was awesome - I will definitively come back next year. Here are a couple of things to remember for next year:
  • A larger tent - preferably one where you can open the walls.
  • Shoestring Nikon cable, so that I can take wide field images with the DSLR on top of the scope
  • Solar panels to recharge the batteries (no more schlepping batteries over the camp ground) and/or a second battery recharger
  • The Celestron suspension pads
  • A thicker cover for the scope to make sure that it doesn't get so dusty during the day
  • Swiss Army knive (with cork screw!)
  • Larger Astroturf with shorter covering (or maybe I can use the blue tarp that I bought this year)
  • Red screens for phone and tablet
  • Water bottle
Larry and I also talked about bringing the kids next year. It would be great if they get to experience these skies too (just a few days ago Peter asked me why the milky way is called milky -if he were here, he would know!) We thought about some things that the kids could do:
  • They can observe the sky with my 6" scope - the should be able to use the hand control. We can give them a list of objects that they can slew to.
  • We can give them a list of Iridium flares and satelites to observe
  • The quadcopter
  • Kite
  • We can do day trips into the surroundings

Golden State Star Party - Night 3

Well, the guiding gods are not really with me. Although I moved my scope lower, I couldn't get better guiding then 1 arcsec RMS. Definitively not accurate enough for the Eagle Nebula:

One can make out some nebula details, but the stars are horrible :-(

But I had much better luck with my DSLR images last night. First, I took some shots of the milky way with our camp in the foreground:

A little dark - I might try these tonight with higher ISO.

After that I did extra wide angle images of the Sagittarius region, the Cassiopeia/Cygnus region and then a 50mm shot of the North America nebula. Here are the images just after stacking and super basic stretching:

 Yes, there are some artifacts - especially in the corners. But I hope that with some proper processing and adequate cropping these will turn out good.

4th Night

Monday, July 8, 2013

The Bubble Nebula (NGC 7635)

My first image from the Golden State Star Party:
(click on the image to get a full resolution image)

10x10min Luminance
10x7.5min Red, Green
5x7.5min Blue

The Bubble Nebula is an Ha II emission nebula in the constellation Cassiopeia. It's 11,000 lightyears from earth. The "bubble" is created by the stellar wind from a massive hot, 8.7 magnitude young central star (SAO 20575).

I still have to improve this image:
  • The blue images aren't as well focused as the other channels (and I have less blue data)
  • I have only done very little processing (setting background, some basic DDP stretching, HLVG)

... and I can't believe the difference between imaging from our backyard to imaging at a really dark site!

Golden State Star Party - Night 2

Last night was one of those nights that you don't want to have...

First, I moved my scope higher to avoid that accident from the night before where somebody stepped in front of the scope and ruined 3 images. Unfortunately, there was quite some wind last night and that together with the higher scope made guiding REALLY bad. I had between 1.3 and 1.9 arcsec RMS error :-(

My wide field images weren't much better. First, I had VERY good polar alignment. I then took various images with my 50mm lens (Cygnus region, Cassiopeia region, Sagittarius region, Andromeda Galaxy). All with 1 min exposures, the histograms looked great!
... and then I realized in the morning that I completely screwed up focus! I must have touched the focus ring on the camera at the beginning of the night because all but 1 image were out of focus :-(

But it still was a great night under the stars. I am still amazed by the number of stars and the milky way overhead. And had some interesting views through Larry's Dobsonian.

3rd Night

Sunday, July 7, 2013

Golden Gate Star Party - Night 1

The drive up here was (as expected) pretty boring.

I setup my whole rig and I really think I didn't forget anything!!!

At 8:30pm, I took my flats - first the entire scope didn't connect. Panic! But I just had to reboot the machine - probably something with the USB drivers (I think I forgot to disconnect properly at home).

When Polaris came out, I polar aligned my Polaris and mounted my Nikon camera for wide angle imaging.

At ~10pm, I started to align my scope - with the dark sky it was very easy and I think pretty accurate. Then I checked focus, collimation (CCDInspector still gives weird values, so I ignored it). And at 11pm I was ready to image - an hour earlier then I expected!

PHD calibration worked quickly - I got 0.6 arcsec RMS error. And so, I started to image NGC7635 (Bubble Nebula). I could very quickly see the difference from imaging from our backyard to imaging here: so much detail, so many stars!

Once my scope was busy, I tended to the Nikon. I pointed it first to the Cygnus region, I then tried the Sagittarius region - but my car was in the way. Next, Cassipeia, and finally Andromeda.

In between, I took a couple of looks through Larry's Dobsonian. It was quite impressive to see the Veil Nebula and other objects "live".

And at 1am I went to bed and let my rigs to their work.

The next morning, I first checked my PHD graph:

At the very end was dawn. But I'm not sure what happened during the night- maybe somebody stepped in front of the scope while I was asleep. The good thing is that PHD recaptured the star! When I checked my images, I could see that 2 Luminance images weren't good (the first disturbance), 5 Red (the second disturbance) and 2 Green images (it got too bright). So, I'll have to do these again. But because I started imaging an hour early, I have that spare time. But I might consider to move the scope up higher to avoid this from happening again.

Next, I checked my Nikon images. 2 min was a little bit too long - even with the Polarie polar scope alignment - there was clearly some curvature in the corners. But the main objects seem to be good. But the images are also WAY bright - the milky way is simply too bright :-) Here is an unprocessed 2 min image of Cygnus:

I also realized that I didn't take RAW images, but 2 copies of JPEG's :-( I did that a few months back when my 2nd storage card stopped working. Well, these wide angle views won't need a lot of stretching, so I think it'll be fine with JPEG.

I'll try 1 min next. When I then tried to stack the images with DSS, I had to increase the start detection threshold A LOT - otherwise, it would detect too many starts (and take A LONG time to register and stack). When setting the threshold to 41%, I still had 2000+ stars!

And finally, I had some morning exercise - I had to carry to the $#%%! heavy battery all the way to the front of the ground for recharging. This will be my daily workout for the next 4 days ...

Tuesday, July 2, 2013

Guiding to the Fritz??!!

A few days left to GSSP. And last night, I could not guide with a better accuracy then 1.2 arc seconds RMS error - with all my efforts I could get easily below sub one arcsec accuracy. I have no idea what I did or changed. I hope that it was just the case of really bad polar alignment or such. Will try tonight, but this would suck for my imaging plans this weekend :-(

... I tried this tonight again. And I am almost convinced that this is because of the hot weather and the thermal disturbance during the night. I took a 10 min unguided exposure and it actually looked pretty good (my polar alignment was pretty good). I then observed the guide star in the PHD window and it jumped around (left, right, up, down - all directions) very quickly. I.e. it didn't look as if the guiding had issues. Well, keeping my fingers crossed!

And the next night it was even better. Some of the best guiding ever (0.6 arcsec combined RMS error)!