Sorry if this has already been covered... I couldn't find it.
My 6se is still in collimation, but I'm sure it's only matter of time. Since I've never tackled it or even seen it done I figure when it's time, I will curl up in a ball and wet my pants. But for now I think I'll just find someone who knows what they're doing and ask for help.
I am however, even now considering Bob's Knobs as an alternative to the factory screws. Can anyone tell me if this is a good idea?
Bob's Knobs
Started by
Bill45
, Feb 11 2010 12:42 AM
16 replies to this topic
#2
coopfore1
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Vostok 1
Posted 11 February 2010 - 12:51 AM
Yes, bobs knobs are an excellent idea.....
#3
Tel
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Voyager 1
Posted 11 February 2010 - 04:06 AM
Hi Bill,
Bob's Knobs are indeed a great convenience which allow one hand to reach around the front of the OTA to make adjustments while viewing and their use also has the added bonus of removing the potential hazard of wielding a screw driver or Allen key (wrench) in the vicinity of the corrector plate.
Buy them then with all blessings, but the general concensus of opinion is not actually to fit them until you really feel your 'scope is in need of colllimation and from what you describe in your other post, it is currently performing well.
The collimation process itself is straightforward enough. Just ensure a good, still seeing night on which to carry it out, and, if for any reason you do feel slightly out of your depth on this one, just shout ! We're all here to help one another !
Best regards,
Tel
Bob's Knobs are indeed a great convenience which allow one hand to reach around the front of the OTA to make adjustments while viewing and their use also has the added bonus of removing the potential hazard of wielding a screw driver or Allen key (wrench) in the vicinity of the corrector plate.
Buy them then with all blessings, but the general concensus of opinion is not actually to fit them until you really feel your 'scope is in need of colllimation and from what you describe in your other post, it is currently performing well.
The collimation process itself is straightforward enough. Just ensure a good, still seeing night on which to carry it out, and, if for any reason you do feel slightly out of your depth on this one, just shout ! We're all here to help one another !
Best regards,
Tel
#4
Tel
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Voyager 1
Posted 11 February 2010 - 04:16 AM
By the way, Bill, if and when you do come to fit Bob's Knobs, remember to do so one at a time !
The secondary mirror does not bounce well; especially off of the primary ! :rofl2:
Best regards,
Tel
The secondary mirror does not bounce well; especially off of the primary ! :rofl2:
Best regards,
Tel
#5
Bill45
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topic starter
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Sputnik
Posted 11 February 2010 - 04:21 AM
Thanks Tel.
I will likely need the help.
I will likely need the help.
#6
Bob Griffiths
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In Memoriam - R.I.P. (1943-2016)
Posted 11 February 2010 - 08:06 AM
Easier...and FASTEST WAY IS TO REPLACE ONE KNOB...THEN RECOLLIMATE (rough but as good as you can) ... then replace the second and recollimate again... then do the third....
Sounds like a lot of extra work but it is not...pretty easy to come back real close to being perfectly collimated between installing the next knob...
You really are not ever all that much "off"
Bob G
Sounds like a lot of extra work but it is not...pretty easy to come back real close to being perfectly collimated between installing the next knob...
You really are not ever all that much "off"
Bob G
#7
brianb11213
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Cosmos
Posted 11 February 2010 - 08:08 AM
Don't fit them BEFORE the scope needs collimating, it WILL need collimating after fitting them.
If you scope is like most peoples, Bob's Knobs will rust away before you need them.
If you scope is like most peoples, Bob's Knobs will rust away before you need them.
#8
Arctic_Eddie
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Soyuz
Posted 11 February 2010 - 09:10 AM
Bob's idea has the advantage in that the replaced screw is the only one needing adjustment to reestablish collimation.
It's also possible to replace only two screws and get an X-Y adjustment scheme thereafter. If anyone is interested I can describe the procedure.
It's also possible to replace only two screws and get an X-Y adjustment scheme thereafter. If anyone is interested I can describe the procedure.
#9
Arthur Dent
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Galactic Hitch-Hiker
Posted 11 February 2010 - 10:33 AM
Hi Bill,
Welcome to CN and the NexStar forum in particular.
Don't forget that for collimation (or re-collimation):
1) you need a night with VERY GOOD SEEING, not just good but very good/excellent
2) re-centre the star EVERY TIME YOU MAKE AN ADJUSTMENT OF THE COLLIMATION SCREWS
and
3) PICK A BRIGHT STAR for collimation at a reasonably high altitude - eg Vega
Art
Welcome to CN and the NexStar forum in particular.
Don't forget that for collimation (or re-collimation):
1) you need a night with VERY GOOD SEEING, not just good but very good/excellent
2) re-centre the star EVERY TIME YOU MAKE AN ADJUSTMENT OF THE COLLIMATION SCREWS
and
3) PICK A BRIGHT STAR for collimation at a reasonably high altitude - eg Vega
Art
#10
coutleef
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Aurora
Posted 11 February 2010 - 11:15 AM
Hi Bill,
3) PICK A BRIGHT STAR for collimation at a reasonably high altitude - eg Vega
Art
Vega
Why Vega in february??
sometimes i prefer not to select a star too high so it is easier to reach my Bob knobs with the dew shield on.
If you travel with your scope, Bob knobs are essential. If not, collimation will not need to be adjusted that often.
#11
brianb11213
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Cosmos
Posted 11 February 2010 - 11:19 AM
It's getting nice & high by dawn.... but in the evening Capella is probably better. Or Polaris if you're at a highish latitude.Why Vega in february??
#12
Arthur Dent
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Galactic Hitch-Hiker
Posted 11 February 2010 - 11:52 AM
Yeah Brian you're right :o
I just plucked Vega out of the air (so to speak) as an example of a bright star that one would use for collimation purposes.
Capella is a much better bet at the moment (and will be until early summer).
Isn't Polaris a tad dim for collimation purposes?
ARt
I just plucked Vega out of the air (so to speak) as an example of a bright star that one would use for collimation purposes.
Capella is a much better bet at the moment (and will be until early summer).
Isn't Polaris a tad dim for collimation purposes?
ARt
#13
brianb11213
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Cosmos
Posted 11 February 2010 - 11:56 AM
I find it perfectly adequate .... and it's convenient as it doesn't need "chasing" across the sky, even at high power.Isn't Polaris a tad dim for collimation purposes?
#14
coutleef
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Aurora
Posted 11 February 2010 - 02:50 PM
I have read at several places that a dimmer star is better than a bright one. I must admit that i usually a brighter one!!!
#15
Peter9
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Fly Me to the Moon
Posted 11 February 2010 - 03:13 PM
Around 2nd magnitude seems to be the usual advice.
Peter.
Peter.
#16
Fimpster
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Vanguard
Posted 12 February 2010 - 05:21 PM
It's also possible to replace only two screws and get an X-Y adjustment scheme thereafter. If anyone is interested I can describe the procedure.
Eddie, I would like to hear this X-Y adjustment scheme.
#17
Arctic_Eddie
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Soyuz
Posted 12 February 2010 - 06:29 PM
You can get an X/Y adjustment with just two of the screws in a three point scheme. Assume you have a setup where screw A is directly on top and B and C are on a line across the bottom. Also, Y is the vertical axis and X passes through screws B and C. If you adjust B and C in the same direction by the same amount you will be rotating around the X axis. If you adjust B and C the same amount but in opposite directions you will be rotating around the Y axis. Rotating around one axis is the same as moving a reflected image along the other axis.
The advantage is that screw A will never come out or hit bottom because it's never touched and using the scheme above will give you the X/Y motion most people expect. The Y axis does not have to be vertical. The X axis will still be at right-angles to Y which is the orientation we need. Try this with a paper plate marked with the three screws.
The advantage is that screw A will never come out or hit bottom because it's never touched and using the scheme above will give you the X/Y motion most people expect. The Y axis does not have to be vertical. The X axis will still be at right-angles to Y which is the orientation we need. Try this with a paper plate marked with the three screws.
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