Celestron Mini Mak C70 and Barlow Lens

[Nikodn]

The Celestron C70 Mini Mak  has a 750mm focal length and a 70mm objective. With the scope being a small Maksutov and my high power eyepiece is a 15 mm which gives me 50X magnification Would using a 2X Barlow lens be too much for the optics and has anyone had any experience with using a Barlow lens with the C 70 Mini Mak.

[Mr niall]

Yes I've used one they are brilliant (but no finder scope)

The mini mak has a focal length of 750mm. So if you add a 2x barlow to a 15mm that gives you an effective 7.5mm that's 100x.

Maximum usable magnification is a bit of a moving target but some people say 50x per inch of aperture or 2x aperture in mm - so lets say 140x would be your max.

So far so good - but... that 7.5mm effective eyepiece would give you an eyepiece of 0.7mm - which will make things a bit dark at the eyepiece but is still usable.

In theory - for targets like the moon and planets - that would be a fairly reasonably absolute maximum I'd say. But only for moon and planets. 

[Ruud]

I had a C70. It worked best at the lowest magnification I tried:  23x with a 32mm GSO Plössl. This was about the only magnification that my minimak handled with any grace.

I blame the erecting prism. I kept the Plössl and gave the C70 to a shop 'selling' free second hand stuff. I still had the original 25...75x eyepiece and all else: table tripod, box etc. I put a note on it saying that I thought it would probably make some kid happy and not to look at the Sun with it.

You could invest in a 32mm GSO Plössl if you want to. It's a decent eyepiece and I still use mine on my new 70mm telescope.

[Ruud]

By the way, Mr Niall, you can easily make a finder yourself for the C70 from a ballpoint pen.

[Mr niall]

2 minutes ago, Ruud said:

By the way, Mr Niall, you can easily make a finder yourself for the C70 from a ballpoint pen.

yeah that's what I did with mine!

[Nikodn]

On 11/06/2020 at 22:48, Mr niall said:

Yes I've used one they are brilliant (but no finder scope)

The mini mak has a focal length of 750mm. So if you add a 2x barlow to a 15mm that gives you an effective 7.5mm that's 100x.

Maximum usable magnification is a bit of a moving target but some people say 50x per inch of aperture or 2x aperture in mm - so lets say 140x would be your max.

So far so good - but... that 7.5mm effective eyepiece would give you an eyepiece of 0.7mm - which will make things a bit dark at the eyepiece but is still usable.

In theory - for targets like the moon and planets - that would be a fairly reasonably absolute maximum I'd say. But only for moon and planets. 

Thanks for the replies.

I already already have a 15mm plossl eyepiece which gives me affectively 50X But my issue is that with the supplied zoom lens after 60X the imaged tended to get a little bit soft and I was struggling to get a good clarity at 75X. 
I am wanting to invest in a 2X Barlow lens but because of how the telescope performs at 75X with the stock zoom and also how tricky the focusing is I didn’t really want to bye the Barlow if the clarity is below par for  say the Moon and Planets.

 

[happy-kat]

The stock lens I found did get very soft the higher the magnification but I'm not sure if I used a barlow with a 10mm or not and it would have been a 1.6x if I had. I'll check my photos later.

[Tim C]

On 11/06/2020 at 22:01, Nikodn said:

The Celestron C70 Mini Mak  has a 750mm focal length and a 70mm objective. With the scope being a small Maksutov and my high power eyepiece is a 15 mm which gives me 50X magnification Would using a 2X Barlow lens be too much for the optics and has anyone had any experience with using a Barlow lens with the C 70 Mini Mak.

For what it's worth - my experience with this little beauty has been fantastic. It's given one of my housemates their first view of Saturn's rings with a 5mm Celestron Xcel and a x2 Barlow (Edit: the exit pupil is a bit of a bitch past a certain point but not impossible by any means). Took a little while to focus but got a satisfying image, after enough effort to make it feel earned but not onerous! I do read that the quality control on these is supposed to be appalling so your mileage may vary, but I think mine is awesome. Cheap enough as well that one day I might feel bold enough to follow one of the guides around here about taking it apart, flocking it and maybe replacing the prism to see just how far it can be pushed!

The c70 has taken a lot of flak online from what I read in the past, picked it up on a whim when I saw it on sale for £80 and absolutely love it. Using it with a Meade zoom on a fluid head tripod is a joy 🤓

Edited September 22, 2020 by Tim C