This scope is not giving me satisfactory views and I believe it is not collimated correctly. When I defocus a star the concentric circles are not round but rather bunched up on one side of the out of focus star. I believe the three sets of screws on the objective cell is what I use to make adjustments but I am not sure. Do I use an allan wrench to loosen these adjustments ??? I don't want to mess around with these if that is not what they are for. Also, can one use sight tubes or a laser to make collomations? I hope someone can help me on this one. Thanks
Collimating a Meade 102 Ed refractor
Started by scopeking, 03/15/2007 02:30AM
Posted 03/15/2007 02:30AM
Opening Post
Posted 03/15/2007 04:57AM
#1
John,
Rolondo is right, you do need to be very careful and probably shouldn't even attempt this.
When my 102ED came from the Meade factory it was perfectly collimated however my first trip taking it on a washboard road to a dark sky site bounced it out of alignment.
I experimented, slowly and carefully, with the push pull screws on the front of the lens cell and that helped a bit but eventually the concentric rings seemed to just migrate around without ever centering perfectly.
I found that there are three additional holes on the side of the lens cell. Each hole has two allen screws nested inside (6 screws total). These screws actually center one of the two elements in front of the other. Now I suggest you not do this... but I removed the outer screws and made a few tiny turns on the inside screws while viewing a focused star at very high power. I'm talking "tiny" fractions of turns. I made sure to loosen an opposite screw so not to bind and accidentally crack a lens. As I remember one of these inner screws had worked its way out quite a bit and it turned easily for quite a ways before meeting any resistance.
It took about a half an hour but I did get my nice tight airy disks back. I replaced the outer allen screws (I think these function to retain the position of the inner screws) and haven't had an alignment problem since. This was more than a year ago and lots of desert washboard roads.
J.
Rolondo is right, you do need to be very careful and probably shouldn't even attempt this.
When my 102ED came from the Meade factory it was perfectly collimated however my first trip taking it on a washboard road to a dark sky site bounced it out of alignment.
I experimented, slowly and carefully, with the push pull screws on the front of the lens cell and that helped a bit but eventually the concentric rings seemed to just migrate around without ever centering perfectly.
I found that there are three additional holes on the side of the lens cell. Each hole has two allen screws nested inside (6 screws total). These screws actually center one of the two elements in front of the other. Now I suggest you not do this... but I removed the outer screws and made a few tiny turns on the inside screws while viewing a focused star at very high power. I'm talking "tiny" fractions of turns. I made sure to loosen an opposite screw so not to bind and accidentally crack a lens. As I remember one of these inner screws had worked its way out quite a bit and it turned easily for quite a ways before meeting any resistance.
It took about a half an hour but I did get my nice tight airy disks back. I replaced the outer allen screws (I think these function to retain the position of the inner screws) and haven't had an alignment problem since. This was more than a year ago and lots of desert washboard roads.
J.
Posted 03/15/2007 07:08PM
#2
There is a Y**** group for these and other Meade ED refractors. There are very good instructions in the file area there on how to do the collimation. Diagrams of the lens cell along with the location of the screws.
Just remember that the main culprit with these is lens decentering, not just collimation within the OTA. The individual lenses have to be centered pretty accurately with regard to each other (laterally). Because of the steep curves the lens design uses, lens decentering has a quick and detrimental effect. The newer lens cells have these adjustments.
I had a Meade 127ED a couple of years ago. I fiddled with it using those instructions and was able to return it back to collimation easily. It arrived in collimation from the seller here on Astromart, but I couldnt leave well enough alone. After a couple of times it was effortless.
However, if after reading the instructions there and you dont feel comfortable or if it is a recent purchase from Meade, then send it back. But, having owned one before I will tell you that it isnt hard to do and after a few tries it becomes second nature.
Good luck.
Just remember that the main culprit with these is lens decentering, not just collimation within the OTA. The individual lenses have to be centered pretty accurately with regard to each other (laterally). Because of the steep curves the lens design uses, lens decentering has a quick and detrimental effect. The newer lens cells have these adjustments.
I had a Meade 127ED a couple of years ago. I fiddled with it using those instructions and was able to return it back to collimation easily. It arrived in collimation from the seller here on Astromart, but I couldnt leave well enough alone. After a couple of times it was effortless.
However, if after reading the instructions there and you dont feel comfortable or if it is a recent purchase from Meade, then send it back. But, having owned one before I will tell you that it isnt hard to do and after a few tries it becomes second nature.
Good luck.
Funding Member
