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X2 barlow in guidescope


Wonderweb

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Hi all.

I've tried searching for this topic but couldn't find anything. 

I am torn between getting an off axis guider to use with my orion optics ct8 at 900mm or try a x2 barlow with my 240mm guidescope to hopefully improve guiding  at 480mm. 

I've heard some horror stories of people spending all their time searching for guide stars with an oag and with precious little imaging time with work and clouds, I dont want anything else limiting my exposure time. 

Is there much benefit in fitting a barlow to my guidescope or should I try the oag? 

Thanks

Darren 

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2 hours ago, Wonderweb said:

Hi all.

I've tried searching for this topic but couldn't find anything. 

I am torn between getting an off axis guider to use with my orion optics ct8 at 900mm or try a x2 barlow with my 240mm guidescope to hopefully improve guiding  at 480mm. 

I've heard some horror stories of people spending all their time searching for guide stars with an oag and with precious little imaging time with work and clouds, I dont want anything else limiting my exposure time. 

Is there much benefit in fitting a barlow to my guidescope or should I try the oag? 

Thanks

Darren 

I've got a oag on my SCT (1280mm FL)setup and also one with my esprit 80 (400mm FL)/Qsi as it has a internal filterwheel... I've never had to search for a guidestar with either setup... 

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1 hour ago, ollypenrice said:

What is the pixel scale of your present guider and what is your imaging pixel scale?

And, maybe, why do you ask? If you have a problem, what is it?

Olly

My current guide setup is 3.22"/pixel and my main scope is between 0.75 and 0.86"/pixel depending which coma corrector i am using. 

I am.trying to improve my guiding. I am currently getting between 0.7 and 1 arc second total rms with my eq6-r but would like to get it down to around 0.5-0.7 if I can. 

The mount is well set up and the rig well balanced.

Edited by Wonderweb
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You won't be able to capture detail at 0.86"PP because of the seeing,  From what I remember of Derbyshire, I think you might need to double that figure, in which case your guiding is close to meeting your requirements, but I can understand that you'd like to improve it.

I rather doubt that your guide trace is limited by the pixel scale of your guide setup: it's more likely to be limited by the mount's mechanical errors. You could certainly try an OAG but, from my fairly high site (900M) I've developed a liking for the ST80 as a guide scope. It gives a 400mm FL and has enough light to find stars everywhere. This may not be the case with with a Barlowed guidescope.

Have you tried running the PEC on the mount as well as the guider? I've never tried it but several members have found that it worked for them.

Olly

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On 09/01/2023 at 08:16, ollypenrice said:

You won't be able to capture detail at 0.86"PP because of the seeing,  From what I remember of Derbyshire, I think you might need to double that figure, in which case your guiding is close to meeting your requirements, but I can understand that you'd like to improve it.

I rather doubt that your guide trace is limited by the pixel scale of your guide setup: it's more likely to be limited by the mount's mechanical errors. You could certainly try an OAG but, from my fairly high site (900M) I've developed a liking for the ST80 as a guide scope. It gives a 400mm FL and has enough light to find stars everywhere. This may not be the case with with a Barlowed guidescope.

Have you tried running the PEC on the mount as well as the guider? I've never tried it but several members have found that it worked for them.

Olly

Is there something specific about Derbyshire that limits the seeing? 

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1 minute ago, Wonderweb said:

Is there something specific about Derbyshire that limits the seeing? 

Nothing much, no,  The best seeing is generally to be had at high altitudes on small islands and, although Debyshire is very hilly on small scales, it is never all that far above sea level. It is also ringed by hot cities. Realistically, to image below 1.5"PP, you are going to need very good seeing. My advice would be not to devote huge amounts of money or energy on chasing resolution. I'd chase signal instead. You can do a lot with that in post-processing.

Olly

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  • 2 weeks later...

We have Bortle 4 @ ~400 MSL here in SW New Hampshire, so I'm hoping that this set up (my first imaging set-up) will not be pushing it to much.

We also have Bortle 5 ~20 miles west, and Bortle 6 ~20 miles east - but we are about 300m above both.

Guider: (3.75um / 240mm) x 206.3 = 3.22 arcseconds / pixel

Imager: (2.40um / 400mm) x 206.3 = 1.23 arcseconds / pixel

I have a 2x Barlow so I may try experimenting myself ! 😀

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