More frustration

In reference to last night's session, turning off auto-contrast and setting contrasts to the extremes did not work. The bright/hot pixels still leak through. I was not that careful aligning the polar axis thus the bright/hot pixel trails are still present. One different thing I did try was checking the sharp instead of soft setting in the color dialog. This substantially sharpened the star images but also increases noise and probably lowers sensitivity. See M13 below.

M13

I'm in Maryland but will return to Massachusetts tomorrow. Weather forecast suggests I won't have another opportunity until Wednesday earliest. I'll try to do a much better alignment and image then.

Some frustration

In the United States Northeast I don't get a lot of clear nights out. And, for the few I get transparency ain't that great. Since my early successes with the DSI things have not gone well. I get the camera temperature stabilized, collect dark frames and start imaging. Here's the problem. Dark frame subtraction seems never to get rid of the big permanent pixels. This manifests itself as colored streaks such as those in the image of M-13 below.

This had not been a problem with the DSI when I first started using it. I wondered if scope alignment was the big issue. I don't have a permanent location. When in Massachusetts I take the scope to a local park, set up and align, set up the camera and shoot. In Maryland, I use the back yard but have to do an alignment each time. I don't think my aligning is so much better than earlier times to make a difference.

Recently I found this this webpage where the author mentions the contrast control. I hooked up the DSI and it dawned on me that instead of leaving it with auto-contrast checked I should try setting the contrast to 0 and its maximum 65536. With this setting the bright pixels vanish. On my next night out I'll try this setting to see if the problems clear. Fingers crossed. 

It's been a good two years since I posted here. I'm ashamed to  admit I forgot I created the blog. That's not to say I have abandoned the DSI-II. For some reason I no longer remember I stopped posting. Time to give it a renewed try. For the near future posts will catch up on past activities.

Meade no longer produces the DSI-II. There was a DSI-III which has been discontinued along with the full DSI line. In fact I was "lucky" to grab mine for a substantial discount as Meade was closing out the IIs. I put lucky in quotes because the DSI-II is a mixed blessing. It was cheap $290. It does work as you can see from the earlier images.

With its automatic dark frame subtraction it is easy to use. On the other hand the product is really poorly documented and the software interface is poorly designed. Meade left it to an enthusiast to create a video tutorial that is not done under the dark but none the less is more informative than the included documentation. The documentation does little to explain how to use the various settings or what many of them mean. This has been a recent pattern with Meade. The documentation for its Autostar

Whoever coded the software interface did not account for varying screen resolution. Thus the user must futz around with screen resolution settings on a high resolution laptop just to get a usable screen. The lack of temperature regulation is another source of frustration on nights when temperatures constantly change. One is forced to keep generating new sets of dark frames as the device cools along with the night air. A few users have modded their DSI-II with Peltier cooling. I'm not yet brave enough to try that.

Under a full moon

June 16 was just one day past full moon. Between 10 and 11PM the moon was still low to the southeast which offered a test for using the DSI-2 under fairly adverse conditions. Randolph, MA where I live is already very light polluted with poorly shielded sodium vapor lights. Adding to the challenge, the  local elementary school in whose parking lot I do my local observing has both broadband mercury vapor along with sodium vapor lighting.

Messier 3 just past full moon

After setting up the scope it took longer than usual to iterative align the 127ED because I forgot about the problems posed by using Arcturus or Spica as alignment stars. I need to recompile a list of compatible alignment stars which which differ between 3 and 9 hr away from Polaris in R.A.


I chose M3, which rides high in the sky this time of night to image. The globular cluster was obvious at 1s exposures in focus mode. After  creating a fresh set of darks for the night and merging with my old set of darks I acquired two sets of exposures at 2.8 and 4.0s. The 4.0s set were averaged to produce the final image after some histogram, brightness and contrast tweaking.

A few nights in Maryland Part 2

Below is my first DSI-2 image of a galaxy Messier 51. M51 is near the end of the handle of the Big Dipper. As luck would have it a member of the Meade DSI Yahoo discussion group, Bill Rouse announced there is a new supernova or exploding star in M51 also supplying a link to before and after images. I didn't get a chance to image the galaxy until June 8th. Again I did not keep good exposure records. The red arrow in the post processed image points to the exploding star. Exposure was unguided which helps explains the oval shapes of the stars.

A few nights in Maryland Part 1

M3

I was in Frederick, MD for a week with the scope which afforded me couple of opportunities for  a little more DSI-2 imaging. The moon was between a young crescent and first quarter. I like to keep different night sessions separate by creating a date named folder.

It dawned on me to bundle dark frames in a single archive and copy it to the new folder for each night of imaging. This improves the odds of the Envisage software finding a compatible set of dark frames for the current session. Dark frames are coded for temperature and Envisage complains for more dark frames  if the temperature changes significantly.

M13

Only one night offered half decent transparency. On the first night with any transparency 6/6/11 I managed  bag four  globular clusters i.e., M3, M5, M13 and M53. Because, I'm still in the familiarization mode my record keeping for these was poor. The images appear to the below.

In my next DSO imaging round I will try imaging without the mirror diagonal on the hope it will improve the roundness of the stars. The DSI-2 also offers  options to sharpening during imaging. However, according to Meade you give up some sensitivity

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  M5

M53

Periodic Error Correction.

Sunday night I thought I would attempt to train the drive for periodic error correction or PEC.  It took longer than usual to get the drive aligned tonight. I suspect because I dumbly sync-ed Polaris after each drive Azimuth/Altitude(tilt) adjustment. It was unusually humid and transparency was mediocre. As one might expect clouds moved  in ending the night.

It dawned on me that I should simply clear any PEC data that might be polluting the drive and causing it to correct for non-existent errors. Tonight I bring the scope upstairs and retrain the RA/DEC axes. This is different from PEC training. If I get a break on the sky I'll try imaging one easy DSO. There are few visible from my tree obstructed terrace between 9-12 midnight. This weather is really sucking right now.