My new LX600 may need glasses; it may have astigmatism
Posted: 25 May 2016
Following the nearly three hours worth of unsuccessful telescope collimation attempts on the previous session, I had some email discussions with Dr. Clay Sherrod of Arkansas Sky Observatories on Tuesday, 24 May 2016, about my 12" LX600 collimation woes. He quickly responded with some things to try, which I would do on the next session. (I have known Dr. Clay, as he is known, since the late 1990s. Along with Dick Seymour, he was a contributor to my book "Using the Meade ETX", first published in 2001.)
Open: Tuesday, 24 May 2016, 1819 MST
Conditions: Clear, breezy
While waiting for sunset I reconfirmed what steps I wanted to take in order to try collimating the 12" LX600 telescope. I also confirmed what stars I would use for collimating.
1924 MST: sunset. LX600 ON, StarLock OFF.
Slewed to the star Spica (Magnitude +1) and began the collimation work. As I was alone this night I started by using the star diagonal for convenience. I first used the 9mm eyepiece (271X). Per a suggestion from Dr. Clay, I tightened all three collimation screws a slight amount. By this point the breezes had calmed down, making collimating easier (or so I hoped).
As I was trying to do the collimation I kept noticing that if I could get an apparent good collimation on one side of in-focus, the collimation would be bad on the other side of in-focus. I then focused Spica using the Bahtinov Mask. Slewed to Jupiter; view not good. Jupiter was "fuzzy" at the limbs and the three visible moons appeared elongated. I tried doing some collimation adjustments while viewing Jupiter in an attempt to remove the "fuzziness". I got the view slightly better but still not good.
Returned to Spica for more adjustments. I removed the diagonal to remove it from the optical path. Did some more tweaks, then viewed the diffraction pattern at 443X. Collimation actually looked pretty good.
2052 MST: took a short break and saw the Zodiacal Light in the western sky.
Returned to Jupiter and checked it at 102X, 271X, and 443X. Moons were still elongated.
Slewed to the star Syrma (Magnitude +4) and viewed it using 542X. I could get an apparent good collimation on one side of focus, but not on both sides.
2118 MST: viewed Mars, 102X, 271X, and 542X. A dark area was visible but the view was not crisp. Viewed Jupiter again at all three magnifications. Four moons were now visible and a shadow of one in transit was visible using 271X but not 542X. The moons were still elongated and changed from "--" to "|" as I focused the image. Rats.
Returned to Spica. Mounted the DSLR at prime focus (no diagonal). I used the Nikon iOS app "WMU" on my iPhone to view the DSLR live view over Wi-Fi. I could see the diffraction rings of the out-of-focus star but I could still not get a good collimation.
I did some final collimation tweaks (without the iPhone) and then viewed Jupiter. The views were better now at 271X and 542X. The moons were less elongated and the shadow was now visible using 542X. Then viewed Mars, then Saturn. The views were slightly better. There was some "ghosting" along the limb of Mars, which changed direction depending on the focus. I could see Cassini Division in Saturn's ring, but it was still not a sharp view. I then viewed M13 (globular cluster), 102X. The view wasn't horrible, but I could not tell visually how good it was.
I remounted the camera and used the star Vega for these collimation photos, 1/30sec, ISO 3200:
I then did a focus test exposure using the Bahtinov Mask, 1 sec, ISO 6400:
This is a 10 second, ISO 6400, image of M13:
Argh, the stars are doubled, as seen in the magnified inset.
I then slewed to Spica and rechecked if the focus had changed by using the Bahtinov Mask. It had, as seen in this photo:
The focus is not supposed to change with the LX600 telescope as it is slewed. Could there be some mechanical problem with the mirror mountings?
I decided to end for the night and report the findings to Dr. Clay.
Close: Tuesday, 24 May 2016, 2310 MST
Session Length: 4h 51m|
Dr. Clay gave me some more tests to try, some of which I would be able to do during the day on Wednesday. The others would have to wait until Wednesday night.
Comments are welcome using Email. Twitter users can use the button below to tweet this report to your followers. Thanks.
Copyright ©2016 Michael L. Weasner / firstname.lastname@example.org
URL = http://www.weasner.com/co/Reports/2016/05/25/index.html