Focal length, ep's and what size ep's to get?

[Daz Type-R]

Hi all.

So now I have decided to upgrade my ep's and purchase a Telrad but I have a question regarding ep's.

What would be a decent spread of ep's to go with my scope, would I need a 5mm, 8mm, 12mm, 15mm, 18mm and 25mm or is that overkill?

Would I just need 4, say 5mm, 12mm, 18mm and 25mm?

Would a bigger ep be beneficial, say a 30mm (if one exsists)?

Also, what is the focal rate of my scope, some say it is an F5, others say it's an F6, FLO (where I got it from) says F5.9 (so 6)?

Any advice would be appreciated.

Cheers.

Darren.

[brantuk]

A 30/33mm wide angle 2" ep would be a nice addition to that range for viewing the bigger galaxies and open clusters. It's lower mag but you'll get the whole object in the fov. I use William Optics Swans which are good value. But you could go mad and look at Uwans or Televues.

If you work out the steps for a range of magnifications for your scope, and get a good barlow to go with, you'll find you might only need 3 or 4 in total. I go in 4mm or 5mm steps depending on focal length.

You can work out your f-ratio by dividing focal length in mm by aperture in mm - you should be able to tell me what your f-number is lol

[ronin]

I find that you use more smaller ones then long ones.

When you try for highish magnification it is often not usable so you switch to something a little longer, hoping that it will be OK and you still have reasonable magnification.

I would have gone for 5, 7, 10, 15, 25 (or 32).

If the scope is f/5.9, focal length of 1180mm then maybe start at 6mm, then maybe 6, 8, 12, 20, 32.

You say is 6 overkill. 6 isn't even starting. Most of us have eyepieces that number in the double figures, or more occasionally.

If TV did a 6mm plossl (they don't) I would suggest collecting the TV plossl's and so having a good selection to keep. TV Plossl's come in 8, 11, 15, 20, 25, 32, 40mm. The shorter 4 are a nice set and then say the 32.

Some of the decision will depend on what you want, a random selection, more choices, or all one brand, looks nice.

[brantuk]

The answers 5.9 by the way in case you're still stuck 1200/203 = 5.91133

[coffee_prince]

I have the same scope as well.

My idea is that 200x is probably the highest you can go with this dob and then things get hard, I already find it a pain tracking with 10mm, a 4mm would be insane and probably not usable magnification.

I'm aiming for 7mm as my smallest, 16mm mid, and 28 low power.

BUT is ther a reason why 28mm are done in 2inch size as they are a lot more money!

[rwilkey]

I have found with my f/5 that keeping focal lengths in the lower range is more ideal, then barlowing if need be, that way you keep a good FOV and good eye relief. I find high power uncomfortable with a manual scope. A 32mm is my most used ep.