Eyepieces Compatible with a 80mm Telescope

[Katfish Frogmore]

Hello. I have an IOptron Smartstar R80 telescope. It came with a 100mm and a 25 mm eyepiece.  The scope is rated as D=80mm and F=400mm. What other size eyepieces or viewing accessories would be a good match for this scope?  

[brantuk]

Hi Katfish and welcome to SGL

You can work out what magnifications you want with Mag = F / Eyepiece length (in mm). So your 10mm gives 400/10 = 40x mag and the 25mm gives you 400/25 = 16x mag.

Also your focal ratio is given by F/Aperture. In your case it is 400/80 = 5. With F5 I'd suggest you get the best quality eyepieces available within your budget. Slower scopes F10 and above are more tolerant of lesser quality eyepieces. Hope that helps some.

[Dave In Vermont]

Your refractor is an F/5. So it may benefit from a 2x Barlow, giving you the equivalent of 12.5mm and 5mm eyepieces. I am assuming you meant to write it came with a 10mm and 25mm eyepiece. These give you 40X and 16X, so a 12.5mm will give you 32X and 5mm will give you 80X.

To find the magnification of an eyepiece, you simply divide the focal-length of the scope by the focal-length of the eyepiece in question. Such as: 400mm / 10mm = 40X.

It's really up to you if you want higher magnification. A F/5 telescope like yours excells at giving you a wide-field view of the cosmos. Not so great for close-up looks at planets at high-power.

Hope this helps -

Dave

 

PS - Ouch! Your foot is on my shoulder!

[Louis D]

Be aware that this scope appears to come with a 1.25"-only focuser, so avoid buying any 2" eyepieces accidentally.

[ronin]

One aspect that is generally useful is to give an idea of how much per eyepiece and the overall budget that you are coinsidering. Otherwise you get told just about everything from fairly inexpensive plossl's ($30) to TV Naglers and Ethos ($500).

The scope appears to be the 80mm f/5 achro that appears under several names, so unfortunately high magnifications are usually difficult to achieve, the scope will begin to show chromatic aberrations and I suspect a couple of others. It is the nature of the scope, it will as mentioned previously give nice wide field views, so consider making up a list of clusters to head out and observe and tick off. Check if the Astro League has an observing program for clusters. Otherwise use the Wiki entry for Messier objects, reorder and print out the Clusters. Check out the Caldwell Objects. Also dig out some double stars, the Delaware Astro site has a short list of colored doubles that make fun observing, could add in Red Stars - sounds a little "off the tracks" but there are some and it is a bit different. Especially the Carbon Stars, which can be difficult.

Jupiter and soon Saturn are likely to be 2 things to go find. Jupiter should be OK at 80x so a 10mm eyepiece, Saturn will need a bit more say 120x so a 7mm eyepiece for 114x. Of course the 7mm would do Jupiter also.

At, and around, the focal lengths mentioned there are:

Celestron X-Cel LX for 7mm, and 9mm, cost in the US is about $60-65

Astro-Tech Paradigms for 8mm at $60

William Optics 6mm planetary - sorry no idea of the cost.

At 5mm there are the X-Cel LX's and the Paradigms.

At the wider end there are many, the already mentioned Paradigms and X-Cel LX's both have a selection.

I have a small 70mm f/5 scope (similar) and my eyepieces for that are: Paradigms in 5mm, 8mm, 25mm and the WO 6mm planetary. They cover all I want. I would half suggest the 18mm PAradigm instead of the 25mm simply becasue there are little questions over the 25mm performance and the 18mm is wide enough anyway. I just happened to have/get a 25mm and not a spare 18mm so I use the 25mm.

Other items: Solar filter, your scope will be good to take a look at the sun. You do not need a moon filter.