Help?

[Mitchell.Stott]

I am very new to astronomy and am currently looking for a telescope. I have found a Skywatcher Black Diamond 150 x 750P w/EQ3 equatorial mount/tripod package for AU$469 and am a bit confused about the 150 x 750p. Is that the focal length because I don't really understand that. Also how do I find out the aperture and also is an EQ3 mount stable, because someone told me that EQ mounts are not good unless you get an EQ5.
Thanks!

[LAW]

It depends which EQ3 it is and what you want to do with it, I don't have much experience with the new ones so I'll leave that for someone who knows.

As for the Focal Length and Aperture it's all in the name ;) 150x750 means it's 150mm aperture and 750mm focal length (not sure what the "p" means?).

That seems like a pretty good deal for a reasonably 'fast' (good aperture/focal length ratio) refractor. The EQ3 probably wouldn't do too well for Astrophotography because the scope is close to the weight limit of the mount and the old ones didn't have sidereal tracking without upgrading the motors and controller (don't know about the new ones though). But it wouldn't be bad for visual use either.

[Allan_L]

Hi Mitchell,
Welcome to Ice In Space :welcome:
The 150 would be the aperture in mm
(so that equates to a 6" scope)

The 750 is the focal length.

Any EQ mount can be tricky and sometimes unstable, because they get into all sorts of weird positions. This is usually overcome by correctly balancing the scope with counter weights.

A more stable mount is the Dobsonian mount.
Much easier for a beginner to use.
And generally cheaper to buy.

Edit:
Ah! Murphy you just beat me.
BTW: The scope appears to be a parabolic Newtonian Reflector, not a refractor.

[Scorpius51]

Hi Mitchell, Welcome to IIS!

As a beginner, you may find an equatorial mount to be inconvenient to use, unless you intend to do manual tracking. I am assuming it is not motor driven and only has two slow motion control knobs (RA and Dec).

If you just wish to observe visually & casually, then a Dobsonian mounted 150mm (6") reflector would be much better and cheaper purchase.

A GS 200mm (8") Dob can be purchased for $399 - cheaper, more aperture, a better scope and easy to use.

Cheers
John

[LAW]

Oh sorry, didn't realise it was a reflector, I agree, you're probably better off with an 8" Dob then. Excellent for visual use but less suited to astrophotography so it's a personal choice. I have an EQ mount because I want to take photos but Dobs are easier to point at what you want to look at.

[Mitchell.Stott]

Thank you for the feedback. I was borrowing a telescope before now but have just returned it. It had an eq mount that was very clunky (although it was also old and stiff). This is pushing me in the direction of a Dobsonian but I have one main problem, how do you find stuff with it. My friend and I went observing and he has a Dob but we were having trouble finding things because there are no measurements on it. At least with a EQ mount you can find things with your right ascension and declaration.

[Scorpius51]

Hi Mitchell

I think you mean declination!

However, it is relatively easy to start identifying the major constellations brighter stars, nebulae, clusters, and brighter planets. With the help of star charts, a planisphere, and planetarium software such as Stellarium (it's a free download), or even iPod apps, you can find most significant objects in the night sky without reference to RA and Dec. From then on it is a matter of star-hopping to find the more elusive objects. This can be a challenge, but very rewarding.

Cheers
John

[LAW]

I found the easiest way was to print an inverted screenshot in Stellarium.

The advantage of taking your own screenshots is you can set the field of view to whatever you find most helpful, for bright objects like M42 it's pretty simple, but I when you try and find things which aren't visible to the naked eye it helps to have several maps of increasingly small areas to help zero in.

[mark3d]

A dobsonian is good value because rather than splitting the expense into optical tube and mount, most of the cost goes into the optics.

You can make your own 'degree circles' or 'manual setting circles' as seen on Cloudy Nights (http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/937949/page/0/view/collapsed/sb/5/o/all/fpart/1/vc/1). This requires printing the paper degree circle for the base, and then ideally getting an inclimeter that measures the vertical angle of the scope. With this, you look up the Altitude/Azimuth coordinates of an object (requires access to a computer or mobile with planetarium software such as Stellarium or Skeye, respectively), and point your scope to it.