Guiding Getting Better and Better..... sort of

.34" total guiding error!!!   I saw it briefly hit .29" for short periods.   Later in the evening, after a couple dithers, I started getting spikes in the DEC which increased the total error values to around .8 to 1.2.   :(    >sigh<   I double-checked to see if there were any cable snags and I didn't really encounter any problems or issues so I decided it was a balance issue.  Eventually, I had to do a meridian flip.  And the strange DEC spikes occurred again which challenges my assertion that it was a balance issue. 

It still might have been the USB cables coming from the guider and the camera.  The cables do stiffen up as temps drop and though it seemed fine, there might have been just enough tension to cause issues.    I really need to place a USB hub on the dual dovetail.   I also need to run some power to the hub. 

When I pointed the camera/lens combo to NGC 3343 (which is located in the north), I decided NOT to recalibrate and it guided well.   The previous session, I had decided to calibrate before shooting north and I got a warning message to not use a calibration that was so far from the Meridian.  When I did calibrate, my guiding ranged from .6" to 1.2" which sorta sucks considering I was pointing so far to the north.

So, my working thesis is that one shouldn't recalibrate if shooting to the extreme north.   I assume this applies to the south as well.

QHY Polemaster Works!!!

I've been quietly grumbling about the guiding performance of my AP900 mount for the past few years.   It hasn't been great, but it has been passable.   For my seeing conditions, I can't really complain since we really don't get many nights below 2 arc sec seeing.

My total guiding error tends to be around 1.25 sec. on average.   The real issue is that my stars tend to be slightly oblong (eccentric).   Often times, my DEC errors are double my RA errors.  This annoys me to no end considering that the mount is perfectly capable of great performance.   How do I know?   Back in August 2014, Charles and I made our second visit to Van Vleck Bunkhouse in California.  Though I had setup the AP900 that was purchased in 2009 a few times, the Van Vleck trip was its first real imaging session.   It performed impressively with 3 min unguided images with perfectly round stars.   I was using the Explore Scientific 80mm f/6 with a .8 Televue reducer.   When I did guide, my total guiding error was around .3 to .5 with PEC on.    Very good.

My polar alignment routine was primitive and started with the polar scope for rough alignment.  Then I used a modified drift alignment method using the DSLR and the hand controller.   I had read about this online, then tried it as documented in some of my earlier posts.   It seemed to work okay, but sometimes, it just didn't produce good results.  I base this upon the subsequent guiding that ranged from .5 to 1.5 seconds total error.   The problem with all this is that polar alignment can take 90 minutes or longer.    Also, the "DSLR iterative" method takes a toll on the handpad buttons.

Only recently have I experimented with placing weights on the DEC to see if one direction is beneficial over the other.   I discovered that placing a little weight so the DEC is imbalanced toward the COUNTERCLOCKWISE direction helps the guiding.  Since I've been using dual-saddle recently, I can achieve the same thing by making the LEFT side (as I face north) heavier than the right.

But the biggest improvement has come from the QHY Polemaster doodad.   A few nights ago, I met up with Jeff at Wupatki to do imaging.   I had him help me do the "first light" on the Polemaster.   It was a little confusing but within 15 minutes, we had completed the routine.   The first target I guided on produced .4 sec total error!   As the night progressed the error ranged from .4 to .8 depending on where I was pointing. 

Last night, I went out and used the Polemaster routine on my own.  I got the same results again!!!  The Polemaster is a godsend.   Including the rough polar alignment, the total time to get excellent polar alignment has been cut to 20 minutes total.   Now, I just have to get PEC going again.

Mount and Camera Problems in the Field

I've been trying to finish my Pleiades shots that I started last winter.   The plan has been to combine a bunch of 10 min exposures and 3 min exposures shot through the 80mm f/6 refractor.  A few nights ago, I started getting disconnect messages from the camera AND the mount.   While trying to troubleshoot, I even got a Blue Screen error.   When the camera disconnected, I was able to reconnect by powering it off/on.   When the mount disconnected, I couldn't get the USB to Serial adapter to reconnect unless I restarted the computer. 

It got to a point where even restarting wouldn't reconnect the darn USB to Serial adapter.  Almost like clockwork, I would get the message in the pic above during the initialization of PHD2 or after I started an imaging run in BackyardEOS.   I began to wonder if the adapter had gone bad.   But disconnecting and reconnecting sometimes fixed it.   Not always.

The first night these issues popped up, it was around midnight.   So, I assumed it was temperature related.   But I didn't know where in the chain the issue was happening.   Was it in the USB hub?   Was it a cable?     Was it a loose connection?    Was it the USB port in the laptop?

On that first night, during my troubleshooting, I noticed the USB plug into my laptop was cock-eyed and barely making a connection.   I plugged it back in, restarted the computer, and everything seemed fine.   But I was only able to use the rig for maybe 20 minutes before the moon came up.

I'm using a Star Tech USB hub.   Though the hub has a power connector, I've never felt the need to use it.   I've connected the Canon camera, the QHY autoguider, and the USB to Serial adapter for over 20+ sessions without any noteworthy issues.

So I took one of my small 12 volt 7 amp batteries and made a power supply for the hub.   I had a chance to use it a couple nights ago while doing a make-up session for a student at the Basis Astrophotography Workshop.   It didn't make a difference.   While trying to start an actual imaging session, the USB adapter started throwing up error messages AGAIN.   Luckily, after several restarts, I was able to coax the adapter back to life.   But we wasted more than half the session troubleshooting.

I decided I needed to make a few changes.   I remembered that I recently updated the AP V2 driver about a week ago.   Also, I switched to a different AC inverter for the deep-cycle battery.   So, I uninstalled the latest AP driver and reinstalled an older one (5.09.07).   I also went back to my old noisy AC inverter.   AND I tried a newer, shorter cable for the serial connection between the mount and USB adapter.    So, last night, under really good skies, it all worked fine!!!

Random jottings about the state of the art in astrophotography...

An interesting development occurred in the online imaging world when Cloudynights recently changed the name of their "CCD imaging" subforum to include CMOS.  It's now the "CCD/CMOS Astro Camera Imaging and Processing" subforum. At least 50% of the threads are about the newer ZWO ASI 1600 or the QHY 163 cameras.   Some folks are entering the imaging scene with the "new" CMOS technology and a whole bunch of others are either making the switch from DSLR or adding a second "ccd" camera to their equipment list.    These newer cameras have better QE than the last generation of CCD's -- specifically, they have a 30-50% higher QE than the recently popular KAF8300 cameras.  Both the ASI 1600 and QHY 163 camera use the Panasonic MN34230ALJ CMOS sensor which is used in security and surveillance cameras.    ATIK just entered the fray with their Horizon camera.  

I haven't seen so much sustained interest in a specific sensor in awhile.



Besides the fact that the KAF8300 is getting really "old" as an amateur ccd choice, I think price is getting people in the door.  The ASI 1600 is about half the price of a 8300-based camera.   (It's much less if you consider the 8300 choices from FLI, Apogee, and SBIG's STT camera.)  And there are now cheap filter choices from both ZWO and a company named Optolong.   One consequence of all this is that there are many more new PixInsight neophytes posting on Cloudynights.   There are regular discussions about workflows and processes which I find useful and interesting.   In fact, some folks are routinely posting their exact workflows with their finished images. 




Just a decade ago, monochrome imaging with filters used to be the domain of "serious" imagers.   But one of the draws of monochrome sensors with filters is that you can shoot narrowband.   H-alpha or Oxygen-III filters allow only a very narrow frequency range of light.  And more importantly, these filters block all other frequencies of light which includes the light we see as light pollution.  So, suburban backyard imagers are now able to shoot right through their city light pollution and capture nebulous objects.   This is obviously a draw for most folks who live in or near large cities.




Of course like all new tech, these CMOS cameras have some drawbacks.   While super sensitive, the sensors have amp noise which must be subtracted with darks.   The nature of the darks and signal noise seem to vary from one chip to the next.   Some people are having difficulty getting rid of the amp noise.  Also, many of these CMOS chips have shallow wells.   So, the stars saturate quickly and it can be tricky to go super long on your exposures.   The preference is to do many short exposures (like 100 x 2 min.) which also changes the equipment requirements a bit.   Finally, the size of the chips are somewhat restrictive.  If you want to go color, there are full-frame and APS-C choices.   But for mono, we're looking at APS-C and smaller.   




I don't know if it's a sign of anything, but I've been looking for a used ASI1600 on Astromart and they are hard to come by.   The ones that do appear usually sell within a day or two.




Just some observations as an alternative to the normal political noise that seems to permeate media these days...