Tuesday, January 22, 2013

Working on autofocusing with @Focus2

I posted on the Bisque forum and asked about my problems with autofocusing. Apart from the manual, someone pointed me to a good post - explaining it in more details.

Trying to determine a better step size:
  1. Critical focus zone
    With the Lepus reducer, I have a focal ratio of 6.2. That gives a critical focus zone of 6.2*6.2*2.2 = 84.568 microns
  2. Focuser Travel
    I measured how much the Robofocus focuser moves the focus tube: 9000 steps moved it ~7mm. That means I have a movement of about 0,778 microns per step.
The Range paremeter for @Focus2 should be about 40 times the size of the critical focus zone: 3382.72 microns ( = 84.568 * 40). That's equivalent to 4349 steps (3382.72 / 0.778). That's quite different from the default value of 1000. Though, I wonder what this will do to the focusing sequence. When I ran it with the smaller default value, the star blew up quite a lot...

I also increased the number of averages that @Focus2 takes to 5 - yes, that will take longer, but in my light polluted backyard, that's probably a better choice. At least for the beginning, I will also increase the Samples to 10 (5 on each size). Then I can analyze the logs data better. Once I have this working, I will try to decrease both values again to make this faster.

Finally, I have to set the star magnitude that I want to use and the exposure time. I'll try on the brighter side (mag 4). For a star of this magnitude I'll need ~0.2 secs exposure time.

But now I'm running into a different issue. If I set the range to 4500, SkyX tries to move from the initial focuser position to 2250 steps inward... and times out. I guess, Robofocus doesn't give any updates during the movement and then takes too long :-(

After lots of tries and error, I found out that moving Robofocus by 1400 steps still works (higher values timeout again). So, I had to use that x2 (=2800) as the range parameter.

With this setup, @Focus2 ran without complaining - good!

These are the first 2 v-curves:

Neither looking very good. But seeing conditions were pretty bad tonight: bright moon, light pollution and one of our neighbours had his fireplace going.

So, I inserted the Ha narrowband filter and tried again:

Looks better. But I noticed that the subframe was too small to show the defocused star. So, I turned off subframing, and now I got:
Now, this looks like a good v-curve. And focus was perfect!!!Now, if I could only figure out how to use the full range - that would make the fitted curve even more accurate. And then I can start optimizing the average and samples parameter and fit the subframe to speed the process up. 

Sunday, January 20, 2013

M42 - so many firsts

First image with my new camera and my new focuser
First narrowband image
First HDR combined image
First time, I'm imaging M42:

I overlayed 5 min and 2 min exposures with HDR Efex Pro to get the details in the bright center, but also the faint details in the outer layers.

It's clear, that I still have to get better at focusing though and processing though ...

The 2 min and 5 min stacked images are much sharper:

It seems as if combining them brought up a lot of details, but it also reduced the sharpness.

Saturday, January 19, 2013

Tried my first Ha narrowband imaging - can't focus

Last night, I tried my first Ha narrowband imaging. But I was unable to focus the scope properly.
  • Focus@ from SkyX didn't work. The stars that it would try (based on its ranges) were too dark with the narrowband filter. I tried some other stars - but they were apparently too bright and it didn't focus properly.
  • I then tried to focus with the Bahtinov mask. But even after I did that as good as possible, the image wasn't properly focused.
Here is a typical image that I got:

Here is a zoomed-in image:

Need to figure this out tonight.

  • Can't get autoguiding with SkyX to work - have to use PHD for the time being
  • The USB extension cord didn't work for the scope control. I'll try out what happens if I use a USB hub - that would have the good side effect of only having one cable routed into the house.

Tuesday, January 8, 2013

Getting used to SkyX

Today, I did the whole 2 star alignment and polar alignment with the CCD camera. For the first two stars, I needed the star finder. But after that all stars immediately showed up in the CCD screen. And with the crosshairs in the screen, I could do a pretty exact alignment. And it was fast too!

Then I synchronized my mount with SkyX and used SkyX for slewing to other objects. This is very convenient and pretty exact.

After that, I finally wanted to try out collimation with CCD Inspector. The first attempts were complete failures - the Collimation view and the Image view were flickering like crazy, message popups flickered (too fast to read). It took me a while to figure out that I shouldn't let CCD Inspector delete the images that it analyzed (but why does it offer the option then??)

First, I used this as an opportunity to replace the default collimation screws with Bob's collimation knobs. That made the whole process much easier.

Then I tried to follow the CCD Inspector "Single (Defocused) Star collimation method". But what it defined as collimation was clearly not collimated. I could see with my naked eye that the defocused star was not concentric. After the second attempt I gave up and collimated just visually. I don't think it's that good. Next time I'll try the "Multi star collimation method".

During the collimation process, I had to slew the scope multiple times (to get the collimation star back in the center). I found that this was much easier with the handset from my scope vs. the controls in SkyX!

Thursday, January 3, 2013

Lodestar rocks!

Last night, I tried again to setup autoguiding with Lodestar/SkyX. First, I had some weird artifacts in the Lodestar image. But after a while they went away. When I then started using it, I couldn't believe how many stars it picked up. The Orion 3MP autoguider would normally pick up a few faint stars in any image. Lodestar had almost 100 stars - and all of them very crisp and clear. Unfortunately, I didn't store any images for comparison.

Then I calibrated my scope in SkyX - I had to set the calibration time to some really high values (120 seconds!) But after that was done, starting guiding was a breeze. In the end, I suffered the same image shift issue that I had with PHD. It must be either bad polar alignment or shift between the guidescope on top and the main scope. I am looking forward to seeing how this will work once I can use the OAG (still waiting for the filter wheel :-(

Just for fun, I then wanted to take some guided images (without filter). But I forgot that SkyX by default always wants to take a dark image. So, when I came back an hour later, all I could see was a popup box saying that I need to cover my scope and press OK... Well, it was only a test, but I have to remember that in the future!

At the beginning of the imaging session, I tried to use the CCD camera for 2 star and polar alignment. But all I got was a black image - no stars. Not even when I put a light in front of the scope did it catch anything. I finally realized, that the (new 3 Ampere) fuse blew again and that the camera didn't get any cooling. It was all the way up to 13 degrees - which apparently is so high that you don't see anything. After I started cooling it, I did the alignment again. The field of view of the CCD camera is so small, that I needed to center the star very well in the starfinder. What helped was to use the lodestar with continuous photos as well. Because of the larger field of view, it showed the star immediately. I then used its image in SkyX to do a rough alignment and then the star would show up in the field of view of the CCD and I could center it there. Also, having the crosshairs in the camera displays in SkyX helped a lot! After the first 2 or 3 stars, all subsequent stars showed up immediately in the CCD camera and alignment was a breeze!

Over the weekend, I will read more about autofocusing with Robofocus. There are lots of threads on the bisque forum. And I should also try the collimation with CCDInspector. What I did find out was that moving the focus in still works (yesterday, I thought that it won't stop). This is the backlash setting that I set (as recommended to a really high value). Robofocus oversteps by this many steps and then moves the focuser back.

So, I still have to figure out what to do about the fuse for the CCD camera. Starlight Xpress support said that 3 Ampere should be high enough. But when I turn on the camera it can have a REALLY high spike. Maybe I follow John Smith' recommendation and not use any fuse for the camera at all.

And the cable in the 12 Volt AC/DC converter broke :-( Need to get a new one. That's the second cable that broke (the other was the original Laptop power supply). Ordered a new one. But I have to figure out what to do about cable breakage...

Tuesday, January 1, 2013

First experience with new equipment

Finally, a clear night and I could try out my new equipment:

1. Manual focusing
Although Robofocus is incredibly slow, manual focusing was very easy. And that I can store all the focusing positions (eyepiece, camera, with / without diagonal...) will help a lot. Yes, it won't be 100% accurate because of the SCT focusing mechanism, but close enough. Very happy with it!

2. Using the CCD camera
Using the CCD camera through SkyX was easy. Setup was easy. Taking pictures was easy - SkyX takes a dark frame to improve the quality of the pictures. Great! Played a little bit with binning.

3. Autofocusing with @Focus2
This did NOT work at all. Everytime I tried this, SkyX would start moving the focuser in, but not stop. And at some point time out. Not sure if I have to adjust the parameters or if there is something wrong. Another weird thing was that after using Robofocus through SkyX, moving the focuser in did not stop anymore. That could explain the wrong behavior...
But I also need to use dimmer stars - not the ones that I use for autoguiding. Well, lots to learn here!

4. Manual focusing with SkyX
For the love of my life I could not find any buttons or control to move the focuser from within SkyX :-(

5. Autoguiding
There were tons and tons of issues with getting the Lodestar working. First, I couldn't connect it in SkyX. Then I tried PHD - I could connect in the Ascom camera chooser, but then PHD gave an error message. Finally, I tried the Lodestar program itself. I couldn't connect either - error message: "could not write to sxvio output". I couldn't find anything online about it. I unplugged the camera, restarted and at some point it worked. And after (too) many tries, I could get it to work in SkyX. And finally, I could start autoguiding. Though the image was still shifting - not only the image from the CCD camera, but the autoguiding image itself. Not sure if SkyX even communicates with the mount ...

Well, not too bad for a first try with new hard- and new software!

Locked Focuser and calibrating Robofocus

When I calibrated Robofocus, I needed to move the focuser in as much as possible. I completely underestimated how much force Robofocus applies to the focuser. When I was done, the focus knob was completely locked! Neither with Robofucs nor manually could I unlock it (aka move it out) :-(

I asked at the Celestron Edge HD user group, Celestron support and also Robofocus support. Celestron and Robocus support didn't reply at all. From the user group I got two tips: a) loosen the mirror locks at the back of the scope, and b) contact Ed Thomas from Deep Space Products.

Ed Thomas gave me the additional tip to loosen the screw in the focuser itself.

I did both and then used Robofocus to try to move the focuser out. After the belt slipped a few times, the focus knob indeed came loose. I then removed the Robofocus knob and could turn the focus knob easily manually. Phew!!!

So, back to calibrating Robofocus. First, I set the backlash correctly. The Robofocus control program is a little weird in that it doesn't have a "Save" or "Set" button. Most settings seem to be set when tabbing out of the edit field (e.g. step size). But the backlash value wasn't. I used the "Data Traffic" window which shows the data traffic between computer and the control box. And indeed, nothing was sent when I tabbed out. After playing with the form, I figured out that one has to press <Enter> for setting the value. As recommended, I set it to 125 (1000 / step size) for my SCT scope. Then I moved the focuser all the way out again. And then Robofocus moves it in until you stop it. This time, I was on guard and stopped it immediately. Yes!

Unfortunately, the stepsize was too large (8) and I ended up with a max travel of 22198 (Robofocus can have up to 65000 max travel). So, I moved the focuser all the way out again. Set the step size to 4, backlash to 250 and started calibration again. I nervously observed what would happen when I hit position 0 again. But it seemed as if the focuser was indeed only half way in and Robofocus moved into negatives without any problem. At about -22000, the belt slipped again and I stopped the calibration run. Strangely enough, the max travel was still at 22198. It should have been roughly double that. I moved the focuser back to position 20000 and it was now roughly half in. So, I set the max travel position manually to 44000 and started to move the focuser further out - carefully observing if the belt slips again. At around 43600 the belt slipped again. I moved the focuser back to position 42000 and set the max travel position to 43000. This should be enough (I doubt that I will need the extreme in or out position anyway).

Now, I'm ready for the first real usage - the sky is still clear, so I'm hopeful that I can finally try it out tonight!