A few question

[Rumfuddle]

After my first nights stargazing I have a couple of questions:

I checked the collimation of my new scope (200p Dob) yesterday using a chesire collimator and following astro-baby's excellent walkthrough, everything seemed to be spot on. when I carried out a check on a star last night instead of concentric circles as I defocused I just got a half circle halo. Does this mean that the collimation is out or was the check affected by atmospherics? The views of the Moon and Jupiter seemed very sharp.

After swapping back and forth last night betwen the 2 stock ep's (10 and 25mm), whilst juggling lens caps, glasses and hip flask, I have spent some time this morning looking at new eps and am very tempted by a Baadar Hyperion Zoom as my 1st ep buy. Would this be a good choice for my 200p for a newbie, my thinking is that I can just get on with viewing and leave the juggling practice until I'm more dexterous?

Thanks

Lee

[Ganymede12]

If you didn't see concentric circles during a star test then it must be out of collimation. As for EP's, I would suggest you wait until you feel you need new EP's. If you already think that then I suggest a 2X Barlow lens because it would effectively double your EP collection.

[Capricorn]

The circles should be concentric, however check that the focuser is sat flat and that the cheshire is a good fit and isn't sat at an angle when tightened.

Eyepieces: well yes get used to the ones you have but they are not great and I would say that 4 eyepieces are a minimum to cover most situations or requirements. Your scope is f/6 so a 6mm gives 200x. Now 200x is generally accepted as the maximum reasonable usable magnification, you might get more at times but not that often. Also not really that many objects that are that much better at 200x then at a bit less.

So 2 options:

To have 200x available: 6mm, 8mm, 12mm, 25mm - the 25mm could go out to 32mm it is simply for wide views.

Ignoring 200x: 8mm, 12mm, 15mm, 25mm or longer.

Which brand - well most of the above are from the BST ramge except the 6mm.

Vixen NPL are 6mm, 8mm, 15mm, 30mm amongst others.

Celestron X-Cels are 7mm, 9mm, 12mm, 25mm, amongst others.

Based on cost if you got 4 BST's then for much the same cost you could get 6 Vixens and 3 Celestrons. Mention this as cost is relevant.

Since most DSO's are dim then magnifing just makes them dimmer if it goes too high. The possible exception being Orion that is becoming dominent and where higher magnifications become an option as it is bright. After that it is planets that allow magnification. However Jupiter is good at 80-120x and Saturn good at 120-150x, so 200x is not necessary for either of them. Mars next year may need over 200x as in 250x or more, when perhaps the 5mm BST could be useful giving 240x.

[Rumfuddle]

Thanks for the advice, I went back through the collimation checks again yesterday and the secondary was not exactly centred with the focuser. After fiddling with it and rechecking everything else it all looked fine, and I did not have to touch the primary. Last night the star check showed an unfocused image that seems to match all the images of a correctly collimated scope. Unfortunatly it clouded over before I could see the improved (hopefully) image of Jupiter.

I'd already calculated my lowest and highest power Ep's using Warthog's excellent pinned topic in the Beginners H&A forum, but I was just tempted by the ease that a Baadar Hyperion Zoom seems to offer, but only if the image was close to that provided by individual decent quality ep's. I'm in no hurry to 'upgrade' yet just curious and mentally window shopping.

Cheers and clear skies.

Lee

[VigdisVZ]

Some guys in my astronomy club were scratching their heads with a friends home built newton. They collimated it very precisely. Then after a few minutes of handling the scope it was bad again. Turned out the mounting for the secondary mirror was flimsy and shifted easily. To make a long story short: Check that everything is secured, and the struts holding the secondary are up to the job.

Good luck wit the eyepieces also.