Telescope mount n formulae
Telescope mount n formulae
Hi guys, Jingguo here. Just wish to know what r some things we need to know about a telescope mount?? i heard about there's some error involving mount during astrophotography.
the error i know during astrophotography is periodic error when motor driven
though the gears and worms of the dec and ra axes can be machined to high accuracies, they cannot be made to perfection...so therefore when motor driven, the gears may lose accuracy...however the loss in accuracy usually occurs at a regular interval.
it can be corrected by installing a periodic error correction (PEC) circuit. PEC circuit works by "remembering the amount of error" and corrects it periodically...but first you would need to "train" the circuit by manually tracking a target...
periodic error should not be a problem if the scope is guided manually but you may require a guidescope...
thats all i know...hope its useful...
members please correct me if i'm wrong...
though the gears and worms of the dec and ra axes can be machined to high accuracies, they cannot be made to perfection...so therefore when motor driven, the gears may lose accuracy...however the loss in accuracy usually occurs at a regular interval.
it can be corrected by installing a periodic error correction (PEC) circuit. PEC circuit works by "remembering the amount of error" and corrects it periodically...but first you would need to "train" the circuit by manually tracking a target...
periodic error should not be a problem if the scope is guided manually but you may require a guidescope...
thats all i know...hope its useful...
members please correct me if i'm wrong...
K.L. Lee
Hi Jingguo,
Having given the talk on astrophotography weeks back, recall that the telescope mount has two error properties:
1) Periodic Error - which states that the gears on the DEC and RA cannot be made perfectly round. Anything that is out of round, gives rise to periodic error.
2) Random Error - states that the mount gears and worms might have dirt, grit, packaging bits, any other particles that are stuck on them. This will give rise to jittery random tracking of the motorised mount.
Basically one of the fundamental factors in mount consideration is the minimization of PE. RE can be minimized by ensuring that you clean the mount regularly, and make sure the gears are free from foreign entities.
rcj
Having given the talk on astrophotography weeks back, recall that the telescope mount has two error properties:
1) Periodic Error - which states that the gears on the DEC and RA cannot be made perfectly round. Anything that is out of round, gives rise to periodic error.
2) Random Error - states that the mount gears and worms might have dirt, grit, packaging bits, any other particles that are stuck on them. This will give rise to jittery random tracking of the motorised mount.
Basically one of the fundamental factors in mount consideration is the minimization of PE. RE can be minimized by ensuring that you clean the mount regularly, and make sure the gears are free from foreign entities.
rcj
Hi Jingguo,
U can also use a flip mirror so u can use a micrometer eyepiece at 90 degrees to fine tuning using slow motion controls. By the way, some books claim that 'goto' scope are not good for long exposure astrophoto due to scope guided by the gears turn in tiny circles? Can any old help to elaborate?.......
:roll: :roll: 8) 8) 8)
U can also use a flip mirror so u can use a micrometer eyepiece at 90 degrees to fine tuning using slow motion controls. By the way, some books claim that 'goto' scope are not good for long exposure astrophoto due to scope guided by the gears turn in tiny circles? Can any old help to elaborate?.......
:roll: :roll: 8) 8) 8)Hmmm....GOTO scopes probably is taken in the context of fork mounted versions like the LX200 or Celestron equivalents? They would suffer from field rotation issues but with the recent trend of short exposure imaging with DSLRs, i don't think it is a major vexing issue anymore. If the GOTO scope is being referred to a GE mounted version, it should be condusive for long exposure photography provided it is drift aligned properly. Incidently, i am not sure what you mean by using a flip mirror and a micrometer eyepiece (reticle?) for fine tuning, that has got to do with mount errors? Perhaps you are referring to manual guiding for long exposure imaging? This was discussed in another thread in the astrophotography subforum.
rcj
rcj
rcj
rcj