Skywatcher EVOSTAR 150

[Third rock]

Hi. I am just wondering what sort of images I could get from this scope using a 1100d or a spc900 as I'm still deciding on a scope. Kind regards.

[John]

I'm not an imager but I don't think the Evostar 150 is a good choice for imaging. It is a long and heavy scope for one thing so it will need a really stable mount such as an EQ6 for imaging. The other drawback is that the scope is an achromat refractor and will produce quite a bit of false colour which I think will not help it's case as an imaging scope.

[Chris]

I Do a bit of imaging, and for DSO you need short focal length e.g. f/5 or f/6 and for webcam planetary imaging you need a long focal length e.g. f/12. For imaging your ratio of mount to scope needs to be high particularly for DSO imaging, so a very sturdy mount with a small scope would be good. There are 2 rough categories for optical tubes for DSO imaging, Refractors and Reflectors. If you go down the refractor route you need like I say a short f/ratio and quality lenses , ideally a short tube Apochromatic refractor such as an ED80, Megrez 72, equinox range, or like I've only just got hold of a Williams Optics zs66 DS APO, there are many more. The advantage of Apo's is that they need no collumnation, they are very portable, give excellant images i.e. they show what they show better than anything else. the down side is that they are very expensive per unit aperture. The other main branch of DSO imaging is with a reflector such as a 150 or 200pds by skywatcher. The benefits of reflectors include a lot of aperture for your money so they are good for DSO visual work as well as imaging, the downside is that they are bulky and can put more strain on the mount and they catch the wind because of their large surface area which can inturn make tracking less accurate, plus they need regular collumnation to keep them tip-top but this isn't too difficult and there are plenty of collumnation aids on the market such as laser collumnators. For planetary webcam imaging Maksutov scopes are popular because they have high f/ratios and good contrast, no collumnation, and are portable, the only downside I can think of is the cooldown time is relatively long so its best to leave them outside cooling for a while before imaging. I wouldn't recommend the 150 evostar for imaging as its big the optics will have quite a lot of false colour, and the f/ratio isn't good for either DSO or planetary imaging, if you want to start out with a cheap refractor like the evostar get the startravel because they have a much shorter focal length (short f/ratios grasp a lot! more light than long f/ratios, hence much much shorter exposure times required) the startravel will however have even more false colour which to some extent be controlled with a semi-apo filter or fringe killer but this is a much better compromise as the short f/ratio really is key for DSO's. My new WO 66 is f/5.9 and I would like to go even shorter with a focal reducer:D

hth

Chris

[Third rock]

Thanks very much chaps.