Wednesday, November 28, 2018

Rima Hyginus (again)

Another attempt on 11/15/2018...



Best 350 out of 5000.   C11, 2.5x barlow, ASI 174 camera.

I think this shows a little more detail than my previous post of this area.  Technically, the big difference is that I'm shooting through a 2.5x barlow and stacking more frames.   Also, though you can't really tell, I shot with much more exposure time.  There are areas to the right (which have been cropped out) that are completely blown out due to overexposure.  


Alpine Valley Rille

Barely, barely caught the rille which is the faint line in the floor of the valley.   Not the best shot but this is the 4th attempt to shoot this rille.


Best 250 frames out of 5000.   Data captured on 11/15/18.   C11, 2.5x barlow, ASI 174 camera.

(*Interesting processing note:  I tried several times to bring it into Registax to sharpen via "wavelets", but it would create a muddy picture that made it look like there were multiple rilles in the Valley.   I finally took the unsharpened master from Autostakkert and took it DIRECTLY into Photoshop.   Here's the surprise:  Sharpening in the Camera Raw filter environment duplicated the funny results from Registax wavelets;  however, doing a basic UNSHARP MASK worked way better in bringing out detail without introducing strange artifacts!   Victory for UNSHARP MASK!!!)


Wednesday, November 14, 2018

Petavius Rille


Petavius Crater is pretty large at approx. 177 km wide.   As a point of comparison, the often observed Plato Crater is 109 km.   The prominent rille is estimated at 80 km long and it seems to rise up to the top of the crater wall.   My rough guess is that the rille is about 3-4 km wide, which is about 2-3 miles wide.

(As another point of comparison, Gassendi Crater is 110 km and Lacus Mortis is 150 km wide.)

Data was captured 10/26/18 at approx. 1:22 am local time.  16.5 day old moon.  C11, ASI 174mm camera, 610nm filter, flats used.   This is about 400 frames out of 6000.


Sunday, November 11, 2018

Lacus Mortis (Lake of Death)


Shot on 10/29/2018.   The conditions were challenging as there were high cirrus clouds moving across the moon.  Made for a very moody image, but poor seeing.  Same technical info as previous shot with the C11, ASI 174mm camera, 2.5x barlow, captured in SharpCap Pro.   About 1000 frames stacked (out of 5k).

The main rille here is Rima Bürg running from left to right.   The secondary rille almost runs perpendicular to it.   There are various small rille in the upper half of the "lake".

No one online seems to know why it's called the Lake of Death.   To me, in this phase (19.7 days old), this area seems quite spooky.   On the left part of the lake, the two relatively straight walls seem to suggest an overall hexagonal shape.  Also, there are 3 scratch marks to the right entering into the shadows -- like the scratch marks of an evil beast.   :)


Saturday, November 10, 2018

Rimae Between Gassendi and Mersenius Craters


Best 330 frames out of a 1000 through C11.   Camera was ASI174 with TV 2.5x barlow.   Flats were taken because the barlow had numerous tiny scratches and dust in the glass elements.    Sharpcap Pro capture software allowed a "live" dark to be taken.

Shot on 10/20/2018.    Moon was 10.4 days old.

Stacked with Autostakkert (ver 3.0.14), used wavelets in Registax and final enhancements in Photoshop.

The top crater is Gassendi and the largish crater in partial shadow to the left is Mersenius.  The mare is Humorum.

(Note to self:  Set alignpoints (AP) in Autostakkert manually.   Use approx. 300 points.   The default alignpoints resulted in vertical/horizontal line artifacts near bright features.)

Wednesday, November 7, 2018

Big Jagged Lines = BAD

Here's what it looked like yesterday:


Here's what it looked like earlier this evening:

😟


Later it gets better...


Here's BackyardEOS showing the Angelfish frames coming down:

 

Tuesday, November 6, 2018

Misc Notes on Wind and Approaching Comet

Shooting Angelfish Nebula.    Very windy conditions.   Seeing is horrible and guiding is bad.   Straight up Mirfak is twinkling and blinking at times.

Not much to report but general misery.

Took about 20 minutes of 46P/Wirtanen earlier and the guiding was down in the 4 arc second range.   Stars seemed out of focus even though bahtinov mask was used.   Oh well.

46P/Wirtanen presents as dim and green.   Little to no tail visible.   I'm thinking this will be one of the those fat, wide comets when it's near earth in December.

My super general guess is still mag 9 - 10 right now.

Still need to make a wooden makeshift laptop box for this windy weather.

Saturday, November 3, 2018

Flagstaff Star Party 2018

I was a telescope host at this year's Flagstaff Star Party.   There was a professional photographer, Abe Snider, who was covering the event.   He happened to snap this cool pic of me at the scope.


Abe's impressive landscape work can be seen here.

Thursday, November 1, 2018

Tracking Problem: Horrible Right-Ascension Errors

So if you find an RA error where the RA line in PHD2 never reaches the middle, that can mean that polar alignment is really bad.   OR......

It can mean some idiot left the tracking speed on "Lunar" on the hand controller.  


I couldn't find the emoji for the head slap.

Saturday, October 27, 2018

C11 images

Some single frames from the C11...

First a raw file converted to JPG.  This is a 30 sec at 25600 ISO of M31... (click to enlarge)




 
Lots of fine dark nebulosity detail near the core.   It's not rare to see this detail, but it's surprising that such fine detail came out through ISO 25600 and an SCT.  😱   The second pic is the same frame that had some color correction and contrast features increased.   Coma is obscuring a fair bit of detail near the core.

The vignetting is obvious and is caused by the OAG which isn't really designed for full-frame sensors.

Next are two shots of NGC 925 at 5 and 10 minutes at 3200 ISO.   Much to my surprise, the guiding was good.




Here is the 10 minute exposure with a little color correction and contrast boosts...


Obviously, I need to stack at least 50-60 of these to make a decent image, but I'm happy with these single, "investigative" frames.

 And lastly a comparison from the old Tak102 and the C11...

 I was going to sell the C11, but I think it's actually a decent deep-space imaging scope.   

Now I just need a good field flattener...   hm...


Monday, October 22, 2018

Some Notes on the C11 and Imaging


This is just a brain dump of the various problems I had trying to get the C11 up and running last night.   (Extremely long, boring and detailed notes.)



It's often said that the SCT is not the best option for those who want to get into imaging.  And last night, I was reminded of why.  I've been around the block enough to know that IF you are going to shoot with the SCT, you will be dealing with a litany of potential problems:

1)  Dewing over the corrector plate.

2)  Tube currents/Heat plumes.

3)  Focus shift due to the aluminum tube.

4)  Mirror flop during an imaging run AND when you move the telescope.

5)  Not enough stars if you choose to use an OAG (off-axis guider).

6)  Poor guiding due to separate guide scope attached to the OTA.

7)  Pointing not accurate enough with GOTO because your field of view is tiny.

8)  Mount not up to guiding accurately resulting in trails and weird shapes.

9)  Coma, coma, coma...   spherical abberation?

10)  Collimation?   What?

11)  PLUS all the miscellaneous problems associated with imaging in general.


Spoiler alert:  I was able to deal with all the problems -- though it took 5-6 hours. (Technically, I didn't even try No. 6 -- it's a fool's errand in my opinion to use a separate guide scope.)


1)  I have two dew shields for the C11 -- don't ask me why.   One is a plain ABS-plastic type of affair that seals together by velcro.    It's basically a rolled-up tube.   At the beginning of the evening, after initial cooldown of approx. 1 hours, I secured the new dew shield around the front of the tube.   It sags.   No matter how much you finagle with it, it sags.  If pointed straight up, you can get it to stay pretty co-planar with the tube.

I spent an hour shooting video of the moon.   I'm trying to continue my series on large rilles (or rimae) and I got some footage of some rilles around Mare Humorum.   As it was getting chilly, I decided to grab some hot chocolate.

When I came back out, I fired up the video camera and pointed the scope toward Orion's belt.  Increased exposure from 1/40th to 3.5 seconds -- nothing.   Increased to 5 seconds -- again nothing.   Changed the gain -- nothing again.   Eventually I found a bright star, but only the star was visible, nothing around it.  My first ridiculous thought was, 'Maybe I'm pointing at a barren part of the sky and since I'm shooting at F/10 everything is dim...'   I looked up and there were clouds moving through Orion.   A-ha!   I waited 5-10 minutes and then the clouds moved on, but the situation was the same.   I increased exposure to 10 seconds.    I could only see super bright stars.

I finally looked down the crooked dew shield and the light from my headlamp was a big red bloom of diffuse color.   A layer of dew had coated my corrector.    Surprised?   No.

My other dew shield has a built-in dew heater.  The dew shield has a notch that allows it to sit much closer in to the tube.   It sagged much less substantially than the basic dew shield.   I found my dew controller and plugged in the heater then set the temperature for the max. setting.   After 5 minutes, I could barely feel a little warmth from the outside of the shield.   For good measure, I found a couple of shoe warmers (similiar to chemical hand warmers) and put them in the bottom of the dew shield for good measure.   After waiting for an hour (more hot drinks), about 3/4" of the outer corrector had cleared of dew.   Another 30 minutes, it hadn't gotten any better.

I thought of calling it a night, but then I remembered my wife's hair dryer.   I grabbed it and used it on the low setting.  I kept the dryer at least 18 inches away and moved in a circular motion.   After 2 minutes, nothing seemed to change.   (Typical.)   Then the dew started becoming less dense and it was clearing near the center.   After another 2-3 minutes of slow circles, the dew was gone.   I immediately placed the heated dew shield back in place and dew was not a problem for the rest of the evening.

Lesson:  Give up and never try.   Um... I mean no matter what the supposed conditions, place the dew shield and dew heater on the SCT after initial setup.   Once dew gets going, it's really hard to remove.

2)   When I setup the C11, I usually open the back, point the scope down and let the heat rise out of the tube.  Usually, 1 to 1.5 hours is sufficient for this initial cooldown.   (It's not a bad idea to keep the diagonal and eyepieces out as well so they can cool to ambient temps.   Keep them covered.)   Before imaging, I usually spend 15-20 minutes doing a little visual work.   And in this case, I was able to check off a few items off of my lunar observing list.   The views were surprisingly decent with only a little shimmer through a 14mm EP.    As I switched to 8mm (~350x mag), I noticed that conditions were "worsening".   In the span of 5-6 minutes, it went from occasional shimmering to a more constant shimmering. 

By the time I setup the imaging gear, the moon was boiling in the camera view.   It just got worse and worse as time wore on.   (I wonder if the camera heat was also contributing.)   Temps were still dropping and the tube was dripping from all the dew.   The problem is that the aluminum tube can drop below ambient and create all kinds of heat current.   When I defocused on a star, you could see the heat plume like a wiggling line perpendicular to the round star.

There clearly needs to be a way to get the hot air out of the tube throughout the night -- I am considering drilling 2 holes and installing fans on the back.   Also, I'm considering a small fan on the top near the corrector. (I wonder what the smallest fan is?   20mm?)

By 3 am, the scope seemed to have equilibrated as the frames coming down from the 6D were decent.

3)   I used a Bhatinov mask to help focus.   This is a pretty decent way to focus.  But as I did a series of shots over the course of an hour, it was clear that the stars were becoming larger and more bloated.  I was loosing critical focus but since I was really just testing, it was okay.

I think an upgraded focuser with a motor drive will solve this issue down the road.   I think it needs to be refocused probably every 20-30 minutes in the early evening, then maybe every 45 minutes.   To really nail this focus issue, one could try the temperature compensating focuser from Optec or the ONAG from Innovations Foresight.

4)  Later in the evening, I was able to get some longer shots with the 6D through the C11.  Two things stood out: a)  I had obvious hard vignetting in all the corners.  The vignette was curved so the edge of the OAG was obviously in the way.   (More on this later.)  b)  Outside of the central 25% of the image there was obvious star bloating.   It got so bad in the corners that the stars looked like warped donuts.   Much to my surprise the central 10-15% was really sharp.   This made me rethink selling this OTA.  The bloating was much more pronounced on the "left" side of the image and it seemed the central area (the best area in terms of sharpness) was actually right of center.

I think what's going on is that the nature of the focuser pushes the "right" side of the mirror closer to the corrector plate resulting in a "tilt" that causes the non-symmetric coma pattern.   This is one of the reasons I'd like to do a Roth Ritter mod so that I not only correct focus shift, but also remove the tilt.

5)  So I used the TSOAG9 off-axis guider from TS telescopes to connect the 6D and the guide camera.  I had to remove the off-axis prism to connect everything together.   The TSOAG9 is a pretty clever OAG since it only takes up the thickness of a regular T-adapter.   That means that you can incorporate off-axis guiding and still be able to connect to accessories like a coma corrector or a flattener.   Though it's a wide (48mm width vs 42mm) t-type adapter, it's NOT wide enough to let the sensor of the full-frame Canon to see through.   All the corners had strong vignetting.

No matter where I placed the height of the guide camera, I couldn't see any stars!  I spent a good 30 minutes trying every conceivable position -- really far out and really close in.  A couple times I tapped the surface of the CMOS chamber glass.   I lengthened the exposures to 10 seconds -- nothing.

But at some point, the image screen froze (not the computer) and no images would come down.   Aha!  I thought it was buggy camera drivers so I restarted the computer.  Just for kicks I took another image through the 6D -- about 30 seconds.    A weird set of prismatic streaks were evident in the bottom of the frame.  What!?!!?!!   It was like a spectrum...    from an optical prism!

The OAG prism was facing the wrong way -- the guide camera wasn't collecting any light because it was facing the sensor.   :o

I quickly turned the pick-off prism around and was in business.   The stars were not smears or streaks but they were all comatic -- with a bright center and a trailing bloom of light.

5a)  Immediately, I tried calibrating with the new setup.   It would fail calibration after two or three steps to the west.   I would get the dreaded "star lost" message over and over again.   I could see the star on the screen...  why was it lost?    After trying 5-6 times, I noticed that PHD was trying to figure out where the star was before it ended it's command to move the mount!   So it was only seeing a smear of a star.   I was puzzled.

...and a bit depressed so I took another 30 second exposure through the 6D.   There were streaks!   I tried another one and there were two globs of concentrated light for every star!   I felt stupid like a complete newbie trying imaging for the first time.  More puzzlement.   The evening was feeling like it was going to be a complete waste.

5b)  Then I started looking at all the cables -- everything seemed fine and familiar, no snags around the RA axis.   Then I tried the power cable for the dew shield, it felt heavy, it pulled the shield down.

The scope had moved in a way that it was essentially dragging the dew controller which I had left on top of the (now soaked) deep-cycle battery.   I moved the dew controller up to a bungee cord I had tied to the pier.   Now everything seemed fine.

Before I tried recalibrating, I had a vague deja vu moment because I've had guiding issues with my 8" f/6 reflector.    I wanted to double-check that PHD knew that I was guiding at 2800mm focal length.   When I checked the settings in Advanced Setup, it did NOT know my focal length.   I corrected that info.   Also, PHD has a setting that allows it to "care less" about the shape of the star.   It's under the guiding tab in Advanced Setup.  The default setting for Tolerance is 50, but if you set it high like at 95, it doesn't care what shape the star is.   After I set it, it calibrated very quickly.

The guiding was very good at 2800mm focal length.   I was quite relieved.

6)  No comment.

7)  So originally, I was going to shoot the Horsehead.   But I wanted to get a couple of guided test shots on the Orion Nebula.  I used goto to slew to M42.  Nothing.   The C11 has a super crappy finder scope that you can't center your target in the crosshairs of the finder.  I could tell that I was close to M42, but even after spending 20 minutes trying little steps to the left, right, up, and down, I couldn't get it on the 6D sensor.   Then the stars started disappearing and when I looked up, it was clouded over to the south.   Yay.   I waited about 20 minutes and 80% of the sky was covered by clouds.    There was a persistent hole to the Northwest so I goto'd to M31 and used the crappy finder to get it close and took an exposure.   I could see the edge of the humongous galaxy.   After five minutes of adjusting/moving the mount in a random direction-taking a picture-moving the mount-taking a picture-etc, etc I finally got the camera centered on M31, then synced it on the keypad.

I noticed a problem.   Whenever the goto finished, the mount had a tendency to continue moving eastward for 10-30 seconds.   I could click "W" on the keypad to stop it.   But it was a persistent issue through the night.

After getting the mount calibrated in that area, I entered NGC 925 on the keypad and it slewed to the object.   It was pretty closely centered.   So, the key here is the go to a large known object (if possible) near your target, then sync the mount to that.   Afterwards your goto should be fine.
I used ISO 25600 and 10 second shots to see what I could see.

At some point, I need to try plate solving again to fix this pointing nonsense.

8)  I was pretty amazed at the mount's performance.   I've never shot at this long focal length and my initial tests showed tons of promise.   I was able to do both a clean 5 and 10 minute guided test with very round stars.   There was a hint of lack of eccentricity (fancy way of saying roundness) which pointed to a slight colllimation issue.  (The last time I had collimated was about 2 weeks ago.)

The C11 gets bundled with a CGX and CGX-L mounts these days.  I'm 90% sure that my results would have been less impressive with a CGX mount.     Always overmount.

9)  As I mentioned earlier, in my full-frame shots, there is evident coma outside of the central 25% of the image.

While I didn't have any kind of corrector, I have been looking at some possible choices.   The traditional one is the Celestron/Meade f/6.3 focal reducer.   I tried this device back in the day with my old Meade 8 SCT.   While it reduced "coma" by about 25-35%, it created strong vignetting in my film images.

There are a couple of more choices these days:

a)  The Starizona Full-Frame SCT reducer/corrector.   Expensive.   Probably 1k with adapters.

b)  Optec makes something which has identical specs but which is more expensive:  The NexGen NGC 316 f/7.5 reducer.   Haven't seen many results with this reducer.

c)  There was a 2 inch ASA corrector which seems to have been discontinued.   However, their website seems to have a 4 inch version!   (This may only apply to the pure Cassegrain, not the Schmidt-Cassegrain.)

Now there are other possiblities:

Astro-Physics makes a telecompressor that should reduce some coma.  27TVPH.   The problem with this is that I can't find a SINGLE example of the 27TVPH and a regular schmidt-cassegrain telescope.   But AP makes adapters that connect it to the SCT.   Hm...

I stumbled a guy who tried several correctors with his 8 inch SCT and strangely, the best one was the TV .8x reducer/corrector for fast refrators.  Another one of this results pages

The question here is:   Should I try the other Televue reducer/corrector ?   It would be awesome if I could get a moderate improvement of coma/spherical abberation with the Televue RFL-4087 which expects 800-1000mm focal length.   The TRF-2008 expects a 400-600mm focal length scope.

I also have the TS telescope 2.5 inch flattener.   The guy did have a result with this but it didn't seem to show any difference a bare scope and the 2.5 inch flattener.   One thing to note is that he didn't seem to have experimented with spacings.

Here's a reference to a doublet corrector for the SCT that no one seems to have made:

https://www.telescope-optics.net/field_flattener.htm#flattener

10)   It had been two weeks since I had collimated.  Based on the star shapes in the images, I think collimation could have been better.  Here is a link to a DIY collimation method:  The Duncan mask is mentioned here and here.


11)   I'm kind of exhuasted at this point.   Since this was a test run the cabling was a mess.   If I'm doing this for certain (meaning going full hog on the C11), then I need to add a top Losmandy plate so I can velcro USB and power hubs,  a mini-PC, dew controller, etc.


Some pics to follow...








Wednesday, October 3, 2018

Rima Hyginus and Surrounding Areas


Rima Hyginus is the crevice-like feature that runs up and down the right center of the image.  The little crater toward the center of the rima is Hyginus.  The dark oval feature toward the bottom is Mare Vaporum. 

The relatively large crater on the left edge is Manilius.   The medium-sized crater on the right edge is Triesnecker.   You can barely make out the rima associated with Triesnecker.

In the upper part of the image is another rimae, Ariadaeus.

Data taken this time through the neglected C11.   Best 64 frames out of 318 frames.   ZWO ASI 174 mini (a guide camera) was used.   The camera has much better dynamic range than the QHY 5LII that I used on my last lunar attempt. 

Saturday, September 22, 2018

Comet 21P/Giacobini-Zinner near M37




Here's my take on Comet 21P.   Data taken from my backyard with a Tak E130D reflector through the old Canon T3i.   72 x 60 seconds lights, 20 darks, 40 flats, 60 bias frames.   Processed though PixInsight.   Lights collected on 9/10/2018.

It was my first sojourn with the Tak E130D.   I spent the whole day (4-5 hours) trying to the get
the collimation figured out.    It's a horrible system.   When you move one of the three rear screws, it CHANGES what the other two screws do.  If one screw moved the laser up and down, after you change another screw, that prior screw then moves the laser right and left.   There is a chance it will work predictably, then with one more turn, it moves un-predictably.

It took me a week of trying to figure out how to get "CometAlignment" to work in PixInsight.  Like all new processes in PI, the learning curve was steep and I had to redo portions of the image over and over.   Online tutorials are awful as they cover a previous version of the process.  I took 7 pages of notes trying to understand the setttings.   Toward the end, I figured out I could improve the image by starting all over again, but at this point, that's not going to happen.   Hopefully, I can apply what I learned to 46P/Wirtanen in December.

The comet was barely visible through 8x40 binocs.   The head of the comet was quite apparent as a large fuzzy and faint star.   The tail was not apparent at all visually.


Wednesday, September 5, 2018

Solar Oven




Back in May I gave a presentation at Basis for a Solar Astronomy Day event.

One of the projects was to build a solar oven to make smores.   I tried 3 different designs -- all were painted black with flat black enamel from Home Depot.  The most successful design is pictured above. 

I recycled a box of caulking (yay for never ending house projects) by cutting a large hole, then covering the hole with saran wrap which was taped to form a rough seal.   After I placed the goodies in the box, I also taped it shut.   After 30 minutes in the mid-day sun, I had some nice smores.   The other two boxes did not have windows and they were generally 10 degrees cooler than the cellophane window box.   I was a little surprised as I assumed that the closed black box would be the hottest.   I guess good ole direct infrared energy is the most efficient way of delivering heat.


Tuesday, September 4, 2018

Schroter's Valley and Aristarchus


Data acquired on 8/6.  Through the 13.4" f/4.7 dob handheld.   Used the QHY5L-II, my guide camera.   Shot around 40 minutes of video, but had only maybe 2-3 minutes of usuable frames.   Stacked with Autostakkert, processed in PS.

Initially, I tried using wavelets in Registax to enhance the sharpness, but I found that it blew out details more readily than using the Raw Camera Filter in PS.

There is a sharp drop-off in detail outside the central 1/3 area.   Partly, this is due to the fact the
central area is raised like a mesa.   I found the focus to be extremely shallow -- the slightest movement made it unusable.  I also think the outer areas are suffering from coma as well.  So, I definitely plan to use the Paracorr next time.    Another thing to mention is that the dynamic range of the QHY5L is awful.   All the peripheral areas of the original frame are either blown out or in complete darkness.


Sunday, June 17, 2018

Milky Way again with T4i


Canon T4i, 18-55mm kit lens, F/4.5.   ISO 6400 (!!!)  80 x 12 sec exposures, 33 darks, 100 bias, 30 flats.   Shot at Winona with Jeff.



Saturday, June 9, 2018

Milky Way



Canon 6D with 50mm f/1.4 @ f/4, ISO 3200, 60 x 3 min lights, darks, flats, bias.   Shot at Winona and Wupatki sites.

Friday, April 13, 2018


Cutting the pieces for the Ross Null tester...




Testing the fit of the Ross Null lens.  It looks like I have about 1/8 inch space around the diameter.  I plan to put in cork supports and spacers in the gaps.  I have saran wrap down to prevent any wood dust or particles from directly touching the BK7 glass.


Tuesday, March 27, 2018

A couple years ago, Sony introduced their A7r and A7s series cameras.   These cameras were considered the answer for all of us who were reluctant to buy into the CCD/CMOS camera systems.   But soon after, Sony released a firmware update that effectively crippled their cameras for astrophotography use.

An online petition appeared and it attempts to create a pathway for those who want Sony to pay attention to the problem.

It seems like Sony could have easily made the firmware update "optional" in the camera menu.  The slight irony of all this is that Sony is currently one of the most popular producers of CCD and CMOS imaging sensors used by the astrophotography community.   Maybe it's time for someone in the Sony upper echelons to go to a star party?


Thursday, January 18, 2018

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.

Sunday, January 14, 2018

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!!!


Wednesday, January 10, 2018

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...