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Early Christmas (Meade 178ED)

Started by klawson, 11/23/2005 12:02PM
Posted 11/23/2005 12:02PM Opening Post
I just got a Meade 178 ED a couple of days ago. I have had many refractors over the years but this was my first APO! What a beautiful beast smile Put everything together on the evening of the 21st. First light revealed the dreaded comatic star image in the center of the field of view in a medium power eyepiece (160x). I had made sure the lens and focuser were aligned earlier so this was not the problem. I had seen this in other refractors before. Looks like the lens elements had shifted during rough shipment. Crap :C Well..... I dreaded a trip to Meade (wait, wait, wait) and did not want to return the instrument after finally finding one in excellent shape. After getting over my initial dissapointment I found a way to fix it and I'm now having a ball. Second light was a blast. Textbook star images 8) Mars was "off the hook" at 320x grin The tiny polar cap was easily visable during moments of steady seeing. This 50 year old man was laughing like a little kid on a new bike!

I found that the collimatable lens cell has a collimation setup for the second element. It's tricky to use but it works. It's a lot like trying to collimate a Chromacor which can be a pain but this took me about 20 minutes using my daytime artificial star. Last nights tests confirmed about a 1/6th to 1/7th wave overall correction (ronchi[250 line grating] & star test). I pushed the instrument to 426x (Antares 7.5 & barlow)and the image remained crisp and well detailed. Not bad at all grin I'm glad I was able to fix it "in house". My question is: Has anyone else had the same expererience?

Keith

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Posted 11/23/2005 02:27PM #1
I had the same experience with my 127ED. I sent it back to Meade twice before realizing they couldn't fixt it. At first, I didn't understand the nature of the problem but some surfing on the web revealed information from a guy in Maryland with the diagnosis and the process for fixing it. It took me longer - about two hours - before I centered the rear element accurately. After that, the performance was very good - better than the price would lead you to believe. The ultimate problem, however, was the centering would not "hold". Every time I transported the scope to a dark site, which I do a lot, it would shift out of center. Eventually I decided the effort of recentering at the start of most observing sessions wasn't worth the effort. One of the reasons I like refractors they require a minimum of maintenance. After several years, I sold the scope to someone who wanted to use it in a backyard observatory (no regular transportation) - he really likes it.
Posted 11/24/2005 02:47PM #2
Keith Lawson said:

I just got a Meade 178 ED a couple of days ago. I have had many refractors over the years but this was my first APO! What a beautiful beast smile Put everything together on the evening of the 21st. First light revealed the dreaded comatic star image in the center of the field of view in a medium power eyepiece (160x). I had made sure the lens and focuser were aligned earlier so this was not the problem. I had seen this in other refractors before. Looks like the lens elements had shifted during rough shipment. Crap :C Well..... I dreaded a trip to Meade (wait, wait, wait) and did not want to return the instrument after finally finding one in excellent shape. After getting over my initial dissapointment I found a way to fix it and I'm now having a ball. Second light was a blast. Textbook star images 8) Mars was "off the hook" at 320x grin The tiny polar cap was easily visable during moments of steady seeing. This 50 year old man was laughing like a little kid on a new bike!

I found that the collimatable lens cell has a collimation setup for the second element. It's tricky to use but it works. It's a lot like trying to collimate a Chromacor which can be a pain but this took me about 20 minutes using my daytime artificial star. Last nights tests confirmed about a 1/6th to 1/7th wave overall correction (ronchi[250 line grating] & star test). I pushed the instrument to 426x (Antares 7.5 & barlow)and the image remained crisp and well detailed. Not bad at all grin I'm glad I was able to fix it "in house". My question is: Has anyone else had the same expererience?

Keith

You bet i had the same experereience!

I bought a 7" Meade ED back in 1999, went back to Meade 3 times, and was always out of collimation. Got my money back and looked back!

Chas