Thanks for all the fish

[Eric the Halibut]

Firstly thanks to everyone who answered my question about upgrading from my Celestron 6SE, the information was very useful and certainly caused me to have analysis paralysis for a time. I have now ordered a Skywatcher 250P auto dobsonian which seems to be the best compromise for me in terms of practicality and cost though I am still nervous about not having the goto facility.

What I would like to know is:

1) Is the shroud absolutely necessary? My back garden is modestly light polluted eg I located and was able to view a mag 9.2 star recently in the 6SE.

2) To set up the auto tracking do you only need to input your latitude and longitude as one of the reviews of this scope suggests?

3) Can you use the scope as a purely manual scope ie no tracking?

4) I have a set of GSO 1.25 eyepieces which seem to be reasonably ok in the 6SE and will be using them initially. I understand that the fast focal ratio of the scope is more critical on eyepieces so I intend to get some 2 inch ones. Baader Hyperion eyepieces seem to be well liked here but is the difference between the main contenders ie Baader, WO, Swan etc all that significant and how do they compare to say the Televue Radian series that seems to be available at 20% discount at the moment. I like the idea that the Hyperion seem to be dual size ie 1.25 inch or 2 inch.

5) Everyone seems to recommend the Hotech laser collimator which has the compression rings. Will I need the 2 inch version?

Thanks in anticipation for any advice.

[RobH]

Hello Alex.

I can't answer all of your questions, but....

1. Yes, a shroud not only significantly increases contrast, but also acts as a dewshield for the main mirror.

5. Laser collimators assume that your focuser is collimated, which often isn't the case.

I used a Hotech on our 12 inch Lightbridge and it was miles out by the time I'd finished.

I would suggest first getting a cheshire collimator and checking out astrobaby's guide to collimation, although I've no idea where it is on the forum....someone will be along to help though no doubt!

Cheers

Rob

[BrianH]

astrobaby's guide to collimation Astro Babys Guide to Collimation

[John]

On the eyepieces, the GSO plossls are pretty good. It might be worth using them for a while until you can decide where you would really like to invest more.

Hyperions are nice but in an F/4.7 scope (which the 250P is) they do show quite a bit of astigmatism in the outer 20% of the field of view - you could argue that your GSO's show just as much usuable field of view.

Of the ones you list I think it's only the Radians that would be relatviely free of this issue. Radians are 1.25" of course but you can get 20% off them at the moment.