C70 Mini Mac

[Nikodn]

Hi, I’m new to SGL and pretty much a noob to Astronomy. 
I have C70 Mini Mac and I know this scope has its limitations for Astronomy, but I’m looking for suggestions how to maximise it’s potential.

If binoculars are a good place to start for Astronomy there must be some good use for the C70.

This my first post here and would appreciate any comments.

Thanks Niko...

[jonathan]

I think one thing you could try is mounting it on a decent camera tripod if you have one (preferably one with a smooth tilt and pan head) and sitting comfortably with the tripod quite low (legs not fully extended) so you only need to lean in a bit to view without having to touch the scope, although holding onto the tripod should be fine (to brace yourself and also to keep the tripod from moving), it might be a bit more comfortable that sitting at a table with it on the tiny tripod.

As for what to look at, there are plenty of interesting things you can look at through a small telescope, I would steer away from DSO (deep sky objects) and concentrate on asterisms, large targets such as the Orion Nebula (you may need to wait until December for this now), the larger planets and the moon; you should be able to observe the moons around Jupiter and perhaps even see a couple of the cloud bands (Jupiter and Saturn will be small bright discs in the scope, but they should be fairly sharp).  Jupiter and Saturn will be evening objects from about July onwards.

Look up binocular targets, treat the scope as a powerful 'half-binocular' when it comes to targets and you shouldn't go far wrong; with it being a Mak it will have a narrow field of view which should be ideal for planets, but you'll need to use the lowest magnification for asterisms and open clusters.  Might even be able to spot the occasional bright comet from a dark site.  Just don't put too much faith in the zoom eyepiece, it will probably have an optimim magnification zone where it works best so try to stick to that.  Should definitely be able to find the Andromeda galaxy with it (it's also a naked eye object) but again, the narrow field of view may hamper your view as the Andromeda galaxy is quite a wide cigar shape (it may be that you can only discern the bright galactic centre anyway).

I had a C50 Mak at one point, just a tad too small for astronomy in my opinion and as I already had larger scopes and binoculars it was quite superfluous to my needs so I sold it on.

Edited May 16, 2020 by jonathan

[bomberbaz]

12 hours ago, Nikodn said:

Hi, I’m new to SGL and pretty much a noob to Astronomy. 
I have C70 Mini Mac and I know this scope has its limitations for Astronomy, but I’m looking for suggestions how to maximise it’s potential.

If binoculars are a good place to start for Astronomy there must be some good use for the C70.

This my first post here and would appreciate any comments.

Thanks Niko...

checking the specs of this and It is around F11. It comes with a 10-30mm zoom and when using it at 30mm/x25 magnification you will get 1.3 degrees of view. However my eyepiece calculator doesn't  agree with it and gives 1.7 degrees field of view. Whichever is correct it should be ok for finding things making it easier to use.

As Jonathan says, a decent camera tripod would work well with it. It should be ok for planetary viewing, some clusters but it's the moon where this is going to perform best imho.

Globular clusters will look just like a smudge, open clusters will lack the depth of stars seen in a bigger scope and nebula will lack any structure. However you will get the buzz of hunting and finding your target object.

I would get it out to darker areas to maximise it's potential. In anything other than low light polution and viewing anything other than the moon or jupiter is going to be somewhat disappointing. 

M44 and M39 are lovely clusters and if you can get a better 10mm eyepiece with a wider field of view (70 ish or better) , you would be better equipped.

A 10mm/70 degree fov eyepiece will give you about 1 degree at x75 magnification. You would get a lot more  out of it than your supplied eyepiece. 

 

[RT65CB-SWL]

@Nikodn and welcome to SGL. 

+1 one for the above comments.

I occasionally mount my 're-modded' ETX105 on a medium-duty ballhead, (mine is the type that has a separate mounting plate, similar to the Arco-Swiss type), and a Manfrotto/Boden camera/photography tripod. It is very cheap and inexpensive alt-az mount. Just make sure the 'scope is secure to the mounting plate before each and every use.

[Nikodn]

Thanks for the prompt replies ! 
I’m glad there is use for the C70 and along with my binoculars at least I can get my feet wet because I’ve read mixed reviews.

Along with the tripod my big question is replacing the zoom eyepiece. I’ve been looking at Skywatcher  / Celestron plossl’s 

I’ve seen the wider angle eyepiece but some are nearly the price of the scope also because of the narrow FOV of the scope would I get vignetting if that’s the right word and maximise the the FOV of the eyepiece.

[happy-kat]

I have a C70. The field of view actually isn't that narrow the tricky thing is the exit pupil size I've found.

The provided zoom eyepiece is not great at the higher magnification end, the telescope optics are pretty good.

You will see a little chromatic aberration on the Moon and this is down to the inbuilt erect image diagonal prism built into the telescope within the case covering. 

It's f10 and I've taken mine apart as part of a project. The tripod is quite handy it is used here for other tasks and if you have a sturdier tripod you could use then you could mount on that using a ball head. Drop the ball into the groove and then use as a alt az movement.

You could sign up to the binocularsky news letter it has targets each month you could likely find with your C70.

 

 

[happy-kat]

Personally I wouldn't chase magnification as that leeds to tiny exit pupil.

I'd look at 15-20 mm eyepieces and hedge at the 20mm end.

Eyepiece focal length / telescope focal ratio = exit pupil size.

I personally find 1mm exit pupil is a waggle head and not pleasant to use but your milage may vary.

[happy-kat]

Being f10 it won't be fussy on eyepieces so probably pick a decent one up for around £30 or so for a plossl.

[happy-kat]

Here the rough field of view with a 20mm and 30mm eyepiece on the Pleiades

[Nikodn]

Forgetting the 10mm I’ve been looking at 15mm / 50X, 20mm / 37X and 32mm / 24X ish and that’s not pushing the magnification of the scope and gives me a good range.. 

[bomberbaz]

These eyepiece from optic star. http://www.opticstar.com/Run/Astronomy/Astro-Accessories-Telescopes-Opticstar.asp?p=0_10_5_1_8_320 
 

i have the 10&15 mm which i use in an f15 mak.  Gives me excellent views for the price and the 70 degree fov is undistorted in use.  

[happy-kat]

You are paying more for the 70° fov which unless actually useable in the C70 is wasted money.

[bomberbaz]

6 minutes ago, happy-kat said:

You are paying more for the 70° fov which unless actually useable in the C70 is wasted money.

So will the c70 not take the 70 degrees, I have no idea. I only put the link up as I have the 2 eyepieces from them as mentioned and they work great in my mak as well as an F10 frac.

These are only 30 quid. Still 66 degrees but should work fine in an F10 and if the fov is useable or the OP upgrades to another ota, they would still carry over. http://www.opticstar.com/Run/Astronomy/Astro-Accessories-Telescopes-Opticstar.asp?p=0_10_5_1_8_315

[happy-kat]

If on a tight budget then GSO (aka revelation) from astroboot are good value. 

[RT65CB-SWL]

51 minutes ago, bomberbaz said:

So will the c70 not take the 70 degrees, I have no idea. I only put the link up as I have the 2 eyepieces from them as mentioned and they work great in my mak as well as an F10 frac.

These are only 30 quid. Still 66 degrees but should work fine in an F10 and if the fov is useable or the OP upgrades to another ota, they would still carry over. http://www.opticstar.com/Run/Astronomy/Astro-Accessories-Telescopes-Opticstar.asp?p=0_10_5_1_8_315

I have the 6mm...

I purchased mine from a popular auction site; (via China 🇨🇳); and is not to bad; (I think it is better than my 6mm GSO Plossl, but not as good as my 6mm TeleVue Radian or 6mm Ortho's); and I received it within two weeks of ordering.

[bomberbaz]

11 minutes ago, Philip R said:

I have the 6mm...

I purchased mine from a popular auction site; (via China 🇨🇳); and is not to bad; (I think it is better than my 6mm GSO Plossl, but not as good as my 6mm TeleVue Radian or 6mm Ortho's); and I received it within two weeks of ordering.

I think they are erfle in design hence the fov and I really wouldn't expect it to perform as well as a radian at 30 quid but if the OP wants a step up from his existing ep without busting the bank then I reckon it's a decent option for a slower ota.

[Nikodn]

Thanks for all the replies and I’ve ordered some eyepieces - Celestron Omni 15mm, Skywatcher SP 20mm and 32mm and a variable polariser for the Moon. That gives me 50X 37X and 24X.

To keep the cost down a bit I’ve made compromises, everyone has a budget !! 
Hope I’ve not got the wrong gear, time will tell.

Thanks Niko.... 

 

 

[Herb H]

I bought one of these on Amazon a few months ago...

Decent optical quality, image is kinda crisp at the lowest magnification. I later threaded a Canon EOS T6i camera on it (with the supplied 1.25" standard telescope eyepiece adapter, and a camera T-mount for Canon) and took some decent quality pictures, although the image appears to be sharper in the provided zoom eyepiece at lowest magnification.

I tried using both a 36mm and a 20mm Celestron Ploessel eyepieces, and came to the conclusion that the (zoom) eyepiece that comes with the scope is just fine ! It is good quality and needs no improvement imo; nevertheless the scope is used best at the lower (25x) magnification where the image is definitely crisper.

I also liked the supplied short tripod, it is simple, effective, stiff, light and sturdy. A larger tripod only adds to the wobble, this one for most applications is just right imo !

But, today I checked the collimation with an artificial star, mine is definitely out of collimation. With the artificial star the pattern as you focus in and out is far from concentric, in fact it's pretty bad, more like a distorted 8. Unfortunately the six collimation screws are hard to get to (have to peel off all that rubber in order to get to the back where the screws are located), plus that prism makes it harder.  

Overall a bit disappointed that the factory did not make a serious effort to collimate this thing properly. Mine is definitely not what it could have been.

Incidentally, I also have a Celestron C90 Mak and that one is spot on in collimation ! Nice concentric rings.

[RT65CB-SWL]

Hi @Herb H and welcome to SGL. 

Sorry to read about your C70 Mini Mak. The C70 Mini-Mak [I would think] is targeted at bird watchers, wildlife and other outdoor/terrestrial/maritime pursuits. Not sure whether they can be collimated. If it is really bad, then I would be inclined to contact Amazon and Celestron for assistance.

Edited October 13, 2022 by Philip R

[Herb H]

.... As a follow up to my previous post, I did finally find the time to take the C90 apart and attempt some collimation.

Hopefully what I write below will be helpful to others !

Here are my thoughts :

(1) It is actually very easy to peel that rubber covering off, and expose the back. It turns out it is  only slightly glued on at the bottom, where there's a seam.

     I cut through the seam with a fresh blade, and then slid the cover off. You can then see the scope with the back plate exposed.

 

[Herb H]

Next :

(2) the black rounded plastic back cover comes easily off with two M2 screws.

       After which you can see the true scope flat backplate, with a nice prism at the center, and six recessed adjustment screws (three pairs).

[Herb H]

(3) Looking down the prism into the inside of the optical tube, revealed that the image there (of the primary and secondary mirrors) was far from concentric !

       That in a sense was a good thing, as it immediately revealed that something was grossly misaligned (sorry no picture here).

(4) I then proceeded to fiddle with the six adjustment screws. They are three pull and three push M2 screws it seems, their combined effect is to first move (align) the rear mirror,

      and then lock it securely into position.

(5) I was pleasantly surprised that within a few minutes, just by looking nice and straight at that circular pattern inside the prism, I was able to get the whole picture

      nice and centered, and nicely concentric ! (note that in the pic below I have trouble getting focused with my phone).

 

[Herb H]

(6) Normally such scopes can be fine tuned using an artificial star (a point source), by then examining the Airy pattern.

      I did it here as well as a check ... But to do this you need to put that rounded plastic back with the eyepiece back on, which then covers the adj. screws.

      Anyhow, now the Airy rings look pretty good, not perfect but nearly concentric ! (sorry no picture, they are faint and hard to photo).

      So, overall success with I'd say half an hour enjoyable work.

       I then went outside and pointed the C70 at a faraway building, and it looks pretty sharp. Very happy with what I achieved !

      ( Note that I was quite skeptical at first, since I worried that would have to look a the Airy pattern to collimate. In the end it was not necessary).

(7) Below you see a picture of my artificial star that I did NOT need for decent collimation. Only useful perhaps at the end, for a second check.

 

[Herb H]

So the conclusion is ...

If you have a little C70, do yourself a favor and peel that rubber off, take the rounded plastic back cover off, and check the collimation by looking through the prism.

If things are not concentric, adjust with an M2 hex key by trial and error ... Voila you are done 🙂 

[happy-kat]

Excellent photos. The outer covering on my C70 was  stuck with glue in places so didn't peel off as cleanly as yours