Saturday, August 12, 2017

April Observing Report

April 6, 2017
A cold front came through yesterday. Last night was clear and dry but tonight is even better EXCEPT for the nearly full moon looming overhead. Came out at 2000. Set up the ASI071MC-COOL at prime focus with the Lumicon DS filter. I was able to slowly drop the camera's temp to -20.

Synched the model on Dubhe and went to M-109 and started taking 60 second exposures at gain = 400. Frustratingly the camera / computer is still dropping 30 – 50% of the frames! A 60 sec exposure put the light curve maxima at only 15%, so I upped the exposure to 120 sec. Dropped about 7 frames in a row, very frustrating! I gotta change the wiring setup. I'm wasting too much time waiting on frames. Finally got an image and the 2 min exposure moved the luminescence to nearly 30%.

I was using a long active extension USB cable through a USB 3.0 powered hub to connect the camera to the computer. I removed the powered hub and the USB 3.0 extension cable. I hooked the StarShoot guider cam into the ASI071MC-COOL hub and ran a USB 3.0 cable from the ASI071MC-COOL to the laptop. Downloads are much faster and much fewer dropped frames at first with 30 second frames. When I upped the integration to 2 min, still there are too many drops ( nearly 50% of 2 min frames were dropped). Very frustrating. When I finally started imaging the M-109 the image contains an ice crystal, a lot of fogging, and a textile pattern!

I turned the cooling off and after a few minutes the ice, fogging, and textile pattern disappeared. I turned the camera's cooling to -10 C. As M-109 was approaching the meridian so I changed targets to M-101. At 2315 the ambient air temp is 54 F (12.2 C) with 63% humidity and the skymeter reading is 15.0 at the zenith due to the > half moon that is just past zenith. Pointing the skymeter towards Ursa Major the reading is a much more respectable 18.0.

Messier 101, NGC 5457, in Ursa Major is 21 million light years from earth. The face-on spiral galaxy is estimated to contain 1 trillion stars! Started imaging M-101 and got 5 x 120 second frames in and stacked in AstroToaster, looking pretty good. Then the camera / computer dropped the next 10 frames - ARGH !!

The image adjustments in AstroToaster are pretty good but I have to learn the interactions of the controls. Also I need more frames to bring out the detail in the arms. The object is getting too far to the west and into the higher light pollution region of my skies. So further frames will have to wait for another observing session. Shutting down at 0050.

April 8, 2017
Came out at 2100 to a beautiful night. Clear with no star twinkle, but a full moon sitting high in the sky. The temp is 63.3 F with 71% humidity and a dew point of 54 F. A slight occasional breeze. I set up the camera the same as last night: at prime focus, Lumicon DS filter, and gain = 400. I'll stick to -10 C on the camera cooler to hopefully avoid the textile pattern I saw at – 20 C. I still have the camera on a USB 3.0 cable direct to the laptop and the autoguider in the hub of the ASI071MC-COOL.
Cooled the camera down to 0 and held for 10 + minutes. Found the mount was parked slightly East in RA, so I had to reset counterweight down and now I'll have to rebuild the model; Arturus, Spica, Mizar, Denebola, Vindemiatrix, Castor, Capella, and Alphard.

I started out pretty good with the fast 8 sec frames while building the model, but when I went to 60 s frames the time to download got longer and I started dropping frames. I changed from RAW16 to RAW8 but it froze the SharpCap program. After several minutes of the program not responding, I killed it and restarted. Resuming my Herschel 400 project.

H 34-1, NGC 5248
Found that an exposure of 90 sec gave a maximum on the histogram at 40%. A little high but I'll go with it. I got 6 frames stacked, but dropped 4 so far. Seems like it gets into a mode of dropping frames, now I'm at 6 good frames & 8 dropped, so I've dropped the last 4 frames in a row. Finally got 19 good frames on this object.

This object is a face on spiral galaxy with a prominent arm on the N trailing back to the W and another arm on the S trailing back to the E. Apparent size is ~ 3 x 1.5 ', I'm missing the outer arms in my images. There are hints of inner tighter arms around the center. The center is not overly bright and elliptical running NW to SE. The galaxy is in a nice star field of 19 similar magnitude and size stars and many other fainter ones.

H 9-6, NGC 5466, Melotte 124
Went to NGC5466, a GC in Bootes. Set the exposure to 90 sec which gave a histogram curve maxima of around 27%. The images are very washed out due to the full moon.  The camera is still running at a gain of 400 and the chip temperature is -10 C.

This is a loose GC about 10 ' in diameter. The GC is roughly circular with a linear string of 5 stars on the NE corner. The star field is relatively sparse with no large or bright stars in the FOV. The GC is not saturated in the core. Many individual stars are seen.
I've cropped off the bottom 10% of the image due to amp glow.  Use of dark frames will eliminate that but for now this camera provides such nice fields, a little can be sacrificed without harming the image.

At 0004 it is 54 F and 88% humidity. The skymeter reading was 17.08 with the full moon near the meridian.

H 99-1, NGC 5557
This is a small (2.4 x 1.9 arcmin) galaxy in the constellation Bootes.  It is 132,700,000 light years from earth.  At 2 min exp yielded a light curve peak @ 31%. The galaxy is quite small at 2.4 x 1.9 ' but zoomed in my image is similar to that from the Deep Sky Survey (DSS). I captured 11 frames and then I stopped.

This is a small face on galaxy with a bright core that is slightly elliptical, while the visible halo is nearly circular. The diameter of the halo is roughly 3 core diameters. There is a bright star in the halo at the ESE position. The star field contains several bright stars that are nearly as big and bright as the galaxy's core. 

H 189-1, NGC 5676
NGC5676 will be the last target for the night. A 2 min exposure put the apex of the light curve at ~ 28%. I note that the bottom of each image contains a bright streak across the frame. Not sure if this is amp glow or what. I got 7 frames and it dropped 3 – ARGH !

A spiral galaxy inclined about 45 degrees and tilted towards the earth at a shallower angle. It is rather small. The core is barely more luminous than the halo. No discernible features from the halo. The galaxy is in a nicely populated star field with 50 or more stars. Two stars are rather large, at least larger than than the galaxy center.

I noted that the guiding graphs look terrible but the images are reasonable. I need to work on the polar alignment , balance and other causes of bad tracking. I shutdown for the night at 0204. Note the camera ran all night at -10 with no perceptible freezing of the sensor.  

April 14,2017

I returned the ASI071MC-COOL under warranty for replacement. There have been at least 2 other reports of similar issues on the ZWO forum.   ZWO is recommending people clean the sensor with alcohol, but I declined in favor of a replacement. Hoping the replacement will be here in time for the Deep South Spring Scrimmage. In the interim, if it ever clears up, I'll use my Mallincam.

April 20, 2017
Received my replacement camera today.  Came out a little after 8 on a clear, warm night. Setup the ASI071MC-COOL at prime focus with the Lumicon DS filter. Have the camera on a USB 3.0 cable direct to the laptop and the autoguider in the hub of the ASI071MC-COOL. Setup SharpCap for RAW16 color space with FITs files, no binning. Cooled the camera to 10 C and turned on the dew heater. After 20 min turned the cooler down to 0 C and then down to -10 and finally -20.  The camera got to -19 C but that's as cold as it could go.

H 186-1, NGC 5195, Messier 51b
Got a nice image of the whirlpool galaxy (NGC 5194, Messier 51a) and its companion, the smaller NGC 5195.   This galaxy is 25 million light years from earth in the constellation Canes Venatici.   Used  AstroToaster to live stack and adjust the images.  AstroToaster appears to be a better stacking program than SharpCap and it has, IMHO, better image adjustment tools.  The image is 11 x 120 seconds at gain = 400 with no dark frame subtraction.  

I did adjust the levels to brighten the image and improve contrast in GIMP 2.8.22.  

Messier 13, NGC 6205
Went to M13 and caught some nice images of The Great Globular Cluster in the constellation Hercules.  The image is 12 x 90 sec exposures at gain 350 and no dark subtraction.   The camera was running at -15 C.

Messier 57, NGC 6720
A little after 0200 I went to M57 (the ring nebula) and started to capture images and the image looked foggy with a center circle that was darker. I suspect this was from extended operation of the cooler at near 100%. I turned off the cooler until the chip reached near ambient (15 C) and then turned the cooler on again to 0C. After a few minutes I lowered it to -10 C. After a few images the dark circle reappeared at -10 C.  Captured images of the ring with AGC 400 & 3 min exposures. I noticed star trailing and the PhD graphs showed some big spikes in RA, both + & - . Image shift is severe at this point. Not sure what's happening. The mount is not giving any errors.

Interesting the image is black & white as it had color in SharpCap.  Shut down at 0303, will look at this tomorrow.
April 24, 2017

Came out a little after 2000 on a cool (for late April) and relatively dry night. Setup the ASI071MC-COOL at prime focus with the Lumicon DS filter. Have the camera on a USB 3.0 cable direct to the laptop and the autoguider in the hub of the ASI071MC-COOL. Setup SharCap for RAW16 colour space with FITs files, no binning. Gain set at 300 tonight to start. I want to experiment with different gains to determine the impact on the light curve & noise. Cooled the camera to 10 C and turned on the dew heater. After 20 min turned the cooler down to 0 C.

At the end of last session I experienced some significant drift that overwhelmed the guider. I wonder if the mount slipped on the azmituh or altitude locks. Will check that first. Went to Alphard in Hydra. Started drift and after 10 min there is drift up but nothing left or right. I'll take that as a good sign and move to a star in the East. Went to Zubeneschamali (Zubenesch) in Libra just above the E horizon. After 5 min there is drift downward ~ ½ star diameter, but not left or right. From what I've read about drift alignment, up & down drift is not a concern. Seems it should be but I'll have to read more on this later. For now I'll get started observing.
I checked the focus with SharpCap's Bahtinov mask tool. It is quite nice and helpful. Focus achieved at 34.5 mm.

On NGC 5689 a 2 min exposure at 300 gain yielded a light max of ~ 2%. A 3 min exposure yielded an ~ 7 % max.  Took a few more to populate the below table.

exposure time
light curve max (%)

Other than the first table entry we see that increasing gain by 50 will increase the  light curve maximum by approximately 50%.  Increasing the exposure from 2 to 3 min (a 50% increase) increases the light curve maximum by a variable amount (250%,  75%, & 46%).  I should have captured the amplitude of the light curve at maxima, but failed to do that on all the tests.  Something to try another time, but this provides some insight into the system's response to varying exposure and gain.

At 2225 it is 58 F with 96% humidity and no wind. Sky meter reading is 18.99.

H 188-1, NGC 5689

A small faint (mag 11.9) galaxy in the constellation Bootes that is angled away from the earth.  It is approximately 116 million light years from earth.  The core is large and bright but no details are visible in the halo.  The star field is pretty well populated and there are 3 other galaxies in the FOV; NGC 5682 (mag 13.9), NGC 5683 (mag 14.8), and NGC 5693 (mag 13.6).  The image is 9 x 180 seconds at a gain of 400 gain.  The amp glow along the bottom of the frame is evidence that no dark subtraction was employed.

 H 195-1, NGC 4111 
The camera cooling is holding steady at -10 C with no visible artifacts in the images and at 19% power.  The object is a near edge on galaxy with a bright core in the constellation Canes Venatici.  The halo is approx 3 core diameters in radius and is oriented NW to SE.  No detail is visible in the halo.  There is a bright, large star to the SW of the galaxy.  There are 3 other galaxies in the FOV. Two are SW of NGC 4111; NGC  4117 (mag 13.4)  and 4118 (mag 16.0).   NGC 4109 (mag 13.3) is  NE of NGC 4111.  The image is 6 x 180 seconds at gain 400.  

H 701-2, NGC 6207
A small faint galaxy with a smallish core that is rather dim.   There is no detail evident in the halo.  The halo radius on the thin side is about 1 core diameter.  In the long direction it is 3-4 core diameters.  The galaxy is in a well populated star field.  There is a large star just off the FOV to the E.  The DSS image shows more of a molted appearance, but I don't see that in my image, which is 6 x 180 seconds at gain = 400.

At 0046 the temp is 57 F with 96% humidity and a sky meter reading of 18.99

H 759-2, NGC 5907
This will be the last target of the night. Still gain 400. PhD started giving me warnings about max RA duration is preventing PhD from making corrections. Not sure what caused this, likely the part of the sky I'm pointed at. Images have significant star trails. To complicate troubleshooting, the camera / SharpCap is posting partial images. The trailing stopped after a couple of minutes without any intervention by me. Not sure what to make of it. The stars are now nicely shaped starting in image # 4.   I noticed in image 3 of NGC 5907, the image has a dark circle like dew on the sensor. Raised the temp to 0 and then to 5 C.  This dew issue continues to plague me.

A large edge on galaxy in the constellation Draco.  The galaxy is oriented NW to SE.  The core is barely brighter than the surrounding halo.  The star field is nicely populated with many similar size & brightness stars.  The image is 7 x 180 seconds at gain = 400.

Shut down at 0145.

April 25, 2017
Around 10 am I installed the auxillary desicant tabs in the ASI071MC-COOL. Hopefully this will avoid the dark circle in the images like I experienced late last night.

Came out a little after 9 pm on another coolish (66 F, 90% humidity) clear night with a light breeze. Created a new PhD dark library for 3 – 6 seconds with 10 exposures each. Hopefully this will help reduce the noise and improve the S/N on the guide stars. And it did, I went from a S/N of 12 to 46 with the new darks.

Took a new series of darks on the ASI071MC-COOL at 180 sec & gain 400 @ -10 C as RAW16 FITS. Hopefully it will eliminate the glow along the bottom of the frame.

H 42-4, NGC 4631, Caldwel 32, "the Whale & Pup (NGC 4627)
The guiding is poor – swinging from -2 to +2” on both axis with occasional larger swings in RA. I saw this last night when the scope was pointing near the zenith. I'm not getting any Gemini errors but perhaps I'm not sufficiently balanced. The tracking settled down and I took 10 images of 180 sec each and stacked at gain= 400.  The dark subtraction did help to remove/reduce amp glow.

An edge on galaxy in the constellation Canes Venatici that is thicker on the S end than the N.  There is no discernable central core but there is a brighter region just to the S and W of the center of the visible galaxy.  The galaxy is oriented NNE to SSW.  Also visible in the FOV is a companion galaxy (NGC 4627, "the pup").  It is a small roughly circular galaxy located just W of the center of NGC 4631.  These galaxies are located in a nice star field with a loose grouping of over a dozen bright stars to the WE of NGC 4631.  
Cooler is holding -10 C well at 22% power. No artifacts noted on the images thus far.   At 2340 it is 61 F with 94% humidity and a sky meter reading of 18.92.

H 40-6, NGC 6171, Messier 107
I wasn't able to get any of the targets around the N pole, so I moved back to the E to NGC 6171 in the constellation Ophiuchus.  I found it easily and cooled the camera back down to -10 and I got the circle back !!!.  Had more difficulty guiding with wild RA swings. I had recalibrated PhD before this. Not sure what is causing this, but it is screwing up lots of images!

After a few minutes the tracking settled down somewhat (I didn't do anything) and I was able to capture eight images of NGC 6171 with nice round stars. The computer dropped a few frames which prolonged the process and raised the aggravation level.

Note on this GC (NGC 6171) a 3 min exposure with gain = 400 yielded a light curve with the max at just under 20%. So even with reasonably bright (mag 7.8) objects it takes ~ 3 min exposure to capture. Dimmer objects like nebula will likely require me to take longer exposures.

This is a nice GC in a rich star field.   The core of the cluster has many discrete stars visible in a roughly circular grouping.  On the N side of the GC  there is a line of stars running NE to W.  There are 5 larger brighter stars in this FOV.

Shutdown at 0156.

April 30, 2017

Came out at 2330 on a windy night after a stormy day. Clouds are clearing but still prevalent. Checked scope balance and found it fine in RA & Dec. I did find the W azimuth lock blot a bit lose and tightened it. Not sure if that accounts for the poor tracking when the scope is near zenith.   I'm using the ASI071MC-COOL at prime focus with the Lumicon Deep Sky filter + a Badder UV/IR cut filter. This is my first time using the UV/IR filter on this camera.

I captured a few images of the Ring nebula (M 57).   Images are 180 sec, gain 400, -10 C, dark frame subtracted in SharpCap. Intermittent clouds are disrupting some images & affecting the guiding. I'm noting a small dark circle near the bottom of the image that I haven't seen before and also an arc to its NW. I suspect these may be from the UV/IR filter.  Focus looks a bit off.   Certainly not my best image of this iconic object.

Sky meter reading @ 0232 = 19.10, 59 F, 83% humidity, with only light breeze now. Most of the clouds have cleared except for some low in the east.

I dropped 3 images out of 10 taken on M57, very frustrating! I hate to spend the money on a laptop, but that may be the only solution. Also the histogram colors were not well centered with red to the left of the white and green & blue to the right.

It is after 0230 and the mosquitoes are irritating me, so I'm shutting down.

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