Hints/tips for using a dob mount scope?

[patomlin76]

Hi,

I'm relatively experienced using an eq mount as I've had a Skywatcher 130p for the past 3 years. However after resurrecting interest with the help of my son and star gazing live on the bbc, I sold that and got a bargain on a used Orion XT8 dob.

Impatient as I am, I wanted to have a quick try before bed last night, but quickly found the whole usage thing will take some getting used to. Especially coordinating slight hand movements with what you're seeing in the eyepiece.

It came with a 9x50 90 degree ffinder which replaces my old red dot sight, and that takes some getting used to as well!

For the experienced users i guess you get used to a manual alt-az mount over time, but it'll be interesting looking at objects at high magnification...

For ease of setup and portability though it's excellent, I just can't wait to compare some views with my old 5 inch scope. How much more light does 8 inch gather compared to 5 by the way?

Thanks! Paul.

[Astro Imp]

Never having used a Dob I can't advise on use.

However the light gathering of scopes is directly proportional to the area of the mirror/lens. So in your case 8²/5²  approx 2.5 times.

[PHIL53]

I would say that coordination of movements will come natural after the first few nights, but to help you aim for a DSO, I would strongly advise to get yourself an optical finder such as a Telrad (my favourite) or a Rigel Quickfinder, that really should be standard accessories for any Dobson.

[BeanerSA]

When I move the dob, I imagine I am trying to pull the object back into view. That seems to work for me.

90° finders really need some sort of zero-mag finder as well, as it's hard to "sight" down the side of a tube with a 90° finder.

[Tinker1947]

Give the movement a few session and it will become second nature, get a Telrad there good, also download Stellarium and the Telrad Maps, there both free....

Stellarium..

http://www.stellarium.org/en_GB/

Maps, there are others

http://www.atmob.org/library/member/skymaps_jsmall.html

[patomlin76]

Thanks all, I'm away this weekend but hope for clear skies when I return. With an increase in light gathering I'm looking forward to bringing out a little more detail in DSO's.

The moon looked lovely and bright and detailed last night, I'm still unsure of the maths of it all, but will my 9mm perform better on the 8in compared to the 5in, in that detail will be brighter or sharper?

Thank you all!

[laudropb]

You will quickly get used to operating your scope, so don't worry. I would use a lower magnification to learn with. At high magnification the target moves through the FOV very quickly. This is no great problem once you are used to nudging your scope. I agree with the suggestion of using a Telrad or Rigel finder. I have the Rigel and use it in conjunction with a RACI.

[John]

I tend to use eyepieces with wide fields of view with my dobsonian. This reduces the tracking effort a little.

At higher magnfications, I don't attempt to keep up with the object being viewed. What I do is to nudge the object across the field of view so that it's closer to the edge of the field opposite from the direction it's drifting in, then observe it while it drifts across the field, then nudge it back over again, and repeat.