mirror shift

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shoelevy
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Post by shoelevy »

ok
well besides the crayford focuser, if there another cheaper solution?
or do you guys have a method to actually fix the mirror shift itself
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shoelevy
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Joined: Mon Apr 26, 2004 9:03 pm
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Post by shoelevy »

ok
well besides the crayford focuser, is there another cheaper solution?
or do you guys have a method to actually fix the mirror shift itself
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VinSnr
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Post by VinSnr »

shoelevy wrote:ok
well besides the crayford focuser, is there another cheaper solution?
or do you guys have a method to actually fix the mirror shift itself
Yes there is.....but I am hesitating to tell you.

There are two reasons why there is mirror shift

1) Grease not evenly distributed.
2) Pin at the Primary mirror was not engaged properly.

The most common reason is (1)

For (2), you have to open up the focuser. I am hesitating to tell you because I wouldn't want you to do that. If you don't know how to do it well, you might make it worse.

There is a pin at the back of the primary mirror cell. When you turn the focuser, you are actually pushing or pulling this pin. If the focuser end is not engaging this pin properly, you will have a problem with large image shift.

Now when u turn the focuser, is it tight or smooth? Celestron's focuser is normally very smooth....to the extend I find it too loose. If you find it tight, then there must be some binding somewhere.

However, if your image shift is so large, how on earth did you get your object focus in the first place?
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VinSnr
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Post by VinSnr »

shoelevy wrote:ok
well besides the crayford focuser, is there another cheaper solution?
or do you guys have a method to actually fix the mirror shift itself
No....the other cheaper solution is to open up the focuser and check teh focusing mechanism. Please do not do this. If you do, you will void your warranty

Just get a crayford and live with it. Next time, try not to buy new. Get a used and proven one and you won't have this problem.
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shoelevy
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Post by shoelevy »

yeah..for tele maybe i should get used one but accessories wise, i'll still get new ones
hehe
actually, i've contacted astro sci and turns out if i get it fixed there i'll still save over $600 so i'm contented
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VinSnr
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Post by VinSnr »

shoelevy wrote:yeah..for tele maybe i should get used one but accessories wise, i'll still get new ones
hehe
actually, i've contacted astro sci and turns out if i get it fixed there i'll still save over $600 so i'm contented
how much they charging u for fixing this??
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shoelevy
Posts: 352
Joined: Mon Apr 26, 2004 9:03 pm
Location: Singapore

Post by shoelevy »

VinSnr wrote:
shoelevy wrote:ok
well besides the crayford focuser, is there another cheaper solution?
or do you guys have a method to actually fix the mirror shift itself
Yes there is.....but I am hesitating to tell you.

There are two reasons why there is mirror shift

1) Grease not evenly distributed.
2) Pin at the Primary mirror was not engaged properly.

The most common reason is (1)

For (2), you have to open up the focuser. I am hesitating to tell you because I wouldn't want you to do that. If you don't know how to do it well, you might make it worse.

There is a pin at the back of the primary mirror cell. When you turn the focuser, you are actually pushing or pulling this pin. If the focuser end is not engaging this pin properly, you will have a problem with large image shift.

Now when u turn the focuser, is it tight or smooth? Celestron's focuser is normally very smooth....to the extend I find it too loose. If you find it tight, then there must be some binding somewhere.

However, if your image shift is so large, how on earth did you get your object focus in the first place?
wah...i have no idea how i missed this message of yours.haha
ok...for 1) i tried moving the mirror up and down to redistribute the lubricant but it isn't working.
and regarding the focuser, it's VERY tight. unlike my c5. it feels like sharpening a pencil with a blunt sharpener

i don't know how i got my object in focus...i just did
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shoelevy
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Post by shoelevy »

one other thing...if i use the crayford focus right...is it true that i have to lock the primary mirror?
if so how do i do it?
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VinSnr
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Post by VinSnr »

shoelevy wrote:
VinSnr wrote:
shoelevy wrote:ok
well besides the crayford focuser, is there another cheaper solution?
or do you guys have a method to actually fix the mirror shift itself
Yes there is.....but I am hesitating to tell you.

There are two reasons why there is mirror shift

1) Grease not evenly distributed.
2) Pin at the Primary mirror was not engaged properly.

The most common reason is (1)

For (2), you have to open up the focuser. I am hesitating to tell you because I wouldn't want you to do that. If you don't know how to do it well, you might make it worse.

There is a pin at the back of the primary mirror cell. When you turn the focuser, you are actually pushing or pulling this pin. If the focuser end is not engaging this pin properly, you will have a problem with large image shift.

Now when u turn the focuser, is it tight or smooth? Celestron's focuser is normally very smooth....to the extend I find it too loose. If you find it tight, then there must be some binding somewhere.

However, if your image shift is so large, how on earth did you get your object focus in the first place?
wah...i have no idea how i missed this message of yours.haha
ok...for 1) i tried moving the mirror up and down to redistribute the lubricant but it isn't working.
and regarding the focuser, it's VERY tight. unlike my c5. it feels like sharpening a pencil with a blunt sharpener

i don't know how i got my object in focus...i just did
As I suspected, something must be binding in your focuser. If it is that tight, I believe the pin was not engage correctly.

You see, the focuser end has a hole. That hole is for the pin. To insert the focuser in such a way that the pin sitted nicely into that hole require some effort. Someone must have force the focuser in before the pin could be sitted correctly.

Tell me this......how many hex screws can you see on your focuser? These screws tie your focuser onto the OTA. Tell me how many screws are there. If possible, take picture and show me the focuser front with the hex screws.
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VinSnr
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Post by VinSnr »

shoelevy wrote:one other thing...if i use the crayford focus right...is it true that i have to lock the primary mirror?
if so how do i do it?
There is no need to lock. Just move your primary all the way to the back of the tube and leave the stock focuser alone.

The only scopes that can lock the primary are the LX200 GPS series.
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