Skywatcher Evostar 120 achromat

[alexbb]

Hello all,

This weekend I went to my girlfriend's parents and they live in a village under superb dark skies. As I wanted to travel light, I took only the EQ5 and the Evostar 90/900 achromat. With the M13 directly visible naked eye without even needing to search for it, the views with the 90mm were pretty good. I believe I saw some structure in Bode's Nebula and Whirpool, not sure if I could resolve something in Pinwheel or just something fuzzy there.

Most of the times is not possible to carry the dob, I didn't even get it out for more than one year. Other larger scopes that  I have are an 102/500 StarTravel achromat, an 130 PDS which is sometimes set up home for imaging and I don't want to disturb it and a C6 which takes longer to cool out and sometimes I worry about the vibrations that it takes on the road and possibly leaving it in the car under the sun, therefore I avoid sometimes to take the C6 out too if I don't go out especially for observing.

I don't mind the 90/900 chromatic aberrations, but this has a smaller aperture and a longer focal ratio than the 120/1000.

Now, I wonder if it's worth the upgrade to an Evostar 120/1000 for the extra aperture, but more chromatic aberrations. And, of course, it's not free, while the scopes I have don't cost me anymore.

I was thinking to get the Evostar with an EQ3-2 mount and put the OTA on the EQ5 and give away the Evostar 90/900 together with the EQ3-2 mount.

What are your thoughts about this?

Thanks and clear skies,

Alex

[Peter Drew]

If travelling to a dark site and your main (astronomical) interest is DSO's I would have thought that a 120mm F5 Startravel would be a better bet as CA is pretty much a non issue for low power wide field observation.  

[alexbb]

I'd like to get a little more personal with them so I'd like to increase the magnification and still be able to resolve the details. For this, the 90mm F10 is better than my 102mm F5 and I expect that a 120mm F5 will also suffer at high magnifications due to chromatic aberrations.

For wide field observations, the 102 F5 will do just fine, no need for a larger aperture.

I'm interested in planets, globular clusters, brighter galaxies and nebulas. Medium to higher magnifications.

Thanks!

[David Smith]

CA in my Evostar 120 is pretty well controlled. My primary interest is planets which are generally brighter and therefore more likely to show CA. It is there, and Venus for instance can be pretty ugly without filters but for Jupiter and Saturn it works pretty well. I would imagine for DSO's it would be ok as the target tends to be less bright and therefore produce less CA. Mine is mounted on a CG-4 which is just about workable but I certainly wouldn't want to try imaging anything faint with it.

 

[Peter Drew]

2 hours ago, moise212 said:

I'd like to get a little more personal with them so I'd like to increase the magnification and still be able to resolve the details. For this, the 90mm F10 is better than my 102mm F5 and I expect that a 120mm F5 will also suffer at high magnifications due to chromatic aberrations.

For wide field observations, the 102 F5 will do just fine, no need for a larger aperture.

I'm interested in planets, globular clusters, brighter galaxies and nebulas. Medium to higher magnifications.

Thanks!

Didn't know  you already had a 102mm F5, a 120mm F5 probably wouldn't be enough of an upgrade to be worthwhile, specially if higher magnifications are considered. Very difficult to find an affordable telescope that can do both, your 130mm PDS comes closest. 

[Louis D]

Consider rebuilding your dob into a lightweight suitcase style better suited for travel.

[alexbb]

Thanks all!

I don't intend to do any imaging with this scope. I want it to be as plug&play as possible. The suitcasedob sounds good, but still I have to be careful with it, it takes time to assembly it, not to mention how much it would take me to build it in my apartment. And being careful with the box with mirrors and spending time to put it together is more demanding than carrying my C6 and collimating it if needed. In fact, I'm thinking to sell my dob and the C6 and get a C8 instead.. But that's another topic. And all of these need some dew prevention measures.

The 130 PDS could work, but putting it on an EQ mount makes the observations difficult. I have to rotate it inside the rings, which I don't like and, worse, I have to put it back perfectly in the previous position so when I image with it again, the spikes are in the same position.

Therefore, a cat or a frac would suit best my needs I think. I had a 5" mak and the cooldown time was significant and the C6 clearly outperforms it in brightness, having XLT coatings. It was smaller than the C6 though.

If the CA is not that bad, I think I'll get one maybe in August when are my and my brother's birthdays. I'll keep the 120 and I'll give him the 90 frac on the EQ3-2.

I still have time to decide otherwise.

Clear skies,

Alex