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Hello from Cincinnati, Ohio. Rotorcraft CFI, Aviation Author

barnstorm

By barnstorm
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barnstorm

barnstorm

Posted
Posted

Hi everyone,

After years and years of using my ETX90 I have taken the plunge and purchased a slightly larger used scope and I am looking for some sage advise.

My new scope is an old 16-inch Meade StarFinder Dob.

My Hotech Laser Collimator arrived today and my Meade 56mm super plossl.

Someone has already installed a fan in it and I have ordered a Telrad.

The knowledge I seek at this point is:

1. Is there a 'drop-in' replacement for the PLASTIC stock meade focuser? I notice that the previous owner must have had another focuser in at some point as the tube is drilled out about 1/8 larger and there are screw holes.

2. Coma Corrector? Yes or No?

3. Other suggestions? I have seen some posts about large Dob owners covering up the scope to get better planet viewing. Really? I got the scope for hunting nebula but still, got to have my planets! can someone explain this.

Thanks!

.

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Rusty Strings

Rusty Strings

Posted
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Hi and welcome to SGL

Quite an upgrade to a 16" dob. I don't know if there is a drop in replacement, but any of the crayford focusers that are available should be made to fit ok.

I've never needed a coma corrector for my newt. I guess it's down to how much coma you have and if it offends your eye.

What some dob owners do is use an aperture stop in an attempt to improve contrast for planetary viewing. This involves making a cover for the open end of the scope where the light enters and cutting a circular hole that sits between the spider vanes. This has the effect of reducing the aperture, which will increase the focal ratio of the scope and thus make it similar to a long focal length refractor. I've had a go myself and all it seems to do is dim the image.

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Mr Spock

Mr Spock

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Hi, welcome to SGL :)

There are a few replacements you can get for the focusser. Something like the a Skywatcher should fit.

If you are going to go wide with a short focus Newt then coma will be a problem.

Nothing can beat aperture :) Stopping down can increase f-ratio to where lesser eyepieces can perform as well as more expensive ones, it can increase contrast by putting the stop away from the secondary, and smaller scopes can perform sometimes better on nights of poor seeing. Overall there's little point in having a large scope and not using all its resolution - size matters!

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barnstorm

barnstorm

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thank you Rusty and Spock!

I have been searching crayford and JMI focusers for hours and all of the mounts seem to stop at 12"

I will put google on the hunt for a SkyWatcher focuser and see what happens.

Thanks!

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SteveA

SteveA

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thank you Rusty and Spock!

I have been searching crayford and JMI focusers for hours and all of the mounts seem to stop at 12"

I will put google on the hunt for a SkyWatcher focuser and see what happens.

Thanks!

Take a look at the Moonlight website;

MoonLite Telescope Accessories

They do a universal install kit for their CR focusers....

"Universal Install kit for our CR model focusers. Fits all 6",8", 10", 12", 14" and 16" Newtonian scopes such as Orion, Sky Watcher, Celestron , Vixen, GSO, Meade Light bridge, DBA, Hardin, Antares, Parks, and Astro Tech. "

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